A NOS 192/24 DAC with the PCM1794 (and WaveIO USB input)

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#5,442
smooth dancer said:
Simon@

Do not reduce the transformer output. Remove the caps before the first choke, and you then have a true choke input. Sounds better, and your voltage will drop much closer to 12vdc.

What dac boards do you have ? The new ones draw twice the current and if you hook them up to your psu as it is now, you will see a large drop in voltage. With choke input , the voltage drop is only half of cap input psu, but you maintains the same current through.

If you have the old board(s), 19vdc is probably to much, it depends on the number of boards.
Click to expand...

Thanks for the input. I have the new tent boards and using four of them FYI.
 
#5,444
Good, when you hook up to mainboard you will have 1-3v drop, I guess. In other words a bit low, around 9-10v. No problem at all, but a little low. I have 9 v at input dac, and my trafo is 2x15v, so I'm going for a new R-core 2x18v. That will be perfect ( for me). For you maybe 2x15v is enough. Hook up to dac and let us know your numbers Simon.
 
#5,445
smooth dancer said:
Good, when you hook up to mainboard you will have 1-3v drop, I guess. In other words a bit low, around 9-10v. No problem at all, but a little low. I have 9 v at input dac, and my trafo is 2x15v, so I'm going for a new R-core 2x18v. That will be perfect ( for me). For you maybe 2x15v is enough. Hook up to dac and let us know your numbers Simon.
Click to expand...

So with the DAC connected and 100 ohm bleed resistor I have 10.8 v DC out which is a bit low for the 7810 input but the DAC board shunt LEDs are on.

I plan to get R core too so looks like 18v might be needed
 
#5,449
Hello ,
Doede did tell me minimum input for the 7810 is 11,5 volts!!!
With the new boards there is a 4E7 resistor after the 12 volt input just before the 47µF cap that is at the input of the 7810 regulator.
You can get some extra voltage by using schottky diodes!
If you are giving less voltage to 7810 maybe they will also break down in the end and destroy the Tent shunts as well.
You could also change the 4E7 resistor into 1 ohm and gain about 0,4 volts or just get another transformer.
Greetings, Eduard
 
#5,454
Hello Tommy,
Not many people need a 21 volt with a single secondairy. Of courese being r core there are 2 seconairries but they are connected at the transformer underneath the isolation just like the primaries. No more worries about paralleling the wrong wires lol
I hope they will send it quickly. Mine ( the 120VA r core for the wave Io Bellison supply) was quickly within one week but they forget the track and trace link. Somehow being French they never can do it 100% right lol
Greetings, Eduard
@ Simon if you put the 2 coils in series you might as well use them in what Lundahl calls common mode. Total inductance will remain the same but filtering will be improved. Take care how to connect them. Take a look at my pics posted this morning.
 
#5,455
eduard said:
Hello Tommy,
Not many people need a 21 volt with a single secondairy. Of courese being r core there are 2 seconairries but they are connected at the transformer underneath the isolation just like the primaries. No more worries about paralleling the wrong wires lol
I hope they will send it quickly. Mine ( the 120VA r core for the wave Io Bellison supply) was quickly within one week but they forget the track and trace link. Somehow being French they never can do it 100% right lol
Greetings, Eduard
@ Simon if you put the 2 coils in series you might as well use them in what Lundahl calls common mode. Total inductance will remain the same but filtering will be improved. Take care how to connect them. Take a look at my pics posted this morning.
Click to expand...

Yes I plan to use common mode but just tried this method first
 
#5,456
eduard said:
Hello Tommy,
Not many people need a 21 volt with a single secondairy. Of courese being r core there are 2 seconairries but they are connected at the transformer underneath the isolation just like the primaries. No more worries about paralleling the wrong wires lol
I hope they will send it quickly. Mine ( the 120VA r core for the wave Io Bellison supply) was quickly within one week but they forget the track and trace link. Somehow being French they never can do it 100% right lol
Greetings, Eduard
@ Simon if you put the 2 coils in series you might as well use them in what Lundahl calls common mode. Total inductance will remain the same but filtering will be improved. Take care how to connect them. Take a look at my pics posted this morning.
Click to expand...

What r core did you use for the bellison?
 
#5,457
Hello Simon,
120 VA r core 12 volt secondaries in parallel, schottkys, LL2733 1000mH 0,7 A common mode choke input 2*1000µF with 360 ohm bleeder right at the output connectors of the choke and another 1000µFclose to the Belleson input. Gives you around 10,5 volt but that will go down one volt once there is around 0,5A load present when the wave IO has a signal applied.
Greetings, Eduard
 
#5,458
SimonJ said:
Yeap I have sound but agree need more volts for the 7810s

Now time to listen to see if PSU is better 😉
Click to expand...
Are the 7810 supplying the regulators for the 3.3v section? If so, why not just swap them for the +9v 7809 or +8v 7808 instead to give some more room for maneuver.

Edit:.. Hmm, no they aren't. So they sit before the 8v tent shunts. Ignore me...
 
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#5,460
dwjames said:
Lovely work Alex 🙂
I'd be really interested to hear how it compares to my single decker with buffer and reclocker.

Did your new boards soften up in sound at all? I recall that the 2sk208-o for the ccs take some hours before they mellow. I would expect for anyone with the new dac boards that their sound will improve over time to become more relaxing.
Click to expand...

I have found that the sound does improve over time, it was the reason I took so long building it.
After any mods I will leave it alone for about a month and just listen to a load of CD`s.
Some mods did not work as well as others but I made sure I left all alone until it had time to settle down.

As it is so far, it takes about 20 mins playing time for the sound to move out beyond the speakers and fill the depth front to back. My single 16 stacker did the same, but after about 6 weeks I could put the CD in and it was up and running immediately.

Well worth the trouble and gave me a very fast introduction to digital circuit design with a lot of help and donation of buffer IC`s from Doede. I am no expert but I am a lot more comfortable trying various ideas, and I even got some PCB`s made for the buffers 🙂
 
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