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Old 26th August 2011, 07:43 PM   #1
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Default A good sounding EL34 PP sch please

Hi all,


I've been given the makings of an EL34 PP amp - chassis, valves, iron etc. But I'd like to try a different driver stage. I've got about 500V of B+ to play with, good current capability and enough heater current to run the 4 EL34s, 2 x 12..7 and 600-800 mA of 6.3V heaters. Although I do have other Tx I could add in if more current is needed for heaters.

Could someone point me in the direction of a good sounding EL34 PP amp? Something with 6SN7, 6N2P or the 12..7 series would be an added bonus!!

I have searched, but its very hard to figure out what sounds best....


Fran
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Old 26th August 2011, 07:45 PM   #2
SY is offline SY  United States
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What sort of output iron? Are you committed to EL34 or is there flexibility?
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Old 26th August 2011, 07:48 PM   #3
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toroidal output iron is the kind..... and I don't have other spec's than the fact that they were used for EL34s. I suppose I could also put in KT66s or maybe even KT88, but I thought KT88 would need a bit higher B+ (+ more heater)

So, the long way round is that I'm kinda committed to EL34 unless a good argument is set up for something else!!

Fran
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Old 26th August 2011, 07:55 PM   #4
SY is offline SY  United States
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Impedance would be an important thing to know.

If I were sticking to tried and true output tubes, I'd be inclined toward 6L6GC in class AB2, which will get you 50-60 watts easy, and excellent 6L6GC are available dirt cheap.
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Old 26th August 2011, 08:15 PM   #5
DF96 is offline DF96  England
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"different driver stage" - different from what?

You could do a 5-20, although opinions vary about how much this needs to be modified.
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Old 26th August 2011, 08:18 PM   #6
rmyauck is offline rmyauck  Canada
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Do you have UL taps? Here's one with a Mullard style circuit.

http://www.lundahl.se/pdfs/claus_byr...fier_30wpp.pdf

There are many Dynaco ST-70 circuit's out there too that might work great. Some are Williamson types. Depends on your OPT's what you use.
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Old 26th August 2011, 08:18 PM   #7
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The existing amp is an old KEL34 from world audio designs... see the attached PDF for the sch. Its mostly built on a PCB, so I suppose I was looking for something to play with that would be an improvement on that....
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File Type: pdf kel34.pdf (53.9 KB, 787 views)
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Old 26th August 2011, 08:24 PM   #8
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My vote would be this, using original ST70 iron or anything reasonably close in primary impedance. Very pleased with the sound. 500V sounds a tad rich for me, but you could go with cathode bias. My preference is strongly toward triode connection; I don't bother with the UL switch.

Take what you like and spit out the bones.
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File Type: pdf ST70schematic.pdf (48.9 KB, 601 views)
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Old 26th August 2011, 08:26 PM   #9
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Zigzag: I take your point and agree, but I already have a st70 running kt66s and was going to go for something else. The st70 does sound lovely driving my quads....


Fran
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Old 26th August 2011, 08:52 PM   #10
Bone is offline Bone  United Kingdom
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There's always the old Linear 30 watt circuit here Linear Conchord 30w Amplifier . I can verify that does sound nice as I used to have two back in the day.
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