Project....Modding an Ebay TK2050 board - diyAudio
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Old 1st June 2014, 05:36 AM   #1
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Default Project....Modding an Ebay TK2050 board

I built a 41Hz amp4 a while back, and like the sound quite a bit. So much so that I don't mind getting another TK2050 based amp. But the 41hz build was a bit confusing (small parts; some part # don't follow any order; the board has power supply section built-in which I don't use/need, etc). Now 41Hz support site is down, without knowing when it will come back on, I am not sure if I want to do another amp4 anytime soon.

About a weeks ago I was browsing ebay and noticed that there are quite a few 2050 based boards. One of them piqued my interest, the layout seems to be very straight forward with common sense (which is a good sign, suggesting they probably did manual routing instead of auto-route) , components are minimalistic (which is good since I will replace a lot of them anyway), the whole arrangement/ parts spacing also seems quite promising for easy modification.

So I bit the bullet and bought one from this listing. I suppose $25 is a no-brainier for a fully built TK2050 board. (for that kind of $ I can't even get another amp4 parts kit).

** I don't know if my case is typical or not, but the seller shipped my order at lighting speed, I did the "buy it now" around 4PM and by 6:30pm I got an e-mail with a tracking # indicating the board was shipped. According to the tracking system it should show up in my mail box within the next couple of days, which will make the total ship time around 10 days, to the US.

Since I have done Tripath based stuff before, I will go straight to the good stuff, here are the planned mods:

-- Replace input caps with good quality film caps. Judging from the auction photo, the stock caps are electrolytic's.
-- replace bias-cap (the 0.1uf that goes to the ground, yes I know there must be one, it is on the TK2050 spec sheet) with good quality film cap.
-- Replace output inductors with toroidal air coils.
-- Replace output filter caps with good quality polyprop caps.
-- Do a linearly regulated 22V power supply to power the board. ( 20V so it is safe to drive both 4 ohm and 8 ohm speakers. ). I will use 4x 7812, float the reference/ground pin to 8V using a 4-LED string, that should provide the 20V/4A I need.
-- Maybe add a volume control, if so it will be a shunt type with an Alps pot and AudioNote resistors.

Stay tuned, if you are interested in doing a similar project.

Last edited by audiocats; 1st June 2014 at 05:54 PM. Reason: fixed link
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Old 1st June 2014, 03:56 PM   #2
Bare is offline Bare  Canada
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IMO :-) The Best mod possible would be to source a proven Genuine Tripath chip and fit it.
Good luck with that tho
Then proceed to replace ALL the other rubbish quality parts.
For $20.. likely even the solder was recycled rubbish

Last edited by Bare; 1st June 2014 at 03:58 PM.
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Old 1st June 2014, 05:46 PM   #3
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hehehe, the price does seem awfully low, we just have to wait and see how bad/good the board turn out to be.

On the other hand, most of the cost on a class-D board is from the support components, and judging from the auction photo most components on that board look cheap (which is a good thing since I will replace a lot of them). Maybe that is why they can sell it at such a low $.

By the way, is there that many fake tripath chips out there? they aren't that expensive to begin with and I don't think the production has ever stopped even after Tripath went under as a company? I can see somebody repackaging the (less expensive) TA2021/2024 into DIP package, in a small factory using relatively simple machinery, and sell it as TA2020 (which usually demand a little more $); I don't see how one can easily fake a functional TK2050, it is a SMD chip set, and there isn't any lower priced chip set that one can use for repackaging. It is no garage-level work to fake a functional SMD chip (and this board is supposedly fully done and ready to use)....

We will find out soon enough, hopefully it will arrive tomorrow. Click the image to open in full size.
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Old 3rd June 2014, 05:02 AM   #4
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got the board in mail.

the good:
-- shipping was fast enough, 10 day to the US.
-- solder joints look good, the through-hole joints are good, the SMD soldering is really good, shiny and clean. No excessive flux residue. Definitely no "recycled solder". Much better soldering than what I see on my Muse TDA1543 Dac.

the bad:
-- packaging was just a padded envelope.....
-- board was wrapped in plain clear bubble wrap (then stuffed into the envelope). no ESD bag, not even the more ESD safe pink bubble wrap. I suppose the humidity in southern china is always pretty high so ESD is probably not a concern for them, but they should still have used some ESD packaging material to make sure bad things don't happen during the shipping. Even if the board works ok for now, there is no way to tell whether there is hidden damage caused by some low power ESD discharge which can still cause latent component failures.
-- heatsink is silicon glued to the chip. There are holes in the heatsink and in the board to accommodate two screws, but they opt'ed to just use silicon....

Will do a functionality test tomorrow before I start pulling parts off.

Last edited by audiocats; 3rd June 2014 at 05:06 AM.
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Old 4th June 2014, 12:58 AM   #5
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update:
hooked up the board and it works, sound is clean without distortion.

The control chip has Tripath logo; The output stage chip is marked DDX.

The overall board gain is 30X. Gain resistors are easy to identify, at a convenient location (if I end up wanting to chang them).

Bias cap easily identifiable as well.

Will post pictures later, if my photobucket account still works.
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Old 4th June 2014, 04:13 PM   #6
Bare is offline Bare  Canada
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Hey! a good start then.
Quality (sounds ) can vary ..Dramatically.. between examples.
Hopefully you received one of the better ones?

Don't be fooled Tripath ceased ALL production ~8 years ago.
Unlikely that's a genuine chip, as there are copies of copies of copies being Fabrique en Chine.
Easiest identifiers, beyond substandard sounds and sudden death:
Logo is laser etched and Korea is on the logo , no gold pins)
Tricky though as the Rascals are becoming surprisingly adept at cosmetics.. yet ignoring all else
Genuine Tripath chips Were V good sounding.. the reputation was well earned.

Last edited by Bare; 4th June 2014 at 04:16 PM.
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Old 5th June 2014, 05:14 AM   #7
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the tip of screw driver is pointing to the gain resistor groups for the analog stage(two groups, each has one 20K (203) and one 47K (47k)) . This will give 47k/20k=2.3x gain for the analog stage.
The digital stage gain is the default 15x, I am not gonna change that.
To reduce gain, change the 47K to 20K (or parallel another resistor on top of the 47K).

Click the image to open in full size.
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Old 5th June 2014, 05:17 AM   #8
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Tip of the screw driver is pointing to the bias-cap capacitor. ( I marked it in red).

Click the image to open in full size.
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Old 5th June 2014, 05:18 AM   #9
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After taking off the parts I want to replace, the board looks pretty barren.

Click the image to open in full size.
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Old 5th June 2014, 05:22 AM   #10
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the 5V line on the board is generated by a surface mount 7805. Nothing wrong with that. Except the reservoir at the output of 7805 is just a pair of ceramic caps, the uF value can not be very high. I added a 100uf tantalum cap to it. Might change to fancier cap later. (say, a BGNX).Click the image to open in full size.
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