Fizzy,crackly distortion from speakers on 36watt lite
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Fizzy,crackly distortion from speakers on 36watt lite
I built a 36 watt lite and it has some nasty trailing distortion when cranked up a bit.It's not a cold solder joint or biasing issue and all the usual suspects like tubes and such have been eliminated.
The plate dissipation is 13 watts.
It sounds like an oscillation and it does lessen considerably when I upped the grid stopper resistors from 8.2k to 220k but it's still there.I could go larger on the grid stoppers but the highs are suffering from the increased stopper values.
Is this the dreaded EL84 fizz problem?
I'm using a separate pair of cathode resistors and caps for each pair of tubes so I'm wondering about the Paul Ruby fix and how one would implement it with separate R/C's ?
Any insight would be appreciated.I have built quite a few 36 watters and this is the first one with this issue.
The plate dissipation is 13 watts.
It sounds like an oscillation and it does lessen considerably when I upped the grid stopper resistors from 8.2k to 220k but it's still there.I could go larger on the grid stoppers but the highs are suffering from the increased stopper values.
Is this the dreaded EL84 fizz problem?
I'm using a separate pair of cathode resistors and caps for each pair of tubes so I'm wondering about the Paul Ruby fix and how one would implement it with separate R/C's ?
Any insight would be appreciated.I have built quite a few 36 watters and this is the first one with this issue.
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- zaphod_phil
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Re: Fizzy,crackly distortion from speakers on 36watt lite
Yikes. EL84s are rated for 12W max.The plate dissipation is 13 watts.
Looks like it probably is.Is this the dreaded EL84 fizz problem?
That doesn't make any difference. The Ruby buzz fix involves a zener and regular diode connected to *each* power tube grid - so four grids get the treatment instead of two. You may also want to add a clamping zener across the cathode caps of each P-P pair.I'm using a separate pair of cathode resistors and caps for each pair of tubes so I'm wondering about the Paul Ruby fix and how one would implement it with separate R/C's ?
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Nature abhors a clean tube amp
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The Lar-Mar shouldn't make any difference either, as IIRC it sits on the PI side of the coupling caps to the EL84 grids. The Ruby mod diodes are connected directly to each EL84 grid. The only question is what voltage the zeners should be. One rule of thumb is to use a value around 2V higher than the cathode voltage at idle.
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Nature abhors a clean tube amp
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