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ES9038Q2M Board
ES9038Q2M Board
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Old Today, 11:50 AM   #3661
kaytata is offline kaytata  India
diyAudio Member
 
Join Date: Mar 2012
Hi Mark,
Another set of questions.
1. Am I correct in assuming that the Vref output of AVCC is to be connected to the ground (-) point of the AVCC Caps on the board?
2. Which DAC outpins pins connect to the Vref R&L input on the Output Stage Board, is it AGND L&R?
3. For the i2c connection, which one would be easier, pin-lifting or trace cutting as you have done?
Cheers,
Kay.
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Old Today, 05:36 PM   #3662
Markw4 is offline Markw4  United States
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Join Date: Jul 2016
Location: California
Quote:
Originally Posted by kaytata View Post
1. Am I correct in assuming that the Vref output of AVCC is to be connected to the ground (-) point of the AVCC Caps on the board?
No. The Vref for each of the left and right channels needs a wire that goes down to the the output stage board. It is connected to the non-inverting inputs of the I/V opamps for that left or right channel respectively, as should be shown on the schematic.

Quote:
2. Which DAC outpins pins connect to the Vref R&L input on the Output Stage Board, is it AGND L&R?
If you look at the pinout diagram for the dac chip you can see there are two outputs for each channel. One of each has a letter 'B' suffix or other indication that it is the inverted phase output. In the output stage, all the I/V opamp circuits are inverting, so both dac outputs will be inverted there. In the next opamp, the differential summing amp, the output from one I/V is inverted again, and the other one isn't. That subtracts the two signals to take the difference. The signal that gets inverted there will have been inverted twice in the output stage, thus they cancel out and it will be un-inverted at the output. That signal should in theory come from the non-inverting dac chip output. In the schematic that MrSlim drew, he labeled the I/V inputs correctly to show which inputs should come from which dac chip outputs. Also the dac chip is arranged with outputs symmetrical about the center axis. The way I built my output stage, the outputs are also symmetrical about the center axis of the dac board. So, if the outer dac outputs are connected to the outer (or inner) I/V opamps, it all works out okay. That is to say, if the phase of the left channel is reversed, it will not hurt the sound so long as the phase of the right channel is also reversed. The most important thing is that both channels are in the same phase. I will attach the pinout diagram of the dac chip below for reference.


Quote:
3. For the i2c connection, which one would be easier, pin-lifting or trace cutting as you have done?
Can't say that one is easier than the other exactly. I have always said to practice first on an old scrap circuit board before trying it on the dac board. There are a couple of risks with pin lifting. If they used a lot of hard, high temperature solder to solder down the MCU pins, then if you try to pry them off cold, chances of tearing the PCB traces may be high. If they are damaged, then you will have to solder traces to repair the connections. Also, if you bend MCU pins too many times they will break off pretty easily. Really try for bending them into place only once. If they are not perfect, but you can solder to them, then leave them as they are and solder to small leads to them, then glue the wires to the top of MCU with thick super glue or otherwise secure them against being disturbed. If there is thick, hard solder on the MCU pins, best to try to add some soft leaded solder, or maybe try to chip quik just those two pins, being careful not to get any on other pins, or you will have to clean them off and resolder them to finish the job. If you add soft solder, wick off as much as possible before trying to pry up the pins (you want the solder connection to be weak). What makes trace cutting hard is that the traces are small and close together, and jumper pins are close by making access to the traces limited. That may be the safest method since you can have some do-overs at another location on the traces if you damage them too much. The idea is to try to scrape solder mask only off the trace you want to solder. Then solder won't stick to the wrong trace. If you accidentally scrape some solder off an adjacent trace you can protect it from solder with a thin piece of mylar tape. Tin the trace first and tin the wire too, then solder them together. Again, practice first if there is any way you can find a junk board of some kind to work on.

Getting back to what happens if a pin breaks off the MCU, sometimes it may be possible to solder a tiny wire to side of the chip where some of the pin is exposed. If that doesn't work, then you would have to get to work on your Arduino to make it control the dac chip for everything. I know how to do it, so let me know if that happens and we can talk, probably offline, about what to do.
Attached Images
File Type: png ! Pinout.png (178.5 KB, 38 views)

Last edited by Markw4; Today at 05:49 PM.
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Old Today, 07:47 PM   #3663
PJN is offline PJN  United States
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Join Date: Dec 2004
Location: Pa, USA
Hi Mark,

I'm finishing up my output stage and will post pics soon. Just some questions to make sure that I don't screw things up. I remember you said that Vref is half of AVCC, and that I should make a voltage divider using two 10R resistors, AVCC in, two resistors on outlet, one to gnd the other is Vref. I plan on putting the dividers on my filter board to avoid hacking up the day board. Looking at the chip pinouts there is AVCC-r and AVCC-l. Can I just pull AVCC from the outlet of the regulator on the board and use the one source to make Vref-r and Vref-L. If yes can you point me to the best spot to safely pull AVCC from. If I need to pull AVCC-R and AVCC-L from the dac board could you point me to the best spots to pull them from the board.

Thanks,

Paul
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Old Today, 08:01 PM   #3664
Markw4 is offline Markw4  United States
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Join Date: Jul 2016
Location: California
Hi Paul,
The AVCC schematic (and BOM for Vref component part numbers) we use shows how to produce Vref for each of the left and right channels. It uses a voltage divider composed of two 10k 0.1% tolerance metal film resistors (not 10R!) with a 10uf filter cap to ground on the output. There is one divider for each channel to help maintain best stereo separation and the correct Vref values. You could run an AVCC wire from each channel down to the output stage board and put the voltage dividers there, or maybe put them somewhere on the dac board ground plane more towards the output stage end, wherever there is some space for them. Then from there, the Vref signals can go to the I/V non-inverting inputs for each channel. Probably good to keep the wires close to the ground plane to avoid picking up noise. A little tape can be used if it helps to keep them in place. If you are sure the wire layout is final, you could tack the wires in place with a little super glue in a few places.

Regards,
Mark

EDIT: The schematic and BOM can be found in post #3003 from MrSlim: ES9038Q2M Board

Last edited by Markw4; Today at 08:10 PM.
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Old Today, 08:29 PM   #3665
PJN is offline PJN  United States
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Join Date: Dec 2004
Location: Pa, USA
Hi Mark,

Great, I'll copy the divider from the AVCC schematic. Meanwhile I don't have an AVCC board yet and want to test the output stage first before moving to replace the existing AVCC on the dac board. Can you suggest a easy spot to solder wires to on the existing dac board to get AVCC-R, AVCC-L to my output stage board.

Also I was planning to feed the output stage by taking the inputs from the existing opamp holder on the dac board, any problems with that plan. I'm trying to keep my mods reversible in case I screw up.

Thanks,

Pau
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Old Today, 09:00 PM   #3666
eslei is offline eslei  New Zealand
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Join Date: Jul 2011
Quote:
Originally Posted by kaytata View Post

1. Am I correct in assuming that the Vref output of AVCC is to be connected to the ground (-) point of the AVCC Caps on the board?
2. Which DAC outpins pins connect to the Vref R&L input on the Output Stage Board, is it AGND L&R?
3. For the i2c connection, which one would be easier, pin-lifting or trace cutting as you have done?
hi, there,

the vref is not related to the avcc but the opamp power supply, if that's +5v supply the +v to 5v, the -v to gnd, if that's +,- 15 v supply the +v to +15v, -v to -15v. pls see the schematic attached.

the i2c connection, what dac board do you have? if the smp cb vr1.07 we just put the j1 and j2 on will stop the mcu.


cheers
Attached Images
File Type: jpg vref.jpg (18.2 KB, 14 views)
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Old Today, 09:11 PM   #3667
Markw4 is offline Markw4  United States
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Join Date: Jul 2016
Location: California
Hi Paul,
If you haven't modified the original AVCC circuit at all, you can pick up 3.3v from the bottom of the board where the existing through-hole AVCC electrolytic filter cap leads are soldered on. There is one cap for each channel. One lead of each existing cap goes to ground, and the other lead that is closer to the dac chip should be the one you want.

EDIT: While you are working in that area, you might be able to temporarily improve sound quality somewhat by tacking on some more electrolytic caps in parallel with the caps where you attach the AVCC wires. One fellow by the name of victor used three 1800uf electrolytics in parallel for each AVCC channel. He said it helped reduce harmonic distortion a lot.

Regarding where to pick up the dac chip output signals, you will need to unsolder and remove two existing SMD resistors or cut the traces leading to them from the dac chip and attach there. Probably easiest just to remove the resistors and solder your leads onto the existing solder pads (you can replace the resistors later if you really decide you want to). I drill a tiny hole between the two resistor solder pads and run a piece of #28 or #30 wire wrap wire though each hole, then solder one to each pad going to the dac chip. On the bottom of the board, twist the wires together and route them to the I/V inputs (keeping track of which wire goes to which dac output).

A pic below shows the dac output connections outlined in red.
Attached Images
File Type: jpg DACouts.jpg (873.9 KB, 12 views)

Last edited by Markw4; Today at 09:19 PM.
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Old Today, 09:26 PM   #3668
Markw4 is offline Markw4  United States
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Join Date: Jul 2016
Location: California
Quote:
Originally Posted by eslei View Post

the vref is not related to the avcc but the opamp power supply...
Hi eslei,
Don't know where you got that idea, but it is not what ESS says you should use for Vref. If you would like to see for yourself, there is a schematic of an older (maybe ES9008) evaluation board schematic on the ESS downloads page. You can clearly see that Vref is taken as half of AVCC for each channel using a voltage divider as we do in our AVCC board schematic. In addition, I have the schematics for the latest ES9038PRO evaluation boards from ESS and it is still exactly the same thing.

However, I agree with you about connecting I2C on the newer 1.07 SMP CB boards in that installing J1 and J2 should stop I2C bus activity by the MCU, thus making it unnecessary to do any trace cutting or pin lifting. However, I have a 1.07 board like that here and installing J1 and J2 didn't stop it. That same board also didn't work with an optional display I got to try out with it. I assume I happened to get a board with the wrong version firmware installed. If so, it appears to be a very rare problem. Really helps to have some kind of a scope available to check such things. Also, I just kind of assumed that since Kay asked the question, he knew he didn't have one of the boards that can be stopped with J1,J2. Maybe I assumed too much?

Last edited by Markw4; Today at 09:36 PM.
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