Long AC wires or DC wires?

[schmidlapper]

I’m seeking a remedy to my inverted state that would fit my current situation, the two large can filter caps fit perfectly in the amplifier chassis, while the power supply chassis at most could accommodate a pair of smaller radial smoothing caps. Could I add 1000/80 radial electrolytic across the two legs in the power section, with the 13000/80 still in the amp and it be beneficial? Would a retro fit like this be sound or advisable? The alternative would require a whole new power supply chassis and rebuild to relocate the two big filter caps to fit the power supply chassis.

 

[rayma]

Could I add 1000/80 radial electrolytic across the two legs in the power section,
with the 13000/80 still in the amp and it be beneficial?

Depending on the wire resistance, and the capacitor ESR in both locations,
the small capacitors in the power supply chassis could be heavily stressed
from high local ripple currents.

 

[fredbloggstwo]

Question, would the resistance of the jumper cable be sufficient in order to add a second set of filter caps to the second chassis? Or would one need to add a larger resister between them. I ask because currently I have a separate power supply chassis with the smoothing caps located in the amplifier chassis due to size constraints. This appears to be incorrect based upon this discussion. I would be tempted to add a small lower value set to the power supply chassis say 1000uF, with the larger 13000uF left still mounted where they are. If the cable provides sufficient resistance, I would not be lowering my DC rail voltages. I have had it the wrong way round now for 27 years, but if it would be an improvement would add these caps. Thanks.

Regards,
Bill

Hi there Schmidlapper,

In your situation, I would be inclined to leave things as thy are. If they have been fine for 27 years with no problems, then why change?

As I mentioned in a previous post, I use a similar arrangement as youself with a high-power Class A amp. I am limited for space in the amplifier case so I put the (large - 500 VA) transformers in a seperate case with the rectifiers and 30,000uF per channel, then run a cable to the amp chassis with a further 45,000 uF and a capacitance multiplier. Its been that way for a number of years during design and testing with no problems whatsoever.

Best regards

Mike

 

[schmidlapper]

That is what I’m going to do in this situation. In the future I will design accordingly and allow room for the filtering in the power supply chassis also. I was curious about what all negative effects there could be. I would assume the re introducing of the AC back into the chassis is the big one, but are there others? Any pluses doing at all doing it how I did?

Regards,
Bill

 

[KatieandDad]

I run my Pearl B2 with a separate PSU. The power supply to the Pearl is highly smoothed DC which is then further filtered in the Pearl.

 

[ompdiburi]

Noise is also coming from rectifiers, usually I prefer to have transformer, rectifier and first capacitor in the power supply box.

 

[fredbloggstwo]

In my previous post I may have confused you - my fault for not being clear enough: part of the design of my Class A amplifier was to intentionally put the PSU in a separate box (and share the capacitance between them) to keep down noise and hum, not just to minimise space requirements.

Also remember that if you put the mains transformer etc. into the amplifier case that is made of metal, it has to be connected to mains earth for safty reason.


Kind regards

Mike

 

[schmidlapper]

I finally figured out a way to move the main filter caps into the power supply chassis and out of the amp. I had to add a chassis extension, not pretty but it works well. Also ran a much needed safety ground to the amp chassis. All changes together really have lowered the noise floor, most notably when I pull the amps inputs and it is amplifying anything it can into 101db sensitive speakers. Nice ��.