Trainwreck gain?

[leleduke]

What is it that makes the express have so much gain?

[funkmeblue]

I'm guessing the extra gain stage and nothing in it's way

[rooster]

The Express has 3 gain stages, a bit unusual relative to early Marshalls and Fender. So yeah, as 'FMB' suggests, that 3rd stage is the culprit. KF fine tuned this stage using 150K resistor, but other circuit designers might have a stage like this with an adjustable pot of a slightly higher value, and then a MV to pull things down as necessary. .....Or do all this and add even more gain stages before the MV.

What's cool here though, with the Express, (although I think the 35 watt OT is too much volume for my needs), KF thought that this OT with NO MV (Master Volume) was the ticket to sonic bliss. Interesting really, because in so many ways it is. Read the post 'Pacific vs. Heyboar' and read moose's comments. Here you might see that - given an OT that performed as KF intended, the whole package might be a bit loud - true - but at least very 'smooth'. Smooth is good in a loud amp. Anyway, nice meeting you.

[leleduke]

Thanks, have a merry Christmas.

MD

[bluegate]

I read a lot that the powertubes should go into overdrive first, then the PI and then the preamp.

But I have installed a PPIMV type 2, and the gain is the same on full and on nearly off.
So this is a total contradiction.

I love the sound of my DIY Express, so no problem there.
But I wonder if the statement of Powertubes -> PI -> preamp is correct.
My guess is that all the gain is created by the PI getting overdriven by the preamp.
The Powertubes make the sound thicker as volume increases.

[tubetek]

If your Express clone is built to KF specs, you can use a scope to easily verify the gain/overdrive progression, as others here have done. If yours doesn't perform/react as suggested, perhaps you have component value or tube performance issues. Hope this didn't sound snarky, but others have been down this road. My (limited) experience agrees with the general consensus... PA-PI-PRE.
Tom

[bluegate]

I'm building a second express, I'll see if that one does the same.
This time I'm using Toneslut transformers.
Hopefully this one will be ready in about 3-4 weeks (waiting on ordered parts).

[tubetek]

Bluegate-
What were the transformers you used in your first build?
(I'm using the TuneSlut Heyboers)
Tom

[bluegate]

A dutch company PT, I believe it's called AE Electronics.
300-275-250-0-250-275-300 and 0-6,3V
And a Hammond OT, 1650H.
Tubeplates run at 406V, I use 6V6 NOS Sylvania.
I love the sound, and decided to build another with the better components,