Current Control Diode versus JFET
Internally, a current control diode is a JFET with the gate and source tied together. It should sound the same as an adjustable single JFET circuit. The current control diode seems difficult to implement with precisely 400ua current. It comes in 100ua, 300ua, and 500ua values varying as much as plus or minus 40%. Good luck finding singles or combinations that get close to 400ua. A lot of testing throw-aways at over $2usd each.
Internally, a current control diode is a JFET with the gate and source tied together. It should sound the same as an adjustable single JFET circuit. The current control diode seems difficult to implement with precisely 400ua current. It comes in 100ua, 300ua, and 500ua values varying as much as plus or minus 40%. Good luck finding singles or combinations that get close to 400ua. A lot of testing throw-aways at over $2usd each.
Just tried to power the DAC from a square 9v battery and no music, I'll see if I can pick up a 12v battery tomorrow
In my dac..i have not connected the rca to earth....but from minus on the powersupply i connect to star earth,,,both powersupply have connection to star earth..
do not connect anything to ground on dac output..(just pos and neg to cinemag trafo)
in this way i solved my hum problem to my tube pre
best Bjarne
do not connect anything to ground on dac output..(just pos and neg to cinemag trafo)
in this way i solved my hum problem to my tube pre
best Bjarne
You may be onto something here, I know what star earthing is. But how would that apply to the dddac ? I don't suppose you have a picture do you ?
I've got a couple each of 100ua and 300ua coming this week
I'll let you know how they measure
Sovereign--
it is not so hard to do
normally i will make one connection near the input rca,,(in the cabinet)
connect one wire from minus on the 12v dac supply
same from the 5v dac supply (the supply to usb bord)
remember to connect the cinemag correct
if this not remove the hum ---try to connect a wire from rca input ground,,to the star point (one from left and one from right)
just one wire from the different point
one thing more...be carefully not to play loud when you try the connection....some time it hum very bad
i am not so good to paste picture in this forum...hope you understand how to do it
it is not so hard to do
normally i will make one connection near the input rca,,(in the cabinet)
connect one wire from minus on the 12v dac supply
same from the 5v dac supply (the supply to usb bord)
remember to connect the cinemag correct
if this not remove the hum ---try to connect a wire from rca input ground,,to the star point (one from left and one from right)
just one wire from the different point
one thing more...be carefully not to play loud when you try the connection....some time it hum very bad
i am not so good to paste picture in this forum...hope you understand how to do it
Hi Doede,
Please see photos of a more complete DAC board. I have resisters at I2S input under PCB. Please note analog side of DAC will be wiring direct to PS while digital will under going a voltage drop resister to approx 8V output into mainboard and 3.3V shunt regs. Idea was adopted from Supersurfer!
Please kindly advise if any abnormally spotted!
Many thanks!
Chanh
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Hey Chanh,
Prolly advise a bit of teflon or a dab of hot glue on the green resistor that runs around the can of the cap, they can be live when energized as the sleeve is an insulant. Just to make sure they don't touch.
I haven't seen anything else but I haven't a board to play with!
Thanks,
Drew.
Prolly advise a bit of teflon or a dab of hot glue on the green resistor that runs around the can of the cap, they can be live when energized as the sleeve is an insulant. Just to make sure they don't touch.
I haven't seen anything else but I haven't a board to play with!
Thanks,
Drew.
Chanh, Starting to look very good & no doubt will sound amazing too.
One comment I have is that, caps are best used going from large ->..-> small, not small -> large -> small. But it's probably not that big a deal.
... and once there is a ccs option you might want to turn the 100uf Silmic outwards to creat some space at the 6k spot..
One comment I have is that, caps are best used going from large ->..-> small, not small -> large -> small. But it's probably not that big a deal.
... and once there is a ccs option you might want to turn the 100uf Silmic outwards to creat some space at the 6k spot..
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Thanks Stijn!
The current layout added 220uf Elna based on your larger cap recommendation!
I could not see an alternative real estate for it, hence current position seems ideal.
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The place seems good for the connections, but for that middle 220uf silmic cap, you could flip it around so that it hangs off the board like the 8v regs do instead of covering the 6k current reference resistorThanks Stijn!
The current layout added 220uf Elna based on your larger cap recommendation!
Thanks Stijn!
The current layout added 220uf Elna based on your larger cap recommendation!
Hi Chanh, I put a 100uf there, I never recommended you to put the 220uf there, but you knew that right?
Not really!Hi Chanh, I put a 100uf there, I never recommended you to put the 220uf there, but you knew that right?
What is wrong with 220uf being there?
Not really!
What is wrong with 220uf being there?
As I wrote:
"One comment I have is that, caps are best used going from large ->..-> small, not small -> large -> small. But it's probably not that big a deal."
I put the 220uf at the C1-C4 & C7-C10, and that's where I would suggest you put it ( I never suggested anything else), and put something smaller in the C5/C11 position..(but not smaller then 47uf..)
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the proof will be in the eating of course.....
With the reserve of potentially too high a Vgs(off) - which is in the detriment of the CCS performance - I like all three options you've found - first two, long-gate JFETs, the third an RF duty JFET.
Some e101 and e301 diodes arrived today.
I was looking at the datasheet and I wonder if the reason they quote such a wide variation of current is in order to cover a full range of voltages and temperatures. I'd also imagine that the surface mount versions are more susceptible to getting hot than the wire mounted ones which can get a bit of air around them
I hope that with a reasonably stable voltage and normal temperatures there won't be that much variation.
I'll have a play and get them measured shortly...
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I was looking at the datasheet and I wonder if the reason they quote such a wide variation of current is in order to cover a full range of voltages and temperatures. I'd also imagine that the surface mount versions are more susceptible to getting hot than the wire mounted ones which can get a bit of air around them
An externally hosted image should be here but it was not working when we last tested it.
I hope that with a reasonably stable voltage and normal temperatures there won't be that much variation.
I'll have a play and get them measured shortly...