What LED did you use? I measured a few yellows and greens that I had, all 1.95-2V so pretty hard to get 3.8V from those..
Yep, ~5V & ~470ohm, so should be ~6mA. Those are really cheap 3mm yellows also, maybe I will find the lowest ones..
Is those R30-R33 needed in the I/V stage?
hi all,
as I have started to build, questions arise naturally...well, here is the first one, and maybe its already answered in the depths of this thread.
Its about the 33r resistors for the low voltage salas shunt, do they really have this value? I remember vaguely that there was a change, but I could be wrong also. Ernst ordered for these 3 places ( R1,7,13) 22R, but according to Andreas list its two 33 and one 27R, in Quanghao's list its two 33 and one 8-10 ohm..
So what comes in finally?
And I'm planning to use the HV Shunt as well, has anyone experiences with this? For example, how to set it up with a 250V transformer?
And, finally, is it enough cooling for those fets when they are bolted at the bottom of a steel enclosure ?
Thanks alot, also for the very helpful pics and posts of the lucky ones, who have finished the whole thing already.
Juergen
as I have started to build, questions arise naturally...well, here is the first one, and maybe its already answered in the depths of this thread.
Its about the 33r resistors for the low voltage salas shunt, do they really have this value? I remember vaguely that there was a change, but I could be wrong also. Ernst ordered for these 3 places ( R1,7,13) 22R, but according to Andreas list its two 33 and one 27R, in Quanghao's list its two 33 and one 8-10 ohm..
So what comes in finally?
And I'm planning to use the HV Shunt as well, has anyone experiences with this? For example, how to set it up with a 250V transformer?
And, finally, is it enough cooling for those fets when they are bolted at the bottom of a steel enclosure ?
Thanks alot, also for the very helpful pics and posts of the lucky ones, who have finished the whole thing already.
Juergen
for the analogue ps sections 33ohm should be fine, although i would use 27r and heatsinks on the fets.
for the 5v dig i settled on 11r. Too high resistance will mean the reg will drop out and you wont be able to adjust the voltage enough to give the tl431 enough headroom (you want to dial in 5.3v at least, 5.6 max, 5.5v optimum)
Best check is to ensure vgs on the second fet is not 0, if it is then no shunt current is flowing and poor regulation.
HV shunt you are on your own until completed builds come out.
Steel is not a fantastic conductor of heat, but you may get away with it. The heater reg gets very hot, and do heatsink the diode bridge. Its the hottest part on the build.
for the 5v dig i settled on 11r. Too high resistance will mean the reg will drop out and you wont be able to adjust the voltage enough to give the tl431 enough headroom (you want to dial in 5.3v at least, 5.6 max, 5.5v optimum)
Best check is to ensure vgs on the second fet is not 0, if it is then no shunt current is flowing and poor regulation.
HV shunt you are on your own until completed builds come out.
Steel is not a fantastic conductor of heat, but you may get away with it. The heater reg gets very hot, and do heatsink the diode bridge. Its the hottest part on the build.
What will be the differences between the 2 and the original?
I have the set of original boards but not built. I was waiting to see what errors / mods were before I started. Now that I see you doing a "2" version, I'd like to know what the differences will be. I only want to build one DAC, so if the "2" version is better, I will do that instead of the originals, and sell them.
Jeff Davison
I have the set of original boards but not built. I was waiting to see what errors / mods were before I started. Now that I see you doing a "2" version, I'd like to know what the differences will be. I only want to build one DAC, so if the "2" version is better, I will do that instead of the originals, and sell them.
Jeff Davison
you can se in this link:
http://www.diyaudio.com/forums/digital-source/111259-ad1865-best-dac-17.html
I completely agree with this. Also use Adam's LED bias suggestion. Very nice sound !!!!
I have also continued to use Welborne's PS10 for HV. Just keep coming back to it. Tubes are E182CCs. Need to try the 5687. I have some NOS TungSols and Raytheons from the 60s.
My next experiment may be running input directly to the 8414 (no transformer) Some say it lifts a veil.
This DAC is a keeper and will be one I keep in my system
Best
Bob
I got the mine playing tonight ! Very impressed by the sound.
Now it is configured with no modifications. I have a second I/V board that I plan to use to try leds and ccs.
Andrea, I would love to hear a comparison between various I/V you tried.
1) Transformers (I could not understand what input and output impedance your transformer have)
2) Quancho ver.1
3) Quancho + led and CCS
CCS has also the advantage that will allow for a lower B+.
I have around 5.3 V on the input of the DAC. Is that enought ? I cannot raise it more.
Good project !! I like all these little modules to play around.
Davide
Now it is configured with no modifications. I have a second I/V board that I plan to use to try leds and ccs.
Andrea, I would love to hear a comparison between various I/V you tried.
1) Transformers (I could not understand what input and output impedance your transformer have)
2) Quancho ver.1
3) Quancho + led and CCS
CCS has also the advantage that will allow for a lower B+.
I have around 5.3 V on the input of the DAC. Is that enought ? I cannot raise it more.
Good project !! I like all these little modules to play around.
Davide
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