Lowering voltage on preamp plates for fatter sound

[Chuck H]

Enzo was the first I heard use the term "decoupling capacitors". And by that he means that the capacitors in the preamp end of the power rail serve as ground for AC in the power supply to eliminate small feedback loops that can interfere with amplification. The first capacitors in the rail serve also, and primarily as reservoirs to smooth and filter ripple from the main DC source (ergo "filter caps"). Now, all the caps in the rail decouple AND filter, but the priority of those two functions shifts as the power rail moves from the power amp toward the preamp.

This is how the capacitors constitute a "node". Each power point needs to be "filtered" and it's the capacitor that facilitates that. The resistors serve to drop voltage AND allow separation between the nodes for more effective filtering.

That's the best I can do with my low tech understanding.

[pdf64]

I think that 'reservoir cap' is usually and best used to refer to the 1st cap after the rectifier; as it acts as a reservoir that keeps the voltage up between the lumps of dc that the rectifier puts out.
It's that action which raises the average Vdc to the peak Vac.

[balokker]

I got a thicker crunchier tone replacing one of the 365s with 42k in total (spread over three 2 watt resistors). As I went up in total R it got better until I got past 47k, dropping C to 142v which was too dark and lifeless. Right now it sounds real good with 184v on node C.

[balokker]

Question: in the stock circuit it shows 450v at node A and 412v at node C, with ten 365 ohm 1/2 watt resistors and one 220 ohm resistor in between. So it's a 38 volt drop over these 11 resistors? (approx .37 watts per)

Reason being, I noticed the 365s got pretty hot in my modded set up. I didn't check them before the mod. Is it normal for these dropping resistors to get fairly hot?

[Chuck H]

Not being sure exactly what's on each node makes it hard to suggest which node is good to target or any criteria for good, minimum operating voltage. For example, including the PI in the voltage drop may actually cause it to clip BEFORE the power tubes and reduce amplifier output and any ability to achieve power tube clipping. See? So, there's that. But there's no danger to amplifier by doing that, so, if it sounds good and performs to your satisfaction...

Yes, those resistors make a lot of heat. They were doing that before your modification. You haven't done anything to cause the heat.