Further auditions.
The 6V6 pre enthused in the system of the fellow DIYer. The 'hssst' transients never appeared again. Due to less efficient speakers than mine, 'ding' sounding microphonics when the envelope is striken, are even less. Not more than his 6SN7 pre he said. Its moving to another housing with 5R4GY 300V supply passively filtered with chokes, and a warmer operating point. Testing continues. Will let you know.
The 6V6 pre enthused in the system of the fellow DIYer. The 'hssst' transients never appeared again. Due to less efficient speakers than mine, 'ding' sounding microphonics when the envelope is striken, are even less. Not more than his 6SN7 pre he said. Its moving to another housing with 5R4GY 300V supply passively filtered with chokes, and a warmer operating point. Testing continues. Will let you know.
Current version even better
The preamp right now follows the attached schematic. It works even cleaner with even more impact and warmth. The early desired and now realized operating point is indeed the best. Current is 22mA, cathode stays at 15V give or take. Gain is around 7 times.
The NOS prewar 6V6Gs are wonderful sounding. Their microphonics are good enough for practical use, but we are looking for NOS GT variables and square plated old and new to determine the best in both departments and broaden our choice in sonic flavor. A good contestant for building this line pre with new and available is JJ 6V6S with strong square and ribbed plates as long as the new Russian Tungsol with oval ones. Both have good reports for tone and microphonicity. We intend to check em out. Remember that you cant go wrong with any 6V6 make in triode mode, its a sweet little gal, the Evangeline Lilly of tubes. Build this pre and you cant get LOST. Highly recommended. It beats the OTHERS.😀
The preamp right now follows the attached schematic. It works even cleaner with even more impact and warmth. The early desired and now realized operating point is indeed the best. Current is 22mA, cathode stays at 15V give or take. Gain is around 7 times.
The NOS prewar 6V6Gs are wonderful sounding. Their microphonics are good enough for practical use, but we are looking for NOS GT variables and square plated old and new to determine the best in both departments and broaden our choice in sonic flavor. A good contestant for building this line pre with new and available is JJ 6V6S with strong square and ribbed plates as long as the new Russian Tungsol with oval ones. Both have good reports for tone and microphonicity. We intend to check em out. Remember that you cant go wrong with any 6V6 make in triode mode, its a sweet little gal, the Evangeline Lilly of tubes. Build this pre and you cant get LOST. Highly recommended. It beats the OTHERS.😀
Attachments
6V6GT tests
Good news! 6V6GT Miniwatt and Sylvania showed no peculiar self noises at all! They sound a treat too. We had a good comparison yesterday with properly executed 6SN7 (cascade) and 6V6GT (as above). Also a 12AU7 (cascade) one. The 6V6 idea reigns in musicality and richness. Confirmed by Bob too.
Good news! 6V6GT Miniwatt and Sylvania showed no peculiar self noises at all! They sound a treat too. We had a good comparison yesterday with properly executed 6SN7 (cascade) and 6V6GT (as above). Also a 12AU7 (cascade) one. The 6V6 idea reigns in musicality and richness. Confirmed by Bob too.
Attachments
Wow, you've got THAT outside your window? I hope that you're using Cardas Golden Ratio cables then. You don't want to make the gods angry.
Its right across my good friend's balcony where the yesterday tests took place. Sadly I did not have a tripod with me to engage a night mode long exposure.
*Parthenon has yet another trick up its sleeve. No right angle nowhere. Its quasi right. So it looks right from underneath.
*Parthenon has yet another trick up its sleeve. No right angle nowhere. Its quasi right. So it looks right from underneath.
EL84 Balance output
Hi Jane,
I don't think you can get the balance output from this output transformer. It can be only used for Single Ended output.
You need an OPT with CT.
Please correct me if I am wrong.
Johnny
Hi Jane,
I don't think you can get the balance output from this output transformer. It can be only used for Single Ended output.
You need an OPT with CT.
Please correct me if I am wrong.
Johnny
rdf,
It looks like the output is being taken off the screen. If you look closely, the screen does not appear to be connected to the bypassed cathode; the suppressor is however.
It looks like the output is being taken off the screen. If you look closely, the screen does not appear to be connected to the bypassed cathode; the suppressor is however.
The screen is being used as the anode. The plate is run at a very low voltage, almost turning it off. The screen's transconductance (dIc2/dEc1) will increase above its usual value when it conducts more current than the plate. The screen's dissipation is about 250mW, well below its 2 watt rating. Is all this advisable? I don't know.
I think that Steve Bench's site describes using the screen as the output anode.
I think that Steve Bench's site describes using the screen as the output anode.
They use the screen as an anode. Somebody probably wanted to make a small tube out of a bigger one that was available. Maybe ill advised soundwise since the big current is a plus if used as a triode with output normally taken off the plate.
Re: EL84 Balance output
Actually you don't need a center tap for balanced operation at all, particularly simple if the device on the other end is another transformer. Not a bad idea though to connect the chassis together through the xlr ground connection. Most transformer coupled pro gear does not use a center tap.
kmtang said:
Actually you don't need a center tap for balanced operation at all, particularly simple if the device on the other end is another transformer. Not a bad idea though to connect the chassis together through the xlr ground connection. Most transformer coupled pro gear does not use a center tap.
yes,The plate is run at a very low voltage, almost turning it off in this case,it make the 6V6 look like be close to a triode with low internal resistance.
A=5.5V is necessary,we can use a regulate circuit to make it adjustable for the output gain.
A=5.5V is necessary,we can use a regulate circuit to make it adjustable for the output gain.