It`s something that I have been wondering the past few days. I had a lot of amps and receivers over the years from all kind of manufacturers like Kenwood, Marantz, Yamaha, Teac, Akai, Dual, Denon, Onkyo just to name a few and from a lot of cheapo brandsas well, and with power ranging from only a few watts to above 100w per channel.
I had 5.1 and 7.1 receivers with 60-100w per channel rated power coupled with 8200uF capacitors which I think they were kind of undersized for the advertised power (to examples are Yamaha RX-V395 5.1 5x60w and Marantz SR4002 7.1 7x105w receiver), and stereo amps with say 2x80w (example Kenwood KA-5040) coupled with 12000uF capacitors which in my opinion are adequate for that kind of power.
But how much does it really matter. I know High-End stuff use a buttload of filter caps but i`m not interested in that. Is there a law for power output/filter cap capacity, or some kind of minimum recommended for a given power output?
I had 5.1 and 7.1 receivers with 60-100w per channel rated power coupled with 8200uF capacitors which I think they were kind of undersized for the advertised power (to examples are Yamaha RX-V395 5.1 5x60w and Marantz SR4002 7.1 7x105w receiver), and stereo amps with say 2x80w (example Kenwood KA-5040) coupled with 12000uF capacitors which in my opinion are adequate for that kind of power.
But how much does it really matter. I know High-End stuff use a buttload of filter caps but i`m not interested in that. Is there a law for power output/filter cap capacity, or some kind of minimum recommended for a given power output?
ripple on the smoothed supply is inversely proportional to the capacitance used for smoothing.
I use +-20mF on the supply rail of my 8ohms capable amplifiers.
A two channel version would either have +-40mF supplying the two channels or two sets of +-20mF each supplying one channel in a dual mono arrangement.
For 4ohms duty amplifiers all these numbers would need to be doubled to maintain the same LF reproduction abilities.
Gootee had a long thread/s describing the amplifier's needs and how to size the smoothing to suit the loads. He also produced various simulation and spreadsheet models to remove the need to do a lot of the complex arithmetic that is needed when the models become complex.
I use +-20mF on the supply rail of my 8ohms capable amplifiers.
A two channel version would either have +-40mF supplying the two channels or two sets of +-20mF each supplying one channel in a dual mono arrangement.
For 4ohms duty amplifiers all these numbers would need to be doubled to maintain the same LF reproduction abilities.
Gootee had a long thread/s describing the amplifier's needs and how to size the smoothing to suit the loads. He also produced various simulation and spreadsheet models to remove the need to do a lot of the complex arithmetic that is needed when the models become complex.
Its better to have more smoothing but this can cause a problem with large currents on power up. You can end up blowing mains fuses. So a soft start circuit is usually required with large values of smoothing capacitors.
For a 600 watt peak amp I usually use 10,000uf/rail.
For a 600 watt peak amp I usually use 10,000uf/rail.
So 20.000uF total. Is that really enough for 600w amp? Also 600w total or per channel?
600 watts total.
I use the 600 watt amplifier on a disco and it gets thrashed and I have had no problems.
I use the 600 watt amplifier on a disco and it gets thrashed and I have had no problems.
You will have to ask their designers.
I know what works for me.
I prefer less rather than more so I don't have to contend with soft start circuits.
5x60 amps usually can only produce 2-3x60W and about 5x40W. And usually nothing uses all that power on all channel at the same time. This makes the so few caps look better.
nigelwright7557: is that a class D amp?
nigelwright7557: is that a class D amp?
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Sometimes excessive reservoir caps are used to try and make up for under sized transformers. Also, pictures of lots of big caps look good in marketing material.
Is there an optimum size one shld use in the entire filter supply? I read somewhere that the first pair shld be small to mitigate inrush while the last pair shld be large to provide for transients, especially for the low freq. On the other hand, I also read that the caps shld be kept small for fast charge/discharge. What do you guys prefer?
Class A amplifiers draw a higher current than their lesser brothers.
Class AB only draw maximum current at maximum volume.
Depending on the Power Supply Rejection Ratio (PSRR) of the amplifier design, the maximum current draw may produce rail induced hum into the output at high volume.
The PSU also needs to present a low impedance to the amplifier in order to accurately produce decent music.
In a commercial design its all a balance of cost against design. As most of your listening is done at surprisingly low power (5-10W), the smaller caps will usually suffice.
At higher volumes you generally can't hear the distortion anyway so it doesn't matter.
So, yes, bigger caps are better but not always necessary.
Class AB only draw maximum current at maximum volume.
Depending on the Power Supply Rejection Ratio (PSRR) of the amplifier design, the maximum current draw may produce rail induced hum into the output at high volume.
The PSU also needs to present a low impedance to the amplifier in order to accurately produce decent music.
In a commercial design its all a balance of cost against design. As most of your listening is done at surprisingly low power (5-10W), the smaller caps will usually suffice.
At higher volumes you generally can't hear the distortion anyway so it doesn't matter.
So, yes, bigger caps are better but not always necessary.
There are lot of calculations.
100W amp with 10kuF cap will have at max volume about 4V rail swings. That can generate a serious humm. Yes, the amp with feedback can compensate a lot, but stable supply is always good.
100W amp with 10kuF cap will have at max volume about 4V rail swings. That can generate a serious humm. Yes, the amp with feedback can compensate a lot, but stable supply is always good.
Our Oriental friends are very clever, they always try to save a buck.
If you look at the schematics of an eastern commercial design it will appear to be very complicated with loads of semiconductors. If you look at a good design it will normally be far simpler.
Good capacitors are EXPENSIVE. If you can design an amplifier that doesn't need them then you save a buck. Purists will argue that the complicated design will compromise the sound and I agree.
I use a Pass Aleph 4, a Class A 100W/Ch amplifier. The design is simple but quite stunning to listen to. It's power supply is enormous.
If you look at the schematics of an eastern commercial design it will appear to be very complicated with loads of semiconductors. If you look at a good design it will normally be far simpler.
Good capacitors are EXPENSIVE. If you can design an amplifier that doesn't need them then you save a buck. Purists will argue that the complicated design will compromise the sound and I agree.
I use a Pass Aleph 4, a Class A 100W/Ch amplifier. The design is simple but quite stunning to listen to. It's power supply is enormous.
Attachments
power in the lower ranges, say below 200W, does not affect the smoothing requirement.
It's about frequencies. F-3dB ~2Hz to ~200kHz (the amplifier passband) requires input filters of ~80ms & ~0.7us The NFB needs to be lower than the ~2Hz of the 80ms and the PSU needs to be at least an octave below that 80ms, i.e. ~160ms
8ohms and 20mF is 160ms.
My little full bandwidth lm3886 get the same smoothing as a Roender RM1 connected to +-50Vdc and capable of >100W and a Leach Lo Tim on +-58.5Vdc capable of 170W into 8ohms.
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Nigel has been going on about a soft start.
The Aleph uses 2 x 625VA transformers with 12 x 33000uF caps and doesn't require a soft start. It is a CLCC design so the inductors may reduce the inrush current.
The Aleph uses 2 x 625VA transformers with 12 x 33000uF caps and doesn't require a soft start. It is a CLCC design so the inductors may reduce the inrush current.
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