The Amp Garage

I've never seen it, but I'm just a hobbyist and haven't strayed far from Fender, Marshall, Ampeg, and Vox designs. Maybe you could post the schematic of the amp you have with this configuration. It's just a 2204 clone with a Jose master volume mod. But it has a 4K7 tied to the 5K L presence pot. An...

Ah ok, got it thanks!

Still, it's kind of abnormal to see a presence circuit with a 5K pot and 4K7 resistor, no?

That's it, Roe.. same here. I like 220k plate with 220k to 270k divider. So the higher plate resistor puts more voltage on the stage, decreasing a bit of gain. And a 220K/220K divider to V1b grid also reduces gain? Keep in mind I'm not going for a Van Halen or '80s sound here. More like '90s hard r...

its too gainy for me with 320k anode resistor and a 68k/68k voltage divider. Also there is a fair amount of hiss Interesting. I've gone up to 470K plate load. Doesn't seem that different from 330K to be honest. I can try 220K of course. What about what I have in parenthesis with an 82K off the gain...

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. This isn't my experience. 5K pot with 4K7 to ground and the sweep is not bunched up at all. It actually seems to be more spr...

sluckey wrote: ↑Wed Aug 22, 2018 4:19 pm

FourT6and2 wrote:... 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?

Have you ever played through a Randall RG 80/100/120? That whole amp is about the N914. It's thumpy and flat/dry and LOTS of reduction. (umm.. 5v?) They look like honey bees made of glass.. a plus. They are about as freaking clippy as anything could ever be. (err.. bee) Commonly, I will engage the ...

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? Interes...

sluckey wrote: ↑Tue Aug 21, 2018 6:49 pm

100v zeners?

A 1N914 is not a 100V Zener. It's a small signal diode with a 100V PIV rating.

Oh you're right! I glanced at the data sheet too quickly. How do these compare to a pair of zeners? Why use one over the other?

You might find that you don't need such a high first plate even though you are trying to squeeze the gain out there. I've built a few similar amps as well and I think I've never gone lower than 330K plate load. I started super high, at like 470K and worked my way down lol. I think that 5kp over the...

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.

I've built a bunch of Jose-style builds. All of them slightly different. Put this schematic together for another one but I'm going back and forth on some voicing options. Any thoughts? V1a plate will probably be 330K or 390K. Not a huge difference either way (I've tried both in the past). Clipping/c...

Are the other amps you mentioned that are quiet really identical to this one? It's hard to believe the same problem wouldn't appear with that remote ground. I see that the C-tone layout shows it that way. Does this amp follow that layout exactly? They are all the same circuit. Some slight voicing c...

Great! Where did you ground the pot that is on V2B's grid? Kept it in the same place—grounded locally at that standoff. Ideally, I guess I should move that to the bus bar too. I might just throw a 470K resistor on the board to replace the pot at some point. The amp does sound a bit different. Not s...

Grounding gain 2 eliminates any noise coming from upstream of that point. Here's a picture. Does this sum it up at this point? I would want to associate the grounds as shown by the dashed lines. Yeah, that makes sense. :) But... I've fixed it! :D A new standoff at V1b, with an isolated lug for that...