Did you learn the causes of your blurred soundstage or early clipping ?
That's probably a good idea but I wouldn't blame the 5842. Cathode bias with big cap is not a great way IME to use a 5842 but it's not the tube's fault. 5842s can sound good in the right circuit for the job.
If you read more of Romy The Cat you might get a sense of where he's coming from and not worry about it too much ;-)
Of course, if you think those 417As will embarass you in front of your Cat fancier audiophile friends just send them to me... I'll pay the postage.
Cheers,
Michael
PS Here's a scope trace of a 5842 swinging a power tube grid 300V peak-peak
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About 190V/10mA
My signal generator may be pushing the 5842 grid about 0.5V positive, which seems to happen without an abrupt transition... It would be about 250V Pk-Pk if you kept the grid from going +
Oh yes, diode bias and a gyrator in the anode circuit
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OT: Mike, I'm using tube based gyrators as loads in my phono stage - nice to see someone else also using gyrators. I'm sure the fets work better, but I am getting good results..
Note that Mike's circuit is not as obvious as it first seems due to the direct coupling and a floating 75V supply on top of the 270V supply.. The biasing arrangement for the 4-65 appears to be quite interesting. (And clever)
Note that Mike's circuit is not as obvious as it first seems due to the direct coupling and a floating 75V supply on top of the 270V supply.. The biasing arrangement for the 4-65 appears to be quite interesting. (And clever)
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I agree with Kevin, the issue is reduced resolution on the amp.
Check all voltages and currents.
Check all filament supplies (too low voltage com degrade sound), but there are some detais cannot forget to correct:
grid stoppers, as already said
the 0,22uF is too small for a 250k load
the signal in the 300B goes via the filament transformar. Check impedance for signal.
The 1Vrms limit is not acceptable, you need more headroom, even if it means reducing stanby current for the tubes.
Check all voltages and currents.
Check all filament supplies (too low voltage com degrade sound), but there are some detais cannot forget to correct:
grid stoppers, as already said
the 0,22uF is too small for a 250k load
the signal in the 300B goes via the filament transformar. Check impedance for signal.
The 1Vrms limit is not acceptable, you need more headroom, even if it means reducing stanby current for the tubes.
Wes you are right. I am usually using them with a 50 W solid state amp. This is just to confirm the pb of sounstage I have with the tube amps. The PM610 are 92 dB! And and the level in the room can be pretty loud!
Cheers,
Jean-Paul
TubeLab has no grid stopper resistors at the 5842 in his TubelabSE design. Are there any drawbacks using grid stoppers?
I use a Lundahl LL1623 as output transformer in my TubelabSE amplifier. The LL1623 is strapped for 6 kohm primary load impedance. The 300b runs att B+ 425 V 80mA and the 5842 at 180V 10 mA. I then get 8 W over 16 ohm before clipping. I really like the Lundahl OT, I think they sounds great
I use a Lundahl LL1623 as output transformer in my TubelabSE amplifier. The LL1623 is strapped for 6 kohm primary load impedance. The 300b runs att B+ 425 V 80mA and the 5842 at 180V 10 mA. I then get 8 W over 16 ohm before clipping. I really like the Lundahl OT, I think they sounds great
He has grid stoppers. R31 and R32. They are just absent from the schematic but you can see them in the parts list and the build instructions. In fact, he recommends increasing their size from the specified 1k to 4.7k and even using carbon comp. Apparently some people were having issues with oscillation.
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