Long Interconnects Cable Suggestion

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izzy wizzy
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#1 Long Interconnects Cable Suggestion

Post by izzy wizzy »

I'm currently using twisted magnet wire interconnects 9m long. Up until now, they've been fine but with my new amps, I have a feeling they are causing problems.

I would like to try some kind of twisted shielded pair for a balanced interconnect 9m long. In the past, I have preferred pure copper, no plating of any kind.

Does anyone have any suggestions for some cable that is cheap and decent sounding?

cheers,

Stephen
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pre65
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#2

Post by pre65 »

Cat5 ?
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IslandPink
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#3

Post by IslandPink »

Have you spoken to Bud Purvine ? ( O-Netics )
He sold me speaker cables and interconnect made from 140/40 litz in cotton braid outer (shoelace !) a few years ago and I've been using them ever since. At that time he didn't charge me very much ...

Mark
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al newall
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#4

Post by al newall »

Van Damme Microphone Cable?
Much to learn there is.
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Greg
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#5

Post by Greg »

For long interconnects I use this.

http://www.maplin.co.uk/Module.aspx?ModuleNo=132
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IslandPink
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#6

Post by IslandPink »

Sorry the shielding bit is going to be difficult with that .
Now, a friend of mine made interconnects using satellite cable - the outer copper foil was left in place ; the inner thick wire was removed ; and he fed thin pieces of solid-core (enamelled ) copper down two sectors of the polythene separator ( Trivial Pursuit 'cheese' cross-section ) . You could do this with litz wire, which would be better .
I got a reel of something like 13/38 litz ( 13 strands of 38 gauge ) which has been very useful for small-signal link-ups .

MJ
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#7

Post by Toppsy »

I use similar 6m long interconnects as described by IslandPink above. However, I use thread 4-lengths of very thin silver wire down the polythene seperator using 2 for signal and 2 for earth. I then connect the outer sheild of the coax cable to one phono plug earth to act as a drain. If you cover the coax cable with some the stretch nylon braiding they look very professional finish.

Silver wire bought from http://wires.co.uk/.
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Mike H
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#8

Post by Mike H »

Rapid Electronics "instrument cable", sold in 20 metre lengths.

I think it's intended for on-stage microphones and like that. I've made a number of interconnects with it with gold phonos, seems quite good.



 
 
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#9

Post by izzy wizzy »

Thanks for the suggestions. At some point, I have to figure out, are the interconnects causing the problem or is it something in the way I've built the new power amps.

I was at the point in thinking it is the interconnects but last night, I had a thought about the power amps that could be the cause of the problem.

They use a cascode front end which is a very wideband amplifier. My layout may have caused it or the finals stage to be a bit unstable and the long interconnects in both amps just may push it over the edge. Quite how this would happen, I'm not sure but "the fix" for the layout would be free for now if it worked.

After that, if there's no fix, I'll try short ordinary interconnects and if that's fine, extend them until there is a problem.

Farnel seem to be a good supplier of the Van Damme cables which would be first choice for now. Rapid seem quite expensive for that brand. I really want to stick with magnet wire as it is soooo cheap. I can't quite believe the new amps, with balanced transformer input have a problem while my EAR509s single ended input have none.

cheers,

Stephen
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#10

Post by Mike H »

Transformer inputs? Maybe forming a tuned circuit with the cable capacitance?



 
 
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#11

Post by izzy wizzy »

Thanks Mike. Problem is a whistle. Happened with or without transformer. Single ended as shown or balanced. With or without CCS in LTP tail. With both heaters powered as shown or separate top and bottom. With CC grid stoppers everywhere. Ferrite beads on top heaters.

Happens only with both interconnects plugged in which don't share a common connection. Continues to be unstable even if commoned up. OK if only one interconnect plugged in :?

I got it reduced from very annoying to only mildly noticeable.

But I spotted a build error last night that mayhaps is the problem. The HT caps are in the PSU base and so there's not a good reference in the amp chassis. That seems bad to me and I'm not sure why it happened. OK I was lazy :oops: . Given the cascode is very HF sensitive, and the 813 is very sensitive an 0V ref so far away on long leads may well be the issue.

So Plan A is to use another LC stage, in the HT, in the amp chassis to see what happens. Sometimes this hobby can be very very annoying :cry:

http://www.izzy-wizzy.com/audio/powamp813elin.html

cheers,

Stephen
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#12

Post by Mike H »

Ah now then, I am reminded that a while ago I had a correspondent (bought some transformers I expect, or why would he be e-mailing me! :D )

He got 2 ECC81's as phase-splitters which were whistling.

Turned out they were too close together. I.e., pull one out, nuthin'.

Our solution was put a small value cap across the two anodes of each splitter, but can't remember if it was 10pF or 22pF, but something in that area.



 
 
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#13

Post by izzy wizzy »

I have simm'd a cap across the anodes to reduce bandwidth but it seems a bit of a fudge.

When you say too close, what do you mean? Mine are close - the top and bottom parts are in the same envelope.

cheers,

Stephen
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Mike H
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#14

Post by Mike H »

The ECC81's were close together, must've been interfering with each other. The socket positions then.



 
 
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Greg
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#15

Post by Greg »

Mike H wrote:...........must've been interfering with each other..........
Here we go again :roll:
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