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Nap 250 speaker cables

Discussion in 'audio' started by Alexm2033, Feb 14, 2020 at 8:55 AM.

  1. Alexm2033

    Alexm2033 pfm Member

    Hello all
    I have just acquired a nap 250 for a future upgrade the price was good so I got it.
    I would like to test it when it arrives just to ensure all is ok
    My current speaker cable is vdh skytrack
    Will I be safe to test the amp with this or am I at risk of damaging it.
    Many thanks
     
  2. Whatsisnaim

    Whatsisnaim pfm Member

    I’m sure your 250 will not explode just because you’re not using Naim speaker cable, or one of the alternative brands that have been produced by the likes of Chord to similar specs to ensure compatibility.
    You could try asking the manufacturer what the inductance and capacitance specs of your cable are, and compare them with Naim’s NACA5.
    If the amp sounds strained at high volumes, or overheats when driven hard, that can be a sign that the cables are a poor match.
     
  3. wylton

    wylton pfm Member

    The only thing that Naim say, is to ensure that the loudspeaker cable is low capacitance and of moderate inductance and to avoid high capacitance &/or very low inductance cables; I don't use Naim loudspeaker cable on my 250.
     
  4. MJS

    MJS Trade: Consultant at WH Audio

    If the 250 hasn't been serviced in the last 10 years or so it will probably need a couple of capacitors changing at the least. Otherwise it could sound disappointing regardless of which cables you're using.
     
  5. stevec67

    stevec67 pfm Member

    The cables need to be at least 4m long and of conventional construction, like QED 79 strand, Linn K20, Nainm NACA4 or 5. To test you could use any mains lead material of 4m length or better, say an extension lead. It needs to be this length to provide enough inductance to form a Thiele network. Note that a Thiele network is not the same thing as a Zobel network, this is a common confusion.
     
  6. Alexm2033

    Alexm2033 pfm Member

    Thank you all
    We are having a major refit at home so upgraded are waiting until.tje system is in its new home.
    I just wanted to test the amp was working
     
  7. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    Or the OP could buy one of my gizmos which render it insensitive to speaker cables!
     
    Shadders likes this.
  8. Alexm2033

    Alexm2033 pfm Member

    Assuming no snakes are harmed in the production of said gizmo
    How much?
     
  9. stevec67

    stevec67 pfm Member

    No snakes at all. I talked about a Thiele network earlier. The Arkless box is exactly that, in a box. Look it up, it is a parallel inductor and resistor of modest value. If Naim had put it in the box it would have made the amp unconditionally stable. Instead they chose to make it stable by having 4M of speaker cable do the job of providing the necessary L and R. No snakes, no witchcraft, just basic engineering.
     
    Arkless Electronics and Shadders like this.
  10. Shadders

    Shadders pfm Member

    Hi,
    As it is for Naim, it will need to be blessed by a priest, so may cost quite a bit. Naim prices probably.

    Regards,
    Shadders.
     
  11. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    I couldn't have put it better myself:)
     
  12. stevec67

    stevec67 pfm Member

    Jez, does a JLH 1969 need a Thiele, or is it stable?
     
  13. stevec67

    stevec67 pfm Member

    Well, 2 x 4 M of NACA 5 costs £210, so the "official" solution isn't a giveaway. Compared to a resistor and a coil of wire soldered onto the speaker socket of each channel and <£1, that's a costly solutiuon.
     
  14. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    Stable. Once again it's all down to negative feedback and how it's implemented. It has very few circuit poles (look at it as few intrinsic filters at ultrasonic frequencies) to add phase shifts and not particularly high open loop gain. It therefore has such good gain and phase margins that it needs neither Theile or Zobel networks.
     
  15. stevec67

    stevec67 pfm Member

    Thanks Jez. I understand some of that.
     

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