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Vintage threads from the first ten years

previous: Steve A. Dan: &nb... -- 4/5/2000 3:26 AM

Re: Fixed to Cathode Bias Switch Mod

4/5/2000 5:04 PM
Dan	Re: Fixed to Cathode Bias Switch Mod Thanks to everyone who has responded. First off, I actually bought the BMR to turn into a Vibroclone. I would like to do the work myself. So, I tried to blackface the amp following Gerald Weber's instructions (Vintage approved mod). The amp now has really low output and distortion with two different sets of 6L6s. So, I'm waiting to order a SwAMP Probe so I can properly bias the amp. Then I'll try and figure out if crappy soldering in the phase inverter is at fault. Most of the mods I would like to attempt are fairly non-invasive; like disconnecting the NFB. Maybe experimenting with different resistor values or tone caps. I certainly won't be drilling holes in the chassis and front/rear faceplates. I agree with John S in warning about Torres style mods. The number of easily affordable, quality PTP amps (silverface) is only going to drop. Last year, when I first got interested in tube amps, I wound up at the Torres site. "Wow, I could get Marshall or Vox sounds out of my Fender Normal channel? Cool!" I now know that isn't really possible. If I really mess the thing up, I'll just take to Rick Erickson and have him make it right. Dan

4/5/2000 5:04 PM

Dan

Re: Fixed to Cathode Bias Switch Mod

Thanks to everyone who has responded.

First off, I actually bought the BMR to turn into a Vibroclone. I would like to do the work myself. So, I tried to blackface the amp following Gerald Weber's instructions (Vintage approved mod). The amp now has really low output and distortion with two different sets of 6L6s. So, I'm waiting to order a SwAMP Probe so I can properly bias the amp. Then I'll try and figure out if crappy soldering in the phase inverter is at fault.

Most of the mods I would like to attempt are fairly non-invasive; like disconnecting the NFB. Maybe experimenting with different resistor values or tone caps. I certainly won't be drilling holes in the chassis and front/rear faceplates.

I agree with John S in warning about Torres style mods. The number of easily affordable, quality PTP amps (silverface) is only going to drop. Last year, when I first got interested in tube amps, I wound up at the Torres site. "Wow, I could get Marshall or Vox sounds out of my Fender Normal channel? Cool!" I now know that isn't really possible.

If I really mess the thing up, I'll just take to Rick Erickson and have him make it right.

Dan

Replies:

steveR Another way to go if you want to ex... -- 4/5/2000 5:59 PM