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Re: stupid question ?

9/12/2003 1:41 PM
Bob DeRosa Re: stupid question ?
Hi Chris,  
A Tweed Mixer is a way to isolate channels in a multi channel amp. The idea is to input each channel into one of the the two grids of a tube that has a shared plate resistor. This isolates the channels without using mixing resistors. I did some experimenting with mixing resistors and I didn’t like the tonal tradeoffs that I had to make so I tried the “Tweed Mixer” and it works really nice. It can even add gain/distortion if that’s what you want. In my Marshall clone I don’t mind a little gain :) so I’m using a 12ax7 but in my Matchless DC30 clone I don’t want to add any gain so I’m going to try a 12au7 (low gain factor) in an effort to isolate as transparently as possible.  
FYI - The Tweed mixer is fully discussed in TUT1.  
Hope this helps
9/12/2003 3:45 PM
Chris ( CMW amps )

Bob : many thanks !  
Now I can talk with fellow amp-techs .....  
:) LOL :) ( just kidding ! )  
I used to call it a Pro 5E5 / Twin 5E8A / Hiwatt-mixer :) and I'm using it in bf & sf Fenders for putting reverb on both channels .  
I also did experience little or no tonal tradeoffs .  
Have a nice & rockin' weekend !  
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