When run some many tubes in the past to pick some out the available new Russian "Tungsol" was one of the quieter and tonally balanced and the Sylvania VT107A NOS was such also. The Miniwatt too. But they change production standards some times on the new ones so you cant be 100% sure. What about the 6K6 that disco says is behaving well? Can you get any? Units differ in same type even both in NOS & new especially in noise and microphony. That is why they select them in expensive preamps especially if phono.
6K6 alternative
6K6 is the electric equivalent of #41 and can be dropped in place of the 6V6 in Salas' circuit. My setup is without cathode bypass, Rcat= 700 ohm, Rload= 5K. The supply voltage is not too critical, I measured 292V. My volume pot reaches unity gain at three 'o clock setting. I could not measure F-3dB, at the limit of my tone generator (10Hz). Output coupling is .68uF, for driving my high input impedance tube amp good enough. No microphony issues at this operating voltage.
B+ 292V
anode 192V
cathode 15V -> 21mA (Rc = 700 ohm)
This specimen is from Visseaux. It was produced for TV sets, probably in the 1950s.
The plate has a round shape while US models have the oval shape.
6K6 is the electric equivalent of #41 and can be dropped in place of the 6V6 in Salas' circuit. My setup is without cathode bypass, Rcat= 700 ohm, Rload= 5K. The supply voltage is not too critical, I measured 292V. My volume pot reaches unity gain at three 'o clock setting. I could not measure F-3dB, at the limit of my tone generator (10Hz). Output coupling is .68uF, for driving my high input impedance tube amp good enough. No microphony issues at this operating voltage.
An externally hosted image should be here but it was not working when we last tested it.
B+ 292V
anode 192V
cathode 15V -> 21mA (Rc = 700 ohm)
An externally hosted image should be here but it was not working when we last tested it.
This specimen is from Visseaux. It was produced for TV sets, probably in the 1950s.
The plate has a round shape while US models have the oval shape.
An externally hosted image should be here but it was not working when we last tested it.
The 6p6s is usually far from the worst, actually usually a good performer. I think I supplied George with a matched pair that he was happy with and he had tried alot of brands/types before. He also had the notion that aging affected microphony. The earlyer had gone worse with time I think he said. So its your choice.
6K6 looks like a 6V6 construction without the beam guides but with a normal extra grid. Is that making it less prone to mechanical instability? Alas, not everywhere and not cheap when nearly unused.
That's encouraging. That fix and film coupling caps will let it come out cleaner.
The construction and fitting of the micas (transparent stuff that holds the electrodes to the glass envelope on the top side) is usually the biggest difference between tubes of the same type. 6V6 has a number of different constructions on that. Then is ofc the design of the electrodes themselves. 6V6 is a spec. How one constructs something that lives up to the spec is up to the manufacturer.
OK some more comparisons !
I compared the 6V6 with a 6922 preamp. This was a 6922 . Standard triode gain stage followed by another stage as a cathode follower . That was done as it appeared to sound better with a follower output.
Anyway , the 6V6 sounds better in many ways. Instruments sound slightly cleaner. Different type of layout and type of parts . That could contribute also I think.I guess with the proper supply approaching 300V the 6V6 might get better !
The electrolytic cap appears to have 'formed' and is now sounding much better. HF is very good. One area that shows up very quickly. But will try the film cap also.
I think the 6L6 is quite similar though the tube is very bulky. Will try this out again later. I want to try the tubes with either a Zener or LED's in the cathode ! Gain doesn't go up to much.
Salas, you mentioned about tube construction.
Genalex,EH,Tung Sol and Mullard have four tiny metal strips that keeps the tube structure away from the tube wall.
JJ and TAD use the usual mica spacer. Will that make them less microphonic ?
I compared the 6V6 with a 6922 preamp. This was a 6922 . Standard triode gain stage followed by another stage as a cathode follower . That was done as it appeared to sound better with a follower output.
Anyway , the 6V6 sounds better in many ways. Instruments sound slightly cleaner. Different type of layout and type of parts . That could contribute also I think.I guess with the proper supply approaching 300V the 6V6 might get better !
The electrolytic cap appears to have 'formed' and is now sounding much better. HF is very good. One area that shows up very quickly. But will try the film cap also.
I think the 6L6 is quite similar though the tube is very bulky. Will try this out again later. I want to try the tubes with either a Zener or LED's in the cathode ! Gain doesn't go up to much.
Salas, you mentioned about tube construction.
Genalex,EH,Tung Sol and Mullard have four tiny metal strips that keeps the tube structure away from the tube wall.
JJ and TAD use the usual mica spacer. Will that make them less microphonic ?
You are comparing a buffered low Zo 6922 preamp with a 4K Zo non Rk bypassed non finished and in lesser operating point weak for bias current experiment. Still you already like it better. You are on a good path for finishing it properly that says.
Avoid LEDS or other semis in the cathode circuit in this one IMHO.The stronger they look constructed the stronger they manage against vibrations in circuit too as usually. Mechanical tolerances are important whatever the techniques.
Hi Salas, the same 6922 preamp sounds much better with an ECC82 (NOS-Mullard) at the input.
But I plan to refine the 6V6 preamp and get a couple of more tube brands, Tungsol and maybe JJ . EH also has them but I'm not sure how they will sound.
I will also complete my 6SN7 tube preamp which has been lying in storage for a very long time ! All octal !
But I plan to refine the 6V6 preamp and get a couple of more tube brands, Tungsol and maybe JJ . EH also has them but I'm not sure how they will sound.
I will also complete my 6SN7 tube preamp which has been lying in storage for a very long time ! All octal !