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Matchless tone stack question


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6/3/2004 1:08 PM
Bob DeRosa Matchless tone stack question
The tone controls for the ef86 channel consists of a six position switch that selects between various values of capacitors ranging from .0036uf thru .01uf. There are 5M1 resistors across the contacts of the six position switch.  
 
I don’t seem to be getting much of a change in tone as I rotate the six position switch. Is this normal for this circuit ?  
 
What’s the purpose of the 5M1 resistors ? It seems like I could just remove them and the switch would isolate the different paths…
 
6/3/2004 2:41 PM
two tone
You´re using wrong values,the smallest cap is 360p/.00036mf,the difference in tone is very audible,those 5M1 resistors prevent a ´pop´when you switch
 
6/3/2004 5:04 PM
Bob DeRosa
That was a typo on my part, I'm using 360pf up to .01mf.  
 
I'm not getting much (if any) difference though.  
 
Maybe I need to measure the capacitance from the "upstream" side of the caps to the "downstream" side of the switch at different positions to verify that the coupling capacitance is actually changing...
 
6/3/2004 5:16 PM
Mark Lavelle

IIRC, it's a "bottom cut" control - do your guitar, OT & speaker have enough bottom for it to make much difference?  
 
If you're not building a clone, are you reducing the bass (compared to the original circuit) anywhere else in the signal path?
 
6/3/2004 6:09 PM
Bob DeRosa
Hi Mark,  
 
As far as guitars, I play a Strat (Lindy Fralin Blues) and a Les Paul (PAF's) so I don't suspect them.  
 
The speakers cab is a 2x12 open back loaded with a Weber Alnico Blue Dog and a ceramic Silver Bell - I don't suspect that either.  
 
The amp is an HC-30 clone using original Matchless iron so it sounds like something's wrong. It's such a simple part of the circuit I can't imagine what's wrong but I'm going to fix it.  
 
FWIW, it sounds amazing right now (with whatever coupling capacitance it has). I played out with it last friday night and everyone was commenting on the tone. Two guitarists asked me if I sell amps !
 
6/3/2004 7:05 PM
two tone
Are you sure using 5M1 resistors,too low values may not isolate the caps from each other
 
6/3/2004 9:26 PM
Mark Lavelle

Well, I had to ask – partly because I'm pretty sure one of those tone controls is going into an amp I plan to build soon. Keep us posted on your progress, please!
quote:
"FWIW, it sounds amazing right now (with whatever coupling capacitance it has). I played out with it last friday night and everyone was commenting on the tone. Two guitarists asked me if I sell amps !"
Cool!
 

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