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Headphone amp and AV receivers

post #1 of 16
Thread Starter 

Hi everyone, noob here in desperate need of expert advice! 

I own the NAD T748 AV Receiver, as well as a pair of Sennheiser HD 598s which I use a lot for night time viewing. I use the Digizoid Zo2 to really bring them alive.

I'm looking to upgrade my cans to the HD-650's or similar, and as such I'm looking for a better driver than the NAD's built in microphone jack. Seems a good quality headphone amplifier is key to this.

Im at a loss though trying to work out how the amplifier and headphone amp would connect? I get how headphone amps can connect directly to a source like a CD player, but in an AV receiver environment, I'm a bit confused.

For example:

1) My NAD T748 seems to have a couple of Analog Audio OUTS:

a) Headhone Jack out
b) Audio Out
c) Audio Pre-Outs to connect to an external amplifier (is this an option with headphone amps?)

What would be the best output to connect to an AMP? I would assume Headphone jack out > Headphone amp > Headphones, but most headphone amps, besides portable ones with 3.5 inputs, only seem to have RCA analog inputs (not headphone input)?

2) My NAD automatically kills the sound to the speakers as soon as I plug in the cans. Is there an elegant way to hook up a headphone amp if I use the audio out or audio pre-out?

3) Lastly, any headphone amp recommendations, especially in an AV environment?

For reference, this is the back of my NAD:

http://i42.servimg.com/u/f42/17/32/12/85/new_0511.jpg > Note that anything that has output is shaded in grey dots

Thanks everyone for your time!

post #2 of 16

So you could hook an external headphone amplifier to the "Audio Out" or the "Front" Pre-outs.

 

What makes you think the NAD would not be a good headphone amplifier for driving the 300-Ohm HD-650 or similar headphones?  I would have assumed it would have at least do a decent job.

 

How do you have your sources connected to the NAD?

post #3 of 16

Hey Roger your audio pre out #3 (in/ out) is the way to go.

 

That is a line level output signal that has not run through the amplifier circuit yet..... If you opt for a desktop type amp you would just connect the two with RCA to RCA.... If you go with a portable amp then you can get an RCA to mini cable that way the headphone amp receives a line level signal and its volume is independent of the receivers. So both could be running at the same time and work independent of each other.

 

If you run through the headphone out like you were saying you are double amping the signal and the volume could be adjusted by either unit..... which not the best option for multiple reasons including fidelity, circuit path, and safety.

 

As far as amp recommendations..... It depends on your budget, and form factor.... portable vs. desktop. Personally I think the HD650 responds best to a desktop unit and is pretty amp picky.... I "personally" think it sounds better with tube amps than solid state but that is just my opinion. 

post #4 of 16

And Purple Angel is right...... An NAD receiver probably has a lot more current on tap through its headphone jack (which is just the speaker amp padded down by resistors) than a good many dedicated headphone amps that are just going to give you a little opamp based gain circuit in a fancy metal box.

 

HD650's are 300 ohm cans so they are pretty resistant to poor damping..... I'd think the NAD would do pretty damn good.

post #5 of 16
Thread Starter 
Quote:
Originally Posted by PurpleAngel View Post
 

So you could hook an external headphone amplifier to the "Audio Out" or the "Front" Pre-outs.

 

What makes you think the NAD would not be a good headphone amplifier for driving the 300-Ohm HD-650 or similar headphones?  I would have assumed it would have at least do a decent job.

 

How do you have your sources connected to the NAD?

Thanks PurpleAngel

 

The HD-598's are my first entry level HP's, but I can hear a distinct difference in quality/vibrancy when I pair them with the digizoid zO2. Directly via the NAD AV receiver, I find them a bit flat and less dimensional, if that makes sense. Admittedly these might not be the best choice headsets for mainly movie watching (lacks bass), but even when I listed to music / FLACs, I always use the digizoid which makes a huge difference. 

 

My sources are as follows: 

 

HDMI 1 > DSTV (satellite) 

HDMI 2 > Media Streamer

HDMI 3 > XBOX

HDMI 4 > unused

 

HDMI OUT > Samsung ES7500

 

Thanks for your response appreciate it

post #6 of 16
Thread Starter 
Quote:
Originally Posted by The Fed View Post
 

Hey Roger your audio pre out #3 (in/ out) is the way to go.

 

That is a line level output signal that has not run through the amplifier circuit yet..... If you opt for a desktop type amp you would just connect the two with RCA to RCA.... If you go with a portable amp then you can get an RCA to mini cable that way the headphone amp receives a line level signal and its volume is independent of the receivers. So both could be running at the same time and work independent of each other.

 

If you run through the headphone out like you were saying you are double amping the signal and the volume could be adjusted by either unit..... which not the best option for multiple reasons including fidelity, circuit path, and safety.

 

As far as amp recommendations..... It depends on your budget, and form factor.... portable vs. desktop. Personally I think the HD650 responds best to a desktop unit and is pretty amp picky.... I "personally" think it sounds better with tube amps than solid state but that is just my opinion. 

Very helpful, I'll definitely try that RCA to mini cable suggestion. 

 

Thanks again

post #7 of 16
Quote:
Originally Posted by RogerWilcoZA View Post
 

The HD-598's are my first entry level HP's, but I can hear a distinct difference in quality/vibrancy when I pair them with the digizoid zO2. Directly via the NAD AV receiver, I find them a bit flat and less dimensional, if that makes sense. Admittedly these might not be the best choice headsets for mainly movie watching (lacks bass), but even when I listed to music / FLACs, I always use the digizoid which makes a huge difference.

My best guess.

It could be that the NAD's headphone output has a high impedance and the Z02 headphone output has a very low impedance, so the 50-Ohm HD598s would be better driven by the Z02.

Where as the 300-Ohm HD650s would be fine with a higher impedance headphone output.

But I would think you could get the HD650s first, see how they sound plugged into the NAD, then decide if you should buy an external headphone amplifier.

post #8 of 16
Thread Starter 
Quote:
Originally Posted by The Fed View Post
 

Hey Roger your audio pre out #3 (in/ out) is the way to go.

 

That is a line level output signal that has not run through the amplifier circuit yet..... If you opt for a desktop type amp you would just connect the two with RCA to RCA.... If you go with a portable amp then you can get an RCA to mini cable that way the headphone amp receives a line level signal and its volume is independent of the receivers. So both could be running at the same time and work independent of each other.

 

Hi Fed,

 

I tried out the RCA to 3.5 jack on both the front L/R audio pre-out and the other Audio 3 line out jacks, but no sound came through the headset (sound came out the speakers as per normal). I looked in the NAD menu to see if there's any particular setting for analog audio out, but couldn't find anything. Any idea what might be needed?

 

Thanks v much

post #9 of 16

RogerWilco,

    I was trying to use my Yamaha RX-V800 to feed an Asgard 2 in the same way as what you're trying to do with your NAD. I thought I could use a pair of the many RCA outlets available, but discovered none of those would work because my source feed was digital. I can only use those analog outputs if an analog signal is input. Tried to read your manual and couldn't find any specifics in your case.

   The pre-outs can be used, but it is noted in your manual (just as it was in mine) that the speaker terminals for the corresponding pre-out cannot be used in this case. Disconnecting the speakers wasn't practical, but I suppose a switch could be installed to disconnect the speakers. I did test the A2 using the pre-outs, after disconnecting the speakers and it worked good, even though two volume controls are now involved.

    The only other option I had to try was using the receiver's HP jack. The A2 worked terrible when I tried this (I originally thought the unit was defective). Same thing when I tried the computer headphone jack. The A2 apparently does not like the common ground that HP jacks use.

    I had another receiver laying around that I could have used, but didn't have enough room with separate stereo and AV systems already in action. I ordered and am still waiting for a Fiio D3 that I'll use for now. Good luck and if you find a way to make it work, let us know.

post #10 of 16
Thread Starter 
Quote:
Originally Posted by Braveheart View Post
 

RogerWilco,

    I was trying to use my Yamaha RX-V800 to feed an Asgard 2 in the same way as what you're trying to do with your NAD. I thought I could use a pair of the many RCA outlets available, but discovered none of those would work because my source feed was digital. I can only use those analog outputs if an analog signal is input. Tried to read your manual and couldn't find any specifics in your case.

   The pre-outs can be used, but it is noted in your manual (just as it was in mine) that the speaker terminals for the corresponding pre-out cannot be used in this case. Disconnecting the speakers wasn't practical, but I suppose a switch could be installed to disconnect the speakers. I did test the A2 using the pre-outs, after disconnecting the speakers and it worked good, even though two volume controls are now involved.

    The only other option I had to try was using the receiver's HP jack. The A2 worked terrible when I tried this (I originally thought the unit was defective). Same thing when I tried the computer headphone jack. The A2 apparently does not like the common ground that HP jacks use.

    I had another receiver laying around that I could have used, but didn't have enough room with separate stereo and AV systems already in action. I ordered and am still waiting for a Fiio D3 that I'll use for now. Good luck and if you find a way to make it work, let us know.

Thanks Braveheart,

 

I had the same experience when I hooked up the digizoid ZO2 to the unit - the headphone gave back quite a bit of interference. What I discovered only recently is that the unit has 2 modes - headphone and line out. As described by the company: "With headphone mode, the volume is controlled by your source with the ZO2 controlling only the amount of bass boost. In line out mode, the ZO2 also controls the volume". 

 

The way I understand this is that it is essentially low gain and high gain mode. The interference came through in high gain mode, but when I changed to low gain, it sounded amazing. No interference and the audio quality was vibrant compared to plugging it in directly in the receiver. 

 

As is, I'm quite happy with the Zo2 and HD 598 combo, but worry about the HD 650's and if it'll be enough. Going to take the plunge soon though anyway. 

 

So I figure the interference was a combination of the double amping of the amp's HP Jack, and high gain mode of the Zo2. Does the A2 come with different gain modes?


Edited by RogerWilcoZA - 10/28/13 at 9:18am
post #11 of 16
Quote:
Originally Posted by RogerWilcoZA View Post
 

Thanks Braveheart,

 

I had the same experience when I hooked up the digizoid ZO2 to the unit - the headphone gave back quite a bit of interference. What I discovered only recently is that the unit has 2 modes - headphone and line out. As described by the company: "With headphone mode, the volume is controlled by your source with the ZO2 controlling only the amount of bass boost. In line out mode, the ZO2 also controls the volume". 

 

The way I understand this is that it is essentially low gain and high gain mode. The interference came through in high gain mode, but when I changed to low gain, it sounded amazing. No interference and the audio quality was vibrant compared to plugging it in directly in the receiver. 

 

So as is, I'm quite happy with the Zo2 and HD 598 combo, but worry about the HD 650's and if it'll be enough. Going to take the plunge soon though anyway. 

 

So I figure the interference was a combination of the double amping of the amp's HP Jack, and high gain mode of the Zo2. Does the A2 come with different gain modes?

Glad it worked out for you.

The A2 does have high and low gain modes. That's why I passed on the Magni. I'm using the HD558 which is a high efficient HP (just as your 598's are) and it's only 50 ohm (40mw max). When I plug the A2 into the HP jack it sounds like I'm listening to mono.

This is my first foray into the world of serious headphones. I always preferred listening to music on speakers, but never preferred have the police banging on the door (sometimes I like my music loud). The town I live in has a noise bylaw that technically can be broken when two people talk to each other when they're four feet apart.

Are your HD650's comfortable? I went with the 558 for the comfort factor. I knew that if I got a HP that wasn't comfortable, no matter how good it sounded, I would abandon the whole headphone experiment. Using a headphone is a lot less expensive than building a soundproof room.

post #12 of 16
Thread Starter 
Quote:
Originally Posted by Braveheart View Post
 

    I was trying to use my Yamaha RX-V800 to feed an Asgard 2 in the same way as what you're trying to do with your NAD. I thought I could use a pair of the many RCA outlets available, but discovered none of those would work because my source feed was digital. I can only use those analog outputs if an analog signal is input. Tried to read your manual and couldn't find any specifics in your case.

  

 

I was under the impression the AV receiver would act as a digital to analog converter, but that makes sense. So in this case, would a DAC+AMP combo be the way to go if you want to use the audio outs?

post #13 of 16

I'll receive a Fiio D3 on Wednesday. I'll use that until I have funds for something more adequate.

I bought the A2 thinking that I'd use the receiver as a temporary DAC until funds became available get a Bifrost.

I'm hoping the receiver's HP jack may have a high impedance output and the A2 will make the HD558's sound better.

Maybe I'm just hoping these HP's are better than what they are. Their comfort is outstanding.

post #14 of 16
Quote:
Originally Posted by RogerWilcoZA View Post
 

I was under the impression the AV receiver would act as a digital to analog converter, but that makes sense. So in this case, would a DAC+AMP combo be the way to go if you want to use the audio outs?

As the Marantz's only digital output is the HDMI, Chances are you not going to be hooking a DAC/Amp to the Marantz.

post #15 of 16
Thread Starter 
Quote:
Originally Posted by PurpleAngel View Post
 

As the Marantz's only digital output is the HDMI, Chances are you not going to be hooking a DAC/Amp to the Marantz.


Correct...so if no sound was coming out of the RCA audio outs, does that mean the only way to hook up a HP amplifier to a AV receiver is via the HP Jack (or just rely on the AV receiver solely?)

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