What would you add/change to this design?

[leadfootdriver]

Yesterday I redid my practice amp into a sort of Mini Bad Cat with a Vox tone stack using what parts I had laying around. It sounded nice and clear, but not a ton of gain. Really dynamic tho!

So today I added another gain stage, and put a SPDT to switch it in or out. It sounds glassy and Vox Top Boosty with it in. It cleans up pretty good when you roll back too. But I'm sure it can be better. That's where you guys come in.

I guess one thing that I'd like to change is that when I get into power clip, the tone gets a bit blurry.

How could I make it a little more aggressive and gritty when I get into power clip?

I stink at drawing schematics, but hopefully you guys can make some sense of it.

Check it out!

[J M Fahey]

Put a better speaker there.
Since it already sounds "glassy and top boosty", donīt think you have a lot of electronic modding left, considering what you have there.

[Steve Conner]

Might be worth trying the Paul Ruby mod on your power stage, too, especially if it's an EL84.
http://music-electronics-forum.com/t17903/

[jmaf]

Might be worth trying the Paul Ruby mod on your power stage, too, especially if it's an EL84.
http://music-electronics-forum.com/t17903/

I thought we called it the Chuck H mod 'round here

[pdf64]

The schematic needs a grid leak resistor on the 3rd stage (switchable boost), and the master vol a coupling cap.
If the amp works they're probably in there.
The use of 22nF coupling caps with 1M loads allows excess bandwidth (3 octaves too much!) in guitar amps, the '-3dB frequency' is below 10Hz.
Bear in mind that those values seem to have been popularised by the 5F6A Bassman, which was intended as a bass amp.
Bringing the '-3dB frequency' up some is desireable in reducing flubby tone and potential for blocking distrotion.
Pete.

[leadfootdriver]

Thanks for the replies, and good eyes from the experienced!

There are a few errors in my drawing. I do have a 150k pull down resistor on stage 3. On the MV, there's a 220k resistor between 1 and 3, and a 22n CC coming in on pin 2 that I picked up from the Mini Cat schematic. But at first power up, the MV didn't really work like it should, so I grounded pin 3 and then it worked fine, so I left everything else. On the same note, the tone stack didn't really work either, so I tried a Vox TS, and like the results much more.

Here's the Mini Cat drawing I worked from.
http://www.webphix.com/schematic%20h...at_minicat.pdf


I haven't tried yet, but I was wondering about the power tube bias. The original value my amp came with was 100R. I've seen values between 100R and 220R in different schematics. How would a hotter bias change the clip tone on this amp?

I changed the drawing if you'd like to have another look.

Here's some pics of the amp. It's not pretty as it's probably the 6th version I've tried on this platform. I tried to use the space I had without totally reworking the whole board. Don't forget that I reused a lot of parts!

[leadfootdriver]

Still had some errors. I did change the EL84 cathode resistor to 150R.