Welcome to Solid State Guitar Amp Forum | DIY Guitar Amplifiers. Please login or sign up.

November 13, 2024, 04:10:07 AM

Login with username, password and session length

Recent Posts

 

Class d pedalboard amp project

Started by Miyagi_83, October 23, 2024, 07:38:45 AM

Previous topic - Next topic

Miyagi_83

Quote from: g1 on October 27, 2024, 08:19:10 PMIt should make no difference whether the fan is set to suck or blow.  Air flow should be equal either way.
Thanks, g1. Another question. Should I cool the chip or the heatsinking PCB plane on a class D amp?
Good night, Frau Blücher.

g1

Cooling is never a bad thing.  Capacitor failure is a way higher percentage of faults in the modern era, and it is mostly caused by heat.

Miyagi_83

Quote from: g1 on October 28, 2024, 01:55:36 PMCooling is never a bad thing.  Capacitor failure is a way higher percentage of faults in the modern era, and it is mostly caused by heat.
Ok, cool 8|
I'm asking because I read over at diyaudio that in a class AB amp it may be a bad idea to blow air at the transistors because the temperature sensing device might not operate correctly, so it was suggested to fan-cool the heatsink. I wasn't sure how it's done with class D.
Thanks.
Good night, Frau Blücher.

Loudthud

Quote from: Miyagi_83 on October 28, 2024, 02:20:19 PMOk, cool 8|
I'm asking because I read over at diyaudio that in a class AB amp it may be a bad idea to blow air at the transistors because the temperature sensing device might not operate correctly, so it was suggested to fan-cool the heatsink. I wasn't sure how it's done with class D.
Thanks.

Biasing is not an issue in a class D power amp, the transistors are either on or off.

Miyagi_83

Quote from: Loudthud on October 28, 2024, 08:42:22 PMBiasing is not an issue in a class D power amp, the transistors are either on or off.
All right,thank you. There's still so much to learn  :)
Good night, Frau Blücher.

Tassieviking

I cam across this today looking for something else so I took a picture.
I remember now that there were a trimpot on the input of the amp module so I removed it and put a pot on the front of the box
There are no stupid questions.
There are only stupid mistakes.

Miyagi_83

Quote from: Tassieviking on November 05, 2024, 04:13:41 AMI cam across this today looking for something else so I took a picture.
Thanks, Tassieviking  :tu:
Looks really tight inside but, from what I understand, you had no issues with that, right?

Sadly, I didn't have a chance to do anything with mine last weekend :(  but I'm not in a rush.
Good night, Frau Blücher.

Tassieviking

#22
I have not had any problems with it, I just havent used it since I blew up the last laptop power supply, I think the amp is still fine.
If you want to see an even smaller one there is a company selling tiny 30 watt poweramps that are 25mm x 25mm x 100mm.
Even their 50 watt pedal is nice with a VU meter on it.
https://svisound.com/index.php/products/amps-cabs
There are no stupid questions.
There are only stupid mistakes.

Miyagi_83

Quote from: Tassieviking on November 05, 2024, 09:42:19 AMIf you want to see an even smaller one there is a company selling tiny 30 watt poweramps that are 25mm x 25mm x 100mm.
Even their 50 watt pedal is nice with a VU meter on it.
https://svisound.com/index.php/products/amps-cabs
Nice!
Good night, Frau Blücher.

Miyagi_83

I wanted to test the amp today using an oscilloscope, so I connected a dummy load resistor and hooked up the probe and ground across it, but the waveform didn't even budge even when I applied a test signal to the input.

Later I remembered that the output on this module is bridged, hence such reading on the scope. I started wondering, what are the odds that I blew the amp? I shorted one of the outputs to ground, after all. When I connected a speaker and a guitar, it worked, but I don't know how to tell if it's working correctly.
Good night, Frau Blücher.

Loudthud

Use the scope to see if there is signal on each side to ground.

Miyagi_83

Quote from: Loudthud on November 07, 2024, 02:03:50 PMUse the scope to see if there is signal on each side to ground.
Thank you for the suggestion. I'll do that tomorrow (it's 11 pm in this part of the world) and report back.
M.
Good night, Frau Blücher.

Miyagi_83

#27
Quote from: Loudthud on November 07, 2024, 02:03:50 PMUse the scope to see if there is signal on each side to ground.
Perhaps it's important to mention first, my oscilloscope is nothing fancy. It's a 1 MHz, single-channel digital unit by FNIRSI (DSO-153) with a built in signal generator. I wanted something cheap for starters in case I were to mess it up.

I tried the following just now. I used the built-in signal generator, plugged it into a Tube Screamer clone to be able to change the signal amplitude more easily. I tested this setup with my scope and it worked ok.

Next, I plugged it into the amp module, turned it on and tried testing it following your suggestion. A sine wave appeared on the screen when the volume knob was at minimum, but nothing happened to its shape when I turned the volume knob up. It just started floating up and down. The same was true for both outputs.

EDIT: Attached is the sine wave with the Screamer's volume knob at 0.
Good night, Frau Blücher.

Loudthud

#28
Quote from: Miyagi_83 on November 08, 2024, 05:41:49 AMNext, I plugged it into the amp module, turned it on and tried testing it following your suggestion. A sine wave appeared on the screen when the volume knob was at minimum, but nothing happened to its shape when I turned the volume knob up. It just started floating up and down. The same was true for both outputs.

See on the screen where it says the frequency is 284.09 kHz ? That is the class D modulation being filtered by the output filters on the class D amp. The floating up and down, that is the signal from the generator. Set the frequency of the generator to 500 Hz and set the scope to 10mS (Ten millisecond) per division. Set the Volts per division to 5 to 10 Volts per division, whatever it takes so the trace doesn't go off the screen vertically. The scope trace will look really thick or out of focus because the 284 kHz will still be there.

Miyagi_83

Thanks, Loudthud. I'll do that as soon as I get some time on my hands.
Good night, Frau Blücher.