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2007-01-19, 13:24
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New Blood
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Join Date: Oct 2005
Posts: 22
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Tube Power Question
I have a 6505 and i was woundering if i take two of the power tubes out will it do any harm to my amp in any way?
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2007-01-19, 14:06
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Post-whore
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Join Date: Oct 2004
Location: Land of Dust
Posts: 3,551
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I would not do this. I know it can be done on some amps but I wouldn't dare if I were you unless I was 100% sure it's safe.
Taking 2 powertubes won't make your amp much quieter anyways btw. Just use your master volume. 
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Originally Posted by far_beyond_sane
(Did you know In Flames had a 2005 album called "Come Clarity"? How prophetic. I think they're trying to tell us all their sperm are dead.)
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2007-01-19, 15:14
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Senior Metalhead
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Join Date: Mar 2006
Location: Norway
Posts: 398
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Well take into consideration that the source impedance (from the tubes) will then be twice as high and this is reflected on the OT, so if the OT is set to 8 ohms you need to hook up a 16 ohm cab for the same sound.
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Many people who own a 100-watt/non-master volume Marshall will remove two of the output tubes to achieve a more manageable volume from the amplifier. This isn't such a bad idea (other than the fact that you have to keep tabs on a pair of output tubes that aren't 'aging' at the same rate as the 'in use' pair), but a popular myth is that you must reset the output impedance selector to one-half of what your cabinet is rated for. This is 99% untrue. An 8-ohm load connected to an 8-ohm output tap should achieve full rated power and full bandwidth. A mismatch 'up' or 'down' will reduce the power output and the bandwidth. With a 'good' transformer utilizing high-temperature wire and 'properly' insulated between the coil stacks, no special care is needed to ensure safe limits of current through the tubes or transformer. You will achieve full wattage and the 'original' bandwidth by adjusting the impedance, but the 'alternative' has interesting possibilities. It's all up to your ears. If you aren't 100% comfortable about this procedure, play the amplifier and feel the shell of the output transformer. Did you get a blister? You may want to check Screen Grid voltages and bias currents. As for the output tubes and reliability, you should have learned by now that output transformers were wound for many different primary impedances over the years. Using 6L6's as our example, the primary impedance recommended has been 10k-ohms, 6600-ohms, and 3800-ohms. The tubes, transformers, and speakers all lived long and fruitful lives. A better idea came later when some Marshalls (and Fender's The Twin) featured what is usually called by everyone except the manufacturer a Pentode/Triode switch (which doesn't really switch the output tubes between pentodes and triodes, but that's a long story). 'Triodes' will have a much lower plate-to-plate impedance, and not even the average tube 'guru' was brazen enough to state that the impedance selector must be adjusted whenever the amplifier is run in the 'triode' mode. As a side note, those Marshall amplifiers with 'High' and 'Low' power switching (JCM900) have given service technicians very little trouble, while JCM2000 amplifiers (without High/Low switching) are the source of many output transformer headaches. Draw your own conclusions.
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http://tone-lizard.com/Marshall_Myths.htm |
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2007-01-19, 15:19
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Post-whore
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Join Date: Dec 2004
Location: Toronto, Canada
Posts: 1,816
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dude, dont do it. you dont have a half power switch so your amp will still put power into all 4 sockets, and if theres nothing to carry the current, there will be big problems.
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Originally Posted by Dahmers Fridge
In the US "fanny" is a word used to describe the ass or butt. Here in the UK "fanny" is a lady garden (vagina)
I was very bemused as a youngster watching the Golden Girls when Blanche said she was going to "spank her fanny" I had visions of a geriatric vertical bacon sandwich red and bruised from being disciplined!!!
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2007-01-19, 16:25
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New Blood
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Join Date: Oct 2005
Posts: 22
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note taken. guess ill just go get a THD hotplate
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2007-01-19, 16:35
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Post-whore
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Join Date: Oct 2004
Location: Land of Dust
Posts: 3,551
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Actually get a Weber Mass, they're far cheaper(because they're out of production) and maintain the integrity of your amp's sound a lot better at high attenuation levels because there's a real speaker motor inside, so the poweramp feels like it's interacting with a real speaker not with capacitors like the THD. Check em on ebay, there's one that has 2 ins/outs. Remember you will need speaker cables to hook up the Mass between the speaker and PA out.
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Originally Posted by far_beyond_sane
(Did you know In Flames had a 2005 album called "Come Clarity"? How prophetic. I think they're trying to tell us all their sperm are dead.)
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2007-01-19, 16:45
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Senior Metalhead
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Join Date: Mar 2006
Location: Norway
Posts: 398
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There will be no current, the connections are broken.. ? Now if you shorted it then okay, but really, output tubes are wired in parallel. Not that i recommend it. The bias current will probably go through the roof (taking two tubes out of there should double it in theory) and the tubes burn out in a matter of weeks. Plus, if you do nothing about / fuck up the impedance selection then there's a good chance you output transformer will have a meltdown. 100w output tranformers are not cheap..
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2007-01-19, 18:09
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Supreme Metalhead
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Join Date: Mar 2006
Location: West Coast
Posts: 839
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Originally Posted by the_bleeding
dude, dont do it. you dont have a half power switch so your amp will still put power into all 4 sockets, and if theres nothing to carry the current, there will be big problems.
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Actually, pulling two power tubes is a pretty common practice. If the proper precautions are taken, it wont do any harm.
__________________
"So often our hands get caught up in ruts of muscle memory. 'Muscle memory' is an accurate term. We get used to doing certain things, without even being aware of them. This ultimately not only shapes and therefore limits our technique, it also shapes what we compose, what we write. We end up thinking still unknowingly trapped in that box." -Adam Nitti
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Originally Posted by the_bleeding
buy a stick of graphite (art stores) and rub it into your nut
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2007-01-19, 18:44
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Post-whore
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Join Date: Dec 2004
Location: Toronto, Canada
Posts: 1,816
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dude, my marshall has a half power switch which essentially takes 2 tubes out of the loop. I've renamed it the half ass switch because it murders the tone. With it on, i lose some gain (my distortion goes from metal --> rock), i lose clarity, and i lose overall tone. I also lose a tiny bit of volume, which i could fill back in on half power by turning it up a notch (1/12th) of the way (marshall knobs have 12 dots around them).
basically, the volume reduction is very insignificant versus the tone reduction. I wouldnt really reccommend it.
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Quote:
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Originally Posted by Dahmers Fridge
In the US "fanny" is a word used to describe the ass or butt. Here in the UK "fanny" is a lady garden (vagina)
I was very bemused as a youngster watching the Golden Girls when Blanche said she was going to "spank her fanny" I had visions of a geriatric vertical bacon sandwich red and bruised from being disciplined!!!
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2007-01-19, 18:57
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TEH PWNZOR!!!1qa
Alumni Staff
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Join Date: Aug 2003
Location: The West.
Posts: 4,433
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if you do take a pair out, it has to 1&4(outer two) or 2&3(inner two). it also doubles the impendance so you have to change that.
i wouldnt reccomend doing it though. that amp is pretty much a preamp gain amp so poweramp distortion isnt a huge role in it's sound. and making it 50w wont help you much in the lower volume department.
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