M4 amp questions


M4 caps? Originally they had two 15000uf 75v I ordered 18000uf 80v chemi-con caps and was wondering if I should ya e got bigger or better? And what about the bypass people talk about is it worth it? If so what if should I get for that and does it go on pos or negative? First timer here but have soldered 100 plus speakers and done a few CD players but not amps yet ?


Hello @Bdraudio

Generally when you are replacing caps you can increase the voltage and that can be better depending on why the original ones went bad. I have seen instances in TVs when jumping from a 16V to a 25V has increased the life as the caps are not running as close to 100% all the time.

As far as changing the capacitance value I would not recommend that unless there is a reason you are needing to change it. Generally if you are just replacing the part you want to keep as close to the original as possible.

As far as adding a bypass cap it can help with filtering noise from the power supply. Generally you would find one between the VCC and GND of your power supply to help filter noise into your circuit. It can also help with incoming spikes.

I have not worked with an M4 amp so I am not aware of why people are adding them in your exact instance.


Ok yeah I understand the part you said on the caps about not increasing the uf value. On the amp board themselfs I agree about keeping them as close as possible. Now these are power supply cap I am taking about and I was told the uf acts like a valley wherein the louder and more demanding load I put on it If I go a little higher on the uf value it will substantially fill in the gaps in the valley better. If you get the analogy. And I ordered 2.2uf 250v Panasonic caps for the bypass. From what I understand it will help keep the noise down going through the amp filter it so I don’t get pops or power noise into the outputs of the amp kinda a filter at that. Now these power caps are a 5 lead cap two positive 2 negative and one other lead. My question is where do I solider the 2.2uf caps on the bottom of the board. Positive to positive negative to negative? That’s what I need to know.


I understand how a cap functions. The issue you run into is if the circuitry after the cap can handle the extra input from the larger cap.

If you are filtering the power supply coming into the amp you would be running the cap between the positive and negative line coming into the unit…


Thank you for all the info :slight_smile: helped me a lot. And yes the circuit after the power supply can handle 3000 more uf from what the guy at Yamaha told me he said I could go higher than that but I should not go past 22000uf so I am safe on that part. he stated that do not go above 80v he said 80v is fine being that 75 was original. Thanks for all the info guy really appreciate it. One more question now I know to go positive negative for the bypass caps but does it matter witch positive or negative on the caps there are two pos and two neg on each cap 5 lead? Or do I go between both pos and negative thanks again


Your positive leads should be connected and negative would be connected so it would not matter which you are using.

The exception to this being if you had a dual capacitance part such as a start/run cap.


Got ya I have not take apart yet or I would ha e seen that lol. I am glad you guys have this form :smile: it was a big help in learning for me. Thank you for your time I know it is valuable.