• Registered: 2017-05-18
  • Posts: 42

Topic: HDSP 9632 headphone out as line out

Hi,

I have an HDSP 9632 PCI. I use the balanced breakout cables. I want to add an external headphone amp. At the moment Analog Out 1&2 are my only outputs (I have no additional outs). Am I correct in assuming that the headphone output can be used as a line output as well? Will doing this in any way compromise the sound quality from the headphone out as compared to the sound quality from Analog Outs 1&2? Or are they identical as regards quality?

I will make a split cable as described in the manual, from the headphone out to rca males. It seems almost too good to be tru to be able to do this without degrading audio quality, so I want to double check before I go ahead.

Best,

Magnus

  • vinark
  • DAW Mastermind
  • Offline
  • Registered: 2009-06-05
  • Posts: 2,861

Re: HDSP 9632 headphone out as line out

AFAIK the same audio quality cause it is the same DAC. You are aware it is not a separate output but the same as analogue1/2?

Vincent, Amsterdam
https://soundcloud.com/thesecretworld
BFpro fs, 2X HDSP9652 ADI-8AE, 2X HDSP9632
  • Registered: 2017-05-18
  • Posts: 42

Re: HDSP 9632 headphone out as line out

vinark wrote:

AFAIK the same audio quality cause it is the same DAC. You are aware it is not a separate output but the same as analogue1/2?

Yes, I am aware of that. But it seems like a cost-effective option to add a better headphone preamp, as long as the audio signal is not degraded by passing through the HDSP's built-in headphone preamp/output.

/Magnus

  • Registered: 2017-05-18
  • Posts: 42

Re: HDSP 9632 headphone out as line out

Could someone from RME please confirm that the audio signal is not degraded or compromised by the built-in headphone preamp, but is indeed identical to the Analog 1 and 2 outs on the xlr jacks?

/Magnus

  • From: Germany
  • Registered: 2007-04-10
  • Posts: 9,847

Re: HDSP 9632 headphone out as line out

Why would a headphone output be "degraded or compromised" on a card like this? The output can connect to line inputs as well, but you will not get an independent signal, since the DAC is the same for both line and phones out.


Regards
Daniel Fuchs
RME

Regards
Daniel Fuchs
RME

RME Support's Website

  • Registered: 2017-05-18
  • Posts: 42

Re: HDSP 9632 headphone out as line out

Hi Daniel,

Thanks for confirming the integrity of the audio signal through the headphone out. I was worried, since AFAIK an output impedance as high as the 50 ohm of the HDSP 9632's headphone out will affect the frequency response of most headphones very negatively, for instance my 300 ohm Sennheiser HD-600s.

To the best of my understanding, the impedance of a headphone amp output should be at least 8 times lower than the impedance of the headphones. A proper fit for the headphone out of the 9632 would then have to be at least 400 ohm. This to me suggested that the headphone output on the 9632 is at the least a poor design.

That's what made me worried anyway.

As I said above, I am aware that the signal is not independent of the Analogue 1 and 2 outs.

In the future I may add an AO4S-192 to my setup to get around this. But for my present purposes I should be (cost-effectively) fine with using the headphone out as a line out.

Best,

Magnus

7 Reply by MC

  • MC
  • MC
  • Administrator
  • Offline
  • From: Germany/Thailand
  • Registered: 2007-04-06
  • Posts: 25,770

Re: HDSP 9632 headphone out as line out

The frequency response of whatever phones can only be affected negatively when the phones has a very uneven impedance over frequency. In your case the HD 600 is quite lienar except for a bass resonance at around 100 Hz, wich will give a very slight bass bosst when used with the 9632. Now you could argue that is not good. Others will argue that is exactly what this headphone needs, and why Sennheiser's own high-end headphone amp has 100 ohm output impedance wink

Regards
Matthias Carstens
RME

MC's Website

  • Registered: 2017-05-18
  • Posts: 42

Re: HDSP 9632 headphone out as line out

MC wrote:

The frequency response of whatever phones can only be afected negatively when the phones has a very uneven impedance over frequency. In your case the HD 600 is quite lienar except for a bass resonance at around 100 Hz, wich will give a very slight bass bosst when used with the 9632. Now you could argue that is not good. Others will argue that is exactly what this headphone needs, and why Sennheiser's own high-end headphone amp has 100 ohm output impedance wink

Hm, interesting stuff. So perhaps I misunderstood this article on headphone impedance?

http://nwavguy.blogspot.se/2011/02/head … dance.html

Anyway, the headphone amp on my Palmer Monicon L has an output impedance of 10 ohm, according to Palmer support. It makes my NAD Visios - 32 ohm - sound extremely muddy, and my Sennheiser Momentum On-Ears - 18 ohm - sound awful. This to me corroborates exactly what the above blogger says about headphone impedance vs output impedance, especially since the 300 ohm HD-600s sound fine on this preamp.

I don't know what Sennheiser amp you are referring to, but their HDVD800 seems to have an output impedance of 16 ohm, low compared to the 300 ohm of the HD-600.

Anyway, you may be right, I am no engineer, I try to make sense of what I read. And since my low-impedance headphones are almost unlistenable with higher impedance amp outputs, I tend to believe my ears in this case.

Best,

/Magnus

9 Reply by MC

  • MC
  • MC
  • Administrator
  • Offline
  • From: Germany/Thailand
  • Registered: 2007-04-06
  • Posts: 25,770

Re: HDSP 9632 headphone out as line out

> Hm, interesting stuff. So perhaps I misunderstood this article on headphone impedance?

You were talking about the HD600, not In-Ear monitors, which have wild impedance swings and therefore are not suitable at the 9632 output.

> but their HDVD800 seems to have an output impedance of 16 ohm

That value is the recommended minimum impedance as load (the phone). The internal output impedance is not stated by Sennheiser, but seems to be 47 Ohms. I confused that with the Beyerdynamic A1, which has 100 Ohm.

Anyway, you want to to use IEMs, then you need a low impedance phones output. Our latest interfaces have either 2 or 0.1 Ohms of output impedance.

And reading your above post again you seem to have a wrong understanding of impedances when using multiple units. The phones output impedance of the 9632 is of no relevance at all if you connect a headphone amp to it, and then connect the headphone to that headphone amp. The headphone amp has a high impedance input, and a low impedance output. Totally decoupled operation.

Regards
Matthias Carstens
RME

MC's Website

  • Registered: 2017-05-18
  • Posts: 42

Re: HDSP 9632 headphone out as line out

MC wrote:

>
...
And reading your above post again you seem to have a wrong understanding of impedances when using multiple units. The phones output impedance of the 9632 is of no relevance at all if you connect a headphone amp to it, and then connect the headphone to that headphone amp. The headphone amp has a high impedance input, and a low impedance output. Totally decoupled operation.

Well, I just wanted a corroboration. I never thought that the 50 ohms from the 9632 would be "transferred" through the headphone amp to the headphones. I am not that stupid. wink

Thanks anyway for engaging in this interesting subject, and for confirming that the output quality from the 9632 headphone amp is identical to that from A1 and 2.

And just so that you know: I have had the 9632 for almost ten years. It is a great product, and I love RME.

Best,

Magnus