Shielded Cable

[crgfrench]

Anyone have preference between Mogami vs Belden or others for the shielded lines?
https://s3.amazonaws.com/tubedepot-com- ... 1521736870
vs
https://www.mouser.com/ProductDetail/Be ... vi5uyZQ%3D

[JMPGuitars]

IMO Mogami is hit or miss, and usually overpriced. I recently made the mistake of buying some of their tube mic cable. It was TERRIBLE.

I usually go for silver plated mil spec PTFE. I don't generally get caught up on which brand (unless I have a bad experience, and then I avoid it).

[crgfrench]

This 20G Belden is available at AES for $2 per foot, a little more than twice as expensive as the 25G Belden in my OP.
https://www.tubesandmore.com/sites/defa ... s-ws20.pdf

[AussieTim]

You must have read my mind I was doing the same research myself. One thing I have noticed is the Mogami is rated to last 15 seconds at 500volts whereas the Belden has a rating of maximum 300 volts also the impedence of the Belden is a lot higher than the Mogami which could affect tone etc

[JMPGuitars]

High-voltage leads don't need to be shielded. The point of the shielding is to protect the lower-voltage leads from interference.

If shielding adds impedance, how good is the shielding on one claiming to be lower impedance? Is that same cable still lower impedance without the shielding when comparing the two? What about the cable capacitance?

[crgfrench]

High-voltage leads don't need to be shielded. The point of the shielding is to protect the lower-voltage leads from interference.

If shielding adds impedance, how good is the shielding on one claiming to be lower impedance? Is that same cable still lower impedance without the shielding when comparing the two? What about the cable capacitance?

From the datasheets (I did some conversions for the 9434):

The Belden 7805 is solid copper
DCR= 41 Ohm/1000ft (includes core + insulation)
Capacitance= 31.2pF/ft
Inductance= 0.077uH/ft

The Mogami 2368 is stranded copper
DCR= 99 Ohm/1000ft (includes core + insulation)
Capacitance= 107pF/ft
Inductance= 0.092uH/ft

The Belden 9394 is stranded copper
DCR= 19 Ohm/1000ft (includes core + insulation)
Capacitance= 54.9pF/ft
Inductance= n.a.uH/ft

[JMPGuitars]

Higher capacitance = not as good. You shouldn't use solid core wires in amps. Stranded wire only, unless you're using a 12AWG copper wire for the bus...and personally I think that's overkill.

Capacitance is the ability for a body to a hold a charge, right? So if the cable is more likely to hold a charge (higher capacitance), what is the affect on the signal (charge) passing through it?

[JMPGuitars]

You must have read my mind I was doing the same research myself. One thing I have noticed is the Mogami is rated to last 15 seconds at 500volts whereas the Belden has a rating of maximum 300 volts also the impedence of the Belden is a lot higher than the Mogami which could affect tone etc

You're reading that information incorrectly. The Belden shows 300V RMS. That doesn't mean peak like the Mogami is showing. RMS (Root Mean Square) is the average voltage a cable should be able to handle CONSTANTLY. 15 seconds at 500V shows what the Mogami cable can handle before it breaks down / becomes a problem. They don't appear to show the RMS value for the Mogami cable.

BTW- I don't think either of these cables are ideal for amps because of the rubber insulation. Personally I prefer PTFE (teflon), but you may find the wire okay.

[AussieTim]

Is twisting wires enough to provide some shielding I have an amp that I acquired as a project it has a lot of additional controls such as presence and resonance and different voiced pre-amp switching, that while fun to play with creates a lot of noise, it is also point to point wired which I do not know if contributes to extra hums etc over a turret board mounted circuit, does make the circuit a little harder to follow. Whoever built it has used screened cable but it looks low grade and has some terrible soldering, I was thinking of working through it and replacing the cable with better quality stuff and tidying up the soldering, lead dress and layout and see if it quietens down the overall noise. Failing all that I was thinking of stripping it down and rebuilding it as a straight 18 watter like Richies TMB a SIII or similar

[JMPGuitars]

Is twisting wires enough to provide some shielding I have an amp that I acquired as a project it has a lot of additional controls such as presence and resonance and different voiced pre-amp switching, that while fun to play with creates a lot of noise, it is also point to point wired which I do not know if contributes to extra hums etc over a turret board mounted circuit, does make the circuit a little harder to follow. Whoever built it has used screened cable but it looks low grade and has some terrible soldering, I was thinking of working through it and replacing the cable with better quality stuff and tidying up the soldering, lead dress and layout and see if it quietens down the overall noise. Failing all that I was thinking of stripping it down and rebuilding it as a straight 18 watter like Richies TMB a SIII or similar

Twisting bad wire connected to bad solder joints won't fix anything, especially not where the voltages are low. PTP wiring doesn't make things good or bad; the quality of the work does...but if there's a turret board, it isn't really PTP (same story though, quality of work and lead dress matter most). It sounds like you've got the right ideas to move forward with. Take photos and such so you know where it started.

[geoff 1965]

AussieTim,
this sounds like an interesting project,if you decide to rework/rebuild keep us posted with your progress and create a new topic post for it.if you could add some good close up pics it helps,someone might spot something regarding the noise.
good luck

[AussieTim]

Sorry JMP I did not mean twisting the existing wires, I meant replacing the existing wires with a twisted pair and was curious as to the effectiveness of doing so or if I am better off getting some shielded gear, hence my interest in the subject of shielded wires.

[JMPGuitars]

Sorry JMP I did not mean twisting the existing wires, I meant replacing the existing wires with a twisted pair and was curious as to the effectiveness of doing so or if I am better off getting some shielded gear, hence my interest in the subject of shielded wires.

Wire twisting is most helpful on high voltage / AC leads. On low voltage input/preamp leads it doesn't do anything for you except maybe look pretty. Not all preamp lines need shielding. Input jacks, and higher gain leads like the gain knob, do benefit from shielding. Besides that, it depends on the lead, and its proximity to interference whether or not shielding adds any benefit. Looking at different layouts might give you an idea of where shielded wire is normally used.

[AussieTim]

Just wondering how important is the fatness of the shielded cable I know that around 20AWG is usually recommended but I can get hold of some 16AWG shielded cable which is mil grade, Is there any advantage or disadvantage of using thicker cable

[JMPGuitars]

Just wondering how important is the fatness of the shielded cable I know that around 20AWG is usually recommended but I can get hold of some 16AWG shielded cable which is mil grade, Is there any advantage or disadvantage of using thicker cable

You don't want thicker cable. Thicker cable is harder to work with, and can actually add to noise issues. The heaviest you need is 20AWG, but some people like 18AWG for the heaters (obviously not shielded here). There's generally no need to actually go above 20AWG as the voltage and current are well below what quality 20AWG can handle. I think most Marshalls had/still have 22AWG for the heaters, so that gives you an idea.

Thanks,
Josh