Generic PCB designs - Preamp, LTPI, FX, Power

[bmx]

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?

In my amp it did not work well at all, which makes sense as soon as you hookup the ground you create a massive buzz, but just having the heaters
connected to the reverb board there was also a mean buzz,

I solved the issue because I had a 5V rectifier line that was not being used, therefore isolating the reverb boards supply from my heaters.
FYI , I guess your boards may be designed to all work together which I may try at some point later.
Thanks again for the cool pcbs..

A super common error when deriving a supply voltage off heater supplies is to forget that the heater supply has a center reference to ground. When you then create the supply and try to reference it AGAIN to ground essentially what happens is you are shorting one rail of the heater winding to ground through one of your rectifiers. It does take some care to solve this. Possibly one solution is to make a capacitively couple supply for the new circuit.

[tristanc]

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 line that was not being used, therefore isolating the reverb boards supply from my heaters.
FYI , I guess your boards may be designed to all work together which I may try at some point later.
Thanks again for the cool pcbs..

Yes - as noted above you've hit the issue of having a ground loop. Notice on my schematic I have separate grounds (GNDD and GNDA so I can choose where they join) and also I'm using a voltage doubler to get the higher voltage to then regulate down. So I don't think (someone correct me!) you can have a heater centre tap connected to ground with that configuration. That's why I used a spare tap (5V) and that solves the issue. Perhaps I should have made that clearer. Glad it's resolved.

[tristanc]

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.

[Guy77]

Hi Tristanc.
I sent you a PM.

Thanks

Guy

[audiosalvage]

Does anyone have pcb for high voltage effects loop

[tristanc]

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.

[audiosalvage]

I'm interested in an LD150 one I can use in my plexi clone. What is your price, shipped to 53085. Thank you

[tristanc]

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 commercial boards available. And you can share with others who’d likely be interested.

Tristan