The Amp Garage

I built one of these and it works great https://www.marshallforum.com/threads/simple-attenuators-design-and-testing.98285/ 2nded. Brilliant bit of kit. I’d even consider building it ‘in’ my next amp instead of power scaling / VVR etc. https://www.marshallforum.com/threads/simple-attenuators-design-...

I’ve to hunt down those boards over Christmas - I was certain I had spares. If I do, happy to send one to you for the cost of shipping (~£10). If I don’t the gerbers are on my github and these would come under the 10 for $10 at PCBway et al, so would likely work out cheaper than some other commercia...

yes. I’ve made a pcb for both valve and solid-state that run off usual B+. Both are Merlin’s series loop. I’ve some valve loop boards still available.

I've a few spare boards if anyone is interested. Just cover shipping.

2 x preamp
10x effects loop
6x phase invertor
3x power supply

I may also have a solid state FX loop (4) and reverb board (4) available.

Let me know if interested.

Get 5 of mine made from PCBway for ~$25 and you can make pretty much any preamp (minus switching etc). https://github.com/tristancollins/amps/ ... tar-Preamp

Or, fire up KiCad and use them as a starter to make what you want.

Hey just FYI I used your loop and reverb boards in one of my test amps, I had a major buzz hum with the reverb board on the 6.3 line, I was curious how you rectify and ground the heater supply when the center tap is raised to a positive DC voltage? I solved the issue because I had a 5V rectifier li...

Great - glad you're up and running. Keep me posted on how the build goes.

Yes, you'd need both (the SS ones) and the loop has the take-off point to feed the reverb.

Something's up at your end. I've just downloaded the repository afresh as a zip from github (https://github.com/tristancollins/amps/archive/master.zip), expanded it, navigated to the Reverb board, zipped the GerbersX directory and uploaded it to PCBway. I also opened the .pro file with no issue. So ...

steve07868 wrote: ↑Sun Sep 13, 2020 6:38 pm Could you please kindly provide gerber files in RS-274X format?

this is what JLPCB said about the files..

I've put them up - let me know if JLPCB accept them.

Tristan

I've added the reverb board Gerbers. But these are in 'normal' format which is fine for PCBway and many other fab places. I've never used JLPCB... I'm more concerned that you can't open the source files. You should be able to open the ".pro" file, open the pcb file and export the Gerbers in RS-274X ...

What were your HT, G,S,D, bias voltages? I didn't make a note I'm afraid. I was in a bit of a rush, so wired it up, checked continuity etc, turned on and scoped it. Spotted the issue and verified with a quick play-through. Of course, in my haste I left off a jumper to apply the HT to the 'top' of t...

Thanks Martin - found the issue. Would help if I had applied a bias voltage to the LND150 gate... Forgot an all important jumper. All working as it should. Some readings: Clean out sine wave: 2.8Vpp (0.11W) with self-split, ~4Vpp (0.25W) with source-o-dyne into 8ohm load Max out square-ish wave: 7Vp...

Did you ever get a chance to play around with this? OK, so finally got this installed, and it passes sound. But I think there's an issue. The attached shot of the scope shows what's happening: Light blue is amplifier input (200mV) Pink is speaker output Dark blue & Yellow (inverted) are the outputs...

I've populated the board, made the change to fixed bias (cut a trace and needing a jumper from memory) and I'm now just waiting for a free afternoon to get it in to the build. Ideally I want to take some measurements of max clean output and max overall output before and after the installation. I sho...

In my haste to get a board made I forgot about the problems with using FETs and self bias... So I've modified my PCB to be fixed bias. I can easily modify the boards I have had made (cut a trace plus a couple of jumpers) so no real issue. Will report back when I have it working. https://github.com/t...