Bypass Capacitors

[Stocker]

To make a long Application Note short, bypassing large capacitors with small ones changes the output impedance curve of the power supply. Wow, all those pages condensed into a sentence... I wish I could remember the title of that Note; it had graphs and everything...

 

[infinia]

The effect of a series .01uF cap on the upper end of an 8 ohm tweeter is approx 20 dB. To all that can hear a difference in or out are truly golden.

 

[cotdt]

I'm skeptical that bypassing capacitors make that much of a difference. I can't even notice it back when I tried it. I do notice a big difference when using good single caps though, especially in the treble. Probably the bypass cap value should make up at least 20% of the cap value to make an impact on the sound.

What caps are best for active crossovers? For amps the best caps I've heard are Teflons but Mundorf Supremes are good also. However the more expensive Mundorfs are merely above average IMHO. I'm thinking we can all save a lot of money by going active and thereby using much smaller values, and use single good caps rather than bypass which I'm skeptical makes a difference.

 

[lndm]

I'm skeptical that bypassing capacitors make that much of a difference.

I once approached an old Proton tuner I was using at the time, (probably had a devilish look in my eyes IIRC). I decided that all the electros mustn't be in the RF circuitry, and declared that all must be bypassed.

Solder and caps flew (dozens of them), mostly small value mylars I had on hand.

The end result sounded like the same tuner... after being dropped and walked on. The sound was edgy and irritating, kind of nervous sounding. I can at least say I'm glad I learned my lesson.

 

[soongsc]

I kind of think that the better caps you have, the less benefit of bypass. I normally use bypass if I'm using low cost caps. Some people might feel bypass is not good, probably is because the bypass cap is not significantly better in performance of the cap being bypassed. This might give adverse effects.

 

[POPBUMPER]

Using good quality caps is, by far, the single most significant "bang for the buck" in crossover upgrades, especially where treble and midrange are concerned. Of course, $400 "snake oil" caps are only for the foolhardy.....and a big waste of money. For all my custom crossovers, I have used Daytons on the low end (non-critical since they are in parallel to the woofer signal path), and Kimbers or Auricaps on the midrange and tweeters. I have also heard good things about Hovland Musicaps, though I have yet to sample any.

ANYONE can benefit from a cap change out, especially where older equipment is concerned. Of course, a network swap (where the WHOLE factory network is replaced with a more robust unit, utilizing superior components) is best...which I do on a regular basis!

Chris

 

[cotdt]

Dayton caps (Bennic) are warm-sounding and color the sound. I think Sonicaps or better should be used for the entire crossover, including the woofer circuit. Teflon caps have the lowest distortion, an all-Teflon xover would be nice. Bypass capacitors seem like snake oil to me. If you want to save money, you can simply make your own capacitors.

 

[lndm]

you can simply make your own capacitors.

Now there's an idea

I once dreamed of making coupling caps out two sheets of aluminium and four wafer thin spacers. I guess if it were that simple we would all be doing it

Seriously though, do you have a suggestion? Whenever I unravel a cap for a sticky, it seems almost impossible to achieve by hand.

 

[cotdt]

i beleive there is a member of this forum who makes really nice fluorinert capacitors. if he can make them, why couldn't anyone?

 

[lndm]

Doesn't he get them made for him? or am I just not up to date.

I don't have the skill to specify custom caps any better than what's available on the shelves, but I just sandwiched two sheets of foil around a foolscap sheet of note paper with a book on top and picked up 10nF.

I use some 10nF caps in my amp. I guess I would have a low inductance design here. Unfortunately it would be placement sensitive, humidity sensitive and would act as an antenna.

Maybe a gently rolled monolithic design?

I think I'll keep buyin' em for now.

 

[jerishi]

I'm curious what the best cap might be made of... rolled up (very thin) sheets of... copper?... with (teflon?) betwixt layers?... am just guessing... what makes one capacitor sound better than another... and why do some cost so much more than others.

 

[lndm]

One thing I alluded to but didn't point out is the rolling process. If stray inductance exists it will resonate with the capacitance to create a top end roll off and sometimes a peak at the resonance.

It seems, and has been generalised about in an article in AudioXpress, that larger electrolytics have issues in the midrange. Naturally there are good and bad examples of these capacitors. I believe I have heard upper mid anomalies whilst using generic electros in power supply duty and in cathode bypass duty.

In contrast, I have used Elna and Rubycon electros that have sounded good. In my experiences I have noticed a gentle rolloff at the top end. It is these caps that have given me the least trouble with bypassing.

YMMV.

 

[HiFiNutNut]

The need for bypassing is that capacitors, especially electrolytics, have a rising impedance towards high frequencies. Smaller film caps have much lower impedance at high frequencies than electrolytics.

I use 0.01uF polystrylene or 0.1uF polypropyline in CD Players, line level XOs or SS power amps to bypass electrolytics. Some people prefer not to bypass electrolytics. I think that would be fine because some modern high quality electrolytics do not have high impedance until, say, 50kHz.

In my passive XOs I only use ICW SA Clarity Caps (polypropyline) and in general polypropyline caps have low impedance until the MHz region. Adding bypass caps to bypass film caps in audio circuits, IMHO, is a waste of money.

Regards,
Bill

 

[noodle_snacks]

Well the i got the bypass capacitors today, with two volonteers to switch them in and out (external crossover). I *could* hear a difference, it was minor, the frequency balance etc didn't seem to change. Imaging just seemed to get a bit better, with a sort of seemingly less grainy sound. I am still sus about placebo effect, as well as measuring the changes that could be going on.

 

[lndm]

The most common difference I seem to notice between caps has to do with upper mid and high frequency balance and clarity.

I happen to feel that if you are going to like a new cap or bypass, you will know straight away or soon after. I often register it as a feeling rather than an analytical judgement. Stick with first impressions, I think.

 

[slhijb]

Newbee questions here. Hoping someone will help. Looking at placing a 0,01 uF bypass cap for the tweeter capacitors (Mundorf Supremes).

1. What is the best place to insert the bypass cap in the parallel Xover? Before or after the tweet cap? or does it make a difference?

2. Where can I get 0,01uF MKP1837 or Styroflex type bypass caps?

Thanks!!!!

 

[FullThrottleRic]

1. Bypass cap's are put in parallel with the main capacitor, not in series

2. Here

 

[lndm]

Looking at placing a 0,01 uF bypass cap for the tweeter capacitors (Mundorf Supremes).

I wonder whether replacing your caps outright could be a good way to go, that's how I'd do it. If, of course, the larger valued supremes are within your budget. If not, the M-caps give good tweeter performance.