[jcbrunelli]

Comparing with your HD650 what is the position of the AKG701 in the volume control (in the vertical)?
 
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I think the HDP definitely drives the K701/702 with competence and actually has pretty good synergy with it. I just attended a local meet this last weekend and took my HDP and evaluated it with AKG 701 for a good while as well as many other headphones including Denons, Audio Technica's, Jerry Harvey universals, etc.
 
I felt that the HDP did a nice job of bringing out the bass and getting a fuller and more engaging sound out of K701, which can sound a little lifeless and bass anemic with many amps. The owner of the K701s thought that the HDP did better than many amps he has tried with it and drove them comparably well to his Ming-Da tube amp (which even required tube rolling several times to get there).
 
Overall, I confirmed (to myself at least) that the HDP has very strong synergy with the Sennheiser HD600 and HD650, pretty good synergy with K701, and just good synergy with Denon D2000, D5000, and LA 7000 - all of which I all tried over the weekend. It also did very well with JH 13 universals, Westone UM3X, and IE8 - not having any hiss with any of them according to several members present. On the other hand, I didn't think it had much synergy with a few Audio Technica cans I tried, but then again I don't really like AT's that much so that might just be my bias. 
 
Also, not to get into the volume pot issues again, but I thought it was ironic that a local friend that attended the meet and has a 2-3k tube amp and balanced HD 800s liked the HDP and specifically remarked (unsolicited) that is has a really nice and smooth volume control...

 

[grokit]

The K701 is picky but has great synergy balanced out of a WA22 tube amp.

 

[HeadphoneAddict]

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The uDac and the Grados are both on the forward-sounding side, so they might not be the best match for each other. I wasn't very impressed with my loaner Bithead when I had it, but its unremarkability might be a good clean match with the 325is. You might want to consider an iBasso D4 instead of the Bithead, it has a similar form factor and superior SQ but no rechargeable battery. If your budget is low the Fiio E7 may be a good option. Then again I think the Headstage Arrow HE is starting to ship again, has good bass boost, and is offered with the DAC Stick as a combo deal.

The SR-325i are less forward than my HF-2 with bowls or RS-1 with flats, so it might actually be a decent pairing to warm up the SR-325i sound.

 

[Sid-Fi]

I had to push the volume further for the K701 to a range of 2-3pm versus 1-2pm on HD650 to get them both to fairly loud listening levels. K701 definitely took more power but still had lots of headroom. The HDP is as powerful as advertised IMO.
 
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Comparing with your HD650 what is the position of the AKG701 in the volume control (in the vertical)?
 

 

[grokit]

 
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The SR-325i are less forward than my HF-2 with bowls or RS-1 with flats, so it might actually be a decent pairing to warm up the SR-325i sound.

Maybe forward isn't the best way to describe the 325is. More like a tendency towards sharpness in the upper frequencies. For some reason I don't think I ever plugged my 325is into my uDac when I had them, maybe I would have liked it. I definitely liked them out of some amps more than others, and the pads used of course made a big difference. I even tried them balanced, but in the end they weren't for me.

 

[kite7]

It sounds like this could be the tolerable listening volumes varying from person that makes it seem like the HDP's volume pot being different on each unit. The absolute maximum position I could listen to the K701 was at 12 o'clock with foobar and windows volume at 100%. I usually listened to the K701 at 11 o'clock, 12 o'clock being the maximum threshold for me. With the RS1, if I had foobar at 100% I would have to drop the volume pot below 9 o'clock for it to be listenable which caused imbalance problems so I lower the volume in foobar thus I could adjust the volume pot to about 9:30 with no imbalance problems. With the HD580, I never past 11 o'clock. I have never had to go beyond 12 o'clock with any headphone I owned. What is quiet or loud is not someone else's threshold for quiet or loud. I need a SPL meter some day.

 

[bcwang]

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It sounds like this could be the tolerable listening volumes varying from person that makes it seem like the HDP's volume pot being different on each unit. The absolute maximum position I could listen to the K701 was at 12 o'clock with foobar and windows volume at 100%. I usually listened to the K701 at 11 o'clock, 12 o'clock being the maximum threshold for me. With the RS1, if I had foobar at 100% I would have to drop the volume pot below 9 o'clock for it to be listenable which caused imbalance problems so I lower the volume in foobar thus I could adjust the volume pot to about 9:30 with no imbalance problems. With the HD580, I never past 11 o'clock. I have never had to go beyond 12 o'clock with any headphone I owned. What is quiet or loud is not someone else's threshold for quiet or loud. I need a SPL meter some day.

Finally, someone more like me.  People talking about listening at 3 o'clock in the vertical position.... I don't know how they do it.  For me, 9 is really loud with Grados, and even with the HD800 I listen under 10 o'clock.  Grados are too sensitive for me to use with the HDP internal headphone amp.
 
I doubt the volume pot differs that much, I think it's more people's listening levels vary a lot.

 

[kite7]

I think it is the variation of people's listening levels too. I doubt the quality of the volume pot is contributing to the large variations of preferred volume pot position from each person.
 
9 is really loud for grados I agree with foobar maxed and volume 100%, in fact I can't listen at that volume pot position. I'd have to remove my grados off my head within 5 seconds.

 

[jcbrunelli]

Maybe this link can help:

Measuring headphone volume with a multimeter

 
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Originally Posted by kite7 
 
... I need a SPL meter some day.

 

[TobaccoRoad]

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Finally, someone more like me.  People talking about listening at 3 o'clock in the vertical position.... I don't know how they do it.  For me, 9 is really loud with Grados, and even with the HD800 I listen under 10 o'clock.  Grados are too sensitive for me to use with the HDP internal headphone amp.
 
I doubt the volume pot differs that much, I think it's more people's listening levels vary a lot.

 
I disagree. Our units clearly don't have the same pot. Like I said before, your volume positioning doesn't make any sense to me. When the volume is OFF it's at 7 oclock, right? So when you just TURN ON the unit it's already at 8 oclock. That means you are listening at almost lowest possible level...with a 300 ohm headphone.
 
This is from an Amazon reviewer:
 
"With the unit standing upright on the stand with the volume knob at the top, the off position is at 7 o'clock, and the max position is at 5 o'clock. There is no sound that comes from the unit until the knob is turned to 8:45-9 o'clock. The volume will suddenly come up at that point."
 
 

 

[cravenz]

Yeah I have to agree. To some extent, there are variables such as us being used to listening to really loud or soft sound, but my 702s were no where near the right level at 10am. My D10 as a dac/amp with my IE8 also only comes on around 7 am but only has volume at around 8:30 am or thereabouts. It's not next to me, but there is a fair bit before the volume comes up and the same with the HDP. I myself can't fathom someone listening to it at 9am with full sized headphones, doesn't make complete sense to me on the HDP and even my M-Stage. I think some people could like it at say 11am, but anything lower to me just sounds like I would be straining to hear music. But then again, some people are more sensitive to volume at different levels. Such is the complexity of the human body I guess. I supposedly have very sensitive hearing cos' of the noise floor issue, but trust me, I listened to the 702s past 12 from my recollection; and it is past 12 or thereabouts on my M-Stage as well; and I would find 10 am way too soft

my opinion of course! that and the fact that there are always other variables that come into play, but I won't get into that.
 
on a side note, my replacement HDP has arrived. Crossing fingers that it isn't the same unit, I vaguely remember bits of the serial number. Anyhow, will be picking it up tomorrow since I wasn't home earlier and I sincerely home I get a nice working unit.

 

[bcwang]

 
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I disagree. Our units clearly don't have the same pot. Like I said before, your volume positioning doesn't make any sense to me. When the volume is OFF it's at 7 oclock, right? So when you just TURN ON the unit it's already at 8 oclock. That means you are listening at almost lowest possible level...with a 300 ohm headphone.
 
This is from an Amazon reviewer:
 
"With the unit standing upright on the stand with the volume knob at the top, the off position is at 7 o'clock, and the max position is at 5 o'clock. There is no sound that comes from the unit until the knob is turned to 8:45-9 o'clock. The volume will suddenly come up at that point."
 
 

Actually, that sounds about right.  Mine clicks on around 8 but doesn't really make any sound until 8:45-9.  And yes, I do listen at just slightly the level both channels equalize.  In fact, on my Grado's I set it to just when they equalize as that is extremely loud already.  With the HD800 it is enough to listen to lots of music comfortably.  I only have to turn it up for softer recorded jazz or classical pieces, but rock and pop is plenty loud around 9-10 o'clock.
 
When my cousin came over and listened he immediately turned it to 12 o'clock...so I think people definitely listen at far different levels.  I'd think there is much more variance there than a volume pot unless it was defective.

 

[cravenz]

I’ve just received my HDP replacement and I first tested it with my Sony IEMs and found that hiss was minimal at most, but the main thing that I found was that I had NO volume pot issues this time round i.e. if I shift the volume pot, I don’t have crackling noises on my Sony’s.
 
I then shifted to my IE8s because they are the acid test for me. Unfortunately, I still experience hiss, but again, I have NO volume pot movement issues which confirms to me that my volume pot on my last unit was broken. I had crackling noises on both IEMs on the last unit, but this unit now has no crackling noises whatsoever at any level of the volume pot from 7 – 12 and obviously, now I have half a mind to say that it was not my earphones that gave way coincidentally the last time since this unit has no crackling noises!
 
Also, when I unplug the USB, the hiss level drops, but I can still hear it. Any suggestions on how to lower the hiss from my laptop side of things? Nothing is heard on the 702s though obviously, so I figure an impedance adapter would be the best route?
 
My 702s have no channel imbalance now I believe and also, yes, I can listen to it at 10 on the dial, I think 11 onwards has more ‘body’. On another note, everything seems to have more mid-bass so I’m unsure at the moment and now I’ll try and let the unit burn in to see if that tones down.
 
This is just my update for now; and will update in the future if anything changes.

 

[bcwang]

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Also, when I unplug the USB, the hiss level drops, but I can still hear it. Any suggestions on how to lower the hiss from my laptop side of things? Nothing is heard on the 702s though obviously, so I figure an impedance adapter would be the best route?

Do you have anything else connected to the HDP?  I'm surprised your hiss level dropped by disconnecting the USB cable unless you also have the analog cable hooked up as well and are actually hearing more of a whine from a electrical loop.  What if you switch the knob to an analog input, does the usb cable being connected make any difference to the hiss?

 

[cravenz]

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Do you have anything else connected to the HDP?  I'm surprised your hiss level dropped by disconnecting the USB cable unless you also have the analog cable hooked up as well and are actually hearing more of a whine from a electrical loop.  What if you switch the knob to an analog input, does the usb cable being connected make any difference to the hiss?

I have to admit that the hiss actually annoys me lol. With no music playing, on usb and unplugging, hiss drops, so I guess it is computer interference. I have nothing plugged at the moment. Switching to the other settings like digital etc drops the hiss a little like unplugging the usb. I am assuming it is because no signal is being run through.