Resistor type on Compressors

[Shakal]

Hey ya!

I gonna make a Ross Compressor for Bass, I already bought the components but the resistors that I don't know what type should they be.

Metal film resistors make difference on this kind of Effect? Is it better to get a "overwattage" resistor maybe they have better quality?

How can I identify a metal film resistor? I thought they were blue instead of beige carbon film resistors, but this guy told me that blue resistors are the 1% tolerance. Is there any blue resistor that is carbon film?

One more thing, I bought BC549C instead of the 2N5088 that I didn't find anywhere, will they make difference?

Thanks, see ya!

[markm]

I use carbon-film in everything, I don't notice very much difference but that's me.
Been using "noisey" comps for years. In a crowded smokey bar, the crowd doesn't care.
At least I've never had anyone come up to me and say....
"Man, your set-up is kinda noisey......do you have carbon film resistors or ceramic caps in there or somethin'"!!

[Mark Hammer]

Compressors will amplify whatever noise they see during the "quiet" passages.  The over-arching question is what the biggest source of noise is at the input to the gain stage in the compressor.  If you feed it a single-coil equipped guitar with poor shielding via a 3rd rate cable, and you tend to stand too close to the ventilation or fluorescent fictures, then I suspect changes to the input resistors in the compressors will not improve your noise situation very much.  If you feed the compressor a higher quality hot and quiet signal, then you may achieve some improvement in noise specs by switching to metal-film resistors, and perhaps a low-noise input transistor. 

One rose in the middle of a pig-sty doesn't necessary improve the aroma!

[Shakal]

Got it.

I don't have any noise in my Bass... Well, only when I play in front of the monitor and it's ON, when I turn it OFF the noise disappears. Anyway, I think it's good to have better quality you can, and the price difference is so low...

Someone know the answer for the other questions:

Is it better to get a "overwattage" resistor maybe they have better quality?

How can I identify a metal film resistor? I thought they were blue instead of beige carbon film resistors, but this guy told me that blue resistors are the 1% tolerance. Is there any blue resistor that is carbon film?

One more thing, I bought BC549C instead of the 2N5088 that I didn't find anywhere, will they make difference?

[Mark Hammer]

Wattage won't matter except with respect to heat dissipation.  Half-watt resistors aren't "better" than 1/4 or 1/8W resistors in any way other than the fact that they can pass more current before they overheat and produce magic blue smoke.  Actually, a great many pedals can easily work just fine with 1/8W resistors; we just have a harder time finding and working with those types of resistors.  The noise is not a product of the resistor wattage but often of the resistance itself.

Resistor "color" (i.e., the coating of paint over which the nominal value information is painted) will vary with manufacturer.  My experience is that metal film types often have the value printed on rather than painted on with color-coded stripes, but there are 1% metal film resistors that do have stripes as well.  You'll just need to ask for 1% metal film from whomever you buy from.  If the vendor does not specify that itis 1% metal film, then it is likely a 5% carbon film type.

A BC559C will be slightly better than a BC549C, and a 2N5089 will be slightly better than a 2N5088, from a noise perspective.  There are probably some exotic Japanese types with noise specs that will kick the ass of both of these, but I have no idea what they are.

(AN Note, BC559 is PNP, BC549 is NPN)

The limiting (pardon the pun) factor with a number of compressors is that what they use for the control element can't handle hot input signals.  The CA3080 OTA chip used in a number of well-known compressors does not take kindly to input levels above 100mv, and the FETs used in some others are also not robust enough to withstand hot signals.  That means that the signal-to-noise ratio in a great many compressor stompboxes can not be optimized.

The ideal in simpler floor boxes is an LDR-based compressor, since the LDR can take whatever you want to throw at it.  That means that you can feed the compressor input stage a VERY hot clean signal and not only will the compressor contribute little noise, but the LDR won't add any unwanted grit.

[Shakal]

Hmmm...

So, 1/4w is fine.

The atendant can't tell me if it is 1% carbon or 1% metal film, there are only cute girls that knows nothing, all they do is to look for components and look at the computer! I gonna take a look at another stores.

The BCs I'll place in a socket for transistors. If I find the 5088 or 5089 I just change it.

I think LDR based compressor will have to wait for my next project. It's a little more complicated, and will need more practice.

Thanks for sharing your knowledge. I'll make the pedal next week then I post the results.

See ya!

[tube]

transistors  BC559 is PNP BC549 is NPN

[Shakal]

OH yeah! Good point!

I think he meant: BC549 is better than 548 or 547 or 546 "noiseling" speaking.

I just saw the datasheets... The BC549 has the same noise figure than 2N5088, but 5089 is really better.

Thanks!

[Mark Hammer]

Oops! My bad.
I recalled reading somewhere that the 559 had good noise specs, and neglected to read the PNP part of the datasheet before zooming in to see the noise specs.  The specs ARE better than a 549, but being the wrong polarity kind of makes it moot.
The 549 and 550 does seem to be better, noise-wise, than 546/547.

[tube]

 You must reed  symbols A,B an C after number
h21e (gain)  A= 100-220, B=200-450,C=420-800.  is not large diferent between tyoe of 547-549 diferent is with groups A,B.C It is the same in groupe 55x.
I hope do you uderstand me english.

[Shakal]

OH yeah, it has to be the BC549C.

The gain isn't all. Noise figure is important too.

See that BC546 and 547 have 2dB typical noise figure and 10dB máx, against 1.2dB typical and 4dB máx of BC548 and 549. The 5088 has 3dB máx. Almost the same...

Your english is good, better than mine... I think non-english mother-language people can understand eachother... hehehe

Seeya!