DIY capacitor bank....feasible?

[Duckzilla]

I've seen several amp maufacturers offer an external capacitor bank for their power amps. My question is would it be feasible to build one, or rather is it just an exercise in futility and spending money. I have a lot of experience with large caps in autosound, and they definitely make an impact, and as I said, I've seen some factory banks available. Any input would be welcome.

 

[EchoWars]

In autosound, the cars electrical system IS the power supply. Not so with home audio. Apples and oranges.

 

[mech986]

Yes, its fairly easy to build depending on the chassis form factor that you are using with your amp. The chassis sizes that you choose and the cosmetic will ultimately determine how many and how much capacitance you can put into your system's amp.

However, you'll also need heavy duty wiring, possibly a connector if it isn't hard soldered together with cables, likely a much heavier rectifier set or bridge, and bleeder resistors and bypass caps (the charge held without bleeding it off can be VERY substantial so you don't want these things charged when you're doing some troubleshooting or moving around.

Check this AK thread for some info:
http://www.audiokarma.org/forums/showthread.php?t=29399

 

[Duckzilla]

In autosound, the cars electrical system IS the power supply. Not so with home audio. Apples and oranges.

Not quite sure what you mean. In a 110v amp, the AC power capacitors are connected indirectly (??) to the power supply (via the transformer, Im guessing) and in a 12V amp, there is no transformer so a cap can be added easily externally. Is that correct?

 

[EchoWars]

The whole purpose of a power supply in home gear is to change AC to DC and provide a reservoir of energy. In a car, you already have DC, but because you've only got 13V or so we deal with 1 and 2 ohm speakers to get large power outputs. Adding caps in a car is simple and sometimes necessary. For home audio, the power supply provided by the manufacturer is nearly always more than sufficient, since we generally work with 8 ohm or 4 ohm speakers.

Adding large banks of caps for a home setup is a waste of time more often than not, even assuming you do it in a fashion that won't kill the amp.

 

[M Jarve]

Worst case scenario is that you kill the PT of the piece you operate on, unless you manage to cobble together some slow-start circuit or merely double or triple the capacitance.

The only real benefits of going well beyond the stock power reserves (provided it's adequate in the first place) may be quieter operation (there should be little or no line hum present in any competently designed amp), and a little more of a buffer when the amp hits its limits (insignificantly longer peak power output).

While I did just this sort of thing with some HT amps, and it did improve audible performance significantly, I have no compulsion to do so with the well designed power amps I use now. When it comes time to change out the smoothing caps on my 775's, most likely I will only go up in value due to having to make the caps physically fit, not for performance reasons.

If you look at real pro power amps, those designed for continuous operation at high power outputs, I think you would be surprised to see how little (or small) the capacitors are, especially compared to a decent home unit. However, these will also generally have very large power transformers or sophisticated, high-power SMPS's, using the caps just to smooth out the supply and lower the noise floor.

 

[Duckzilla]

Worst case scenario is that you kill the PT of the piece you operate on, unless you manage to cobble together some slow-start circuit or merely double or triple the capacitance.

The only real benefits of going well beyond the stock power reserves (provided it's adequate in the first place) may be quieter operation (there should be little or no line hum present in any competently designed amp), and a little more of a buffer when the amp hits its limits (insignificantly longer peak power output).

While I did just this sort of thing with some HT amps, and it did improve audible performance significantly, I have no compulsion to do so with the well designed power amps I use now. When it comes time to change out the smoothing caps on my 775's, most likely I will only go up in value due to having to make the caps physically fit, not for performance reasons.

If you look at real pro power amps, those designed for continuous operation at high power outputs, I think you would be surprised to see how little (or small) the capacitors are, especially compared to a decent home unit. However, these will also generally have very large power transformers or sophisticated, high-power SMPS's, using the caps just to smooth out the supply and lower the noise floor.

The amps in question are VSP Labs TransMos 150's, which appear to be of good quality and design. Think I'll leave well enough alone. I see your point about pro amps, since I also use a QSC RM850, which is designed as you describe. I appreciate the input.

 

[Duckzilla]

The whole purpose of a power supply in home gear is to change AC to DC and provide a reservoir of energy. In a car, you already have DC, but because you've only got 13V or so we deal with 1 and 2 ohm speakers to get large power outputs. Adding caps in a car is simple and sometimes necessary. For home audio, the power supply provided by the manufacturer is nearly always more than sufficient, since we generally work with 8 ohm or 4 ohm speakers.

Adding large banks of caps for a home setup is a waste of time more often than not, even assuming you do it in a fashion that won't kill the amp.

I understand now, and given the risk of damage to my precious amps, consider the case closed. Thanks for the advice.:thmbsp:

 

[Blue Shadow]

Two things to mention, the McCormack DNA-1 power amp and the Odyssey amplifiers.

The DNA-1 has a cap or two for each output transistor to supply the power from the power supply. The amp does not have the big coke cans we are accustomed to in amps having 100-200 wpc. This is an interesting design that sounds gear.

The Odyssey power amps have options available when purchased to have extra capacitance installed. Mike brought over his Khartago mono blocks for a little work and looking at them (see their web site for photos) there was a 4 pack of caps in the center of the board and what appeared to be speaker wire going to 4 additional caps on the periphery of the board.