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previous: Nick Will PT handle increased fillam... -- 6/29/2000 1:08 PM

Re: Bluesmaker mod in my SF Bassman 50

6/30/2000 3:28 PM
Carl Z	Re: Bluesmaker mod in my SF Bassman 50 Nick; I've done the mod and it's basically just a hotrodded 2204 circuit. The low gain setting sucks! It's too damn clean. As for the transformer, the heater windings are only rated at 4 amps so using EL34's put's it right at the margin from a reliability standpoint. Actually you're over but those trannies are tough as nails, so you can get away with it if you've got a good transformer that hasn't been abused. A better alternative is to get a replacement transformer for a super reverb. This will give you a little breathing room if you're dead set on using EL34's. I've cooked up more than a few tweaks for this circuit as some of the potential has been missed and other things were overkill. Note that most any mods for the Marshall 2203/2204 amps will work well with this circuit. Here's a few things that you might want to consider changing... 1) lose the capacitor network that he's using for the mid boost. Replace it with a more standard circuit. As designed it removes the hairyness in the high gain settings but gives a somewhat compressed quality to the amp that you may or may not like. 2) replace that mix control with a switch so you can run in low or high gain mode. 3) use that dormant preamp stage as a mixer for a passive series effects loop. Use the second set of unused inputs for the send and return. Build it first as designed and then start tweaking to taste. Carl Z

6/30/2000 3:28 PM

Carl Z

Re: Bluesmaker mod in my SF Bassman 50

Nick;

I've done the mod and it's basically just a hotrodded 2204 circuit. The low gain setting sucks! It's too damn clean.

As for the transformer, the heater windings are only rated at 4 amps so using EL34's put's it right at the margin from a reliability standpoint. Actually you're over but those trannies are tough as nails, so you can get away with it if you've got a good transformer that hasn't been abused. A better alternative is to get a replacement transformer for a super reverb. This will give you a little breathing room if you're dead set on using EL34's.

I've cooked up more than a few tweaks for this circuit as some of the potential has been missed and other things were overkill. Note that most any mods for the Marshall 2203/2204 amps will work well with this circuit. Here's a few things that you might want to consider changing...

1) lose the capacitor network that he's using for the mid boost. Replace it with a more standard circuit. As designed it removes the hairyness in the high gain settings but gives a somewhat compressed quality to the amp that you may or may not like.

2) replace that mix control with a switch so you can run in low or high gain mode.

3) use that dormant preamp stage as a mixer for a passive series effects loop. Use the second set of unused inputs for the send and return.

Build it first as designed and then start tweaking to taste.

Carl Z