CS4397 dac

[gabdx]

Thanks guys, especially leo and hi iihay i got me too a ska under construction ))

Well i might buy a Rakk, or some modified lite 60 , i still don't know and my confidence with china products is going down and down ... though i think the dac is my fault it's a warning about it for moders !, had no problem modifying my dared amp tough ! no chips

I had 2 other bad experiences with chinese products : buying on ebay this guy a opamp like 85 $ and its a non working one, lost my money,

Now i bought some preamp transformer and the instructions are far from clear.. chinese is so tempting because it looks half price of usa gear but there is always a catch somewhere in the design or on reliability.

[iihay]

Thanks guys, especially leo and hi iihay i got me too a ska under construction ))

You'll love the SKA, quality bit of kit

[Puffin]

Now i bought some preamp transformer and the instructions are far from clear.. chinese is so tempting because it looks half price of usa gear but there is always a catch somewhere in the design or on reliability.

I bought a Lite remote controlled Pre-Amp from DiyClub.biz. Cost aout £20 with shipping. 4 unbalanced and one balanced input, relay switching for inputs, Alps motorised pot.

Kit came with no instructions at all as to which pins to attach which sets of wires, and more inportantly how to wire up the senser and adjuster. I emailed and got some info back. Pidgin English! Good start.

Turns out the wire patch cables are insufficient. Some pin sets are 6 pins and the cables have only five wires and 5-hole connectors. If I didn't have copius amounts of "rubbish" that I have taken off over the years. I would not have been able to get it working.

The thing is actually very good for the money and the volume control works quickly. However if you were a newbee you would not have got it working.

[leo]

Some more fiddling, poor things had more alterations

[chakija]

Hi guys !
I also have this DAC and i have done those simple bypassing mods and i putted 2 oscons in C20 and C17.However ,i have not tested if it's working.
Offsets with original opa are 75mV for L and 180mV for R .
Are those values ok?
Will it be ok if i solder 75R coaxial cable direct on board instead of RCA socket?
I 2 have one of those JVC transports so i would solder coax on it 2...

[leo]

Hi guys !
I also have this DAC and i have done those simple bypassing mods and i putted 2 oscons in C20 and C17.However ,i have not tested if it's working.
Offsets with original opa are 75mV for L and 180mV for R .
Are those values ok?
Will it be ok if i solder 75R coaxial cable direct on board instead of RCA socket?
I 2 have one of those JVC transports so i would solder coax on it 2...

Theres a flaw in the original output stage, no matter what chip you use there will always be a DC offset, if you want to lower this you have to properly mirror the differential output, by changing a couple of caps and resistors it lowers the DC offset to +/- 1mV , it also improves the frequency response , the original circuit doesn't make a lot of sense TBH

for now the DC offset is too high so use a decent quality pair of coupling caps on the output to be safe, even though your amp may have an input cap its not recommended to have DC across the pot tracks for the pre, in a lot of cases you get the coupling cap after a pot so any DC tends to give a scratchy sound when adjusting volume, it can damage the tracks

[chakija]

Well ,i think i menage to kill my dac 2 .
With stock opa bypassed ,i connected to 2.2uF and 47R on 100K pot ,and then to my aleph J iteration amp (babbelfish J).I got some loads on speakers even with pot turned down.I didn't have courage to even touch the pot !
I instantly turned it off after 1 minute.
When i turned it on again and measure offsets ,i had some huge values like 1700mV ,and after few secs i didn't have any value at all.Finally ,i cut bypasses and measure exit's from dac and it seems dead.

Source is from my jvc transport connected directly on board with 75R coaxial.

[chakija]

I disconnected spidf and i tried to measure again.
I have now 0.25 V on R+ R- and L+ L- from dac.Does this means it is maybe still alive ??

[paradox]

I've been following this thread for a while and have finally decided to contribute something, albeit a request...!

Leo, do you have a link to a schematic of this amp? I'm just wondering how you know so much about how to effectively modify it, or have you just worked it all out? I'm more interested in the output stage, as I'm considering using it to feed my main amp.

thanks

[leo]

Lots of experience in fiddling with things I find it hard to resist not to meddle with any piece of kit I buy.
Everything is made to a given price, the tweeker does not have these limitations so if theres anything we don't like in a particular circuit we simply faff about until its improved.
Theres also a few design errors on this dac which is probably why they are being sold for cheap

There is a schematic for the dac somewhere (I'll see if I can find it) although a lot of the part numbers on the drawing is different to whats on the pcb so it just requires working out