Which circuit do you guys prefer?

[M Fowler]

When you guys build JCM800 50w clones which presence pot circuit do you like best 5KL or 25KL?

[Roe]

5k

[martin manning]

Seconded. 5k.

[M Fowler]

Thanks guys I will install the 5kL.

[Reeltarded]

yeah yeah my amps are basically sort of 800s with plexi Pres.. the 25k circuit is weak and meh

[pompeiisneaks]

yeah yeah my amps are basically sort of 800s with plexi Pres.. the 25k circuit is weak and meh

I swear I read and/or heard that the 25k is poorly designed because the way the circuit works, it can only use the first 4 or 5 k anyway and the rest is wasted, no?

~Phil

[Reeltarded]

You turn the knob and if you don't hear DC scratch, you won't hear any real change at all. The early one does too much and too little. That's perfect.

The 25k is a waste of a control, a hole, the components..

[RockinRocket]

Pompi and Reel you've lost me.

Alberto did a amazing job analyzing the frequency sweep on my questions of the differences between the two.
They are more or less the same in frequency. No DC scratch on the 25k but the actual sweep in the 25k does not react Linearly like the 5k pot setup.

[FourT6and2]

What about the 5K pot plus the 4K7 resistor like in the 25K pot version? I have an amp here that came with that and it surprised me to see that.

[RockinRocket]

What about the 5K pot plus the 4K7 resistor like in the 25K pot version? I have an amp here that came with that and it surprised me to see that.

It works but you have half the range as a 25k pot 4k7 circuit.
5k/no reistor has the largest frequance range of the circuits.

What ampin question?

[V2]

I prefer the 5k too. I just don't like the sweep of the 25kB (with || 4k7 R) pot.

[FourT6and2]

What about the 5K pot plus the 4K7 resistor like in the 25K pot version? I have an amp here that came with that and it surprised me to see that.

It works but you have half the range as a 25k pot 4k7 circuit.
5k/no reistor has the largest frequance range of the circuits.

What ampin question?

Interesting, thanks. The 4K7 resistor is there to block DC, right? But it also changes the sweep/frequency range of the pot?

[RockinRocket]

Correct. The frequency range is more or less the same but the sweep is very bunched between 1-5 and then very spread out. So its not linearly even though the pot is linearly.

I believe the difference is because the cap on the pot is wired differently. Joins from the wiper to a end.

[sluckey]

... The 4K7 resistor is there to block DC, right?

No, resistors do not block DC. The 4K7 provides a dc current path for the PI cathodes.

[FourT6and2]

... The 4K7 resistor is there to block DC, right?

No, resistors do not block DC. The 4K7 provides a dc current path for the PI cathodes.

Thus keeping DC off the pot?