Tube guy here. This is my first foray into DIY solid state amp. LM3886 Chipamp.com boards. I made a few minor modifications: 1000pF caps at the input from ground to chassis, 2.2 uF input coupling caps, moved R1 to after R2, added a 470pF cap from pin 10 to ground, increased Ci to 220uF, and the 2 extra 10,000uF caps sticking out with a couple of bypass caps. Everything looked great on the scope. Hooked it up to my system, and holy cow, major ground loop! No such problem with my tube amps, though. So until I can fix it, I'm listening to it being fed by my old Fiio X3. It really surprised me as to how good it sounds. This will likely see duty during the summer when it's too hot to run those hot tube amps. The two toggle switches are for soft start function with a CL-80 thermistor across the SPST switch on the live wire after the DPST switch. I flip on the green switch, wait a second or two, and flip on the clear switch to short out the CL-80.
Nice work
For your wiring I would remove the 1000pF at the input.
Have a look at p.12, it’s a useful document
BR
Eric
For your wiring I would remove the 1000pF at the input.
Have a look at p.12, it’s a useful document
BR
Eric
I tried shorting and disconnecting the cap. Neither had any effect. The hum's gone when I disconnect the RCA inputs or connect it to a portable device not powered by mains.
As it turns a out, the ground loop has always been there. I just didn't notice it on my tube amps because all of them have a potentiometer at the input, and all of them are low powered, and I listen at a very modest volume. As I was relying on the volume control on my DAC, the amp has a lot more power than my other amps, and there was no attenuation of the signal coming, the hum was loud. I need to take a close look at my power strip, and my mains earth. Old house with old wiring.
As it turns a out, the ground loop has always been there. I just didn't notice it on my tube amps because all of them have a potentiometer at the input, and all of them are low powered, and I listen at a very modest volume. As I was relying on the volume control on my DAC, the amp has a lot more power than my other amps, and there was no attenuation of the signal coming, the hum was loud. I need to take a close look at my power strip, and my mains earth. Old house with old wiring.
My 2011 MyRef:
The amplifier PCB is Mauro Penasa's original design. The relay based 96-step, +30 to -65 dB, volume control (the board on right wall) and its ATmega8-based control board (front right) are my own designs. The enclosure is Galaxy Maggiorato GX288 230 x 280 mm from Modushop.
The amplifier PCB is Mauro Penasa's original design. The relay based 96-step, +30 to -65 dB, volume control (the board on right wall) and its ATmega8-based control board (front right) are my own designs. The enclosure is Galaxy Maggiorato GX288 230 x 280 mm from Modushop.
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Thanks. Yes, I have been putting LEDs on the underside of my builds lately. I like the look. I used orange on the chipamp.
If anyone is interested I uploaded a build video to my YouTube channel (not monetized)
Main caps between main heat sink and regulator heat sink.
Can cause problem.
Try shifting, use wire to connect to PCB. Can mount on chassis etc.
How does it sound?
Can cause problem.
Try shifting, use wire to connect to PCB. Can mount on chassis etc.
How does it sound?
