Since the I2S-PCM driver board is soon to be released the idea came up to create some bare DAC boards that could be coupled with.
The concept is a core board for multibit DACs, with keeping anything else such as digital front end, I/V, power supply external. To reduce the complexity and cost each DAC will have its own core board with same size and same interface, so it can become a standard part in the system.
Why only a core board with everything else external?
- to let us easily swap the DAC
- most of us already have different breeds of power supplies
- some may have an I/V but want to try out others. Would be nice to continue this idea for different I/Vs as well.
There were some starting ideas about this board:
- 2 layers (if mostly possible)
- options for stereo / balanced / dual mono configurations - this means it has to hold 2x stereo DACs or 4x mono DACs
Open questions (that comes to my mind):
- size of the board
- how to integrate it with other components
- power supply options
- I/V options
Once we decide about the questions, volunteers are needed to design the PCB and/or prototype and test it. I'm offering to design, prototype and test the AD1865 DAC and later on the PCM1704.
L.E. Policies for better readability: since this thread is dedicated for multiple core boards let's use the Title of a post to differentiate between subjects, like this:
- Core Board: posts related to standardization of the core board and _not_ specific DACs related: e.g. size of the core board, connector placement, etc
- AD1865: related to this DAC
- TDA1541:....
Regards,
Zsolt
The concept is a core board for multibit DACs, with keeping anything else such as digital front end, I/V, power supply external. To reduce the complexity and cost each DAC will have its own core board with same size and same interface, so it can become a standard part in the system.
Why only a core board with everything else external?
- to let us easily swap the DAC
- most of us already have different breeds of power supplies
- some may have an I/V but want to try out others. Would be nice to continue this idea for different I/Vs as well.
There were some starting ideas about this board:
- 2 layers (if mostly possible)
- options for stereo / balanced / dual mono configurations - this means it has to hold 2x stereo DACs or 4x mono DACs
Open questions (that comes to my mind):
- size of the board
- how to integrate it with other components
- power supply options
- I/V options
Once we decide about the questions, volunteers are needed to design the PCB and/or prototype and test it. I'm offering to design, prototype and test the AD1865 DAC and later on the PCM1704.
L.E. Policies for better readability: since this thread is dedicated for multiple core boards let's use the Title of a post to differentiate between subjects, like this:
- Core Board: posts related to standardization of the core board and _not_ specific DACs related: e.g. size of the core board, connector placement, etc
- AD1865: related to this DAC
- TDA1541:....
Regards,
Zsolt
Last edited:
TDA1541A core PCB
Hi Zsolt,
I have no software to design any kind of schematics for PCB creation (last time I used PCAD almost twenty years ago
), but will gladly participate here.
Some ideas about what should be included on core board for TDA1541:
1. Socket or sockets for TDA1541A
(depends on board size, but about it later).
2. Surrounding components:
2.1 U.FL and/or alternative connectors and 3.3V attenuators for LE, BCK, DATA_L, DATA_R signals;
2.2 SMD capacitor for oscillator (polystyrene or better COG/NPO) SMD 1208. I still do not understand how free running DEM oscillator by John (ecdesigns) can work succesfully with such wide range of sampling frequencies (44,1 kHz to almost 400kHz), so here is an open question - is it better than text book 470 - 680 pF capacitor?
2.3 connectors for all three power supply lines (per one TDA1541);
2.4. HF filtering SMD 1206 size capacitors on all power lines, placed nearby pins of TDA1541.
2.5 decoupling capacitors on power lines - in case we still have space for it: I think it is not bad idea to have the opportunity to use 100 - 220 uF OSCONs pin type, however it solely depends on power solution in certain DIY project - I'm not sure in case of use Salas shunt regulators (placed nearby core PCB) such power decoupling capacitors would help.
2.6 famous decoupling capacitors. I would place those right under TDA1541A on topside and/or downside of PCB as 1206 size SMD, making shortest way from those 14 capacitors to digital ground (pin 14). 1206 size solder pads would let us experiment with a lot of different types capacitors - whatever everyone needs (X7R, FCA alcylic or COG/NPO). You can also use here 1210 size capacitors, soldering those on side less than 1.8mm, for example 1uF FCA1210C105M-G2.
2.6 Jumper or at least soldering pads for selecting TDA1541 mode (pin 27 to DGND or pin 26 or pin 28) - not sure is it really needed if we are going use that PCB with Ian's FIFO and PCM converter - in offset binary simultaneous mode, but anyway...
2.7 on analog outputs - as minimum we need place for I/U resistor, as maximum - I/U resistor and CSS for 2mA injection to every output.
I guess or, better say, dream, that using all components SMD type, except TDA1541 itself and analog output parts, would allow to fit balanced set of two TDA1541 on double sided PCB 80x70mm (size of FIFO without clock board).
On the other hand, 80x60mm core PCB for ONE TDA1541 allows to make unbalanced stereo set (one board) or balanced set by two PCB (stacking one over another). Also not bad really.
Best regards
Saulius
Hi Zsolt,
I have no software to design any kind of schematics for PCB creation (last time I used PCAD almost twenty years ago
), but will gladly participate here.Some ideas about what should be included on core board for TDA1541:
1. Socket or sockets for TDA1541A
(depends on board size, but about it later). 2. Surrounding components:
2.1 U.FL and/or alternative connectors and 3.3V attenuators for LE, BCK, DATA_L, DATA_R signals;
2.2 SMD capacitor for oscillator (polystyrene or better COG/NPO) SMD 1208. I still do not understand how free running DEM oscillator by John (ecdesigns) can work succesfully with such wide range of sampling frequencies (44,1 kHz to almost 400kHz), so here is an open question - is it better than text book 470 - 680 pF capacitor?
2.3 connectors for all three power supply lines (per one TDA1541);
2.4. HF filtering SMD 1206 size capacitors on all power lines, placed nearby pins of TDA1541.
2.5 decoupling capacitors on power lines - in case we still have space for it
: I think it is not bad idea to have the opportunity to use 100 - 220 uF OSCONs pin type, however it solely depends on power solution in certain DIY project - I'm not sure in case of use Salas shunt regulators (placed nearby core PCB) such power decoupling capacitors would help. 2.6 famous decoupling capacitors. I would place those right under TDA1541A on topside and/or downside of PCB as 1206 size SMD, making shortest way from those 14 capacitors to digital ground (pin 14). 1206 size solder pads would let us experiment with a lot of different types capacitors - whatever everyone needs (X7R, FCA alcylic or COG/NPO). You can also use here 1210 size capacitors, soldering those on side less than 1.8mm, for example 1uF FCA1210C105M-G2.
2.6 Jumper or at least soldering pads for selecting TDA1541 mode (pin 27 to DGND or pin 26 or pin 28) - not sure is it really needed if we are going use that PCB with Ian's FIFO and PCM converter - in offset binary simultaneous mode, but anyway...
2.7 on analog outputs - as minimum we need place for I/U resistor, as maximum - I/U resistor and CSS for 2mA injection to every output.
I guess or, better say, dream
, that using all components SMD type, except TDA1541 itself and analog output parts, would allow to fit balanced set of two TDA1541 on double sided PCB 80x70mm (size of FIFO without clock board). On the other hand, 80x60mm core PCB for ONE TDA1541 allows to make unbalanced stereo set (one board) or balanced set by two PCB (stacking one over another). Also not bad really.
Best regards
Saulius
Core Board
The main idea is that all DAC boards will share the same size and have the same connectors to be easily replaceable.
Data input: all output connectors of I2S-PCM driver board: 10pin PH2.0 + all U-FL connectors.
PSU input: highly differs between multibit DACs but I think +0- for analog side and +0- for digital side covers all: so 2 x 3pin connectors.
Output: Since we have dual-mono/balanced then 4 x 2pin connectors.
Size and placement: we have from 20pin SOIC (PCM1704) to 28pin DIP (PCM63) everything. If we want to stick to the dual-mono/balanced setup for most common multibit DACs we have to be able to accommodate the largest footprint needed 4 x 28DIP. Maybe the size of FIFO-Clock board would be enough and this board could be placed alongside FIFO-Clock board...
The main idea is that all DAC boards will share the same size and have the same connectors to be easily replaceable.
Data input: all output connectors of I2S-PCM driver board: 10pin PH2.0 + all U-FL connectors.
PSU input: highly differs between multibit DACs but I think +0- for analog side and +0- for digital side covers all: so 2 x 3pin connectors.
Output: Since we have dual-mono/balanced then 4 x 2pin connectors.
Size and placement: we have from 20pin SOIC (PCM1704) to 28pin DIP (PCM63) everything. If we want to stick to the dual-mono/balanced setup for most common multibit DACs we have to be able to accommodate the largest footprint needed 4 x 28DIP. Maybe the size of FIFO-Clock board would be enough and this board could be placed alongside FIFO-Clock board...
Core Board
Please take into account that if you are going to have possibility for direct replacement (cold swap) of one DAC core board by another DAC core board, you need "standartise" all inputs and outputs of each core board, including approximate position of sockets (cabling issue).
So, not only sockets, but also supply voltages and analog signal type (I or U) and level of signal should be matched on certain pin of certain connector...
That means you can not use 2x3pin connectors for power supply, as you wrote. You need so many pins in each connector, how many supply voltages you have per whole list of DACs
!
Else you have no desired task solved - "cold swap" would lead to malfunction at least, damage at worst.
Concerning size of core board: I would not plan core board for 4xDIP28 set - it would be not enough space on 132x80mm board (FIFO+clock).
Please look photos of PCM63 in Rotel RCD-991 in Lukasz site: Rotel CD with tubes .
Length of one PCM63 is about 35mm (DIP28) - for scaling right on monitor
Those two PCM63 with surroundings (without capacitors for opamps) need at least 80x100mm area.
And this is without any sockets and MSB adjustment circuitry ( I see no trimmers in photos).
And actually without I/U conversion (no opamps - remember "standartised" level of output).
I guess, even complete usage of SMD components for surrounding would not allow to squeeze almost in same size area double set of parts.
So, take maximum FIFO "compatible" size, let say your mentioned 132x80mm board (FIFO+clock) and try to put here maximum 2 of DIP28 DAC chips.
Saulius
Please take into account that if you are going to have possibility for direct replacement (cold swap) of one DAC core board by another DAC core board, you need "standartise" all inputs and outputs of each core board, including approximate position of sockets (cabling issue).
So, not only sockets, but also supply voltages and analog signal type (I or U) and level of signal should be matched on certain pin of certain connector...
That means you can not use 2x3pin connectors for power supply, as you wrote. You need so many pins in each connector, how many supply voltages you have per whole list of DACs
!Else you have no desired task solved - "cold swap" would lead to malfunction at least, damage at worst.
Concerning size of core board: I would not plan core board for 4xDIP28 set - it would be not enough space on 132x80mm board (FIFO+clock).
Please look photos of PCM63 in Rotel RCD-991 in Lukasz site: Rotel CD with tubes .
Length of one PCM63 is about 35mm (DIP28) - for scaling right on monitor
Those two PCM63 with surroundings (without capacitors for opamps) need at least 80x100mm area
. And this is without any sockets and MSB adjustment circuitry ( I see no trimmers in photos).
And actually without I/U conversion (no opamps - remember "standartised" level of output).
I guess, even complete usage of SMD components for surrounding would not allow to squeeze almost in same size area double set of parts.
So, take maximum FIFO "compatible" size, let say your mentioned 132x80mm board (FIFO+clock) and try to put here maximum 2 of DIP28 DAC chips.
Saulius
Core Board
The idea is to have all PSU and I/V external - so the board should have current output _without offset_. Core boards with DACs that have offset like TDA1541 will have to take care about this by using a current source to null out the offset. As far as the current output level is concerned it will be between +-1mA to +-2mA (AD1865, AD1862, PCM1702/4, PCM58, PCM63, TDA1541) - double that for dual mono.
Good you brought up this direct replacement (cold swaping) issue: up to now I didn't thought about directly replacing one board with another _without adjusting the power supplies_. I thought when replacing e.g. AD1865 with AD1862 the user will consciously take care that analog voltage should be +-12V and when switching back to AD1865 he/she will change it +-5V - indeed it's easy to shoot yourself in foot this way.
So there are two possibilities:
1. Have only 2x3pin connectors but switching will need attention - power supply adjustment/change is needed
2. Have as many power connectors as many different DAC needs...
I would certainly choose #1 for simplicity and let the gravity of switching boards to the user.
Thanks!
Zsolt
I would like to have same position of input/output sockets for all boards.Please take into account that if you are going to have possibility for direct replacement (cold swap) of one DAC core board by another DAC core board, you need "standartise" all inputs and outputs of each core board, including approximate position of sockets (cabling issue).
So, not only sockets, but also supply voltages and analog signal type (I or U) and level of signal should be matched on certain pin of certain connector...
That means you can not use 2x3pin connectors for power supply, as you wrote. You need so many pins in each connector, how many supply voltages you have per whole list of DACs
Else you have no desired task solved - "cold swap" would lead to malfunction at least, damage at worst.
The idea is to have all PSU and I/V external - so the board should have current output _without offset_. Core boards with DACs that have offset like TDA1541 will have to take care about this by using a current source to null out the offset. As far as the current output level is concerned it will be between +-1mA to +-2mA (AD1865, AD1862, PCM1702/4, PCM58, PCM63, TDA1541) - double that for dual mono.
Good you brought up this direct replacement (cold swaping) issue: up to now I didn't thought about directly replacing one board with another _without adjusting the power supplies_. I thought when replacing e.g. AD1865 with AD1862 the user will consciously take care that analog voltage should be +-12V and when switching back to AD1865 he/she will change it +-5V - indeed it's easy to shoot yourself in foot this way.
So there are two possibilities:
1. Have only 2x3pin connectors but switching will need attention - power supply adjustment/change is needed
2. Have as many power connectors as many different DAC needs...
I would certainly choose #1 for simplicity and let the gravity of switching boards to the user.
Will check this tonight...Concerning size of core board: I would not plan core board for 4xDIP28 set - it would be not enough space on 132x80mm board (FIFO+clock).
Please look photos of PCM63 in Rotel RCD-991 in Lukasz site: Rotel CD with tubes .
Length of one PCM63 is about 35mm (DIP28) - for scaling right on monitor
Those two PCM63 with surroundings (without capacitors for opamps) need at least 80x100mm area
And this is without any sockets and MSB adjustment circuitry ( I see no trimmers in photos).
And actually without I/U conversion (no opamps - remember "standartised" level of output).
I guess, even complete usage of SMD components for surrounding would not allow to squeeze almost in same size area double set of parts.
So, take maximum FIFO "compatible" size, let say your mentioned 132x80mm board (FIFO+clock) and try to put here maximum 2 of DIP28 DAC chips.
Saulius
Thanks!
Zsolt
Last edited:
Core Board
OK, now we have clear requirements for sockets, output type and offset.
Actually, I had in my mind third possibility: power connector need to have dedicated pins for every voltage possibly needed for DAC chips and surrounding + GND, for example (-15;-12;-5;GND;+5;+12;+15).
Core board for TDA1541 would use 1,3,4 and 5 pins of power connector, PCM1704 would use 3,4 and 5 pin, etc. Indeed, this is long list of voltages, but it can be shortened if we are not going to make very universal "standard" for power supply here.
In that way if you really need cold swap for experiments, you simply need to have all necessary voltages for your experimental DAC type on power supply connector from your PSU side.
And no chance to make mistake during swap...
Thanks
Saulius
OK, now we have clear requirements for sockets, output type and offset.
Good you brought up this direct replacement (cold swaping) issue: up to now I didn't thought about directly replacing one board with another _without adjusting the power supplies_. I thought when replacing e.g. AD1865 with AD1862 the user will consciously take care that analog voltage should be +-12V and when switching back to AD1865 he/she will change it +-5V - indeed it's easy to shoot yourself in foot this way.
So there are two possibilities:
1. Have only 2x3pin connectors but switching will need attention - power supply adjustment/change is needed
2. Have as many power connectors as many different DAC needs...
I would certainly choose #1 for simplicity and let the gravity of switching boards to the user.
Actually, I had in my mind third possibility: power connector need to have dedicated pins for every voltage possibly needed for DAC chips and surrounding + GND, for example (-15;-12;-5;GND;+5;+12;+15).
Core board for TDA1541 would use 1,3,4 and 5 pins of power connector, PCM1704 would use 3,4 and 5 pin, etc.
Indeed, this is long list of voltages, but it can be shortened if we are not going to make very universal "standard" for power supply here. In that way if you really need cold swap for experiments, you simply need to have all necessary voltages for your experimental DAC type on power supply connector from your PSU side.
And no chance to make mistake during swap...
Thanks
Saulius
Core Board
I also would buy core boards for TDA1541A, PCM1704, AD1865 - all of these DAC chips are very promising.
Thanks
Saulius
I also would buy core boards for TDA1541A, PCM1704, AD1865 - all of these DAC chips are very promising.
Thanks
Saulius
Core Board
Question: do we need separate supply inputs for digital and analog side of a DAC? PCM1704(2), PCM63, AD1864(5) all have +-5V analog and digital.
I personally would follow the recommendation of PCM63/1704: "No real advantage is gained by using separate analog and digital supplies. It is more important that both these supplies be as “clean” as possible to reduce coupling of supply noise to the output"
I like this idea with multiple voltages in one connector. I would use two 4pin connectors though (-15,-12,-5,0) (0,5,12,15).
Thanks,
Zsolt
The simple approach has separate inputs for digital and analog voltages but without fixed voltages. On a second thought this separate analog/digital supply inputs would not be used when they are of same voltage.Actually, I had in my mind third possibility: power connector need to have dedicated pins for every voltage possibly needed for DAC chips and surrounding + GND, for example (-15;-12;-5;GND;+5;+12;+15).
Core board for TDA1541 would use 1,3,4 and 5 pins of power connector, PCM1704 would use 3,4 and 5 pin, etc.
Question: do we need separate supply inputs for digital and analog side of a DAC? PCM1704(2), PCM63, AD1864(5) all have +-5V analog and digital.
I personally would follow the recommendation of PCM63/1704: "No real advantage is gained by using separate analog and digital supplies. It is more important that both these supplies be as “clean” as possible to reduce coupling of supply noise to the output"
I like this idea with multiple voltages in one connector. I would use two 4pin connectors though (-15,-12,-5,0) (0,5,12,15).
Thanks,
Zsolt
Last edited:
Core Board
Size matters
I made some sketches with DACs to see how they fit... Those DIP 28pin mono DACs are mammoths, they need double space in comparison with smaller ones. If we want same size boards it's a waste of space/money when used for small ones.
I suggest to keep the balanced/dual-mono idea for small DACs and make stereo core boards for large DACs. If dual-mono or balanced is wanted for those simply stack them and use U-FL connectors - see how dvb projekt did the same with his DACs used in parallel.
If we go this route the core board could be the size of I2S-PCM board.
Size matters
I made some sketches with DACs to see how they fit... Those DIP 28pin mono DACs are mammoths, they need double space in comparison with smaller ones. If we want same size boards it's a waste of space/money when used for small ones.
I suggest to keep the balanced/dual-mono idea for small DACs and make stereo core boards for large DACs. If dual-mono or balanced is wanted for those simply stack them and use U-FL connectors - see how dvb projekt did the same with his DACs used in parallel.
If we go this route the core board could be the size of I2S-PCM board.
Attachments
Core Board
Waiting patiently for the AD1865 core board, save the trouble of making 1 myself. Thanks...
I see the inclusion of the THD+N Adjust Circuitry and also the negative supply for digital, possible to have some kind of a jumper to bypass these 2 ?
I don't think i will be using the THD+N Adjust Circuitry and the negative supply on the digital side.
Waiting patiently for the AD1865 core board, save the trouble of making 1 myself. Thanks...
I see the inclusion of the THD+N Adjust Circuitry and also the negative supply for digital, possible to have some kind of a jumper to bypass these 2 ?
I don't think i will be using the THD+N Adjust Circuitry and the negative supply on the digital side.
Core Board
I was suggesting in order to keep the size(cost) of the core boards small allow balanced/dual-mono possibility, 4 DACs on one board, only for small packaged DACs, while for large mono DACs use 2 DACs per board.
If balanced configuration is wanted with these large mono DACs then use two DAC boards (stacked) and U-FL connectors to connect with I2S-PCM board.
For dual-mono configuration with these large mono DACs a small modification of the I2S-PCM board would be needed: image shows how dvb project customized it for his dual-mono two DAC board setup.
Well, my former post is not too understandable
I was suggesting in order to keep the size(cost) of the core boards small allow balanced/dual-mono possibility, 4 DACs on one board, only for small packaged DACs, while for large mono DACs use 2 DACs per board.
If balanced configuration is wanted with these large mono DACs then use two DAC boards (stacked) and U-FL connectors to connect with I2S-PCM board.
For dual-mono configuration with these large mono DACs a small modification of the I2S-PCM board would be needed: image shows how dvb project customized it for his dual-mono two DAC board setup.
AD1865
Power supply connector will be standard for all DAC boards - will be explained how to use it when we decide which to use.
I prefer noizas suggestion more and more: [-15,-12,-5,GND][GND,5,12,15]
THD+N circuitry will be optional, simply not solder the components if you don't need it.
Power supply connector will be standard for all DAC boards - will be explained how to use it when we decide which to use.
I prefer noizas suggestion more and more: [-15,-12,-5,GND][GND,5,12,15]Core Board
Your idea is very clear and it is ok; as I wrote earlier - we need to be realistic with sizes.
I just hope two sets of TDA1541 will fit in 80x70mm board. Can you say which software you used for AD1865 core board schematic?
Possibly I would try to do the same for TDA1541.
Thanks
Saulius
Well, my former post is not too understandable
I was suggesting in order to keep the size(cost) of the core boards small allow balanced/dual-mono possibility, 4 DACs on one board, only for small packaged DACs, while for large mono DACs use 2 DACs per board.
If balanced configuration is wanted with these large mono DACs then use two DAC boards (stacked) and U-FL connectors to connect with I2S-PCM board.
For dual-mono configuration with these large mono DACs a small modification of the I2S-PCM board would be needed: image shows how dvb project customized it for his dual-mono two DAC board setup.
Your idea is very clear and it is ok; as I wrote earlier - we need to be realistic with sizes.
I just hope two sets of TDA1541 will fit in 80x70mm board. Can you say which software you used for AD1865 core board schematic?
Possibly I would try to do the same for TDA1541.
Thanks
Saulius
I think we shouldn't leave possibility to use separate analog and digital power supplies because of TI/BB recommendation.Most of DACs works with +/-5V and not every one is TI/BB and some may need separate power to achieve top performance. I think there is also reason why TI/BB use separate pins for analog and digital power.
I see some inconsistency in [-15,-12,-5,GND][GND,5,12,15]. The +15V is useless because TDA1541A use +5 -5 and -15V only.
If this is relly nessesary to minimize number of power pins (I think it is not) I suggest to use bonded -15 and -12V and use separate analog and digital pairs of +/-5V and +/-12V to allow most DACs be implemented in high end fasion.
I'm not sure if we need separate GNDs because as far as I remember it should be connected as close as possible to DAC chips.
So summing up I suggest [-12d, -12(-15)a, -5d, -5a] GND [5a, 5d, 12a, 12d]
or if we want even pin numbr [-12d, -12(-15)a, -5d, -5a] GNDa GNDd [5a, 5d, 12a, 12d]
BTW what kind of connector do you think about?
I see some inconsistency in [-15,-12,-5,GND][GND,5,12,15]. The +15V is useless because TDA1541A use +5 -5 and -15V only.
If this is relly nessesary to minimize number of power pins (I think it is not) I suggest to use bonded -15 and -12V and use separate analog and digital pairs of +/-5V and +/-12V to allow most DACs be implemented in high end fasion.
I'm not sure if we need separate GNDs because as far as I remember it should be connected as close as possible to DAC chips.
So summing up I suggest [-12d, -12(-15)a, -5d, -5a] GND [5a, 5d, 12a, 12d]
or if we want even pin numbr [-12d, -12(-15)a, -5d, -5a] GNDa GNDd [5a, 5d, 12a, 12d]
BTW what kind of connector do you think about?
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