During the modification of my 9038Q2M dac as on this thread http://www.diyaudio.com/forums/digital-line-level/314935-es9038q2m-board.html
I accidentally killed my cheap DAC. This provided me an opportunity to decide whether to start all over again with the above DAC or start over with another kit but having perhaps less requirement for fabrication.
I looked at various DAC boards on Ebay and elected to not get something too costly because I could very well destroy it again and if I did. I would simply purchase something and be done with it.
Via the above thread I realized that substantial fabrication would be required and I did not wish to go to making boards again. With the cheap Es9038q2m mentioned, one needs to fabricate an op amp PS for AVCC as well as fabricate a new IV section for the DAC as the single op amp circuit on the board is simply not good despite putting on better op amps.
Then I saw a DAC board that looked interesting.
It has a proper IV converter section. I chose to stick with the 9028pro because the PS requirements were a lot less than a 9038Pro. Next, I wanted to get an DAC where I could easily insert improved PS sections that without too much trouble. I also desired a display.
The board I ended up with I think is a reasonable cost. It is a 9028pro board and the same design appears to be also used for the 9038pro. It can be found on numerous offerings on Ebay and AliExpress and appears to be a popular board. It uses 3 terminal regulators for the op amp supply...which easily allows me to insert improved PSs like a Sulzer which I already had or put in even a Super regulator for which I might still have some parts if I wanted to build one. It has one compromise. Left and Right AVCC is fed from a common regulator., has a display and a remote.
The project is not finished but this would be a project as it progresses I will report.
Warning, this thread will have a minimum of measurements as I don't have the equipment. So any reports of any improvement as I mod needs to be looked at as not fact but opinion. I state that up front.
After having received my DAC board, in stock form it had 5532/34 op amps. These provided a strong sense of midbass with a thick sound. High frequencies were slight muted. Changing these to LME49720 and LME49710 op amps removed the heavy midbass and provided more extended or more transparent sound. I had noted somewhat similar characteristics on the cheaper DAC but it was much more noticeable now.
The cheaper 9038q2M DAC before I killed it, had been modified. A lowZ low noise Sulzer Power supply was feeding the op amp and an LT3042 was feeding the DAC section. The LT3042 had 15uF of film caps for Cset. The DAC section had been modified by putting in 470uF OSCON sepc caps for decoupling.
The op amp IV section on the cheap DAC was in voltage mode with a single op amp section.
Now the stock 9028pro with the switch to the LME497xx op amps easily easily beat out the 9038q2m modded as above in the following areas. Lower octaves were more solid and defined. Separate voices were more distinct and transparent. This possibly points to the aspect that an ESS based DAC must have a proper IV section and the DAC must be operating in current mode for it to be good.
So as time progresses I will press forward by installing improved power supplies and possibly upgrading clocks and possibly upgrading on board components to better match ESS recommended circuits.
First I will install an improved power supply for the op amps.
I accidentally killed my cheap DAC. This provided me an opportunity to decide whether to start all over again with the above DAC or start over with another kit but having perhaps less requirement for fabrication.
I looked at various DAC boards on Ebay and elected to not get something too costly because I could very well destroy it again and if I did. I would simply purchase something and be done with it.
Via the above thread I realized that substantial fabrication would be required and I did not wish to go to making boards again. With the cheap Es9038q2m mentioned, one needs to fabricate an op amp PS for AVCC as well as fabricate a new IV section for the DAC as the single op amp circuit on the board is simply not good despite putting on better op amps.
Then I saw a DAC board that looked interesting.
It has a proper IV converter section. I chose to stick with the 9028pro because the PS requirements were a lot less than a 9038Pro. Next, I wanted to get an DAC where I could easily insert improved PS sections that without too much trouble. I also desired a display.
The board I ended up with I think is a reasonable cost. It is a 9028pro board and the same design appears to be also used for the 9038pro. It can be found on numerous offerings on Ebay and AliExpress and appears to be a popular board. It uses 3 terminal regulators for the op amp supply...which easily allows me to insert improved PSs like a Sulzer which I already had or put in even a Super regulator for which I might still have some parts if I wanted to build one. It has one compromise. Left and Right AVCC is fed from a common regulator., has a display and a remote.
The project is not finished but this would be a project as it progresses I will report.
Warning, this thread will have a minimum of measurements as I don't have the equipment. So any reports of any improvement as I mod needs to be looked at as not fact but opinion. I state that up front.
After having received my DAC board, in stock form it had 5532/34 op amps. These provided a strong sense of midbass with a thick sound. High frequencies were slight muted. Changing these to LME49720 and LME49710 op amps removed the heavy midbass and provided more extended or more transparent sound. I had noted somewhat similar characteristics on the cheaper DAC but it was much more noticeable now.
The cheaper 9038q2M DAC before I killed it, had been modified. A lowZ low noise Sulzer Power supply was feeding the op amp and an LT3042 was feeding the DAC section. The LT3042 had 15uF of film caps for Cset. The DAC section had been modified by putting in 470uF OSCON sepc caps for decoupling.
The op amp IV section on the cheap DAC was in voltage mode with a single op amp section.
Now the stock 9028pro with the switch to the LME497xx op amps easily easily beat out the 9038q2m modded as above in the following areas. Lower octaves were more solid and defined. Separate voices were more distinct and transparent. This possibly points to the aspect that an ESS based DAC must have a proper IV section and the DAC must be operating in current mode for it to be good.
So as time progresses I will press forward by installing improved power supplies and possibly upgrading clocks and possibly upgrading on board components to better match ESS recommended circuits.
First I will install an improved power supply for the op amps.
Attachments
First mod, I will remove the three term regs and insert a superior PS I have on hand.
power supply sulzer-borbely
I have many of these power supplies in my box after the Super Regulators supplanted them. I just noticed, that I should be able to mod this to power AVCC as well if I just find a low enough component to replace the LM329Z....the LTC6655
http://www.analog.com/media/en/technical-documentation/data-sheets/6655ff.pdf
Hey MarkW4, maybe I learnt something.
power supply sulzer-borbely
I have many of these power supplies in my box after the Super Regulators supplanted them. I just noticed, that I should be able to mod this to power AVCC as well if I just find a low enough component to replace the LM329Z....the LTC6655
http://www.analog.com/media/en/technical-documentation/data-sheets/6655ff.pdf
Hey MarkW4, maybe I learnt something.
Attachments
Mikett, Do you know what under the other heat sinks? Looks like 5-terminal power ICs. Are those more voltage regulators?
They are 2 - LT1963 1500ma Fast Trasient LDO regs. http://www.analog.com/media/en/technical-documentation/data-sheets/1963fc.pdf
One feeds AVCC Left and R shared. The other provides the other 3.3V to clock and to 2x AMS1117 1.2V to the DAC etc.
I have 2 LT3042 to feed these now as soon as I mod them for 5V to 3.3 V.
The LT1963 is supposed to be protected from reverse voltages so I think I can tack on the feed from the external 3.3V sources whether it be from the LT3042 or Sulzer to be modded for 3.3V. I've ordered this board MLT - LTC6655 High Precision Voltage Reference Breakout Module | eBay to mod my Sulzer PS for AVCC
One feeds AVCC Left and R shared. The other provides the other 3.3V to clock and to 2x AMS1117 1.2V to the DAC etc.
I have 2 LT3042 to feed these now as soon as I mod them for 5V to 3.3 V.
The LT1963 is supposed to be protected from reverse voltages so I think I can tack on the feed from the external 3.3V sources whether it be from the LT3042 or Sulzer to be modded for 3.3V. I've ordered this board MLT - LTC6655 High Precision Voltage Reference Breakout Module | eBay to mod my Sulzer PS for AVCC
Attachments
Last edited:
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.
Last edited:
I know. But I will accept that compromise unless I see a breakout where I can come back in. Like the traces to the AVCC divider. I will try and follow that back out and see.
Is this the same board that was referenced early on in the other 9038 thread?
I wondered why no one put up a link to it when it seemed to have a lot going for it...
Those purple elnas aren’t helping you, discovered that on a similar dac here recently, and if you can manage to get a COG .1uf for the clock, that will help a lot also.
I’ve been pretty happy with the lt1963 so far.
I wondered why no one put up a link to it when it seemed to have a lot going for it...
Those purple elnas aren’t helping you, discovered that on a similar dac here recently, and if you can manage to get a COG .1uf for the clock, that will help a lot also.
I’ve been pretty happy with the lt1963 so far.
The challenge is that the first decoupling cap leading from the AVCC LT1963 then feeds to other decoupling caps closer to the DAC via an inner layer. At those points, the designers feed from there to the two AVCC resistor divider circuits via a surface trace layer on the board. So the challenge is to cut off the feed from the first cap to the other caps...inside the board.
How about removing the resistor dividers and tossing them? Run new wires above board to the pads. ... Although, it doesn't make sense to have resistors last, should be caps last before the AVCC pins. 😕
Are you referencing the SilmicIIs? The burgundy ones are SilmicIIs. The lighter color ones are 33uF Sanyo oscons.
Last edited:
Yeah there caps before the AVCC pins but they are connected inside the layer to the LT1963. So essentially the L&R AVCC feed branch out inside the board.
