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.
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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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...
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
That’s really helpful!
I actually just did a tear down last night and logged the caps location and checked possible alternatives.
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 didn’t touch the 5532s on Line-in board as I don’t use those.
A 5V LDO Rohm 05cc0 was replaced with LM340T. I didn’t touch SMT ones as I think it’s 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 won’t work. But it turned out just fine.
A 5V LDO Rohm 05cc0 was replaced with LM340T. I didn’t touch SMT ones as I think it’s 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 won’t work. But it turned out just fine.
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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 🙂
Don’t really plan to do rolling. I have been doing so on my other amps. Nothing left to try.
Recently I purchased TEAC-UD503. And I am using it as pre-amp & headphone amp with external audio clock.
And now I am planning to mod it.
For two usage which are pre-amp & headphone amp, what kinds of mod do you recommend?
For example, so-dip to 8pin dip, caps upgrade, usb parts upgrade etc. Actually I am not an expert to read schematic. So I just want to follow former user's mod guide.
Any comment will be helpful to me. Thank you.
And now I am planning to mod it.
For two usage which are pre-amp & headphone amp, what kinds of mod do you recommend?
For example, so-dip to 8pin dip, caps upgrade, usb parts upgrade etc. Actually I am not an expert to read schematic. So I just want to follow former user's mod guide.
Any comment will be helpful to me. Thank you.
Well if you decide to follow the op in replacing the vref cap, you may want to investigate further than he had.
While it suggested to use a larger value part in that position, you’d be best to ensure that the regulator that serves that circuit is up to the task of handling a lower esr capacitor.
It doesn’t help that a standard part was used, I would’ve found some audio branded part as those typically have lower noise.
Also, consider the potential risk of permanent damage to a device that still has resale value.
While it suggested to use a larger value part in that position, you’d be best to ensure that the regulator that serves that circuit is up to the task of handling a lower esr capacitor.
It doesn’t help that a standard part was used, I would’ve found some audio branded part as those typically have lower noise.
Also, consider the potential risk of permanent damage to a device that still has resale value.