Yaqin MS-22b Phono Amp

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singlemike

Member
Joined 2015
alvin81 said:
Hello all! New to the world of tubes and valves. I have just received a brand new MS-23B and would like to start on the LesBox conversion. Right now, I am gathering all the required components. It seems that the Lemco 8200pF is rather hard to find. Can I use any other replacement of the same values?
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Yes you can - you can try mouser electronics. I used the allied parts number to gather the details of what was needed and plugged it into the mouser search parameters - looks like 45 can ship immediately

CD30FD822JO3F Cornell Dubilier - CDE | Mouser
 
Hi_Q

Hi_Q

Member
Joined 2007
TheFox, hum can be a devil to trace - is it present with the input jacks shorted out?
If it is not then suspect a broken ground on TT else you need to check that the heater volts is a good DC at 12.6V is close to. Woofer flutter was solved by taking the 68uF to 100uF but a simpler cure may be to run V3 from the other side of the 20k resistors, they are commoned here and using this other supply position introduces more decoupling to the front end. Denny the new circuit is very well proven, it is based on the old WAD design, many were built and I have modded at least 30 MS22's and 23's without any problems. The only thing I have found is the excessive stray capacitance of the Yaqin circuit board and reducing the 220pF EQ capacitors to 180pF can bring the top end more into line with a required -19.6dB reduction..... Les
 
denny9167

denny9167

Member
Joined 2007
Hi_Q said:
TheFox, hum can be a devil to trace - is it present with the input jacks shorted out?
If it is not then suspect a broken ground on TT else you need to check that the heater volts is a good DC at 12.6V is close to. Woofer flutter was solved by taking the 68uF to 100uF but a simpler cure may be to run V3 from the other side of the 20k resistors, they are commoned here and using this other supply position introduces more decoupling to the front end. Denny the new circuit is very well proven, it is based on the old WAD design, many were built and I have modded at least 30 MS22's and 23's without any problems. The only thing I have found is the excessive stray capacitance of the Yaqin circuit board and reducing the 220pF EQ capacitors to 180pF can bring the top end more into line with a required -19.6dB reduction..... Les
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Thank you, I will run this through B2 spice A/D and see what happens!! Not sure this will be an improvement over any classic design!!
 
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akka

Member
Joined 2010
YAQIN RIIA MS-22B "HUM..."

Hi, I have bought a second hand Yaqin MS-22 B RIIA (quite cheap). This RIIA has been modified by some of the previous owners acc. instructions at this homepage and of course his own experience...

I have tested the Yaqin MS-22 B and compared it with my Musical Fidelity X-LPS V3, Yaqin is not bad but it has an disturbing "hum" as many of you have experienced here and at "youtube.com" modifications.

The hum is there and if you play music a bit lauder and when you hear it you can't enjoy the music at all... and I have also noticed that; you can't touch incoming signal cable connectors without a concentricity with an unpleasant noise from your speakers.

I can identify some of the "mods" as for ex. "69" between chassis and PCB earth point. I can solder and make small modifications but what should I do to get rid of the "HUM"? On page 25(39) "Les Carpenter Life bible"? I can see som mod are these to avoid the hum?

If you could give some advise I would be grateful! If you still are interested of MS 22B...:confused:
 
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akka

Member
Joined 2010
The black wire(s) are not connected together near in/outgoing cable RCA around "central turntable ground" point. In my unit there is only one black cable and it goes to "central turntable ground" all other cables are replaced with what I can see silver cables...
 
N

Nick77

Member
Joined 2009
Thinking about picking up a new MS-23b and curious about replacement tubes.

I see the Svetlana winged C as recommended replacement of the stock tube. These are not cheap and compare to nos Mullards ect in price.

How would you compare the sound between the two?? And how do the WingC compare to better tubes like GE Bk plates or nos Mullard ect??

Thanks for any input on the sound of the WingC. :D
 
Hi_Q

Hi_Q

Member
Joined 2007
I think we all have our favourites, the winged C seem to go so well with the MS22/23 LesBox. They have boxed plates so microphony can be a problem but any really troublesome ones can be put into the V3 position. Long Plate JJ's are a good alternative but make sure they ARE long plate and not short. They are now cheaper than the Langrex boxed anode winged C. I recently did a conversion for someone who supplied Mullard ECC83, they sounded OK but not quite the clarity one gets with the winged C.
 
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mraudioguru

Member
Joined 2014
I am hoping to find someone that has done this mod a few times successfully, that could modify my current stock MS22 for a reasonable price.

OR:

Someone that has the modded unit that would trade my stock MS22 plus $$ for it.


I'm pretty good with a soldering iron and have read the directions several times through for the mod, but the LESBOX mod is just a little out of my comfort zone.

I'm located in Colorado (80550) and would like a US based deal. I found a really nice tech up in Canada, but the shipping was almost as much as the mod itself.

Thanks!
 
D

DragonSteve

Member
Joined 2016
Hi
I'm pretty new to tubes, don't have much technical expertise (but I do have two soldering irons and boundless enthusiasm). To be fair I probably wouldn't have bought the Yaqin MS 23B if I'd read Les's comments before hand. Is the design still as bad?

I've tried to access the PDF from post 68 and others, but the links appear to be broken and the document isn't available.

Mine hums like crazy, would doing the modifications here cure that?

If the mods would improve the amp, does anyone (Les?) Make them into LesBoxes any more?

Sorry if these are stupid questions!

Best regards

Steve
 
L

lilc

Member
Joined 2012
Hi_Q said:
Hi Evan, personally I found the 69 circuit unnecessary if you isolate the input grounds. When you gain access to the rear of the RCA sockets you will find that on both the input and output sockets, the manufacturers have soldered the ground tags together and terminated both Black wires (one for each channel). What you need to do is temporarily remove the Black wires then unsolder the two tags away from each other. When you have done this, reconnect the respective Black wire to its Ground Tag. Hopefully the attached simple sketch will help you.
You may have a different issue with RF interference, this is not due to a Ground loop but something else. Have you tried using the Ground post on the MS22B as this may help. Les
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pixelpidgeon

Member
Joined 2016
Hi Les, I'm new to these forums... and also new to Tube Amplifiers. I have just purchased a MS-23B-RIAA, which I am enjoying very much so. I was wondering if you were still doing your upgrade for this Model as I am very interested in listening to how good the Yaqin would make my records sound. Cheers Gra
 
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pixelpidgeon

Member
Joined 2016
Hi. Got another question. Have noticed hum when I connect my Thorens TD208 MK IV to the Yoqin. This is the case whether the turntable it plugged in or not. I presume its to do with a grounding issue. I did read back further in the thread about disconnecting the earth inside the yoqin? Could someone kindly clarify to me what exactly it is I need to do? cheers Gra
 
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