Moving from 9038Q2M to a 9028Pro board

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The ones I have here are Elna RJH, are burgundy like those.
Are they labeled Silmic II?
My (4495)board follows the same basic layout has other similarities as far as parts, was assuming they were the same burgundy Elnas on both...

I have not yet seen burgundy silmic before.
 
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I am getting to where I just blindly remove and replace nearly all electrolytic capacitors, to start with on anything from eBay.
Went to look up a cap on a data sheet recently and discovered that that part didn’t exist in that configuration!

How does it sound so far?
 
Is that a mulit-layer board for sure? Maybe so, but they usually try hard not to. You can see some traces under the solder mask when a picture is highlighted a little.
 

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Judging by the traces and where they lead to, it has to be because there are points where there are no vias that are visible at all. So unless I am blind and I used a magnifier to check and found the soldering that initially I thought was an error immediately as a result. I think it is at least a 3 layer board. I also looked for raised traces as well.

As for the sound I already commented on that. Further listening this evening to acclimatize myself to the sound before mods reveals it actually sounds pretty nice as is. It has all the cues I am looking for right now, low frequency extension, purity of voice and yeah, the cymbals thingie sounds not bad at all. About that imaging thing....once I realized that one of my speakers was not toed in at the correct angle, that speaker adjustment fixed it up. My reference would go back to a very old DAC which is not relevant anymore though it was in its day well regarded. So I cannot comment as a comparison.

So as a stock unit for $140 or so that you just hook up transformers and you're ready to play I'd say it represents better value if you are able to put out a little more money.
That $140 includes, a display, remote control and "upgraded" clock as well. Yeah, we know it is not the best clock but it is a better clock than some other DACs.

The other thing is that I plan to make a Balanced to Single ended Tube based converter to periodically get that tube sound when I want. So those Balanced Outputs will come in handy. Hope it all goes well.

I have a case that I believe I can fit all the added Power supplies into it and I will mount the transformers remotely.

I have the schematic for it but when it was sent I was asked not to reveal it in public.

The board I believe is the same as in the thread http://www.diyaudio.com/forums/digital-line-level/314935-es9038q2m-board-136.html#post5449289

The power supplies and layout look identical.
 
Hello Mike

Do you plan to power directly the TCXO ?
It's very easy to do it ,there is a self near the TCXO
Remove it an connect a 3.3v LDO.

It seems for me that there is a significative sound improvment.

Serge

YES.

I plan to replace the LT1963 on the right with an LT3042 low noise reg. I will eventually do this by depowering both LT1963s by not connecting the ac input. Then I will lead wires directly to the output pins of the LT1963. This can be reversed at anytime. Looking at the data sheet, the LT1963 is protected by reverse voltage protection so it should be OK. Now when I look at the schematic, it looks like the output LT1963 simply leads to the ferrite filter and then to the clock circuit. The same output before the filter then feeds a couple of AMS117_1V2. I am thinking that the ferrite filter should remove more HF residual noise out of the LT3042 before it feeds the clock.

The other LT1963, I will also try to feed with an LT3042 with a 22uF Cset addition. Eventually I will replace this with a Sulzer_Borbeley PS using an LTC6655 1.25V as a reference. That PS is also op amp based as well very similar to what ESS recommends but it uses some feedback and I have an option of creating a reference from the output itself or after the prereg. Hope it will be stable starts up fine. Since I have all these boards in my hands, I will not need to fabricate too much.

I am also awaiting some 797s. I also try using these in the IV circuit at the single op amp stage and then try the LME49710s in the Borbeley circuit.

Then I will have to move on to the Borbeley Tube based balanced to single ended converter. Just need to find some ecc88s. With this I can get Tubey DAC sound or precise SS whenever I want.
 
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Completely separate power supplies seems (to me) like a good idea.

TCXO :winding, rectifying, filtering and LDO 3.3v
Digital :winding, rectifying, filtering and LDO 3.3v
Analog :winding, rectifying, filtering and LDO 3.3v

Actualy it is the same winding, rectifying, filtering for :
- LT1963 3.3v for TCXO and digital
- LT1963 3.3v for Analog
:D:D
Serge
 
Probably the AVCC supply, then. Maybe roughly somewhere around 20 - 40 times worse noise than an LT3045 with 4.7uf Cset, which is worse again than if Cset=22uf.

Yes, but the thing is the LT1963 sounds better than the 9038q2m with the LT3042. So it makes you wonder what really is the parameter that is important.
Is it that the 9038Q2m is more sensitive to AVCC and the 9028PRO less so, or is there something else going on. Beats me really, I just hear what i hear. maybe the LT3042 on the 9028PRO will not be good either. Time will tell.
 
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Completely separate power supplies seems (to me) like a good idea.

TCXO :winding, rectifying, filtering and LDO 3.3v
Digital :winding, rectifying, filtering and LDO 3.3v
Analog :winding, rectifying, filtering and LDO 3.3v

Actualy it is the same winding, rectifying, filtering for :
- LT1963 3.3v for TCXO and digital
- LT1963 3.3v for Analog
:D:D
Serge

If my other op amp PS for AVCC is successful then I can use a dedicated LT3042 to power the clock.
 
Yes, but the thing is the LT1963 sounds better than the 9038q2m with the LT3042.

Are we talking with our without IV output stage? Are you saying that LT1963 sounds better than LT3042 with everything else being the same (except for pro vs q2m dac chips)? If so, that would be very interesting because lots of people are using LT3045 and LT3042 based on specs alone and without doing any apples to apples comparisons.
 
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Yah, you're right. Remember I said the comparison WILL be apples to oranges. So the 38q2m with the voltage mode and LT3042 vs. The stock 9028pro with current mode and stock LT1963. The 9028Pro sounds better even before modding. So Yes, the difference could be the IV stage causing the main problem in the Q2M.

No matter, I got my fingers crossed that the mods to the 28PRO will bring substantial improvement over the 38Q2M with a lot less effort. I know the specs says otherwise but maybe a hidden aspect to the PRO chips that allows them to reach a higher level much easier whereas the 38Q2M must have everything down pat to sound good. i.e more sensitive to implementation. I really don't know at this point.
If such is the case and it is a big IF, then the PRO DAC chips might be better options for the enthusiast despite them costing a little more up front.

Ideally someone like yourself. Mark would best be able to judge having the Benchmark DAC3, modded 9038Q2M and ................ . Also you have instruments to guide the build. Each mod, I perform is cross the finger and hope it sounds better. Which is not that objective...I agree with the weakness.
 
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I have a scope, a DVM, an ultra-cheap logic analyzer, and a sound card.

Changing the subject a bit: Tried a new experiment this morning. Think I am going to change my upsampler recommendation from SRC4392 to AK4137. For some unknown reason the very high I2S and DSD sample rates just sound better - more accurate and less distorted sounding. Closer to DAC-3. However, DAC-3 does what it does without using high sample rates, so I don't see why it should be the high sample rates per se that makes things sound better when using much more than minimal upsampling. Maybe it is some side-effect of fairly extreme upsampling that produces the subjective improvement, just don't know. I would sure like to measure and see what I can find that might explain it.

Anyway, before finalizing a change in recommendation I would like to check a few more things, but I am definitely leaning that way.

To summarize the two SRCs at this point:
Benefits of SRC4392 are that it offers some worthwhile improvement in SQ, it is less expensive than AK4237, and it is known to be useful for jitter reduction.

Benefits of AK4137 are availability of higher sample rates, support for DoP and DSD formats, and it would seem, more SQ improvement than SRC4392 when used at the very highest sample rates.

By the way, the upsampled DSD and I2S formats sound very slightly different from one another (however it is they finally end up coming out of the DAC). Don't know which one is closer to real.

In relation to the above, the other new DAC board I decided to try appears not to be able to play higher than 192kHz, so it may end up that the existing modded DAC board will end up being the SQ winner between the two boards. Either that or maybe I will find some way to input higher than 192kHz formats into the new board. Have to wait and see how that turns out.
 
As for the sound I already commented on that. Further listening this evening to acclimatize myself to the sound before mods reveals it actually sounds pretty nice as is. It has all the cues I am looking for right now, low frequency extension, purity of voice and yeah, the cymbals thingie sounds not bad at all.

So as a stock unit for $140 or so that you just hook up transformers and you're ready to play I'd say it represents better value if you are able to put out a little more money. That $140 includes, a display, remote control and "upgraded" clock as well. Yeah, we know it is not the best clock but it is a better clock than some other DACs.
The $140 ES9028PRO board seems to have most of the quality features we would like to upgrade to. The 3 totally separated PS, I/V output and a better clock. I estimate adding USB input, PS source and a pre-drilled case will add up to about $300. The sound would have been good enough for most of us without further board upgrade.

The SU-5 assembled ES9038Q2M DAC has I/V and ready to run at $200. A good quality linear PS box will add about $30. I am waiting for Markw4's assessment on how good it sounds as is and quality of the parts, including clock used.

I have an assembled ES9038Q2M DAC with TFT display, USB for $120. I am about done upgrading it to LDO dual linear PS. But it has no I/V and the clock is not so good. It sound pretty good to me and like the filter adjustment, but I do not have a reference for high quality DAC. :confused:

Two low end, commercial ES9038Q2M DAC, Pro-Ject Pre Box S2 Digital and Topping D50, both get very good reviews without the I/V. But they get good separate PS. I am facing the question of how good is good enough. I am very tempted to get the SU-5 DAC if it sounds better than the ES9038Q2M board that started the ES9038Q2M thread. Any first hand input on comparison of the above mentioned 3 options is appreciated.
 
The 9028PRO board with the 'golden clock' you can buy on ebay for about $10 (only the clock, not the board) is not a low phase noise clock so far as anyone has been able to show.

The IV stage doesn't use quality thin film resistors and C0G caps in the signal path.

The voltage regulators, some of them anyway, probably need to upgraded.

The AVCC supply is one regulator for both left and right channels, so stereo separation is probably affected as would be expected.

It still does't have any way to upsample, either. My current recommendation for that may be changing from an SRC492 to an AK4137. I made some comments as to why in another thread, but I can post a link here if anyone is interested. I will have more to say about it later anyway after some more tests. The basic rationale for upsampling, which is the reason Benchmark and Crane Song use it, is to fix reconstruction filter issues that are a part of all hi-res DAC chips currently made (according to Benchmark).

Bottom line, I would agree it appears the 9028PRO board is better as-built than the 9038Q2M board. I don't know how much work or if it would even be possible to make the 9028PRO board sound as good as my modded 9038Q2M board. That remains to be seen. If the AVCC issue can be fixed then it can probably be made as good as my modded board, but the end cost will be more because there is still a lot to fix to make it the best sounding DAC it can be.

As far as the question of how good is good enough, I would say that I have been encouraging people to mod a headphone amp to go with the DAC mods. An high quality HPA would be pretty cheap to do, a whole lot less expensive than a power amp, and it will let you know how good your DAC actually sounds. Getting back to how good is good enough, it may depend on how good you have heard. Too much listening to a really good system risks making you want one. The safest protection is never listen to a good system, then you won't know how good it sounds and you can remain satisfied with whatever you have right now. For myself, I guess I can listen to some car stereos, but not all, and I can listen to iPhone audio some, but none is good enough for a main stereo. Since I know what a good one sounds like (potentially habit forming), that's what I want to have. I also want it to be able to serve some utility function such as be usable to mix a record with if the need arises, which it does now and then when people track me down asking me to do it for them.
 
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