Some basic questions.
Hello folks. Having bought one of these DACs and knowing virtually nothing about DIY Hi-Fi I've been reading through this thread with great interest and an increasing awareness of what a fascinating and rewarding hobby this can be. Many thanks to all the contributors for helping to educate a no-nothing like myself.
Having assembled one kit into an enclosure, added different RCA sockets & fitted better op-amps, I decided to order a second kit and fit a pair of the ubiquitous UTC A-20 transformers, which are currently en-route from China.
I note on some recent posts that the connections from the DAC to the transformers have been taken directly from the top surface of the DAC board, rather than from where the four capacitors in front of this board were previously fitted. This seems a simpler option as well as yielding sound benefits so it's what I intend to do.
First question - do I still need to remove these four capacitors? Secondly - these connections are to pins 19, 20, 23 & 24 which all appear to be on the right-hand side (looking from the direction of the four capacitors) but am I right in assuming they're the 5th- 6th, & 9th- 10th solder-blobs down from the top right?
On this second DAC I would like to add an LED "Power" indicator but I'm unsure about where this can be added to the board, so advice would be appreciated. And what type/power would be suitable?
I would also like to fit an external selector switch to toggle between optical and co-ax inputs (I'm not interested in the USB input at the moment) and I'm contemplating soldering wires to the relevant pins on the small jumper on the front edge of the main board & connecting them to a DPDT switch. I'm just a bit nervous about using this switch when the DAC's powered up. Will this arrangement cause any problems please?
Any and all help will be gratefully received!
Hello folks. Having bought one of these DACs and knowing virtually nothing about DIY Hi-Fi I've been reading through this thread with great interest and an increasing awareness of what a fascinating and rewarding hobby this can be. Many thanks to all the contributors for helping to educate a no-nothing like myself.
Having assembled one kit into an enclosure, added different RCA sockets & fitted better op-amps, I decided to order a second kit and fit a pair of the ubiquitous UTC A-20 transformers, which are currently en-route from China.
I note on some recent posts that the connections from the DAC to the transformers have been taken directly from the top surface of the DAC board, rather than from where the four capacitors in front of this board were previously fitted. This seems a simpler option as well as yielding sound benefits so it's what I intend to do.
First question - do I still need to remove these four capacitors? Secondly - these connections are to pins 19, 20, 23 & 24 which all appear to be on the right-hand side (looking from the direction of the four capacitors) but am I right in assuming they're the 5th- 6th, & 9th- 10th solder-blobs down from the top right?
On this second DAC I would like to add an LED "Power" indicator but I'm unsure about where this can be added to the board, so advice would be appreciated. And what type/power would be suitable?
I would also like to fit an external selector switch to toggle between optical and co-ax inputs (I'm not interested in the USB input at the moment) and I'm contemplating soldering wires to the relevant pins on the small jumper on the front edge of the main board & connecting them to a DPDT switch. I'm just a bit nervous about using this switch when the DAC's powered up. Will this arrangement cause any problems please?
Any and all help will be gratefully received!
No problem switching inputs when powered up, and all you need is a SPDT switch. You are only changing one jumper position.
You can hook up an led to an existing one or anywhere you like.
Removing the caps has been very troublesome for many. An easier option is pulling the end of the resistor that connects to them, or just clipping the end.
Best, Bill
You can hook up an led to an existing one or anywhere you like.
Removing the caps has been very troublesome for many. An easier option is pulling the end of the resistor that connects to them, or just clipping the end.
Best, Bill
An externally hosted image should be here but it was not working when we last tested it.
run a signal wire ontp of the dac chip, starting from the solder blob to be exact....
look at the pic here to help you identify the right pin...
There's pair of AOUTA and AOUTB. Either one can be left or right. + is for signal and - for grounding. Connect it with a signal wire to the primary of each A-20 if you choose transformer output route. Don't forget hi pass - lo pass filter circuit for the A-20 at primary and secondary....
make sure you align you dac based on the notch on the chip....
Regrading those tiny green caps I think you can leave it as we by pass the on board opamp I/V....
I prefer the last option...remove the regulator and use the input & output holes for the new regulator...but I think those 2 resistors need to be remove since it's in the output line....
By ImageHousing.com
I am totally new to audio DIY, but the depth of discussion in this thread and the abundance of helpful commenters encouraged me to give it a shot with this DAC. I have three STRs (just the boards, I will need to assemble them) on their way and I removed the LM317 regulators from the board. I had a couple of questions about what will be next.
1. I have not yet removed the two resistors. I just wanted to confirm that they are the two parallel resistors closer to the stock 9v input on the board. Is that right?
2. I am little confused about how exactly to wire in the STR. Because the STR does not have a rectifier, I am thinking that the input (+) on the STR should go to the hole on the board where the input pin on the 317 was connected and the output (+) on the STR should go to the hole on the board where the output pin on the 317 was connected. I am assuming that the output (-) on the STR would go to where Ryssen connected the black wire (i.e. negative on the big e-lyt). Where should the input (-) on the STR come from? Should I pull it from the soldering points directly to the right of the green dots on Ryssen picture from post 2408? Will I need to cut any trace doing it this way?
I have also removed the four green output caps and plan to get output transformers soon. Last, I am working on populating a tube output stage PCB. Probably bit off too much for a first project, but I am already neck deep so I guess I will have to learn to swim. One thing at a time I guess...
Thanks for all your help in advance.
Hello! Has anyone compared the sound between this DAC with transformers output and TDA1541A with tube output? Now I have the DAC TDA1541A with SRPP tube output without any filters and this DAC. I just changed the opamps to AD823 in it. But the difference is dramatic. Sound TDA1541 is alive, beautiful, close to analog. CS4398 is bright but dead, very digitally. Is this difference between the chips of DACs or the difference between the outputs-tubes and opamps?
The STR has three connection points just like the LM317 they are replacing
STR Vin - LM317 input
STR Vout - LM317 output
STR Gnd - LM317 adjust
LM317 datasheet here:
http://www.st.com/stonline/products/literature/ds/2154/lm317.pdf
So it should be possible to drop the STR into the vacant holes left by the LM317's. I'm pretty sure the rest of the on board regulator components should be removed in this case.
The STR's should be set to 5V using the adjustable trimmer and a multimeter before inserting into the circuit. 9V supply will give plenty of voltage dropout required for this.
Thanks Rich. The STR schematic makes it look like there are 4 connection points. http://www.teddypardo.com/Images/SuperTeddyReg3.png Did you get your STRs yet?
What two points will I measure the voltage? I know that i will want to use the output, but where should my negative lead go? The adjust? The negative on the big e-lyt after the regulator?
Also, just to confirm, the resistors are the only other components of the regulation stage on the board, right?
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I have brand new unused Edcor XSM 10k/10k for sale. Took so long for them to ship, I bought Altecs instead. I'm selling them for what I paid for them, $35 shipped US - but at least you won't have to wait 5 million years for them to show up, like I did...
Funny. I just called and got an 8 week lead time on some XSM 600/600s.
Will the 10k version work? I thought we needed the 600 ohm version.Funny. I just called and got an 8 week lead time on some XSM 600/600s.
Both are OK but 10K is in fact better suited for this DAC. You can use the same low pass filter on primaries you just need to change the R/C values on secondaries to 13K/620pf(or something similar)
I still have one STR left from a previous order and still waiting for two more to arrive.
The new Version 1.3 boards have only 3 connection points. The previous boards had 4, 2 of which shared the same Gnd track so were basically the same connection. I think Teddy simplified the connection scheme to make thing easier to understand.
Measure the voltage out from Vout and any point on the Gnd track. When you see the boards you will understand.
Out of interest what capacitor did you order for C3?
I ended up getting it from Teddy. Expensive, but not any more than I would have paid for a nice 22uf/35v tantalum from Mouser.
Excellent. The Vishay tantalum is supposed to be the very best choice for this position. In an audio circuit application this capacitor has the most influence on sound but in our case it's more speed and signal noise quality that's important I think. I am trying an SMD tantalum cap for C3 as an experiment.
I prefer the last option...remove the regulator and use the input & output holes for the new regulator...but I think those 2 resistors need to be remove since it's in the output line....
Would this work?
Remove R1 and jumper R2, then hook up the STR outputs to input, output, and adjust as Rich suggested above? I think you could use a continuity test once the resistors are out to identify which was R2.
Just had this advice from Teddy regarding replacing the 317 regulator
"You will have to remove the resistor network of the LM317 as well as the capacitors if exist:
- If you want to use the adj pin, you’ll have to replace the resistor that goes between the adj pin ant the ground with a link, otherwise connect the gnd pin of the STR directly to the ground (better).
- If there is a capacitor (usually electrolytic or Tantalum) in parallel with this resistor it has to be removed.
- If there is a capacitor (usually electrolytic or Tantalum) at the output of the LM317, either remove it or even better, replace it with a 0.1uF film capacitor (in this case you can ignore C6 of the STR)."
"You will have to remove the resistor network of the LM317 as well as the capacitors if exist:
- If you want to use the adj pin, you’ll have to replace the resistor that goes between the adj pin ant the ground with a link, otherwise connect the gnd pin of the STR directly to the ground (better).
- If there is a capacitor (usually electrolytic or Tantalum) in parallel with this resistor it has to be removed.
- If there is a capacitor (usually electrolytic or Tantalum) at the output of the LM317, either remove it or even better, replace it with a 0.1uF film capacitor (in this case you can ignore C6 of the STR)."