SVT Style power amp with twin iron

[wawa]

Well I thought I would bump this thread as I'm starting to tackle this beast again after a long hiatus.

On my SSS build I'm using Twin iron with 4 6l6GC tubes as per twin.
What component changes are there vs the 6550 SVT schematic RJ posted earlier.

Also do I stay with the 12BH7 or 12AT7 driver, suggestions?

I was looking at the SUPER TWIN REVERB power schematic as well for ideas and values for the drivers. thoughts?

[wjdunham]

You may need to modify the trimmer and resistor values on the grids of the cathode follower stage. That network allows you to set the static bias current through the CF, which via the cathode resistor sets the grid bias for the power tubes. 6550 bias voltage being different from 6L6, you may not have enough range on the trimmer to set bias for the 6L6.
No opinions on the BH7 vs AT7.
Bill

[wjdunham]

You can also adjust the value of the -VBias at the bottom of the cathode follower cathode resistors to get the correct bias range as well.

[tictac]

I used the Super Twin circuit in my SSS type build. It's easier to implement than a direct coupled circuit because you don't need a separate power supply for the bias or a PT with a winding dedicated to high voltage biasing...

[talbany]

I've used the Super Twin CF.. No real magic there..IMO.. I would use the SVT and follow Bill's post..

Tony

[David Root]

Haven't got to the SSS yet, but it's coming, after a 183-type build.

However, depending on if you're looking to get the SRV SSS tone, I have heard that the 12BH7 is a necessary part of that, can't recall where I heard that but it's probably because SRV's amps were really Dumblelands with filters I think. I wouldn't be surprised if the direct coupled CF is part of that too.

Tony, you have any recall/intel on that?

[Chris333]

Never used a Super Twin power amp in a build, but I have a Super Twin, and I agree with Tony... no magic there. Of the power section topologies discussed for loud and clean around here, SVT, Marshall Major and Super Twin seem to come up from time to time. The Super Twin is probably the least desirable design of the three. A few years ago, I think a couple members built amps w/CFs for 4 6L6s or maybe 6550s, and from what I remember, there wasn't much advantage over a regular LTP...