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Author Topic: Tape head to preamp cable  (Read 8767 times)

Offline ketchup

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Tape head to preamp cable
« on: February 13, 2007, 11:10:58 PM »
I'm curious as to what everyone likes in a tape head to preamp cable.  Low capacitance coax (is ther anything that's small diameter?)?  How about a twisted pair of teflon insulated, small gauge, silver tonearm-type cable?

What are you using, and how is it working out for you?

In what ways will a tape head > preamp cable differ from a phono cartridge > preamp cable?

Thanks,
Kevin

Offline PJ

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Re: Tape head to preamp cable
« Reply #1 on: February 14, 2007, 01:29:38 AM »
Really, it's going to depend strongly on the tape head, and on the length of the cable. For high-inductance heads (over, say 300mH) capacitance is usually your enemy - it resonates with the head's inductance, and no exotic material is going to make up for excess capacitance.

For very low inductance heads (usually they will have a step-up transformer at the preamp end, unless it is an exotic current-source head) you must worry about magnetic field hum, so shielded twisted pair and a differential input is going to work best; capacitance is not the problem here.

In the middle range, say 100mH to 300mH, you will want to worry about both problems. I'd take shielded twisted pair for preference even with an unbalanced input, though coax can work equally well if carefully implemented. For runs longer than 1 meter, capacitance is again the main problem. Use short runs!!
Paul Joppa
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Offline James Guillebeau

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Re: Tape head to preamp cable
« Reply #2 on: February 14, 2007, 10:28:48 AM »
I use Belden 8450 or Alpha 2460C, twisted pair, shielded, solid. I agree with PJ. Keep the cable short and get the preamp as close to the head as possible without getting near a power transformer or motor. James
"I'm completely free of prejudice. I hate everyone equally." W.C. Fields

Offline docb

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Re: Tape head to preamp cable
« Reply #3 on: February 14, 2007, 01:38:46 PM »
I found this reply sent to someone who was asking me for suggestions for low capacitance head cabling a couple of years ago:

-- Belden 1505F, 1694A (it's kind of thick and a lot stiffer), and 89259 (pretty stiff too, but Teflon instead of Polyethylene). They are all roughly 17-18 pF/ft. 89259 is what I used on my Ampex 934. --

Those are all coax, BTW. By comparison 8450 is 40pF/ft. conductor to conductor - but on the plus side it's twisted pair, more flexible and quite a bit smaller diameter than 89259. I just looked up 89841,which is stranded shielded twisted pair, but at 12pF/ft. conductor to conductor and with Teflon insulation it looks pretty interesting in spite of the hassle of solder prepping stranded wire. A RoHS compliant 1000ft. spool is $2517.25!!!!
« Last Edit: February 14, 2007, 02:18:01 PM by docb »
Dan "Doc B." Schmalle
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Managing Director - retired, The Tape Project

Offline ketchup

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Re: Tape head to preamp cable
« Reply #4 on: February 19, 2007, 08:34:55 PM »
Thanks, everyone.

I just found a few feet of Belden 1695A in the closet, so I think I'll begin my experimentation with that if I can find a way to get it out of the headblock!  It's almost identical to 1694A but its insulation is teflon instead of polyethylene.  Maybe my next experiment will be a twisted pair of Silver Van den Hul tonearm cable that I'm about to remove from my turntable!