SLO 100 tube head modification!

 

 This nice SLO 100 tube amp head was hand built by Brit Tone amplifiers UK. It's a Soldano SLO 100 replica made using high quality components.
  Here are the SLO(Super Lead Overdrive) 100 specs and manual:
http://www.audiotek.cz/produktyGTA/soldano/SLO100_p1.pdf

Brit Tone amps UK:
http://brit-tone.com/services


Mods:

Less gain? What?!..
 This all tube amp head is such a gain monster that the owner asked for a bit less gain on the OD channels... The gain knob was responding quite well until you set it past 12 o clock were the amp started to sound muffled and muddy. The brightness and detail were buried under tones of gain, fuzziness and low end. So we modified the OD preamp channel for less gain. I replaced the grid resistor in the 1st half 12ax7 OD gain stage with a (470K-4,7nF)R-C series network to reduce gain and bass fuzzy frequencies. That worked well but I added a 250k resistor in parallel with the Gain pot outer lugs to reduce gain ever further. The result was a usable gain pot range. Now, you can crank the gain up without getting feedback, fuzzy notes and muddy tone.

The fx loop mod:

 The fx loop on this amp was fiddled with so it sounded weak and funny. It turned out the fx loop send/return jacks were busted and I had to replace them with new heavies duty ones. The fx loop sounded okay but there was a difference in level and tone with effects plugged in the send and return jacks. The SLO schematic provides a note about the fx loop and so I tried this particular mod pictured here:
http://www.ampbooks.com/home/classic-circuits/soldano-slo-preamp-1/soldano-SLO-schematic.jpg
The added 1K and 25uF components fixed the fx loop level and tone issues and the amp was ready for a bias adjustment!

Bias
 Setting the bias on this SLO replica was easy as there was a set of bias connectors available on the back of the metal chassis.

 The amp sounds pretty good now and it's got a nice working fx loop plus a usable gain range. The tone is really good after these mods and the amp is a proper hard rock monster that can produce interesting clean and crunch tones as well!

Here a few pictures of the amp: