I don't think the F4 will be perfect for low bias since the strength is more in the bottom end than the top end, and you'll not be able to drive the bass without distortion at a lower bias current. I ran my F4 at 80mA per transistor in the beginning and the bass was quite distorted.
A switch to change the bias is however very easy in this configuration and I don't think you even have to fear sparks, since you'll only need to switch the low current running through P1.
A switch to change the bias is however very easy in this configuration and I don't think you even have to fear sparks, since you'll only need to switch the low current running through P1.
Variac said:OTOTOTOTOTOTOT
you could also probably have a switch inside the box of the pumpkin to set gain from high to low? I mean not for background listening, but to make it work with other amps..
if I understood correctly that OTOTOTOTOTOT was for me
yup ;
relay/switch with two sections per channel- half ; one section for resistor side , one for lag cap side
so - two takamisawa double relays per channel ..........
naah - just play with input resistance ; that will be good enough .......
...... in that case one little takamisawa will be 'nuff for entire channel
Nah, the OTOT was for me because I was talking about the Pumpkin, but just a joke ,as how can you talk about the F4 without talking about
Pumpky every now and again...
So you are saying it's just as good to have a resistor you can switch in and out to increase the volume control resistance? Actually I was considering this to create more of a "two level" volume control to get more settings on the switched vol control, but there is always that risk that you have the resisistor switched in, then you increase the volume, then your little punk nephew runs over and magically decides to flip THAT switch...
(that's why I said "INSIDE the case.. ) ..
Pumpky every now and again...
So you are saying it's just as good to have a resistor you can switch in and out to increase the volume control resistance? Actually I was considering this to create more of a "two level" volume control to get more settings on the switched vol control, but there is always that risk that you have the resisistor switched in, then you increase the volume, then your little punk nephew runs over and magically decides to flip THAT switch...
(that's why I said "INSIDE the case.. ) ..
Variac said:Nah, the OTOT was for me because I was talking about the Pumpkin, but just a joke ,as how can you talk about the F4 without talking about
Pumpky every now and again...
So you are saying it's just as good to have a resistor you can switch in and out to increase the volume control resistance? Actually I was considering this to create more of a "two level" volume control to get more settings on the switched vol control, but there is always that risk that you have the resisistor switched in, then you increase the volume, then your little punk nephew runs over and magically decides to flip THAT switch...
I agree with every word ( can I say or do anything else , considering that I write these words to who else than
Pirate 
) , except that - point is that you make each one R1 and R3 switchable ; say - R1 is made of one fixed resistor , and other one which can be switched in parallel .
same as R3
so - there is nothing with pot , just varying NFB
