[]|[ GorE]

Like i wrote before,the wallwart has a 4700uF cap in it.The wallwart then supplies my LM317 and its accompanying capacitors as described in the "Improved Ripple Rejection" diagram in the lm317's datasheet.

See attachment . I have further added a 220uf cap at the output of the lm317 as recommended by tnt-audio in their diagram.

POINT IS :
After i turn of the mains supply,the audio keeps playing for 3 seconds after which it quickly dies in volume.

Does this phenomenon have any negatives about it in terms of the sound quality
? and could it make the sound a "bit" harsh in the highs ?

 

[Clutz]

It's staying on for such a long time because the capacitor is still discharging. I doubt that this is what is causing the harsh sound. What headphones are you using? What source are you using? Is the source MP3s? Have you tried the line out on a portable cd player?

 

[Ikon]

That's absolutely normal - the amp powers down as soon as the capacitors are discharged, not immediately when you unplug the power cable.

 

[grasshpr]

With a 4700uF Cap on the wallwart, I'm surprised it doesn't stay on longer...

 

[bjackson]

Quote:

With a 4700uF Cap on the wallwart, I'm surprised it doesn't stay on longer...

My thoughts EXACTLY.

 

[ATAT]

]|[Gore - It is unlikely that this would contribute to harshness... the cap in question is a power-supply capacitor. What it does is stores charge and discharges in order to stabilize the "ripples". The reason why your CMoy keeps playing is because 0v is lower than 24v, the cap discharges and holds it there. 4700 uF is awfully large (eh. who cares I guess..) so it keeps playing. I'm more worried about turn-on / off spikes that the capacitor might cause..

someone else can chime in, but there's a very good reason the PPA's 470 uF power caps are only 4 of them..

 

[Mod_Evil]

My 20.000uf on my power supply, my amplifier stay on for 1minutes

I use 2 x 4700uf + 4 x 100uf + 4 x 0.1uf + 4 x 1uf on my power supply per voltage. The sound? Is VERY clean...

It is absolute normal.

I thinking put a resistor to discharge this capacitance... Is this a good idea?

Thanks.

 

[ATAT]

WOAH Mod.. that sounds really overkill.. to the point of absurdity..

Seirously though, about putting caps on the rails..

Quote:

As for capacitors...There are a few different things going on here. When using large amounts of rail caps the in rush current these draw can blow up regulators on PSUs like the steps and tread. Some people have reported that sound increases up to a certain capacitance and then tends to get a bit lazy sounding. The best thing you can do is experiment and find out. Higher quality caps tend to be physically larger. On the PPA you might be able to fit 220uF Blackgates in each spot or 1500uF Panasonic FCs. You will need to decide for yourself which you like best.

Quote:

It's possible that the power supply is having a hard time during the turn-on time. Often a regulator will stay near 0V (2-3V at most, not enough to turn the LED on, or allow it to be bright if it is on a little bit) if it's having a hard time getting started. Too much rail capacitance is one way this can happen.

And tangent..
Quote:

Yes, there are limits. Some people have reported that the circuit just gets "sloppier" when there's too much capacitance. More critically, more capacitance means greater energy required to charge things up, and more energy that has to be gotten rid of when the amp powers down. These facts give different effects in different circuits. Some circuits will just lock up if there's too much capacitance. Others will have increasingly large turn-on and -off thumps, which can be dangerous to your cans' health. If there is no output protection on some of your circuits, more capacitance means more current for that circuit to play with during a short, so greater chance of blowing something up. Is there a way to calculate all of these? Theoretically, yes. But all three of the bad things I allude to above have different math behind them, and some of them you'd have to specify very closely to get any reasonable result. My practice is just to use common sense: if doubling the capacitance doesn't give you an audible result, back it off. If the turn-on and -off thumps get too loud, back it off. If the circuit locks up or starts oscillating...well, you guess.

Quote:

Another possible problem has to do with the chips you're using. Some op-amps I've used, for one example, do not like to see a slowly-rising power rail voltage at turn-on. They lock up the output near one rail unless the rails come up quickly. Neither of these issues is insurmountable, but since the amount of capacitance you're proposing is probably overkill, why press the issue?

Quote:

Preregulator caps should add up to 4000uF~5000uF. This will decrease the ripple to 1~2V making it much easier for regulator chips. More isn't necessarily better because the turn on and off surge will go thru the rectifiers and the transformer. This may damage them. Postregulator caps should be around 1000uF or more. Place these close to the amp as possible. Perhaps even have these for both channel. Note too big capacitance here can damage regulators or other components in the regulator stage. Note lastly that you probably can get away with smaller cap if you are using opamps. Since opamps come with high PSRR and CMRR. (Power Supply Rejection Ratio and Common Mode Rejection Ratio respectively.) Just becareful of using too much capacitance because it won't do necessarily do better with higher and higher capacitances. Most of the time, too high capacitance is more trouble than it worth.

and lastly..

Quote:

Where capacitance grow too high, the strain of the high charge currents on rectifiers, transformers and capacitors actually degrades reliablity and noise (again...) performance. Its far easier and cheaper to build amplifiers with good PSRR than to deal with these problems, too.

 

[]|[ GorE]

Quote:

Originally Posted by Mod_Evil My 20.000uf on my power supply, my amplifier stay on for 1minutes I use 2 x 4700uf + 4 x 100uf + 4 x 0.1uf + 4 x 1uf on my power supply per voltage. The sound? Is VERY clean... It is absolute normal. I thinking put a resistor to discharge this capacitance... Is this a good idea? Thanks.

Whats the reason for using different capacitance caps ? Could you please explain to this electronics noob ?

 

[blip]

Quote:

Originally Posted by ]|[ GorE Whats the reason for using different capacitance caps ? Could you please explain to this electronics noob ?

One of the higher level hardware adepts can give you a more technical explanation but in essence, different caps have different pros and cons. By combining them you can maximize the pros and minimize the cons.

One thing that is often cited is that smaller caps tend to discharge more quickly providing fast bursts of power whereas larger caps can provide more power over a longer period of time. Smaller caps can also be placed closer to opamps etc. which many believe improve performance.

 

[grasshpr]

Quote:

Originally Posted by blip One thing that is often cited is that smaller caps tend to discharge more quickly providing fast bursts of power whereas larger caps can provide more power over a longer period of time. Smaller caps can also be placed closer to opamps etc. which many believe improve performance.

Also, they provide better filtering at different frequencies, i.e., small capacitors tend to filter out very high frequency noise usually in the range of RF frequencies to avoid hearing radio in your headphone amps, where they will usually put them very close to IC in order to avoid this type of noise. Larger caps tend to be lower frequency filters, which will mainly smooth your DC output.

 

[]|[ GorE]

theres something different about the bass on the cmoy.The attack is good but the decay seems slow....evident largely on dance music and pop.It decays audibly slow ...not too slow but definitely lagging behind the other spectrum.

Caps used : 0.1uf Polypropylene for the Input.
Sanwha 470uF 35V caps for power section.

 

[Ikon]

Electrolytics (especially cheaper, non-low-ESR types) have a very bad behavior at high frequencies.
I would bypass the 470µF electrolytics with something smaller and faster - film/ceramic/tantalum caps around 0.5µF would certainly help.

 

[]|[ GorE]

the cmoy sounds very smooth and rich with no harshness on my Panasonic universal player.SO its the onboard sound to blame.

 

[ATAT]

by the way... the lead inductances could cause a LCR oscillator.. if you have that many caps it may be nontrivial. I'd parrot Tangent's suggestion of one good, appropriate value cap. Not many ridiculous sized caps paralleled with some high quality small caps..