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November 29, 2022, 02:30:43 AM

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200 watt amplifier board.

Started by tonyharker, May 21, 2021, 02:00:21 PM

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Looking for a suitable project to build for a bass amplifier, I found this board (bare PCB) on Ali Express . https://www.aliexpress.com/item/32942076982.html?spm=a2g0s.9042311.0.0.5d434c4dzHmGDd . Does anyone know anything about it, especially the schematic as one is not supplied, only giving component values on the board? Has anyone bought and assembled it?



You get what you pay for
I assume at that price you have to purchase all the parts?
I'd want verification that all the parts are available.
For me there are too many unknowns. xP

I'd be looking at something like this which is well researched.
Rod sells PCB's and you have a schematic as well as a full explanation of the circuit.
If you buy his kit you also have backup if needed.


main index here; https://sound-au.com/projects-0.htm#pwr


Yes I know about Rod and have already used a number of his boards, but I am not prepared to pay his ridiculous shipping charges of US$24.50 from Oz to UK for a board when all he has to do is stick it in an envelope.


When you asked the postal service, what did they tell you it would cost to send a padded envelope on that trip?


As I dont know where in Australia Rod lives, I can only use the information displayed on his web site and that is what he quotes. UK VAT must also be added (20%) and also the local Royal Mail charge for collecting this from me. This is not known but Rod estimates it at about £8.00. The P68 board costs US$32 (£22 approx). Unfortunately I am not prepared to pay this for one board no matter how good, even though the ones I have used before are certainly good quality.


What impedance speaker load do you intend to use ? If 4 Ohms, you will need a rail to rail Voltage of about 100V. For 8 Ohms, about 140V.

The good news is that  the capacitors used as local bypass of the rails on the board are marked as 220uF @ 100V so you are good there. But, only 4 output devices is on the light weight side for a musical instrument amplifier of 200 Watts. Better to have six or eight. Also, those standup 0.22 Ohm emitter resistors might be hard to find.


Rod designs are good and proven. But one big bottle neck is some board designs do not have mounting holes. The board is supported by either the power transistors clamping bolts or by the potentiometers. To me they are not that much flexible to use when using TO3 transistors or separate potentiometers. Just my view. There are many who have successfully used his boards. Regards.