Pull Boost Master on 79'TwinReverb???

CsaRvoX

CsaRvoX

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My 79' Silverface Twin Reverb has push/pull master volume...I know it boosts the signal to power tubes and I use it everytime I play but is there a drawback in this?Also if you could help me about the basics of this master volume boost process...what I hear actually is not a volume boost really but bringing the guitar tone forward and reducing the reverb...its kinda like swapping the actual guitar tone with the reverb...but I like it better cause I can still crank the reverb and get both...I always use it with master pulled...it seems to lose its fullness when it is pushed...anyway I'm curious :) if you could enlighten me in this matter I'd be much grateful thanks everyone...
 
Re: Pull Boost Master on 79'TwinReverb???

CsaRvoX said:
My 79' Silverface Twin Reverb has push/pull master volume...I know it boosts the signal to power tubes and I use it everytime I play but is there a drawback in this?Also if you could help me about the basics of this master volume boost process...what I hear actually is not a volume boost really but bringing the guitar tone forward and reducing the reverb...its kinda like swapping the actual guitar tone with the reverb...but I like it better cause I can still crank the reverb and get both...I always use it with master pulled...it seems to lose its fullness when it is pushed...anyway I'm curious :) if you could enlighten me in this matter I'd be much grateful thanks everyone...
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It's been a while since I've looked at a schematic that had one;However the basic idea IIRC was that it tapped off the reverb driver stage (more gain) through a capacitor which created more of a treble boost effect (most people thought it a bit to nosebleedy). When you pull it you add in a louder *dry* signal (which is probably why you hear the guitar get louder, but not the reverb) signal after the reverb). It drives the amp a bit harder, and also provides a bit of volume boost. If the cap value is made larger, then it rolls off less low end, and creates more of an even volume/gain boost. I think there is also a resistor or two there to knock down the voltage to get a preset level of boost. The fullness you speak of is probably do to the fact that it does somewhat increase some of your mids (as Fenders are rather weak in that area), and does increase the level of availble overdrive to the following stages. I'm sure there were changes over a few years, but that's the short of it.
 
Re: Pull Boost Master on 79'TwinReverb???

Great reply Kent thanks...that's the exact situation my ears catch ;)...Well I don't know much about technics but at least I can judge with my ears...well it sounds great to me,I don't complain about the treble nosebleed issue cause I'm used to it,my guitar is also fender with maple fingerboard and as you can see I really like treble much :)...anyways I could still roll off excess treble via tone control so no problem there...you're right boost seems like extra tone controls upped like treble,mids,little bit low-end...it also gets hotter on power tubes which is a good thing to get the best tone...its always on for me as long as power tubes stay thanks you :)
 
Re: Pull Boost Master on 79'TwinReverb???

That was a great reply from Kent. I've removed that master volume in several late 70's Twin Reverbs and just eliminated it. IMO, the amps sound better without it. In one amp I replaced that master volume with a variable negative feedback control...it didn't have alot of range but it was useful. In another I made it a prescence control (very similar to a variable negative feedback control) and found that useful too. Lew
 
Re: Pull Boost Master on 79'TwinReverb???

Lewguitar said:
That was a great reply from Kent. I've removed that master volume in several late 70's Twin Reverbs and just eliminated it. IMO, the amps sound better without it. In one amp I replaced that master volume with a variable negative feedback control...it didn't have alot of range but it was useful. In another I made it a prescence control (very similar to a variable negative feedback control) and found that useful too. Lew
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Hi Lew...When you removed the master volume in which mode does it stay pulled or pushed?Also I don't use the preamp volume it just stays at 2 in order to get sound from power tubes...I'm running pedals through input combined with the pulled master volume cranked to get power tubes working efficiently...well I've tried the other ways like keeping master low and pushing preamp volume but sounded like ordinary transistor amps cause power tubes are not in action...I've experimented both with 5 to 5 but that was also not enough...the best sound I get is with cranking the master and keeping preamp low...
 
Re: Pull Boost Master on 79'TwinReverb???

When you remove the master volume it makes the amp like a blackface non-master volume Fender. So no boost. Thanks! Lew
 
Re: Pull Boost Master on 79'TwinReverb???

Lewguitar said:
When you remove the master volume it makes the amp like a blackface non-master volume Fender. So no boost. Thanks! Lew
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question- i have a customer that just acquired a sf 100w mv. for some un godly reason he wants it restored original.the previous owner had it blackfaced.P.I. resistors,cap job,removed hook up wires to mv and pull boost,removed boost components from the board.nice touch there.the only layout diagram i can find is for a 74.some values get really screwy around V4.if you examine just about any other 70's 100w twin w/mv you'll find a 12k resistor attached to pin 6 of V4. the only layout i could find. which is the 74 shows a 300k.if you or anyone else happens to have some nice intelligible close ups of this circuit or even an earlier layout i would be in your debt if you could share.i believe i can solve the mv circuit.also...the area of the board the components are missing from is right above or below ,depending on your perspective,V4. as close as I can get to an actual year is the date codes on the pots which indicate 73
thanks
 
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