New H20 Signature S250

With the interest of a local audiophile who had an H20 (non-sig stereo) model on loan, I had the opportunity to audition this in my home system. As a Sound-Lab A1 owner with CAT JL-3 Signature amps and a 10-year old Counterpoint NPS400 hybrid amp, I was eager to hear how the H20 amp would compare to both a reference amp and a more affordable ($1500-2000 on the used market) amp. All amps were powered on for at least an hour before listening, and were only powered down for the brief periods of swapping IC and spkr cables and then powered back on.

There is much issue on MIT cables with the H20 amps in the Audiogon forums and from Mr. Ho when he wrote to me after my initial impression of his amp. But because I use a 25' MIT 350 EVO single-ended cable from an Aesthetix Callisto Signature line stage to the CAT amps, this cable was what I initially used to compare the amps. The CAT amps do not support balanced connections.

The H20 has outstanding extension and resolution at the frequency extremes. There was however, a huge dip in the midrange. On two different LP recordings, the singers, guitar and keyboard players were very much recessed on the stage relative to the other members of the band. I tried turning up the volume to bring the performers together, but this only caused the bass player and drummer to overpower the performance. In all the ARC, Counterpoint, Wolcott and CAT amps I have owned, my system has never had a tonal imbalance like this.

Another concern with the H20 had to do with image widths. Singers, guitar players and pianos all had a very narrow field. Piano image size was only a couple feet wide. The H20's image compression was very evident after hearing the same music minutes before with the CATs which brought the piano’s presence to realism. The Counterpoint was not all that far behind the CATs in this regard.

The other problem with the H20 was its lack of dynamic contrasts. I could not get the loud peaks in the music to really come out into the room. With the CATs and less so with the Counterpoint, segments in the music would build up and briefly become quite loud and then return to a softer level. There was very much a defined volume range for which the H20 played the music and the brief loud peaks reached by the other amps were just not to be achieved with the H20.

The whole issue of decays and harmonic richness was not to be an expected strength here and indeed, the H20 was very much like any other solid state amp I have heard in my system and elsewhere.

Upon sharing my findings with Mr. Ho, he told me of the incompatibility with his amps and the MIT cables. With all the praise I have read here on these amps, I wanted to do anything I could to get out of them what others have written. The only option I had was to use a 14’ NBS Statement XLR cable and run it across the room to hear this setup. This required me to bring the component rack a few feet into the room vs. being at the back wall, but the effort was well worth it. I used adaptors to run the NBS into the CATs.

Huge difference with the NBS balanced cable!!! Now the H20 had very good tonal coherency. Images were still a bit narrow, but a definite improvement here. I was very pleased with these changes.

The now far more accurate tonality brought on great musical enjoyment but at the same time, it made clear the subtle deficiencies that were masked before due to the recessed midrange. With piano now having more accurate presence, the notes were more clearly connected rather than being distinct from one to the next; intricate guitar work was a bit slurred from one note to the next as well. The Counterpoint did not fair very well here either, but with the CATs, the space between each of the notes was very clear. Without the CATs on hand to hear this capability, the H20's resolving power fairs quite well.

With the H20, there was still a definite reduction of each performer occupying a realistic volume of space on the stage. However, with the improvements brought on with the balanced NBS cable, overall, the result here was most impressive for an amp of this cost....and a solid state amp at that. Still this was one area where the Counterpoint clearly excelled over the H20. The 3-dimensionality, bloom, decays, etc., are very significant characterizations I listen for when evaluating audio components. To the H20's credit, it does have a more refined and resolving top-end than the Counterpoint.

The H20's dynamic compression issue with the single-ended MIT cable was now much less an issue with the balanced NBS. This was one area I was pleased to hear an improvement as I would have little tolerance for an amp of such dynamic compression.

One new problem with the balanced cable was that there was now a fatigue in the upper trebles. If anything, the NBS is more soft and a little less resolving on the top than the MIT, and yet there was now an annoying ringing in not the attack but the trailing (decay) of primarily percussion notes. I suspect this issue would make the H20 very system critical to find a balance elsewhere in the system to tame this characteristic. And perhaps this fatigue could be partly resolved with adjusting the Sound-Lab brilliance controls. Trying other cables could very well resolve this problem as well. Since I had this amp just for a couple days, I did not have the time to investigate these opportunities.

So what is the reason for the dramatic change between the two listening sessions? 1) is the H20 indeed incompatible with the MIT 350 EVO? OR 2) does the H20 simply need to be run with a balanced signal to achieve its potential? My gut feeling is the latter as the NBS and MIT cables used here have very subtle differences in my system and this has been true when I've run them with the Counterpoint as well as previously, the Wolcott monos. And the same was true when I had the BAT 31SE line stage before the Aesthetix Callisto.

I have found the line-stage-to-amp link to be by far the most critical of cable differences. And I have found only a few products capable of retaining the 3-dimensionality in the music; the NBS Statement and MIT 350 EVO & Reference Proline cables are among this group.

So yes, the H20 can perform incredibly well with the Sound-Lab speakers. When run with the "appropriate" cable(s) with the balanced inputs, this amp can be very impressive. The simple fact that it does not have listener fatigue, that I often associate with many solid state amps, speaks well for this amplifier. And that it faired so well to amps of the caliber of the CATs says a lot about the H20's potential and what I suspect exists to a higher degree in the Signature and mono amplifiers developed by Mr. Ho.

I hope to learn more from Mr. Ho on whether or not the H20 amp really needs to be driven by a balanced signal to work at its best.

John

A few comments and clarifications to answer some comments on my previous posting here:

Muralman1: As a long time owner of Magnepan 3.3 and then 3.5 speakers, as much as I loved them, they were far more the challenging speaker to play their magic than the Sound-Lab. When a speaker has such incredible 3-dimensional cpabilities as the Magnepan, but also has very clear dynamic limitations, it is tough to get such a speaker do it all. And throwing 1000w amps at them is not going to do it even remotely to the level of a far less "powerful" amp with the Sound-Lab.

I have not heard a big Apogee speaker for nearly 20 years. And this was never in my home. So I have no idea how a speaker like the Scintilla would compare sonically to the A1. But I do understand the H20 was designed with the Apogee speaker so I would expect it to perform its best with that speaker line. I wish we were closeby as I'd be willing to lug over the CAT amps to try with your Scintillas. I would have to call Ken Stevens first to make sure they could handle the 1-ohm load but I believe they can be configured to drive such speakers. I understand them to handle a load under 2 ohms with ease. And I suspect with some modifications, they could be turned into welding torches! 8-)

Concerning me going with the H20 signature, the CAT amps were so far ahead of the std H20 that I do not see me letting go of the CATs anytime soon. They do dynamic contrasts and the leading edge attack of the notes that you simply need to hear to believe. And they portray volume of space that the H20 does not even begin to do. One local audiophile who visited me said he had never before heard a tube amp with such speed as this. And he is much more detail oriented and particular to perfection in a music reproduction system than I am. With all the tube amps I have owned and have heard before, I could not have said it better. It was this attribute that caused me to purchase this amp.

I don't want to go into a count-by-count comparison between the amps because that was no my intent of my report here. The dramatic difference in cost alone makes this kinda silly. But I wanted to hear the H20 as I suspect it could be an ideal match for my home theatre system which I want to be fully ss based.

My initial report here was to state the areas where I felt the H20 was lacking relative to a "reference" product but also conclude that for its price point, it performed remarkably well. I also wanted to point out that an older "low-cost" model like the Counterpoint holds its own to today's great solid state amps in that it still does a 3-dimensional presentation like no ss amp I have tried in my home.

Audiofankj: I can so very much relate to trying cables in my system that just did not work at all. One immediately comes to mind: the highly raved Audioquest Diamond. It completely obliterated all the harmonic richness, bloom and decays in the music that I had worked so hard to achieve. That is a cable I too will never consider at least in the context of a tube-based system.

My MIT cable experience is strictly from line stage to amp. Again, I have no experience with MIT speaker cables. A few years ago I tried the MIT ICs as they are rather affordable in longer lengths. And I was mightily surprised at their performance relative to the NBS. And with 5 different tube amps and 3 different line stages, I did not at all have tonality problems with the MIT 350 when compared to the NBS Statement. The NBS has been my reference cable for the last 5 years since replacing Cardas Golden Cross, Harmonic Tech One and SilverAudio Passionata.....all of which are excellent cables for the price.

When I had balanced amps I ran with a 20' MIT 350 Ref Proline XLR cable with the same results, no tonal coherency problems nor fatigue issues at all. Unfortunately I have these loaned to a friend or I would have tried them with the H20 to once and for all put the "to MIT or not to MIT" or "single-ended vs. balanced" issues with the H20 to bed.

So it is NOT a global issue of MIT incompatibility with tube amps. Some other factor is going on out there but I have not heard it here. And the implementation between the NBS and MIT is about as different as two cables can be. How these two cables can both sound so exceptional and remarkably similar with the wide range of electronics and with Talon Khorus, Magnepan 3.5 and now Sound-Lab A1 speakers causes me to believe it is at least, a non-issue for me.

I might add that not every MIT cable sounded the same for me. I had a 30' M1 IC on loan for a month and I could not get it to perform like the MIT 350. The M1 was very sterile whereas the 350 brought on dimensionality that was right behind the NBS.

Woodburger brings up a concern that I share: maybe another cable will resolve the interactions with the H20 but if it takes away the magic elsewhere that we had before, then it's a "this for that" issue. And giving up many attributes in my system just to correct an interaction problem is not acceptable.

Bob: Thank you for pointing out the input impedance issue. I had no idea the H20 was so low in single-ended. This could very well have been the problem running the H20 singl-ended from the Callisto and not an MIT cable issue at all. I do not know if the Callisto has the same "requirement" as the Calypso in terms of needing to see a higher impedance load.

Only a month or so ago did I move my equipment rack from a side wall to the wear wall. Up to this time, I was using the NBS XLR cable to the CAT amps with adaptors. With the greater distance, I now use the 25' MIT cable and run from the SE outputs of the Callisto. Phono and DAC inputs to the Callisto are both through balanced NBS Statement XLRs.

I might add that switching configurations with the CATs and the Counterpoint during this amp evaluation did not cause dramatic changes as was clearly the case with the H20. So it was definitely not an issue of connectors or cables not being burned in.....except for the possibility with the H20's circuits/connectors themselves. Still, there is absolutely no way the problems described in the initial run with the H20 could be attributed entirely to this.

John