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ES9038Q2M Board
ES9038Q2M Board
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Old Yesterday, 07:52 PM   #1511
TioFrancotirador is offline TioFrancotirador  Poland
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or maybe not that much anyways does anyone know what are those control and reference voltages in this clock?
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Old Yesterday, 08:09 PM   #1512
Markw4 is online now Markw4  United States
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Control is probably to set the temperature of the heater for maximum frequency stability, or tweak it if there is any long term drift. Reference is probably feedback from the temperature sensor so you can monitor it is working.
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Old Yesterday, 08:18 PM   #1513
TioFrancotirador is offline TioFrancotirador  Poland
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Quote:
Originally Posted by Markw4 View Post
Control is probably to set the temperature of the heater for maximum frequency stability, or tweak it if there is any long term drift. Reference is probably feedback from the temperature sensor so you can monitor it is working.
Thanks. Do you think those are necessary to make this clock working? or it is just enough to connect 3.3V, GND and output?
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Old Yesterday, 08:31 PM   #1514
Markw4 is online now Markw4  United States
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Don't know. My guess is it would probably work, but I don't know about meeting all it's specifications. It would probably be safe to set the control voltage to the middle of it's range and ignore the reference signal.
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Old Today, 12:35 AM   #1515
Mikett is offline Mikett  Canada
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Quote:
Originally Posted by eziitis View Post
simply changing ams1117 to lt3045 does not bring any measurable improvement for the board discussed in this thread. btw majority of Chinese boards use LT1963, apparently because of its fast transient response. actually, there is not even need for a fancy LDO, even 317 regs correctly implemented will be fine:

Nazar's Regulator: アナログ回路のおもちゃ箱
PSU for High end audio without electrolytic capacitors_2: アナログ回路のおもちゃ箱
Been listening to a 9028pro Ebay board using the LT1963. In stock form, this board blows away this 9038Q2M dac board with an LT3042 for AVCC. Now remember this an apples oranges comparison so bear that in mind. However, I now can tell immediately that the single OP amp 9038Q2M badly needs a proper IV stage. Secondly if you add in an LT3042/5 stage for AVCC without adding a proper IV stage, it is a wasted effort. So if you intend to use this cheap 9038 board, you gotta commit to making up your own IV stage as well as an OP amp PS for AVCC. In that form it might be superior to this 9028 Ebay DAC. I had version 1.04 of the 9038q2M and I blew it up while making an outboard IV stage and Op amp AVCC supply.

The stock as delivered ebay DAC using the LT1963 for AVCC using the stock 317/337/5532/*5534 sounds a lot more refined than this 9038q2m when modded with a LT3042, LME49720 op amp driven with a HP low noise low Z Sulzer power supply for the linear stages. Both boards were using filtered AC through a CORCOM filter.

When I add the LME49720/LME49710 op amps to the 9028pro DAC, it removes some of the thickness of the 5532/5534 and gains transparency and removes midrange veiling. I have yet to mod the AVCC and add the Sulzer PS to replace the 317/337. But as it is now.....it sounds sweet with the only weaker point in that the front to back is a little shallow (AVCC related based on my experience with the 9038Q2M) and I can "hear" the slightly compressed dynamic contrast which I think is the signature of the 317/337. Low end is not a problem with the 9028pro board like it was with the 9038Q2M board. I will make a new thread eventually outlining what I am doing after experimenting and learning with the now "smoked out" 9038Q2M board.
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Old Today, 02:59 AM   #1516
Markw4 is online now Markw4  United States
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Hi Mikett, Good to hear from you. Of course you are quite right that going with a proper AVCC supply and IV output makes a really big difference in SQ. Don't forget to use good tight tolerance thin film resistors and C0G caps in the signal path. Also decouple power rails at each chip directly to a very close-by ground plane. If using leaded decoupling caps, ground them separately to keep inductance low, or maybe use a flat, wide-as-reasonable piece of copper foil as a low inductance ground strap for both. Keep it short is all.

Still not quite where it needs to be at that point, but it sure is better.

Add an ultra-low jitter clock (with fast enough edges), then add upsampling, and select the minimum group delay reconstruction filter.

Assuming proper power supplies by that point and one is probably good to go. (according to ESS, separate regulators for digital and analog power pins, and another one is suggested for any microcontroller - they don't have to all be super quality except for AVCC of course, they just need to be reasonably good, clean, separate, and hopefully close to the pins they regulate - the clock may be considered as analog, as is VCCA).

The only other possible things I can think of offhand to do would be to fix the reconstruction filter with an outboard DSP, and drop the master volume level send from Windows (or other OS) by 3.5dB to help prevent intersample overs. (The external DSP would probably be overkill, but maybe I will continue to think about it.)

Last edited by Markw4; Today at 03:21 AM.
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