[rickcr42]

Quote:

No, Mica is not really "expensive" (by the way you can get it in Lee's electronics, just next to Main electronics) but it does cost 10x as much as an equivalent polypropylene. The bigger problem for me is that it's considerably larger than polypropylene for the same capacity.

in the pf range you are pretty much stuck with micas if you can't find the value you need in polystyrene

Quote:

I like capacitors that are big.

actually some wisdom there

for some unknown to me reason 600V poly caps sound better than 200V poly caps

nothing blatant but it is there in the note separation during low level passages

again , i have no idea why

another point i should add

Just me but i do not use low value bypass caps on large value capacitors

even electrolytics

for the same reason i do not like multicaps

Something just not right about the so called "capacitor crossover" where the circuit speed of exit is different for each capacitor which is a different frequency range

i don't want the high notes coming through faster than the low notes

 

[Prune]

Quote:

Originally posted by aos No, Mica is not really "expensive" (by the way you can get it in Lee's electronics, just next to Main electronics) but it does cost 10x as much as an equivalent polypropylene. The bigger problem for me is that it's considerably larger than polypropylene for the same capacity.

My question is how mica and polystyrene differ in performance (and yes, I know Lee's...).

Quote:

Originally posted by rickcr42 And yes , a cap can pass a square wave but not all circuits can ! question is ,do we need or want to ?

Not passing a square wave means slew rate limiting. In an amplifier with feedback a slew limited input stage may be overdriven by a signal not sufficiently bandwidth limited, causing transient intermodulation. I do wonder, however, if one can have too high a slew rate.

Quote:

Originally posted by rickcr42 Just me but i do not use low value bypass caps on large value capacitors even electrolytics for the same reason i do not like multicaps Something just not right about the so called "capacitor crossover" where the circuit speed of exit is different for each capacitor which is a different frequency range i don't want the high notes coming through faster than the low notes

Can you elaborate on that, as I'm not sure how this practice exactly affects the signal? I'm very interested in the issue of bypassing large capacitors. For example, in a power supply, would it be a good idea to bypass large electrolytics with some spare Solens I have?

 

[JohnFerrier]

Quote:

Originally posted by rickcr42 and even if there were not ,the condenser mics MUST use cap coupling if they use (and they do) phantom power ! there is no way around the DC bias voltage riding on the signal if it is not blocked by a capacitor

...but, there are ways to level shift out DC without using capacitors....think about how a complementary output pair of transistors is biased with +/-DC at their inputs and yet the output is 0Vdc (as an example). Other types of circuits can shift larger amounts of DC. Or even feed the DC biased signal to a differential amp with the other terminal also DC biased...hey, it's a bit like PPL's DC correction circuit! -->http://www4.head-fi.org/forums/attac...&postid=750972

hehehe...I guess I don't know but maybe microphones operate on the principle of capacitance...some humidity sensors use capacitance...that doesn't help PF though...however, I think microphones use inductance...don't personally know though....


JF

 

[rickcr42]

in power supply bypassing what you are doing is shunting the high frequency noise signals to ground due to the cap being in parallel with the voltage (low pass filter) and not in series .

Capacitor coupling of an audio signal is there for DC blocking so what you need is a series connection (high pass filter) which means the entire audio signal passes through the capacitor so the capacitor has a major bearing on the final product

Slewing Induced distortion (S.I.D) was covered in the 70's by Tom Holman and using test equipment as well as his ears it was determined that if you top out the high end of the audio signal at 40khz the group delay is not audible but any stage downstream would be immune from S.I.D. if it were a slower stage than the preceeding stages

the "crossover/multi-capacitor' analogy was on the apparent speed of the audio signal passing through the various capacitors that make up either a multicap or DIY big cap/little cap paralleling.

Just like with a speaker having a "phase correct" crossover and the various drivers placed on the speaker panel at a depth that coincides with the crossover to make in the end a phase coherent image there has been some statements made in ad copy and elsewhere about the capacitor crossover "speed" at which each cap in parallel passes the signal according to cap size and thus the hinge frequency at which the cap cuts off the signal

Common sense will tell you that if the caps are not identical in material (dielectric) and size the then the signal will come out the other end as a mix of two different signals rather than one coherent signal

can this be heard ?

I find it to be a non issue with loudspeaker listening . The nature of the room/speaker interface does far more damage to signal coherence than a simple cap could ever do

but with headphones i find it not only audible but irritating

YMMV but you can try a simple test of your audio irritability point

Listen to a capacitor coupled amplifier with just the single coupling cap , say usually one of around 4.7-10 uf is the norm , then clip one acros the cap of 1/4 the value of the main cap and listen

then remove the cap and listen again to see if you hear a difference

Some do not

I do

and somewhere someone said "bypass all big caps with little caps" and most,including me blindly followed

at least until i thought about the concept then ran some of my own listening tests

what i found was , and this is only with headphones unless i specifically listen for it , the signal is smeared a bit , less clear and the note separation suffers with low level passages

Instead of very sharp and distinct individual sounds there is a blurring , a bit of haze is added that was not there before.

From that point on i choose to use the best capacitor i can find at the value needed for that particular point in the signal chain.

Just one

again

YMMV (your mileage may vary)

 

[aos]

Quote:

for some unknown to me reason 600V poly caps sound better than 200V poly caps

I think I've read somewhere that higher voltage capacitors tend to have better numbers for those coefficients (DF, FDA, XYZ, whatever). But I never thought that one could actually hear the difference as it's small.

 

[ppl]

Rick this is true that paralelling any two disimiler capacitor types will result in the effect you discribed if incorrectly done if properly implimented can be almost as transparrent as a single cap but not as transparrent as one large value and another smaller value of the same cap material IE 1uF Non polar Black gate N series with the 200uF or so polarised Black gate. this also is true af any similer polar and non polar Electrolytics like the Muse nd pannasonics. The long leed to short leed supper E arangement can be done on any electrolytic pair

 

[rickcr42]

I found that a single 2200uF black gate sounded better on the output of a SE class A mosfet follower meant to drive low Z cans and using a single polarity power supply than did the same cap bypassed with a 10 uf film cap even though conventional wisdom says it should sound worse .

Using a 1uf in the same spot was transparent but there being zero need for the 1 uf cap why add it since the reasoning behing the bypass was to add some calrity in the mid-range ?

The same configuration in a speaker driving SE class A mosfet follower ,the pass zen , and using a large value cap but equally divided between two electrolytics had zero effect on the sound !

zip ,nadda , even though i used the amp with very high efficiency (96db/watt) speakers that have a way of magnifying any abberations,
unless i listened with and without the poly cap with headphones connected through an asl upc matching transformer

same amps,same associated equipment,same transducers,same ears,etc

a valid test in my mind

And since the effect is not heard and when heard is detrimental to the sound it is my choice to eliminate the extra part ,a costly part btw ,entirely from my designs and go with the single best part i can obtain/afford in that spot

power supplies as i have stated are a different beast and since the ps caps are shunts , each has a particular frequency responsibility that has to do with noise filtration-the noise being shunted to ground at the selected frequency

Big caps for the 50/60 hz hum and ac line ripple

little caps for the rf hash riding on the ac sinsoidal

 

[ppl]

Silver Mica is like some ceramic caps high "Q" and polystyrene like Film lower "Q" Mica for high current tempature bypass and subber or compensation use Coupling too small a value.

 

[kwhead]

Quote:

Originally posted by rickcr42 the "crossover/multi-capacitor' analogy was on the apparent speed of the audio signal passing through the various capacitors that make up either a multicap or DIY big cap/little cap paralleling. Just like with a speaker having a "phase correct" crossover and the various drivers placed on the speaker panel at a depth that coincides with the crossover to make in the end a phase coherent image there has been some statements made in ad copy and elsewhere about the capacitor crossover "speed" at which each cap in parallel passes the signal according to cap size and thus the hinge frequency at which the cap cuts off the signal Common sense will tell you that if the caps are not identical in material (dielectric) and size the then the signal will come out the other end as a mix of two different signals rather than one coherent signal

Huh, that's interesting. Do you have a source other than "ad copy" for such a theory? Sitting here with a pencil and paper I can't figure out what on earth is being talked about. I can't generate any appreciable phase error even with full capacitor models with oversized ESR and lead inductances. As far as "speed" goes are we talking about phase? There is no propogation delay in a capacitor that I'm aware of.

 

[rickcr42]

when it comes to audio gear sound measurements are only a guidline

It can tell you if something will sound bad 9high noise or distortion etc) but can not tell you what will sound good

take two componants with identical specs but totally different designs and they will sound entirely different .

the capacitor example is something that maybe can and maybe can not be measured

but

It is not a point of contention that different capacitor dielectrics sound different ,or even the same dielectric but from two different capacitor manufacturers sound different

add to that the frequency turnover point per cap into a known impedance will be different according to the size value of the cap

and finally throw in the "speed' of small caps being faster than large (easily checked with a scope and signal generator-square waves)

now parallel a small fast cap with a slightly slower med size cap and finally a large slow cap and you have what ?

A very confused signal !

Instead of passing one coherent waveform through a single capacitor,regardless of if it passes a clean square wave or not ,you get three signals with different speed/phase/turnover freq mixed together at the output of the capacitor soup

Single driver loudspeakers can have a clarity that can blow your mind but good at all things they are not and sometimes a subwoofer for the lows and a super tweeter to assist the highs can give you a more complete overall sound

Each speaker has a different speed and frequency rang but

1-you can physically place each driver for a coherent phse integration

2-most room/speaker coupling makes "1" moot anyway . The room will mostly kill any phase coherence unless we go back to the one individual driver

Does that mean multi-driver speakers with crossovers suck !

Not at all

It means it works out in the context of the room/ear interface

Headphones do not cut you that kind of slack

not only are they the classic single full range driver without crossovers but the ear/transducer coupling eliminates ANY room interaction with the sound

so what you end up with is direct drive from the amp to the headphone to the ear

any abberations will be design flaws and not caused by poor room integration there being no "room"

THIS is where multi-capacitor bypassing can and is heard !

The signal may sound clear until it is directly compared to the single cap or no cap .

It will be like someone upped the low level detail control (no such thing of course !) and you will lose the what i like to call"confusion factor" caused by having too many paths from the input to the output ,all carrying the same information but delivering in with different speed/phase/bandwidth

Again this does not hold for power supply bypassing due to the supply bypass being a "shunt" of unwanted signals to ground and thus not in the signal path of the supply (also an audio signal path) while the audio signal coupling cap IS in the direct path between you and the music

as always

YMMV

 

[JunktionFET]

I've listened to some polypropylene caps that sound quite harsh and edgy. Often times I would rather listen to a cheapo electrolytic than one of these poly caps. The worst that a bad electrolytic will do is blur the sound together into a lifeless boring mass--but at least my ears won't bleed.

Not all caps are created equal--audition several brands and you'll find that some really suck and some really stand out as winners.

 

[Porksoda]

Quote:

Originally Posted by ppl While Feedback and the power supply are indeed part of the signal path they are secondary as opposed to primary paths.

Pardon me if this is already been beaten to death, but:

Take a second and think about exactly how an op-amp works. In a non-inverting topology, the amp is essentially varying the voltage at its output such that its two inputs are equipotential. Hence, you put in 5 volts to the positive terminal, and it will vary its output until the voltage at the negative terminal is 5 volts. So, you use a voltage divider to divide the output voltage by 5 and connect this to the negative terminal. The op-amp increases its output to 25 volts so the voltage at the negative terminal will be 5 volts after the voltage divider. PRESTO! 5x amplification. When you put a capacitor in the feedback loop you create a low pass filter. It impedes low freqencies, increasing the voltage divider's effect for that particular frequency. Thus, a low frequency is amplified MORE so that its output at the negative terminal is still equal to the input terminal. This is how bass boost works.

We can therefore conclude that the feedback loop is the primary determining factor of sound coloration. Because the op amp will by nature try to cancel out any effects in the "signal path" between it and where the feedback loop connects, components in the feedback loop in fact have a much greater impact on final audio quality than what is in the signal path.

 

[rsaavedra]

Where is the poll option "I have no idea"?

 

[ppl]

Quote:

Originally Posted by Porksoda Pardon me if this is already been beaten to death, but: Take a second and think about exactly how an op-amp works. In a non-inverting topology, the amp is essentially varying the voltage at its output such that its two inputs are equipotential. Hence, you put in 5 volts to the positive terminal, and it will vary its output until the voltage at the negative terminal is 5 volts. So, you use a voltage divider to divide the output voltage by 5 and connect this to the negative terminal. The op-amp increases its output to 25 volts so the voltage at the negative terminal will be 5 volts after the voltage divider. PRESTO! 5x amplification. When you put a capacitor in the feedback loop you create a low pass filter. It impedes low freqencies, increasing the voltage divider's effect for that particular frequency. Thus, a low frequency is amplified MORE so that its output at the negative terminal is still equal to the input terminal. This is how bass boost works. We can therefore conclude that the feedback loop is the primary determining factor of sound coloration. Because the op amp will by nature try to cancel out any effects in the "signal path" between it and where the feedback loop connects, components in the feedback loop in fact have a much greater impact on final audio quality than what is in the signal path.

Yes this has been covered lots of times. Also i would like to point out i am completely aware of your observations. This is obvious since this exact same method is what i use for Bass Boost.

No we can not conclude that the feedback loop is the primary factor for coloration as the small caps talked about in the feedback loop in this thread regards High Frequency compensation and at these frequencies there effect is far less than the effect of a coupling capacitor operating within the audio range. I agree that any capacitor in the feedback Loop will degrade the sound Also why in my designs you completely bypass the Bass Boost cap in the feedback loop within the audio Frequency range when you turn off the bass boost. I have bee a long time out spoken highly controversial critic of capacitors used for frequency compensation and inter-stage coupling.