The author is making a test and a modification according to the test result. First, the author is showing what device he is using as we can see.
1：Digital output：EMU0404
2：DAC and Pre-amp ：MINI USB DAC MKII
3：Power amp：DENON AVR48
4：Speakers：DIY 5 inch using SEAS H1216 and VIFA XT25 30-04 units.

The components changed can be seen in the pics.
2# is about the result of changing some capacitors. It’s so complicated. I don’t even know how to translate it. Let me try my best. The original Nichicon MUSE 16V/100uF capacitors are replaced by some Nippon chemi-con solid aluminum electrolytic capacitors as we can see in the pics.
The change in sound is that it feels more real when listening to some violin and piano pieces, better texture.

Then is the 3#. The author uses a Rubycon Blackgate and it’s very good. The reverb on the instruments clearly enriched - and almost the whole band.
The best compounding here is the Blackgate plus the NCC PS capacitors.
The Elna SILMIC doesn’t perform well in the filter part. Combination of the filter capacitor is replaced by Rubycon ZL + ZLH.

And the last part of 3#, the author tested the Panasonic FC 220uF/25V replacing the Rubycon ZLH beside LM1875. The bass is good, but the high-frequency is not very good.

The Rubycon MCZ(two 1800uF/16V in the picture) replacing 4 1000uF/16V ZLH to be the filter capacitor performs well in high-frequency, and the Blackgate’s bass is good. So they arrange in groups well.

The 4# is about the test of OPAMPs. The original OPA2134 has a better definition than NE5532. But NE5532 has its special taste. Two NE5534s are similar to one NE5532.
Then the author tried the LM833N. The amount of bass is just right. If you like listening to drums it’s a very good choice. Its sound is the most real in the OPAMPs the author has tested. The OPA2134 is better than LM833N in weak sound and resolution. But LM833N is much cheaper and performs well.

5# is the test of changing the single PSU to dual. The single PSU uses an LM317, the main filter capacitor is 3300uF, the voltage is 30V DC. The dual also has 3300uF capacitor as main filter, uses one LM317 and one LM337, the voltage is +-15V DC. The result is, the single PSU is better in bass because the transformer it’s using has bigger power(26*3.4VA).

That's all, my translation is incondite, hope you can understand as much as possible. I see the picture of your MUD, the 105 capacitor is a red WIMA? I tried a 1uF WIMA there, it's not very good, the high-frequency is a bit too sharp and the bass is weak. The Evox is more balanced.

For some reason when I try to listen to my iPod via RCA line-in it doesn't work. I already had to send in one defective unit once because of the headphone input. My old AUNE did not have this problem.

I have a hunch there is SOMETHING wrong with the headphone amp portion of this unit. When I listen to it straight from my computer, the DAC portion works fine, and when I switch it to the headphone amp setting, the sound sounds identical. Is this supposed to happen?

Also is the unlock button supposed to be on 24/7?

When you want to listen to it via RCA line-in, then you should switch it to A. When it is switched to D, it just outputs the signal from the dac part.
When you use the digital input through coax, switch it to S/PDIF and if the signal is locked, the unlock LED will be off.

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I have deduced what the problem is with a little help from Jeffery over at coolfungadget.

It seems there is something wrong with the A-D switch. Whenever I try to change the setting from D-A nothing happens. The DAC function of the AUNE works just fine, meaning that the switch will not let me change it to A, which in turn won't let me listen to my iPod. It makes sense. Does anyone know how to fix this switch? It seems like a real bummer to pay 40 bucks to ship it back for another replacement when I have a pretty good idea what the problem is.

Hi guys,

The Aune caught my eye today.

Can anyone comment as to the robustness on this dac/amp? I've seen a few posts in this thread with people having some trouble with it. Is there much/any noise over USB in?

Cheers,
JackyD

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The rca output on the back is hardwired to the lpf filter/dac meaning no matter what switches you use, the connector always outputs the the usb/spdif source. The a/d switch decides what source the headphone amp part should use, D uses the dac as source while A uses the rca input at the back. I'm using it with a little chinese tube buffer, i connect the out to its in, and its out back to the aune. A/D switch is in the A position. Switching is done by the rectangular component near the leds, this takes the signal from the A/D switch. To check your A/D switch: in one position it should short its middle pin and the left or right pin, and in the other position the middle pin and the opposite.

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Thanks alot for the info, it was a nice read. I think i won't touch/replace the electrolytics for now, but i think they used those 100uf/16v nichicon caps way to generally... i'll replace some with 2.2uF film caps, and add 0.1uF ceramics directly between the power legs and ground of active components on the backside of the panel (if i can get some that fits). As i see the problem: electrolytics usually act act as "energy storage", or a buffer to reduce ripple, while film caps act as noise filter and ceramic caps for high frequency noise filter. For power supply, i'm thinking about getting this one. Add an enclosure and a transformer and it's finished basically.
About power supply voltages... is it safe to use it with +-15V at all? Electrolytics over the place are 16V types, and the lm7808 voltage regulator has no heatsink attached to it, it might overheat. The voltage regulator is my main concern, if i should use +-12V or +-9V.
Yep the 105 cap is a red wima 1uF. I'll try to get 1-2,2uF evox there, but it will be a hard mission, it's hard to get brand parts where i live.

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I haven't noticed any noise over usb, or spdif for that matter. The signal path has no capacitors if you use the dac as the source, for the headphone part, and i'm getting weird dc offset out of the phone jack. I personally wouldn't use the volume pot over 1 or 2 o'clock, it could potentionally damage your headphones. If the unit is powered on and you have headphones plugged in with the volume pot maxed, it would probably kill the phones overnight or maybe even faster(100mV is a lot), without any listening of course. It might be that somethings is weird with my unit but i doubt that. I checked the original graham slee solo design, and that has dc blocking caps on its input.

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I'm using a +-12V PSU, but its power has got only 7VA, a bit too small for the DAC I think. +-9V is also OK and safer I think. The 105 cap can also be replaced by other brand's, not just evox. You can try some bigger ones, the bass may be improved.

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I gonna get a transformer with 10+ VA per output rail, so that wont be a problem i guess. Well, since the puwer supply i linked is adjustable, ill just use it +-12V and check the regulators temperature. About that cap... just how much bigger? 15mm or 17,5mm lead spacing is the max there i guess...

Maybe you can try some caps bigger in capacity. I once compared a 1uF WIMA and a 10uF Evox. The difference is very obvious. But the difference between a 10uF Evox and a 22uF Evox is not that large, I can't even tell apart them.

Eugene I see you upgraded the power supply in your unit too. What are you using?

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I'm using a PSU kit using 7812&7912. A simple DIY kit, you can see in the picture.