Does shielded wire really kill your tone?

[noworrybeefcurry]

Ive read somewhere once that using shielded cable absolutely kills your tone. Is there some truth to this, or am i reading to far into it?

[Structo]

That is kind of a broad statement.

Your guitar cord is shielded cable.

It really depends on the cable and where it's used.
All shielded cable has capacitance, it's like a long capacitor.
Shielded cable has a capacitance value per foot.
The longer it is the more capacitance there will be.

If is too much it can make the tone muddy and not clear.

As far as using shielded cable inside an amp, many amps didn't use it, especially vintage amps.
But we found that by using it in key places it can cut down on noise and coupling.

So my advice is to use good quality guitar cables (low capacitance) and only use shielded cable where it is needed inside the amp.

[noworrybeefcurry]

I was mainly concerned with the shielding inside of the amplifier. I have a 183 clone that i built into a large chassis (probably not the best idea in hindsight) so long wire runs were hard to avoid....I have shielding on all the grid wires except V1B as well as on both legs of the master volume pot. But when i have the gain set to anything but low i am getting a lot of excess noise. Is it safe to add more shielding? or will i be compromising the core tone?

[sonicmojo]

I would think shielding, especially in a 183, would help in general without compromising tone. What kind of noise are you hearing? If it is strictly hiss you are hearing, I'm not sure it would be a huge improvement with the shielded cable. My 183 was the noisiest amp (hiss wise) compared to others even with the coax where it was called for. It wasn't excessive, but just not really quiet like my Bluesmaster or 3rd gen amps. It comes with the territory a little on the higher gain circuits (which is what I consider 183 in the Dumble context) but if you think it is excessive, you may want to go ahead and try a few things.

[David Root]

I don't use shielded runs as much as I used to. Input jack to V1A grid, Vol. pot wiper to V1B grid, then only for long runs >6" or so if I can get away with it. But they do have their place IMO.

Building a tweed Twin, which has quite long runs and nooo shielded wire anywhere, and is dead quiet, is what convinced me to minimize use of coax.

Of course that is not comparable gainwise with any high plate Dumble.

I have recently found that older resistors, like Piher CFs and Mepco/Electra metal films for example, seem to moderate the highs that can be aggressive with new resistors, especially some newer/cheaper metal films, without stripping out any desirable content. Unfortunately these are getting hard to find and more expensive, especially the Pihers.

[sparrott]

I built a high gain preamp a couple of years ago that required some shielding and it was very apparent that there was some tone loss when using shielded cable. I started replacing the shielded cable with twisted pair wire one run at a time and there was an increase in clarity and note definition. It sounds odd but it had more pronounced effect on the later stages where there was larger voltage swings.

[noworrybeefcurry]

sonicmojo-

Sorry, i should have been more clear..the kind of noise i am hearing is the kind of feedback you would hear with a modded marshall or old boogie that has the gain maxed and your just holding the strings down...and dynamically when i play, it feels like a wild, piercing feedback that you cant tame regardless of the volume level.


David Root-

Where would be the best place to find those older resistors? ebay maybe?


sparrott-

What sort of tone loss did you hear?

Also, how do you prepare and install the twisted pair wire? is it as simple as using one conductor as the hot lead and grounding the other conductor?

[ToneMerc]

I was mainly concerned with the shielding inside of the amplifier. I have a 183 clone that i built into a large chassis (probably not the best idea in hindsight) so long wire runs were hard to avoid....I have shielding on all the grid wires except V1B as well as on both legs of the master volume pot. But when i have the gain set to anything but low i am getting a lot of excess noise. Is it safe to add more shielding? or will i be compromising the core tone?

Sorry, i should have been more clear..the kind of noise i am hearing is the kind of feedback you would hear with a modded marshall or old boogie that has the gain maxed and your just holding the strings down...and dynamically when i play, it feels like a wild, piercing feedback that you cant tame regardless of the volume level.

Here's my 2 pennies; across all the different Dumble voicings and regardless of "generation" there's a common build architecture. It lies in layout, grounding scheme, lead dress and power supply topology for starters. When done correctly these amps are dead quiet and hiss free other than maybe an open FET circuit.

If you you radically deviate from these it is not a clone, nor is it even fair to begin to label it my "xxx" or "xxx clone", in reality it's just a circuit you built. Nevertheless, one can take the circuit an apply it in alternative layouts, but in a sense you would be starting from zero, your own baseline.

IMHO, you need to address your issues from the root cause as using additional shielded cable and vintage CF resistors are normally tuning aids, not band-aids. So the question is, why exactly is my circuit behaving this way? I would analyze my lead dress and circuit layout before I chase more shielded cable and using vintage resistors.

Now you have a nickel.

TM

[Structo]

Also the tubes you use in V1 and V2 can have an affect on the hiss level.
A high gain 12ax7 in V1 is most likely going to raise the hiss level a bit when you turn up.
Tony mentioned he has a V1 with a 90 mu in his 102.

[caphead]

I had a thought on this topic .... What if there was thicker insulation between the shield and the inner wire? In theory wouldn't that reduce capacitance if the distance between the shield and lead were increased? The type of wire I can think of that best meets that specification would be braided co-ax (like what Gibson guitars used to wire their pickups, the type with thick old style wire rubber insulation).

[martin manning]

The dielectric constant of the inner insulation comes into play also. Low-capacitance co-ax cable, say 20 pF/Ft, can be small, 3-4mm/~1/8" and cheap high capacitance cable can be quite large. The shielded runs are pretty short, generally 6-8", so you are only adding ~10 pF to ground, which is not going to bleed much audio frequency, and it isn't much different from a plain wire lead running along the surface of the chassis. Some people think low-capacitance cable actually makes the amp too bright.

[diagrammatiks]

just be aware that depending on how you ground and route the shielded wire the capacitance can have a much bigger effect.

shielded wire used in guitar amps is not really comparable to shielded wire in an instrument cable.

With an instrument cable the shield braid is an essential part of the circuit. It acts as the ground return for the guitar and it runs all the way to the amp where it gets grounded with the amp grounds.

If you just use a ground shield inside the amp that is grounded at one end and is non essential for the ground returns then you will get significant capacitive coupling.

[martin manning]

If you just use a ground shield inside the amp that is grounded at one end and is non essential for the ground returns then you will get significant capacitive coupling.

I don't follow, diagramatiks. Can you explain how the capacitive coupling to ground will be other than the capacitance per unit length times length?

[diagrammatiks]

If you just use a ground shield inside the amp that is grounded at one end and is non essential for the ground returns then you will get significant capacitive coupling.

I don't follow, diagramatiks. Can you explain how the capacitive coupling to ground will be other than the capacitance per unit length times length?

It has to do with function the shielding is acting in the circuit.

You can think of it as whether it is essential or inessential to the circuit.

For an instrument cable you cannot omit the second conductor. Therefore there is always capacitive and inductive interaction between the two conductors.

In that instance, depending on what the conductor carries, different arrangements of the conductors will maximize or minimize the unavoidable effect.

In the case of instrument cable that is running the ground return as a shield braid. For speaker cable it would ideally be a twisted pair.

Alternatively for instrument cable you could if you wanted to run 2 separate and equal conductors and moving those conductors around, increasing their distance from each other etc would have effects on noise pickup, signal losses, etc.

Using shielded wire in a guitar amp is usually a totally different set of maths. The shield in this case is non essential, meaning that it does not act as the ground return, does not complete a circuit, and is only grounded at one end, usually.

In that instance any coupling is additive to the circuit rather then necessary for the ground return.

[Max]

...using shielded cable absolutely kills your tone. Is there some truth to this...?

IMO discussions about questions like this one sometimes have a tendency to mix up (at least) three IMO rather different topics:

1 - Do different technical specs - like the kind of cable / wire used - correlate with measurable differences in the way the signal present at the input is processed?

2 - Do different technical specs - like the kind of cable /wire used - correlate with differences in the human perception of timbre and feel etc?

3 - What kind of perceivable timbre and feel etc. does some individual guitar player or a majority or minority of guitar players personally like or dislike based on personal taste and current "fashion" etc?

Cheers,

Max