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A good sounding EL34 PP sch please

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woodturner-fran

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Joined 2006
#1
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
 
#3
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
 
#8
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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#11
#14
The PP2C looks interesting indeed.... I've gone back to ask about the impedance of the OPT, but given as it was made especially for a PP EL34, I'm guessing that the impedance should be about right.

Many thanks for all the suggestions so far!! Is there a thread somewhere about the PP2C? - a search didn't throw up anything...


Fran
 
#15
PP2C was originally developed for an ST70 donor. Issues may be providing sufficient heater current (but this amp really deserves an indendent heater supply) and a shunt reg is mandatory on top of the cascode LTP.

My buddy is building one of these and i am gathering parts for an EL84 derivative.

dave
 
#18
Yes indeed...the EL84 amp is quite a nice little setup. I may start collecting my iron for this one as well. I have been wanting to build a higher power tube power amp in a more contemporary enclosure chassis. Like a HiFi2000 3U if it could fit or maybe a 4U if height dictates. The P2P + EL34 height will dictate that. A hammond 10X12 bottom plate should work nicely with a few bends in it....

Power Xformer
OPT's
 
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#19
I would also like to experiment with an LED bias scheme for the first triode input in lieu of the cathode resistor. This worked wonders on the EL84 amp.

Another interesting approach would be a CCS on the EL34's. I am running 80mA per channel on an LM317 on the EL84 as well.

push-pull%20power%20amp%20example%20for%20ps-4.png
 
#20
If you want triode....

There's also Poinz' 6GK5/EL34 Music Machine. Triode, Fixed bias, CCS under the LTP, very straightforward design...about 12-14W or so.

The power supply in my MM is a fairly conventional CLC.....

Required OT impendance is 5K.
 

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  • poindexter 6gk5-el34 schematic.gif
    poindexter 6gk5-el34 schematic.gif
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