Wrapping versus shielded cable?

[BobW]

Did HAD use something like RG318, or 178, 179? this stuff is a small version of RG59 (about .125" dia) but with a much lower capacitance/ft. I acquired a 50' roll of RG178 for a bargain and use it for any shielded cable in the chassis, and well, it works for me, no problems with loss of dynamic range using this stuff.

['67_Plexi]

Funny how people get hung up on the high frequency attenuation from a couple of feet of sheilded cable on the inside of the amp, when we connect to them with up to 50 feet of the stuff from the guitar, and that's without even considereing any effects pedals that may be in the chain.

There are however a number of of other strange effects that can happen using sheilded cable all over the place, but on the other hand unsheilded cables can lead to a noisy microphonic parasitic amp from hell.

When I plug my old '59 Les Paul Special into this amp, those ancient P90's found every possible unstable weak area. A few shielded runs quietened it down consideralbly and is the best of two evils.

I got away with using it in small runs on the grids of V1 and V2 and thats really about it. Looking at the Dumble pics, he seems to use it in more places.

Personally with the small runs I have I can't hear the difference between good quality audio grade and coax. Maybe on longer runs it might be more evident.

Bottom line, don't ignore it and go crazy with the stuff, but equally don't get too hung up about it either, there's a whole myriad of more important areas that have a much bigger effect on the tone.

[dogears]

I totally disagree..... I have swapped each and every piece of coax in my amp to unshielded and have heard a difference in each case. I have abotu 4 pieces in there now..... Also, Belden shielded is CRAP. Please don't tell people that it is OK. 67pf per foot!!! Gary Johnson will concur with me.... Amp lost all of the 3d shimmer and chime with it. All of it. After swapping it, it all returned! There is a reason Dumble used very good quality cable.

Funny how people get hung up on the high frequency attenuation from a couple of feet of sheilded cable on the inside of the amp, when we connect to them with up to 50 feet of the stuff from the guitar, and that's without even considereing any effects pedals that may be in the chain.

There are however a number of of other strange effects that can happen using sheilded cable all over the place, but on the other hand unsheilded cables can lead to a noisy microphonic parasitic amp from hell.

When I plug my old '59 Les Paul Special into this amp, those ancient P90's found every possible unstable weak area. A few shielded runs quietened it down consideralbly and is the best of two evils.

I got away with using it in small runs on the grids of V1 and V2 and thats really about it. Looking at the Dumble pics, he seems to use it in more places.

Personally with the small runs I have I can't hear the difference between good quality audio grade and coax. Maybe on longer runs it might be more evident.

Bottom line, don't ignore it and go crazy with the stuff, but equally don't get too hung up about it either, there's a whole myriad of more important areas that have a much bigger effect on the tone.

[llemtt]

Shield capacitance only matter where the source impedance is high, luckily pickups are at 20k max so driving few meters of good cable is not a problem.

There are mainly 3 places inside D amps where shielded cable capacitance has huge impact

from vol wiper to V1b grid resistor, it's only few inches but you can hear it

from v2a to drive pot to v2b, here impedance is very high, think the 100k resistor...

from v2b to master pot, here again impedance is very high, think the 150k resistor in non-HRM...

I can tell you for sure, use a 100pf/foot cable in the OD section, like I did, and it's like putting 1500-2000pf snubbers!!

I think HAD used RG58 (probably teflon) in most of the golden era amps and maybe switched to something like RG174 later

teo

['67_Plexi]

OK, I stand corrected, you are totally correct about the source impedance, never even thought of it.......talk about missing the obvious.

I also have never used Belden sheilded cable.
I have a whole load of sheilded cable that came from a couple of 1950's hi-fi amps that is the best quality audio cable I have.

I guess I was comparing apples and oranges. Sorry if it was misleading

[glasman]

OK, I stand corrected, you are totally correct about the source impedance, never even thought of it.......talk about missing the obvious.

I also have never used Belden sheilded cable.
I have a whole load of sheilded cable that came from a couple of 1950's hi-fi amps that is the best quality audio cable I have.

I guess I was comparing apples and oranges. Sorry if it was misleading

Take a look at my website under the Clone Project. I ran into some serious problems using Belden shielded cable. There are a few graphs and charts of measured effects.

www.glaswerks.com/cloneproject/clone_project.htm

Gary

['67_Plexi]

Nice work bro !

I actually picked up some RG-58 co-ax today after reading this thread.

One thing I learned is that there is RG-58 and there is RG-58...... the cheaper the better !!! The cheapest had the lowest capacitance per foot (around 18pF). THe most expensive was over 30pF. I guess what you gain in response you lose in shielding. Physically it was the quality and wrapping of the screen that was the main difference. The looser and the less of it the better it seems.

[glasman]

Nice work bro !

I actually picked up some RG-58 co-ax today after reading this thread.

One thing I learned is that there is RG-58 and there is RG-58...... the cheaper the better !!! The cheapest had the lowest capacitance per foot (around 18pF). THe most expensive was over 30pF. I guess what you gain in response you lose in shielding. Physically it was the quality and wrapping of the screen that was the main difference. The looser and the less of it the better it seems.

That is probably why HAD used TANDY RG-58 in early amps. Not much shield so the capacitance would be lower.

Gary

[tonelab2]

Thank you gentlemen, the last few posts confirm my line of thought on shielded cable. I was pondering on the difference in the physical appearance of the shielding itself and the effect on capacitance, It's seems the cheaper shielding has less capacitance but is it's ability to stop unwanted interference any less? what is the trade off? I'm guessing the less shielded the better, as long as we have good layout .

[llemtt]

.. I was pondering on the difference in the physical appearance of the shielding itself and the effect on capacitance, It's seems the cheaper shielding has less capacitance..

Don't be misleaded, this is somehow true when you compare the same cable type (RG58 for instance) made by different producers, otherwise usually the cheaper the cable the higher the capacitance...

teo

[mogo]

-> tonelab

87pF per foot is common spec for audio quality shielded cable, it will round your highs in a significant way
-> Gary

Teo

Lets not forget that Capcitance in itself will not round off anything.
It depends on the driving impedance. So it all depends where this capacitive cable is. You can also use this to your advantage everyone likes to knock off some highs here and there. Wrapping a wire with a grounded wire might have a little less capacitance but it is a pain to do and does not have the shielding properties.

[skyboltone]

Did HAD use something like RG318, or 178, 179? this stuff is a small version of RG59 (about .125" dia) but with a much lower capacitance/ft. I acquired a 50' roll of RG178 for a bargain and use it for any shielded cable in the chassis, and well, it works for me, no problems with loss of dynamic range using this stuff.

I have no idea what he used but 178 is common and about 1/8" in dia. It's characteristic impedence is 50 ohms, (we don't care) and I don't have my belden catalog here. I think it's pretty low cap wire though.

[ApexJr.]

Hey Ayan...
My old stomping grounds, my brother is running Apex with my sister
and Mother. Went on my own 13 years ago. Worked there 20 years +
Glasman... Gary if your going to be in Burbank you can also look
me up too. Since I'm a one man operation give me a call and set
a time to meet me at my warehouse...

Bob W and the Rest:
I have in stock RG 178A/U 50 Ohm teflon coax at .25ft $20.00/100ft
RG 316/U 50 ohm coax at .40ft $35.00/100ft
20 Awg 1 cond shielded Teflon w/ silver plated braided shield .25ft
22 Awg 1 cond shielded Teflon w/ silver plated braided shield .20ft

Steve @ Apex Jr.
www.apexjr.com

[BobW]

thanks for the info ApexJr,