Looking for a schematic with 6-8 EL84s PP per channel, Preferably 8 Something like :: AUDIOVALVE :: unique highend tube amplifier made in germany .. , Have been looking on google but can only seem to find designs with 2-4 tubes. So do you know any designs like this or do you have the schematic for the avalon ?
(This is for a school project)
Regards x3me00/viktor
(This is for a school project)
Regards x3me00/viktor
Choose any circuit, including such for a 2 tubes, and multiply currents by the quantity you want, and divide the output impedance from the transformer for a same amount. Finally, add some low value resistors (10R) between plates, screens, and grids. And if you will use cathode bias, divide the ohmic value for them by the amount, and the power increased similarly. If they are operated without grid positive current, the driver no need modifications at all, nor the NFB if it exists.
I believe that 2 * 2 * EL84 needs more load impedance than 2 * EL34. EL34 needs about 3K and single push pull el84 needs about 11K, so 2 pairs need about 5-6Kohm for proper working. I´m remembering, so I may be wrong.
I make a board using EL84's called the Simple P-P. It uses a 6600 to 8000 ohm load for 15 to 25 WPC from a pair of tubes. To get 25 WPC you need good tubes and a B+ that is over spec. I have used NOS Sylvania 6BQ5 or JJ EL84 at 430 volts plate and 320 screen for 30 WPC with a 6600 ohm load.
I simply wired two channels in parallel through a common OPT for 60 WPC from 4 JJ EL84's with a 3300 ohm load and 430 volts B+.
Don't try this with wimpy tubes!
Tube matching is a good idea for any design where multiple tubes are paralleled, and usually required unless individual bias adjustments are used.
I believe that 2 * 2 * EL84 needs more load impedance than 2 * EL34. EL34 needs about 3K and single push pull el84 needs about 11K, so 2 pairs need about 5-6Kohm for proper working. I´m remembering, so I may be wrong.
I have been using a pair of EL84's in PP UL config on 8k pri. without any problems, a PPP config should be able to work nicely with 4k pri.
@TS:
Do you already have transformers for your project? If so, could you post the specifications of these transformers?
Wow... 430v plate... no fireworks? The mil-spec Sovtek EL84M should be more reliable at that kind of voltage...
430 volts is too much? Check out the Music Reference RM-10 amp. They claim to get 35WPC from a pair of EL84's by using 700 Volts on the plates and a 11000 ohm load! They also claim a 10000 hour tube life. 700 Volts? Even I haven't gone that far.....yet.
http://www.diyaudio.com/forums/tube...hifi-amp.html?highlight=Music+Reference+RM-10
References to the 700 volt supply are no longer mentioned on the companies web site.
http://www.diyaudio.com/forums/tube...hifi-amp.html?highlight=Music+Reference+RM-10
References to the 700 volt supply are no longer mentioned on the companies web site.
Jeez, with the experiences I've had with most Russian EL84s, that should be a good testbed for some interesting explosions!
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BTW, if the classic Dyna OPT's are any indication, 8k primary was used for a pair of EL84s in the Z565, while the A470 primary presents a 4.3k load to a pair of EL34s. So an A470 should work fine for a quad (PP-parallel) of EL84s, no?
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Ja ja ja, and the socket? Perhaps they use the old 1X2 25KV isolated sockets.
By the way
Have you seen this kit ?
https://taweber.powweb.com/store/kits_60b.htm#6M50H
Kagliostro
Have you seen this kit ?
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
https://taweber.powweb.com/store/kits_60b.htm#6M50H
Kagliostro
It is a bit rare that they don´t use anode resistors to prevent self oscillations, nor screen stoppers.
Would it be possible for you to provide some more information?
eg:
- What is the exact assignment that you have received from your school?
- Why do you need to run 6 or 8 EL84's per channel, why not a pair of 6550's?
- Do you have any building experience with high voltage projects?
- How should the output stage be connected to the output transformers (triode, pentode or UL)?
- What parts do you already have to your availability?
- Are you planning on hardwiring the amp or use a PCB?
etc...
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