More coax talk

[dcribbs1412]

Sorry to beat a dead horse
trying to figure out which coax to use
any comments on using this coax
for internal runs
http://www.gepco.com/products/proav_cab ... flex_F.htm

[Structo]

Even though that is low pf cable, it is made for digital transmision so for very high frequencies above 1MHz.

Plus you don't want super low pf cable or it will be harsh sounding.

Something around 25-30pf/ft is usually good.

The mil spec Teflon cable is the best stuff to use.
It won't melt back when soldering either.

You can find it on Ebay or Apex Jr. usually has a good supply of it for cheap.

http://shop.ebay.com/items/shielded%20t ... 2389484494

http://www.apexjr.com/wire.html

[dcribbs1412]

Thanks Tom
funny you mention harsh sounding
I've been fighting a harsh sounding build full of this type of wire

Darin

[fp2000]

Is RG-178 what we are supposed to use? I remember something about it but I can't remember

[stelligan]

Something around 25-30pf/ft is usually good.

I used Gepco VDM230 in the 183 I just finished. That may explain what I am hearing. Too much high end hash. Just looked it up - its 16pf/ft.

Maybe I should install Gil's tone cut?

[67plexi]

If I recall the Tandy foam core coax HAD used was 50pf per foot.
I may be wrong.
I scored this 50pf Teflon pure silver coax mil-spec. it’s a bitch to work with but sounds great.
It kills RG-174 no comparison. Got it for $5.00 for 50’ now with the price of silver it’s $100.00 per foot.
That’s what the high end Hi-fi suppliers want for it now.
I rewired all 4 of my ODS amps with it sounds smooth as silk.

[dcribbs1412]

I've got some Canare stuff coming
I think its around 30pf/ft...may mix some cable runs.
Plexi is there any other info on the 50pf stuff?

[67plexi]

I was wrong it is 50 ohm coax not 50pf coax.

This coax is silver tined copper not pure silver like the coax I have.

http://www.belden.com/techdatas/english/84303.pdf

[wjdunham]

I've been using this stuff in my 70's amps, I believe Brandon had recommended it in a thread here. I have no problems with harshness, and those amps have no snubbers and I don't have the treble bleed in there either. No problems at all with high end harshness.

http://www.gepco.com/products/proav_cab ... gage_M.htm

I believe it's the same as the originial post except the shielding is foil in stead of the braiding.

Bill

[talbany]

Here are the specs on the 2nd generation like #40 (silver) If anyone cares..

Columbia Flexfoam 1389
Coaxial video cable 75Ω
Capacity: 18.3pF/ft
Inner Conductor: AWG 22, stranded wire 7x AWG 30
Dielectric: 2.8mm foam PE
Shield: Braided shield
Jacket: 4.6mm PVC

Coax Dumble History..
In the 3rd generation "pre-classic" amps you find a different coax cable. It is not the "Columbia Flexfoam 1389" of the 2nd generation ODS amps but a usual black RG59 foam 75ohm video cable. It looks very similar as the black Tandy Wire RG59 of the transition generation and 4th generation amps but it is not marked "Tandy Wire". These different coax cables may well be one of the reasons for the different tone of the 3rd generation amps in addition to the small tone stack differences between 2nd and 3rd generation amps.
One difference between "classic" and "skyline". The "skyline" amps have the white teflon coax cables ( I believe are RG319) these are a part of the "skyline" update ( see #124.) The "classic" amps (like Gregors #94) have the black "Tandy Wire" RG 59/U foam 75ohm video cable. All these various cables will make a difference in tone,


Tony

[dcribbs1412]

Thanks for the info Tony
I'm starting to understand the many types of coax and how much it affects everything.

Bill
I think my harshness is from my lack of skill/experience rather than the coax
I think I got that cable on Brandon's recommendation also.

67plexi do you know what the pf/ft of your cable might be?

[67plexi]

With my old Eico Model 950 it reads @ 30pf/ft

[dcribbs1412]

Thanks plexi
I'm trying to find some close spec cable.

Bill
after looking at the cable specs
do you use both conductors or do you use one with one tied to the shield?

http://www.gepco.com/products/proav_cab ... gage_F.htm

[wjdunham]

Thanks plexi
I'm trying to find some close spec cable.

Bill
after looking at the cable specs
do you use both conductors or do you use one with one tied to the shield?

http://www.gepco.com/products/proav_cab ... gage_F.htm

I use just the white conductor for the signal, and tie the braided wire and black conductor together and ground, so I use it like a single coax, not dual.
Bill

[vibratoking]

I thought I would tag on to this thread.

There are quite a few coax/shielded cable threads in this forum. Some recent and some more than 5 or 6 years old. There seem to be 3 schools of thought:
1 - use a little coax as possible. Some have said don't use any. Use lead dress to retain noise immunity.
2 - use low capacitance cable, something less than 20pF.ft, in the amp and the Dlator. Dogears has said that retaining as much brightness as possible contributes to the amps' ability to sing.
3 - use higher capacitance cable, something like 25pF/ft or more, to rolloff some highs. Then install a tuned bright cap on the master to restore the highs.

I have to admit that I haven't tested and compared these methods, yet. I am currently gathering some different types of coax. I know that sometimes approaches and perceptions change with time. Which, if any, of these approaches represents the current state of thinking? What locations have you found it useful?