Blackfacing a Silverface

racehorse · April 24th, 2004, 08:11 PM

I need some good advice,from some of your personal experiance.

I have an early 70`s vibrosonic, basicly a TR with 1/15.
It has a master volume ,but no pull boost.
I have had it since it was new, it needs a cap job.

the MV iI never used , always kept on 10.

If I remove this from the circuit , what sound differance will I here?

the other BF mods etc.

PI changes

voltege changes

The bias change is going to happen , I may just add a bias vari to the bias balance. seems like a good idea.

but what audible differance`s will I hear , or am I suposed to hear ?BF vs SF?

nothing I do will be irreversable .

HELP
Thanks
Racehorse

Stan Martin · April 29th, 2004, 08:32 AM

your amp wil have a better livelier feel. less constricted especially when you change the PI circuit. those 2 330k resistors dampen way too much.
clip off those tiny suppresssor caps that may be connected to the power tubes to ground. they will kill off high end. disconnecting the MV is no big deal tone wise. most guys do it just because.

racehorse · April 29th, 2004, 05:37 PM

Thanks Stan, that is just the kind of info I needed.
I feel the need to BF this amp but wanted to make sure I`m not caught in the Hype of the day.

Because the amp sounds pretty good as is.
I am going to do the hole BF mod.though.

Thanks again
Racehorse

AtomicMassUnit · April 30th, 2004, 01:08 AM

Racehorse,
Techs have been blackfacing those amps since the early 70's. I just got done with a Vibrasonic, and it's a nice sounding amp. The weak point in the one I worked on was the speaker and power tubes being very tired, but the BFing really added a lot more life to it. Blackfacing it will give you a much richer tone overall. Pay close attention to the PI, I really think this is one of the most important sections in the amp for getting the sound you want. A lot of people prefer putting a pair of .047s in the PI where the .1s are. This takes a little bit of mud out of the low end. See if you like it. Also, I wouldn't worry about adding a Level bias to the bias Balance, because matched tubes are so easy to come by these days. Just convert it to a level bias, and use matched tubes. The Master volume will still rob a little bit of signal when it's all the way up. It's best to disconnect it, if you're trying to get that last little Nth degree of tone out of it. But hey, that's why we use these things, right? Email me if you need anything..

Atomic

April 24th, 2004, 08:11 PM	#1 (permalink)
racehorse Tele-Meister Join Date: Apr 2003 Posts: 144	Blackfacing a Silverface I need some good advice,from some of your personal experiance. I have an early 70`s vibrosonic, basicly a TR with 1/15. It has a master volume ,but no pull boost. I have had it since it was new, it needs a cap job. the MV iI never used , always kept on 10. If I remove this from the circuit , what sound differance will I here? the other BF mods etc. PI changes voltege changes The bias change is going to happen , I may just add a bias vari to the bias balance. seems like a good idea. but what audible differance`s will I hear , or am I suposed to hear ?BF vs SF? nothing I do will be irreversable . HELP Thanks Racehorse

April 29th, 2004, 08:32 AM	#2 (permalink)
Stan Martin Tele-Holic Join Date: Mar 2003 Location: Pepperell Posts: 818	differences your amp wil have a better livelier feel. less constricted especially when you change the PI circuit. those 2 330k resistors dampen way too much. clip off those tiny suppresssor caps that may be connected to the power tubes to ground. they will kill off high end. disconnecting the MV is no big deal tone wise. most guys do it just because.

April 29th, 2004, 05:37 PM	#3 (permalink)
racehorse Tele-Meister Join Date: Apr 2003 Posts: 144	thanks Thanks Stan, that is just the kind of info I needed. I feel the need to BF this amp but wanted to make sure I`m not caught in the Hype of the day. Because the amp sounds pretty good as is. I am going to do the hole BF mod.though. Thanks again Racehorse

April 30th, 2004, 01:08 AM	#4 (permalink)
AtomicMassUnit Tele-Meister Join Date: Apr 2003 Posts: 153	Racehorse, Techs have been blackfacing those amps since the early 70's. I just got done with a Vibrasonic, and it's a nice sounding amp. The weak point in the one I worked on was the speaker and power tubes being very tired, but the BFing really added a lot more life to it. Blackfacing it will give you a much richer tone overall. Pay close attention to the PI, I really think this is one of the most important sections in the amp for getting the sound you want. A lot of people prefer putting a pair of .047s in the PI where the .1s are. This takes a little bit of mud out of the low end. See if you like it. Also, I wouldn't worry about adding a Level bias to the bias Balance, because matched tubes are so easy to come by these days. Just convert it to a level bias, and use matched tubes. The Master volume will still rob a little bit of signal when it's all the way up. It's best to disconnect it, if you're trying to get that last little Nth degree of tone out of it. But hey, that's why we use these things, right? Email me if you need anything.. Atomic