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Old 16th September 2010, 11:31 PM   #1
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Default quad el84 or PP el34

Im trying to decide if the pain of going over 400 volts is worth it.

I want to make a oddwatt/simple el84 type setup with a ccs in pp arrangement. However my test el84 setup with b+ of 230,ccs of 83ma for the pair and 7200ohm primaries in pentode mode, wasnt loud enough to drive my dayton reference MTM's with very complicated crossovers.

I figure thats 9 watts of plate dissipation with the current setup. Now the el84 can do 12 watts plate, and i have the nice russian 6P14P-EV on hand. I also have a set of winged-C el34's. The el34 dissipates 25 watts.

So the question is, do i do 2 pair of el84's with half the primary impedance, or do i do a normal el34 setup?

The oddwatt uses 450volts with an 8k primary and a ccs of 125ma. So thats a plate dissipation of 28watts with half the recommended load(??? he normaly does 80% of max plate).
If i just doubled up the el84 and upped the voltage to 300 that would give me about 12 watts of plate, and i would need 4k primaries. So thats about the same power as the el34 setup. But the B+ means i can use way less expensive caps and even some silicon regulators if i want.
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Old 17th September 2010, 05:09 AM   #2
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Hi!

I would not go with CCS in cathodes to drive speakers with complex crossovers. I would use EL84 tubes with fixed bias instead, and local feedbacks by voltage across them.
Either one pair of EL34, or 2 pairs of EL84, the end result will be similar, but less tubes means easier bias adjustment.

Also, 6P41S would be a good option for this case. They are cheap and wide available currently, greatly under-priced. With +140V stabilized screen grid voltage it looks like 2 of EL84 in parallel.

Just my +2 cents.
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Old 17th September 2010, 07:37 AM   #3
Ian444 is offline Ian444  Australia
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You need more B+ to get the max out of a pair of EL84, say aim for 320V across the tube, that will give a lot more power than 230V B+. Also, if you use fixed bias and a standard LTP or cathodyne phase splitter, that will get you out of Class A into AB for around 15W per channel. Oddwatt is limited to Class A, I built one and liked it, but Class AB will give more power. It depends on your needs/desires in which direction you go.
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