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Old 27th January 2011, 09:39 AM   #1
engels is offline engels  Israel
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Question Chinese class D TDA8920BTH

Hello everybody,
I'm considering a new hybrid project, a bass amp with tube preamp and class D output stage. As I'm experienced only in tube designs I've thought about buying a class D power amp board and simply putting it in the chassis together with the super-duper preamp I'm going to build.

I've seen several boards on ebay, and this one seems like a proper choise - it's small, the PS is built it, produces 200W into 8Ohm and costs nothing.

TDA8920 Class D Amplifier board/ audio Power AMP 2X100W - eBay (item 110620612550 end time Feb-02-11 23:50:27 PST)

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The ebay description is nice:


TDA8920BTH Philips high efficiency (2X100W) D class digital audio amplifier. IC use HSOP24 power package
With low power consumption and quiescent current. Is the MOS output due to internal control, so has a good sound performance. Deep, powerful bass, and good flexibility. Alto simple and honest warmth, clear bright treble.

When using the BTL bridge, 8-ohm load at 200W power output

Basic performance parameters:
Work: D Class
Quiescent Current: 65mA
Efficiency: 90%
Rated output power: 2 * 100W
Frequency response: 20Hz to 50KHz
Operating voltage: AC12.5V to AC24V
Recommended supply voltage: AC20V-0-AC20V
Maximum output current: 8A
BTL Output:200W 8ohm
PCB board size: (70 86) mm


Now this is a finished board, and I think originally it is being sold as a kit, so the sellers (there are several chinese guys offering this amp) assemble the kit with whatever components they find in a dumpster and sell it to dumb americans. Am I right? Nobody knows.

What I'm asking is:

1 - is there a better power amp for my purpose (200W minimum)? Maybe I'm looking at the wrong place?

2 - If I still buy this thing may I replace bad components with quality parts, or is this board simply a waste of time?

3 - I understand there shuld be a 40 - 50 VCT transformer to power this thing up. What VA rate should it have? How many Amps?
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Old 27th January 2011, 01:24 PM   #2
zog666 is offline zog666  Australia
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I got one of these boards to play with and it was OK.
Not amazing.. but pretty good for the price.
I did a few tweaks on it that improved the sound a little bit.. but one of them (removing the input coupling capacitors) later contributed to my frying it when I shorted a valve pre-amp I was playing with, which zapped it as I dont think the TDA8920 chip liked a blast of DC.

I would buy another one, to maybe use for a simple portable "party" system or similar, as they work, and dont use much electricity.

I used an 160VA 18-18V toroidal transformer to power it.

I'd consider the 200W figure to be pretty optimistic.. It's clean sounding under 30W or so (running in stereo), but distorted above that... so in BTL mode I guess to 60W. Of course if you can tolerate a bit of distortion (instrument rather than hifi use), you might be able to crank it higher.

My experiences documented in this thread:
inexpensive YuanJing TDA8920 board from ebay

And even more detail here:
http://minirig.org.au/2010/07/13/***...-minor-tweaks/

.. later reused the transformer, capacitors and enclosure for a Hifimediy TK2050 amp, which is great, so all OK.
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Last edited by zog666; 27th January 2011 at 01:34 PM. Reason: added extra info
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Old 28th January 2011, 08:30 AM   #3
engels is offline engels  Israel
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Oh, thanks a lot for the link, how come I haven't found it before!
I will probably try the board, but do you have any suggestions for a more powerfull class D output stage? Sort of 150-200W (real watts).
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Old 28th January 2011, 11:32 AM   #4
zog666 is offline zog666  Australia
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Quote:
Originally Posted by engels View Post
Oh, thanks a lot for the link, how come I haven't found it before!
I will probably try the board, but do you have any suggestions for a more powerfull class D output stage? Sort of 150-200W (real watts).
other threads on this forum discuss this amp:

Hifimediy|Hifimediy T3 300W@4ohm Amplifier single

I dont know much about it but have been impressed by the less powerful stereo amp of theirs.

I also have amplifiers from Connex:

Connexelectronic
They have a range of them, some discussed at length on this forum, and Connex have their own vendor forum section on this sitewhere you can ask questions and get support. I really like my Connex TA3020 v3c amp.

All my experience is with audiophile type lower power stereo applications though.
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