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Headphone amps in Denon AVReceivers

ironhorse128

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#1
Recently I have been forced to use the headphone amp of my Denon x2500h for almost all my movie and TV show watching. I mainly use my Argon Modhouse Mk3 which I find are actually quite enjoyable.
  • I was wondering if anything is known about the quality of the headphone amp in Denon AVReceivers
  • Is there a way to apply EQ to the headphone output
  • Can I add headphone amp even though the x2500h does not have preouts. Would preouts really help?
  • Any tips on how to improve the experience.
Thanks for your feedback.
 

MZKM

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#2
If I'm not mistaken, they just use the DAC output, like for Zone 2 pre-outs. The issue, as seen with the knock-off Topping that Amir just reviewed, is that the output impedance is super high, I'll just paste Amir's comments:

"Ah, the truth comes out! Someone just tapped the RCA outs and brought it to the front and called it done. This is wrong as the RCA out typically has high impedance in the order of 100 ohm we see here. That high impedance causes a ton of power loss as we see in the 33 ohm test. And rules out using vast majority of headphones out there as it will interact with their impedance and change their frequency response (tonality)."

I doubt you can apply EQ.

I think you can use the Zone 2 preouts and send that to a HP amp
 
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escape2

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#3
I can only offer up my experience with headphone out in my S740H. The X2500H may be different.
I've watched a few movies with my Philips X2HR plugged into the S740H headphone-out and enjoyed the experience. Definitely loud enough, but X2HR have fairly low impedance (30 Ohm), so they're pretty easy to drive.

No full EQ control for headphones, but you do have basic bass/treble controls.
 
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#6
Headphone outputs come through a 470 ohm resistor tapped off the left and right speaker outputs.
This is correct. See R6691 and R6692 in the schematic below.

The MCU disables EQ functions when headphones are detected between pins 4 and 5. If you wish to use EQ in conjunction with headphones, you will need to replicate the voltage divider externally and connect it to the speaker terminals.

1610404313225.png
 
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ironhorse128

ironhorse128

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Thread Starter #7
@Otaku+ and @dkfan9 Thanks for your input. It seems that the headphone output is really substandard in these denon receivers.
Yesterday I hooked up one of my RME Adi DACs directly to the TV via optical (bypassing the denon altogether) and this sounded immediately better. The RME Adi DAC gives me loudness and custom EQ options. I guess I will leave it connected to the TV.
 
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