Pedal Mule 30 - Prototype build

[jelle]

I love the cabinet!! Walnut?

[RJ Guitars]

Yup, walnut... I had a few made up like this for a combo amp using a Wreck sized chassis. A very nice compact cabinet but with the amount of bass this amp puts out you'd think it was a big closed back unit from the sound it can make. As soon as my lungs get healthy I'll sand it a bit more and put some clear coat on it.

[jelle]

Looks great!!

Do not sand walnut without protection or you will be sick again.

[Littlewyan]

I believe C8 should be connected to R8 and not directly to ground if you're using NFB. The amp will have a lot more headroom once you do this.

As for the bright cap not working there is no reason why it shouldn't make a difference, even if its as small as 100pF. Have you tried hooking the cap up directly to the volume pot or the turret board to rule out the switch?

With regards to the hum thats quite a mystery. Once you get the NFB going that might fix that.

[RJ Guitars]

I believe C8 should be connected to R8 and not directly to ground if you're using NFB. The amp will have a lot more headroom once you do this....

That made a big difference - Thanks for finding this! At one point I had the "Deep" switch doing good things but changed so much stuff around chasing the hum that I lost track of the changes.

As it turns out, the Negative feedback seems to just make the tone suck... not sure why that would be? I had the switch wired so that with no NFB the switch was in the deep position. In the other position I added some NFB. However, it seems that no matter how little I added, it sucked tone. It also had a hideous pop every time I switched it. I got rid of it altogether and decided to re-purpose the switch.

In this case I am using a finished faceplate with a control option that I am not sure makes a better amp... I had been curious about that 330K resistor with a 250pF cap across it that feeds the volume control. I removed the 330K resistor - very bright and not much bass. So I changed the 250pF to .001uF and it seemed pretty decent. Now by switching in and out the 330K resistor I get a true "Deep" effect and the faceplate actually adds a very usable feature.

The amp is sounding the best it has so far and finally it's at that point where I could feel good about telling somebody "build it just like this". I'll update my schematic to the "As Built" status and get to work on the cabinet...

[randalp3000]

RJ, try bypassing C4 and R6. Really opens up the amp.
might take away some of the voodoo tho

[Littlewyan]

The NFB might not be that good without a Presence control.

If you want more headroom try putting a 220K to ground after R7 to make a voltage divider. Its a waste of signal (in my eyes anyway) but it might give you the tone you're after. Or try a 12AY7 instead of a 12AX7.

[RJ Guitars]

Looks great!!

Do not sand walnut without protection or you will be sick again.

Good to know... I may put that off a bit longer.

RJ, try bypassing C4 and R6. Really opens up the amp.
might take away some of the voodoo tho

That seems to align with my experience in changing C4 to the .001 value. In my earlier report I mentioned that the amp had a bit of a tightness and compression even though it is very clean sounding. That tightness went away with the .001 coupling cap. The amp just sorta sorta rings out now...

The NFB might not be that good without a Presence control.

If you want more headroom try putting a 220K to ground after R7 to make a voltage divider. Its a waste of signal (in my eyes anyway) but it might give you the tone you're after. Or try a 12AY7 instead of a 12AX7.

As is the amp has a lot of headroom so that hint of breakup without any NFB was a bit of a pleasant surprise. I'm curious if anybody else has tried NFB with this circuit? To me it just sucked tone and did nothing good otherwise.

I haven't changed anything in the last 24 hours and the amp is very fun to play through. However, I have been wondering about the use of a pentode in V1, I know that has been done before...

[RJ Guitars]

Finally all the hardware arrived to get the amp mounted into the finished cabinet... very cool amp and a decent size for moving between gigs. Ready for some road testing now... I hope I don't scratch it.

[RJ Guitars]

I updated the schematic posted at the beginning of this thread. The updated schematic shows the final "As Built" configuration of the amp. It is sounding extremely good these days and has inspired me to look into the Octal output version and also the addition of reverb... stay tuned.

[Zippy]

I hope I don't scratch it.

Want me to do it for you?

That way, there is no guilt or remorse.

I'm here for ya.

[LeftyStrat]

That cab is gorgeous. I love walnut.

[RJ Guitars]

Thanks guys... I'll see if I can avoid scratching it for myself for now.

Walnut can sorta make the average hack seem more like a real woodworker.

I finished up the schematic for the octal version and I have someone who will help me with the first prototype using a pair of 6V6gt output tubes. Should be sorta like AC-30 meets Fender Deluxe.

[cbass]

nice!Walnut is definitely upm there with my favorite woods to work with and look at.

[DocJames]

looks great RJ! That walnut really looks nice.