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dumble mod question


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4/6/2005 2:06 PM
regis dumble mod question
In this mod there is a .05uf cap on pin 6 of the first preamp tube. Is this an electrolytic? It looks like it but mouser doesnt have a .05uf elec.  
 
https://schematicheavencom.secure.powweb.com/rumbleamps/mod1.pdf  
 
by the way, has anyone done this mod on a fender? How does it sound?
 
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4/6/2005 8:30 PM
regis
anybody??
 
4/7/2005 5:36 PM
Daver

It's not an electrolytic. Any film cap rated at 400v+ should work fine. As far as the tone goes, I've never used it all by itself, but would say it provides a more refined, hi fi tone. Like most stuff, you have to try it for yourself to really tell. It's worth experimenting with. Also, using different values of the series resistor will change the tone and gain. The smaller the resistor the less gain. Try it out!  
Daver
 
4/8/2005 6:05 AM
regis
Thanks Dave, I have a Bassman 100 I am going to try it in.
 
4/12/2005 3:01 AM
Steve A.

regis:  
 
    A 0.047uF/630vdc poly cap will work here. You might experiment with the 22Meg value, adding 11Meg resistors in series to get 33Meg or 44Meg.  
 
    I think the mod is as slick as bat sh*t, but let me know what you think. If you do it to the Normal channel be sure to add reverb to it since it works really well with reverb. (I recommend ALL of the bells and whistles: rock/jazz switch, deep switch, mid boost.)  
 
Steve Ahola
 
4/13/2005 10:42 AM
regis
thanks steve, I'll let you know how it turns out.
 
9/3/2005 8:18 PM
Dr Rico

Hola Steve, long time no see!  
 
RE: Dumble mod. I have an old Precision PA head here that has been rebuilt as a 5E5 more or less. The Dumble mod on this one uses a 44meg resistor in series with a .100 cap (selected after stepping up from .047 until it pleased the ear). The mod dropped the top some, but clean tones are much fatter and it suits the amp well.  
 
Hasta --> Rico
 

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