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I have a Peavey Guitar amp, model Duel 212. Peavey claims it outputs 120 watts. (Which I question.)
The output tubes are push pull as you might expect, but to get that high output they parallel two 6L6's on each side going to a massive OPT.
What are the plus's/minus's of a design like this? It seems pretty common on high power guitar amps, but I don't recall seeing the same design used for high fidelity audio amplifiers.
Proudly serving content-free posts since 1984.
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Never was a big fan of these powerful amps from Peavey. One thing... They are LOUD. And very hard on tubes. Not the easiest to work on.I would not mod this amp. Keep it as stock as possible. Go for tube rolling and speaker exchange to alter tonal response. Maybe, look for a good pair of JBL D120F? And a heavy-duty dolly jack to cart the amp around.
8^)
Edits: 05/30/16
I know some early Mesa-Boogie amps that needed 7581A or STR 6L6GC just to meet the high output requirements.I'll check schemo, once I get off work, here...
8^)
Edits: 05/27/16
Steve
The schematic I looked at doesn't show the output transformer but it shows the output stage and the power supply.There are two sources off the power supply for the opt stage,one for the plates which are 480v and the other for the screens which are 475v so that would mean that it isn't UL otherwise it would have one source for the output stage.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Because they are running 480v on the plates and 475v on the screens and the cathodes are grounded directly and the amp runs into AB2. Of course the 120 watts is coming at a much higher distortion but it does make 120 watts on measurement. I tested one of these amps four years ago as I was also shocked at the numbers but they make it.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Edits: 05/28/16
The schematic I have for that amp shows the grids being driven through coupling caps. It's not AB2, just an example of tubes pushed to their absolute limits with elevated operating voltages. Also, the standard specs for 6L6GC indicate this is way above the continuous power rating of the tubes. Even at a somewhat reduced anode voltage compared to the Peavey, maximum plate dissipation would be about 95W per pair at full output (450V x 210mA). It wouldn't take long to melt the tubes under those conditions.
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Buy Chinese. Bury freedom.
I saw the four tube output stage and the power supply and I realize you won't get 120w continuous but at those voltages you can certainly peak at 120 watts even without driving the the grids positive.I figured it may have a MOSFET driver DC coupled to the OPT grids driving it into AB2 to get those power ratings..I did see a FET in part of the schematic but it wasn't the driver..I just assumed they were using an DC coupled driver to get those numbers.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Man, that's a lot of voltage for a 6L6! I wonder how long a quad of 6P3S-E would hold up under those conditions...
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Buy Chinese. Bury freedom.
they have less dissipation than a 6L6gc..They are more along the lines of a 6L6gb but can handle much higher voltage..Look at my Scott 280s.I'm running almost 600v on the plate and I was running 260v regulated on the screens biased at around 35ma..I usually run them at 520v and 320v on the screens but I wanted to prove a point with these tubes at the time.They can take some major abuse.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
I've had this amp only for about a month, and I'm no pro, just for my own enjoyment. I've read every review I could find, and (so far, no mention of short tube life. is there a 6l6 variant or sub that has better specs for this application?
Proudly serving content-free posts since 1984.
If you use the amplifier as it was intended, i.e. musical equipment amplification, plate dissipation is unlikely to be exceeded. Tube life will probably be determined by idle current (screens and anodes) more than anything else.
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Buy Chinese. Bury freedom.
It's a standard push pull amp. Parallel output tubes will give more power. However they should be matched to even out the load on the tubes.
There are many examples of this in hifi amps as well. Check out Audio Research, McIntosh, Rogue and numerous others.
You are also correct 120 watts is a pipe dream.
Dan Santoni
It used to be that 4-6L6 amps like Fender Twins etc were rated at 85-100 Watts. Peavey squeezes a little more power out of the four tubes by running higher plate voltage and less plate load. You need a matched quad set of good tubes to be dependable in those amps.
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