Why did Warwick stop with 18V preamps in Thumbs?

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okay i found out randomly that my stage 2 has two batteries in it. How about that... wouldnt have known by hearing it :/
 

Florin

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Very keen to do this to my thumb, did you make space in the existing cavity or did it require routing?
I owned one that had a foamy cover for the battery. Like- thin foam and tape :) So the metal part of the battery will not touch anything there. And just place the battery above pots. It should be ok, and tight.
 
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I owned one that had a foamy cover for the battery. Like- thin foam and tape :) So the metal part of the battery will not touch anything there. And just place the battery above pots. It should be ok, and tight.

Florin, thanks so much for the expert input and if its that simple then consider it done! I play with loads of attack and by the sounds of things, 18v provides enough headroom to even things out?
 

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Hi Pablo, I have no idea. But you could easily try it and see the results, the mod is easy to do and totally reversible.
 
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Hi Pablo, I have no idea. But you could easily try it and see the results, the mod is easy to do and totally reversible.
Well I will let you know how it all goes down when I get the bass back from a set up next week. Will A / B with spectrum analyzer and post findings.
 
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Hi friends! I am from Russia, so I apologize for my English. I studied the power issues in the preamps at thumb 9 and 18 volts. In fact, in old preamps with 2 batteries, there is simply no way to put one, since the circuit is designed in such a way that the signal is amplified by default by 15 dB, and at the output it is reduced to the original value. Why was this done? Unfortunately, I don’t know, but it caused nonlinear distortions when amplifying frequencies, as well as amplifying the signal on the board. The 9 volt preamp does not have this drawback, and there is no such gain in the middle of the circuit. I can add that the frequency characteristics of these two preamps are different. To make the 9 volt version sound like the 18 volt version, you need to turn the treble control down to a minimum of "-". This gives you flat 18 volts.
 
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Here is a graph of the 18 volt preamp in flat mode.
 

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