hifidiy.net A20 mini 20W class A Amplifier

[nippontiger]

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.
HIFIDIYСÐͼ×ÀàA20¹¦·Å×°»ú˵Ã÷(ÕýÔÚ¸üÐÂ, ÓÐÎÊÌâÇë¸úÌù,ÎÒÃÇ»á»ã×Ü) - HIFIDIY ²úÆ·×ÊÁÏרÇø - HIFIDIYÂÛ̳ - 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.

 

[unclejed613]

at 20W, there's no such thing as mini in class A, as you need a very large heat sink....

 

[unclejed613]

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

 

[Telstar]

The heatsinks on the pictures dont seem to small 🙂

 

[nippontiger]

yeah, not sure why they call it "mini" - thing weighs in around 13kg, those heatsinks are about 30x13x5 cms each!

 

[jacco vermeulen]

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)

 

[vinyl dragon]

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.🙂

 

[nippontiger]

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.

 

[HIFIDIY]

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

 

[GTHICM]

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.

 

[Zen Mod]

where we can see exact schmtc , if available on line ?

 

[wahab]

where we can see exact schmtc , if available on line ?

Where "LOW POWER CLASS A" is pronounced, expect Zen Mod
suddenly popping up......

 

[Zen Mod]

(there is always hope to learn something )

 

[bobodioulasso]

ksa 50

 

[Zen Mod]

yup - I know KSA

but - I was interested in that decreased thingy ....... to see how they decrease it

 

[jacco vermeulen]

Vely hot lunning Vas.

 

[wahab]

yup - I know KSA

but - I was interested in that decreased thingy ....... to see how they decrease it

Sure that they first reduce the PS voltage, then adapt
the current sources while regulating the voltage stages
supplies to reduce increased ripples due to quiescent current
inherent to class A biaising..

 

[Zen Mod]

going that route - I can draw one of my own .......

I was just curious in one easy piece , looking at printed schmtc , while drinking coffee ...

 

[wahab]

going that route - I can draw one of my own .......

I was just curious in one easy piece , looking at printed schmtc , while drinking coffee ...

Perhaps that it s a copy from something published in this site..😀

 

[firestorm]

Hi Zen Mod,
did you get round to engineering a KSA-25 ?

Cheers
fs