High-End Regulated Buffered Inverted GC

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:devilr: 😀
 

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So I did some listening today (after 14 hrs of breaking in the new amp). The new amp is built exactly to Carlos schematic. I used 338 regulators and 33u Nichicon Gold Tune caps at the chip. At the bridges there are 4.700u Nichcon Gold Tune and 1,500 Panasaonic FC right before regulators, inverting topology with 220 Caddock and 10k Rikens, 4.7 BG N for coupling. OPA627 is powered by 78/79 15V regulators. PS to the amp is 29V with 5V drop on regulators.

The other amp is Patek, powere by 4 x 12 V Panasonic 7.2Ah cells providing shared 2 x 24V supply. The PS caps are 1000/50 BG N type and the amp is NI with Caddock, Riken and Vishay resistors.

The transport used was CD Pro with TDA1543 outboard DAC. Preamp is ML380S.
 

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I first listened to Patek to get some initial impressions and a base for comparisons. The material consisted of variety of styles: from jazz, country, classical, contemporary to techno and industrial. I was particularly interested in hearing the bass performance.

On a first listen, the new amp (I will not call it Carlos amp as it's built by me, but based on his recommendation) sounded surprisingly good, with nicely defined highs and midrange. The sound was clean and convincing.

On more closer evaluation, I noticed that the bass is actually worse that what I'm getting with battery powered Patek. A good track to test the bass performance is Track No10 on Burmeister CD 3 Sampler. It is Yim Hok-Man, Master of Chinese percusion: 'Poem of Chinese Drums", Bestell-Nr 8.2259942.

The bass with new amp was rather "rounded", lacking dynamics and the 'punch', kinda lean and flat. The accustic space between drum beats was missing, as well as fine resonances. On a bad system, this track sounds rather boring and uninvolving. In a good system, you actually notice when the drums begin to "talk" with each other and sort of exchange starts. This gets you involved and you want to hear what comes next. With an average system, you simply switch it off, as it's too monotonous. With the new amp, I wasn't really interested what comes next.

Another area of my complain is the missing of fine detail and resolution. The new amp simply does not provide the accoustc space between notes. It's almost like you listen with DNR system that cuts off all the "inner voices" (I got this description from Elso). It does not seem as alive, as I know it can be. The guitar strings seem to not resonate enough and the feeling of being there is gone. I did not notice any improvement in soundstage and actually I think it got more narrow.

On more complicated passages, like track 4 from Front 242 Re:Boot album, the amp couldn't keep up with the main bass line and the whole composition fell apart. Again, the bass was not that deep, as I'm used to and the pace and rhythm was missing, or at least was not as good as I'm used to.

In closing, Carlos amp is pretty good, but it is not very good. There are some areas that can be definitely improved. I don't know how much it is due to the design choices here: is it the inverted topology to blame, or is it OPA627 buffer, is it regulators for input buffer, or the coupling cap. I truly didn't observe any improvement with regulators on LM3875 chip (comparing to battery power), but actually the performance was rather inferior. I know that Nichicon caps are not the best out there and maybe with better types the sound could improve.

I did not compare this amp to a regular, minimized GC, but will do it soon. They feature the same chassis, so comparing will be rather accurate.
 
Peter, I don't recognize any of your impressions of this amp.
Or there's something wrong, or let it :hot: -in for at least a week.
You can listen meanwhile, but let it play.
Anyway, I was amazed comparing with my unregulated amp (the only difference was the PSU) on the first power-on.
But it did improve over the time, It was :hot: -in for 3 weeks.
 
I must say that in those amps everyhting counts if you really want to push the envelope. Even such thing as transformers. We recently got some samples from China, 300VA toroids that actually look like 400VA and seem to be very well built. They look like older production Plitrons. Since we could get them at less than 50% of Plitron cost, they seemed very appealing.

I've built two amps, exactly the same, the only difference was the transformers: one was from China, the other Plitron. Although initially they both sounded OK, on closer examination we noticed that Plitron produced much better bass, pace and was also more detailed. Sort of the difference when comparing BG and Panasonics. The Chinese TX were smoother, but somehow lacking "definition". We decided not to use them, even in the budget line.
 
What speakers are you driving

One limit to mass generalization of any of the results (GC classic, regulated, battery etc) is that there are as yet only a few data points for some of the approaches. It is quite possible and quite likely that "which one is best to the listener" will vary with speakers, volumes and personal preferences.


Peter,

What speakers were you using to test with and what are the speaker attributes as to the type of load they represent?
 
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