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Why not balance?


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5/23/2003 10:28 AM
Brad1
Why not balance?
Probably a simple answer. And I understand that since everything has "always been that way" it would be hard to change midstream....but. If balanced circuits reject noise better than unbalanced, especially with cabling, etc., why haven't people started making balanced guitars, stompboxes and guitar amp inputs? Cost or design prohibitive? Tonal considerations? Would it help cut out extraneous noise any?  
Just a thought as I go through my room trying to balance as much of my recording equipment as possible (which is surprisingly comprised of about 80% balanced rack-mount effects and recording stuff).  
Brad
 
5/24/2003 3:18 AM
Enzo

A solution looking for a problem...  
 
Balanced lines inherently reject common mode noise, but unbalanced lines can be quite quiet. You should use good quality cable. 100% shielding is a must. There are plenty of cheap cables with shielding less than that. A good cable won't pick up much noice at all. It is dependent on length to a great extent. Those one, two, or three foot cords in your rack will pick up nothing. If your gear already has balanced I/O, great. But to convert just to go to the next thing in the rack is a waste.  
 
Noise in your guitar system is probably not due to the cable picking it up. Balanced will do nothing to the noise from the guitar itself, nor will it take care of grounding problems.  
 
Balanced lines have been used for eons in long lines. That 50-100 foot snake for example. Guitar cords are usually 20 feet or shorter. When you get longer than that you start to roll off the highs. Yes, that depends on the cable, but it holds in general. Mic cord runs are often longer than that, they often travel the snake as well. But even a 20 foot mic cord protects the sound. But mics put out a tiny miniscule signal which is not much louder than the ambient noise. So we like to use the balanced lines for them.
 
5/24/2003 7:08 AM
Steve A.
Not exactly balanced, but...
Brad:  
 
    ...using shielded cable with two center conductors would significantly reduce the noise in most guitars. If you've checked out John Atcheley's GuitarNuts site, he took a fresh look at the grounding scheme used in a strat and came up with suggestions that quiet them down considerably. The big paradigm shift is to separate the signal returns "grounds" from the shielding "grounds".  
 
    You could take his ideas one step further by wiring your guitars up with a stereo jack and using a shielded cable with two center conductors. Once you get to the amp you could connect the signal return wire to the ground shield and plug it into a mono input jack. For the stereo jack in your guitar, you would wire up the signal return lead to the ring so that you could plug in a mono cable and have it work normally.  
 
    As long as you are plugging your guitar directly into your guitar amp, this scheme should work, but you would have to rewire any stomp boxes you were planning to use to take advantage of the scheme. Or just use the dual conductor cable between your guitar and the stomp box(es) and a regular mono cable between the stomp box(es) and guitar amp.  
 
    But I like your idea of having a balanced input on a guitar amp! So would the normal hot lead and the signal return lead act as a balanced source? I would guess that it would since the two signals are 180 degrees out of phase with respect to each other— right?  
 
    So how would you wire up a balanced input jack on the guitar amp (preferably without some sort of matching transformer)? I was thinking of two stages of a 12A_7 wired up so that the normal hot lead goes to one grid and the signal return lead goes to the other, with the output being a single lead... kinda like you'd wire them up to the + and - inputs of an integrated circuit.  
 
    Such a setup would be even more incompatible with "normal" stomp boxes, but one solution would be to have two output jacks on your guitar— one unbalanced and one balanced. If you were to use a 1/4" switching jack for the unbalanced output you could wire it up to kill the signal going to the balanced output jack.  
 
    Adding a preamp to the guitar with a balanced output would probably reduce the noise even more, and allow you to run longer cables, but I prefer to run my signal direct from passive pickup to tube grid...  
 
--Thanks!  
 
Steve Ahola  
 
P.S. For those not familiar with John Atcheley's work you can quiet down a guitar by isolating the signal return leads from the various shields. With the stock wiring on a strat, the various shields will pick up extraneous noises from the RF continuum, and then mix them in with the signal (albeit on the grounded end where they aren't as noticeable).  
 
P.P.S. I believe that one company does use two conductor shielded cable for their guitar cords, with the signal return lead connected to the cable shield on the amp end but not the guitar end. Obviously they must have the two plugs marked so that you know which one goes where.
 
5/24/2003 8:51 AM
Dai Hirokawa

I think hi-impedance pickups and inputs partly have to do with tradition. Just the way things went. Les Paul and Bill Lawrence experimented with low impedance stuff, IIRC. Some old amps (Gibsons) have low impedance inputs, I believe.  
 
As for pseudo-balanced wiring, I was thinking that maybe you could also put a small cap inside the (oversized stereo?) plug (maybe a tiny 10nF multi-layer ceramic) between the frame ground and signal ground at the input side. Rewire the amp input using a metal bodied stereo jack, so the frame ground line connects directly to the metal amp chassis at the input (should help dissipate the RF with the cap in the plug). I wonder if you'd have to switch to a different cable for a normal input (maybe the plug, cap and wiring would cause problems).  
 
Steve said:  
 
quote:
"The big paradigm shift is to separate the signal returns "grounds" from the shielding "grounds"."
 
 
This is recognized as a problem in the audio engineering world as a source of noise.  
 
Dai
 
5/24/2003 1:36 PM
Steve A.

Dai:  
 
Steve said:  
 
quote:
"The big paradigm shift is to separate the signal returns "grounds" from the shielding "grounds"."
 
 
This is recognized as a problem in the audio engineering world as a source of noise.  
 
 
    Exactly! Atcheley was evidently an electrical engineer for many years and was wondering why the Fender strat wasn't grounded in accordance to the accepted practices.  
 
    I used humungous caps in some of my guitars to isolate the signal returns from ground, with the cable shield connected directly to the signal return and a 1.0uF or 2.2uF 250v poly cap connected between the signal return and the shields in my guitar (string ground, cavity grounds, pot grounds).  
 
    His later articles suggested that the cap was there just for safety reasons but I think that it helped quiet down the guitars. It was alternately suggested by some readers that a small cap in series with a resistor be used for both safety and noise reasons.  
 
--Thanks!  
 
Steve Ahola
 
5/24/2003 6:10 PM
Brad1

Thanks guys,  
Was just another of those thoughts that pops into my mind about stuff. Sometimes, I wonder if I just like to wonder....  
Anyway, may have to experiment, just to see what happens. Any method of lowering noise in a recording is worth investigating, as all the noise sources alone may not be that bad, but cumulatively, it just makes things more difficult to denoise later without mucking up an otherwise nice sound.  
Brad
 
5/27/2003 12:14 AM
Enzo
Re: Why not balance?
Whatever you decide to do, you owe it too yourself to find the sources of the noises you wish to eliminate. FInd out how much noise is inherent in the amp. How much comes from the guitar itself, and how much comes from the cables. Each source has its own cures. Nothing you do to the cords will affect noise from the guitar or amp. Nothing about the guitar affects the noise from the amp or cord. Nothing about the amp affects the contribution of the cord and guitar.
 

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