This thread i make so people can share their building/modding knowledge for heads and cabs.

So i'm thinking of building and amp / buying a cheapo (used jcm 800 or an ampeg or something) and modding the shit out of it.
I'm interested in cutting out shitty fuzz, adding a fuckload of tight distortion, and pretty much learning what i have to do to shape the tone of an amp and turn it into a monster. Anybody know how do to this?

So far, all i know is how to change plate resistor values, and that the higher the resistor = the higher the gain... but thats it... Is there anything else i can do? Jopop, i'm lookin at you.

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You need to take a analog electronics class if you want to mod a tube amp. They are ancient technology by modern standards but mods still require in depth knowledge to get the most out of the work. There are a lots of things to know about amp function and I'm not just talking about music amps but the basics are the same. Placing a higher value resistor in a circuit will not do shit unless you know where to put it. Put it in the wrong spot and you will release the magic smoke from your amp and it will work no more.

I'm not about to start teaching complex electronic fundamentals on a forum. I don't have the time and it is wasteful. You would learn faster by working for free at your local TV/stereo electronics repair store and taking a class or two.

I will post simple mods for amp and cabs but go to school to learn to most.

Just remember to be damn careful.

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Like Soulinsane said, tube amps are very simple devices, solder points are very large, components are few, the design is simple, and so on

The JCM 800 is a great amp to start modding.

Here's some pointers:
More gain & bass: Add a cathode bypass capacitor (or increase the one already present).
More gain (clipping really) & compression: Increase the plate load resistor.
Just more gain and less buzzy tone: Modify & fine-tune the voltage dividers between gain stages (will explain more throughly tomorrow, it's late here).

Tone shifting: Modify coupling capacitors (google it) to a larger value for a darker sound, smaller for brighter. Change the values in the tone stack for a drastic change in tone, higher value means lower frequency (for example, change the bass cap. from 22n to 220n for a massive increase in bass and low mids, used by ENGL for instance). http://www.duncanamps.com/tsc/index.html is a great tool for tone stacks.
Google "marshall tone stack" to find out more.

More clarity: Muddiness is often caused by "too many" components, i.e. the designers have added tons of capacitance to "safe" the design so it won't crap out no matter how crappy it gets built and how much off standards it is (too much high freq. cut between stages to tame over-excessive buzziness is an example, it muds things up, they should rather have less gain and then less cut), they add huge amounts of gain in each stage but then cut tons off before next stage to keep it from overloading (adding small amounts of gain in each stage and fine-tuning is FAR superior to going all-out in each stage and then just chopping off a lot to not get "bad" distortion in the next tube (blocking distortion)), etc.

Tightness:
A nice and solid power supply gets you a long way - check that you have a diode rectifier and plenty of filtering, adding some more caps in parallel over the existing filter caps can help. There's more on this but i will get back to it.

Google all the things you don't understand, like "voltage divider", "plate load resistor", "cathode bypass resistor" etc. Check out the preamp section of amps you like, and observe the small differences (they are mostly VERY similar).

Here's a VERY nice article for the JCM 800: http://tone-lizard.com/Ultimate_JCM800.htm

Also, read the info material on www.aikenamps.com and check out www.ax84.com , esp. http://195.178.227.103/ax84/media/ax84_m35.pdf - nice theory on tube amps.

Also maybe some general theory, like Ohm's law, Kirchoff's laws etc may be helpful..

Bedtime, sorry.

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ahhh beauty

I will research all of that, and i know the basic physics laws, they were the only thing i was mildly interested in in physics class. I will do my reading.

Oh and Soul, i'll be lookin for a class to take so i can get familiar enough with this stuff to build my own.

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Nice links You are a very brave man to want to explain all this on a forum. I figured it was going to take me hours. I think the hardest part for me was going to be explaining how to analyze and calculate circuits in order to derive the target component values. There is just so much to know.

Good luck!

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This mod is for any speaker cabinet. This mod will help add clarity and frequency response to your tone; mostly in the low mid to bass range. For simplicity, I will explain these instructions as if I were performing this mod on a closed-back 4x12 speaker cab, but is only the example. This mod can be performed universally on absolutely any type of speaker cab.

Important note: These instructions will only cover what the cab is wired with and not change its wiring schematic (or change how it is wired). Basically, when finished, you cab should be wired the same but with better wire material.

First step is to assess if your speaker cab needs this upgrade. The focus here is to determine what wire gauge diameter ( AWG ) is currently being used in the cab. Most cabs use a small diameter wire because it is very economic when manufacturing a large number of cabs. Better wire adds a huge cost when you have to wire hundreds if not thousands of cabs. The AWG of a wire can be found written somewhere on the length of the wire or you could just measure the diameter of the conductor to get a close guess. Small wire diameter will result in poor signal transfer from the amp to the speakers for many reasons to detailed to post about here. Anything 15 AWG or higher AWG will need to be replaced.

FYI: The bigger the AWG # the smaller the wire diameter. The smaller the AWG # the bigger the wire diameter. Keep in mind stranded core wire will seem to measure larger in diameter than solid core wire due to cross reference parallax error. Higher frequency signals travel better near the surface of a conductor and stranded core wire was invented to accommodate those frequencies. It was designed as one wire with a lot of surface area carry high frequency traffic far better than solid core wire.

Materials needed:
Soldering iron
Electronics solder ( not plumbing solder )
Female spade push-on connectors ( that will accept you new wire AWG )
Pliers to crimp the spade connectors
Wire strippers ( a knife will work if your careful )
AND....new wire.

The new wire will need to be STRANDED COPPER WIRE with an insulated wrapping to help keep it oxygen free. Stranded copper wire is ideal to carry high frequency signals without problems. Do not buy solid copper wire or any type of aluminum wire. Stranded copper wire is the best you can buy. Ignore "speaker wire" as it really isn't designed for use inside a speaker cab and will have a measured capacitance even in short lengths. It is better to keep single insulated wires ( stranded core ) in a cab separated about an inch apart to prevent capacitance from building up and ruining the signal. There room inside a cab so use it.

The new wire also needs to be at least 14 AWG. I would not use anything large than 12 AWG unless you really are good with soldering. I used 10 AWG in my cab as overkill but it also very hard to work with. I purchased 10 feet of 10 AWG stranded copper wire at a Home Depot hardware store for $0.40/foot.

12-14 AWG stranded core copper wire is perfect the prefect mod.

The Work:
Draw out how your cab is wired on paper before you disconnect any of the old wire just in case you get confused later. Be very detailed. I will not cover wire schematics in this mod. The new wires should be connected to the same points as you old wires.

Measure out each length of wire you will need. The shorter the better but leave enough length to be able to move it away from other wires or things the wire might vibrate on.

Strip the insulation off the wire ends and twist the strands hand tight. With the solder iron tin all the twisted wire ends.

Next, depending on the cab, wire ends will now need to be soldered to the cabs input jack(s) terminals, but first you will need to desolder ( remove ) the old wires from the jack(s). This can be done by simply holding the solder iron to the where the old wires are soldered to the jack and lightly pulling on the wire at the same time. The solder will melt and the wire will pull free. Here's a nice soldering guide, but there are hundreds online to read.

Once the needed wires are soldered to the jack, put the female push-on spade connectors on the other tinned wire ends and crimp them on using the pliers.

Remove one of the old wires from the cab by pulling and wiggling the connector off. Replace it with the new wire by pushing and wiggling the spade connector onto the correct male speaker terminal. It should fit tight. Repeat this process one wire at a time until all the old wires are replaced by the new wires.

Advance Tip: If you are really good at soldering then add tinning on the female spade connectors and once pushed on the male speaker terminals, using the solder iron, apply just enough heat to remelt the tinning on the female shade connector so that both the male and female terminals fuses together with solder. This will provide a rock solid connection but requires a lot of skill to know how and when to remove the solder iron. What makes this hard is the speaker magnet. The magnet will pull very hard at the solder iron and could take it out of your hand and put the hot end through the speaker cone. I seen it happen once so be very careful.

Once everything is connected, make sure none of the wires length contacts anything or comes within a inch of the other wires. This will prevent the wires from rattling or building a capacitance.

The wires should look like this when finished.

And this, but ignore trying the foam mod until I post it.

Once everything is back together you should notice an improvement in tone. Mostly in the low range frequencies. The improvement comes from the lowered resistance of the bigger gauged wire, better frequency attenuation of the stranded copper core, and removed capacitance due to careful wire placement. However little difference this new wire compared to the old wire makes on short lengths measured by a multimeter, this mod does make a real difference when measured on a O-scope. Musical tone is noticeable to the point that even a untrained ear will hear it.

Summary:
This is an easy and cheap mod. The key phase is, "Bigger gauge, stranded copper wire is better". No body should have much problem with this mod but post questions if you have them.

Good luck.

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Also, after doing Soulinsane's mod, remember that your cable from your amp to your cab is now by far your weakest link - buy a pair of jack plugs and use the biggest wire you can shove into the plugs and solder yourself. I use 10AWG inside my cab and i think i have 12 or 13 AWG speaker wire inside a modified jack plug (cut it open and bent it out).

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Absoluely correct, but you spoiled my surprise. The speaker cable is the weakest link after my mod, but it can be nulled with high quality cable and good connectors. I make my own speaker cable with MOGAMI 3103 speaker wire ( 12 AWG dual speaker wire design for outside a speaker cab ) and G&H Megafoot .500 phone connectors to mate my amp and cab.

Edit:I guess I now have to explain how to build your own badass cables next.

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cant you just buy a kit? The guitar store local to me honestly has a HUGE rack of different gauge wires with a giant sorted box full of different plug types... or is there some speshul secret you know

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Where do you get that cable + the plugs? I am about to order some Mogami signal cable, so maybe I'll get a roll of speaker cable too (my current one is a little lacking, AND I'll be upgrading my car stereo soon)..

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Now that means we all need to upgrade the wire from the output transformer to the speaker outputs

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You're getting the right ideal You could have the best gear in the world but you need high quality materials connecting it all to get the most out of that gear. I can not emphasize the importance of good cable, wiring, and solder joints enough. Any musician worth a damn will tell you the same thing. All it takes is one solder joint, wire, or cable of poor quality to ruin you tone. Why make your own cable? Because its cost efficient, construction quality is better, and you get the lengths you need.

Continuing with this theme, I will explain my top secret cable making skills. I've spent hundreds hours of researching cable stats and materials, comparing everything. This post will reflect my final research results, choices in materials, and supply links.

Instrument cable:
Mogami w2524 guitar cable has the best stats I've ever seen compared to other cable manufactures that publish their cable stats. Basically, if you can't find stats on a cable you don't want it. The difference you hear between this cable and most other cables is like night and day. I consider this to be the best cable in the world, even compared to instrument cable that cost hundreds of dollars/ft. It is about as neutral, transparent, and quiet as a cable can get.

This is the cheapest place I have found it at $0.52/ft. Average price is $0.75/ft, but I have seen it as low as $0.37/ft in the past. If you can find it any cheaper than let me know.

Neutrik phone plugs are my favorite plugs to use, especially the series-C plugs. They are absolutely solid badass plugs for both instrument and patch connections. They do cost a bit, but are top of the range quality plugs and I've never had one fail. They range from about $2.00 up to $5.00 depending on the plug type and can be purchased just about anywhere. Here is an awesome buy! I use the Neutrik NP2C-BAG, Neutrik NP2RC-BAG, and Neutrik NP2RCS plugs. It's almost like the Neutrik series-C plugs were designed for use with Mogami w2524 cable. They are a perfect fit for each other. I don't use the gold plated plugs because there is no point unless the jacks they are plugged into are gold plated to and, most of all, I've never found any evidence that plating makes a real difference, so why pay more?

FYI: Use only the mono type 1/4" phone plugs with instrument cable or you will have big problems.

Now that you have everything, all you have to do is solder the plugs onto the desired cable length. Seems easy right? There are some important things you need to know first about stripping the Mogami cable. There is a layer of black PVC that needs to be stripped from the end of the clear insulation. Don't question it it. Just do it or the cable will not perform as it should. A fully prepped cable will have two hand twisted strands and will be tinned with a solder iron. It should look kinda like this once stripped, twisted, and tinned. Ready to have the plug soldered on . The strands in the middle of the cable should be soldered to the plugs tip terminal and the shielding strands should be soldered to the plug sleeve terminal. It should look kinda like this but not broken. Put the casing on the plug. Now test the constructed cables resistance with a multimeter to make sure there are no shorts or opens where there shouldn't be. Done.

Tips:
Make sure you slide the plug casing on to the cable first before you solder the plug and cable together or else you will have to desolder everything to get the casing on the plug.

Don't make cables any longer than 30' or the signal it will carry will start to diminish.

Practice soldering for about an hour or until you know you are ready to tackle this project. To much heat applied to the cable when soldering will melt the insulation and ruin the properties in that part of the cable if not ruin the plug in the worst case. To much or over heated solder joints will also ruin tone by acting like a resistor. Bigger the blob isn't better the job. Soldering is easy but it takes some pratice.

Always remember to tin the twisted strands of the cable and the plug terminals before you solder. It will help make the prefect solder joint. Use just enough heat and solder and the joint will be prefect every time.

Summary: I hope this saves someone from paying $50 on a pre-made 20' Mogami guitar cable with Neutrik plugs, because now you know how to make that same cable for $15. Making the prefect cable only requires decent soldering skills, good cable and good plugs. That's it. If you got any questions then ask.

Good luck

Edit: I'll post my links for speaker cable materials later, but their construction is basically the same. The only difference is that speaker cable is balanced while instrument cable is unbalanced.

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Now for the speaker cable. It is basically the same process as instrument cable construction but with balanced cable.

Mogami w3103 2/12 AWG conductor speaker cable is what I use. Avoid 4 conductor in quad configuration cable; its good for triamping only and not ideal for short runs between amp heads and cabs. Do I use w3103 because I have a hard-on for Mogami cables? Not at all. Again, I put hundreds of hours comparing stats and performance test results into dozens of different speaker cables before coming to my final choice. It surprised me that Mogami was again the superior choice. This stuff cost a lot but the good news is you shouldn't need but a few feet of the stuff. Best price I've ever seen for this cable. This is were I got mine. The bad news is the shit is thick ( just under 1/2" in diameter ) and there are not many phone plugs that can accept the stuff.

G&H MEGAFOOT plugs are the only things I know of that will accept this cable snug. They all cost about the same everywhere. They are actually very nice high quality plugs.

And thats it. Solder it all together and remember to tin the cable stands and plug terminals first. I like to add some shrink wrap around the plug and cable for add protection and stability.

Summary: This cable makes a huge difference in tone and will not cost you much to make compared to buying it pre-made. Any question?

Good luck

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Ok, I can see people are viewing the thread but what disturbs me is that no one is asking questions all of a sudden. I need to know if anyone is getting shit out of this thread or I will stop wasting my time. I have a lot of knowledge to share but damn wasting my time typing it out.

I've opened myself up here so ask away. This thread is about easy mods. Predators are waiting to charge you at least 3x more than what I'm given for free. I've hidden secrets for years, thinking it would give me a musical edge, but the only real edge is hard work. Now is the chance for me to share more. No one will be able to take your cash on over priced shit if you read my post, but give me some input or I will share no more.

If you read me then post or I'm going to stop posting my brain dead upgrades I can spend my time in better ways.

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Oh I'll have questions for you soon enough, I'm still just trying to digest all that info.

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What is this about? I'm sure I know tricks you don't so don't get ahead of yourself young grasshopper.

I believe you have questions now. Ask away...

Take the pebble from my hand

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Haha never mind I read the speaker cable mod thing again twice and now I got the grasp on it. Really informative, thanks, I may attempt this sometime after I learn to solder. I do feel like my Framus 2x12 cab could use a little more low end... I'll also be doing the foam mod to it at some point too.

I use Mogami instrument cables and you are right, miiiiles ahead of any other cable brand I've tried. I have some monster cable and a cordial(not bad, has neutriks), but the mogami blows it the fuck away. Unfortunately I have Planet Waves speaker cable(oxygen free), but I wanna upgrade everything including patch cables to some mogami when I get the chance.

Hey man, check out my other thread about what soldering kit I should pick up please.

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Before you try that foam mod read my next mod post first. Please! It will not be much but there are a few things I need to explain before the foam mod. I will actually include the details in the foam mod lesson.

I seen your thread about solder irons too. Both of your choices will serve you well even though there are other crazy expensive irons on the market that do many other functions. Expensive solder irons do have a place in the world, but for most music project mods the irons you posted in your thread are beyond perfect. 15-30W pencil irons are the max anyone should use for basic electronic soldering. Practice is all that is needed, but reading a few guides will definitely help too. Tinning is about the most important thing you can ever do when soldering electronics. This isn't rocket science after all

Edit: Btw, oxygen free cable is a sales hype in most cases. Mogami uses the words "oxygen free" to, but any wire that is insulated correctly shouldn't oxidize even in a hundred years.

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I ordered lots of crap from redco.


Had to keep it under 30 to skip customs. Redco 12AWG speaker cable from amp to cab (i can't really tell a difference between brands that are considered "decent"), 100 feet of Redco Install Cable (again, can't really hear much difference on high-voltage low-impedance signals, i.e. anything after the preamp) in fun colors, and two con + shield high-impedance ready cable (almost just the same as Soulinsane's, just balanced which means i can run semi-balanced and get NO NOISE, and no real thick plastic insulation). Not as sturdy as 2524, but in a studio, it doesn't matter. Better specs too (on paper). This has been one of the top workhorses in professional recording studios for guitars, high-Z mics and the like for many years, and it sounds pretty damn amazing. Low capacitance / foot and hardly any resistance makes this a very clear and bright (good bright, not "thin"-bright) cable. The shield is a fucking madman, with a served shield of about 95/0.12A there's just no HF noise getting into this bastard. I can't fathom why they sell this so cheap. It's not the cable to bring on the road, but it's unbeatable in the studio and at home if you can manage not to dance on top of it.

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shhh, dont say that, they'll find out and raise the prices



Man, all of this info is SOOOOO key, and Soul, its kinda hard to ask questions when you've already answered them all. All of this is VERY appreciated.

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Soul: Your posts are really informative, keep them up I always forget to tin the ends of my wires when soldering- i should know better by now, i've been soldering for years! It seems to be really difficult to find Mogami cable over here in the UK... really irritating, as i'd like to wire my whole rig (rack included) up with 'custom' cut cable.

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Hey Soulinsane that was some GREAT info!!! I am considering making these Mogami cables myself. Right now I'm using George L's but I hate them because they die randomly due to the "solderless" connection, which is quite scary on a gig as you can imagine! My other big problem with them is how easily they tangle. Almost unnaceptable. How are these Mogami cables for onstage use? I run around a lot and every cable I have ever used tangles up badly. I need something that won't do that unless I use it as a lasso haha! Considering how cheap it is to build these and the fact that my soldering skills are decent (I have built effects pedals and re-wired many guitars) I feel these are the best deal possible, for a great sounding cable. They are cheaper than the George L's for sure.

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Mogami is a tough cable so it would have no problem being used onstage, but don't expect it to last for ever. Walking on, pulling on, and bending the cable will reduce its life over time. W2524 cable has a flex life of 15,000 bends, which is really good, but no cable last forever.

I'm not sure if it tangles less than other cables, but give it a shot. I always find myself turning one way when I play guitar and that makes the cable want to coil up.

Edit: Solderless plugs fucking suck. You are right about them failing all the time, plus they have poor connection with the cable conductors. I can't blame Goerge L for trying though because it would be hard to sell a cable kit with a solder iron.

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+1 on the solderless. It's horrible. I myself solder everything in audio, no god damn cable connectors on anything. If i have to use a screw-on terminal i tin the wire, tin the terminal, screw together and solder them together. This is a decent upgrade to your George L's, very recommended. Also, the transfer resistance on a screw-on terminal is pretty damn high compared to soldering it on - we're talking 0,2 ohms versus 0,0002 ohms. Stuff like that actually makes a difference with a complex low-voltage signal.


People in "pro" car audio solder the speaker cable directly onto the speaker terminals instead of using the more common cable connectors.. It has to be for a reason

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I agree completely, but you got to be damn careful when soldering near a speaker. The magnet will attract the solder iron like crazy and if it pulls it out of your hand... the hot iron tip could end up in the speaker cone.

I seen someone have that happen once. The speaker was completely ruined.

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This is a super easy mod to be done to just about any speaker cab to tighten low end and low mid range response. It will eliminate a cabs tendency to sound boomy by lowering the noise peak resonance frequencies while at the same time extending the low end frequency a few Hz.

But first, while you have the cab open, it is a good time to inspect your speaker wiring, speaker mounting, cab structure strength, and the cabs seal integrity.

Speaker wire inspection: If you have not read the speaker wire mod I posted earlier in this thread then now would be a good time to do so. Upgrading your wiring is a higher priority than added foam.

Speaker mount inspection: Make sure the speaker(s) bolt all the way through the baffle, even if front mounted, with a T-nuts ( or clamps or normal nuts) and bolt screws. Most cabs use "nut and bolt" mounting but a few cabs use just wood screws. This will not provide the speaker seal(s) with proper tension and the speaker(s) will eventually vibrate badly and fall off the baffle. Replace "screwed in" speaker mounting with "nut and bolt" type speaker mounting.

If you have "nut and bolt" mounting then give each nut screw an even tension twist with a screw driver, but not to much or you will strip the threads. Just make sure nothing is loose and every "nut and bolt" have an even amount of tension. Its critical to insure the speaker seals effectively against the baffle board.

Cab structure inspection: Most cabs use glue to hold the joints together in conjunction with internal bracing 1x1' batons stapled or glue in to better seal the cab. I guess its a cheap and good way to make cabs, but it can be strengthened further. It's not necessary in most cases but if you want to strengthen the cab structure then just add wood screws through the 1x1' baton bracing into the cab shell. I suggest predrilling the screws unless you want the bracing batons to split. Once done you should be able to hide behind your cab during a nuclear attack and feel safe.

Cab seal integrity inspection: Now this is critical, even if you have a ported or open back cab; and most important for closed back cabs as no air should ever escape. A cab needs to be sealed air tight to prevent air from escaping where is shouldn't for many reasons. I would love to explain everything but it took me endless hours of researching detailed material to see why it is important. It would take me pages to explain, so I would rather get right to the simple methods of how to properly seal a cab.

Get some caulking and go over ever bracing baton corner within the cab. Do not use it around the speaker(s)! A speaker has its own seal so no need for added sealing.

Around the handles and removable back board use a weatherstrip tape to seal the cab.

FYI: I took shit a step further and built an air tight isolation box around my jack port. I did this because I could see light around the jack so I knew it wasn't air tight. I used wood, glue, wood screws, and caulking to completely seal the jack box. Now my cab is completely sealed.

Inspection and preparation is now done, time to add foam.

There are many expensive sound damping foams. Inside a cab there is no need for expensive foam unless you have money to burn for bragging rights. I bought a single twin bed egg crate foam mattress at Walmart for $10. It's not pretty but no one will see it inside the cab. It is made of the same stuff and works the same as the expensive audio foam. Don't stuff the cab with blue jeans or popcorn foam... please. Its to dense and not porous enough to brake up standing sound waves.

You don't want foam in contact with the speakers, so don't add foam to the speaker baffle. Parallel solid surfaces benefit the most from having foam attached. A cab doesn't have to be packed with foam to achieve the desired effect. Use 3m glue spray on the foam surface to be attached and then stick it to the inside of the cab. Don't spray the glue inside the cab! Other glue will work too but allow a few days to cure. I use wood glue on my foam and it is still holding strong.

How does it work and what about space reduction inside the cab? The needed foam for this mod should be porous and if compressed into a solid block of foam should only consume several cubic inches. Its reduction on cab airspace is effectively null. Depending on how dense the foam is ( profession audio foam used on studio walls is very dense ) it could take more of less relative space inside the cab. Since most egg crate foam is so porous and air creates most of its volume, a cabs inside airspace with foam remains about the same. The speakers still have far more than ample airspace to work safely and effectively for their natural lives. What is important about foam is that air vibrated by the speaker(s) becomes dampened once contacted by the foam. The foam absorbs the energy/vibrations and doesn't bounce it back like solid wood surfaces. These bounced back vibrations are called standing waves ( like an echo ) and will influence speaker vibration in a unwanted way.

Foam will destroy standing waves, kill boomy tone, and expand lower end frequency response. Bass cabs and closed back guitar cabs see the best results from this mod.

If there are any questions then please post them.

The result.
From a different angle.

Good luck

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I love Soulinsane.

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^
this might be my fave thread

Great mod. Mods like those turn a cab from budget shit to something boutique sounding. The difference between a leaking cab and a properly sealed one is insane.

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So I finally did the foam mod, whoa!! Cab got really punchy in the low end, didnt think I would notice that much of a difference, but I was wrong! Soulinsane, im pretty sure I got the exact same foam as you, $11.99 at Target. Used Krylon spray adhesive and a hefty staple gun to attach it on the back, bottom, and sides. Awesome mod!

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Awesome I'm glad to know the mod turned out good for you. I personally will never own another cab without foam.

I'm trying to come up with a new easy mod but I can't think of anything safe. I don't want people to try dangerous DIY mods just because I said go for it! The worse that can happen with the foam mod is you glue your fingers together.

Any one got any mods, ideals, or questions?

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Hey, thank you for posting it! Although im thinking about removing small sections of the foam in certain places because resonance inside the cab can still be a good thing. Do you have any other types of mods, maybe some for amps? Im not concerned about danger, have worked with amps before.

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I have lots of tone mods and the like available to amps. Thing is, an amplifier is seriously dangerous business - you don't want to poke around in one unless you know what you are doing.

This is not a mod - this is required reading before you unscrew the first chassis screw.

AMP SECURITY 101 - THE 10 RULES OF AMP SAFETY

Rule 1: There are no exceptions to any rules described in this document.

By no exceptions, I mean no exceptions. Even in the case of "oh damnit i forgot to solder on that little point, It'll just be a brief second" the rules apply. No matter what, you need to obey all the rules described in this document.

Rule two: Think of the power switch as faulty.

The power switch is not a good enough barrier between you and the AC mains, unplug the cord going into the wall or into the amp.

Rule three: Unplugging your amplifier from the wall does not mean it cannot kill you.

An amplifier's power supply contains fairly large capacitors with pretty high voltage and max current storage capabilities. You need to properly discharge these before you can start working inside your amp.

Rule four - Put one hand in your pocket when working on an amp that might carry high voltages.

If you should get burned on your one hand the worst thing that might happen are minor burns. However, if the current flows from one hand, through your heart, and out your other hand, there's a possibility you might die or you blood might go acidic. The chassis of your amp is actually connected to one end of the power supply (reference, usually 0 volts) or ground (or in most cases both). Having one hand touching the chassis while the other reaches in to measure some voltage while the amp is "live" or discharging capacitors with one hand on the chassis and the other shorting the caps can be lethal.

Rule five - Don't work on an amp together with other people that might distract you.

People who ask "What're you doing? What does that do?" might break your concentration just enough to slip your tools somewhere they shouldn't be, causing damage to you or your amplifier. Don't talk on the phone either. Stay focused.

Rule six - Things might blow up, protect your eyes and face.

Capacitors, diodes, resistors et cetera might blow up if you use the wrong value component or wire it wrong. This is just like setting off a small hand grenade, it might make you blind. Close the chassis or wear glasses that cover your eye when you power up your amp. Don't sit with your face unprotected over it.

Rule seven - Solder might drip.

Wear pants long enough to cover your socks, and wear socks. And, at least wear a t-shirt. Solder dripping on your knee or feet not only hurts, but leaves permanent marks as well.

Rule eight - Don't wear metallic objects.

Off with jewelry, rings and watches and other metal stuff on your hand. Also, don't wear a necklace that might fall down into the amp shorting stuff. Piercings in your face, ears, or on your body other than your hands is okay.

Rule nine - Use your common sense, don't do anything stupid.

This rule explains itself. Don't put your coke bottle on top of your chassis while working in there, stuff like that.

Rule ten - If in doubt, ask.

Don't assume something will be okay, maybe it won't. No question is stupid when it comes to safety.

Well that should be a pretty damn comprehensive safety rules list.

How to decharge capacitors

1. Make sure you followed the safety list from top to bottom.

2. Open up the amp. Wait 10 minutes or so before doing anything else.

3. Locate the power supply capacitors. They are cylindric in shape, and have two or more ("multi-section" capacitor) leads going out from the "shell". They're generally one color with a black, grey or white stripe or arrow pointing towards one of the leads. Looks like this:
http://www.germes-online.com/direct...c_Capacitor.jpg
or
http://www.germes-online.com/direct...c_Capacitor.jpg

As you can see there might be one lead in each end or several coming out from one end.

4. Drain the caps. There are several ways to do this. You could either short the capacitor, by deinsulating a wire a little bit in each end, and connecting one lead on the capacitor to the other lead (REMEMBER RULE FOUR). There'll be a small pop and a flash, but it's nothing to worry about. Leave it there for 10 seconds or so, then go on to the next one.

The other way (which i prefer) is connecting a switch and a 50K resistor between a preamp tube's plate and ground. Solder a wire onto pin 1 on a preamp tube socket.

Here's the pinout for 12A*7, ECC 8* and so on: http://en.wikipedia.org/wiki/Image:EIA-9A.png

Solder the other end of the wire to one leg of a 50K 5 watt resistor. Solder the other resistor leg to one lug of a simple SPST switch. Remember rule four. These are like $0.1. Now solder a wire to the other lug on the SPST switch. Solder the other end of that wire to a ground point, or solder it / screw it down to the chassis (but not a painted area, paint is not a good conductor). And remember rule four. Now anytime you'll be working on your amp, just turn the switch on, wait 5 minutes, measure the voltage over the 50K resistor, and if it's under 10 volts or so you're good to go. If not, wait a little while longer.

Remember to turn the switch off again before testing out any modifications. Leaving it on won't harm anything, but it'll decrease the plate voltage on one triode (creating a voltage divider), meaning shitloads of distortion and (in most cases) bad sound. Leave the switch engaged while working inside the amp.

Make sure you get a five-watt resistor, they're quite a bit sturdier and won't break as easily. A two-watt or even less should also be fine in all cases but the 5-watt is best anyway, and is not that much more.

Now start modding

List the mods you want explained, i.e. more/less gain, more/less bass, more/less treble, less buzzy tone, darker / brighter tone, more low mids, more high mids, tighter bass, more clarity or similar, if i know how to do it I'll try to explain.

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Wow, this could get fun...

My other guitarists Laney GH100L is a little harsh in the upper ranges, my Laney VH100R does not have this problem which is strange because they should have the same drive channel, but the GH100L is an older version and might be built different. Basically, smoothing out the high end would be good.

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According to the schematics, they differ on very few points - the voltage in the VH100R is quite a bit higher, and one capacitor in what looks like a low pass filter is actually smaller, which should result in a less smooth sound (the exact opposite of what you're saying). I may be wrong though, I'm not too good at spotting different functions in a schematic. The things that obviously differ are the transformers, which has an impact on the overall sound (esp. the output transformer). Your tubes and guitar make a difference too.. Your amp should also feel a bit tighter at high bass settings and also be a bit less muddy and cleaner at high-gain, but the differences are quite small.

Anyway, on to the mod -

http://www.schematicheaven.com/newamps/laney_gh100l.pdf
Page 3.
Right after V2a you see C9, which is 22 nanofarads. For fun, try swapping it out with a 470 picofarad one, i don't really see how it will help, but it will make his drive channel exactly the same as yours (this exact circuit puzzles me, it seems like a lowpass filter and a voltage divider, but I'm probably wrong).

Now, if that doesn't work, move on to right past V3a, where the tone stack is. Replace C17 with a 680p silver mica, and test the amp. If you still feel it's too harsh sounding, try replacing C22 with a 33nF Orange Drop, this will make the amp a tad bit warmer and darker. If it's still not enough try a 47nF, it will give lots of low mids and not so much high mids, very warm sound.

http://www.tube-town.net/ttstore/in...15P-Series.html
http://www.tube-town.net/ttstore/in...ilver-Mica.html

Doesn't have to be these brands, but they have a good name.. not that it should matter. You could just as well try radio shack, make sure you get mica and polypropylene caps (mica for the really small ones, polypropylene for the others). Don't get polyester film, they're for vintage freaks who like noise and distorting capacitors (which is not good for high gain).

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Q: My amp is a little too buzzy / harsh but otherwise i think it rocks, what do i do?!?

A: Well, usually this is caused by higher harmonics which may sound harsh or buzzy. There are many ways to get rid of them, but this is the easiest and my fav. by far. What you need is one or more 1nF capacitors. Get polypropylene film type if you can, they're the best type for tube amps.

Wire one 1nF capacitor in parallel over the plate resistor of a preamp tube. Generally speaking, the second-last gain stage is the most effective point, followed by the last one. To find the second-last stage, look at the schematic for your amp and look at the plate load resistors. They will usually be 100k, but one or two of them will be larger, like 150k, 220k or even 330k. The gain stage with the large plate resistors creates the most gain and high harmonics, so this is the best place to put the capacitor (for starters). If there are two or more gain stages with large plate resistors try modding the one that comes last in the signal chain first.

Solder one end of the 1nF cap to one end of the plate load resistor, and the other end of the cap to the other end of the plate load resistor. Thats it. If you still feel you need more, try soldering another 1nF cap on top of the 1nF cap you already put in, and if that smoothed it out too much take the cap out again and try adding a 1nF cap over the plate resistor of the gain stage that comes next in the signal chain.

I uploaded a engl blackmore schematic showing where the extra capacitor goes, it's drawn in red so it's easy to make out, so you can see which resistor is the plate load resistor and which gain stage you usually want to be modding (the one with the biggest plate load resistor).



This mod will smooth the amp out quite a lot but not make it that much darker, if you want a darker sound i have another easy mod..

Attached Images

englmod.gif (8.8 KB, 135 views)

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Damn...this thread kicks ass.


I did Souls Cab mod ages ago, but I'm not quite sure where the pics are now.

It definitely tightened it up quite a bit....and it's no cheap cab to begin with.

It is a new Crate Blue Voodoo cab, and the benefit was great!

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--- Tone stack mods ---

Q: I want more "roar" instead of "buzz"/sizzle/chainsaw! And i want more low end!! Please

A: Well, if you want a more "roaring" sound instead of a chainsaw-like buzz, you need some way to decrease the amount of high mids in your amp. Luckily enough this is easy on most amp that have a traditional tone stack.

There's an easy way to add in low end too. It won't make that much of a difference if you tune to E standard, but if you tune to B or use a seven-string it will make all the difference in the world. Be warned that this mod also lets you scoop out your mids a tiny bit more, so if you usually run mids on 4 run it on 4.5 after the mod.

What you need to decrease the value of the treble capacitance in the tone stack and increase the bass capacitance.

The following example is from the 5150, since i did this exact same mod today on my 5150.

The treble capacitor in this tone stack is a little strange, there are actually two of them. There is one that's 470pF, and one 100pF wired in parallel with the 470p. When you parallel wire capacitors the capacitance increases, so total capacitance of the treble caps is 570pF. This is a very large value and it accounts for a lot of the chainsaw-like sound of the 5150, the amounts of high midrange is absolutely insane. What you need to do is decrease the vaue of the capacitor(s). The first thing to try on the 5150 is to just cut the legs of the 100pF and remove the whole thing from the circuit, reducing the capacitance to 470p. This is still pretty high, but might just be enough for some (it was enough for me). The treble caps in the 5150 look nothing like ordinary caps, they look just like resistors. They are blue and located between the treble and the mid control. The 100pF one can be identified by it's color code, it starts with a brown ring. If you can't be bothered, well it's the one closest to the mid control. Just cut it out and see if you like it. If it's not enough, cut the 470p out of the circuit too and try soldering a 330pF or 220pF in it's place. 220pF is as low as i would go, below that you would lose a lot of aggressiveness! Remember to cut the legs off the components as close to the component body as possible so you can solder the new components on the existing legs (so you don't have to screw the main board out! saves a lot of work).

To add low end, look just above the treble pot for a small, yellow capacitor. It's right next to a jumper (a jumper is just a bare wire). Cut the bastard out (the stock caps suck ass by the way), remember to leave the legs of the components there! I would just clip the fucker in half so the legs are longer. Now, solder a capacitor on there. I used 100nF (or 0.1µF), you may experiment with 47nF, 68nF, 100nF, 150nF and 220nF. There is hardly any difference between 100nF and 10000nF so i wouldn't bother with anything higher than 100nF (the tone just gets more scooped after 100nF), and if you find there's too much bass after the mod try a 47nF. This is a huge improvement if you like to play 7 strings or tune lower than D, the low end chugging will kick ass after the mod.

Note: as always, use polypropylene capacitors. For the treble caps you can use silver mica, they're good too. I like Xicon brand polypropylene caps, they're inexpensive and sound great. Other favorites are Orange Drops and Mallory's, but i can't really hear the difference between an Orange Drop and a Xicon, and the Xicon costs 1/3rd of the price.

See the attached image for details

The procedure will be similar for all amps with a similar tonestack.

Attached Images

5150-tone-stack-modded.gif (7.9 KB, 145 views)

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Nice mods, Jopop I love how that cap mod on the gain plate resistor works as a voltage regulator. Simple and easy.

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this is exactly what i've been waiting for

hows the new 5150 sound by the way Jopop?

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Well i have mixed feelings about it

Some days i just love it and some days i want to get rid of it. But i think it's more of a volume issue, it does not really sound good below 2 on that master volume really, and i can't play that loud every day

I played it for an hour today on volume 3 or so and dialed it in pretty good! I loved the tone and when i tried swapping guitars the tone was still really awesome without any tweaking really, it just became a tad different which was cool. I marked my settings with a green marker on the face plate so i won't forget them if someone fucks around with it

There's a very fine line between too little and too much on this amp's EQ and all the controls affect the others in some way or another.. Also the very subtle darkening of the amp worked really well, it removed some of the chansaw-like gain and put more of a lion's roar in it (the difference is subtle but it's there) Right now the balance between a palm mute and a normal fretted note is very nice and they kind of both just jump out of you but in different ways, and the midrange and stuff is really nice and everything just feels like how it should be. Sounds like a really expensive rig.. Like a Framus Cobra or something (at least what I've heard on record of it). The high end might need a tiny tiny bit more tweaking, but i managed to get it less ear-piercing without becoming too dull. I need to fine tweak the balance between the presence and treble controls, i will get there soon!

Shame though, next time I'll probably play it at low volume and think it sucks.. my opinion varies from day to day but the volume i can turn it up to also varies quite a lot from day to day

Maybe it would be good for me to get a power brake or hotplate or something? Those things are expensive though and I'm pretty broke atm :/

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Oh and I'm sorry, but on the "less buzz" mod with the 1nF capacitor i said polyester film type which is very bad to use! Use polypropylene film! The words are so similar i forget the difference some times I edited the post though so it's correct now

As always, i like Xicon polypropylene film capacitors since they're affordable and sound great. For smaller sizes get silver mica caps (for treble capacitors and so on)

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Yeah, the 5150 sucked ass today.

I sold the piece of shit and bought an Engl Powerball and a Z5 footswitch. 1300 bucks.

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Me wants an ENGL..

I want to try a Bogner Uberschall as well. Any experience here?

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Meh the damn deal didn't go through. Seller crapped out on me I already said I'll take it and he said "okay sold" and then next day he says he sold it to some dude who wanted the amp + cab so he rather sold both

I understand the seller but we had an agreement that i bought it really. What an ass.

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Does anyone have any experience with the Celestion G12K-100 speakers?

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This should be a sticky.


Mass important mod info icluded!!!

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That is very, very cool. I want to do this, my cables suck. Fucking one of the best things i've read on here. Will definantly acquire materials for several cables after my HSC, cause this is awesome. I expect to pay more for the materials here in Aus, but so be it.

Thanks a lot.

Problematic; I assume AUS pricing is similar to Norways? If so i've saved hundreds of dollars ordering from Redco.com. I use their 12/2 speaker cable too, it's top notch at a great price. They also have W2524 in stock at a great price.

For my pedalboard I've had great results with the belden foil install cable. Silent, transparent, thin.

Shipping doesn't break the bank either.

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hey, about cables... and fx loops.

As everybody probably knows by now, i have a marshall 6100lm, which has an SS driven FX loop. My problem with it is that when its on, it completely sucks tone, gain, and basically you can DEFINATELY tell when its on(and i only keep it on the parallel setting thinking i wouldn't suck as bad as the series setting). So what can i do to fix this? Thicker cables in the loop? or should i open my beast up and fix some crap.

Currently, the send and recieve trip pots are set to +4, would setting them to 0 fix that? (ranges from -10 to +4)

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-10 is generally what you work with in guitar audio, +4 is for "professional" equipment. Although, your FX loop might just be a piece of shit, but i thought the FX loops on the more expensive marshalls were pretty good..

Read this (I didn't write it, just copy-paste)

Q&A Questions and Answers general sound questions
GENERAL SOUND QUESTIONS
What does '+4dBm' and '-10dBV' mean on equipment? Is it important?



These values apply to the expected input and output levels. The levels of +4dBm and -10dBV are the 'nominal' levels, not the maximum or minimum, but used to differentiate between equipment for 'consumer' applications which generally have lower level, high inpedance inputs and outputs (the -10dBV level) and equipment for 'professional' applications, which have higher level low impedance inputs and outputs (the +4dBm level).

Both are voltage levels, and as you will see from the table below that the +4dBm equipment will produce up to 4x the level of the -10dBV equipment

level in dB level in Volts (RMS)
+4dBm 1.23V
-10dBV 0.316V


If you connect equipment with different nominal levels, then yu may experience distortion, particularly if a high impedance output is connected to a low impedance input, as the output may not be able to deliver the necessary voltage. Generally, low impedance outputs will connect to high impedance inputs, although you will have to be careful with the level output.



---


Now, if you're doing it the wrong way, you might be experiencing

#1 Gain decrease, loss of high end
#2 Gain increase

If you have both on +4 the return buffer will be severely mismatched with the output of your FX.. and you'll lose gain and treble. Plus, you're killing the input on what you have connected to send :P

BTW, some FX processors can switch between -10 and +4 too.. If you can, low impedance is generally better.

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wicked info dude. So i'm just going to be using pedals on this puppy, so -10 it is?

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Basically what Jopop said.

Setting your amps FX level to +4 dB means your amp is expecting your FXs to be functioning at a +4 dB signal level ( rack gear level ). Your pedals are -10dB, so start the knob there first.

Assuming you are using the series loop, adjust the level knob on the amps fx loop until the volume remains the same no matter if the FX loop is on or off. The final level you use depends on your pedal settings as well, so go with what sounds right to your ears. You might need to tweek the output setting on the pedals as well until you find a tone you like. It's a balancing act really.

Having that FX loop level knob is a freaking nice feature btw. Most amps are lucky just to have a level switch.

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soulinsane, you should start a cab enhancement service. i'd send my shit to you and pay for it.

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Cab enhancement is only the beginning of what I can do and by far the safest. Most mods are way to dangerous to post here. I know that no matter how careful I describe each step in an amp mod someone would die testing the waters and fumbling through my instructions for the first time. There are just to many details to account for. High voltage mods are not to be made by beginners without instructor observation. Several hours of safety training is needed before a potential tech ever opens a unit capable of killing; and this is without the unit even plugged in or energized. Under the right conditions, 30 mA is enough to kill a healthy human so safety is #1. If you want to mod guitar amps then college ET classes are a way to help gear your future If your a hardass fast learner then military service will uber boost the bell curve near cyborg learning levels but I do not suggest signing a military contact just to learn how to mod amps.

If shipping cost wouldn't kill the deal I would gladly mod your cab to your desired specs and wants. If you bring it to me I will only charge parts and beer cost... maybe $40-$50 total if you help me drink the beer. I will also be able to show you the finer points of the cab modifications I know about. The total process including glue cure times is about 2 weeks max, but I'm anal about every detail. When done the cab might look the same but it's reborn hard and bullet proof. What isn't seen is what counts the most with cabs.

"Soulinsane engineering technologies on the information dirt road"

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Bump from the grave. I finally built my own amp, that very amp was the one i started this thread about.

here it is without a headshell, or faceplate art. I have it in the headshell right now, just dont have pictures. I'll be painting the faceplate eventually

Its like a Sunn Model T, 2xkt88's, feedback loop defeat switch, and the wrong output transformer hahahha. Still working on the math to figure out what transformer primary impedance i need for a pair of 6550's running at about 480v on the plates, in ultralinear configuration.

http://i49.photobucket.com/albums/f...01/DSC00386.jpg
http://i49.photobucket.com/albums/f...01/DSC00387.jpg
http://i49.photobucket.com/albums/f...01/DSC00400.jpg

I run it with my B.C. Rich Mockingbird Special (white) with a bareknuckle warpig in the bridge position, into my BlueBeard Fuzz, into the high input.

Bright channel volume around 2, normal around 3, bass at 0, middle at 5, treble 3, presence 1, masters wherever.

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We need some audio when it's all said and done! I really wish I had the prowess when it comes to electricity to do something like this. Very impressive

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I wrote an article (see link) for a guitar site of mine that may be of use to you, and also run a Marshall oriented modding site (see my sig). Feel free to fire off any questions and I'll do my best to respond!

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