A new thread has started regarding this new DAC from Gigaworks:
High Grade 24bit/192khz DAC with fully assembled kits - eBay (item 120551270004 end time May-01-10 02:48:28 PDT)
Looks promising and interestingly includes a Sumlink pulse transformer on input. I wouldn't mind getting just the DAC board and making my own power supply and regulation with STR's.
I really am going to have to give this a go. Surely it wont harm the reciever chip if I try a resistor across the secondary's?
High Grade 24bit/192khz DAC with fully assembled kits - eBay (item 120551270004 end time May-01-10 02:48:28 PDT)
Looks promising and interestingly includes a Sumlink pulse transformer on input. I wouldn't mind getting just the DAC board and making my own power supply and regulation with STR's.
I really am going to have to give this a go. Surely it wont harm the reciever chip if I try a resistor across the secondary's?
Regarding the STR BOM guys, I have been advised the following:
R1+ value is calculated for the led used, to get it into a nice linier part of its range. So for the LED listed in the BOM use 18R for R1+
The 100R value on the BOM was taken from Teddy's site and will work but better to use 18R for that LED.
Sorry for any confusion
Rich
R1+ value is calculated for the led used, to get it into a nice linier part of its range. So for the LED listed in the BOM use 18R for R1+
The 100R value on the BOM was taken from Teddy's site and will work but better to use 18R for that LED.
Sorry for any confusion
Rich
Regarding the pulse trafo arrangement, yes, the trafo wires directly to the 8416 and ground but you still need the 75ohm across the secondaries for correct termination. The .1 or .01 cap goes between the RCA or BNC and the primary to block DC.
The biggest problem I have found is the SPDIF transmission from the source. Most I have checked out on my scope are really crappy, mostly because they were an afterthough on the manufacturer's part. It's really a much bigger can of worms than I thought before I started digging into this. I haven't made many comments about this stuff because some of it still feels like voodoo to me and I don't want to lead anyone astray. Getting it exactly right requires at least a good scope and probably more. Once you have the trafo squared away I urge you to examine your source's SPDIF transmission circuitry, that is where you can easily increase the quality of the listening experience.
I guess that's enough wind from me.
Nice one Bill, I bloody love you!
your comments are always bang on.
Will try that later. need to source a 75 ohm resistor!
Cheers fella
your comments are always bang on.
Will try that later. need to source a 75 ohm resistor!
Cheers fella
Yes Bill you have been conspicuous by your absence but your "wind" is always welcome. I suspect my source needs some looking in to but I'm still trying to figure out how/what to improve. I've seen a few Squeezebox modding threads here and on other forums but I'm not too comfortable with those tiny SMD circuits. But I'll get there eventually.
So has anyone tried getting an unpopulated PCB instead of the kit? with the output transformer mod a lot of the board is unused anyway, so why not start from scratch and have greater control over parts quality and values?
Another thought:
Does Lukaz's GreenDAC seem like a good candidate for transformer output? Again, you can order the bare PCB and cut out the middlemen...
What do you guys think?
Another thought:
Does Lukaz's GreenDAC seem like a good candidate for transformer output? Again, you can order the bare PCB and cut out the middlemen...
What do you guys think?
Bill
Does it means that one leg from secondary goes to pin 4 of CS8416 after 10nF and the other one to ground just like in audiodesignguide.com....???
How about PPL values...??? Are you avoiding it...????
Is there any significant improvement from here?
gabanyayaya, the new method, call it the 'Ryssen mod' is to solder the seconday's of the pulse transformer direct to the reciever chip pins:
One(+ secondary) to RXPO and one(- secondary) to RXN.
CS8416 datasheet, page 12 is where you want to be:
http://www.cirrus.com/en/pubs/proDatasheet/CS8416_F3.pdf
Looks like pins 4 + 5.
I don't think my Sumlink has polarised terminals so a pair of twisted wires straight to the top pins.
The primary's go to the input with a 75 ohm resistor across. It is exactly the same principle as the output transformers, galvanic isolation. So what would happen if you applied the resistor loading principle with a resistor on each leg of the primary's? The input needs to have 75 ohm impedance, would 37 ohm and 0.5 ohm on each provide the required load correctly. Then filter caps across the terminals?
Probably complete rubbish and to be honest as Bill pointed out the attention needs to be on the S/PDIF signal delivery, from source to presumably BNC connnections etc and quality coax cable made correctly. We should probably sort this out before upgrading the regulation really.
@wushuliu - does the TDA1541 have high enough output to drive transformers? they work better with a buffer stage i think. Someone will know this but I think the new generation of DAC chips will drive loads easier. That Greendac looks very good though.
This post is rambling on a bit sorry. I'll leave you with a pic of the inside of my NAC72 with STR's on the end of each gain and filter cards. Stunning preamp. Interestingly the cards on their own can be made into a very effective preamp buffer stage. Fully regulated of course...
[IMG=http://img196.imageshack.us/img196/9990/img1726p.jpg][/IMG]
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It should look just like Fig.16 except 75ohms instead of 110, and coax with the shield connected to the trafo and grounded at the source. You can add a cap from shield to ground at the dac, but it,s not necessary. The Sumlinks have identical windings, you can use them either direction. You should probably attempt to keep the polarities the same.
I changed the PLL parts to the correct values on the datasheet, I think Cirrus probably knows more about it than we do.
The 1541 is current output, they need 18-20/1 trafos. I've seen threads about using trafos with them and the opinions were all over the map. They make trafos expressly for current out dacs. Would be fun trying it.
I changed the PLL parts to the correct values on the datasheet, I think Cirrus probably knows more about it than we do.
The 1541 is current output, they need 18-20/1 trafos. I've seen threads about using trafos with them and the opinions were all over the map. They make trafos expressly for current out dacs. Would be fun trying it.
I've got it hooked up like that(twisted pairs soldered under the 8416) I haven't really had the time to listen that much but for now I can't say if it's any better or worse that the way Ryssen did it(without C&R).
Hi folks - haven't been on this thread for a while as been too busy enjoying music from the Gigaworks + UTC-A20s 🙂
Made an easy to do tweak today which has really improved things - quite taken aback actually. I desoldered the twisted pair of wires from the L-/+ and R-/+ pads, untwisted them, shortened them as much as possible, and soldered them instead directly to the solder pads on the CS4398 DAC board:
Pin19 - R-
Pin20 - R+
Pin23 - L+
Pin24 - L-
Give it a go - really improved the bass in particular, and the 'start/stop' transients/dynamics are quite astonishing on some material now. If you're using output transformers this is a REALLY worthwhile and free tweak!
Enjoy 🙂
- John
Made an easy to do tweak today which has really improved things - quite taken aback actually. I desoldered the twisted pair of wires from the L-/+ and R-/+ pads, untwisted them, shortened them as much as possible, and soldered them instead directly to the solder pads on the CS4398 DAC board:
Pin19 - R-
Pin20 - R+
Pin23 - L+
Pin24 - L-
Give it a go - really improved the bass in particular, and the 'start/stop' transients/dynamics are quite astonishing on some material now. If you're using output transformers this is a REALLY worthwhile and free tweak!
Enjoy 🙂
- John
@ johnm
Been doing that way since the beginning. Had no choice after I destroyed one of the traces while desoldering the coupling caps.
Been doing that way since the beginning. Had no choice after I destroyed one of the traces while desoldering the coupling caps.
It's something I've been meaning to do for at least 6 months now haha! I guess those extra solder points and traces degrade that signal by a surprising amount, in hindsight.
have a Behringer SRC2496 awaiting the output transformer mods, but I'd be very surprised if it bests the Gigaworks.
have a Behringer SRC2496 awaiting the output transformer mods, but I'd be very surprised if it bests the Gigaworks.
Seams to many uncertainty with the pulse transformer mod here.... anyway i'm using the newava transformer mention in early pages of this thread soldered at the empty space on the dac with some 75ohm Canare LV 77s cable. I can't say any improvement since applying this mode since i first got the dac.....
On the top, yes. Makes me wonder how good it would be soldered directly to the chip pins, but this is way too tricky for me I think. Still soldered directly to the DAC chip-boards solder points I'm very happy with the improvement.
Hello John,
were there resistors between the DAC chip and the L/R outputs that you've bypassed?
Cheers,
Dan
As it is a quick mod on one of my breadboard setups, I just tried it with my version of the non sample rate conversion DAC, DIR9001 based:
Indeed, I think it is an improvement in the bass area, I cannot believe it!
Thanks John!
BTW: I am using actually my "subwoofer desk", an open baffle construction with my desk, including a 15" Goodmans Bass and two Fostex FE83E. A nearfield setup, driven by selfmade active crossover and T-Amps.
So, you can believe me: when I speak Bass I mean Bass, clean Bass 😀
Franz
An externally hosted image should be here but it was not working when we last tested it.
Indeed, I think it is an improvement in the bass area, I cannot believe it!
Thanks John!
BTW: I am using actually my "subwoofer desk", an open baffle construction with my desk, including a 15" Goodmans Bass and two Fostex FE83E. A nearfield setup, driven by selfmade active crossover and T-Amps.
An externally hosted image should be here but it was not working when we last tested it.
So, you can believe me: when I speak Bass I mean Bass, clean Bass 😀
Franz
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