Watch the dissapation, if you use the old b+ those little heatsinks will melt (I exaggerate... but the fets will die).
and did you test the css, its almost impossible to set the current by maths, the tolerances are pretty big.
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Fredlock,
I bought the TL431 at a local store, but they are marker timexico TL431C
Adamus,
Actually I already thought to lower the B+, it should be sufficient to leave 10-15 V of headroom to the regulators. I did not measured the plate voltages with the leds yet.
I was also surprise of the results of the setting resistors. I set them empirically with a trimmer and then replace with a fixed resistor. You can see two small resistors between the regulator and the boards. These are 10 ohm 0.1 % and they show exactly 15 mV of drop.
Davide
I bought the TL431 at a local store, but they are marker timexico TL431C
Adamus,
Actually I already thought to lower the B+, it should be sufficient to leave 10-15 V of headroom to the regulators. I did not measured the plate voltages with the leds yet.
I was also surprise of the results of the setting resistors. I set them empirically with a trimmer and then replace with a fixed resistor. You can see two small resistors between the regulator and the boards. These are 10 ohm 0.1 % and they show exactly 15 mV of drop.
Davide
good stuff
to make life easier on the ccs we could also up the plate voltage on the tubes, maybe a sting of 4 leds or a resistor
to make life easier on the ccs we could also up the plate voltage on the tubes, maybe a sting of 4 leds or a resistor
Grounding / Shunt and TL431
Still waitin' for some parts most are already where they should be 🙂
Have been digging this thread a lot this weekend tho figure out mod that make sense. Will try Adamus' LED mod and probably his CCS mod. Andrea recommends 2nd mod in his finished project as well with ready made parts from NYC (if I remember correctly).
Regarding the usage of the TL431 Quanghao posted somewhere at diyAudio that he is planning a total new all in one board using just Salasshunts without any TLs. Should sound superior.
For me this would be slight overkill even it might be a good sounding one. I had a second shuntboard at hand, but I'd go a different, more economic way and hope is will be a almost as good one as well. Lets see what your opinion is about: In my ears most important voltages are the analogues +- 5V for the DAC. Each has a dedicated shunt and subsequently a dedicated TL431. Nothing else is after these two Salasshunts (if I am right - tried to find out this right on the board). For me this means, these two TLs can be disposed in any case without any disadvantage, but only advantage. Of course than it is more important to set the Sshunt voltage to 5V precisely.
All digital 5V are fed by the second positive Sshunt and finally regulated by the TLs. From what I know this should be enough quality for digital supply.
What I will try is to put small SMD caps underneath the board between voltage pins and closest ground instead of dedicated bypass cap location. Have read more than one time that this should help to keep voltage clean.
Regarding ground I saw, somewhere on the center of the board underneath both, analogue and digital ground connected. I am not really happy about the way this is done (mixing up gounds around DAC) and think about changing this in following way: Having just really one defined connection point. This keeps ana and digi ground clean. Question: Is it better on the DAC board done or on the shunt board? Maybe I'm picky 🙄 and maybe I'm wrong 😱
Cheers Ernst
Still waitin' for some parts most are already where they should be 🙂
Have been digging this thread a lot this weekend tho figure out mod that make sense. Will try Adamus' LED mod and probably his CCS mod. Andrea recommends 2nd mod in his finished project as well with ready made parts from NYC (if I remember correctly).
Regarding the usage of the TL431 Quanghao posted somewhere at diyAudio that he is planning a total new all in one board using just Salasshunts without any TLs. Should sound superior.
For me this would be slight overkill even it might be a good sounding one. I had a second shuntboard at hand, but I'd go a different, more economic way and hope is will be a almost as good one as well. Lets see what your opinion is about: In my ears most important voltages are the analogues +- 5V for the DAC. Each has a dedicated shunt and subsequently a dedicated TL431. Nothing else is after these two Salasshunts (if I am right - tried to find out this right on the board). For me this means, these two TLs can be disposed in any case without any disadvantage, but only advantage. Of course than it is more important to set the Sshunt voltage to 5V precisely.
All digital 5V are fed by the second positive Sshunt and finally regulated by the TLs. From what I know this should be enough quality for digital supply.
What I will try is to put small SMD caps underneath the board between voltage pins and closest ground instead of dedicated bypass cap location. Have read more than one time that this should help to keep voltage clean.
Regarding ground I saw, somewhere on the center of the board underneath both, analogue and digital ground connected. I am not really happy about the way this is done (mixing up gounds around DAC) and think about changing this in following way: Having just really one defined connection point. This keeps ana and digi ground clean. Question: Is it better on the DAC board done or on the shunt board? Maybe I'm picky 🙄 and maybe I'm wrong 😱
Cheers Ernst
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Old known reference but still interesting
http://www.tentlabs.com/InfoSupport/page35/files/Supply_decoupling.pdf
Unfortunately things should have been done when routing, now only few minor change can be tried.
But it's diy, there's always room for trying.
What you can try is to separate the AGND and DGND (you will have to cut trace) and tight them together at one point under the AD1865
I Haven't finished yet I don't kwow if it will improve something or not but this approach worked for one tda1541 DAC board i played with.
After playing with the original board for 5 years I'm very interested in this. I was trying to figure this out last night. I believe there will be a good gain if they can be separated. I separated the digital from the analog output by floating the grounds and the result was dramatic.
Dramatic means bad I guess !
As I already "split" the ground with this GB board, I will see. I will have to find here someone using the original PCB as I don't even have a scope.
Ok thx same meaning in french... As i said the result with a 1541A was dramatically good. And i don't have any doubt with this AD DAC chip 😎 Your conclusion helps that way too
If you assembled this dac, could you please tell us all the details of sound. And what version did you assemble? Thanks.
I'd like to assemble, but cannot decide because I'm not sure for the quality of sound.
I have two questions :
1) How important is to keep the connection between the DAC-END and the I/V short ?
Is it possible to put them in two separate chassis ?
2) How to add a toslink input ?
Thanks,
Davide
1) How important is to keep the connection between the DAC-END and the I/V short ?
Is it possible to put them in two separate chassis ?
2) How to add a toslink input ?
Thanks,
Davide
1. Longest I have gone with an i-out DAC is about 7 inches to a tube stage whith shielded cable. Little bit of hiss and I'm sure it would have been quieter with a shorter length. I wouldn't recommend a separate chassis, we are talking about very susceptible signal. I've got a classic DAC that just needs a better analog stage but haven't started on it because I will have to buy a bigger case, considered the two chassis idea but others told me it doesn't work out well.
How big should the heatsinks be for the FET's on the Salas PSU? I have these in my bin, would that be sufficient?
Digi-Key - HS115-ND (Manufacturer - 507302B00000G)
Digi-Key - HS115-ND (Manufacturer - 507302B00000G)
I have a small problem in the protection circuit of the I/V. When the voltage approaches the opening of the relays, I have a strong oscillation, like the relays opening and closing very quickly. This happens only if both the tubes are installed, and only on one I/V (I have two). Now I have a BC550 instead of a BC337 installed (I could not find the right one), but on one board works OK. Is it just a faulty relays ? I hope not, it's a nightmare to unsolder it 🙂. I am not very familiar with this circuit, any hint to stabilize it ?
Thanks,
Davide
Thanks,
Davide
I noticed that if I change the regulator the problem is mitigated, the oscillation last less than one second.
Quanchao, one question: am I right, but the filament supply is not independent for left and right channell.
BR,
Davide
Quanchao, one question: am I right, but the filament supply is not independent for left and right channell.
BR,
Davide
what pcb do you use??
Salas shunt ? or Supply for iv stage???
On PCB IV/satge have cap C12, you can change it for time of relay.
More cap, it is slow stard!
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