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E1DA 9038D Review (portable DAC & Amp)

Veri

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BTW: Somehow I can't understand the purpose of balanced headphones, given the limited cable length.
If you drive a tough load like the Aeons, balanced cables for portable gear can definitely help with the additional power..
 

respice finem

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How can a headphone cable influence power? A real question, I'm driving the de facto 1kOhm Beyerdynamic T1 Mk2 unbalanced (RME ADI2-DAC), no power problems at all.
 

jannek

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How can a headphone cable influence power? A real question, I'm driving the de facto 1kOhm Beyerdynamic T1 Mk2 unbalanced (RME ADI2-DAC), no power problems at all.

As far as I understood it: In a balanced (correct: differential) mode you don't have music signal vs. common ground but signal vs. inverted signal. This in fact doubles voltage (and improves channel separation).
The point is not the cable but balanced amplification.
 

respice finem

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For this to work, you need the wiring of your headphones also to be balanced, or am I sitting on my brain?
 

Jimbob54

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Yes to use a balanced cable your headphones need to have a compatible wiring :p some need to be modded for that.

@respice finem Dead easy for the T1.2- detachable 3.5mm dual cables at the cups- plenty of aftermarket cables can be had for about $50-100 terminating in whatever you like at the amp end. I would suggest pointless in your case as, like you say, the RME can drive them no problem. But on a weaker amp that has balanced and single ended, if the SE isnt enough, the balanced might be.
 

capslock

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Amir, as I see your setup has too high common-mode noise or AP analyzer has a problem with its CMRR. I took a look at the result here https://www.audiosciencereview.com/forum/index.php?threads/hidizs-s9-review-headphone-adapter.21152/
The balanced is a lot less noisy vs unbalanced, that's why my balanced 9038S looks so clean vs unbalanced 9038D. You can check that by shorting one of 9038D outputs(of course better if no signal on that channel), I bet you'll find the same dirt on the shorted output as well as on the working one. To avoid that noise you can try to use Android phone in airplane mode and battery-powered with a free Hiby hires player.
My measurement was performed in different ways and always I see the same result +/- a little bit. Regarding Dynamic Range, APx555 has 8x times more noisy inputs vs my custom preamp, hence it is fine if your result up to 1db worse(i.e. 124db(A)) but not 6db of course. The same about THD+N my SYS2522 shows me -117db, SYS2522+external ultra-high performance notch filter(the current 3rd version of that filter has -126db limit for THD+N) 9038D has THD+N -118.3db(-.2-.5dbfs, no-load condition, 20-22000Hz BW 0.00012%). Also, my new project Cosmos ADC(SNR -127db(A) in the mono mode) also shows me THD+N -118db. All my analog processing instruments(120nVrms(A) preamp and notch filter)are well-matched with their preliminary simulation and school physics too(I did test thermal noise of resistors to confirm the noise level resolution).
PS: I want to show how Cosmos ADC sees the signal of 9038D 12kHz@48kHz. No AVG at all. The FFT shows jitter of Cosmos+9038D.
View attachment 119260
Can you tell more about your COSMOS ADC? What ADC chip does it use?
 

capslock

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Not quite. The 9038S's headphone Amp cannot be bypassed and using it with external Amps is not recommended. Without the GND pins of a proper, balanced standalone DAC, the resulting GND potential can destroy the 9038S.
Unless you know what you're doing, please use the 9038S only with passive equipment.

So what is the concern? That the V- outputs would get shorted to ground, especially if the USB and the amp are not galvanically isolated?

Or is it the missing ground connection? The 2.5 mm TRRS connector has no ground. Will that cause problems with an AMP that has balanced in? I suspect if all four inputs are terminated to amplifier ground with a reasonably low resistor, say 4k7, it shouldn't be.

Then, why the distinction between TRRS connectors with a 5 mm shaft stopper and barrel and why would it make a difference only for the PDv2? I looked at about 30 different offerings in Europe, non had a shaft stopper, but many had a slim housing rather than full barrel.

Lastly, what is the Susumu edition of the 9038SG3? There does not seem to be a standard edition any longer, just Susumu 2000 and 3000, the difference appearing to be an extra 1000 µF for about $5.
 

staticV3

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So what is the concern? That the V- outputs would get shorted to ground, especially if the USB and the amp are not galvanically isolated?

Or is it the missing ground connection? The 2.5 mm TRRS connector has no ground. Will that cause problems with an AMP that has balanced in? I suspect if all four inputs are terminated to amplifier ground with a reasonably low resistor, say 4k7, it shouldn't be.

Then, why the distinction between TRRS connectors with a 5 mm shaft stopper and barrel and why would it make a difference only for the PDv2? I looked at about 30 different offerings in Europe, non had a shaft stopper, but many had a slim housing rather than full barrel.

Lastly, what is the Susumu edition of the 9038SG3? There does not seem to be a standard edition any longer, just Susumu 2000 and 3000, the difference appearing to be an extra 1000 µF for about $5.
Here's why you need a shaft-stopper for the PDV2, but not for the 9038S:
Screenshot_20210321-155013_Keep Notes.jpg
Screenshot_20210321-155249_Keep Notes.jpg
Screenshot_20210321-155704_Keep Notes.jpg
Screenshot_20210321-155518_Keep Notes.jpg
The PDV2's 2.5mm jack is slightly recessed into the housing.
While some plugs without that stopper have been reported to work fine, I still recommend you get one with.

9038SG3: Yageo resistors and 2mF power filtering caps
9038SG3 Susumu 2000: Susumu resistors and 2mF power filtering caps
9038SG3 Susumu 3000: Susumu resistors and 3mF power filtering caps

Switching to Susumu resistors improved the unit to unit variance.

Edit: all 9038D units use Susumu resistors and 4mF power filtering caps
 
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capslock

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Thanks, very clear on the connector. I initially thought the Susumu were about the power filter, but I assume they are about gain matching?

So what is the concern about connecting an amp? I take it connecting a balanced input will not be a problem unless the common mode differential is huge?
 

staticV3

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Thanks, very clear on the connector. I initially thought the Susumu were about the power filter, but I assume they are about gain matching?

So what is the concern about connecting an amp? I take it connecting a balanced input will not be a problem unless the common mode differential is huge?
I don't know the specifics, only that some 9038S units have been destroyed after customers used 2.5mm to 2x 3pin XLR adapters to plug the DAC into a balanced, mains-powered Amp.
If that 3rd ground pin wasn't necessary for safe operation, then DAC and Amp manufacturers would instead use a single 4pin XLR port or two RCA ports for their balanced DAC output/balanced Amp input.
Maybe @IVX can tell you more about it.
 
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capslock

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I don't know the specifics, only that some 9038S units have been destroyed after customers used 2.5mm to 2x 3pin XLR adapters to plug the DAC into a balanced, mains-powered Amp.
If that 3rd ground pin wasn't necessary for safe operation, then DAC and Amp manufacturers would instead use a single 4pin XLR port or two RCA ports for their balanced DAC output/balanced Amp input.
Maybe @IVX can tell you more about it.

Interesting. Since the 4-pole TRRS does not have a ground connection, the pin 1 ground of the XLR never was connected to the DAC. Or would the adapter short the sleeve to ground? I would imagine the headphone out is protected against shorts as you can have them with TRS, too, if it only half way plugged.

So was this too high a common mode voltage overloading the protection diodes of the headphone amps? In that case, putting a 30 or 50 R resistor in series with each output right on the connectors of the 2.5 mm TRRS plug should make things safe. One could also try to connect the screen of the cable to the ground of the USB connector.
 

staticV3

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Connecting Pin 1 of the XLR plugs to the GND of the USB cable that's plugged into the 9038S is the way some people on our Discord are using the DAC with an external Amp.
 

DivineCurrent

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The 9038D G3 works really well with my IEMs. No hiss at all, and I love you can adjust maximum volume output and put it in IEM mode to prevent accidental volume jumps. I will say the unit gets very warm, sometimes even hot depending on the length of use and what music I'm playing. It gets very warm with my 16 ohm JVC HA-FDX1. My 9038S does not even get warm at all, maybe it doesn't need to work as hard in balanced mode as the unbalanced 9038D?
 

Veri

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IEM = In Ear, what is M?
Monitor. Good IEMs used to be reserved for professional stage use and professional musicians. Nowadays you can get good/affordable ones for home and casual listening.
 

IVX

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Ok, guys it seems I've found the reason for always worse Amir's tests for unbalanced DACs and better for balanced. The problem is Amir uses unbalanced APx555 inputs for unbalanced DACs. Only balanced inputs of APx555 have good enough CMRR to measure DACs or amps whatever, and actually, no reason at all to use unbalanced inputs ever(just forget about them) - only balanced XLRs.
Dear amirm, Unbalanced BNC inputs tied to the APx555 chassis and could not be used for non-isolated sources like AC-line powered PC, if you like to use that BNCs for any unknown reason(because any even 30 years old AP has excellent balanced XLRs), please use it with battery-powered sources. Balanced XLRs inputs are referenced to each other but not to the chassis intentionally to let you measure precisely sources with strong common-mode noise(XLR+/XLR-/GND-chassis-AP to GND of your PC, for instance, to USB-C shield). I can't and I don't push you to remeasure my DAC but for the future of the audioSCIENCEreview.com better if you'll correct your setup.

2021-03-22_19-55-16.jpg
 

DeepSpace57

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Ok, guys it seems I've found the reason for always worse Amir's tests for unbalanced DACs and better for balanced. The problem is Amir uses unbalanced APx555 inputs for unbalanced DACs. Only balanced inputs of APx555 have good enough CMRR to measure DACs or amps whatever, and actually, no reason at all to use unbalanced inputs ever(just forget about them) - only balanced XLRs.
Dear amirm, Unbalanced BNC inputs tied to the APx555 chassis and could not be used for non-isolated sources like AC-line powered PC, if you like to use that BNCs for any unknown reason(because any even 30 years old AP has excellent balanced XLRs), please use it with battery-powered sources. Balanced XLRs inputs are referenced to each other but not to the chassis intentionally to let you measure precisely sources with strong common-mode noise(XLR+/XLR-/GND-chassis-AP to GND of your PC, for instance, to USB-C shield). I can't and I don't push you to remeasure my DAC but for the future of the audioSCIENCEreview.com better if you'll correct your setup.

View attachment 119687
@amirm please see it. Can you re-analysis the dac ( 9038D) ? If you can, we all would be grateful
 
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