Lead dress question

[12AX7]

When ever this subject is discussed, 99% of the time it is concerning lead dress as it relates to hum/noise. But isn't it also just as important for tone?  I'm not sure if it's placebo effect, but i was moving some wires around today and could swear i'm noticing some tonal changes. One i was surprised about and maybe was placebo effect, but i coulda sworn the tone changed for the better when i separated the 2 bias wires that go from the bias circuit to 2 pots on the chassis for my dual bias setup. They were maybe 1/2" apart at one point and mostly parallel. I pulled them away from each other far as i could and it seemed to change the tone to a more open sound. Is that possible with those particular wires? In any case, how big a change can be made by finding the optimal lead dress for a marshall type amp with cascaded preamp?

[alerich]

I can imagine that moving circuit wires carrying audio *might* impact tone - possibly due to alleviating an oscillation that you cannot hear that was negatively impacting the amp's tone in a way you can hear. Since no audio travels through the bias circuit (and it is a largely a static voltage) I can't see how it would impact the amp's operation but you never know. I learn new stuff about amps every day.

[Willabe]

When you said does lead dress makes a difference for tone I would say, Yes, Yes, Yes. It most certainly can and does.

But when you said;

"but i coulda sworn the tone changed for the better when i separated the 2 bias wires that go from the bias circuit to 2 pots on the chassis for my dual bias setup. They were maybe 1/2" apart at one point and mostly parallel. I pulled them away from each other far as i could and it seemed to change the tone to a more open sound."

First off there's not enough information IMO to say what's going on. We have no idea where or what wires those 2 -bias wires where running by.

Second, I would at least twist the 2 dual bias wires together (they are going to opposite phase push/pull tubes) just like heater wires and if I could I would try to run the layout so I could twist the 2 -bias wires with their ground wire. OTOH there's almost no current flowing in the -bias wires to put out an electro static field that could cause problems with sensitive grid wires. But a negative dcv close to a grid wire I guess could mess with the bias of a tube if close enough, ie, laying right on the grid wire or worse yet running parallel to the grid wire. 

1. What amp is it?

2. Please post a schmo drawing of the amps circuit.

3. Please post hi def gut shot pictures of the amp.

This will greatly help you get the information your asking about.


              Brad        

[Ed_Chambley]

Every change made inside an amp will make a difference.  Most of the time these are very subtle, but as alrich mentioned, you could be simply making the amp more stable.

My problem is when I do something and hear a change, I immediately think it is to the good or if it is int I think it is a route to something new and cool.  Most of the time it is not.  Notice I said MOST of the time.  Every once in a while I do find something cool I did not know.

Also, before I get too excited I put the shielding back over the chassis as I use very minimum amount of wax potting on pups.

[stratele52]

12AX7 you are right , I see some change in tremolo sound in Traynor amp . But most of the time is noise issue

[12AX7]

I guess the point is it CAN change tone, but usually only because you're likely fixing a oscillation issue, and capacitance coupling isn't likely unless the dress is really bad. I may have some oscillation issues tho because recently i've noticed a lack of airiness and a more hard strident tone as i turn up thats not how it usually is. I do change things now and then and i may have caused it for all i know.

[jjasilli]

If there is a change in tone then there is a change in waveform.  The only way to really know is to 'scope it, save the screen shots & post it for peer review.

I agree with Willabee: it's hard to believe that separating the bias wires in and of itself would cause a change in tone.  OTOH, the bias wires eventually feed the power tube grids where the bias voltage mixes with signal voltage.  So any noise, etc., induced into the bias leads might get noticed.  Hence moving the bias leads might affect tone, even if the change is not literally caused by their separation.  

However this remains speculative unless it is proven that the change is not merely subjective.