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Modding UD-503 Teac
Modding UD-503 Teac
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Old 16th January 2019, 08:02 PM   #1
erikovsky is offline erikovsky
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Join Date: Sep 2015
Default Modding UD-503 Teac

Hello Guys,

I own a Teac UD-503 DAC with heapphone amplifier intergrated.
UD-503 is based on AK4490 per channel, and featuring Teac's unique amplifier circuitry.

However, I don't like its soundstage. So I modded UD-503.
First, bypass cap for Vref is way too small, and according to datasheet, the larger capacitance the smaller THD. I don't understand why Teac uses just 100uF with extra space left.

Therefore, I increase these cap and replace them with Panasonic FM series.

In the amplification section, OPs like muses 8820 and NE5532 are used. I replaced NE5532 with MUSE02 with good result.

As for digital part, I noticed there're 2 SMD XO by NDK, but not the best. I choose NDK2520SDA and they matches perfectly.

Also, there are some 3-terminal IC, transferring 5V to 3.3Vdc. I replace one that is responsible for supplying XO, using LT3042 ultra low noise LDO.

For most digital filtering, Nichicon ultral lowe ESR FP CAP are used, this provide excellent performance for digital part.
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Last edited by erikovsky; 16th January 2019 at 08:04 PM.
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Old 12th March 2020, 02:46 PM   #2
chris0202 is offline chris0202
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Sorry to dig up. However, I looked at mine and noticed there are 2 LDO's inside on the digital board. The one far away against chasis is a 05CC0 from Rohm doing 5V output. This is to avoid confusion...
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Old 13th March 2020, 10:43 AM   #3
invisible force is offline invisible force  Germany
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I am looking forward in thoughtfully replacing some parts in my two very nice UD 503..schematic and service manual will help ..have fun..greetings Philipp
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File Type: zip teac_ud-503_ver.c_sm.pdf.zip (1.99 MB, 14 views)
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Old 13th March 2020, 05:18 PM   #4
chris0202 is offline chris0202
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Quote:
Originally Posted by invisible force View Post
I am looking forward in thoughtfully replacing some parts in my two very nice UD 503..schematic and service manual will help ..have fun..greetings Philipp
Thatís really helpful!

I actually just did a tear down last night and logged the caps location and checked possible alternatives.
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Old 15th March 2020, 01:11 AM   #5
chris0202 is offline chris0202
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Here is mine. I changed all through hole caps. Signal caps are EPCOS 41858 low ESR ones amd Silmic II. Other decoupling caps are either Rubycon ZLJ or EPCOS depending on size that could fit. For opamps, a pair of 1612 replaced 8820, and a pair of 1656 replaced the 5532s on the main board. I didnít touch the 5532s on Line-in board as I donít use those.

A 5V LDO Rohm 05cc0 was replaced with LM340T. I didnít touch SMT ones as I think itís more important to clean the upstream input rather than relying on LDO to reject power noise. The Rohm is okay there. However when I measure prior to modding, input to the 05CC0 is functuating a bit around 10.2-10.3V. So I picked LM340 there.

Initially i was a bit concerned that 1656 wonít work. But it turned out just fine.
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Last edited by chris0202; 15th March 2020 at 01:18 AM.
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Old 1st May 2020, 05:54 PM   #6
tankertop is offline tankertop  United Kingdom
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Location: UK
Quote:
Originally Posted by chris0202 View Post
Here is mine. I changed all through hole caps. Signal caps are EPCOS 41858 low ESR ones amd Silmic II. Other decoupling caps are either Rubycon ZLJ or EPCOS depending on size that could fit. For opamps, a pair of 1612 replaced 8820, and a pair of 1656 replaced the 5532s on the main board. I didnít touch the 5532s on Line-in board as I donít use those.

A 5V LDO Rohm 05cc0 was replaced with LM340T. I didnít touch SMT ones as I think itís more important to clean the upstream input rather than relying on LDO to reject power noise. The Rohm is okay there. However when I measure prior to modding, input to the 05CC0 is functuating a bit around 10.2-10.3V. So I picked LM340 there.

Initially i was a bit concerned that 1656 wonít work. But it turned out just fine.
Interesting. And how would you describe the sound quality after the mods?
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Old 1st May 2020, 10:59 PM   #7
chris0202 is offline chris0202
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Quote:
Originally Posted by tankertop View Post
Interesting. And how would you describe the sound quality after the mods?
Sound quality improves. New opamps are outputing more power and overall better clearity and wider soundstage.

USB board is the biggest surprise. Before the mod I prefer coaxial over usb, after the mod I found USB to outperform coaxial.
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Old 2nd May 2020, 12:10 AM   #8
erikovsky is offline erikovsky
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Join Date: Sep 2015
Quote:
Originally Posted by chris0202 View Post
Sound quality improves. New opamps are outputing more power and overall better clearity and wider soundstage.

USB board is the biggest surprise. Before the mod I prefer coaxial over usb, after the mod I found USB to outperform coaxial.
Why not SOIC-8 to DIP-8 adapter, like my mod?
It provides OP-rolling, really fun!

After SMT pins are soldered, use some silicon glue to reinforce the socket, and swapping OPs would be safe and easy.

Just try it
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Old 2nd May 2020, 12:13 AM   #9
chris0202 is offline chris0202
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Quote:
Originally Posted by erikovsky View Post
Why not SOIC-8 to DIP-8 adapter, like my mod?
It provides OP-rolling, really fun!

After SMT pins are soldered, use some silicon glue to reinforce the socket, and swapping OPs would be safe and easy.

Just try it
Donít really plan to do rolling. I have been doing so on my other amps. Nothing left to try.
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