Yaqin MS 12B phono amp- reviews

[Zero One]

I am looking for a valve phono pre-amp as a starting point for my system, does anyone have any experience or feedback on the Yaqin MS-12B MC/MM phono amp, the price is certainly right and it looks good enough but how does it sound?

I am happy to mod it so I can accept some shortcomings if the base unit is good enough.

[frapa02]

I recently acquired one of these and after some minor work I can say that it does sound very good, especially for the cost (paid £100 plus cost of my mods.)
Basically, you have to check the 12AU7 heater voltage first - this was a serious issue and could ruin some expensive valves. This was alarmingly high at 15.4V here in the UK with 240V mains on a 220V unit. These heaters are fed via a resistor from the unreg supply and I think the resistor was incorrect, even for 220V mains. It was 15R and I replaced with a 22R and the voltage is now much better at 12.90V, with 240V mains. This also cured a small hum problem and some very hot valves! A better option would be to fit another regulator but it was a bit tight.
Next, I replaced the 1uF coupling caps with ICEL 1.0uF 10% 400VDC. These are very cheap but seem to have a very natural sound, although they won't appeal to those who swear by PIOs! Well at least they fit.
Finally, the output coupling caps, also 1uF, were replaced with ICEL 4.7uF 10% 400V. This improved the bass extension when driving solid state amplifiers.
The simple mods made the MS-12B sound like it would challenge a much more expensive unit. So far, the stock Chinese valves have been used and they do improve a lot with use. I will try some more refined ones next.
Another comment, I am beginning to love this as a pre-amp buffer from my home brew DAC. It improves the dynamics and everything sounds more solid. I am not sure why yet.
The only problem I can report is that it takes a while to strip and re-build the unit to work on it.
Paul.

[migkiller1971]

Can someone please tell me where the 15R is so I can replace it with a 22R. I don't have the schematics for it. I' pretty handy with a soldering iron. My 12AU7 can get pretty hot at times. This is what I've done so Far.


http://www.expo29.com/audio/yaqin/ms12b/_DS26556.jpg

Thanks in advance!!!

Cheers!

[audiotux]

its on the left handside down , near the regulator ,
7 or 1 W , 15 Omega for Ohms .

Greetings from Germany
Juergen

[migkiller1971]

Originally Posted by audiotux

its on the left handside down , near the regulator ,
7 or 1 W , 15 Omega for Ohms .

Greetings from Germany
Juergen

Thank you so much Juergen! I lived in Heidelberg, Germany for 12 years and both my sons were born there. It's about gluhwein time!!!

[audiotux]

yes Migkiller its Gluehwein-Time !
and all the Christmas Things like Lebkuchen , Dominosteine and so on.
For Tube-Freaks glowing (glueh) is always nice .

Enjoy the _glowing_!
Juergen

[migkiller1971]

Now I have to find out what kind of resistor is best. I know its a 22R, Why can we make our "7" with the line across it? Cheers!

[audiotux]

the 7 meens 7 Watt , you can buy a 22R - 7 Watt Resistor
on your local electronic supplier /shop , ask the man behind
the desk .

Juergen

[migkiller1971]

Originally Posted by audiotux

the 7 meens 7 Watt , you can buy a 22R - 7 Watt Resistor
on your local electronic supplier /shop , ask the man behind
the desk .

Juergen

Hi Juergen,

Yes, I know its watts but I'm going to have to open it up again to see if its 7 watt or 1 watt. I can't tell from the photo. Also what kind of Resistor? Wirewound? Carbon Film? I'm Learning alot or re-learning. Alot of Fun... Unfortunately, I don't have a local Electronic supplier. Cheers!

[audiotux]

Hi Migkiller ,

for example , a simple Metalloxidschichtwiderstand from Mundorf
MR10 , 22R 2% 10 Watt ca. 1,60€ is okay .
You can see that Resistor on www.schuro.de .
So ask at a lokal Shop in your aera for a 10 Watt Resistor and the
job is done !

Jürgen