Hiss and Component Choices

[angrykoko]

To set this up.. I hate hiss.  I hate pedals that produce hiss.  The first pedal I ever modified was my Boss eq; it just couldn't be used in front of an amp, so I modded it with one of the kits and the thing is now dead quiet.

That kit replaced some caps and IC's, really simple but because of my experience with that mod I always have this needling worry that my choices of caps / resistors / ic's or what ever might be hiss/noise producing.

So, is there some general guidelines to keep in mind when ordering parts?  Like this brand is better than that brand, use audio grade electrolyte caps, look at this value on IC's etc?

Things outside of tidy short wiring and shielded wire when possible....

This is one of those topics I thought would have become more apparent to me by this point but... is still a mystery.. like every time I read  "this pedal uses boutique parts"??..??  what the heck is a boutique cap?

Thanks.
Koko

[icecycle66]

Eh, is there a question...or some guidance in there somewhere?

[angrykoko]

So, is there some general guidelines to keep in mind when ordering parts?  Like this brand is better than that brand, use audio grade electrolyte caps, look at this value on IC's etc?

It was a round-a-bout way to ask that question.

[jkokura]

So, is there some general guidelines to keep in mind when ordering parts?  Like this brand is better than that brand, use audio grade electrolyte caps, look at this value on IC's etc?

I haven't seen a single, clear, definitive answer to your question thus far in my DIY experience. However, there are some basic rules that are sort of common knowledge:

1. Metal Film resistors give lower noise than other types. I use them almost exclusively. Some people find that other types work fine for them, and that's great, but it sounds like you would prefer metal film.

2. There is no 'rule' as to what brand, but rather different 'types' of capacitors make a difference. Film caps are often the first choice, and the types to choose from include polyester, polystyrene, and some others. Generally, Panasonic, Topmay and Wima caps are very common these days because our major suppliers supply them.

3. Electrolytics are known to be a noisy type of cap. I think that's partly why Tantalum caps are often recommended, but not the primary reason. I don't really know what the 'audio grade' types upgrade to make them better, but mostly I suspect it's marketing for extra money.

4. When it comes to ICs, generally it's not the brands but the type itself. For example, a TL071 is much, much quieter when compared to the classic 741 IC. Both are Single Op Amps, and are interchangeable, but it's obvious that the 071 is better for noise. The key with ICs and such is to experiment and switch out compatible ICs until you find one you like. They do sound different, and a lot of the difference has to do with noise.

5. On IC's again, because of the variety in their documentation, it's very difficult to point to one measurement value and say 'look at this' to find out their noise issues. Most of the time, they only give the data that sets them apart in a better way. The engineers in the crowd might give you an answer, but lets say that most of the DIY world has sussed out the good ones, and the lists are around. One rule of thumb might be that the more expensive an IC is, chances are high there's something that sets it apart.

Jacob

[angrykoko]

Thanks.

Yeah IC's, Caps and transistors are always the things that cause me the most pausing when ordering (especially if I'm on Mouser, some things can be worlds apart cost wise but look the same spec wise). 

On the Caps, you say that Tantalum are less noisy...What about MLCC -vs- Ceramic disc?  i've been wondering the same about them.

I only build pedals for myself so an extra $1-$2.00 to the total cost is worth it for less noise / better quality.

Thanks for the reply.
Koko

[culturejam]

The first pedal I ever modified was my Boss eq; it just couldn't be used in front of an amp, so I modded it with one of the kits and the thing is now dead quiet.

I think the important question is: Did the mod kit change just the part types or was it also the values?

A hissy pedal can often be cured by adding or augmenting some low-pass filtering.

[alanp]

Ceramic discs have a reputation for microphony. Don't know if that applies to MLCC.

[angrykoko]

The first pedal I ever modified was my Boss eq; it just couldn't be used in front of an amp, so I modded it with one of the kits and the thing is now dead quiet.

I think the important question is: Did the mod kit change just the part types or was it also the values?

A hissy pedal can often be cured by adding or augmenting some low-pass filtering.

It was the Monte Allum mod kit.  At the time I did it I was such a noob that I didn't even know I was replacing capacitors so no idea if values changed along with the type (a assumed only type before you asked that).  It did swap out the ic's though.  It really cleaned up that pedal though, I was amazed.

[calciferspit]

I believe in tantalums in all applicable places regardless of cost. lower noise, longer life, generally smaller size.

[derevaun]

Awhile back on FSB, Joe Gore posted the results of some capacitor tests he did. It's a worthwhile read, as is the ensuing discussion.

[night-B]

I believe in tantalums in all applicable places regardless of cost. lower noise, longer life, generally smaller size.

Tantalums are known for shorter life and to be fragile. They can litteraly explode if you treat them badly...

[raulduke]

I think metal film resistors (as CJ pointed out) are a good start for getting the noise floor down.

Making sure you have good PSU filtering is always a good idea as well.

Shielded In/Out signal wiring can also help.

Unfortunately, with all OD/Distortion pedals you are raising gain, so are always going to raise the noise floor no matter what you do.

[angrykoko]

Awhile back on FSB, Joe Gore posted the results of some capacitor tests he did. It's a worthwhile read, as is the ensuing discussion.

That was a good read. thanks!  I'll need to re-read it later but I liked this quote he made:

and in the future I'm going to worry more about decisions that actually, you know, matter. Like whether to trim my right-hand fingernails another sixteenth of an inch.

I agree with him but I think he was speaking more towards "mojo" components.  I don't believe in mojo components for the most part because I have to a/b things to hear any (if any) difference and even then sometimes is so small that I wonder who would even know (or I wonder if I could just adjust my eq pedal and get the same and..who would know)?  That was a good one thanks for posting that link.


So as far as my question regarding hiss and noise, I'm kind of getting this:
- Use metal film resistors (cool they are the cheep ones)
- Electrolyte caps are noisiest and still not sure if the "audio quality" ones do anything for the money.  If possible sub in a film cap for Electrolyte??
- Use whatever cap fits and stop worrying so much.
- transistors, diodes, etc - buy a bunch and just try them.
- Short (distance wise) off board wire's
- Use shielded wire in audio path wiring when possible.
- Learn how to tweak the filtering as culturejam points out

Jacob you hinted at a list for subs?  I've never stumbled on one.. do you know of a list you could send me?

Thanks everyone
Koko

[calciferspit]

I believe in tantalums in all applicable places regardless of cost. lower noise, longer life, generally smaller size.

Tantalums are known for shorter life and to be fragile. They can litteraly explode if you treat them badly...

The tantalum capacitor distinguishes itself from other capacitors in having high capacitance per volume and weight. Tantalum capacitors have lower equivalent series resistance (ESR), lower leakage, and higher operating temperature than other electrolytic capacitors. Tantalum capacitors are considerably more expensive than any other commonly used type of capacitor, so they are used only in applications where the small size or better performance are important. Tantalum capacitors have very low electrical leakage (high leakage resistance), so will retain a charge for a long time. They tolerate hot operating environments up to 125 °C, unlike most aluminum electrolytic capacitors. Because most tantalum capacitors being made are solid (no liquid electrolyte), there is no known wear-out mechanism. Tantalum electrolytic capacitors are less prone to "drying out" than aluminum capacitors, which tend to decrease in capacitance particularly when used in hot environments. When operated within their design limits, tantalum capacitors can maintain their designed capacitance under such conditions for decades. Tantalum capacitors can replace aluminum electrolytic capacitors in situations where the external environment or dense component packing results in a sustained hot internal environment and where high reliability is important. Equipment such as medical electronics and space equipment that require high quality and reliability makes use of tantalum capacitors.

[night-B]

Tantalum capacitors are, under some conditions, prone to self-destruction by thermal runaway. The tantalum oxide layer may have weak spots that undergo dielectric breakdown during a voltage spike. The tantalum anode then comes to direct contact with the manganese dioxide cathode, and the leakage current causes localized heating; a chemical reaction then produces manganese(III) oxide and regenerates (self-heals) the tantalum oxide layer.

However, if the energy dissipated at the failure point is high enough, a new self-sustaining exothermic reaction may initiate, similar to the thermite reaction, with tantalum as fuel and manganese dioxide as oxidizer. This can destroy the capacitor, and occasionally produces smoke and possibly flame.[1] To prevent catastrophic thermal runaway failure, auxiliary protective devices (e.g. thermal fuses, circuit breakers, or current limiters) may be used to limit fault currents.

This came from the same source as yours. Not a catfight, I don't want to have that type of incident one day, to prevent it, I don't buy tants, that's just my opinion.