thank you qusp and asterkao for the assistance, i went ahead and connected the OPT after the 1st resistor, i didn't remove anything so i had 2 different outputs active, OPTs and opamps. by having both outputs i was able to switch from the input selector of my amp and compare. To my surprise, volume was almost identical, so apart from the KLUNK!! when switching it was easy to compare.
the sound from the opt's is different as it tames the very sparkly highs i sometimes get (i am now using 4 x opa627 + 2 x ad8610, and the AD's are known because of their rather bright presentation) which is a good thing, bass is also excellent and i would say it is fuller than with opamps, which is also a good thing...but for now i will keep the opamps, replace caps, test some more opamps and save the opt's to test with a chap USB CS4398 i just ordered, i am sure with a more optimized implementation the opt's would sound even better..but before i fix them definitively inside a enclosure i want to test them with the CS chip...
the sound from the opt's is different as it tames the very sparkly highs i sometimes get (i am now using 4 x opa627 + 2 x ad8610, and the AD's are known because of their rather bright presentation) which is a good thing, bass is also excellent and i would say it is fuller than with opamps, which is also a good thing...but for now i will keep the opamps, replace caps, test some more opamps and save the opt's to test with a chap USB CS4398 i just ordered, i am sure with a more optimized implementation the opt's would sound even better..but before i fix them definitively inside a enclosure i want to test them with the CS chip...
Hi all,
I've been watching this thread for a while. I'm a big proponent of the use of OPTs with V out dac chips. There are a few misconceptions that have surfaced in this thread regarding the need for a load on either the dac chip output or the OPT.
Bifilar wound OPTs do not want or need a load to operate at their best. To my experience, a voltage output dac does not want to see a load that draws any appreciable current either.
Impedance matching is not advised for a voltage type signal source. Impedance matching is used for maximum power transfer, not signal voltage transfer. When you impedance match you lose 6db of the signal voltage right off the bat, and unduly load down the dac outputs.
A good read is the article by Bill Whitfield on audio transformers, found on the Jensen Transformers website in their white papers section. It gives you a good feel for proper usage.
An email to BudP would be a good idea too.
I'm sure no expert, just trying to be helpful.
Best, Bill
I've been watching this thread for a while. I'm a big proponent of the use of OPTs with V out dac chips. There are a few misconceptions that have surfaced in this thread regarding the need for a load on either the dac chip output or the OPT.
Bifilar wound OPTs do not want or need a load to operate at their best. To my experience, a voltage output dac does not want to see a load that draws any appreciable current either.
Impedance matching is not advised for a voltage type signal source. Impedance matching is used for maximum power transfer, not signal voltage transfer. When you impedance match you lose 6db of the signal voltage right off the bat, and unduly load down the dac outputs.
A good read is the article by Bill Whitfield on audio transformers, found on the Jensen Transformers website in their white papers section. It gives you a good feel for proper usage.
An email to BudP would be a good idea too.
I'm sure no expert, just trying to be helpful.
Best, Bill
many jensens are already a lower impedance on the primary than they are on the output side, so the reflected impedance is already balanced. loading the secondary is a bad idea as it will increase noise, but experimenting with loading the primary is worthwhile in my experience. i havent done a lot with vout dacs though, but some have optimum loading that needs to be taken into account, some will not like a low impedance load at all. easy to experiment though, just get some trimmers and turn till it sounds good.
check this thread. opinions are all over the place, but all including me agree loading the secondary is a bad idea, only loading the primary should be played with
check this thread. opinions are all over the place, but all including me agree loading the secondary is a bad idea, only loading the primary should be played with
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I can't argue with The Man but I can state that trafo impedance is not a fixed number as many think. It is merely a performance rating, meaning it will meet specs operating in that environment. The ratio is however fixed and it will reflect impedance in both directions equally, regardless of the DC resistance of the windings.
Naturally, experimenting with the perceived source impedance can have a dramatic effect. I'm wondering about this particular implementation with 4 dac chips in parallel, but also with quite a bit of series resistance on the primary side. I would imagine eliminating the ground shunt and lowering the series resistance to a couple hundred ohms would be closer to optimum for the trafos and the dac chips as long as there is no ground path.
Best, Bill
Naturally, experimenting with the perceived source impedance can have a dramatic effect. I'm wondering about this particular implementation with 4 dac chips in parallel, but also with quite a bit of series resistance on the primary side. I would imagine eliminating the ground shunt and lowering the series resistance to a couple hundred ohms would be closer to optimum for the trafos and the dac chips as long as there is no ground path.
Best, Bill
sure haha The Man, thats funny if you are referring to me, even if sarcasm 
i'm hardly the man, i'm just saying its worth playing with. i never even owned this particular dac remember. but i have found loading the primary to always bring some benefits, though hard to predict how much, so i bought some nice vishay bulk metal foil trimmers to play with.
i'm hardly the man, i'm just saying its worth playing with. i never even owned this particular dac remember. but i have found loading the primary to always bring some benefits, though hard to predict how much, so i bought some nice vishay bulk metal foil trimmers to play with. you may well be right, i hadnt thought about that, but 4 dacs in parallel outputz will be quite low. tweak n see imo. i do seem to remember some of the guys finding the output quite hot when tapping the outputs directly
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dac mods
Hi
I just replace all the 4k resistors after all of wm8740 with 100ohm
and the 1.5k to the ground with 10k
I took the signal from the 1.5k resistor only from + of left and wright channel
and send it throug solen 4.7uf to my amp
I just cant believe my ears...!!!
The best mod i have done to this dac
All other mods was just for fun
Hi
I just replace all the 4k resistors after all of wm8740 with 100ohm
and the 1.5k to the ground with 10k
I took the signal from the 1.5k resistor only from + of left and wright channel
and send it throug solen 4.7uf to my amp
I just cant believe my ears...!!!
The best mod i have done to this dac
All other mods was just for fun
Hi, Thanks for the info, Does the output increase or decrease with this mod, compared to stock?
And In what way that you can describe how the sound improved, Just curious.
Thanks
Hi
the output increase a lot with this mod and with my 6 opa627 the music
was much more detailed and the dynamics was much much better with
incredible good bass
As i was looking for more soft hearing i took the signal only from +
right after the 4 resistors after the 8740
and the sound become as soft as i was looking for, keeping all the other
good characteristics but some high frequence noise came that i canot yet
neutralize
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Hi
the output increase a lot with this mod and with my 6 opa627 the music
was much more detailed and the dynamics was much much better with
incredible good bass
As i was looking for more soft hearing i took the signal only from +
right after the 4 resistors after the 8740
and the sound become as soft as i was looking for, keeping all the other
good characteristics but some high frequence noise came that i canot yet
neutralize
Hi
i neutralize high frequence noise with one small change to the source
of signal. I took the signal from the output for xlr ( only from + )
Howdy guys. I think this is my first post in this particular forum. I just read through this entire thread, and I'm quite curious in this DAC. I'm considering purchasing the balanced version, and I was wondering if there was a thread for that too. I figure the design is quite similar, so a new thread might not need to be created.
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