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Old 20th March 2011, 04:26 AM   #1
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Default HiFi DIY's mini-A kit amp

Greetings everyone,

I am thinking about building the Chinese HiFi DIY company's mini A (25W pc) to replace my ca. 1990 Elektor / Giffard design "medium power AF amplifier" that still works well enough but coupled with newly made pair of SEAS Thor speakers (from the SEAS plans, 25mm MDF) seems a bit lifeless. At least, I'm assuming its the amp: AKSA wrote in this thread

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Originally Posted by AKSA View Post
...Complex, lovely pcb design, LOTS of componenst, fully complementary circuit with a servo LF411.

Sound: High resolution, but rather thin and dry.

Verdict: Most of the DIY amps on this forum offer better sound quality.

Hugh
I was depressed reading that! And I have to agree, the overall sound is probably "thin and dry"! I listen to a lot of classical, and it seems to lack "warmth"....

Any experience with the mini Class A? It's only $300 for what looks like a beautiful kit and might offer a different (better?) sound.

HIFIDIY mini-A power pure final stage amplifier A20 Kit - $299.00 : hifidiy.net

Thanks for any tips!!
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Old 20th March 2011, 04:43 AM   #2
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Quote:
Originally Posted by acebritbiker View Post
...but coupled with newly made pair of SEAS Thor speakers (from the SEAS plans, 25mm MDF) seems a bit lifeless. At least, I'm assuming its the amp:
Don't be so sure that it isn't partly the speakers fault to... as has been shown from the alternate builds done as a result of this thread Clarity on Seas Thor Kit it is clear that the design -- and the testing -- of the original d'Apollita TL was flawed. A lot more can be had out of the drivers.

dave
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Old 20th March 2011, 10:27 AM   #3
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Thanks for the reply Dave. Before building the Thors, I read through many of the very interesting Thor related threads; my feeling was that the main critique of the original (SEAS) design related to "deep bass" and that the various discussions about response etc below a few 100 Hz did not suggest the Thors were useless- just perhaps a bit lacking. Anyway, I am fairly content with the Thor's bass response with chamber music, pipe organs etc. My "wish" is to explore more musical mid to high, which I also believe to be affected by the rest of the system, including my primitive amp, aged source, etc. The Thors are in any event a huge improvement for me from their predecessors (Tannoy). If I do get to want more "bass" I guess a sub woofer is probably one avenue (fat Thors etc being another). Cheers! Tim.
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Old 9th May 2011, 06:25 AM   #4
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Default Hifidiy China Mini Class A20 Experience

I am just finishing the build of this kit. The boards are populated and mounted and I qam running it in to set the bias points. Thus far, everything has gone smoothly, but it wil take some time to populate the boards and figure it out, in my experience. Patience has its own rewards. I cannot speak for the sound of this yet, but this is the fourth or so kit I have built from this seller and not once have I been disappointed. All of their kits represent extremely good value, IMHO. Do not fear the negative and sometimes hostile responses here and in other forums concerning Chinese products. There are some terrific items amongst the chaff that do get sold from China.

Here are my observations about this kit thus far. The circuit boards are of very high quality and the traces that matter are thick and substantial. The other traces are of high quality as well. The components are name brand and of more than adequate quality. The capacitors are Nichicon and Wima and the resistors mostly Dale. There appear to be no off brand "Kung Foo" type parts in ntheir kits. The chassis is heavy and substantial, and the machine work is precision, with everything lining up perfectly. The transformer is beefy and appears to be of good quality with very good wire leads. It is also quite heavy and I have not noticed any hum or noise or overheating, of course. The only substantial criticism I have is that the chassis is small and a little tight inside. It is fine, but I would have liked to see more room. What can you expect for 300 USD, I guess?

My dealings with this company, and also Liang for that matter, have been smooth and pleasant. The woman at Hifidiy is Candy and she is very responsive and helpful. The other kits I have built from them include the CDM-12 transport, the TDA1541A tube dac and some power supplies. If you are resonably skilled with assembly of these sort of kits and your soldering skills are average or better, as well as if you posess reasonable patience to take your time to assemble things cleanly and neatly, you will surely not be disappointed.

Good luck if you pull the trigger and let me know if I can help in any way.
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Old 9th May 2011, 08:29 AM   #5
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GTHICM, Thanks very much for your detailed reply and comments. What you are saying really confirms the "visual" impression of HiFiDiy's kit quality; they do look superb and the prices are very reasonable (much lower than I could source parts for one of the popular class A designs). Plus a decent chassis (even if "tight", the chassis is often half the cost or more and much of the pain). I very nearly ordered the kit when my wife was over in China recently but then didn't, for lack of information mainly. Next time I will. I'd really like to hear your opinion of the sound quality in objective terms -rather than the popular "...deep and broad soundstage, great pacing and airy dynamics, blah blah....!! - that seems to pass for review of audio products. Anyway, looks like you have had fun and success, which is 2/3 of the battle!!

Cheers,

Tim
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Old 11th May 2011, 02:44 PM   #6
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Default Sweet Success!

I took some time this weekend to complete the build of the amp, inspired by questions as to its sound. I took some hours to run the amp in on the bench and adjust the voltages and the bias to ensure the settigs were stable. They absolutely were rock solid and stable on the bench. In order to adjust later, one would have to pull apart the amp, so naturally I was not particularly excited at the prospect of having to do this after fully assembling the amp.

The amp is rated at 25 watts in Class A so I was not expecting much. I have built the amp for part of my horn system with an active crossover yet to arrive, so I decided to just hook it up to my B&W 803Ds. These are not the easiest speakers to drive and they are usually hooked up to some modified ASL Hurricane KT88 push pullls that put out about 200 hundred watts per channel. The B&Ws suffer from some really significant drops in impedance, say from 8 to 3 ohms, so they present a difficult load, especially for tube amps which are arguably not ideally suited for these sort of speakers.

The bottom line is that I am extremely surpirsed, if not downright shocked, at how this little bugger drives the B&Ws. The poor thing should be puking its guts out or clipping badly, but in fact, it is just soldiering on at pretty loud listening levels. It does run hot, as expected, but not ridiculously so. The substantial heat sinks seem to be more than adequate. From the start, dead quiet and in deep bass passages, no hint of stress. The imaging is very wide, and comparable to the Hurricanes, which are noted by some for their wide and deep sounstage. Remarkably, the bass does not seem to roll off and seems quite clean and controlled. In the treble, it might be ever so slightly rolled off, but this may just require a bit more break in. In fact it is improving and is not at all harsh, as I expected it might be with the diamond tweeters.

All in all, a very good showing for a measley 300 bucks, and of course a little blood, sweat and angst during assembly. The assembly is a bit daunting, but attention to detail and patience does reward. I think that anyone would be extremely hard pressed to buy any off the shelf product as good as this for a lot more, perhaps even $1,500. I have absolutely no reservations endorsing this kit. I am certain that with any of the easier to drive speakers, the results would be even better. I do prefer the Hurricanes, but it is not by any huge margin. Go for it, is my advice! You wil not be at all disappointed.

Last edited by GTHICM; 11th May 2011 at 02:48 PM.
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Old 13th May 2011, 10:34 AM   #7
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Great review of this kit, many thanks for taking the time to detail your build experiences and the results with us! Also the infos. about the supplier, which is often an uncertainty in overseas ordering.... Happy listening.
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Old 30th June 2011, 09:18 AM   #8
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Default Trouble ordering

Thanks for the review of the kit, this has prompted me to also order it.

However, I am having trouble ordering from the website йDIY

How did you order yours? Also wondering how much the postage was as well.

Cheers,

Scott.
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Old 30th June 2011, 12:11 PM   #9
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Well its not a mini-A if it puts out 25W per channel, that is full blown aleph territory.
mini-A dissipates 30W for about 10W out.
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Old 30th June 2011, 02:36 PM   #10
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I'm not so sure that class A, as a general class of amplification, is the right way to seek "fatter" sound than as suggested for the Mini-A. I'm familiar with class A in several amp. designs and very happy with it when used with fairly efficient 8 ohm speakers. These amps do not like the now typical 4-6 ohm loads unless they run more pairs of output devices and the current and heatsinking is multiplied accordingly. As sense dictates, the justification of class A is best accuracy, solely by virtue of zero crossover distortion.

As often posted here, sound accuracy or incredible specs seem to have little to do with the sensation of pleasure, listening to recorded music programme. Still, there are plenty of others who are happy just to have the assurance and improvements with accurate, high-spec audio. My experience was to have spent those $300 cheap dollars many times over, only to find that the one $1,500 purchase would have saved the waste and angst over the long learning process.

As you are in range, here in Oz, audition Silicon Chip's 20W class A kit. It's a straight, very high-spec, clean amp. Some would say "therefore it must be boring" but sometimes "reference" is a better way to describe or utilise really clean sound that will embarrass any likely loudspeaker.
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