View Full Version : Xiang Sheng valve output modifications
Firebottle
12-02-2018, 15:37
I've had the Xiang Sheng DAC-01A for a while now and was never struck with the quality of the 'tube' output, preferring the 'normal' output.
However even though the DAC is of commendable quality at its price point, the normal output does have that little bit of digital glare.
On investigation of the valve output/buffer stage I found that both input and output coupling capacitors were of Polyester dielectric, a definite no-no in my book, plus the valve was run at quite a low anode (plate) voltage, so certainly not in the best linear portion of the characteristic curves.
Also, just to provides that sods law element, the valve pin out was like nothing else, a 6N3P. So a little more complicated modification than I would have hoped for.
First off I replaced the output capacitors with some decent polypropylene's but that didn't make much of a difference on its own.
The valve socket is on a vertical daughter board so that had to come out and an alternative provided that could offer the different pinout.
The heater and HT power supplies were simplified in order to provide a greater voltage. The valve chosen was a PCC88.
The input capacitors were also changed for some polyprops, the yellow ones in the picture.
http://i64.tinypic.com/2d2a1g.jpg
The end result was a healthy 90V across the valve plus a much cleaner 'tube' output without the digital glare of the normal output.
Result :mex:
nice mod alan. i run both outputs into 4 speakers. cant say ive noticed the valve to be that bad although i prefer the ss, which goes to the main speakers. the tube goes to my little active ones on top for extention of the full range driver purposes
Bigman80
12-02-2018, 16:39
Well done matey
I just ordered one to play with/mod.
Plus some bad boy valves. Believe it or not some Western Electric and Sylvania Gold pins. Will get the soldering iron out too I expect.
Western Electric Xiang. Has to be cool. Or crap. One of the two.
Johnny nocash
13-02-2018, 09:18
Hi Alan, interesting stuff. I know there are at least 3 different versions of the 01A.
Was your Xiang Sheng the one with the Cirrus chip & upgraded TE7022 daughter board?
Firebottle
13-02-2018, 09:50
I believe so.
I went for what looks like an older one. More boxes to play with. And a French DAC 3 too.
https://www.ebay.co.uk/itm/XiangSheng-DAC-01A-DAC-Headphone-Amplifier-XMOS-U8-USB-Bluetooth-Receiver-Silver/172436267251?hash=item282600a0f3:g:ahEAAOSw5cNYSBO c
What was the HT before the mod?
Jim.
Firebottle
13-02-2018, 21:25
Originally there is a simple shunt regulator on the board limiting the HT to +77V.
The valve then sees 65 volts anode to cathode.
With simplification the HT is raised to +118V, then with a change of cathode resistance the valve sees 88V anode to cathode, could be made slightly more.
Around 90V is ideal for an ECC88 or PCC88.
Nice mod!
I bought one of these recently and it arrived with a very healthy channel imbalance across all outputs!
Tried to get a schematic but no joy at all. I don't suppose you have one?
Anyway, working blind my tech friend changed the LF353 opamp but no joy.
All the resistors around the chip seemed fine But he was getting weird readings around the pins either to Ground or to themselves.
Anyway, he bit the bullet and did a complete blanket change of all the electrolytic capacitors, some of very dubious make! He also removed the 8 pin socket which looked as though it could be contaminated, possibly chemicals from an electrolytic and thoroughly washed the board. Didn't have a spare 8 pin socket so made one from a 20 pin one.
Caps replaced:-
33 & C34 3.3uF 50V
C37 & C38 47uF 25V
C39 & C40 100uF 50V
C43 & C44 3.3uF 50V
C47 & C48 10uF 25V
C81 & C82 10uF 25V
Second board wash after fitting above and it now works, err well almost. The NORMAL outputs are spot on but the tube outputs have a small imbalance, the Left out is -1.2dB down. After 15 mins the imbalance drops to -0.8dB so maybe it is just the 6N3 valve? I going to try a 5670 GE..
Anyway, the joys of buying from China!
must have got lucky. mine is still working fine
https://ttywow.ch.files.1drv.com/y4mLyBcOuMYsJaJDcvaw0GkGyM3DGM0Qo8SiFgHTT2Ezaa55p0 pyo9KKcoSYx_0OISkYmOjzcZfQE0LtriRaRZiRHm2SJLrQr6XL lj5olNZ6A9ZvPTJ7wE-8o64guFvyPXoYAqyqZXOcN-u9sLrQp4LbylI1HpQE36--x2S6QtabEflAY57W5SVnopvsteO-puenoJ-3WFlz2rU6oQ2BRAzFQ?width=5472&height=3080&cropmode=none
Well, the valves have arrived by the Xiang was ordered during Chinese New Year. So actually it has only just been sent... but by FedEx so it shouldn't take forever.
Finger's crossed.
Getting the camera to focus on the glass Marilyn mat proved impossible. No gags about valves being a girls best friend, please:D
Jerry seems to think the valve output was compromised too, so this may be a waste of dosh. However, I think he had a different variant... maybe.
Primalsea
27-02-2018, 18:47
Nice Mod, Alan. I am not really a fan of valves run at low plate voltages. Just doesnt sound like you are getting the best out of them.
I borrowed this DAC off of Jerry a while back and like Alan says it is 90% of the way to being outstanding.
Alan, have you considered replacing the power supplies with something ridiculously overspecced for purpose? They say that makes all the difference. I've asked my EE mate to do that with a Cd player but he won't as he says it would be a waste of effort. So I'm counting on you :D
Firebottle
27-02-2018, 21:20
I haven't but well worth considering.
When I have some time I'll investigate further.
I haven't but well worth considering.
When I have some time I'll investigate further.
Cool.
Bigman80
14-05-2018, 19:41
I've replaced the M2Tech Young with this, not in terms of an upgrade (because it isn't) but just for ease of use in my system. I will probably try a ridiculously over spec PSU for it as i am getting into this tinkering lark lol
From what I can gather reading up in the latest DACs the power supply contributes much towards the DACs performance along with galvanically isolated USB ports and as much RFI isolation and noise vibration illimination as possible.
Bigman80
14-05-2018, 19:51
From what I can gather reading up in the latest DACs the power supply contributes much towards the DACs performance along with galvanically isolated USB ports and as much RFI isolation and noise vibration illimination as possible.Galvanically isolated usb? That's probably not going to be easy lol
Galvanically isolated usb? That's probably not going to be easy lol
I would like someone to explain to me how it is done.:lol:
Bigman80
14-05-2018, 19:59
Lol
I would like someone to explain to me how it is done.[emoji38]
Galvanic isolation obviously has a big effect.
http://www.whatsbestforum.com/showthread.php?17071-Galvanic-isolation
Bigman80
14-05-2018, 20:19
Potential Jitter issues with USB isolation? Jesus!, it's a mine field.
Hi Alan , I have bought Xiang Sheng dac , would be very grateful if you can advice me on the same modifications as you did regarding anode voltage - I sent you two messages on the forum but maybe some problems with service ? Thank you . Best regards . Val
Firebottle
19-10-2023, 09:50
Hi Val, this was over 5 years ago, i don't have the Dac anymore so can't refer to any visual clues.
I removed the shunt regulator consisting of a 75V zener and a transistor, I think an E13005.
I'm guessing I left the main smooting capacitor after the HT bridge rectifier (I have a 150uF shown on my scribbled circuit) then added a 1K/90uF RC filter to provide approx 120V HT on load. 100uF is a more common value.
Hope this helps,
Cheers
Hi Alan , thank you for your reply - very grateful , i still waiting for delivery from China , can I send you a photo of the dac inside when it's arrived ? This model with different chip , but same valve - I would be guessing that the same circuit ? I have plenty of 5670/2c51c valves when I bought Havana dac many yers ago , and 120v ht what you get after mods is very close to optimal working condition for this type of valve - which is 135v i think ? This is an old thread - if its possible - could you please send me your contact details in message and I can send you a photo . Thank you very much again . Best wishes . Val
ive still got my dac somewhere in spare room in a box with fancy valve... it was so long ago i cant remember what valve it was but it is a v good dac. one day when the room gets cleared i might find it again...
Firebottle
19-10-2023, 11:53
if its possible - could you please send me your contact details in message and I can send you a photo . Thank you very much again . Best wishes . Val
Just send by PM, I did receive your previous messages, just hadn't found the info.
Hi Alan , thank you for your reply , but I didn't have message in my box , and I didn't have notifications about sent messages too , maybe admin/moderators can help ? Thank you in advance
Lawrence001
19-10-2023, 19:14
ive still got my dac somewhere in spare room in a box with fancy valve... it was so long ago i cant remember what valve it was but it is a v good dac. one day when the room gets cleared i might find it again...I think it was a Tesla and you were interested in trying a WE 396A?
https://theartofsound.net/forum/showthread.php?57968-WTD-Western-Electric-396A-valve
Hi Alan , thank you for your reply , but I didn't have message in my box , and I didn't have notifications about sent messages too , maybe admin/moderators can help ? Thank you in advance
Hello Val and welcome to AoS.
As you are a new member, you need to make 10 posts before you can send and receive Private Messages.
So only three more post to go: why not use them to tell us about your system and what kind of music you like to play on it?
Cheers
Barry
Hi Barry , thank you for explaining
Hi Barry , actually i was registered in 2010 - maybe new old member
9 posts so pms should be active.... usually about 6.
My system still unfinished , hence not updating my page yet . Xiang Sheng dac is on the way , Khozmo passive into nutube valve buffer ( bought second hand nutube pcb , but still need some parts for that ) , amplification - amptastic mini , needs to be modified - I want to transfer pcb to different chassis to be able to change capacitors , valve amplifier Art Audio PX25 set , waiting for recap .Speakers is going to be Lii Song 18'' in open baffle . All promising , but still long way to go , funds permitted .. starting with dac .
I think it was a Tesla and you were interested in trying a WE 396A?
https://theartofsound.net/forum/showthread.php?57968-WTD-Western-Electric-396A-valve
yes the WE 396A was one of the valves i had; in fact i had 2 but sold one(to brian i think) but not sure if i still have the other one. i had several different ones at one time. its a good dac and pre if you want to use as a pre(by moving a link per channel inside)
Hello Val and welcome to AoS.
As you are a new member, you need to make 10 posts before you can send and receive Private Messages.
So only three more post to go: why not use them to tell us about your system and what kind of music you like to play on it?
Cheers
Barry
Hi Barry , just checked again - still not be able to receive messages , even as you mentioned I did reach 10 posts
Hi Barry , just checked again - still not be able to receive messages , even as you mentioned I did reach 10 posts
test pm sent
Great , its working , just one more question - can I retrieve Alan's message or do I need to ask him to resend it ? Because no other messages apart of test one in my box . Thank you very much , very grateful
Thank you again , I sent message to Alan again , but no confirmation in my sent items folder ?
thank you again , i sent message to alan again , but no confirmation in my sent items folder ?
you might need to set that up.
Lawrence001
20-10-2023, 19:38
Actually he never said he sent one just that he didn't see yours.
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