hifidiy.net A20 mini 20W class A Amplifier - diyAudio
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Old 16th June 2010, 12:41 PM   #1
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Question hifidiy.net A20 mini 20W class A Amplifier

I found an amplifier kit from Hifidiy.net - a Chinese company supplying DIY audio kits.
HIFIDIY mini-A power amplifier A20 Assembly Instructions
Basically, its a 20W class A amplifier. The kit comes complete with PCBs, components, what looks to be a 200 VA toroidal transformer, 40,000uF in the PSU, heatsinks and a nice, shiny case.
Im living in Japan at the minute and because of the strong yen, this kit would cost very little. (less than 200 pounds in real terms)
I was wondering a few things:
Has anybody built this kit?
Has anybody any experience with hifidiy.net kits in general?
Unfortunately, I cant find a circuit schematic, but does this look like a decent amp for a beginner to build?
Also, Im a bit worried about the lack of proper English instructions - I dont think I'd have to much trouble populating the PCBs and wiring it up, but in the assembly instructions (looks like they used google translator!) theres a section describing what looks like amplifier set up - perhaps setting the bias? The English translation doesnt make any sense! There seems to be more pictures on the Chinese assembly instructions.
HIFIDIY小型甲类A20功放装机说明(正在更新, 有问题请跟贴,我们会汇总) - HIFIDIY 产品资料专区 - HIFIDIY论坛 - Powered by Discuz!
I have some Chinese friends who could, perhaps, help me with the Chinese, although they know nothing about electronics.
The other thing I was wondering, I believe the trans is set for either 115 or 230 V operation - this would suit me as Id need it in 115 V for Japan and 230 for when I move back to UK - would it be just a case of rewiring a couple of leads on the transformer to make the change?
Thanks.
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Old 16th June 2010, 01:23 PM   #2
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at 20W, there's no such thing as mini in class A, as you need a very large heat sink....
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Old 16th June 2010, 01:31 PM   #3
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at 20W, there's no such thing as mini in class A, as you need a very large heat sink.... note to self, avoid the use of the BACK button
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Old 16th June 2010, 01:33 PM   #4
Telstar is offline Telstar  Italy
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The heatsinks on the pictures dont seem to small
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Old 16th June 2010, 01:41 PM   #5
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yeah, not sure why they call it "mini" - thing weighs in around 13kg, those heatsinks are about 30x13x5 cms each!
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Old 16th June 2010, 03:06 PM   #6
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Quote:
Originally Posted by nippontiger View Post
I cant find a circuit schematic, but does this look like a decent amp for a beginner to build?
It's a downsized Krell KSA50.
MJL3102/3281 outputs, MJE15030/31 drivers, 2SD669 Vbe device, MPSA+MJE Vas devices, A970/C2240 input transistors (some even use MPSA42/92)
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Old 16th June 2010, 09:15 PM   #7
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For 200 it looks like a bargain and given the difficulty in translation etc will also provide a lot of entertainment.
Don't really see that you can go wrong.
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Old 17th June 2010, 12:49 AM   #8
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I might give it a go! Seems like the most difficult part might be working out how to pay using Yen - Japanese banks are absolutely awful and its difficult to get a credit card here as a foreigner!
If I manage to get the kit, I will post my experiences.
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Old 10th October 2010, 08:31 AM   #9
HIFIDIY is offline HIFIDIY  China
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Yes, it is a chass A amplifier, the specification is like this :
Frequency response(HZ) :5-100K
Output power (watts) : 25(Class A)/100 (Class AB)
Total harmonic distortion: 0.01%
Size( W*H*D) (CM): 25*13*32
The Net weight (Kg) : 13kg
more information can check on http://mall.hifidiy.net
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Old 10th October 2010, 10:23 AM   #10
GTHICM is offline GTHICM  United States
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Default Recommend This Vendor and Products

For what it is worth, I have built several of their kits, including a cd transport and TDA1541A dac. The boards and parts are all of top quality and the caswork is very nice as well. A little time is necessary to figure out the instructions, but this has become much easier than several years ago when I built the cd transport kit, which was fun to build and works very well to this day. There is a lot of value for money here so you need not hesitate on account of any concerns like that. I trust that you would not be disappointed if you decide to pull the trigger.
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