Reducing noise In a Pedal !

Started by Izzy, November 03, 2006, 10:55:38 PM

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Izzy

Hi I have been wodnering about reducing noise in a pedal.
Doesn't the most of the noise gets into the pedal because of open leads of resistors and cap? Like if more leads are exposed then there is a chance those open leads will act like antenna?

If yes then why do commercial pedals have resistors soldered vertically exposing more leads ? rather than  soldering it horizontally?

If open leads acts liek anteena then when we use tin wire as jumper in perfboard wouldnt it worsen the problem? like this one?


Meanderthal

 If you put that in a properly shielded enclosure you eliminate the antenna factor. As far as exposed leads go, a PCB is no different, and a vero might be even noisier because of all those paralell leads and ghost capacitance wierdness...
I am not responsible for your imagination.

Izzy

Ahh! So  good sheilding enclosure is the main factor then?

Should tin enclosure be good enough? Or does the thickness of enclosure does matter?

brett

Hi
the main factor is the size of the largest hole or non-conducting part.
Holes up to about 1 mm are ok.  (Your microwave has holes that big in the front so that you can see in, but very little of the 800 watts of microwave energy inside gets out).
Holes of 10mm and larger would be best avoided if possible.
cheers
Brett Robinson
Let a hundred flowers bloom, let a hundred schools of thought contend. (Mao Zedong)

Izzy


Dirk_Hendrik

what kind of pedal are we talking about anyway??

Main sources of noise are semiconducctors or thermal noise of resistors. Especially in high gain applications (distortions, boosters) this noise will be amplified additionally by the gain of the effect. Get rid of that first by using metal film resistors (as opposed to carbon comp), use a quiet power sypply and low noise semiconductors.

I don't understand how a hole is going to give me noise ???
More stuff, less fear, less  hassle and less censoring? How 'bout it??. To discuss what YOU want to discuss instead of what others decide for you. It's possible...

But not at diystompboxes.com...... regrettably

Izzy

Damn I didnt knew that carbon film resistors were one of the factors for noise.  Isnt carbon film resistor the one that most of the people use here?
I had bought 500 resistor from radio shack. :D

Gus

don't worry about carbon film.  carbon comp is different.  Good section in "The Art od Electronics"

You are not going to get good fast answers because noise can be due to a LOT of things.

  Google Ask etc. read a bunch of books take a class.

Izzy

#8
Thanks.

One question though. I know its always better to solder resistors horizontally instead of vertically, because  less leads gets exposed and also it gets atatched firmly than soldeing vertically. But there are times when you are forced to solder them vertically due to the lack of space. So is it good to solder them vertically when we are forced to do so? Or we must find a way to solder them horizontally to  make a pedal as less noisy as possible?

How much risk  (noise wise) are we taking when we solder them vertically?


Dirk_Hendrik

That's entirely depending on the fuction of the component in the circuit.  Example:
If a resistor is soldered to the input of an opamp (a high-Z connection) the juction of the 2 is more vulnerable for picking up noise than when it's soldered to the output of that same opamp. (A low-z connnection). Therefore the rule of thumb is to keep connections at high-z points as short as possible.

Furthermore, coming clear over this thead,
Define for yourself that there's two sources of noise. One comes from the components itself (Carbon comp and carbon film) resistors, as well as semicionductors PN junctions). The other one is noise picked up by the circuit but caused by an external source.  Proper shielding helps but then again, that external source could also be another part of the same circuit. Switching noise from the LFO of a chorus radiating in the input of the output buffer of that same chorus, to give an example.
More stuff, less fear, less  hassle and less censoring? How 'bout it??. To discuss what YOU want to discuss instead of what others decide for you. It's possible...

But not at diystompboxes.com...... regrettably

GibsonGM

Let's not forget that 1. some noise is always going to be there, and 2., is going to be acceptable  ;)  High-gain distortion pedals are going to be noisy due to the fact that they are amplifying and then clipping.  Any noise at all (and there will always be some in an analog system!) is amplified along with the desired signal.   This is why amplifiers hum in when you're not playing thru them, and is normal.  Mild hiss from dist. ckts is not noticed when playing; most people stomp the box in when they start jamming and stomp it out when done.

A DIY ckt such as you've pictured, Izzy, has a certain amt. of internally-generated noise from the electrons passing thru it...aka 'thermal noise'.  This is going to be present no matter what you do; getting fancy caps and resistors might reduce it by like 1%.  You could spend $1,000,000 and not notice a major difference in hiss.   The main problem noise we're concerned with as DIY'ers is externally located, and is picked up by a ckt thru antenna action. Light dimmers and monitors are major culprits. Placing the ckt in a well-shielded enclosure has the most impact on this.  Whether a tin box can do the job depends on the factors others have talked about (hole size, etc) and the conductivity of the box.  It's a function of the wavelength of the RF noise that's invading the ckt.  The lower the frequency, the longer the wavelength, and therefore the larger the holes may be.  For your average pot, simply grounding the metal box correctly and using the shortest practicable lengths of wire to the pots should give more than satisfactory results.  A ckt is Always going to pick up a lot of noise when it's being tested out of its enclosure  ;)  Capacitance of wires is an issue (hence short wire lengths to pots).

There is a lot that's already been discussed about this, search the forum. Star grounding and shielding enclosures are places to start searching.  There's no good substitute for a good enclosure and proper shielding.  It's not rocket science once you do it and notice the results...   8)
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MXR Dist +, TS9/808, Easyvibe, Big Muff Pi, Blues Breaker, Guv'nor.  MOSFace, MOS Boost,  BJT boosts - LPB-2, buffers, Phuncgnosis, FF, Orange Sunshine & others, Bazz Fuss, Tonemender, Little Gem, Orange Squeezer, Ruby Tuby, filters, octaves, trems...

rogeryu_ph

Thanks guys, I get lot of info. Maybe this is why my stompbox is more noisy than the origiinal stock due to enclosure. I did project on TS9 and includes the mod I selected but the clone seems to be noisier then the original. I done this to experiment that I could find a cure to the original stock (Noise) but then it's noisier. I sort to buying noise gate DOD fx 30b but to no avail, cause it stop the noise only in the beginning but when after the note tend to end the nosie still appears before the noisegate kill the hum and hiss. Star grounding i'll search for it thanks again guys

Izzy

Thanks guys for taking some time to post. and special thanks to Gibson GM.  :D

I will definatley do serach on this topic and read.

So basically the main reason a pedal becomes noisy are:

1. Bad sheilding
2. Open lead
3. long wires to pots.
4. Unsheilded cables at input and output
5. carbon componentes like resistor.

GibsonGM

Yeah, those are the main causes, Izzy...they're really not a big issue until (as someone just posted on another topic) they become an issue!!   Following good construction technique like star grounding gives the best results. 
Using a good low-noize opamp like a TL071 helps (the 741's are noisy! but have their own pluses, too).  I might consider using 'good resistors and caps' and the like for a very clean ckt like a pure delay, but have never had a problem, even with the Easy Vibe.   Keeping it all clean is why I always suggest using one of the Taiwan Smallbear boxes for enclosures..good shielding.   I put together an envelope follower in a PVC endcap - it sounds awesome, but when I play out with it, it picks up every bit of interference around - even when bypassed.  So I have to wrap the inside with foil and put a bottom on it...didn't save any time on that one!  We could all read more on star grounding...there's an article on hum on the AMZ site, too.
8)
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MXR Dist +, TS9/808, Easyvibe, Big Muff Pi, Blues Breaker, Guv'nor.  MOSFace, MOS Boost,  BJT boosts - LPB-2, buffers, Phuncgnosis, FF, Orange Sunshine & others, Bazz Fuss, Tonemender, Little Gem, Orange Squeezer, Ruby Tuby, filters, octaves, trems...

MikeH

Since vero board has extra traces that aren't being used, which makes it more prone to the "antenna" effect, would it help to break the traces to the unused portions of track?  Do you know what I mean?
"Sounds like a Fab Metal to me." -DougH

Mark Hammer

Read the article on circuit design here: http://hammer.ampage.org/files/Device1-8.PDF

It provides some specs (circa typical 1979 op-amps) about the relationship between op-amps, component values, and noise that you'll find interesting. 

Key message to be derived: it is the context, not just the op-amp itself, that provides better and worse noise specs.

Gilles C

Quote from: MikeH on November 06, 2006, 09:36:59 AM
Since vero board has extra traces that aren't being used, which makes it more prone to the "antenna" effect, would it help to break the traces to the unused portions of track?  Do you know what I mean?

I do that for some of the traces to make sure it doesn't pick-up noise, or doesn't induce a signal into another part.

But I don't cut all the unused traces.Sometimes I connect the ground to some unused traces.

Gilles

Izzy

Thanks guys. I appreciate

I used shielded cables and shielded input and Output wire.
I dont know whether this is the right way or not but I did it this way:

http://www.diystompboxes.com/smfforum/index.php?topic=51235.msg384181#msg384181

I cant really tell whether the noise kinda decreased because of that shielded cable ot not. Because after I changed my opamp it was kinda less noisy then before or may be i have learnt to live with some noise. :D

But now its decent . It has some noise but I guess its from guitar or cable. When I put guitar volume at 0. There is very less noise compared to before, almost unnoticable noise. So I am kinda satisfied.
I havent found difference between ts-9 and ts 808 mode. I gues I will need to plug that into a tube amp to know the difference.haha

But this pedal sounds awesome.

Tube screamer  into boss GT6's drive stack amp = super awesome!

Sir H C

Don't forget coupling in the circuit itself.  Often with extreme gain you have to worry about a small signal on the output coupling back to the input and getting amplified again causing squeals and the like.  Decoupling capacitors and sometimes resistors to isolate the V+ (or ground) for different parts of the circuit are needed.  Also star grounding and supplies can help.