I will admit to liking the way Hugh has voiced Aspen gear. I have a GK-1R in my main system and a TLP(Nirvana) in my bedroom system. I am mid-way through assembling an Orion system, so I have two 55N+ for Orion mids and highs, a newly built 100N+ for the Orion bass, and a 100N+ for the bedroom system.
To handle the demands imposed by the Orion bass drivers (two 10" XLS per side, minimium impedance = 2.45R), Hugh recommended that I build a 100N+ with 43v rails. Using a spreadsheet from SL's website, I found that building this amp to handle 10amps/channel would prevent the amp from being current limited in the range ~80 - 120Hz. To get 10 amps/channel, I needed 625VA transformers and 20 amp diodes. In the power supply, I used 2x10,000 Nichicon Gold Tune caps per channel bypassed with 100uf electrolytics (these are the black and white stocker caps that Hugh uses in the AKSA kits) further bypassed with a 0.1uf film cap (details are available, but since I'm writing over my lunch break at work, I don't have the details here).
So, I have two 100N+ amps on hand:
One is a stock 100N+ with 50V rails that has been playing in my main system or perhaps six months. I have bypassed the PS caps in this amp with 100uf 100v BG standards, otherwise this amp is absolutely stock.
The second amp was built to handle Orion bass, described above with 43v rails, etc. By now, it has about 250 hours of break-in time on it.[/list:u] During break-in of the 43v amp I thought (in comparison to the stock 100N+) that this amp was equally good on the high end and seemed to have a bit more spine when things get tough on the low end.
Yesterday afternoon--with the new amp well broken in--I spent a couple of hours listening to these two amps head-to-head. I mounted the two amps one on top of the other, plugged them into the same duplex outlet, and was able to get the cables swapped and get the music playing in less than two minutes. The recordings I used were (1) Minnesota Orchestra, Pictures at an Exhibition, cut #22 (Baba Yaga's Hut) on Reference Recordings, and (2) Pictures at an Exhibition, Dorian (pipe organ), cuts #1 and 2. Both of these CDs have serious bass and are reasonably well balanced across the entire sonic spectrum.
Every time I switched away from the 43v amp I thought the stock 100N+ sounded fine, but when I came back to the 43v there was no doubt that there was more authority in the bass line. I do not feel that there is a problem with the stock 100N+ nor do I feel that the bass in the 43v was out of balance or excessive... "more authority in the bass" accurately captures my impressions of the 43v amp.
The effect on the bass I saw is not "day and night" nor is it subtle in the realm of "differences between wire". I am confident that all of us would notice the difference, but I am not confident that all of us would be willing to pay for the extra iron (this is one extremely heavy amp 
).
I'm not sure what factors led to this observation. The rails are 43v, the PS caps have been doubled vs. stock, the transformers are 625VA (rated at 10.2 amps) and I paid great attention to current carrying capacity during construction (beefy PS diodes, short 12awg leads from PS to amp board, lots of wire and solder surface area on connections that will carry serious current, etc.
With transformers this large and this much capacitance in the power supply, I expected that the amp might sound slow... but I didn't hear that. Maybe others would think it slow, but not to my ears. Perhaps the N+ mods have made it possible to run the amp with larger transformers and higher PS capacitance?
After the above shoot-out, I put the stock 100N+ back in the bedroom system, and then listened to the 43v N+ amp in my main system play Beethoven's 4th symphony (Vanska leading the Minnesota Orchestra, recorded on BIS... a very nice recording by the way)... the music was absolutely lovely. So, the 43v amp will remain in my main system until I get the Orions completed sometime this spring/summer.
Peter
