Swissonic DA24 looking for operation manual or schematic, auto mute and noise

[ADaddy]

Hi, my name is Alan and maybe someone here could help me?
Swissonic company don't exists anymore...
No information about old units, no documents left online, no support.
I have an old converter DA24, which sounds great, but it's noisy and i'm trying figure out why.
I doubt there exist any schematic for it but maybe at least someone have instruction/operation manual for DA24 or DA24MKII.
There are internal jumpers which i'm trying to figure out how to setup. There's change of output level, but i would like to know what exactly i'm changing.
Maybe someone have any experience with noise problem in these units?
Maybe someone know how to disable "auto mute" in these units?
Any kind of help appreciated

 

[pucho812]

I found a review from one of the trade mags about the unit.
The author mentions the jumpers and how he had to go through 18 star screws to get access. They do a +4/-10 operational level setting. He had them removed and preferred they were back in.

But unable to find a manual

 

[cyrano]

I've never found anything about the DA24, except that review Pucho mentioned, but I have a manual for the AD24 if that's of any use?

 

[ADaddy]

I found a review from one of the trade mags about the unit.
The author mentions the jumpers and how he had to go through 18 star screws to get access. They do a +4/-10 operational level setting. He had them removed and preferred they were back in.

But unable to find a manual

Thank you for the input. Yes i know this review, but author wrote about jumpers in AD24 only. DA24 have 2 jumpers per channel and they reducing level in two steps but i don't know should they be removed two at once or there's more options (each one gave different result).

 

[ADaddy]

I've never found anything about the DA24, except that review Pucho mentioned, but I have a manual for the AD24 if that's of any use?

Wow! Thanks! Could you upload manual here? I believe there are big similarities in both unit design, so maybe i will find any usefull information for at least one problem i have with it.

 

[ADaddy]

Overall i found scrap of info that someone disabled auto mute function in this unit, but nothing more.
Since it's noisy, auto mute is annoying function, there's audible click each time you stop playback. From what i have found, in the chip manual, to disable auto mute there need to be changed level state on proper pin. Not really know how to do that.
For the noise problem FIrst i changed all the voltage filtering capacitors (this unit is old and there's a lot electrolytic capacitors in PSU section).
It improved noise a little but didn't solved the problem. I checked every capacitor, voltage regulator, dac chips, balanced line drivers. Each channel deliver and receive same voltages, nothing strange or broken component.

 

[living sounds]

I think I had a noise problem in one of these once and got rid of it by replacing power filtering electrolytics with modern polymer types.

 

[ADaddy]

I think I had a noise problem in one of these once and got rid of it by replacing power filtering electrolytics with modern polymer types.

You changed THT 10x 1000uF/35V for polymer electrolytics? Or Few SMD tantalum capacitors after regulators? I changed these 10 electrolytics for modern low esr and for tantalum i chnged only two in analag section powering for higher values aluminium electrolytics. It helped but not solved the problem.

 

[living sounds]

I think I only changed the caps responsible for filtering the 3.3V or 5V supply voltage for the DAC.

 

[cyrano]

Wow! Thanks! Could you upload manual here? I believe there are big similarities in both unit design, so maybe i will find any usefull information for at least one problem i have with it.

Please find it here:

https://groupdiy.com/threads/swissonics.84494/

 

[ADaddy]

Please find it here:

https://groupdiy.com/threads/swissonics.84494/

Thank you!

 

[ADaddy]

I think I only changed the caps responsible for filtering the 3.3V or 5V supply voltage for the DAC.

There are two smd electrolytics around each DAC - 4.7uF - high values as for CS4390, but thinking change them to 10uF. Voltage rail after regulator 47uF, this could be bigger as well. Besides that bypass on OP275 is also high 2x1uF. Overall noise nature seems to be more per analog side i think. I will try soon change some of those capacitors, if this work i will report it here.

 

[Whoops]

I have the AD24 converter and I had the DA24 in the past, unfortunately I don’t have any manual for it.
I never seen a schematic for these units

These were very capable converters at the time, the company went bust and Thomann bought the rights to the name.

I wish you good luck trying to fix it

 

[ADaddy]

I have the AD24 converter and I had the DA24 in the past, unfortunately I don’t have any manual for it.
I never seen a schematic for these units

These were very capable converters at the time, the company went bust and Thomann bought the rights to the name.

I wish you good luck trying to fix it

Thank you! Yes, thomann bought it to make some cheap stuff under that name, but these converters, as for 90's, were damn hi-end made. Except limitation of 24bit/48kHz maximum (i don't use higher rates) there is nothing to shame to use it 30 years later. I did comparison with modern ferrofish, rme and avid converters and it sounds comparable or even better to some. This is why i want to fix it.

 

[ADaddy]

An update (not so good).
I recapped rail filtering on both, analog and digital, sides. Everywhere 10uF tantalum capacitors, but by occasion i found one shorted transistor (probably source of noise) in one of 5V PSU sections. I replaced two SMD transistors in this section for THT and now converter is not working... Nothing damaged just one isn't proper type. I was able to identify second transistor (not shorted) and replaced it by BC560. Same transistor i used to replace shorted, but definately it isn't PNP.
Non identified is marked as 6TL (SO23 case) whis means nothing completely (i made research in multiple sources).
It wouldn't have no sense if engineer would use two different PNP transistors in such PSU section but from measurements it looked like so i try to use PNP. Multimeter shows on two non shorted pins connection as for PNP as also collector seems to be connected to ground.
Hmm... Maybe it's some FET not BJT?

Anyone knows what 6TL transistor is?

 

[Khron]

How certain are you that it says "6TL"?

https://smd.yooneed.one/code3654.html

 

[ADaddy]

How certain are you that it says "6TL"?

Sorry, but here i don't understand your question too!
Yes i'm certain it is 6TL as also i'm certain that it's nothing from mentioned 6TL on this site.
It's in fact first site on google i found.
6TL on this site refers only to 5pin voltage detectors, so nothing which could fit in the circuit.
I checked also other 6T and SOT-23 package refers only to PNP transistor and already i know it isn't PNP.
It could be some three pin voltage detector but on the PCB it's marked as Q2 which describes transistor and on Swissonic PCB components are rather well described. Anyway i will investigate voltage detectors, it could have sense to use it in this section of PSU but have doubt it is detector.

 

[ADaddy]

BTW. i checked multiple possibilities on mouser offer which include any kind of 6TL marking, nothing...

 

[pucho812]

Can you send us a photo?

 

[ADaddy]

Can you send us a photo?

Unfortunately not, i have broken camera in my phone. There's nothing more printed than 6TL and i'm sure the case is SO-23 not SO 323.
As for the SO-23 pinout (1 and 2) - from LEFT - down two pins in line are shorted (multimeter diode finctione).