Zähl HM1 - Reference Headphone Amplifier

[Frankie D]

Listening to “Flying Beagle” on the Sus plus HM-1. This album, recommended by @warrenpchi sounds terrific. It is a jazz/funk album from Japan in 1987 I never heard about.

The opening and bass on “Look Your Back!” grabs you with the HM-1. Nice reproduction of the horns.

The bass on “Baby Talk” really hits. Love the interplay with the piano. Great track.

On another thread someone was mentioning the Enleum Amp 23R. I don’t see it vs the Zahl HM-1. It has been awhile since I heard it, but I do not remember thinking this is competition for the HM-1. Do any of you have experience with it?

 

[warrenpchi]

Listening to “Flying Beagle” on the Sus plus HM-1. This album, recommended by @warrenpchi sounds terrific. It is a jazz/funk album from Japan in 1987 I never heard about.

Yeah, holy cow, "Look Your Back" just kicks us in the face from the get go!

 

[IanB52]

Listening to “Flying Beagle” on the Sus plus HM-1. This album, recommended by @warrenpchi sounds terrific. It is a jazz/funk album from Japan in 1987 I never heard about.

The opening and bass on “Look Your Back!” grabs you with the HM-1. Nice reproduction of the horns.

The bass on “Baby Talk” really hits. Love the interplay with the piano. Great track.

On another thread someone was mentioning the Enleum Amp 23R. I don’t see it vs the Zahl HM-1. It has been awhile since I heard it, but I do not remember thinking this is competition for the HM-1. Do any of you have experience with it?

HM-1 can't do the bounciness of the Enleum, but you can sort of emulate it by using the Class A mode, and turning the treble and stereo width back two notches from unity. HM-1 has way more resolution and better stereo separation, but you can get a surprisingly similar sound with the EQ and width settings.

 

[RustyGates]

HM-1 can't do the bounciness of the Enleum, but you can sort of emulate it by using the Class A mode, and turning the treble and stereo width back two notches from unity. HM-1 has way more resolution and better stereo separation, but you can get a surprisingly similar sound with the EQ and width settings.

Its not that simple. I've been going back and forth between the two and can't emulate the sound of the AMP-23R on the HM1. Reducing stereo width on the HM1 just collapses the SS - two notches down and its essentially mono, its nothing like the AMP-23R which does have a great stage, but not as wide as the HM1. It has incredible depth though and imaging. Increasing bass on HM1 gives greater bass presence on tracks, but it still doesn't have the same plump, bouncy and tight bass response of the AMP-23R.

Changing from Class A + Servo to Class A has minimal impact with my headphones and doesn't help to emulate the AMP-23R.

Yes, the HM1 has better clarity on its resolve with a lower noise floor, but the AMP-23R is just as resolving i.e., there is not a single nuance of a track you won't hear on the AMP-23R.

In terms of 'accuracy' or 'neutrality, of course, the HM1 wins. But this not a factor of 'enjoyment' for me, in which tuning will be very much a personal preference. The AMP-23R's output MOSFET's (Exicon) simulate DHT characteristics quite well with the control of SS, and you won't be able to 'EQ' this is any way.

The AMP-23R's sound seems to vary heavily with the DAC. Tambaqui with 23R @ 2V is very different to Chord Mojo 2 with 23R @ 2V, with the former sounding faster (incredible PRaT), more open and clearer with better bass.

I am keeping both the 23R and HM1 as they are very different experiences.

 

[IanB52]

Its not that simple. I've been going back and forth between the two and can't emulate the sound of the AMP-23R on the HM1. Reducing stereo width on the HM1 just collapses the SS - two notches down and its essentially mono, its nothing like the AMP-23R which does have a great stage, but not as wide as the HM1. It has incredible depth though and imaging. Increasing bass on HM1 gives greater bass presence on tracks, but it still doesn't have the same plump, bouncy and tight bass response of the AMP-23R.

Changing from Class A + Servo to Class A has minimal impact with my headphones and doesn't help to emulate the AMP-23R.

Yes, the HM1 has better clarity on its resolve with a lower noise floor, but the AMP-23R is just as resolving i.e., there is not a single nuance of a track you won't hear on the AMP-23R.

In terms of 'accuracy' or 'neutrality, of course, the HM1 wins. But this not a factor of 'enjoyment' for me, in which tuning will be very much a personal preference. The AMP-23R's output MOSFET's (Exicon) simulate DHT characteristics quite well with the control of SS, and you won't be able to 'EQ' this is any way.

The AMP-23R's sound seems to vary heavily with the DAC. Tambaqui with 23R @ 2V is very different to Chord Mojo 2 with 23R @ 2V, with the former sounding faster (incredible PRaT), more open and clearer with better bass.

I am keeping both the 23R and HM1 as they are very different experiences.

I didn't compare the two side by side. Based off of memory those settings give me a similar experience, but you would be the expert here being able to compare directly.

Personally, I was not impressed by the Enleum. I had it for a month and my experience was a sound stage that was halfway to mono and fairly low resolution/lossy, rolled off treble, but some nice harmonic color and fluid/bouncy feel. I used it with my EMM DA2 and Mytek Manhattan II, which are 7 and 10 volts respectively. Much of that musicality comes from more center channel emphasis (i.e. more mono) and more midrange emphasis, which the HM1 can sort of do if needed. Different strokes, but I wouldn't bother with it again.

I do agree that the Class A mode on the HM1 isn't that different, but again a move in the similar direction.

 

[RustyGates]

I didn't compare the two side by side. Based off of memory those settings give me a similar experience, but you would be the expert here being able to compare directly.

Personally, I was not impressed by the Enleum. I had it for a month and my experience was a sound stage that was halfway to mono and fairly low resolution/lossy, rolled off treble, but some nice harmonic color and fluid/bouncy feel. I used it with my EMM DA2 and Mytek Manhattan II, which are 7 and 10 volts respectively. Much of that musicality comes from more center channel emphasis (i.e. more mono) and more midrange emphasis, which the HM1 can sort of do if needed. Different strokes, but I wouldn't bother with it again.

I do agree that the Class A mode on the HM1 isn't that different, but again a move in the similar direction.

7 to 10V!!! The AMP-23R is rated for 2V line-out (its sweet spot) and you're essentially overloading its input buffers, and I can guarantee there will be a performance hit at this line level. As mentioned before, the DAC I use has a large impact to the SQ of the 23R.

Ultimately, you need an amp that suits your set-up the best, and the HM1 is incredible and can better cater for a wider input voltage range (though its HP output is limited to 10.9V whereas the 23R is a 15.6V max output)

 

[IanB52]

7 to 10V!!! The AMP-23R is rated for 2V line-out (its sweet spot) and you're essentially overloading its input buffers, and I can guarantee there will be a performance hit at this line level. As mentioned before, the DAC I use has a large impact to the SQ of the 23R.

Ultimately, you need an amp that suits your set-up the best, and the HM1 is incredible and can better cater for a wider input voltage range (though its HP output is limited to 10.9V whereas the 23R is a 15.6V max output)

That makes sense. It did clean up somewhat when I bumped the DAC output down to 5v, but yeah maybe better performance could be had. The HM1 gets better the harder you hit it.

However, that doesn't change the 9:00-3:00 stereo image thing. Lots of amps do this because it emphasizes vocals, bass, and drums, but rubs me the wrong way. I did find it to be very musical, however.

 

[Somafunk]

This may be of interest to some folk.

An interview by Jamie Lidell with Michael Zähl and Mark Ernestus of AM1 mixing console fame, interview starts at 12mins in (approx)

Michael Zähl, former engineer and designer of the main custom made mixing console at the legendary Studio of Conny Plank and Mark Ernestus, long time producer known from projects like Basic Channel and Rhythm & Sound had a special encounter which led to the collaborative development of AM1 - the state-of-the-art pure analog mixing console.

I speak to these two excellent individuals about how they came to meet and the 9 years journey to make a mixing desk the likes of which we’ve never seen before.

 

[Somafunk]

As I linked to above regarding the Zähl AM1 mixing console here is an example of how clean it can sound with Mark Ernesto at the helm of it.

Phasey electronic dub with the cleanest fades produced and mixed to perfection

https://i.imgur.com/Z7CMPcj.png

 

[nyev]

I’ve read that the ZMF Atrium pairs best with tube amps, in terms of getting the best dynamics. Has anyone tried the Atrium Open on the HM1 and compared with something like, say a WA23?

As I mentioned in an earlier post, I purchased a Caldera to pair with the HM1 - went for the November 2024 limited that went on sale today.

I also purchased a used Atrium Open set, which wasn’t planned and possibly may be something intend to try for a while and then sell. Wondering if I really need to try a tube amp to get the most of the Atrium….

 

[Frankie D]

I’ve read that the ZMF Atrium pairs best with tube amps, in terms of getting the best dynamics. Has anyone tried the Atrium Open on the HM1 and compared with something like, say a WA23?

As I mentioned in an earlier post, I purchased a Caldera to pair with the HM1 - went for the November 2024 limited that went on sale today.

I also purchased a used Atrium Open set, which wasn’t planned and possibly may be something intend to try for a while and then sell. Wondering if I really need to try a tube amp to get the most of the Atrium….

I have not directly compared to my Zahl HM-1. However I have made comparisons directly to my Mass-Kobo 465. The Zahl and MK duke it out for my best amp and are very close. So I think you will be fine with both on the HM-1. Both will be great.

That said, when I was doing some comparisons, the ZMF Decware is an amazing amplifier for the ZMF Atriums and Verites ( dynamic HPs only ). While I thought my 465 was just as good as the Decware using the Atrium Closed ( I suspect the extra bass of the closed synergizing with the bass and speed of the 465), the Atrium Open and Verite Open sounded better to me ( a beautiful liquidity to the sound ) on the Decware. I should also mention the tubes on the Decware were not the standard set. I expect this to be the same with the Zahl ( and you will have some controls at your disposal as well ).

So your Caldera will sound better on the Zahl HM-1 in my view and the Decware will outshine it with the Atrium Open. This is not to say the AO will not be great with the Zahl. It will, but the Decware amp will be better if you wanted a specialized amplifier for the AO.

Also, other tube amps will probably not equal the Decware for the AO specifically. So please do not think that any tube amp will do as I described.

Anyway, hope this was helpful. And as you will be fine with the Zahl, you can audition to see if want a tube amp and which one.

 

[nyev]

That said, when I was doing some comparisons, the ZMF Decware is an amazing amplifier for the ZMF Atriums and Verites ( dynamic HPs only ). While I thought my 465 was just as good as the Decware using the Atrium Closed ( I suspect the extra bass of the closed synergizing with the bass and speed of the 465), the Atrium Open and Verite Open sounded better to me ( a beautiful liquidity to the sound ) on the Decware. I should also mention the tubes on the Decware were not the standard set. I expect this to be the same with the Zahl ( and you will have some controls at your disposal as well ).

So your Caldera will sound better on the Zahl HM-1 in my view and the Decware will outshine it with the Atrium Open. This is not to say the AO will not be great with the Zahl. It will, but the Decware amp will be better if you wanted a specialized amplifier for the AO.

Also, other tube amps will probably not equal the Decware for the AO specifically. So please do not think that any tube amp will do as I described.

Anyway, hope this was helpful. And as you will be fine with the Zahl, you can audition to see if want a tube amp and which one.

Thanks, makes sense and very helpful!

 

[duranxv]

I have not directly compared to my Zahl HM-1. However I have made comparisons directly to my Mass-Kobo 465. The Zahl and MK duke it out for my best amp and are very close. So I think you will be fine with both on the HM-1. Both will be great.

That said, when I was doing some comparisons, the ZMF Decware is an amazing amplifier for the ZMF Atriums and Verites ( dynamic HPs only ). While I thought my 465 was just as good as the Decware using the Atrium Closed ( I suspect the extra bass of the closed synergizing with the bass and speed of the 465), the Atrium Open and Verite Open sounded better to me ( a beautiful liquidity to the sound ) on the Decware. I should also mention the tubes on the Decware were not the standard set. I expect this to be the same with the Zahl ( and you will have some controls at your disposal as well ).

So your Caldera will sound better on the Zahl HM-1 in my view and the Decware will outshine it with the Atrium Open. This is not to say the AO will not be great with the Zahl. It will, but the Decware amp will be better if you wanted a specialized amplifier for the AO.

Also, other tube amps will probably not equal the Decware for the AO specifically. So please do not think that any tube amp will do as I described.

Anyway, hope this was helpful. And as you will be fine with the Zahl, you can audition to see if want a tube amp and which one.

What's even better is using HM-1 as a pre-amp into the MK 465 I love the fact that not only is it great to A/B DAC's, but the tone controls (especially the soundstage knob) are just well implemented.

 

[nyev]

This probably falls into the category of a non-issue. But I just noticed that if I nudge the volume up from min on my HM1, right after the point where you can hear the relay click, and music can first be heard, almost all of the signal can be heard through the left channel only. Nudging the volume up a hair more, the right channel kicks in and everything is centered. I tried this on the second channel and the same thing happens.

Anyone else get this on their HM1’s? As I said not an issue, but just wondering if this is normal. And yes the balance dial is at the centered position.

 

[TheAttorney]

Anyone else get this on their HM1’s? As I said not an issue, but just wondering if this is normal. And yes the balance dial is at the centered position.

My HM1 doesn't do this as far as I can tell. But it is very common for such continuous tracking volume pots to have an extreme channel imbalance at the very start of the tracking. It will vary from one pot to another and is nothing to worry about. It shouldn't be anywhere near your normal listening levels - if it is, you've probably got a gain/sensitivity mismatch somewhere in your system.

Stepped ladder resistor types of volume control won't have such imbalance issues, but they have a bigger practical issue in that the incremental volume change can often be quite large (e.g. 2 or 3 db per step) which is not as nice as having a continuously variable level change. This is a simplification - there's all sorts of clever designs that can minimize such effects. AFAIK, HM1's volume pot is a fairly basic ALPS model, so it's a wonder that it sounds as good as it does.