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Vintage threads from the first ten years

Re: Favourite Fender Master Volume Circuit

7/29/2000 12:48 AM
Peter S	Re: Favourite Fender Master Volume Circuit I'm with Rick on this....if you simply must have a master volume and you're using a blackface style circuit, a post PI master volume is definitely the way to go. If you are putting the master before the PI, then you will definitely need to add a gain stage and do some mods to the circuit in order to get a decent distortion sound. Otherwise you won't have any usable distortion at all. If you just want moderate distortion, forget the master volume and get a power attenuator. Peter S

7/29/2000 12:48 AM

Peter S

Re: Favourite Fender Master Volume Circuit

I'm with Rick on this....if you simply must have a master volume and you're using a blackface style circuit, a post PI master volume is definitely the way to go. If you are putting the master before the PI, then you will definitely need to add a gain stage and do some mods to the circuit in order to get a decent distortion sound. Otherwise you won't have any usable distortion at all. If you just want moderate distortion, forget the master volume and get a power attenuator.
Peter S

7/29/2000 10:46 AM
Dodge	Thanks Rick/Peter. I'll give that a whirl. There will not be any chassis drilling as there is a 1M Master pot in there already. That damn 70's master volume control sucks! I'll try the post-PI version as you kindly suggested and see what he thinks. Dodge

8/3/2000 2:26 AM
Trace	Have you tried putting a 250K dual ganged pot in place of the bias splitters? It sounds pretty darn good and very natural. When the pot is all the way up it's back to a stock non-master amp again. Hope it helps Trace

8/9/2000 4:55 PM

anonymous

quote:
"Have you tried putting a 250K dual ganged pot in place of the bias splitters? "

Trace-
It's a nice circuit.

If you use a 40% tapped 250k pot, there's a simple circuit you can implement to get a "loudness" contour as you turn down, so that your low and high end hang in a bit longer.... It's an impedance-transformed version of the old X100C Fisher volume control/loudness circuit.


 

 
hard-wired               or switchable
 

 
O-----+----+         O-----+--------+
 
IN    |    |         IN    |        |
 
      |    []          68p =        |      
 
  68p =    [] 250k         |        [] 250k
 
      |    []              O        []
 
      +----{]<---O   SPDT*   O---+--{]<---O
 
      |    []  OUT         O/    |  []  OUT
 
  47n =    []              |     |  []
 
      |    []              | 47n =  []
 
      []   |               |     |  |    Shown 
 
  10k []   |               +-----+  |  bypassed
 
      []   |               |        |
 
      |    |               []       |
 
      +----+           10k []       |
 
           |               []       |
 
           V GND           |        |
 
                           +--------+
 
                                    |
 
                                    V GND

C ya,
Dutch

8/9/2000 4:56 PM
dutch	Sorry 'bout the anonymous.... C ya, Dutch

7/29/2000 8:30 PM
Steve A.	Rick: On a Fender you could probably add a terminal strip held down by the eyelet board mount screw. A 5-lug terminal strip will work without attaching it to the Fender chassis (being held in place by the 4 coupling caps). Just bend over the mounting lug in the middle so that it doesn't short out against anything. (The middle lug is handy for attaching the shields from the cables going to the MV.) As you suggested the purpose of this MV in a stock Fender amp is to be able to reduce the stage volume a bit, while leaving the preamp volume pots at the settings you like. You don't get the massive distortion of a modern amp with the pre-gain set high and the post-gain set low (... thank God! ) --Thanks! Steve Ahola

7/29/2000 8:30 PM

Steve A.

Rick:

On a Fender you could probably add a terminal strip held down by the eyelet board mount screw.

A 5-lug terminal strip will work without attaching it to the Fender chassis (being held in place by the 4 coupling caps). Just bend over the mounting lug in the middle so that it doesn't short out against anything. (The middle lug is handy for attaching the shields from the cables going to the MV.)

As you suggested the purpose of this MV in a stock Fender amp is to be able to reduce the stage volume a bit, while leaving the preamp volume pots at the settings you like. You don't get the massive distortion of a modern amp with the pre-gain set high and the post-gain set low (... thank God!

)

--Thanks!

Steve Ahola

7/30/2000 3:50 AM
FredG	I agree with Steve - I've put the post-PI master in 3 Fender-style amps, and it sounds relatively natural at all volumes. Not a heavy, high gain sound - but great for blues and classic rock. Feel free to email if you'd like further info. Regards, Fred G.

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