Using DIN & RCA at the same time. Issues?

[InductionRoar]

I fear this may be a rather simple question though it is one I am struggling to receive a definite answer on.

I use a Naim CD player which is connected to a Naim external power supply/pre amp/power amp via DIN (complete Naim system) I also have a Pathos Aurium headphone amp which is connected to my CD player via RCA. The CD player helpfully has two outputs so I have the pre/power amps and headphone amp connected at all times via DIN and RCA respectively.

Due to the infrequency at which I use the headphone amp it is hardly ever switched on whereas the pre/power amp is always switched on (as per Naim's recommendation). Due to the fact that the headphone amp takes hours to warm up my question is can I listen through the speakers (DIN) whilst the headphone amp (RCA) is being used - warmed up?

In my mind there should be no issue as I am able to channel the signal to RCA, DIN and RCA & DIN at the CD player but neither Naim nor Pathos will comment as obviously they do not support the other company's product.

Is there any issues I should be aware of or should I stop worrying?

Thanks in advance.

[Crackie]

If the CD is already permanently connected to the main system and Pathos then all will be fine. The output stage of the CD player will already 'see' the combined load impedance presented by the Naim Pre amp and Pathos amps in parallel.

[InductionRoar]

Thanks Crackie.

I knew PH wouldn't loose me down.

[TonyRPH]

Crackie said:

If the CD is already permanently connected to the main system and Pathos then all will be fine. The output stage of the CD player will already 'see' the combined load impedance presented by the Naim Pre amp and Pathos amps in parallel.

But surely if the combined load impedance is low, this could result in some bass rolloff if the Naim has small output capacitors for example?

For arguments sake - if the Pathos has an input impedance of 10k and the preamp has an input impedance of 10k*, that means the LF -3db point could well be lifted to ~30Hz?

This is pure speculation without knowing the input impedance of both devices and the value of the output capacitors (if any) in the CD player of course.

• The NAC202 has an input impedance of 47k - Pathos, rather unhelpfully, decline to state the input impedance of their headphone amp, but I wouldn't be surprised if it was around 10k.

EDIT: Rather shockingly for such a high end vendor, the link to the Aurium on the Pathos website appears to be somewhat broken!

Edited by TonyRPH on Sunday 11th December 11:42

[Crackie]

TonyRPH said:

Crackie said:

If the CD is already permanently connected to the main system and Pathos then all will be fine. The output stage of the CD player will already 'see' the combined load impedance presented by the Naim Pre amp and Pathos amps in parallel.

But surely if the combined load impedance is low, this could result in some bass rolloff if the Naim has small output capacitors for example?

For arguments sake - if the Pathos has an input impedance of 10k and the preamp has an input impedance of 10k*, that means the LF -3db point could well be lifted to ~30Hz?

This is pure speculation without knowing the input impedance of both devices and the value of the output capacitors (if any) in the CD player of course.

• The NAC202 has an input impedance of 47k - Pathos, rather unhelpfully, decline to state the input impedance of their headphone amp, but I wouldn't be surprised if it was around 10k.

EDIT: Rather shockingly for such a high end vendor, the link to the Aurium on the Pathos website appears to be somewhat broken!

Edited by TonyRPH on Sunday 11th December 11:42

Back in the day 47k was always the target input impedance for analogue stages; I've also seen 22k on several more recent products. If the Naim pre and pathos are already permanently connected, and InductionRoar is happy with the current sound quality, then there should be negative effects when listening to the main system whilst the Pathos get up to temperature.

[TonyRPH]

Crackie said:

Historically, 47k was always the target input impedance for analogue stages; I've also seen 22k on several more recent products. If the Naim pre and pathos are already permanently connected, and InductionRoar is happy with the current sound quality, then there should be negative effects when listening to the main system whilst the Pathos get up to temperature.

It would be an interesting experiment for InductionRoar to disconnect the pre and Pathos in turn and listen for any subjective change in sound quality. I think there will be no difference.

@Crackie - I wasn't disagreeing with you by the way - I just thought I'd add my comment for the sake of completeness.

Reason being.. I remember when I used to have a tape deck in my system - there was one in particular, with a particularly low input impedance, and disconnecting it made a discernible difference in the very low bass.

I fixed it by fitting a simple OPAMP buffer to the tape output at the time.

And yes, it would be interesting if InductionRoar did listen with and without the headphone amp connected to hear if there was any kind of difference.

[InductionRoar]

Thanks for the input chaps.

When I first connected the headphone amp I played both the headphones and the speakers at the same time (I just turned the volume down on whichever amp I wasn't using) so I could do a back to back comparison to see which I preferred.

I never noticed a drop off in performance of the Naim system when the Pathos was being used though since the doubt was put in in my mind I haven't done this since.

The full system is a CD5X, NAC 112X, NAP 150X and Flatcap 2X. Not sure if this helps or not but seeing as you wnet to the trouble to research the impedance I thought I ought to give the full details.

The Pathos website is pretty shocking as you have seen and their instruction manual provides no additional information as to the specification.