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Using 10 metre interconnect question

Discussion in 'audio' started by valvenut, Aug 1, 2021.

  1. valvenut

    valvenut pfm Member

    I am wanting to use a reel to reel deck in my hifi room but it is going to need 10m interconnects to get connected to my amp. Has anyone used this length of interconnect .I am looking at running it under the floor which can get damp so hoping it will be ok.
    Thanks
     
  2. colasblue

    colasblue pfm Member

    This really depends on the design of the preamp input and the tape deck output. If the pre amp has high input impedance compared with the tape output then all is likely to be well. If the tape deck is pro audio then it's likely to have been designed with long interconnects in mind. Be careful to choose the correct type of interconnect cable and ideally use things designed for pro audio rather than Hi Fi tomfoolery. If a coaxial type is needed then Canare LV61s is pretty good. I use that for a 6M tape loop to a pro sound card (3M out 3M back) and I can switch the cable in and out (with remote ends joined together) with no observable loss in sound quality compared with source direct. If it's shielded twisted pair you want then Mogami Neglex 2549 or Vann Damme pro patch should do it.
     
    Salamander likes this.
  3. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    What's the R2R and the amp? Do you want to record from the amp?
     
  4. valvenut

    valvenut pfm Member

    Croft micro and an Akai gx620 and possibly a revox B77.Yes wanting to record and playback.
    Thanks
     
  5. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    Should be fine playing back but no chance on the recording. There will be no top end due to the high output impedance of the tape out on the Croft combined with the capacitance of the coax.
     
  6. valvenut

    valvenut pfm Member

    Would using a different type of cable help at all.thanks
     
  7. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    No. Even the lowest capacitance coax will be too much capacitance at that length with that pre amp. Ideally you need a pre with buffered tape outputs.
     
  8. colasblue

    colasblue pfm Member

    Last edited: Aug 1, 2021
  9. valvenut

    valvenut pfm Member

    I also have a xindak xa3200 mk11 would that be ok
     
  10. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    That should do the trick yes. Tape out on Croft to the "cleanbox" and then the output of the "cleanbox" to the R2R via the long cable. It's likely that for optimum results the "cleanbox" would need to be switched on whenever the Croft is in use as when off it could place a non linear load on the tape out of the Croft causing distortion on all inputs (most likely on phono). OR of course just connect it to the Croft's tape out when you want to record.
     
  11. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    No. You need buffered tape outputs. A few pre amps have them (all SS units) but most do not.
     
  12. valvenut

    valvenut pfm Member

    Thanks for your advise great to get such quick answers too.I think I need to just figure a way to move the reel to reel .
    I do use a Denon av2000 which has line in and out would this maybe do it if I fed it to that from the amp and then the reel to reel
     
  13. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    Ideally just put the R2R within a metre or so of the Croft yes! I don't know the details of the Denon but the vast majority of amps do not use buffered tape out
     
  14. Zombie

    Zombie pfm Member

    I used a 10 m standard cable from my A77 Line out to an Quad Elite pre Aux input. No problem. No recordings, though. When recording I moved the deck closer and used black Linn cables.
     
  15. colasblue

    colasblue pfm Member

    Actually maybe if you have no plans to move either on.

    The tape out won't work as Jez said since it pretty much just connects the line level source or phono stage out to the record cable, but the main pre-out possibly would work. The croft claims an output impedance of under 300R which would drive the record cable perfectly well. No idea what the Xindac's main pre out impedance is but every chance it's similar. So if you connect the tape out of one pre to the line in of the other and use one main out to drive your power amp, and the other to drive the record line it would probably work. Expensive way to do it though.
     
  16. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    A schematic I looked at for "Croft micro" had a 47K resistor at "tape out".... This will help ameliorate the worst effects of a low impedance on the valved phono section, but puts all outputs from a 47K MIN impedance anyway. There are so many variants of Croft that it's impossible without looking at the circuitry of any specific one to know exactly what is what!
    Even if a fairly low capacitance coax of 100pF/m is used then that's 1nF capacitance from just the coax at 10m... so best top end of 3.5KHz tops...

    Yes "colasblue" the main output would work much better... but then there's no tape monitor etc available and you can't listen while you record
     
  17. colasblue

    colasblue pfm Member

    Under the two preamp option you could, but like I said, expensive way to do it. It's essentially the same as using a whole preamp as just a buffer circuit.

    I agree tape monitoring is quite important on these analogue recorders.

    Sensible length leads are a better and considerably cheaper way to go though since any sort of buffer is adding an additional active stage.
     
  18. valvenut

    valvenut pfm Member

    Thanks I am going to move the reel to reel closer so solve it.
     
  19. ToTo Man

    ToTo Man the band not the dog

    I'm confused now because Jez's answer to my question in this thread implied that there should be no HF rolloff in the audible band when using a 5m long interconnect compared to a 1m interconnect with an active SS pre. I measured a very tiny amount of HF rolloff when I connected the line out of my Yamaha A-S3000 integrated (which I assume is unbuffered) to a Focusrite 4i4 ADC using a 5m interconnect instead of a 1m interconnect. It was only a couple of tenths of a dB at 20kHz though so would likely be inaudible to all but those with golden ears.
     
  20. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    Nothing to be confused about! It all depends on the source impedance. 100m could be fine in one situation but 2m pushing it in another... The Croft has a source impedance of 47K from tape out (possibly/probably anyhow! Croft keep making changes so often that the problem with Croft is that you really need to open any particular example up and see what spec it is) according to schematics I've seen, and rather higher on phono.

    Many amps simply connect the source direct to tape out and so are capable of driving whatever the source can (or cannot) drive. The 47K resistors used in the croft give some isolation from non linear loads of switched off equipment at tape out.

    The OP could of course just short out the 47K resistors and jobs a gud 'n... on most sources... but you couldn't use phono without unplugging the lead from tape out and couldn't record from phono.

    I guess the ideal solution would be to build a small SS buffer into the Croft and power it from the heater supply. I would charge £200 to do this.
     
    ToTo Man likes this.

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