AMT Loudspeaker kit
I had my first listen (although you won't be impressed by the circumstances! It's a very hot summer!) and I am truly amazed. I think my wife also! I often build some very crackpot projects, and when she saw the pvc tubes coming out of the box , she thought that this was some more lunacy. Having given them an initial quick listen she is quite stunned.
Early conclusions:
-As you said, the soundstage is very large, there is a sweetspot but it's easily a couple of metres across,
-Vocals are absolutely stunning. Randy Crawford and my wife's favourite Celine Dion are alive and standing just off centre and 1/2 metre behind the speakers,
-Bass is not as strong as I thought it would be, but given the cabinet volume and driver size this is understandable,
-I managed to pick out at least 3 instruments I've not heard before, primarily mid and upper.
-Grosvenor Washington jr sax is full and rich.
Of course I have to let them loosen up, find decent positions.
I have a friend in SA whom I've told about the speakers and his comment was, "sounds strange, but I'd love to hear them." At least he has an open mind!
Second impression:
I'm usually disappointed with the sweetspots of most speakers as I seem to be particularly sensitive to changes between left and right. It can be bad enough that if I've found a good position and I turn my head slightly, it goes away. With the AMT's turning my head makes no difference! Many thanks for all your help with the AMT and also your ongoing comments.
Conclusion
All in all it was not a difficult kit to build. The results far exceed the very reasonable cost and labour required to complete the set. I believe it would take 15 times the cost to buy a comparable commercial set of speakers and even then the sheer breadth of soundstage will probably not compare. The personal joy in building something which is so good sonically, has my personality in its finish and is not another brown box off the shelf, and I can use on a day to day basis, makes the whole experience even more worthwhile. I can't wait to hear an RMT.
One factor which is invaluable, is the outstanding help I've received along the way from the designer. How much is this worth, even if you can find it in the commercial world? What a breath of fresh air in the over-hyped, fake world of commercialised high end sound systems around today.
Ruvane (U.K.)
e-mail: rcbernstein@netscape.net
Concerns: MP-DAC after the latest updates (OS-CON elco's!)
Date: thirsday december 31 1998 15:10
john;
this is no longer acceptable. Lately I experienced an emotional charge increasing all the time.
I'll have to sue you because:
Attention, emotional dangers
don't consume lightly
You'll have to warn your customers and again: THANKS, THANKS. At this moment I enjoy a free concert by Paolo Conte, it's live!
Fons de Boeck
Subject: 6N1P tube in A-50 power amp
Date: wednesday december 16 1998 13:08
how is this possible
could this be achieved for that price
where am I
THIS IS ANALOGUE
THIS GETS TO YOU
THESE ARE EMOTIONS
THIS IS UNIQUE
THANKS
FONS DE BOECK
MP-DAC
Date: tuesday december 15 1998 14:38
Dear John,
Just a short message while being very busy on my job.
Yesterday I visited a colleague who had a Meridian CD-player on lend from a dealer. It's the CD-508-HD with the Crystal 24-bit DAC-chip. I had my own MP-DAC 24-bit with me and we could compare both very easy: the transport in the Meridian is the newest Philips CDM-12, a very nice transport and a nice player, really. But the MP-DAC should be classified in a (much) higher range. We both could confirm this.
Regards
Rudo Meijer
AT MP-DAC
Date: monday january 8 1999 17:12
Dear John,
A short mail as a follow up for my last mail concerning the Meridian CD-player and the APN's MP-DAC.
Some year and a half ago I was anxiously looking for a better transport to connect to the MP-DAC. At that time I had the elder 20-bit version of the DAC. I then had various transports to compare, such as the Audio Research CD2 and models from Meridian, Teac, CEC and Philips.
The AR cd2 is an integrated player, equipped with a digital output, so it can also be used as a stand alone transport. The result in combination with the MP-DAC was quite good. Although the player as a whole scored better then my MP-DAC. It's really a very good player. But well, the price was over US $ 5,000.-! Last year I switched over to the 24-bit version of the MP-DAC and that was really a big step ahead. Last weekend I compared my DAC with the same AR and the result was quite a big difference in favour of the MP-DAC. This DAC really lets you hear more, with uncomparable authority and ease. So it deserves a very good transport ....
But you already knew that for a long time.
Rudo Meijer
APN Do-It-Yourself projects (spring 2000)
Dear Audio Technicians,
I'm not a technician, I'm good at languages and therefore I'm a typical 'Alpha' man. Although I always had an affection with electronics. As a young man I experienced with various circuits and learned that if a diode is mounted in the wrong direction a whole power amp can blow up. That's why I have a fear to switch on the mains of a d.i.y. project!
It all started with loudspeaker boxes such as the Karlsson resonator with the famous 9710M from Philips and socalled 'Edwin' amplifiers as published in 'Elektor'.
In 1992 I decided, after twenty years of having built nothing at all, and having enjoyed better equipment (Quad, Thorens, IMF etc.) to start building A-25 power amps as designed by APN (formerly 'Audio & Technique'). I first heard those amps at a friends' home and I was totally over the edge! At the cost of half a year of my lifetime I constructed these two mono power amps. Because of my uncertainty to 'switch on' I visited the offices of APN to let them control my kits and what came out: my uncertainty wasn't necessary, just switch on and play! These A-25's where quite complicated to build, at least for me and certainly when compared to the more recent designs from A&T.
Meanwhile I'm a 'regular customer' at APN. I bought the kits for the P-11, the MP-DAC and the A-50 without even listening on beforehand and the construction went with ease and great pleasure. Within a week, per design, all was completed. What remained was a visit to their offices where there was always understanding for my uncertainties. The coffee is good, you're welcome and I enjoy the typical Rotterdam humor: 'well mr. De Kort what's it I see there? Is that a LED? I never touched them after finishing my education ...'
Until now it seems that I'm a good do-it-yourselver (or the designs and construction plans were just good..). All projects worked all at once without any problem. I have to speak appreciatingly of those fantastic kits which are delivered by mail, complete and with good drawings and are a guarantee for a fantastic musical experience.
I've always been a true lover of Quad equipment (33-303-405-66-606) but I got rid of the lot including my ESL-63's! What's now playing at home and what I have built by myself may be compared with any factory-made equipment. My listening friends are perplexed and don't understand that I've built all this on such short notice with these fine results.
My greatest experience I had was with the MP-DAC, that gave an unimaginable improvement. The CD's I had, which gave a flat and dull result, now started to 'live' and I had to replay my total collection of CD's to rediscover their qualities. The images became wider and deeper and details are unsurpassed, it's really dramatic while for a very affordable price.
Two remarks are there to make: I'm a lover of heavy and serious popmusic (Pink Floyd, Peter Gabriel, Marillion, Genesis etc.). That's why I made a four-way system with five units in it. The filtering and the wiring inside are in 'Rolls Royce' quality and the units came from Scan Speak and Vifa. When combined with the A-50's this gives a marvellous result.
I don't understand why APN aims at designs like the PMT's and AMT's which are relatively 'light footed'. I understand their spaciousness, but sometimes I want to "feel' the sensation of a live concert. Therefore other types of designs are needed.
I really have just one problem left: there's nothing more to build!
Many thanks
Jan Kort
Digital sound quality
In my system with the Teac VRDS-10 as a (modified) CD-drive, the MP-DAC, the P-11 and a pair of A-50's driving Martin Logan's full range electrostatics I recently changed my digital interlink for the more expensive one with BNC connectors. And once again a veil was taken away! The image is stunningly open with dimensions never heard of!
Compared with my Goldmund record player with the Van-Den-Hul Grasshopper in it the differences between analog and digital simply vanish!
Thanks again for this wonderful achievement.
J.H.M. de Vreede
A-50 (september 7th 2001)
Dear John,
My recently built A-50's are running and very well in my opinion. It is a real pleasure to listen to them and they run quite continuously when I am home.
Music rendition is quite delicate and most of the annoyances I experienced with the previous amp in the long run (sibillances and obstructions in HF + uniformity due to lack of bass) are gone. I compared the two amps briefly one afternoon thinking that the A-50 would completely overshoulder the Audiomat. Weirdly enough on A/B comparision I was surprised to find that this was not the case and the output of the Audiomat sounded quite nice in what it does fine. So I left it hooked to the speakers. The next morning starting my day with Bach violin/harpsichord sonata by van Asperen and Lucy Dael (Naxos), I found the sound so lean and uninvolving that I returned in the minute to the A-50 and with no desires since then to experience any more with the Audiomat. In fact I became bugged by all these A/B listenings I did lately which rely more on an obsessive analytical experience of music than an evaluation of the artistical rendition of musical performances. I am satisfied by the system how it is now and I find myself listening to performances from the first bar to the last which I never did before because I always stopped hurted by inaccuracies or fatigue. I was surprised for example to be able to listen to the concerto for celesta, string and percussion from Bela Bartok interpreted by Fritz Reiner (RCA), in its integrality. I remember that I could listen to only little moments of it with my system in the previous configuration. Last night I stood up after the last notes vanished and said "this is really beautiful".
IMO the A-50 has no flaws in what is basically necessary for music reproduction, tonal accuracy, timing and dynamics and it enables something which I realize recently is important for me and which which I could not formulate: to be able to percieve the silence between the notes almost any time.
Jean-Claude L. - Marseille - France
A-50
(january 30th 2002)
Comparing it with the Twin Tower from Pathos and the Audiomat Prelude
Dear John,
I finally could compare the A-50 to the Pathos TwinTower (PTT) with the kind assistance of Phillipe Faure (PhF) in the Eclipse Audioshop in Avignon.The speakers used for comparision were "easy" and expensive (E6000) Apertura Kalibrator (92 db for 1W) which are very good monitor speakers with very smooth transition between LF and HF drivers. Unfortunately, there were no "difficult" speakers around to listen to and compare both amp behaviours against more complex loads.
The set up was MicroMega DDrive>> AndioNote DAC2.1x>>> attenuator-A50 or PTT >>> Apertura Kalibrator.
The interface of the DAC with the Amps may be a sensible issue because the AudioNote output impedance is rather high (around 1.2kOhm). As far as I dare to know, it should function best with receiver inputs showing high impedance and low capacitance. The PTT input impedance is 100Kohm and the connection to the DAC was with Hms Grand finale 1m long interconnects (capacitance unknown). In case of the A50, the same cables were plugged in
two different attenuators for control of voltage levels at the A-50 input.
My DACT CT1 100Kohm DIY attenator box with 40cm of 60pf/m cabels to the A50 or an Audiosynthesis Passion Ultimate passive Preamp (10Kohm input impedance) with 1.5m of Hms duetto to the A-50 (cable impedance unknown).
The two attenuator-A50 combinations were briefly compared with the PTT. The A50 in association with the Audiosynthesis sounded generally closer to PTT than in association with the DACT. No harshness, no distorsion and a high transparency in any cases but an extension toward HF with the DACT that tended to subjectively attenuate Bass rendition. Comparisons thereafter were mainly done with the Audiosyntheis/A-50 combination.
To summarize the experience, both amplifiers were neutral, free of gross distortion with refined HF. The A-50 seemed more dynamic, percussive and produced a stage that was hugely more open than with the PTT. Switching from the PTT to A-50 was always granted by commentaries stressing out how impressive the difference was. The scene with the PTT shrunked enclosed in a sphere located between the speakers. Much wider with the A-50 although I
would have liked to experience some more depth possibly because the scene was more localized to the left and right speakers with a little less appearing in the middle field. One listener said it was one of the first times that the PTT was beaten, but he also said the PTT was still an excellent value given the price of the A-50 would be under traditional trading. I thought that he was a bit severe because I liked very much the coherency of the PTT. Another
fellow also trained to listen, coming in, prefered the PTT saying that the music lines were easier to follow and enjoy. In other words, that it was more ordered and ultimately more musical. It was his opinion that the differences were constitutive to the circuitry of the amps.
Retrospectively, I regret to have dismissed the DACT-A50 combination because I assume that the matching with the Audiosynthesis is far from perfect. This might have resulted in some HF roll-off and contributed to this slight lack of togetherness found with the A-50.
An active preamp from E.A.R.(model 834L) designed by T Paravicini, was hooked to the A50 just to listen if it would the job. It was dehooked fast. Not good for me, all the vividness, the energy and openess collapsed in a mellow and somehow sluggish presentation.
Then coming back home, I took advantage that the A-50s were out of the rack to recompare it in more details to the Audiomat Prelude C11(AMT), a 30W pushpull EL 34 integrated (6dB of negative feedback) equipped with a 100K pot which I had before the A-50 and did not listen to for 6 months. Volume control of the A-50 was with the DACT 100K and DAC was an Audionote 1.1x, speakers B&W 805 biwired. For the comparison, I used a CD from "la Nouvelle Revue du Son" published this month containing a panel of well-recorded tracks for evaluation of sound reproduction systems.
The difference in tonality of the two amps was enormous. The general pitch of the AMT was way higher than that of the A-50 where exploration of the Mid-LF and LF was scrutinized. On some tracks rendition by the AMT was agreeable (for example with clavicord or violin and guitar duos) and rendered precise by the apparent more compact width of the tonal range.
However these characteristics of the AMT were very disturbing to the reproduction of piano recordings in particular: the tonal and dynamic particularities of a given interpretation and the emotional impact were almost lost which makes that all performances sounded kind of alike. For example, the beautiful interpretation of Beethoven sonata by Maria Joan Pires (DGG4346636) made of reverie, strengh and love with the A-50, was leveled out with the AMT. On the other hand, the ample bass rendition with recordings with high bass content by the A-50 could sometime result in some imprecision due to room mode stimulation. But this is something I expected.
Then, I wondered about these differences. Was the AMT poor in the bass reproduction department or the A-50 "coloured" by HF roll-off? To answer the question, I drove the LF driver with the A-50 and the tweeter with the PMT and conversely. To my big surprise, I found that the problem with the AMT was not so much with Mid/Low reproduction (not as good as with the A50 though) but with the HF. For reasons, I don't understand (third harmonic distortion?), the general trends of the AMT, shift toward high-pitch and apparent compression of Low/mid information, was obtained when Mid/Low
driver was fed by the A-50 and tweeter by the AMT. Ductility was restored in the converse configuration (tweeter driven by A-50 and Low/mid by AMT).
Here I think I realized something important about compensation and
non-linearities in psychoacoustics. For example that you may decrease subjective perception of lows by increasing the highs. I played a little bit with the speakers biamped in the latter conformation and it was amazing how the sound could be tailored and opened by leveling the volume of the tweeter and mid/low driver depending on the recording. I understand that I could become a fan of biamping with 4 good monoblocks.
So now my personal conclusions are that the A-50 outperforms the AMT in all respects. On easy speakers, the PTT and A-50 are high levels amplifiers showing different personalities with the PTT being more reserved and refined and the A-50 more extrovert and dynamic. Whether and how I could manage to instil a bit more relaxation to its presentation, is a matter of reflexion and may be further experiments.
With my best regards.
Jean - Claude Lissitzky
MP-DAC Mk III Received januari 21st 2002
Well, this weekend I finally finished assembling my MP-DAC kit. Not due to anyone's fault but my own- just to many things to do. I purchased the parts kit without chassis, and built it into a rack chassis which I had purchased previously in quantity for some projects.
Assembly was straight forward for someone willing to follow instructions and with reasonable background knowledge of terminology. The only place I strayed from the instructions was adding a EMI line filter (for a little extra CMRR from line propagated HF noise), and where the grounding arrangements for the output connectors weren't clear, I used a dual conductor shielded Cardas hookup wire for the output signals, and had the connectors floating from the chassis.
I have to confess that I purchased this unit to use with my older Sony XA7ES CD player in my secondary system. However, after listening to it with my Sony SCD 777ES SACD player, I'm left with no possible conclusion except that the CD playback is better through the MP-DAC, using the Sony only as a transport. For Redboock CD, the MP-DAC is more coherent, more of a single piece of music, and retrieves more low level detail, with less glare or hardness. Altogether a fine piece, and this only after a few hours of break in, compared with a year an a half old SCD777ES. Now, SACD is still another matter, but I have to wonder if the Sony wouldn't be improved on SACD with a fully revised analog section, using thinking like the MP-DAC (zero feedback, heavily regulated).
Best regards,
Jon Hancock
Livermore - CA - U.S.A.
complete Hawk set
received on march 25th 2002
An audiophile music lover recently bought a complete Hawk audio set.
From top to bottom:
Nagra recorder
P-12
MP-DAC
two A-50's.
Not visible: the CD-drive, the record player and the phono pre-amp.
On the left a full range electrostatic loudspeaker.
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