Yaqin Tube Valve Amplifiers

Pingback from Yaqin Tube Valve Amplifiers » MS-12B added to the amplifier section.
Time: December 15, 2008, 12:57 pm

[...] I was given a partial schematic for thisso have added it. [...]

Comment from John
Time: May 14, 2009, 9:23 pm

I recently bought an MS-12B. It came in a box marked ‘240V’ and the manual also stated 240V operation. The amp itself however had 220V + or- 10% marked on it. I checked the voltages on the secondaries of the mains transformer, and with a 240V input they measured exactly as specified on the schematic. The heater supply to the 12AU7’s was rather high though, 13.8V. The main supply caps are 400V working.
I thought the sound was good, and much better after putting better valves in. There is a persistent problem though, in that after it has been switched on for 20 mins or so, intermittent high-pitched whistling noises start to happen. They happen with either input selected, and are independent of volume setting so I guess they originate in the 12AU7 stage. I put some 1k grid resistors in there, but the noises still happen.
Any ideas please?
John

Comment from Peter Brouwer
Time: June 22, 2009, 1:22 pm

I use the MS 12B as a vinyl preamp only. In this capacity it’s been great paired to the MC 10L. I’ve rolled a few tubes through this pre-amp and found that some vintage Philips ECC83 work well in the front (12AX7) and AWL Radiotron’s for the 12AU7’s. I’ve also tried some Electro-Harmonics gold pins. The fit with these was tight against the aluminium lower case (I don’t use the caps!) because the EH tubes are fatter than the vintage tubes. I’ve had no hum like John. I don’t like the front panel phono connectors and earth pole as I’m not trying to show off my mega dollar connectors. Overall 8/10 when the Chinese tubes are replaced with something a little better. Highly recommended for lovers of vinyl.

Comment from Chris Shepherd
Time: June 23, 2009, 9:51 am

I haven’t had the whistle, but where I am the mains frequency is quite high and I got serious transformer buzzing and heating. Withis this in mind I went for a full re-build. I now use a torroidal mains tranformer and have replaced all of the the square blue capacitors within the amp with russian nos teflon and pio caps. I had previously upgraded the valves to EH 12au7 and 12ax7 which sounded great, but with this mod I now get a more substle output. I have lost a little volume, but I have gained more detail from my vinyl and it just sound even more musical, smooth across the whole frequency range. I haven’t tried the square wave test yet, but I will at some point. I love this amp, even if it was a bit of a pain to mod.

Comment from Kryn
Time: January 10, 2010, 5:52 pm

Guys,
You can actually ask for a 240Vac version if necessary, but you really have to ask them for it. I was in contact with a guy named tubestein (ebay seller), from whom I recently purchased a Meng Yue X1 6P1 amp. But I did ask him before that if he could provide one with a 240Vac transformer due to the problems in the UK with European powered stuff. I tend to do so for this one as well (yes, I plan to get one. I do like the design…)

Comment from sgkho
Time: February 24, 2010, 3:21 pm

Hi to all, If you are looking for a tube pre-amp, please look no futher. It can compare with 3500+ pre.in any field.
My current set are vtl deluxe 100 (PM) arcam delta 250t transport dac qed m-68 sonus faber concertino speaker. And my new toy Yaqin ms-12b with stock tube. i dont have to say much at such a price its a steal……..