# How many µF do you recommend for this amp?

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#### hugobross

Hi, I'm building a 2 x 500W rms amplifier for use on parties etc... This amp excists of 4 mono-amplifiers (bridged to eachother) and a power supply of 2 x 50 V.
Do you know "big" the capacitance must be to play loud and clearly without any distortion?? Right now, I've already 6 capacitors of 37000 µF.

Thanks anyway.

HB

#### hugobross

I forgot this

the minimum load of the amp is 8 ohm.

HB.

#### tsz

With 3 * 37,000 ( I assume that you meant that there is 6*37,000 per monoblock) per rail and a peak current of about 12 amp (1152 W in 8 ohm) gives a ripple voltage of approximately 0,76V peak to peak, not likely to be audible. But you can't have to much capacitance
ESP has a nice article: http://sound.westhost.com/power-supplies.htm

Regards
/Tobbe

[Edited by tsz on 09-28-2001 at 11:53 AM]

#### djk

The Carver M1.5T that I used to own had a single pair of 3,400µF caps to put out 1,200W at 8 ohm in bridge mode."The values for power supply capacitance can be realistically determined by a consideration of the numerical value of W C R where W is the line frequency (377 rad/sec), C is the power supply capacitance, and R is the load resistance.

For this amplifier, the design load is 8 Ohms (although it will easily drive 4 Ohms) at full power. An WCR value of 10 yields about 10 per cent ripple (pk.-pk. ) and a value of 100 has about two percent. Below 10, the power supply will have serious problems and values of about 100 will achieve diminishing performance returns. The minimum value then, for each of the four power supply capacitors should be about 3,000uF and the maximum about 30,00OuF. Capacitances above this value may cause diode bridge failure due to turn-on surges and are not recommended." http://www.passlabs.com/projects/a40_9.htm

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