The Amp Garage

Have you tried clipping an extra cap across the 200uF cap? For example if you put another 200uF in parallel, does it change the speed of the motor-boating? Great tip, this solved the issue completely. Added a 220uF in parallel with the existing 220uF I put instead of the original 200uF...and the is...

Update. Still struggling to get it to run. Motorboating seems to be the only issue so far. I've played with it a little and have few more clues: 1) it's not the tubes. I bought a pair of NOS ECL80 tubes, replaced them and nothing changed 2) the input signal comes through the speaker, mixed with the ...

I don't know, nothing at the moment Seems to control local negative feedback network on the first stage, some sort of tone control I guess.

update: checked all 3 tubes for shorts and they seem fine. I also measured voltages and they seem reasonable, although they fluctuate a bit all the time while measuring, like +-5% or so. Could be related with the motorboating issue. I also checked that the two 22nF coupling capacitors aren't leaky a...

Stevem wrote: ↑Wed Nov 15, 2017 11:44 am And you have tested all the tubes for shorts?

no, I will do that.

@Malcolm, yes, I have replaced all three electrolytics with new ones.

Thanks. I've came across self-split PI before, but this doesn't seem to look like it. The second triode inverts the phase for the second pentode. So it's not self-split.
Or maybe I'm missing something.

Hi, I'm trying to salvage an old Italian phonograph and convert it into a guitar amp. It's an odd push-pull design with ECL80 tubes that might be interesting for guitar, apart from an auto-transformer that will need an isolation transformer to make it safe. I traced schematic of the amp minus the po...

Thanks RG. Didn't know that. I bought a new IRF820 today and it works pretty good. Also re-purposed the standby switch to control if VVR is supplied to the while amp of just the power amp. Make a huge difference in character. Will post more details in a separate thread early next week

Cheers

Thanks. Must be it, reads very low between each two pins

I decided to install a VVR circuit in my AX84 firefly (12AU7 selft split push pull) that is still too loud for my apartment. I used IRF840 for the mosfet and the schematic below. At first I followed pin numbers from the schematic but then I realized those were wrong (input voltage goes to drain pin ...

I downloaded the new version a few weeks ago and really like the component template functionality you added! That feature alone makes me think I will probably use it for layouts exclusively now. No more changing every single parameter every time I drop down a capacitor or resistor! :mrgreen: glad y...

If you are missing some components take a look at the current list of requests and feel free to add if not already there

https://github.com/bancika/diy-layout-creator/issues

that's my work queue, although I've been super busy last month or two.

If you're using all metal knobs, you might notice some hum when you touch the knobs if the pots are not grounded. But if you're using plastic or wood knobs, no problem. My opinion.... Yes. I have bourns 95s in my ibanez that has metal knobs and there's some noise if I touch the knob without having ...

BTW in most cases you don't need to use the legacy java, its just mac being stupid, I've found (jschem for example) that you can just right click on the app, do 'show package contents' and find the actual java compiled file in there somewhere and double click it and it will use the latest java. I d...

Haven't been active in a while. In the meantime I invested a lot of effort into DIYLC and added a bunch of new features. Check it out when you have a chance

https://github.com/bancika/diy-layout-creator/

Cheers