Bassdude V1 cathode resistor question

G

Gritdog

New member
I was doing some analysis of the Bassdude/bassman schematic for an upcoming build. This article (https://www.ampbooks.com/mobile/classic-circuits/fender-bassman-5F6-A/) says that the 820ohm V1 cathode resistor is shared across two triodes, which means that if you’re building a one channel amp you would double it to 1.64k (unless you joined the two cathode pins, which I saw is possible in this thread: https://www.tdpri.com/threads/bassman-micro-v1-cathode-resistor.1115674/).

The bassdude keeps the original 820ohm value - does this mean the cathode pins are joined or should I increase this value to ~1.5ish to more closely reflect the amp?

Thanks!
 
Bassdude is based on the 5D6 Bassman, which does indeed have a shared cathode connection across two triodes, but since each triode acts as an input stage for the respective channel you're only using one at a time, which made me think the 820Ω cathode resistor for V1A was fine for Bassdude. Realistically though, I wouldn't expect you to notice any difference at all if you were to try a 1.5kΩ resistor there either. Cathode resistor value becomes much less important (assuming you stay within a degree of magnitude) when the cathode is bypassed like it is here.
 
I think that since you are only connecting one triode you should really use a 1K6 resistor and a 120uF capacitor, that way the voltage drop across the resistor stays the same as the original.
I also doubt you would notice any difference whichever way you do it, if you really want to be correct then do it but then you should also use 12AY7 tubes like the original 5D6-A schematic, but this could cause a large loss of gain in the pedal and reduce the output signal.
I used a 820R resistor and a 220uF cap in my build with 12AX7 tubes.

T

Post in thread 'The MOD Squad'

The next mod I am going to show is more about what can be done to the BassDude, I think I only placed the Bright cap on a switch on my first BassDude.
When we look at the Bassdude it becomes obvious it is a copy of an earlier Bassman, the Bassman 5D6-A and the 5E6 both match the BassDude schematic.
The first thing that stands out to me is that we only have one input but the original had two inputs with a common Cathode resistor and capacitor,
since we are only supplying one triode we should really double the resistance of R16 to 1k6 and halve the capacitance of C8 to 120uF.
When I run the...
 
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