Steel String Singer questions

[Svempan]

Hello,

I’m new on this forum. Maybe this has been talked about many times before, but I post my question to see if I get any interesting answers.

Most people seem to be interested in the Over Drive Special but this question is about the Steel String Singer.

A couple of months ago I modified one of my own Fender Amps. My purpose was to try the Dumble type tone circuit (as in the 70’s ODS schematic of Schematic Heaven) and 6550 as output tubes. From the beginning the amp is a 1972 Fender Bandmaster Reverb, but since several years it has been modified to a 3x10 combo (the output transformer is from a Blackface Super Reverb).

Here’s how I now modified it:
- Tone circuit as in the 70’s ODS schematic of Schematic Heaven. I included both Jazz/Rock, Bright and Deep switches. The Bright switch has a 47 pF capacitor though.
- The circuit around the tube stages on both sides of the tone circuit, also as on the 70’s ODS schematic.
- First pre amp tube is GE 5751.
- Standard Fender Blackface reverb circuit.
- Output tubes are GE 6550.
- Phase inverter circuit is like standard Fender Blackface type long tail pair, but the input coupling capacitor is 0.01 uF, the tail resistor is 10 kohms and the phase inverter tube is a 12AU7 (Philips ECG JAN 6189)
- Presence control circuit is very similar to the 90’s ODS schematic of Schematic Heaven.
- The rectifier is solid state diodes (FREDs).

I wanted to try the 6550 because I had tried some hefty bass amps with that, which I really liked... for guitar...

The Dumble tone and pre amp tube circuits, I wanted to try just for curiosity...

My God! Was I positively surprised? I have now giged and rehearsed several times with the amp and I really like it. Right now I use it together with a Blackface Fender Vibrolux Reverb (the two amps sound rather different).

I also discovered that the sound of the Dumbleified Bandmaster is very much like the sound that Stevie Ray Vaughan has on the DVD from Montreaux 1985. At least as I hear it. That made me more interested in the Steel String Singer.

Although I like the sound of the amp like it is, it would be nice to know what the two tone filter controls found on the front panel does. Some information says they are six step rotaryswitch high and low frequency shelving filters. Does anybody here know more exactly what they are and what they do? Comments?

Maybe some of the Steel String Singers had cathode follower circuits as phase inverter or between the phase inverter and output tubes. That's probably a good idea if low distortion is the goal. I don’t play extremely loud though, so I don’t think that’s necessary... Comments?

Some information says there are EF86 tubes in the preamps of some Steel String Singers. That sounds interesting. I like the sound of EF86. Comments?

Take care,

Svempan

[heisthl]

All good questions, I'm also curious about the SSS and have heard it's more of a bass amp, specifically a showman preamp into a SVT or Model T type output or is that the wonderland? In any case, I would like to hear from someone who actually knows something for sure, even if it's just what tube types were used. There is another type of output section that would appear like a cathode follower at first glance but isn't (see picture below) and unless someone has actually traced the circuit could be easily mistaken for one.

[johan]

Welcome Svempan!
You've come to the right place!
Maybe you can help me out here https://tubeamparchive.com/viewtopic.php?p=20253
Good luck with your amp.