Can "big" input/output caps make a difference?

[WhenBoredomPeaks]

I built a headphone amplifier in the past.

There were calculations about where the input filter starts to make the low frequencies weaker.

Around 1 or 2uf the response curve was linear till 20hz. My Champion 600 will never output anything close to 20hz.

So using 47uF input caps instead of 1uF input caps could make any difference?



Bonus question:

Using a 10uF cap instead of 4,7uf in ROG Omega is allright? (i don't have any 4,7uf caps) I would swap both of the 4,7uf caps, the Q1toGround and the output cap too.

Schem, pics:

http://www.runoffgroove.com/omega.png
http://www.runoffgroove.com/omega.html

[GibsonGM]

Well, theoretically after you've gone below the cutoff point, the cap should just pass all freq's of interest, Boredom.  So you're right in that respect.  However, if the circuit was designed around 1uF or so, you should try to stay close to that since effective series resistance of the cap may affect its function - and the larger value could allow just enough lower junk in to affect operation.  Or maybe not!
All I can say is to try it out - if it sounds good, do it! 

[WGTP]

Especially on distortions/overdrives and fuzzes, the input cap is very important in establishing the "tone" or "character" of the device.  More or less bass going thru the distortion has numerous implications.  It's good to use a socket at that point to allow for easy substitutions, maybe even a switch...   

Sometimes I unplug the guitar and stick my thumb on the end of the chord to get a good 60Hz buzz going, and increase the bass/decrease the treble, so I can hear how large or small the input cap needs to be to start effecting the tone.  You can also estimate input impedance this way, to help if you want to calculate the roll off point. 

[Mark Hammer]

The low end of the signal can be defined/restricted at many different points in many different ways.  Certainly the input and output caps can be part of that, but you could make those suckers 1000uf if you want, and if a different DC-blocking cap elsewhere in between the input and output provides a rolloff at 200hz, the input and output caps will not be expected to make one pinch of difference.

Caveat:  There ARE some circuits, particularly simply 1-2 transistor discrete ones, where the only bandwidth limiting caps are at the input and output.  So, in that context you would be correct.  Not all circuits are like that, however.

Bottom line?  Get to know your rolloff points all through the circuit.

[Top Top]

In my gargletron build report I mentioned how much the input cap affected the sound of the pedal. It was distorting badly and had a dull muddy tone (with guitar anyway) with the input cap suggested in the layouts I found, so I substituted with a cap 1/4 the value and it sounded much better.

I have a fuzz with the input switchable between two input caps, one very large and one very small. The two caps make for completely different fuzz sound. The large one produces a big thick, sustaining fuzz, and the small one creates a gritty, thin, low sustain dirt. I did find, however, that beyond a certain point, there was no more audible difference in terms of the larger cap. It just took longer for the cap to charge up and actually pass a signal once they started getting too big.

[WhenBoredomPeaks]

Thanks for the answers!

I knew about the tone shaping capabilities of the lower valued in/output caps. (like the input cap in treble boosters, etc.)

But i think that any highpass filter cap higher valued than like 2,2uf, is freely interchangeable with any higher values in audiopaths.

[doitle]

I like to use 4.7uF caps for input and output. I've got a boatload of them and I think it sounds good so it's totally up to your ears. Throw a 6800uF cap on the input and output and see how it sounds. If you like it, keep it... And go buy some monsterous enclosures for your giant caps... lol

[WhenBoredomPeaks]

I like to use 4.7uF caps for input and output. I've got a boatload of them and I think it sounds good so it's totally up to your ears. Throw a 6800uF cap on the input and output and see how it sounds. If you like it, keep it... And go buy some monstrous enclosures for your giant caps... lol

Films are better than electros, so i like to use film caps when i can. (1uf, 2,2uf, etc. film caps)

Talking about giant caps:



I made this photo 1 minute ago.
The big one is a WIMA MKP10 1uF 400V cap, the smaller is a 0,22uF and the smallest is a normal cheap 0,22uF 63V cap which you can see in guitar effects.

[Thomeeque]

...
The big one is a WIMA MKP10 1uF 400V cap, the smaller is a 0,22uF and the smallest is a normal cheap 0,22uF 63V cap which you can see in guitar effects.

Do you use those MKP10 caps even in 9V pedals?

[doitle]

What constitutes "better"?

I actually do have a few film caps at home but I dont know their values off hand... I'll have to check when I get back. Maybe I can see if I can hear this betterness... lol

[WhenBoredomPeaks]

...
The big one is a WIMA MKP10 1uF 400V cap, the smaller is a 0,22uF and the smallest is a normal cheap 0,22uF 63V cap which you can see in guitar effects.

Do you use those MKP10 caps even in 9V pedals?

No, that would be over the top.

The bigger one is actually soldered in a headphone amplifier circuit, it is a highpass filter to eliminate DC offset.

The smaller WIMA is just sitting there because i had thoughts about build the whole thing into a 1590B case before, but i will put it into a bigger enclosure.

I wouldn't use this big caps in guitar effects, just in hi-fi audio circuits.

[WhenBoredomPeaks]

What constitutes "better"?

I actually do have a few film caps at home but I dont know their values off hand... I'll have to check when I get back. Maybe I can see if I can hear this betterness... lol

Im not a big audiophile myself, but as far as i know, they would never use electrolytes in signal paths. They are used for power filtering and stuff, but never in audio signal path.

But those little distortions and stuff what a electrolyte would add to the signal, could be unnoticeable in a guitar rig because there are many bigger things going on, noise, frequency roll-offs, distortions, limited amp-speakers. etc.

[WGTP]

Op amps usually have really low output impedance, which requires a large output cap to avoid bass roll off.  That is why you see 10uf and larger.  Other circuits have higher output impedance and may use .1uf.  Same with input.  The FF has low input impedance so you see large input caps.  Mosfets boosters have high input impedance and you see .01uf input caps and smaller.  As Mark pointed out, there are a variety of points thru out the circuits that can provide low or high roll off...   

[Gus]

WGTP  low output impedance does not require the use of a large value, in that case the input impedance of the following stage/load often is what sets the cap size if it is >> than the output Z.

With the ff the input cap works with the source impedance as well(the pickups inductance and resistance and volume pot(s)and tone circuit(s) and switching)

To understand what is going on you need to know the output Z and following input Z to size the cap with math.

[Ed G.]

What constitutes "better"?

I actually do have a few film caps at home but I dont know their values off hand... I'll have to check when I get back. Maybe I can see if I can hear this betterness... lol

Im not a big audiophile myself, but as far as i know, they would never use electrolytes in signal paths. They are used for power filtering and stuff, but never in audio signal path.

But those little distortions and stuff what a electrolyte would add to the signal, could be unnoticeable in a guitar rig because there are many bigger things going on, noise, frequency roll-offs, distortions, limited amp-speakers. etc.

Yeah, we're not audiophiles here. Especially when the goal is to ADD distortion to the signal. Some of the most revered classic big muffs had ceramic and electrolytic caps throughout the circuit, including the signal path! I think some of those funky old caps are what gave some classic effects character. Of course, the designers were probably just looking for the cheapest parts they could find!

[WGTP]

Damn Gus, I knew better than that.  I guess I shouldn't think of circuits in isolation.  Thanks for clarifying my erroneous assumptions.  The designs I mess with seem to work as I said, but generalizations don't work.