The Amp Garage

Is there a technical reason that grid stoppers used on the power tubes tend to be on the order of a few k vs preamps that often use up to 470k? And what is the largest you've seen? 10k is the biggest i saw looking thru a few dozen schematics.

I'll see what values i have laying around and try for around 3k. Thank you.

on a side note, If the amp's output section feels rather stiff even with small filters, i think larger screen resistors will soften that, right? What would be considered the largest value to use in a marshall 50 watt that you think would be considered within reason? I use 1k now.

el34 50w

Well, that was easy. At max volume with a 1k .1vac tone at max volume the bias jumped to around 200mv. So i guess it's good to go. Thanks much for the info.

Very simple, Thanks ! I already have 1R test points on each cathode as dual bias so i'm good to go. I'll give that a shot in a few, thanks...

tubeswell wrote:Have you tested (i.e. measured) the Pri:Sec VAC ratio?

How would i do that?

Oh, and the title was supposed to be "slightly", not "lightly".

In other words, can they seem to work fine but not be working at thier optimum due to a defect of some sort ? Is there any way to check them to be sure they are 100%?

This ringing you speak of, does it sound like an acoustic guitar ringing like if you hit a chord with the amp loud and a acoustic in a stand in front of the speaker? I've heard that when cranked under certain circumstances. Does the choke's H value affect the tone when the amp is loud ? If it does h...

Does the choke's H value affect the tone when the amp is loud ? If it does how would you say very large values like say a 20H would sound or feel compared to a 5H?

No bright cap, but thats good to know. I've messed with the gain pot like this too and never thought about that. It has a cap.

I guess i am using the word load wrongly, but i always figured that mean resistance to ground. Anyways, i will try that again today also.

EDIT: I see what you mean now.

I didn't realize you could do that without changing the bias to a degree that wouldn't be good. I don't care about driving the power section into OD since i never use it for anything more than small stage volume. But I will definitely try that today, thanks.

Ok, yes, thats what i have tried and it does change the tone because it halfs the load. let me just ask this....if i did what I first suggested, will that also half the load? The load part of a set VD is also 1M to ground, but it's separated from the pot's load unless the pot is maxed. Come to think...

If by the formulas you mean 1M = 1M in parallel=500k or 1M = 1M in series =2M, i get that. Thats not what i meant by can't wrap my head around it. But as for martin's suggestion, as i said in the edit in my last post, it wasn't clear to me what he was suggesting.