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Pot and cap replacement universal?

#22
i_got_a_mohawk said:
mF = millifarad (1x10^-3 Farad)
µF = microfarad (1x10^-6 Farad)


I can understand some confusion as I have seen MFD (all cap letters) used to represent microfarad.
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I'm probably older than you... It used to be the standard way to write it in the US, as was MF, before the whole metric thing. ;)

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Antique Capacitors and Schematic Diagrams
Prior to the 1960s, capacitors were called "condensers". Same part, same function, different name. You'll still hear the old name used by auto mechanics when they speak of the condenser in the ignition system on an older vehicle.

That earlier list of prefixes, although valid in the hayday of the vacuum tube, was used even less extensively back then. Mega (M) was the largest prefix commonly used and micro (f) was the smallest. To achieve larger or smaller multipliers, the prefixes were doubled up just like multiplying two numbers together. So, a small capacitor value might be 47ffF ("forty-seven micromicro farads") which was saying 47 x 10^-6 x 10^-6, which is the same as 47 x 10^-12, or 47pF. So, anytime you see "ff", just think "p" in your head. [Note 3] You'll also hear some old timers use the rather ridiculous term mickey-mikes instead of saying micromicrofarads. Makes me glad that we went to using pico.

To make it even worse, the symbol for micro, µ, was not used often before 1970 except for expensive physics and engineering texts. It was not a common character to find in a print shop and impossible to find on a typewriter, unless you had the special "symbol" typeball for the IBM Selectric. So, the lower case "u" was usually used in its place. That means that on schematics of the 1950s, a capacitor that was listed as 68uF is the same as one today listed as 68fF. In addition, the components themselves rarely had even the "u" listed. The actual part could have any one of the following printed on it:

68mF 68MF 68mfd 68MFD

It was always understood that "mF", "MF", "mfd" or "MFD" ALWAYS meant microfarad. Microfarad or micromicrofarad were the only units used for capacitors back then, so no one would ever even consider that "mfd" might mean "millifarad" or that "MFD" might mean "megafarad"! Even today, you'll still see "MFD" on capacitors, especially on motor start or motor run capacitors.
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So since you will never see a milli or mega Farad cap, mF and MF will still sometimes mean µF. It might not be correct, but it was the standard and common way to write it. :D You often write things the way you first learned them, and yes, I used to "dial" a phone. ;)
 
#23
The US needs to get it's head around SI units :p

(and it's still metric ;) )


Milifarad caps aren't really rare, tho the size would be a giveaway! and heck, seen people using farad caps in car stereo systems!


Negate my previous post then, it seems to just be one of these differences across the pond. I thought things would have been a bit more standardised in the US by now :p
 
#24
I would have stated categorically that all types of caps sound the same at the same value, but my brainiac engineer tells me that that is NOT the case.

He says that different types of caps have different "hysteresis" - That is they don't react the same to both directions of the AC signal. I believe this is why many above have stated that you can hear the difference between caps in an amp - this may be because there is gain taken and differences are magnified.

When designing audio gear, our engineers always chose different types of caps for different circuit functions, with metalized poly in the signal path.

SO - there may be some credence to those that say that they can hear the difference between different types of caps. Whether or not it matters to YOU is the question. AND - in some instruments, that cheap ceramic cap may be part of the sound.
 
#26
Gio S said:
I would have stated categorically that all types of caps sound the same at the same value, but my brainiac engineer tells me that that is NOT the case.

He says that different types of caps have different "hysteresis" - That is they don't react the same to both directions of the AC signal. I believe this is why many above have stated that you can hear the difference between caps in an amp - this may be because there is gain taken and differences are magnified.

When designing audio gear, our engineers always chose different types of caps for different circuit functions, with metalized poly in the signal path.

SO - there may be some credence to those that say that they can hear the difference between different types of caps. Whether or not it matters to YOU is the question. AND - in some instruments, that cheap ceramic cap may be part of the sound.
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Is this not a function of polarity in the cap itself? I seem to remembrance the old 'firecracker' type caps with polarity marks ( +/- ) on one or both ends - maybe they were just the electrolytic ones, but I think I remember the smaller ones having that on them too.

I can see that if you use a polarized cap then there can indeed be some differences in tone and bleed-to-ground characteristics.
 
#28
Gio S said:
I would have stated categorically that all types of caps sound the same at the same value, but my brainiac engineer tells me that that is NOT the case.

He says that different types of caps have different "hysteresis" - That is they don't react the same to both directions of the AC signal. I believe this is why many above have stated that you can hear the difference between caps in an amp - this may be because there is gain taken and differences are magnified.

When designing audio gear, our engineers always chose different types of caps for different circuit functions, with metalized poly in the signal path.

SO - there may be some credence to those that say that they can hear the difference between different types of caps. Whether or not it matters to YOU is the question. AND - in some instruments, that cheap ceramic cap may be part of the sound.
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You are correct when caps are used in the signal path of a piece of audio gear. But not when used for a treble shunting passive tone control in a bass. What you commonly hear with cheap ceramic caps used in tone controls are them being way out of spec.

And don't forget ESR and ESL. Caps are non ideal devices.
 
#29
i_got_a_mohawk said:
The US needs to get it's head around SI units :p

(and it's still metric ;) )
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We aren't using the metric system much, it's still imperial. And we know where that system came from, right? ;)

In everyday life, the only time you deal with the metric system here, is in buying a liter bottle of Pepsi. Cars have kilometers on their speedometer, but since all our traffic signs are in MPH, they are useless.

Personally I love millimeters. I'd be lost without them. :D

As far as electronics notation, you see stuff like "4k7" all the time now.
 
#31
SGD Lutherie said:
We aren't using the metric system much, it's still imperial. And we know where that system came from, right? ;)

In everyday life, the only time you deal with the metric system here, is in buying a liter bottle of Pepsi. Cars have kilometers on their speedometer, but since all our traffic signs are in MPH, they are useless.

Personally I love millimeters. I'd be lost without them. :D

As far as electronics notation, you see stuff like "4k7" all the time now.
Click to expand...

To be fair, we still use imperial for most things. Speeds are MPH (tho we do have KPH on the speedo too), height is still generally spoken about in feet and inches, weight is still generally spoken of in stone and lbs (1 stone = 14lbs).
 
#33
So my little question here seems to have taken on a life of its own. I'm flattered since I've never had a thread do that. ;)

But to recap;

  • If I'm happy with the sound, don't bother changing anything until it screws up.
  • 250k pots will deepen the sound as opposed to 500k
  • A larger number cap will also deepen the tone
  • Other than that, a cap is a cap except the orange drops look "cool" especially in a vintage context.

Do I have it right?
 
#34
gm2_in_co said:
So my little question here seems to have taken on a life of its own. I'm flattered since I've never had a thread do that. ;)

But to recap;

  • If I'm happy with the sound, don't bother changing anything until it screws up.
  • 250k pots will deepen the sound as opposed to 500k
  • A larger number cap will also deepen the tone
  • Other than that, a cap is a cap except the orange drops look "cool" especially in a vintage context.

Do I have it right?
Click to expand...

Looks good from this side of the pond.

I just am a little unclear if a Liter/litre is as long as the King's nose or not.
 
#35
gm2_in_co said:
So my little question here seems to have taken on a life of its own. I'm flattered since I've never had a thread do that. ;)

But to recap;

  • If I'm happy with the sound, don't bother changing anything until it screws up.
  • 250k pots will deepen the sound as opposed to 500k
  • A larger number cap will also deepen the tone
  • Other than that, a cap is a cap except the orange drops look "cool" especially in a vintage context.

Do I have it right?
Click to expand...

Yup. :bassist:
 
#37
SGD Lutherie said:
Some import instruments use VERY low quality parts. This is not to say that Gretsch did that. But look in some low end Fenders and real low end stuff like SX. Those parts wont last long. I know because I have to replace them on a regular basis. These are electro mechanical parts, jacks, pots, switches, etc., so they have to be robust. Also cheap pots often have bad tapers.
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Any idea where to find high-quality mini pots? It seems the only 500k linear mini pots are from a brand that doesn't even label its products with its name (that's manufacturer pride, there). CTS has a 500k audio taper mini, but no linear. Also, it's nigh impossible to find 8mm mini pots of good quality; CTS has only inches, and Alpha just has quarter-sized pots with that shaft diameter.

This was particularly frustrating when I did my potentiometer experiment; it was a bear finding good pots of the proper size and resistance rating. I eventually had to drill one of the holes in my control plate to accommodate 3/8" shafts.
 
#38
SGD Lutherie said:
And don't forget ESR and ESL. Caps are non ideal devices.
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isn't that the whole point that people who claim different tones from equal-value caps base their argument on?

i was skeptical myself until i compared some fancy "boutique" caps in a friend's les paul JR. trading out the stock .022μF for the fancy "paper-in-oil" .022μF, the new cap had more of that resonant wah-pedal vibe with the tone rolled all the way off. in fact, the owner, who's not a cork-sniffer by any means, actually didn't like the new cap, preferring the straight-ahead darkening of the stock one.
 
#39
Muaguana said:
Any idea where to find high-quality mini pots? It seems the only 500k linear mini pots are from a brand that doesn't even label its products with its name (that's manufacturer pride, there). CTS has a 500k audio taper mini, but no linear. Also, it's nigh impossible to find 8mm mini pots of good quality; CTS has only inches, and Alpha just has quarter-sized pots with that shaft diameter.
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Don't know if these will fit, but they are good quality:

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