eBay mono LM1875 kit

You can use two 24V supplies and connect them. One supplies side + to the other ones - .
Then, if you measure from the connection to left and right supply, it will be +24v and -24v. The connecting point becomes 0v or "ground".

The power of both supplies doubles. so 2x 250V like these from ebay, give a symmetric +-36v 500W supply.

AC-DC Converter 220v 240v 36v 7a 250w Isolation Schaltnetzteil Modul | eBay

This kind of supply is available in different power and voltage versions from 100,150,250W and 12,24,36V.
It works cool and has low ripple.
 
You can use two 24V supplies and connect them. One supplies side + to the other ones - .
Then, if you measure from the connection to left and right supply, it will be +24v and -24v. The connecting point becomes 0v or "ground".

The power of both supplies doubles. so 2x 250V like these from ebay, give a symmetric +-36v 500W supply.

AC-DC Converter 220v 240v 36v 7a 250w Isolation Schaltnetzteil Modul | eBay

This kind of supply is available in different power and voltage versions from 100,150,250W and 12,24,36V.
It works cool and has low ripple.

Ahhh that's pretty smart! That is basically just an ordinary dual supply, only... cheaper..? :sly:
Just to noob-safety-double-check: This is what you mean right?
 

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Good stuff! Bought a few different in different configs just to try them.
Are there any benefits from changing caps and resistors to non fakes if you have the right values lying around?


Chris; You changed R3 and R6 to 20k. Whats is your reasoning and did you experience any difference? Is it to lower the corner frequency and be able to use a smaller input cap?

/Hilding
 
Good stuff! Bought a few different in different configs just to try them.
Are there any benefits from changing caps and resistors to non fakes if you have the right values lying around?


Chris; You changed R3 and R6 to 20k. Whats is your reasoning and did you experience any difference? Is it to lower the corner frequency and be able to use a smaller input cap?

/Hilding


Hi Hilding


Sorry but i don´t know which resistor you mean with R3 and R6. but the be clear i just changed at my UTC2050 amp the Rf = Feedback resistor - the resistor between pin4 and pin2. from 22k to 20k nothing else.
i try it because i thought, in every amp, that less gain is less noise but to be honest i cant give you a Sound different now between my LM1875 (22k) and my UTC2050(20k) amps.
attached the schematic of the board.

both amp have:
i shorted the 10ohm resistor at the input
change the NP cap from 22µF716V to 100µF bipolar (rabbitz is an experienced DIY he use 47µF here)

decoupling caps from 220µF to 470µF (rabbitz use here a better cap a panasonic Fc 220µF)


chris
 

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Ah ok. Thanks for the answer! Waiting for stuff to arrive, so just in the planning phase for now. Eager to get going...

Built as shown in the schematic that Chris has supplied in post #647 gives a nice sounding amp.

I did 2 versions with the first based on that schematic and the second was one based on Brian Bell's (Chipamp.com) values and this version was my favourite.

eBay mono LM1875 kit

eBay mono LM1875 kit
 
I've built a stereo amplifier based in the layout of this ebay kit (original kit), but I printed my own pcb. I used C1=4.7uf MKL input filtering capacitor and changed the C2 capacitor from 47uF to 150uf, according to AndrewT suggestions in this thread (post #14). I am very happy with the sound, I am using it for more than 4 months for my desktop pc, without any problems (except the bridge rectifier's negative rail died, the symptom was a 400-500hz constant hum). I used a 15-0-15 transformer 60VA, psu has four 6800uF/35V (an overkill for sure, works just fine with just two 4700 uF). I used a speaker protection board with relays, but it might not be necessary. Without it, I rarely have pops when amp is turned on, and even so, they are slightly noticeable. I made the chassis from a metallic cookie box and the volume knob is made from a vodka cap (!) glued in a much smaller and ugly plastic knob. I earth-grounded the B50K pot, this made a huge difference in noise reduction when there is no signal at the input.
 

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