Teflon coax cable

[Mark]

I like the way HAD attaches the shield of the coax to the case of the particular pot. The trouble is the cable needs to be Teflon so it isn't destroyed by heat.

Where do you guys get good quality Teflon cable?

[sluckey]

I use RG-316 from eBay. About 1/8" diameter. The center conductor has PTFE (Teflon) insulation. The outer sheath is not PTFE but it is very heat resistant. You can lay a soldering iron on it for many seconds before leaving a mark. This cable is fairly stiff and does not do sharp 90° bends well. I use it in all my later builds. Here's an example...



And here's a link...
https://www.ebay.com/itm/25ft-RG316-Bul ... 910476babd

[Mark]

Thanks for the advice Sluckey, I appreciate it.

[talbany]

I like the way HAD attaches the shield of the coax to the case of the particular pot. The trouble is the cable needs to be Teflon so it isn't destroyed by heat.

Where do you guys get good quality Teflon cable?

Hey Mark
I get all my coax at Steve at Apex JR has the PTFE in both RG188A/U (white) & RG316. I've used the 188A in several builds and works great,not too big,flexable,and easy to work with right to the back of the pot

BTW.Steve is very reasonable and shipping is the next day. Great to work with! (He is in L.A Cal)
http://www.apexjr.com/wire.html
Tony

[telentubes]

Same as Tony. Apex Jr.

[rootz]

What would you say is the most desirable quality of good coax or shielded cable? Low capacitance? And would you use the same low capacitance cable through the whole amp or a higher capacitance one OD? How did HAD think about this subject?

[norburybrook]

What would you say is the most desirable quality of good coax or shielded cable? Low capacitance? And would you use the same low capacitance cable through the whole amp or a higher capacitance one OD? How did HAD think about this subject?

IMHO, the cable runs are so short that I don't think the capacitance makes a lot of difference. With a 25 foot guitar lead yes, but 6 inches?

Most coax I've used is 75 ohm , not sure about capacitance. It traditionally was used in TV, cable scenarios and in pro audio for digital transmission of signals like word clock or AES-EBU.

there are plenty of high end cable manufacturers making great shielded cable, in the UK I always use Van Damme cable if possible, not hugely expensive but high quality, it's what all the top studios in London are wired with. They do a whole range. In the US you have Belden of course and not forgetting Mogami,Canare.

I've never managed to perfect the way Dumble soldered the shield to the back of the pots so I always wire the shield to the bus bar, to be honest if you need to change pots to experiment with skyliner/classic EQ's then you'll be glad they're not soldered to the pots

Again Just my perspective from my limited experience with all this.

M

[talbany]

What would you say is the most desirable quality of good coax or shielded cable? Low capacitance? And would you use the same low capacitance cable through the whole amp or a higher capacitance one OD? How did HAD think about this subject?

Rootz
I can't obviously speak for Dumble but I treat the coax the same as I would in selecting a certian resistor type or a particular capacitor dielectric. In most (well constructed) amps it would be considered a nuance, some ears hear it and others not much. Of course this mainly affects the treble frequency or top end clarity. Too high a capacitance and the amp can sound lifeless, too little capacitance and the OD can get bright or harsh (especially the low plates!). Again it's the sum of all parts working together as well as other external factors like an effects loop interfacing along with the added cabling that goes along with it. High capacitance cables are also an easy way to fine tune a bright sounding amp and have heard some players purposely extending their cable lengths on the D-Lators to shape the treble response.. IMO The Non HRM amps are the most difficult to build because there are no RC networks to bleed off highs (Apart from the snubbers) in the overdrive section so your left with the natural sound of all the components (including pot's and resistors,coax) to shape the overall sound, so some attention should be paid to the cable's capacitance ratings as well..

So far my 2 favorite in these amps are RGU-59 has a C rating of 20Pf per foot
The next would be the 188 which is rated at 29 Pf per foot for a slightly flatter top end
For me? As long as the amp is free from any harsh odd order overtones (due to my parts selection,layout and circuit constants) I generally want to retain as much top end clarity as possible. Basically if the amp is smooth and musical sounding I don't mind it being a little bright as long as the transition from clean to OD stays as transparent as possible and that way leave my bright switch off.
This is how I go about it.

Tony

[Todd Hepler]

Another Apex Jr. user here.
I also got Bourns pots and PTFE Hookup wire from Steve as well. Great stuff with great prices!

Here's an all loctal/octal ODS with apex teflon wire:

lucky guts.jpg

[Mark]

I've never managed to perfect the way Dumble soldered the shield to the back of the pots so I always wire the shield to the bus bar, to be honest if you need to change pots to experiment with skyliner/classic EQ's then you'll be glad they're not soldered to the pots.

Marcus, I can't say if I perfected that technic, but I had to use an electricians soldering iron to get enough heat into the joint. I first tinned both surfaces, the coax first and the pot last so it is still hot and I put the coax on the pot and fed solder into the joint. It's best done outside the amp. I think HAD's logic for doing this was the coax is held firm and there is no breakage, the other thing is the earth connections are on the chassis and not his earth lines. That is my take for what it is worth.