Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Brownie on June 04, 2026, 11:44:36 am
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Can anyone reveal the ways the various values of mixing resistors behave in the circuit? This early Traynor had 100K ones, but I substituted 270K ones, split the V1 cathodes and put a bunch of Marshall values into it for buddy client. That amp is finished and now I'm doing up my 5f2/5f3 Frankenbeastie with a stacked tone pot. What should I choose for those mixing resistors? Maybe I'll use 220K like on a Fender AB763
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Everything is a filter (especially when adding caps in parallel with the mix resistors) and everything is a voltage divider.
While the divider ratio is the same between these, the overall resistance (impedance if the coupling cap is small enough) to AC ground is significantly different between the different values. You'll need to trace the circuit back through the coupling cap and plate resistor to HT, then parallel that with the functional triode residence to get a good calculation
As to how they'll behave, that depends a lot on the other values in the circuit. In general, you'll have marginally more signal the higher you go, but there's also a voltage drop across the first mixing resistor, so there is a ceiling. There are also noise considerations as higher resistances are inherently noisier.
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Thanks for that. I guess I'll have to set up my board in order to make it easy to try various pairs of resistors. Then I can hear for myself
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So what is a 5f3? Do you mean 5e3? Either way, it would be interesting to see what you come up with.
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I was supposed to edit my post but I missed that error. It's a 5E3 shoehorned into a 5F2 chassis. A single input jack,2 volumes, master and a stacked tone pot. I was just supposed to make a Harvard out of it in the first place, but it'll work eventually...
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There are no mixing resistors in a stock 5E3. The two volume pots act as mixers.
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The mixing resistors are in the grid circuit, do as their value increases, the Miller capacitance LPF corner frequency decreases.
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The mixing resistors are in the grid circuit, do as their value increases, the Miller capacitance LPF corner frequency decreases.
Are you maybe thinking about the two 68Ks for the HIGH and LOW input jacks?
As for mixing the two channels together... There are no mixing resistors in a stock 5E3. The two volume pots act as mixers.
https://el34world.com/charts/Schematics/files/Fender/Fender_deluxe_5e3.pdf
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my 8th grade English-comp understanding of the OP;
"Can anyone reveal the ways the various values of mixing resistors behave in the circuit? This early Traynor had 100K ones
"That amp is finished and now I'm doing up my 5f2/5f3 Frankenbeastie with a stacked tone pot. What should I choose for those mixing resistors? Maybe I'll use 220K like on a Fender AB763
maybe OP's schematic might clear up the english??