Is it worth using a receiver as an amp?

Not really, for a number of reasons. First, the headphone out on most HT / stereo receivers and stereo integrated amps aren't necessarily bad, they're still an afterthought so that wives and mothers won't get more headache sources on top of their PMS. Which means you ought to try first if the IEMs would be more quiet with these. Second, although it provides you with a DAC, HT DACs are not the same as stereo DACs. Not that all 6ch or 8ch DACs are that bad all the time, but consider teh entire circuit design of the whole thing starting with the DAC, and that's not really what they're for. Also, you might want to keep it a bit further from you because these things get real hot, and I don't know it it cuts the current to the speaker power amp section when a headphone is plugged in (or if that's manually defeatable.)

BUT, no harm in trying. Just see first if the IEMs get an improvement with it, and keep it as from as possible to deal with the heat, until you save up for a DAC+Amp.

Kinda depends actually.  Receivers and Integrated Amps USED TO have decent headphone outs on them with dedicated components inside just for the headphones.  Nowadays, the headphone outs on receivers are somewhat of an afterthought and aren't really made the way that they used to be.  Now, not all receivers are like this, and I am not overly familiar with Onkyo equipment (haven't owned any myself), but it was at one point very good stuff.

All of that being said, my next question would be what headphones are looking to use with this?

I would imagine that the Grado's will probably do fine, however, you may have to just do some trial and error with the in-ears.  The trick will be what the IEM's impedance is vs the impedance from your receiver's headphone output.

Don't know about HT receivers, but as far as stereo equipment goes there's no "afterthought" about headphone jacks; 90% are taken from the speaker outlets via resistors, which means you're getting the same signal to the headphones as the speakers. There's no inherent advantage in a dedicated amp to drive the jack; indeed it will probably use a cheap IC and lack power. If you use headphones with an amp you want to hear the amp itself, the amp you bought presumably because it was well reviewed with speakers, not a secondary amp tossed in just for headphones.

No offense, but this question has been asked here at least 600 times.  The answer that usually pops up is this:

If you already own the receiver, try it out.  It IS a headphone amp.  You can try it out for free.  If you like it, keep it, use it, and love it.  Put your cash towards some new music.  If you don't like it, audition some dedicated headphone amps to determine if you want to upgrade.  In the end, the only thing that matters is what your ears tell you.

Quote:

Originally Posted by hodgjy 

No offense, but this question has been asked here at least 600 times.  The answer that usually pops up is this:

 

If you already own the receiver, try it out.  It IS a headphone amp.  You can try it out for free.  If you like it, keep it, use it, and love it.  Put your cash towards some new music.  If you don't like it, audition some dedicated headphone amps to determine if you want to upgrade.  In the end, the only thing that matters is what your ears tell you.

Even if they are covered by pink bunny ears. LOL

To answer the question. My Outlaw 2150RR has a very good head amp but I still prefer a dedicated amp. Try both ways to see what you prefer.

True dat!  That was a photo taken of me when my little nieces wanted to play rock band with me last Christmas.  Their gifts included a pink guitar and a karaoke machine. 
 

Quote:

Originally Posted by Frank I 

Even if they are covered by pink bunny ears. LOL

I own a TX-SR876 Onkyo receiver, and went to some trouble to get the service manual.

Now this is NOT the same receiver as the one you ask about, but it may give you an idea of the approach taken by Onkyo

The HP Jack is driven by a dedicated Headphone amp stage based around 2xNE5532 opamps followed by a discrete buffer stage - this is no different to low to mid range headphone amps.

I have been testing it compared to a Firestone Audio Cute Curve with Creek OBH2 power supply (the power supply improves the sound) - and the dedicated Headamp is marginally better.... maybe... testing is in progress.

So here you have around $500 of headamp vs a receiver you can pick up for around $700 and the sound quality is a wash.

I am using Vintage Revox 3100 (1986 OEM Beyer DT880) 600 Ohm headphones - so like we say YMMV

But try it first it may be great!

An update....

My receiver experiments have involved the Onky TX-SR876 through its Headphone Jack, and then its speaker outputs (via an ART Headtap adapter) - SQ into my Revox 3100's (600ohm) was to all intents and purposes identical - sound quality was good both ways - no problems/issues, the phones were driven properly and there was no excessive noise/hiss.

I also compared to: 

1) Firestone Audio Cute Curve Headamp - marginally better.... probably not worth the $ spend (US$150)

2) Firestone Audio Cute Curve Headamp with Upgrade PSU (Creek OBH2) - better again.... might be worth the $ spend (US$250 all up)

3) Matrix M-Stage Headamp - another step up much better value (US$250)

Other half's comment on the SQ differences - anyone who would worry about this level of difference needs his head examined.....

For an additional US$20 I also purchased a pair of OPA627's and a Class A Mod resistors adapter - these are plug and play mods that can go into either of the Cute Curve or the M-Stage to upgrade them - word in the forums here is that this mod takes the M-Stage two levels up (the OPA627's are an improvement on the stock OPA2134, and they respond well to Class A biasing...)

I have yet to do that comparison but option 4) will be M-Stage will Class A 627 mod for US$270

My objective in all this was to see whether a seperate headamp is a worthwile investment on top of what is in my receiver....

The final decision is of course a value judgement involving perceived SQ (and how much it is valued) vs $ Spent and how much they are valued

So far I have to my own satisfaction confirmed what the experienced "elders" on headfi have been saying - Headamp=Improvement

I have also to my satisfaction debunked the myth of Receiver=Rubbish SQ

Given what I am hearing I believe that one of the Headamps will find a permanent home here - but I have yet to test the Mods (and a suite of additional opamps to see what difference they make) - which headamp will stay, in which form is yet to be seen...

As an aside - reviews online of this receiver have stated that its DAC's are on a par with high end gear.... so I am using the internal DAC's combined with the Headamps - most modern AV receivers are likely to have good DAC's on board.