Agree it depends who is doing the 'testing'. As I recall the tests I saw were done by a supposedly independent person.......
I'm not saying that LiFePO4 can't become a very good psu for the DDDac. Good implementation would mean:
-a better trickle charge solution then the cheapo always connected one used in the Ciunas to remove all possibility of noise from this source
-decoupling between the digital and analogue power supplies of the Dac which is easy to do on DDDac or, better still, separate batteries for each
Whether all of that done properly would be better than a big traffo, decent caps and Tents /Bellesons
I stopped developing the Ciunas /Dac32 versions because you are always limited by the on chip opamp of limited ability, and inability to take out digital filtering.
David
Thx carlsor, it seems that it's almost no end of what upgrades a man can do with this dac. Must say I am a little bit confused. Have been reading a lot of pages about doedes nos dac, and the tips on how to make it sounding better are so many that I wonder how bad it must sound in the first place. Don't get me wrong, have done some twaks in my Buffalo, but not as half so much tweaking as with the ddac. Maybe the ddac is more flexible ?
I want to try ddac out, but not shure what to go for. 1 deck, 4 deck, 8 deck,,,transformer or no transformer, caps, no caps,,,
The target is as always to get the best sound possible.
Hi,
I would strongly repeat that the DDDac sounds great as standard with one deck. While Nige differs in opinion, my friend and I both consider it very superior to the Ciunas dac we both had, and light years ahead of my Arcam R Dac.
Anything you do to improve it just adds to the performance. I started with two decks then moved to four but if I was doing it again I would:
-start with one Board
-build with OSCONS on the digital psu side, Elna Simics or Black gates on the analogue side
-go straight to Belleson regs on the digital side and Tent on the anologue
-build unregulated hi capcity psus to supply those regs
-use Audio Note tantalum load resistors
But that's just my take on it YMMV. It's just so much easier /cheaper optimising one deck rather than more
David
great work, Ross. Could you explain in a bit more detail what you are saying above? I think I understand that you were only able to reach the 400uA conditions with the 2SK246 on your breadboard by biasing the CCS at 3.1V. How do you then see this workable under the actual conditions of pin 20 (2.4V)? I'm sure you have a plan, but I don't see indications of it in your post.
I also assume, given the conundrum above, that you didn't yet get the 2SK246 on pin 20 and listened to it.
Top work Ross!
@SmoothDancer, don't worry, this dddac sounds very good in it's standard form. If you want to tweak it, you can make some nice improvements without a lot of work/time/money . It's a wonderful playground for development
Hi James and thx for your thoughts. No doubt that the ddac is good, and I know that it can be better with some tweaking. Have done the same with my Buffalo.
More about the 2SK246
I bought 10 of the 2SK246GR Toshiba JFETs. The Idss at 9V varied from 4.1 to 4.6ma. The Vds to get 0.4ma varied from 1.65 to 1.87 volts with 7 of them being above 1.8 volts. This leaves vary little Vds voltage drop across the JFETS for regulation. I was hoping for a Vds of 1.2 volts which would leave 1.2 volts for regulation across Vds.
One scope display for a 1.85 Vds 2SK246 shows a significant variation in current from a 0.1V square wave imposed on the 2.45 Volts to the JFET. When I raised the signal voltage to get 1.2 volts across the 2SK246 I got excellent regulation. If we could get some 2SK246s with an Idss<= 3ma then I think we will have a CCS choice that may sound even better than the 2SK170 with very stable current in a warm stack of DACs.
No I haven't listened to these yet. I am going to try to obtain more of these with a lower Idss. Meanwhile I will build a cascoded version of the 2SK246 and connect to the -12 Volts of the buffer just to see what happens - and how it sounds.
I bought 10 of the 2SK246GR Toshiba JFETs. The Idss at 9V varied from 4.1 to 4.6ma. The Vds to get 0.4ma varied from 1.65 to 1.87 volts with 7 of them being above 1.8 volts. This leaves vary little Vds voltage drop across the JFETS for regulation. I was hoping for a Vds of 1.2 volts which would leave 1.2 volts for regulation across Vds.
One scope display for a 1.85 Vds 2SK246 shows a significant variation in current from a 0.1V square wave imposed on the 2.45 Volts to the JFET. When I raised the signal voltage to get 1.2 volts across the 2SK246 I got excellent regulation. If we could get some 2SK246s with an Idss<= 3ma then I think we will have a CCS choice that may sound even better than the 2SK170 with very stable current in a warm stack of DACs.
No I haven't listened to these yet. I am going to try to obtain more of these with a lower Idss. Meanwhile I will build a cascoded version of the 2SK246 and connect to the -12 Volts of the buffer just to see what happens - and how it sounds.
Thx David. Very useful info.
I have tried the Silmics in my Buffalo on the psu's, and they sounded dull. The bass got boomy, not a succes for me.
But the Elna cerafine is another cup of tea. You know what they been called ?
"Black gates light". In the Buffalo they do a great job. Very detailed, tight and snappy bass.
I think the answer is either the 2SK246Y, which is a selection group having IDSS comprised between 1.2 and 3.0mA, or the 2SK208.
The 2SK208 is a SOT23 JFET apparently based on the same die used for the 2SK246. The main difference between the two devices are the IDSS selection groups that for the 2SK208 are concentrated around lower values. For this application, looking for 0.4mA with low VGS, the 2SK208-O should be the right choice.
With its IDSS comprised between 0.6 and 1.4mA, the VGSoff should be comprised between 0.75 and 1.3V (approximate values taken from the graph showing the relation between IDSS and VGSoff)
I see I was not as clear as I intended t be on implementing nige2000's power supply.
As instructed by him I will use a separate battery/series of batteries for both the 3.3 and 8 volts supply for each DAC and a battery for the delay supply. There will be complete decoupling from each side of the DAC and each DAC.
I had not intended to use decoupling caps after the batteries and am not sure if he is using them. One can always add them later and hear what happens.
I figure the delay battery can be turned on first and then using a DP switch for powering both sides of the DAC simultaneously. Each channel can be turned on separately. You would need a 4P switch to turn them both on at once which would not be important to me and would require a whole lot more wire. I will attempt to have the batteries as close to the boards as possible. I see the switch leads and their respective ground lead attached where the PP decoupling caps would be mounted and then keep the batteries as close to the switch as possible while still allowing one to use the switch!
nige2000 was initially using the inexpensive power supplies to power his computer setup. He says, and I believe him, that as long as it wasn't a "switcher" being used as a charger he could not hear anything untoward with the charger attached. He then went further and said he hears no difference with the charger disconnected.
For the DAC supply I will use the BELLESON regs I have removed to be the battery chargers. Since the draw on the batteries will be small I figure these miniature regs will not have any problem keeping up. This will also allow me to disregard whether the charger is sending garbage into the circuit. I will try a small value resistor at the output of the DAC to add a but more isolation. nige2000 thinks this is unneeded and he speaks from real experience but some of us cannot be satisfied with that!
The trick with these batteries is that their low ESR continues to be low much higher in frequency than any reg I am familiar with. I know the BELLESONs's published ESR is a tad lower at the lowest frequencies but the A123s remain level where all regs eventually start to exhibit a rise. I think it is very important for this to be linear - some think a flat ESR is more important than the absolute lowest possible ESR that can only be maintained at the lowest frequencies almost always derived by negative feedback which I tend to think is an illusion of low impedance. Can feedback keep up with a dynamic circuit? No.
When everything is considered this is the best compromise. Not trying to say it is perfect since that is not a possibility but it does more things right than any other alternative.
I have used batteries in the past, big lead acid ones for various duties, and know they can do some things well but one does get tired of their shortcomings; the re-charging especially. But that is eliminated with this and of course to have an eight volts supply would be impossible without this scheme.
I suspect the most difficult part will be finding someone to resistance weld the tabs. Some say you can solder them but I would rather not unless there is no other choice.
Calling around to battery shops yesterday I was told that the best place to ask were computer repair shops. Hoping I can find someone today willing to do this.
As instructed by him I will use a separate battery/series of batteries for both the 3.3 and 8 volts supply for each DAC and a battery for the delay supply. There will be complete decoupling from each side of the DAC and each DAC.
I had not intended to use decoupling caps after the batteries and am not sure if he is using them. One can always add them later and hear what happens.
I figure the delay battery can be turned on first and then using a DP switch for powering both sides of the DAC simultaneously. Each channel can be turned on separately. You would need a 4P switch to turn them both on at once which would not be important to me and would require a whole lot more wire. I will attempt to have the batteries as close to the boards as possible. I see the switch leads and their respective ground lead attached where the PP decoupling caps would be mounted and then keep the batteries as close to the switch as possible while still allowing one to use the switch!
nige2000 was initially using the inexpensive power supplies to power his computer setup. He says, and I believe him, that as long as it wasn't a "switcher" being used as a charger he could not hear anything untoward with the charger attached. He then went further and said he hears no difference with the charger disconnected.
For the DAC supply I will use the BELLESON regs I have removed to be the battery chargers. Since the draw on the batteries will be small I figure these miniature regs will not have any problem keeping up. This will also allow me to disregard whether the charger is sending garbage into the circuit. I will try a small value resistor at the output of the DAC to add a but more isolation. nige2000 thinks this is unneeded and he speaks from real experience but some of us cannot be satisfied with that!
The trick with these batteries is that their low ESR continues to be low much higher in frequency than any reg I am familiar with. I know the BELLESONs's published ESR is a tad lower at the lowest frequencies but the A123s remain level where all regs eventually start to exhibit a rise. I think it is very important for this to be linear - some think a flat ESR is more important than the absolute lowest possible ESR that can only be maintained at the lowest frequencies almost always derived by negative feedback which I tend to think is an illusion of low impedance. Can feedback keep up with a dynamic circuit? No.
When everything is considered this is the best compromise. Not trying to say it is perfect since that is not a possibility but it does more things right than any other alternative.
I have used batteries in the past, big lead acid ones for various duties, and know they can do some things well but one does get tired of their shortcomings; the re-charging especially. But that is eliminated with this and of course to have an eight volts supply would be impossible without this scheme.
I suspect the most difficult part will be finding someone to resistance weld the tabs. Some say you can solder them but I would rather not unless there is no other choice.
Calling around to battery shops yesterday I was told that the best place to ask were computer repair shops. Hoping I can find someone today willing to do this.
That sounds like a great plan and using super regs like Bellesons to charge should rule out most possible noise input. The Ciunas /Dac32 dacs use LIFePO4 batteries with pre welded solder tabs so you should be able to get these somehwere. When I was looking they were available in the US and Germany but not UK!
David
Hi, Rick
Here you can order original batteries with tabs: http://www.batteryspace.com/a123-sy...o4-26650-rechargeable-cell-3.2v-2500-mah.aspx
Ed
I have a German adress too....
Here you can order original batteries with tabs: http://www.batteryspace.com/a123-sy...o4-26650-rechargeable-cell-3.2v-2500-mah.aspx
Ed
I have a German adress too....
dwjames,
Do you know where you got these? The link does not show anything like these and I have not been able to find anything like them.
They do seem superior to what I am seeing.
Thanks,
I had seen those but I am sure you noticed my Scots surname and should feel safe to assume I am as cheap (thrifty is the euphemism) as any Scot in Scotland. This "virtue" is what brought me to DIY audio where all of the money I have saved over the years is spread throughout the house in numerous boxes of parts no longer needed.
That is quite a high price to pay for tabs! Almost twice as much as the place I have ordered from (a little under eighteen dollars a piece versus nine).
Nonetheless, thanks.
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