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don't trash your TEAC UD-H01 DAC, pimp it!
don't trash your TEAC UD-H01 DAC, pimp it!
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Old 12th December 2018, 10:08 PM   #1
mige0 is offline mige0  Austria
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Default don't trash your TEAC UD-H01 DAC, pimp it!

This was the first hifi gear I deliberately bought to be modified.

Besides being advertised by lots of sells babble and having award winning specs, it simply sounds awful, especially on the headphone out. Protruding mids, anaemic, clinical and absolutely nothing to fall in love with regarding sound rendering.

But as those can be picked up pretty cheap second hand, which really is no wonder, and as they can almost play each and every digital format and have a nice footprint, I gave it a shot.

TEAC does use crappy Jamicon electrolytics not only as reservoir caps but also for coupling, hence it was a no brainer to replace them. Did use Nichicon FC and Nichicon bipolar ones for coupling. Quite any choice will be better than those Jamicon I guess.

The HP section is built around the NJM 4580. Though not that bad, for cans of lower impedance and at rather elevated levels it runs out of steam. The logical choice for me was to replace it by the OPA1622 which can output roughly 140mA. I also bypassed the relay driven muting circuit as this adds roughly 100 ohm output impedance.

The symmetric line out section is built around the inferior NE5532 which I replaced by OPA2209.


All in all, presentation came greatly to live by above modifications. Love it already.


Things left to be done:
Heat sink for the TENOR chip, as this one runs really hot
Dig up and replace some "hidden" SMD coupling lytics. No schematics available so I have to spend same more time on that.
Attached Images
File Type: jpg almost_stock.JPG (348.1 KB, 601 views)
File Type: jpg Jamicon_reservoir.JPG (314.1 KB, 606 views)
File Type: jpg nichicon_FC_mod.JPG (258.9 KB, 596 views)
File Type: jpg NE5532_stock.JPG (326.8 KB, 589 views)
File Type: jpg OPA2209_mod.JPG (234.7 KB, 579 views)
File Type: jpg HP_mod.JPG (169.2 KB, 250 views)
File Type: jpg TENOR_chip.JPG (368.7 KB, 237 views)

Last edited by mige0; 13th December 2018 at 02:56 AM.
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Old 13th December 2018, 12:48 PM   #2
mige0 is offline mige0  Austria
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Lots of fun, feeding an external headphone amp
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File Type: jpg TEAC_UD-H01_mod.JPG (269.7 KB, 224 views)
File Type: jpg TEAC_UD-H01_mod_2.JPG (286.4 KB, 203 views)
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Old 13th December 2018, 12:58 PM   #3
mige0 is offline mige0  Austria
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garbage
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Old 13th December 2018, 01:16 PM   #4
weissi is offline weissi  Austria
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Why did you leave the I/V opamp (NJM Muse). I'd rather replace that for a high speed opamp like an OPA2156/THS4032/ADAU4898 and leave those NE5532 in.
You could also try to lower the Iref resistor from the PCM1795s to around 6k (designated R300 and R200).

Why didn't you buy caps that fit? (kleiner Scherz...)
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Old 13th December 2018, 02:27 PM   #5
mige0 is offline mige0  Austria
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Quote:
Originally Posted by weissi View Post
Why did you leave the I/V opamp (NJM Muse).
Has anyone ever had experience with MUSE opamps?




Quote:
Originally Posted by weissi View Post
and leave those NE5532 in.
No way I ever will warm up with NE5532


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Originally Posted by weissi View Post
You could also try to lower the Iref resistor from the PCM1795s to around 6k (designated R300 and R200).
Don't even have a clue what stock Iref resistor is in there. No schematics available


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Originally Posted by weissi View Post
Why didn't you buy caps that fit? (kleiner Scherz...)

Last edited by mige0; 13th December 2018 at 02:31 PM.
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Old 14th December 2018, 10:39 PM   #6
mige0 is offline mige0  Austria
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Heat sinks for the TENOR and the regulators
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File Type: jpg heat_sink_mod_2.JPG (264.4 KB, 130 views)
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Old 14th December 2018, 11:04 PM   #7
mige0 is offline mige0  Austria
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Will try to substitute the headphone board with a OPA1620 EVAL board that is said to arrive around Christmas. Less guesswork for modding, as no schematics from TEAC available.

Occasionally the OPA1622 at the plug in adapter board gets into distortion mode with my 60ohm cans, some oscillation I guess.
Was not able to trace it down because it worked ok as soon as I hooked up my oscilloscope.

Last edited by mige0; 14th December 2018 at 11:30 PM.
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Old 15th December 2018, 10:36 AM   #8
weissi is offline weissi  Austria
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Try a TPA6120, you'll get those boards very cheap and trust me, for driving headphones whatever kind this is the chip to beat. Needs a little mod to get it working in balanced mode. I use it with Fostex T50RP and AKG K702, simply great.
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Old 15th December 2018, 12:59 PM   #9
mige0 is offline mige0  Austria
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There are two drawbacks for the TPA6120 compared to the OPA1622 / INA1620 as I can tell from data sheets.
First the PSRR of the TPA6120 is around 80dB at best whereas the OPA1622 / INA1620 comes with stellar 140dB and second the TPA6120 is not stable on headphones without an output resistor.
Especially the second disadvantage definitely keeps me from trying, but thanks for your recommendation anyway.

There is an elegant way to further improve upon stability for the OPA1622 / INA1620 I have stumbled across lately:
http://www.ti.com/lit/an/slyt630/slyt630.pdf
Don't think this would also work for a current feedback opamp like the TPA6120
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Old 15th December 2018, 03:40 PM   #10
weissi is offline weissi  Austria
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Well, having some resistors at the output isn't such a bad thing, it is also there to avoid short circuits that happen with those TRS connectors.

On the other side, the INA1620 that you've mentioned looks indeed very interesting, I might have to order the EVM too.
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Last edited by weissi; 15th December 2018 at 03:49 PM.
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