Phase Inverter Circuit Differences between SSS#2 and SSS #4

[StratStringSlinger]

I heard the phase inverter circuit is different between SSS#2 and SSS#4, can someone please enlighten us on the differences? Bonus points for what he was trying to accomplish by this. Thanks.

[jazbo8]

Anyone has the schematic for the SSS #4? Only #1 and #2 are shown in the files section... Or a verbal description of the PI CF will do...

[mhartman]

SSS#2 is posted in the files section. SSS#4 didn't have the CF, it is just a standard Dumble style PI. To me, the amp is a bit "warmer/rounder" without the CF, but it doesn't have the same "zing" to it. Also, with the CF, the bass is deeper and tighter.

[jazbo8]

Great, good to know the tonal difference between the two as well.

Thanks!

[mhartman]

Great, good to know the tonal difference between the two as well.

No problem. When I build my SSS, I made the PI section with a "modular" board so I could hear it both ways (it is more than just plug and play through because both methods require a different bias setup). I ended up sticking with the CF because it really took the amp to the next level and gave it that unique SSS sound. That being said, it sounded really nice both ways.

[jazbo8]

Great, good to know the tonal difference between the two as well.

No problem. When I build my SSS, I made the PI section with a "modular" board so I could hear it both ways (it is more than just plug and play through because both methods require a different bias setup). I ended up sticking with the CF because it really took the amp to the next level and gave it that unique SSS sound. That being said, it sounded really nice both ways.

The CF configuration is a bit scary with the large voltage potential between the plate and the cathode, but I guess the 12AX7 CF runs fine with it, what's your experience? It does not shorten the life of the tube, does it?

[mhartman]

Great, good to know the tonal difference between the two as well.

No problem. When I build my SSS, I made the PI section with a "modular" board so I could hear it both ways (it is more than just plug and play through because both methods require a different bias setup). I ended up sticking with the CF because it really took the amp to the next level and gave it that unique SSS sound. That being said, it sounded really nice both ways.

The CF configuration is a bit scary with the large voltage potential between the plate and the cathode, but I guess the 12AX7 CF runs fine with it, what's your experience? It does not shorten the life of the tube, does it?

I haven't had any wear out. That being said, you may have to go through a few to find a good tube. Some brands don't work well as CFs. I like to use NOS JAN 12AX7s in mine for the CF.

[jazbo8]

Good idea, some of the newer made tubes may not be as robust as the NOS nor sound as good,

Thanks!

[Mark]

Why wouldn't you use a 12AT7 or a 12BH7 they are far more capable as a cathode follower than 12AX7?

[mhartman]

Why wouldn't you use a 12AT7 or a 12BH7 they are far more capable as a cathode follower than 12AX7?

You could definitely use another tube. I went with the 12ax7 to follow dumble's design.

[phsyconoodler]

The CF configuration is a bit scary with the large voltage potential between the plate and the cathode, but I guess the 12AX7 CF runs fine with it, what's your experience? It does not shorten the life of the tube, does it?

Mesa Boogie amps have high cathode voltages in cathode follower positions and russian tubes and many NOS tubes can't take it for long.They recommend JJ style 12AX7's or select Chinese 12AX7's. As a former Mesa warranty tech I have to agree.