Another Wreck (almost) alive.

[JimiB]

Mine is on the third stage with the 82K to the plate and 22K to ground

22k to ground

do you mean 22K to B+?

[ODwan]

Hello!

I guess what you are talking about is the same thing as on the "Express Variation #2" drawn by Mark Abbot. This would be the same as the Response switch on a certain current production amp designed by Ken Fisher. I got this thingy in my Express build as well (though I use the .002/150k combo into the third stage).My experience is that it tames the amp to more of a vintage style, but with the flick of a switch you can have the all out Express back!
Another mod I did is a Voxy Cut control with 250kA pot and a .0047 cap. This is cool for taming the highs.

Timo

[Legin]

22k to ground

do you mean 22K to B+?

Whoops! quite correct 22K to B+, I have edited the original post

[LeftyStrat]

Another good discussion on fixes is here:

https://tubeamparchive.com/viewtopic.ph ... t=headroom

This weekend I will have some time to put it on a scope. I'm really interested in seeing what order the stages are distorting.

[ODwan]

Mine distorts with the powertubes first, then the PI and last the third gainstage. I read somewhere that's the way it's supposed to be and I'm lucky that it does so.

Timo

[LeftyStrat]

Mine distorts with the powertubes first, then the PI and last the third gainstage. I read somewhere that's the way it's supposed to be and I'm lucky that it does so.

Timo

Yes, I've heard that is how it is supposed to be. I have a suspicion mine isn't working that way. The distortion is a little "splatty". I think maybe my PI may need some work. I'm going to scope it out tonight.

[ODwan]

The tail resistor in the PI has to be just right I think. I had a 22k in it first and it did sound splashy. The scope said the PI was distorting about the same time the powertubes did. I then changed to 10k and the sound was there! This thing ain't about frequency shaping but the character of distortion.

Timo

[gearhead]

What scope you using? Is it remotely affordable

[LeftyStrat]

Mines a Protek 20MHZ I purchased years ago. I probably paid $300 for it, but you can pick up used ones off eBay for less. Check Tone Lizards web site for a good overview of the older models.

Once you get a scope and learn how to use it you'll wonder how you ever got along without one.

[ODwan]

I snatched my scope from ebay for about 80€ (think about 70$). It's a dual channel analogue scope which is great for comparing waveforms at different points of a circuit. I forgot the brand at the moment. You'll need a function generator with a scope, though.

Timo

[Normster]

Mines a Protek 20MHZ I purchased years ago. I probably paid $300 for it, but you can pick up used ones off eBay for less. Check Tone Lizards web site for a good overview of the older models.

Once you get a scope and learn how to use it you'll wonder how you ever got along without one.

+1 on the Protek 20MHz. They run about $280 at Circuit Specialists. Very affordable and it's a surprisingly decent scope!