Shielded wire I can’t be liking this

Mongo Park

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I find shielded wire my least friendly part of amp making. It just doesn’t have the mojo I am looking for, the wires are dinky painfully small. One little hair like thread going astray and the whole thing is pooched. I’m not building a amp to go to Mars, weight reduction is minimal here. I’ve tried a few kinds but they seem to be much the same to me.
That is my rant and now back to regularly scheduled amp fun.
 

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Mongo Park

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This is about as good as it gets for me
 

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Phrygian77

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Don't use it unless it's absolutely necessary. Trowing extra capacitance into high impedance circuits is a recipe for tone suck. I've only ever used it on the input of a 3 gain stage preamp, and for an NFB switch located over by the mains wiring.
 

King Fan

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LOL I hear ya, @Mongo Park . On a bad day, it's frustrating. I've had both stray-strand and melt-thru issues, for sure. On a regular day, it often isn't needed, either. On a good day, tho, *when* the stars align and you get into the flow, it's kinda fun, like nano-surgery.

What exact cable are you using? I like the 'real' RG-174, or for more conductors, Rob's suggested "Canare L-4E5C Mini-Star-Quad Microphone Cable", rubbery trivial-to-strip outer coat, easy-to-twist shield, rigid easy-to-strip inner layer. My results aren't pure eye candy, but they work.

upload_2021-12-31_11-9-33.jpeg
 

Mongo Park

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The kind used here is a unknown, somebody recommended it a while back and now it has been sitting on the shelf waiting for it’s chance to Jim into action. I will have to rethink and embrace nano surgery, good idea.
Next idea to consider, not using it. It is a 5f2a going from the plate of V1 to the volume pot about 3-31/2 inches. So maybe not needed Maybe I should build it without shielding and see if it hums and address it if needed. Other threads have brought up the extra capacitance point. Do you think it is needed and would a length of 3” affect the capacitance
it is in now but I will use regular wire to return from the tone stack back to the tube. I don’t use much of it but now and again. This is another issue that falls into the slippery slope of what is needed and what isn’t and do the negative effect outweigh the positive.
thanks for the replies.
 

Lowerleftcoast

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the wires are dinky painfully small
I use a two inner conductor *console wire*. I twist the two wires together so they are not so *nano* when soldering.

I have to laugh...
Merriam-Webster definition of *console*... "I consoled myself with the thought that things could be much worse."
 

dogmeat

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in aviation we use solder sleeves to dress out shielded wire. its no help on the conductor, but attaching a ground jumper is a piece of cake. its heat shrink that has environmental seal at both ends and a band of low temp solder in the middle to make the connection. heat gun makes it work

70101035.jpg
 

chas.wahl

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I have 3 different types of shielded cable (all mono-conductor) on hand here. Haven't used any of them, but this thread prompted me to partially dissect and compare them:

upload_2021-12-31_16-44-16.png


On the left is RG-174 from Hoffman, RG-316 from ApexJr in the middle, and on the right "MIL-C-27500 Shielded" from Aircraft Spruce (item # 11-14422).

RG-174 is 0.112" OD (2.85 mm); RG-316 is 0.098" OD (2.5 mm) and the 14422 stuff is 0.078" OD (2 mm). The 14422 is ETFE insulated, both inner and outer sheaths, and has 85% coverage. I don't know the comparable specs for RG-174 and RG-316, but the former seems to have soft insulation on the outer sheath, while both of them seem to have more resilient inner insulation, like nylon or PTFE.

Both RG-174 and RG-316 have what appears to be 25 gauge stranded conductor (about 0.02 OD when twisted -- obviously the RG-174's is not tinned. Despite being smaller in overall diameter, the 14422 stuff has 22 gauge conductor, and it's stiffer and holds together better than the conductors for the RG types. I found it somewhat easier to strip (both sheaths). The two RG types are sort of "floppy" but with a mind of its own in the way that braided wire is, compared to solid, while the 14422 stuff is somewhat more "conformable" and more willing to take a shape. I think that may be because the core conductor appears to be not only tinned, but what I imagine what "topcoat" stranded wire is like: the conductor seems stiffer than normal stranded. The braid shield on it is fairly easy to unbraid, perhaps less "full bodied" than that on the RG types, but without falling apart (losing strands.

Overall, the 22 gauge conductor seems like a winner to me. Aircraft Spruce sells this type of cable in other gauges (24 through 6) and also in multi-conductor versions (2-9) in the smaller gauges.

Here's a link to Aircraft Spruce's page for these cables, which also has a PDF data sheet for the stuff:
https://www.aircraftspruce.com/catalog/elpages/shieldwire.php

In 22 gauge mono, it runs $1.10 a foot currently.
 

Timbresmith1

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Belden Teflon jacket like EMG pickups use. That or the Gibson 2-conductor metal braided stuff- I just slide 1/8” heat-shrink tube over it and go.
 

Bill Moore

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Back in the day all of us used high impedance mics. The cords were small and I've been using them for my shielded cable needs. I guess I should figure out what wire they used if I should ever run out.
 

echuta13

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I've been pretty happy with Canare GS-4. It's not bulky, and it seems to take heat okay plus the shield is copper so easy to solder to.
Never fun to deal with this type of cable, but it's insurance IMO.
 

mcentee2

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Just extended this topic..

Apart from the input to a faint preamp first stage, where else can shielded best add value?

I have seen it on NFB back from the speaker output to wherever it connects to the PI or easier stave cathodes.

Anywhere else?

Where is it overkill and just not needed at all?
 

The Ballzz

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I like Belden 8451. #22 gauge, red & black inner conductors with a "drain" wire, full coverage foil shield and 75°C/164°F rated! Sturdy, insulation doesn't melt like wax when you solder it! Small diameter profile and no unbraiding! Can be found fairly cheap as roll end cut offs, otherwise $.28 per foot at Full Compass.
Just Wiring'
Gene


IMG_0614.jpeg
 
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The Ballzz

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Just extended this topic..

Apart from the input to a faint preamp first stage, where else can shielded best add value?

I have seen it on NFB back from the speaker output to wherever it connects to the PI or easier stave cathodes.

Anywhere else?

Where is it overkill and just not needed at all?

Works well from treble pot to passive effects loop and back to the master. Pretty good for to & fro a post phase inverter master volume pot. Fairly unnecessary in most other locations.
Just Shieldin'
Gene
 

jhundt

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Back in the day all of us used high impedance mics. The cords were small and I've been using them for my shielded cable needs. I guess I should figure out what wire they used if I should ever run out.
I have a box full of old stereo hookup cables, you know, the kind with two cables, red and white rca plugs on each end. I just cut pieces off of them when I need shielded wire. But as others have suggested, I only use a few inches of the stuff in a normal amp build..
 




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