30W Class A Superbass/Model T (rebuild content)

[Zozobra]

I'm rebuilding my Shiva/Hotcat 30 into a superbass/model t-esque beast. 2xEL34@380VDC/4k primary, cathode biased to be pretty much class A. It's not run as hot as the hot cat 30 as those things eat tubes like a motherfucker. It'll hit around 50/55W wide open given how the shive pre performed.

The idea of this is that it will make for a good pedal platform to record with using my captor and it can get dirty all on its own if I push the master.

Once I've adjusted the pre in to taste I'll rebuild the power supply and power amp as I've never been too happy with it.

Initial mods will be; a switch to adjust the bass cut on the bright channel (22n/3n3) so I can get a bright black metal tone; and another switch to add in the model t 4µ7 bypass cap to the 3rd (or 2nd, depending on how you look at it) stage to get it nice and fuzzy. I think the real trick here will be getting the preamp voltage just right.



Progress today was mainly removing the old turret boards and drilling the chassis to take some of the valve wizards new preamp boards. They are really quite nice to work with. Not as versatile as making your own turret board of course, but a hell of a lot less effort and this is a simple build.

[soulsurfer]

Interesting. that sounds like a great project. Would love to hear it when its finished.

[ajaxlepinski]

Model T? Adjustable bias? LOVE IT!!!

Now I see why you started off with such a large chassis!!!
Looks like you have room for a spring reverb circuit!

[Zozobra]

It's going to fall somewhere between a T and a superbass in the end. They're more or less the same with just a few little differences, other than the poweramp. This will be cathode biased and not adjustable. This will mean the poweramp is a bit mushier and looser. I can always convert to fixed if I don't like it.

Heh, this is a different chassis to my last build. This one has sides for a start

[soulsurfer]

[ajaxlepinski]

It's going to fall somewhere between a T and a superbass in the end. They're more or less the same with just a few little differences, other than the poweramp. This will be cathode biased and not adjustable. This will mean the poweramp is a bit mushier and looser. I can always convert to fixed if I don't like it.

Heh, this is a different chassis to my last build. This one has sides for a start

Ah, I misread, "Initial mods will be; a switch to adjust the bass cut" as "Initial mods will be; a switch to adjust the bias" That's what happens when I try to speed read.

Looking forward to hearing about the progress.

[Zozobra]

Made a bit of progress with this tonight.

[soulsurfer]

bit by piece by bit

[Zozobra]

PI board populated. Time to start adding some wires to this motherfucker.

[Zozobra]

Input board wired up.

[Mamberg Jr]

Why is it so friggin big??? (TWSS)

[soulsurfer]

But for him it's for reallzzz. everyone knows UK dick is thick

[Zozobra]

Post server move repost:



TS and board interlinks wired up. Just the PI and power to wire up and we're good to flip the switch. I do want to rebuild the power supply and power amp at some point soon as I'm not entirely happy with it.

We just need ajax to post the fap emoji and we're back to where we were

[Zozobra]

Just the power to hook up and then I can test/play

[soulsurfer]

definitely

[ajaxlepinski]

Did someone request a fap emoji? The pleasure is all mine!

[soulsurfer]

I soooo wanna be a piece that piece of clay right now

[Zozobra]

Everything but the NFB wired up, which I usually do after the first testing as it will scream like a banshee if the OT polarity is wrong. This is ready to test tomorrow!

[Marc G]

so where do you get those PCBs? really neat idea for builds.

[Zozobra]

From the valve wizard/Merlin Blencowe. He does a full amp set so everything can be done with them. They're cheap too:
http://www.valvewizard.co.uk/universalpcbs.html

[Marc G]

From the valve wizard/Merlin Blencowe. He does a full amp set so everything can be done with them. They're cheap too:
http://www.valvewizard.co.uk/universalpcbs.html

sweet... I'll have to take a look.... seems simple enough even I could build an amp without killing myself lol

[Zozobra]

They're pretty easy to work with. I made a preamp/ecc99 mini amp using some with a ZVD DC-DC boost converter for the supply, powered by a laptop charger.

[Zozobra]

Powered up. Voltages look sensible and it sounds about right. I have a bad treble pot to replace but it's otherwise good to go.

[ajaxlepinski]

Congrats on the successful power up!

Can't wait to hear some clips!!!

[Zozobra]

Changed the preamp from a split cathode superleady type thing to straight up superbass. I also dropped the NFB resistor a little and it looks like I have the OT leads reversed so I have a positive loop and not a negative one so it sounded like ass. I'll swap those over tonight and then this is ready to live in its headbox until I decide I want to rewire the power amp/PSU.