I have always admired Dave’s “pretty” schematics. What software? If you don’t mind telling. Also, I suggest moving down the “Ia = 5 ma” (perhaps next to the 100 Ohm resistor). As is it appears the intent is a current in the circuit branch to the next stage.
Eli, as a potential builder of the clone Cit. V, I would like to know why the 12 watt plate resistor? I calculate it will dissipate only 1 watt, so 5 watts will be plenty. Or do you have a particular preference for the sound of the 12 watter?
somehow, i am unable to get the connection on the right work for me, i always ended up returning the grid 2 bypass cap to ground....am i crazy or something?
Thanx. Vectorworks. My symbols have evolved as i have seen ones i like more than the ones i was using.
It is in the sam eplace Eli put it, so perhaps he can weigh in.
dave
Thread cleanup has been completed, please keep it civil and on topic going forward.
the 12HL7, 11hm7, 12hg7, 12gn7 video pentodes seems to be a good replacement for the 12by7, any one want to try....???
the russian 6J9 i have used and is also very good in a mullard 5-20 which this citation 5 borrowed from....
the russian 6J9 i have used and is also very good in a mullard 5-20 which this citation 5 borrowed from....
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AFAIK, 40.2 K does not come in a MRA-5. Check Michael Percy's catalog out. In any event, my "belt and suspenders", AKA anal, mindset is content. 😉 If you can scrounge up a meter matched pair of 5 W. carbon film parts, say KOA-Speer, whose value is correct, they too should be fine. What I would avoid, if at all possible, is an "icy cold" metal film part in that position.
MRA-12 is the correct character string. The parts are claimed to be capable of dissipating 12 W. I have my reservations about that claim and always allow some leeway. What if air circulation is poor? Since I'm always berating manufacturers over the reliability issue, I definitely need to watch my manners too.
No, no, a thousand times no!
Stu Hegeman exploited high gm types and obtained excellent results. While nicely linear, the EF86 is the antithesis of high gm.
Tony, could you clarify, please. Do you mean you don’t understand the connection on the right, or have you wired (or simulated) it and it didn’t work? So, are you saying you always ended up returning to the connections in the HK schematic Eli posted in #9? Now I am really confused about what the correct schematic is.
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the correct schematic is the one on the right, what i am trying to say is, when i follow that schematic, i end up unhappy, so that instead of returning the bypass cap to the cathode in the 12by7, i connect it to ground instead...
I've enjoyed reading through this thread. I really like the sound and performance of the 6L6GC/7581A operated at higher supply voltages, and the Citation V is a classic example. My neighbor had one when I was growing up.
I wish New Sensor or JJ would introduce a REAL 7027A capable of running reliably at plate voltages above 500v. The Tung Sol Reissue 7581A seems like a great tube, but I'm uneasy taking it above 500v.
Scott
I wish New Sensor or JJ would introduce a REAL 7027A capable of running reliably at plate voltages above 500v. The Tung Sol Reissue 7581A seems like a great tube, but I'm uneasy taking it above 500v.
Scott
The bypass C connected to the cathode keeps the AC screen current compensated at the cathode (a local loop).
By returning the bypass to ground, the cathode effectively sees the variation of screen current across it's cathode R. That I think would produce softer clipping, and without N Fdbk correction. But only for the signal polarity where the Plate V drops below the Screen V. Might be interesting if the other signal polarity could be soft clipped as well.
Hi Scott,
My experience with New Sensor tubes so far has been very good. Their Electroharmonix 6L6EH / 6L6GC will handle a FenderTwin without any trouble, so that is a plate running at 475VDC approx. Normally the only other tube I would trust are the good 7581A types. My amplifier I have on the design block is running 6L6GC tubes above 450 VDC just fine, and my new power transformers push the B+ to about 475 VDC. I'm more worried about capacitors than the output tubes.
-Chris
My experience with New Sensor tubes so far has been very good. Their Electroharmonix 6L6EH / 6L6GC will handle a FenderTwin without any trouble, so that is a plate running at 475VDC approx. Normally the only other tube I would trust are the good 7581A types. My amplifier I have on the design block is running 6L6GC tubes above 450 VDC just fine, and my new power transformers push the B+ to about 475 VDC. I'm more worried about capacitors than the output tubes.
-Chris
thanks, tried it twice and did not like it....my tact now is a CCS with zeners to regualte G2...worked nice for me..
hey Chris.
i bought a quad of JJ6L6GC's and boy did they bias exactly the same and up to the first decimal point, i was flabbergasted, can you beat that....😎
Hi Tony,
The question is ... can New Sensor beat that?
Pretty close to the same performance. I set the bias voltages on some 6L6EH the same for initial power up on an amp, and they were all close to each other. My experience with the original tubes certainly wasn't like this. Tube manufacturing has come a long way over the years!
-Chris
The question is ... can New Sensor beat that?
Pretty close to the same performance. I set the bias voltages on some 6L6EH the same for initial power up on an amp, and they were all close to each other. My experience with the original tubes certainly wasn't like this. Tube manufacturing has come a long way over the years!
-Chris