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jonners
08-05-2009, 21:33
I've just lost a longish post I was creating on this :( so I'll keep it short now and add more later.

I read mostly favourable comments about the Yaqin MS-12B on the 'net so I've bought one. I thought that at the very least it would tide me over while the rat's nest on the floor that is my diy Jfet phono stage gets organised into a box.

I bought it off eBay: http://cgi.ebay.co.uk/FreeShipping-YAQIN-MS-12B-valve-tube-pre-amplifiers_W0QQitemZ130305035069QQcmdZViewItemQQpt ZUK_AudioTVElectronics_HomeAudioHiFi_Amplifiers?ha sh=item130305035069&_trksid=p3286.c0.m14&_trkparms=72%3A1683%7C66%3A2%7C65%3A12%7C39%3A1%7C 240%3A1318%7C301%3A1%7C293%3A1%7C294%3A50

I didn't want to wait for the free shipping via a slow boat from China so on top of the very cheap 129GBP asking price (can't find a pound sign on this laptop!) I paid an extra 25 for airmail. It arrived in just under 2 weeks, well packed, and extra charges at this end were just under 20 quid.

The manufaturer's website is good for a laugh: http://www.yaqin.cn/en/company.html

The circuit diag. is below but I haven't checked it so can't vouch for its accuracy. Yaqin loses a few points imo for having that emitter follower buffer after the phono stages.

Ergonomically it's a bit odd as you can see, with phono inputs at the front and cd input plus outputs at the rear. It's pretty solidly built, and bigger than I imagined :- 35cm from front to back.

Early listening impressions were favourable, though it sounded a bit rolled off at frequency extremes and the stage with phono input was a bit restricted in width and depth. After a day or so it began to emit intermittent whistling noises (on both inputs). One of the 12AU7 valves was extremely microphonic.
More to follow later....

jonners
08-05-2009, 21:40
My mistake here: I intended to post this in "Analogue Art".

Mike
08-05-2009, 23:46
Moved. :)

Marco
09-05-2009, 07:51
LOL! I moved it from Analogue Art because it belongs in Blank Canvas! :lol:

Amp discussions don't go into Analogue Art (you should know that, Mikey), so back it goes where it belongs... :ner: :eyebrows:

Marco.

jonners
09-05-2009, 08:16
Fine, feel free to continue your game of tennis with my thread, guys. :)
Marco leads by 30 points to 15 in the first set....

To continue: I had expected to be changing the valves when I bought it, so I put in a pair of Sylvania JAN 12AX7's, and Philips JAN 5963's instead of the 12AU7's.
This improved the sound a lot, and virtually erased my previous criticisms to the point where I was pretty happy with it.

After a day or so the odd whistling noise reappeared, so I took the bottom off (see pic) and soldered in some 1k grid stopper resistors at the 5963's. This was quite easy to do, by cutting the pcb tracks leading to the grids.
While I was there I cleaned up the flux that was around. No more whistles to date.

As you can see, getting access to the components would require quite a bit more dismantling, so it's not very tweak-friendly in that respect.
It's clear that the large codpiece that is the mains transformer cover contains quite a lot of air! :eyebrows:

To summarise, if you want something that's definitely plug and play I would avoid it. However if you want something that can give great sound at a low price and you are up for a bit of valve rolling and fiddling, it's worth a punt imo.

There's a guy in Bristol who runs a Yaqin information site and apparently offers repairs and servicing. I know nothing about him though. http://yaqin.slickpepper.org.uk/

Marco
09-05-2009, 09:17
Hi John,

I had a Yaqin, albeit an MC-100B KT88 integrated amp design, so I know how good they are (or can be with some modding), so no doubt the MS-12B hits the spot too as a preamp.

Yaqin are actually a high-end brand in China, therefore this is reflected in the quality of their designs.

The only thing is their equipment is not safe for use with UK voltage (I know as my MC-100B blew a capacitor when it 'overheated'), so the use of a step-down mains transformer is an absolute must, or better still, upgrading to appropriate spec high quality transformers for UK voltage and caps with a higher reservoir capacity which can cope better with the demands of higher voltage.

Some of the websites say that Yaqin equipment is suitable for 240V, but I can tell you from experience that this is bullshit!

If you're using your preamp without a step-down transformer, I urge you to switch it off immediately and not use it again until you've done so, or had it converted for UK voltage, as if left on unattended IT COULD CAUSE A FIRE !!!

Better safe than sorry...

Marco.

Mike
09-05-2009, 09:47
LOL! I moved it from Analogue Art because it belongs in Blank Canvas! :lol:

Amp discussions don't go into Analogue Art (you should know that, Mikey), so back it goes where it belongs... :ner: :eyebrows:

Marco.

Well, if you move stuff it might be helpful to say so... ya big haggis!

'Blank Canvas' is a daft place for amps to be anyway, amps are an analogue device (mostly) but they could easily have their own area! :ner:

TBH, anything could go in the blank canvas section, it's rather 'ill defined'! :upyours:

Marco
09-05-2009, 10:02
Please read:


Blank Canvas

General hi-fi discussion. Anything not covered in the categories below goes here.


Have a look at the categories/rooms below 'Blank Canvas'. Are amps mentioned anywhere at all?

No. Therefore.................!! ;)

'Analogue Art' is for T/Ts, phono stages, tonearms, cartridges, tape decks, etc, etc. It's not rocket science, ya wee zoomeroid :ner:

Marco.

Mike
09-05-2009, 10:10
Have a look at the categories/rooms below 'Blank Canvas'. Are amps mentioned anywhere at all?

No, and they are an item that could easily warrant their own discussion area.... you patronising buffoon! :lol:

Also!... I can't think of any situation where a phono stage would be used except in conjunction with a TT (which was the reason for the purchase of the Yaquin), so I would argue that the phono stage is a turntable ancillary anyway. So there! :p

Marco
09-05-2009, 10:13
No, and they are an item that could easily warrant their own discussion area....


LOL. And create even more bloody rooms? :lol:

Read 'Critics Corner' and you'll see that some of our members are complaining about there being too many, ya shilly wee shaushage :lolsign: :ner:

Marco.

Mike
09-05-2009, 10:16
I think their argument is more about confusion over what goes in which section really....

And we seem to have a prefect example right here! :)

Marco
09-05-2009, 10:20
... and also the number of rooms. Read Darren's last comment :)

I don't 'get' the confusion at all, as everything seems very straight forward to me!

Perhaps someone should start a separate thread where this issue can be discussed/'thrashed out' in more detail?

Marco.

Mike
09-05-2009, 10:25
Nah... it is what it is. ;)

But I still say a phono stage is a TT ancillary! :P

Marco
09-05-2009, 13:34
Of course it is - on its own, but not as part of a preamp (as far as the layout of AOS is concerned).

Is the MS-12B a standalone valve phono stage or a preamp with a valve phono stage built-in?

Preamp = 'amps' and as such belongs in 'Blank Canvas'. All amp discussion should go in 'Blank Canvas'.

Phono stage = 'analogue ancillaries' and as such belongs in 'Analogue Art', along with SUTs and the like. I don't see this in any way as being hard to understand :)

Marco.

Mike
09-05-2009, 15:03
I don't see this in any way as being hard to understand :)

I didn't say it was hard to understand...

Patronise me again 'n I'll chin ya! :smoking:


:lolsign:

jonners
09-05-2009, 16:34
"...ya big haggis" "...ya wee zoomeroid" "...you patronising buffoon" "...ya shilly wee shaushage" "... I'll chin ya"

I think we must be into the second set... :lolsign:

This level of philosophical discourse is above my head, so I'll just say thanks Marco for your warnings about mains voltage. Mine did come in a box marked '240V' and the manual says "input voltage AC 240V+or-10%. Nevertheless I'll get inside again and do some checks.

Mike
09-05-2009, 16:41
Oh, don't worry about Marco and I... we love 'crossing keyboards' from time to time. :eyebrows:

S'just 'banter'. ;)

jonners
09-05-2009, 16:42
Is the MS-12B a standalone valve phono stage or a preamp with a valve phono stage built-in?
.

It's a valve phono stage with a CD input built in! ;)

jonners
09-05-2009, 16:44
Oh, don't worry about Marco and I... we love 'crossing keyboards' from time to time. :eyebrows:


No worries _ I'm enjoying it! :lol:

Mike
09-05-2009, 16:53
No worries _ I'm enjoying it! :lol:

Jolly good! :)

Anyway... am I right in thinking you bought it primarily for use as a phono stage? If so, I might be able to think of a few little 'tweaks' that might help it along. ;)

jonners
09-05-2009, 17:38
.. am I right in thinking you bought it primarily for use as a phono stage? If so, I might be able to think of a few little 'tweaks' that might help it along. ;)

I did indeed, so I would be very interested to hear of tweak possibilities. :smoking:

I did some voltage checks, and all seems well. The mains trans. secondaries are marked 200V and 16V on the circuit diag., and I measured them to be spot on those values with an mains input voltage of 240V AC. So I think it's reasonable to conclude that this model was actually designed for 240V operation.The main supply caps are Nippon Chemicon rated at 400V.
The heaters of the 12AU7's are being run somewhat high, at 13.8V. The 12AX7 heaters run off a 12v regulator - they are fractionally under 12V.

Hey, I just found a 'dead bug' inside it - a 2N5551 transistor lying near one of the phono inputs, with its legs waving in the air, not connected to anything! :scratch:

Marco
09-05-2009, 19:14
Don't worry about Mike and I - we love yanking each other's chain! :eyebrows:


I did some voltage checks, and all seems well. The mains trans. secondaries are marked 200V and 16V on the circuit diag., and I measured them to be spot on those values with an mains input voltage of 240V AC. So I think it's reasonable to conclude that this model was actually designed for 240V operation.The main supply caps are Nippon Chemicon rated at 400V.
The heaters of the 12AU7's are being run somewhat high, at 13.8V. The 12AX7 heaters run off a 12v regulator - they are fractionally under 12V.


Glad it seems safe, John - mine (and a few others) certainly weren't!!

Dunno about this 'bug', though... What was it for, I wonder? :confused:

Marco.

jonners
09-05-2009, 19:25
Dunno about this 'bug', though... What was it for, I wonder? :confused:



The circuit uses them for relay-switching between inputs, so I guess an extra one just got dropped inside and left there.

Mike
10-05-2009, 16:55
I did indeed, so I would be very interested to hear of tweak possibilities.

PM me with your address and I'll send you a couple of valves to try in place of the 12AX7's. ;)

jonners
10-05-2009, 17:45
PM me with your address and I'll send you a couple of valves to try in place of the 12AX7's. ;)

Great! Many thanks - PM sent. :)

Today I tried a pair of 5814's in the 12AU7 position, but got a load of hum. I know the 5814's take a bit more heater current but I don't see how that could account for this. :scratch: Any ideas anyone?

HighFidelityGuy
10-05-2009, 21:36
That ebay seller has quite a lot of nice looking valve gear. I've been fancying tying out a valve pre-amp on the cheap, so I've just ordered one of the Marantz7 (http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&ssPageName=STRK:MEWNX:IT&item=130304823077) knock off's to try out. I think they look nice and a few people seem to think they work well from what I read on a quick google search. The price is fantastic so I think it's worth a punt.

I think I'll try swapping the volume pot for an Alps motorised unit so I can control it via a remote. There seems to be plenty of spare room in the case to allow access for modding, so there's scope for future tinkering. I'm sure more performance can be obtained by swapping the valves too, so I look forward to doing some rolling.

As I'm not in a rush to get it, I just went for the ground shipping, so it'll be a while until I get it. For some reason I find something quite appealing/romantic about getting it shipped on a slow boat from china. :lolsign:

Thanks for the tip on the seller John. :cool:

jonners
11-05-2009, 07:56
I've been fancying tying out a valve pre-amp on the cheap, so I've just ordered one of the Marantz7 knock off's to try out.

Yes I saw that after I ordered mine. I might have gone for it if I'd seen that first.
Let us know what it's like when it arrives. Hope it doesn't get intercepted by audiophile pirates! :eyebrows:

EDIT: Initially I thought this was a phono preamp, but it seems not....

HighFidelityGuy
11-05-2009, 09:41
Yep, I'll make a new thread when it arrives so I can let everyone know what it's like and get some modding advice. Like you say it's not got a phono stage built in unfortunately which I would have preferred but as I don't have a TT yet I can get over that. It was mainly the line pre-amp part I was interesed in tinkering with for now anyway.

The pirates problem did cross my mind. Hopefully it will arrive in one piece and without me having to pay a ransom. I've got visions of valve and bits of wire arriving in envelopes until I pay a million dollars. :lolsign:

Mike
11-05-2009, 13:00
Yep, I'll make a new thread when it arrives so I can let everyone know what it's like and get some modding advice.

Start by making sure it's safe on 240V, and throw away the nasty Chinese valves...;)

The Grand Wazoo
12-05-2009, 08:01
The pirates problem did cross my mind. Hopefully it will arrive in one piece and without me having to pay a ransom. I've got visions of valve and bits of wire arriving in envelopes until I pay a million dollars. :lolsign:

Hehe - Getting it kidknapped might be a good thing.......'cos they'd send you an EAR!! That might be preferable, no?

jonners
14-05-2009, 20:45
I'm still getting some intermittent high-pitched whistling noises from this preamp, starting about 20 mins after power-up. :(
The sounds happen whichever input is selected, and are unaffected by volume control setting. Hence I assume they originate in the 12AU7 stage, after the volume control.

jonners
25-05-2009, 23:07
I think I've silenced the whistling noises - by giving the valve pins a good clean-up.
Another problem that has emerged is that switching from CD to phono input can sometimes cause a hell of a bang through the speakers. :eek: The capacitors after the phono stage need to be followed by resistors to ground in order to prevent this.
In conclusion, it's a very good-sounding preamp for the money. However it needs decent valves plus a bit of tinkering, and that suits me - but it's not for everyone.

tomatamot
19-01-2010, 10:01
After a day or so the odd whistling noise reappeared,

so I took the bottom off (see pic) and soldered in some 1k grid stopper resistors at the 5963's.

This was quite easy to do, by cutting the pcb tracks leading to the grids.
While I was there I cleaned up the flux that was around. No more whistles to date.


jonners, how much is some 1K gridstoppers? 2 at each 12au7? On pin 2 and pin 7?
Or just one at pin?

I do love this little amp. Sounds very open and musical, oh....but the noise you mentioned.

jonners
19-01-2010, 23:13
jonners, how much is some 1K gridstoppers? 2 at each 12au7? On pin 2 and pin 7?
Or just one at pin?

Yes, one for each section - pin 2 and 7. But the gridstoppers didn't entirely get rid of the whistling noises.
The biggest improvement was when I used Russian 6N2P valves in the first stage. They are very good sounding, reliable and cheap. But I had to rewire the heaters in series because of them being 6.3V.

tomatamot
20-01-2010, 17:00
Yes, one for each section - pin 2 and 7.

But the gridstoppers didn't entirely get rid of the whistling noises.


So mine!

It`s still whistling and scrunching.:scratch:

jonners
20-01-2010, 19:59
Well the 6N2P solved that problem for me. Rewiring the heaters in series instead of parallel is quite straightforward.

tomatamot
20-01-2010, 20:17
Well the 6N2P solved that problem for me. Rewiring the heaters in series instead of parallel is quite straightforward.

As a sub for the 12AU7 ?:scratch:

Does it make any difference between 6N2P and 6N2P-EV ?

jonners
21-01-2010, 10:01
As a sub for the 12AU7 ?:scratch:

Does it make any difference between 6N2P and 6N2P-EV ?

No, the 6N2P is a sub for the 12AX7 in the first stage. I suspect that this stage is where the trouble lies, and that instability here can affect the whole amp via interaction through the power supplies. Hence you can still get whistling on the CD input.
I think the EV suffix is a quality mark, indicating greater vibration resistance and longer life. Also you can find some with a rhombus marking that are mil spec.

tomatamot
21-01-2010, 10:26
No, the 6N2P is a sub for the 12AX7 in the first stage. I suspect that this stage is where the trouble lies, and that instability here can affect the whole amp via interaction through the power supplies. Hence you can still get whistling on the CD input.
I think the EV suffix is a quality mark, indicating greater vibration resistance and longer life. Also you can find some with a rhombus marking that are mil spec.

Oke John,

Just ordered some 6N2P-EV in the Ukraine.

I assume to put gridstoppers at these tubes also.

I hope you are right because the present tubes ( Full Music ) are`nt bad at all.

jonners
21-01-2010, 15:34
Hans -

I thought you were possibly still using the original Chinese valves. The Full Music have a good reputation, so whether the Russian valves will solve the problem in your case I don't know. I can only say they worked for me, whereas the NOS 12AX7's that I tried didn't help (apart from improving the sound).
So far I haven't put any gridstoppers in.

jonners
22-01-2010, 12:28
Hans -

When you put the 6N2P's in, notice that pin 9 is a screen between the two sections so it would be good to earth it. ( On the 12AX7 pin 9 is the heater center tap so I think you'll find it is left unconnected on the Yaqin).

tomatamot
23-01-2010, 07:56
John,

I know. Found yesterday afthernoon a few nice 1K2/3W carbon resistors, cheap! I try these at first and in the mean time I have to wait on the Russian tubes. I d`nt expect a great result of the 6N2P`s, but you never know.

trailer
14-02-2010, 17:32
Any of you valve heads had any experience with one of these?

http://cgi.ebay.co.uk/Yaqin-CD3-Tube-Signal-Upgrade-Tube-Buffer-6H8C-Tubes_W0QQitemZ260552065202QQcmdZViewItemQQptZLH_D efaultDomain_0?hash=item3caa1d00b2

trailer
16-02-2010, 18:41
I guess not?

jonners
27-02-2010, 23:13
Having read good things about the TJ Full Music valves, I tried a pair of their 12AU7's in my MS-12B. Result: Return of whistling noises. :(
These are much more microphonic than the JAN 5814's I was using before.
I pulled the TJ's and put the 5814's back. Result: No more whistling noises. :)
Any progress with your Yaqin, Hans?

tomatamot
02-03-2010, 03:42
Having read good things about the TJ Full Music valves, I tried a pair of their 12AU7's in my MS-12B. Result: Return of whistling noises. :(
These are much more microphonic than the JAN 5814's I was using before.
I pulled the TJ's and put the 5814's back. Result: No more whistling noises. :)
Any progress with your Yaqin, Hans?

John, I have at the moment TJ Full Music 12AX7 in a EAR 834P MM. Sounds beautiful!
I`m finished with my MS-12B.