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6-8x el84 Per channel

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Well lets start from above then :)

School Project : Put atleast 100hrs in to a electronics project (aka i could get away with an electronics essay if i wanted to but i want to build a tube amp).
Why EL84? : Well i like the el-84 i guess i could do with el34s aswell but id prefer el84 (dont want kt88 or 6550 ive never heard an amp with these).
Tube builds: Ive built 3 tube preamps (1 with phono stage) and then another phono stage and few diffrent regulated psus with both tubes and silicon.
Output tubes : No clue so far.
Parts: Well none of the major aka no transformers tubes etc.
Will most likely hardwire since its the easyest.

Regards x3me00/viktor
 
Yeah something like that

Ok, I could work out a little schematic for you however I have never paralleled eight EL84's so I can't guarantee it will actually work properly. Can I throw in a last attempt to steer you into a nice amp with 2 beefy output tubes that can deliver about the same output as eight paralleled EL84's but sounding much better while doing so? :)
 
The Beard P35 had 6*EL84 per channel.

Apparently Mr. Beard never published his schematics. But from the attached picture it is clear that each el84 had some kind of circuit. I read somewhere 7805's. And they also appear to by bypassed.

If I would have to build something similar I would insert a ccs in the tail of each pair to ensure good balance.
 

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The Beard P35 had 6*EL84 per channel.

Apparently Mr. Beard never published his schematics. But from the attached picture it is clear that each el84 had some kind of circuit. I read somewhere 7805's. And they also appear to by bypassed.

If I would have to build something similar I would insert a ccs in the tail of each pair to ensure good balance.

Is this seriously a commercial product? :headshot:
 
I've noticed sweep tubes have also been mentioned. Why not combine your precious EL84's with parallel sweep tubes?

An externally hosted image should be here but it was not working when we last tested it.


This is actually more easy to build than an OctoPP-el84, gives way more power output and is fully DC coupled, thus allows you to get rid of those nasty and expensive coupling capacitors :)
 
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Hmm i guess i could just havnt thought of it ^^ i wanted el84 / el34 for the reason i know they are good tubes ^^ how much power would this get me ? (about) (goal is above 60w but i dont want `` to much ´´ power either still want it to sound good:p)

The EL84 is a very nice sounding tube, I have listened to it for years with great pleasure until I started using PL519 output tubes and DC couple the whole thing :)

The power output depends on how you bias the output tubes. 60 watt's should be possible with a single pair of output tubes, thus a dual pair of output tubes should make 120 watt's possible. However, there are also amplifiers utilizing PL519 tubes which give 200 watt output power with a PPP config. Let's simply say these tubes have a lot of headroom available.

My current amplifier is utilizing a pair of EL509 tubes for the output stage, and is delivering 50 watt's per channel. IMHO this is more than enough for driving my speakers (Jamo D870's, 89dB/M) to insane levels. My ears break up before my sound system does :D
 
Allright possible to see the schematic of urs `? :)

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.


For the output transformer I would suggest to take one capable of handling 100 watts of power and with a primary impedance (A to A) of around 3k.
Compatible output valves are for example PL519, EL509/EL519 and 6P45S. I am currently using EL509's from JJ because of the octal socket and the lack of a top cap :)

-edit-
I found some reading material that described the basic idea behind the operation of the output tubes (screen drive) so you can get a better idea of how this amplifier works:
http://www.tube-town.net/info/sed-technotes/docs/technoteNo33.html
 
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