Merry Christmas,
Here is a link to the ones I purchased.
McMaster-Carr
McMaster also has sorbothane grommets which I think would even be better.
Here is a link to the ones I purchased.
McMaster-Carr
McMaster also has sorbothane grommets which I think would even be better.
6v6 CCS loaded CF compared to 12b4 Gyrator loaded
Attached are two curves comparing my old 12b4 gyrator loaded preamp vs. the new 6V6 CCS loaded CF. I quickly threw together my measurement system and calibrated it. Noise floor is -145db and is flat from 20 to 44kHz.
All measurements were taken with 1Vrms signal and ploteed so that 1Vrms = 0dB. The soundcard is a 1616m using audiotester software. Audio Tester has come along way from the last time I used it. Did not have one crash.
The first plot is frequency response. the -3dB for the 6V6 is beyond my measurement set-up.
The second plot is the FFT of a 1kHz signal. What immediately jumps out is the difference in noise floor. Keep in mind that the 6V6 is currently configured is using AC heaters with no attention to sheilding and a marginal ground scheme. What I havn't shown is that even with the 6V6 isolated on grommets, it isn't enough isolation. The plot used here is with the preamp resting on acoustic felt to decouple it from the counter. The remaining grass seen on the 6V6 plot is, imho, a combination of ground loops, acoustic noise polution and microphony of tube, and absolutely no shielding.
The distortion of the 12b4 measures 0.133% while the 6V6 measures 0.031%. Very nice improvement.
In general I continue to enjoy this change in my system. Certainly more tweeks to come like DC heaters, better shielding and improved mechanical decouplings of the tube.
Attached are two curves comparing my old 12b4 gyrator loaded preamp vs. the new 6V6 CCS loaded CF. I quickly threw together my measurement system and calibrated it. Noise floor is -145db and is flat from 20 to 44kHz.
All measurements were taken with 1Vrms signal and ploteed so that 1Vrms = 0dB. The soundcard is a 1616m using audiotester software. Audio Tester has come along way from the last time I used it. Did not have one crash.
The first plot is frequency response. the -3dB for the 6V6 is beyond my measurement set-up.
The second plot is the FFT of a 1kHz signal. What immediately jumps out is the difference in noise floor. Keep in mind that the 6V6 is currently configured is using AC heaters with no attention to sheilding and a marginal ground scheme. What I havn't shown is that even with the 6V6 isolated on grommets, it isn't enough isolation. The plot used here is with the preamp resting on acoustic felt to decouple it from the counter. The remaining grass seen on the 6V6 plot is, imho, a combination of ground loops, acoustic noise polution and microphony of tube, and absolutely no shielding.
The distortion of the 12b4 measures 0.133% while the 6V6 measures 0.031%. Very nice improvement.
In general I continue to enjoy this change in my system. Certainly more tweeks to come like DC heaters, better shielding and improved mechanical decouplings of the tube.
Attachments
Last edited:
Further Improvements
An update. The pre now runs with better ground pattern, ceramic caps from heater to ground on the base, plus a SSLVS(ver1) modified for filament duty. Attached is the FFT measurment. Red being before and Blue being current. 1Vrms Input = 0dB.
Measurements are good, but this may be a case where too much good is bad. While it is fully enjoyable, I almost prefer the way it sounded before. The majority of the 60Hz bump is my monitor sitting right next to it.
An update. The pre now runs with better ground pattern, ceramic caps from heater to ground on the base, plus a SSLVS(ver1) modified for filament duty. Attached is the FFT measurment. Red being before and Blue being current. 1Vrms Input = 0dB.
Measurements are good, but this may be a case where too much good is bad. While it is fully enjoyable, I almost prefer the way it sounded before. The majority of the 60Hz bump is my monitor sitting right next to it.
Attachments
why the blue peak at 1khz
That is the fundamental in the FFT measurement.. To the right are the harmonics of the fundamental, and to the left is the residual LF noise..
I've seen it in the line stage of a tube comp I use.
but the whole thing is p-p line stage.
Attachments
Salas,
I have been poking around your threads and this one seems the most interesting or maybe the shortest, I don't know which. THat being said, anybody who listens to Sytem of a Down and owns tube gear, knows something, so want to build this and wasnt sure if this was the final schematic. I know you tried CCS instead of resistors but droppped because of gain and sound issues. Let me know so i can get building! First tube amp
I have been poking around your threads and this one seems the most interesting or maybe the shortest, I don't know which. THat being said, anybody who listens to Sytem of a Down and owns tube gear, knows something
, so want to build this and wasnt sure if this was the final schematic. I know you tried CCS instead of resistors but droppped because of gain and sound issues. Let me know so i can get building! First tube amp