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Review and Measurements of E1DA 9038S BAL Portable DAC & Amp

sajunky

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I suspect the cable runs +L and +R directly to the centerpins of the RCA's which is O.K.
The -L and -R carry the opposite signal of the + and are both active outputs. I expect these signals to go to the shields of the RCA.

The problem is that the shields are carrying signals in the cable but as soon as you plug them in any RCA connectored amplifier the shields (-R and -L) are connected directly as the amp has the shields connected (ground/return/common).
So what one basically does is connect -L and -R together (short them)
Shield is not carrying signal, I am sure of this. Shield is floating (connected only on the RAC plugs). This is what I do when fighting ground loops on unbalanced conections. Or just connecting 100pF capacitor on the floating side, not a DC connection.
 

solderdude

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Shield is not carrying signal, I am sure of this. Shield is floating (connected only on the RAC plugs). This is what I do when fighting ground loops on unbalanced conections. Or just connecting 100pF capacitor on the floating side, not a DC connection.

To what signal are the L+ and R+ referenced in that case ?
So you are basically saying only the L+ and R+ are connected to the center pins and the RCA shields in the mentioned cables are floating ?
In that case what is the purpose of having 2 wires to each RCA ?
Where did you get the info that the RCA shields are not connected to anything or which trick is used in these cables ?

Your trick would ONLY work when there is a groundloop or other ground connection already present, which in this case isn't so.
 
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sajunky

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To what signal are the L+ and R+ referenced in that case ?
So you are basically saying only the L+ and R+ are connected to the center pins and the RCA shields in the mentioned cables are floating ?
In that case what is the purpose of having 2 wires to each RCA ?
Where did you get the info that the RCA shields are not connected to anything or which trick is used in these cables ?

Your trick would ONLY work when there is a groundloop or other ground connection already present, which in this case isn't so.
1. There are diferential, isn't? They are referencing to each other.
2. On the cable there are two L+ and L- wires inside a shield. On the RCA side they are terminated L- to ground and L+ to center (as expected) and the shield is terminated on this side to ground. On this side only. On the other side shield is floating.
3. This is called a general engineering knowledge. Sounds right?
4. False, and I use this trick on unbalanced RCA connections, as already mentioned in my first post.
 

IVX

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solderdude

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1. There are diferential, isn't? They are referencing to each other.
2. On the cable there are two L+ and L- wires inside a shield. On the RCA side they are terminated L- to ground and L+ to center (as expected) and the shield is terminated on this side to ground. On this side only. On the other side shield is floating.
3. This is called a general engineering knowledge. Sounds right?
4. False, and I use this trick on unbalanced RCA connections, as already mentioned in my first post.

1: Correct there is no reference needed WHEN the signal is balanced. An additional screen can also be present.
BUT there is no screen here. ONLY L+ L- and R+ and R- on the output of the device as it is a balanced stereo 2.5mm TRRS connector for headphones so the ground/screen is not needed nor present.
You are talking about 3pin XLR to RCA converter, we are talking about TRRS 2.5mm stereo headphone to RCA

2: Incorrect... there is NO shield and it looks like the L- and R- are connected to the screen of the RCA. Again you are talking about XLR to RCA which does NOT apply here.

3: Correct and that's why there are only 4 wires, no shield as it is for connecting a 4 wire headphone... 4 wires, TRRS, 4 connections only, no ground

4: It is perfectly fine to use this trick, in fact a lot of balanced to RCA work this way... BUT in that case the screen is connected to common and thus one can use L+ and R+ (or L- and R-) single ended BUT referenced to ground.
You can NOT do this trick by NOT using a ground reference.
This is called a general engineering knowledge. Sounds right?
 
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FunctionalDoc

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@IVX
I can't wait to get your PowerDACV2 and I was just thinking you need to send your great stuff to @amirm since people on this site will appreciate your great engineered products.

Congratulations
Rick
 

Rem

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It's really good. I think it could be better with 3.5mm to be used as at an at home dac, then something for portable use as well. Only issue is that I doubt it would have anywhere near same power as the balanced connection so it's a trade off. I like it though still, great results!

Unless this could be hooked up to an unbalanced amp like an atoms...?
 
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Music1969

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1: Correct there is no reference needed WHEN the signal is balanced. An additional screen can also be present.
BUT there is no screen here. ONlY L+ L- and R+ and R- on the output of the device as it is a balanced stereo 2.5mm TRRS connector for headphones so the ground/screen is not needed nor present.
You are talking about 3pin XLR to RCA converter, we are talking about TRRS 2.5mm stereo headphone to RCA

2: Incorrect... there is NO shield and it looks like the L- and R- are connected to the screen of the RCA. Again you are talking about XLR to RCA which does NOT apply here.

3: Correct and that's why there are only 4 wires, no shield as it is for connecting a 4 wire headphone... 4 wires, TRRS, 4 connections only, no ground

4: It is perfectly fine to use this trick, in fact a lot of balanced to RCA work this way... BUT in that case the screen is connected to common and thus one can use L+ and R+ (or L- and R-) single ended BUT referenced to ground.
You can NOT do this trick by NOT using a ground reference.
This is called a general engineering knowledge. Sounds right?

Can the DAC designer @IVX please comment on all this? For clarification

Especially the original comment that started this discussion:

"So there is really no issue at all in connecting up to the Atom via the 2.5mm TRRS output of this device."
 

IVX

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Can the DAC designer @IVX please comment on all this? For clarification

Especially the original comment that started this discussion:

"So there is really no issue at all in connecting up to the Atom via the 2.5mm TRRS output of this device."
I'm sorry, I've no idea about the atom, which they mentioned at least )) If you'll give me some input, I'll comment, no problem.
 

solderdude

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You will hear music when it is connected to the atom simply because the L- and R- are connected together and will work as a reference.
It will work perfectly when you are playing a mono signal.
The problems start with stereo.
In that case there are voltage differences between L- and R- and as these outputs from its internal amplifiers are connected directly to each other as soon as the cable is plugged in any stereo device with RCA inputs (as the grounds are always connected) the L-R difference signal will be pumping into the very low output resistance of the L- and R- output stages effectively shorting the device in the negative output for stereo signals.

The mentioned cable effective shorts active outputs (L- and R-) for stereo signals

One can connect a TRRS cable to any balanced input of a headphone amp/pre-amp, console, monoblock power amps, active speakers.
 
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Shadrach

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Congratulations IVX.:)
Slightly amused by the 'it will do for an office/desktop system' when it performs better than many of the main system offerings.
I don't see the balanced output connector being much of a problem. Even when including the cost of a suitable cable the unit is still outstanding value for money.
I hope the production units will be available in black and the made in China logo hidden as much as possible. It seems a silly point but it will matter to many.
A thing I have found irritating with some of the miniature dac/amp units is you are left with a choice of have the unit dnagling on the end of cables, or finding a suitable method of fixing it to a surface.
 

Music1969

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I'm sorry, I've no idea about the atom, which they mentioned at least )) If you'll give me some input, I'll comment, no problem.

Can your DAC be connected to a typical headphone amp single ended RCA inputs, using a cable like this:

https://www.aliexpress.com/item/33011627751.html

Or your DAC can strictly only be connected to balanced headphones or balanced DAC inputs?

That seems to be the discussion by others in posts above.

And 2nd question

Can you recommend an adapter that will allow this DAC to be hooked to headphone amp balanced XLR inputs? So only using your DAC as DAC only.
 

IVX

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Could you please tell me, how do you gonna use #9038S? I cant' catch the idea to use #9038S 3.5VRMS output as input for a further headphone amplifier. Do you need more power for your headphone? You know, my HFM HE400i in the bottom end for sensitivity even for planars, and I have 120db SPL with 340mW, it is loud! f you want to use #9038S as a DAC before the power amp, I mean speakers amp purpose, it is ok, you only need to tie GND wire to the USB-C connector anyhow(crocodile-clamp?).
 

Veri

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Could you please tell me, how do you gonna use #9038S? I cant' catch the idea to use #9038S 3.5VRMS output as input for a further headphone amplifier. Do you need more power for your headphone? You know, my HFM HE400i in the bottom end for sensitivity even for planars, and I have 120db SPL with 340mW, it is loud! f you want to use #9038S as a DAC before the power amp, I mean speakers amp purpose, it is ok, you only need to tie GND wire to the USB-C connector anyhow(crocodile-clamp?).
I believe use case would be to use it at full volume as a line-out, and use another desktop amp with a knob to control the volume :)
Your DAC has excellent specs for this theoretical use case. Problem would be how to "properly" connect the output to XLR inputs.

I think the guys at Ghent would definitely be willing to create a 2.5mm to XLR cable if possible/plausible/good enough option without obvious drawbacks or concerns. Someone should shoot them a mail!! https://www.ghentaudio.com/part/list-35trs.html currently using their A01 RCA and B06. both are really well made.
 

Music1969

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I believe use case would be to use it at full volume as a line-out, and use another desktop amp with a knob to control the volume :)
Your DAC has excellent specs for this theoretical use case. Problem would be how to "properly" connect the output to XLR inputs.

Correct - need a knob to adjust volume @IVX

Will use your DAC as DAC only, as previously mentioned above.
 

August

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Does the designer live in China? I hope there are ways to buy in China!:):)
 
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