Should I screen ALL signal wiring ?

[pedro]

some seem to, and some dont .

I want to know whether I should use good coax/screened to screen all signal wires coming from the board to the tone and OD controls on the panel.

Simpler not to but wondered if its essential.
Its such a fag to earth each wire at one end and it often gets cramped.

Ive noticed on some layouts that only input to first tube triode is screened and rest is just pvc coated etc.

Dilemna !! and Ive nearly finished my build HELLPPPPP !!

cheers
Pete C

[llemtt]

Beware pedro, this has a huuuge impact on tone!

I suggest very low capacitance shieded cable from volume pot to v1b grid.

Teo

[Normster]

This topic has been hotly debated a few times on other forums. I guess the general consensus is that shielded cable is a tone sucker. Also, many builders seem to recommend RG174/U over the expensive Beldon coax.

I use very little shielded wire. Input, Volume, and OD (drive & level)...that's it. I use RG174/U because it's cheap and easy to work with.

I suppose you could use shielded cable to your advantage to tame an amp with an unruly top end.

[glasman]

My opinion is to use as little as possible. The more you use the more hgh end you will use.

Take a look at my web site for a discussion on my experiences.

Gary

[pedro]

OK,
so if I do input, vol CL and OD runs with low cap and then do the off board wiring to everything else with single core I'm OK ?? just seemed like longish runs from the CL tone network on the board to the panel pots thats all ?

I'll try it with this combination and then if I'm getting noise I'll go shielded/low cap coax.

cheers fellas

Pete C

[Normster]

just seemed like longish runs from the CL tone network on the board to the panel pots thats all ?

I keep the 3 wires twisted and run them in the front corner of the chassis and have no issue with noise. Also, the run is a lot shorter than you might think if you use the Dumble-style layout.

[oldmacman]

The OD Reverb layout shows quite a bit of coax, as do the pics of #40. Helps tame the highs without any plate-cathode caps on V2A and V2B.

However, the pics of the guts of '80s and '90s Dumbles I've seen show much less.

[Bob-I]

I did that on a build and found it to be dull and lifeless plus the treble control appears to be disabled. I selectivly removed coax and found that the brightness returned and the effectivness of the treble control returned. Today I have coax only on the grids of CL1 and the power tubes. She's quiet and sounds great.

Even short runs of coax can have a few pF that can add up and suck out the top end. If you're careful with the lead dress you can make an amp quiet without any coax but a little selective use of coax can make it even quieter or even remove an oscillation

[pedro]

As I have some long runs due to my test chassis being very large , I panicked a bit and used quite a bit of low capacitance coax for the signal runs.

I figure if its lossy on the highs then I will go round and selectively lift the grounded shield ends until I'm happy that there isnt any crosstalk and oscillation using just the stranded core wire inside the original coax.

ahem, its obviously not a clone, but I like the industrial look of this one !!!

Pete

[Bennypapa]

Where do you usually buy your coax?

Mouser has it of course but who needs 100ft?

If I use 2 or 3 feet per amp that would last me 30 amps. If I built all the amps I ever even wanted to build

1 dumble
1 18watt marshall
1 jtm45
1 trainwreck
1 fender/marshall 50 watt
1 november

Well you see my delimma.

I only need 10 or 20 feet for a lifetime of builds.

While I'm on the subject and in the middle of a threadjack anyway, Whose hookup wire do you like?

AES has some nice looking wire in lots of pretty colors.

Bennypapa

[oldmacman]

Teflon covered wire from Apex Jr. has always done great for me.

[glasman]

Where do you usually buy your coax?

Mouser has it of course but who needs 100ft?

Bennypapa

Well you could use good ol' Radio Shack CATV coax. 75 ohm cable is pretty low in capacitance and cheap. RG-59 is a little big, but no bigger than the Gepco stuff that I used in my 3 amps.

Best part it is cheap! and by the foot.

Gary


You know I just checked the RS online stuff and I could not find bulk coax listed. Check your local stores.

[Normster]

Where do you usually buy your coax?

Mouser has it of course but who needs 100ft?

Just buy 100 ft and donate the other 80 ft to your friends here...or sell it by the foot. Just kidding!

I actually found a place that sells RG174/U by the foot, 14 cents a foot. Unfortunately, shipping was going to be $8 so I ended up ordering 100 ft anyway just out of principle. It was just as well since I've ended up using a lot more of it than I ever thought I would.

[Dai H.]

weaker high impedance runs are more susceptible to outside influence (which includes noise). So the input stage grid should give the most benefit. It isn't necessary to use it on every single run. You should try to figure out what is going through what wire. AC, DC, signal levels, the impedance. Then it should be self-evident. As far as losing highs, think about where the series R and R to ground is on that line. If you have a series R and R to ground (as a pot) and put them earlier, as you turn down the pot, the signal becomes more high impedance and more susceptible to nearby signals, noise, plus effects of cable capacitance if you use a shielded cable after that point (due to the capacitance "hanging" from hot to ground). How you use or don't use these factors may be one of the "mojo" factors differentiating one person's build from another. And I would be careful in assuming the more frequency response the better. More say, at the input could mean more susceptibility to RF noise coming in and I don't think this is typically desirable. Think about the subjective stuff. Some people say the passive pickups to the amp, the traditional high impedance line are part of the sound that people like, but then there other approaches like EMG, buffering lower impedance which should negate the effects of cable capacitance. There's the matter of personal preference, so "right" and "wrong" may not be.

[toneman]

27001RG174 100' $16.00 -- google (Electronix Exspress) 8.00 for shipping also . I thought that was a deal Where did you find the 14 cents a foot at. I'd buy that in a heart beat. Always tweaking