The following is with respect to a converted MS22LB and not the 'off the shelf' standard MS22B.
I received a message asking about adding capacitors across the 1k2 cathode resistors (R2 & R13) in the first stage, which is just an amplifier and has nothing to do with the RIAA. I initially discounted this as it would remove a certain amount of negative feedback here and may introduce more third harmonic distortion but the good thing is that the RIAA characteristics are NOT affected in any way and the signal gets a 5dB boost. I have had others asking for more gain and this may be a way forward. I did a bit of research and found that the original design had them in place but were later deleted. On the various Forums I have found those that like it and others who do not and others who have disliked it at first but liked it after a 'burn in' period. As the cost is just two small 470uF electrolytic capacitors that can be as low as 10V working to keep size down, it would appear to be something to try in the true DIY spirit. I may have a go later on with my own the MS22LB which I have on standby as at the moment, my hard wired versions are ruling the roost and it will be easier to mod the MS22LB.
I received a message asking about adding capacitors across the 1k2 cathode resistors (R2 & R13) in the first stage, which is just an amplifier and has nothing to do with the RIAA. I initially discounted this as it would remove a certain amount of negative feedback here and may introduce more third harmonic distortion but the good thing is that the RIAA characteristics are NOT affected in any way and the signal gets a 5dB boost. I have had others asking for more gain and this may be a way forward. I did a bit of research and found that the original design had them in place but were later deleted. On the various Forums I have found those that like it and others who do not and others who have disliked it at first but liked it after a 'burn in' period. As the cost is just two small 470uF electrolytic capacitors that can be as low as 10V working to keep size down, it would appear to be something to try in the true DIY spirit. I may have a go later on with my own the MS22LB which I have on standby as at the moment, my hard wired versions are ruling the roost and it will be easier to mod the MS22LB.
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Just finished the initial mod, did everything before the adding of the 3rd valve. I have a hiss coming from both channels, almost like white noise. The unit works but I have no "glow" from the tubes. They are warm to the touch but not glowing in any way. The output is also lower than stock, is that normal?
The hiss happens weather the unit is plugged in or not. If everything is unplugged except the ICs going from the MS22 to the amp the hiss is still present and loud enough to severely detract from the listening experience. I did all of the DMM tests and they were all exact or extremely close to the given values.
HELP!?
**after looking over the manual again it may be because I reused the original FETS. Les gave me the parts to do the 3rd valve mod which doesn't use the FETS so I'm diving back into the board now**
The hiss happens weather the unit is plugged in or not. If everything is unplugged except the ICs going from the MS22 to the amp the hiss is still present and loud enough to severely detract from the listening experience. I did all of the DMM tests and they were all exact or extremely close to the given values.
HELP!?
**after looking over the manual again it may be because I reused the original FETS. Les gave me the parts to do the 3rd valve mod which doesn't use the FETS so I'm diving back into the board now**
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Okay the 3rd valve solved the problem.
The LB is really amazing! I can't believe the difference these mods made. The biggest differences I notice are much more separation and layering of the individual voices and instruments and a considerably more holographic presentation of the performance.
I can't thank Les enough for making this as easy and accessible as possible!
The LB is really amazing! I can't believe the difference these mods made. The biggest differences I notice are much more separation and layering of the individual voices and instruments and a considerably more holographic presentation of the performance.
I can't thank Les enough for making this as easy and accessible as possible!
Glad you sorted it in the end, lol the original transistors are not Mosfets which is why it did not work. Glad you fitted the 3rd tube as it beats the Mosfets hands down anyway.
You said you needed more gain? You could try re-fitting the 220uF capacitors you removed from positions C1 and C8, make sure the polarity is correct with the negative terminal going to ground (0V). Now to invoke an extra 6db of gain, apply a wire link across the vacant pads of R11 (may be marked 560) and another wire link across the vacant pads of R14. Simply snip the wire link if you want to revert back to normal gain. This work can be done by just removing the bottom and front panels as the capacitors are mounted at the front corners. Make sure the HT capacitors are discharged before doing any work!
Regards, Les
You said you needed more gain? You could try re-fitting the 220uF capacitors you removed from positions C1 and C8, make sure the polarity is correct with the negative terminal going to ground (0V). Now to invoke an extra 6db of gain, apply a wire link across the vacant pads of R11 (may be marked 560) and another wire link across the vacant pads of R14. Simply snip the wire link if you want to revert back to normal gain. This work can be done by just removing the bottom and front panels as the capacitors are mounted at the front corners. Make sure the HT capacitors are discharged before doing any work!
Regards, Les
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Hi Les,
Hope you are fine.
Just thinking of trying my Les modded MS-12B with 6n2p's. Do you foresee any issue if the heaters are put in series without modifying the exiting heater voltage in this application? Just 12v fed in to 2 6n2p heaters in series. Want to try it before I put a better 6v parallel supply in place for a longer use. Appreciate your advice.
Regards,
Kanishka
Hope you are fine.
Just thinking of trying my Les modded MS-12B with 6n2p's. Do you foresee any issue if the heaters are put in series without modifying the exiting heater voltage in this application? Just 12v fed in to 2 6n2p heaters in series. Want to try it before I put a better 6v parallel supply in place for a longer use. Appreciate your advice.
Regards,
Kanishka
Hi Kanishka, The present tubes are 12AU7 wired for 12V. Having two in parallel means that the total current draw will be 0.3 Amps and the supply is fed from the bridge rectifier via a 15 Ohm 7 Watt resistor. This resistor value must thus be designed to drop 15 x .3 = 4.5V so it can be assumed the bridge rectifier output is somewhere around 12.6 + 4.5 = 17.1V
To run 6N2P, these have 6.3V heaters with a current of 0.34A +/- .025A so on a 12V circuit you must wire the two tubes in series but the current will be the same going through each which is 0.34A. You can see that running two 6.3V 0.3A tubes in series is exactly the same as two 12.6V 0.15A tubes in parallel.
So the circuit should be the same but for the extra 40mA draw from the 6N2's which dictates a lowering of the 15 Ohm to 13 Ohm but I think can be ignored more or less in this circuit. A much better idea would be to fit another 12V regulator to run the 6N2's in series. The usual diode trick in the regulators ground wire will lift the output more towards 12.6V which should be present on both regulators really. The other question remains, if the present regulator was bolted down onto a decent heatsink, could it provide 12V to both sets of tubes (0.6A) and the remaining 0.4A used for the relay and the bistable circuit that drives it. The latter could be replaced by a dual 2 input nand CMOS driver like the CD40107 which has the ability to drive the relay and LED's direct all from a 8 pin DIL pack. I am still putting together ideas on converting the MS12, each time I come to the same conclusion that it really does need a total re-design. But I am slowly coming to terms with my initial total dis-belief of what I saw on the first sighting of the schematic!
To run 6N2P, these have 6.3V heaters with a current of 0.34A +/- .025A so on a 12V circuit you must wire the two tubes in series but the current will be the same going through each which is 0.34A. You can see that running two 6.3V 0.3A tubes in series is exactly the same as two 12.6V 0.15A tubes in parallel.
So the circuit should be the same but for the extra 40mA draw from the 6N2's which dictates a lowering of the 15 Ohm to 13 Ohm but I think can be ignored more or less in this circuit. A much better idea would be to fit another 12V regulator to run the 6N2's in series. The usual diode trick in the regulators ground wire will lift the output more towards 12.6V which should be present on both regulators really. The other question remains, if the present regulator was bolted down onto a decent heatsink, could it provide 12V to both sets of tubes (0.6A) and the remaining 0.4A used for the relay and the bistable circuit that drives it. The latter could be replaced by a dual 2 input nand CMOS driver like the CD40107 which has the ability to drive the relay and LED's direct all from a 8 pin DIL pack. I am still putting together ideas on converting the MS12, each time I come to the same conclusion that it really does need a total re-design. But I am slowly coming to terms with my initial total dis-belief of what I saw on the first sighting of the schematic!
Thank you. Couldn't agree more about you just said.
I tried both with a separate regulator and lowered resistor whilst I posted the question to you and it worked without an issue. Sound wise, Russian tubes had more space around instruments and little more detailed. But was not smooth as the NOS RCA 12au7 I used before. Probably a good idea for someone who wants to have little more into the face kind of sound.
I tried both with a separate regulator and lowered resistor whilst I posted the question to you and it worked without an issue. Sound wise, Russian tubes had more space around instruments and little more detailed. But was not smooth as the NOS RCA 12au7 I used before. Probably a good idea for someone who wants to have little more into the face kind of sound.
Have ordered a Yaqin MS-22B from aliexpress but ran into some problems with the seller. Had to order from a different supplier. This will be sent off to Les upon arrival. While looking around on the web I found that someone is selling a kit for the Les mod on ebay. Perhaps it´s DIY member "soundwise" going into buisness.
General question to members:
I have completed the Les Mod successfully! I did not have a 12AX7 on hand, but substituted in a 12AU7 in place with an on/off toggle for the 6dB gain stage. My question is what difference could I expect to hear with the 12AX7 in place? I don't have one to experiment with so I'd be ordering one specifically for this project. Just wanted to find out if a noticeable difference or should I stick with the 12AU7?
Thoughts/Insight would be most appreciated.
Cheers!
I have completed the Les Mod successfully! I did not have a 12AX7 on hand, but substituted in a 12AU7 in place with an on/off toggle for the 6dB gain stage. My question is what difference could I expect to hear with the 12AX7 in place? I don't have one to experiment with so I'd be ordering one specifically for this project. Just wanted to find out if a noticeable difference or should I stick with the 12AU7?
Thoughts/Insight would be most appreciated.
Cheers!
I don't if you've seen this discussion
from earlier in the thread.
http://www.diyaudio.com/forums/tubes-valves/216979-yaqin-ms-22b-phono-amp-18.html#post3779434
from earlier in the thread.
http://www.diyaudio.com/forums/tubes-valves/216979-yaqin-ms-22b-phono-amp-18.html#post3779434
Tried below on Les modded MS-12B as a SUT for DL-103 with 4K resistor parallel to the 47K input. Great results for a peanut price. Trafo seems to have 1:6 ratio. Just sharing the info with Les box owners if wish to try.
Lo Impedance Mic Element to Hi Impedance Step Up Transformernew from Shure | eBay
Lo Impedance Mic Element to Hi Impedance Step Up Transformernew from Shure | eBay
I found this thread Googling for reviews on this preamp and I was quickly pulled in by the mod potential. I've purchased all the parts to do the Les Box mod, along with 3 Tung Sol reissue 12AX7s I'm going to roll in after the work is completed. For now, I'm burning in the stock tubes and giving a listen to everything, so I have a baseline to compare to.
For what it's worth, my other phono preamps are an Emotiva XPS-1 that I use with my Pioneer PL-630, and the phono stage of my Pioneer SA-9500 integrated amp that I use for my Pioneer PL-550. To say these other two preamps blow the stock MS-22b out of the water is an understatement. The XPS-1 in particular, sounds really nice. I'm interested to see if there's some magic I'm missing though by never trying tubes. It sounds like a Les Box version of this 22-b is a cheap way to play around a bit.
Now, I only have about 4 hours of play time (15hrs total 'on' time, not sure if this counts towards tube break-in?) on the 22-b but so far it's really truly horrible sounding. It's being used with my PL-630 which is equipped with a low hour Audio-Technica AT25 integrated head shell/cartridge.
The bass/mid-bass is the 'best' part, but it's still a little congested and lazy at times, the mids are recessed, and there's this awful, grating, broken up, distorted sound on all the vocals and higher register instruments. It sounds like severe digital distortion.
Is this typical of what others are hearing out of this thing when it's completely stock?
For what it's worth, my other phono preamps are an Emotiva XPS-1 that I use with my Pioneer PL-630, and the phono stage of my Pioneer SA-9500 integrated amp that I use for my Pioneer PL-550. To say these other two preamps blow the stock MS-22b out of the water is an understatement. The XPS-1 in particular, sounds really nice. I'm interested to see if there's some magic I'm missing though by never trying tubes. It sounds like a Les Box version of this 22-b is a cheap way to play around a bit.
Now, I only have about 4 hours of play time (15hrs total 'on' time, not sure if this counts towards tube break-in?) on the 22-b but so far it's really truly horrible sounding. It's being used with my PL-630 which is equipped with a low hour Audio-Technica AT25 integrated head shell/cartridge.
The bass/mid-bass is the 'best' part, but it's still a little congested and lazy at times, the mids are recessed, and there's this awful, grating, broken up, distorted sound on all the vocals and higher register instruments. It sounds like severe digital distortion.
Is this typical of what others are hearing out of this thing when it's completely stock?
I don't remember it being that bad but it has been awhile. FWIW I purchased mine used and it already had new production Mullards installed. It was listenable but definitely not refined. The LesBox is really in another league. I'm using Winged =C= tubes in mine and they sound wonderful. I haven't compared it to any high end phono stages yet but I hope to soon.
Well I feel stupid, this isn't the first time, won't be the last I'm sure!
After reading this I figured I should swap out the cartridge to be sure it was the preamp causing the poor sound quality. I changed the Audio-Technica AT25 for an AT155LC and it sounds way, way better. It's not quite as good as my Emotiva, less clear high frequencies, less '3D' sound stage, but it's pretty acceptable, even with the stock tubes. For what it's worth, it's got well over 24hrs on the burn in at this point.
I'm still excited to hear what the Les Box version sounds like and I'll still be sending it out, just wanted to give this update.
One on hand, good news I guess, on the other, ouch. The stylus for the AT25 is basically non-existant and I'm pretty sure I caused this damage the other day when I thought I got away with knocking it off the tonearm rest onto the spinning Herbie's mat. I guess not
Does anyone know if capacitors C3A, C3B, C10A, and C10B, set the input capacitance?
I run all Audio Technica MM carts and they all call for very low total capacitance, some call for a total no higher than 200pF, and in addition to the input capacitance of the phono pre, you have to add in the tonearm wiring, phono interconnect rcas, and any connection points. If I could replace the above caps with say, a single 1% 110pF cap on each channel, it would get me a lot closer to ideal total capacitance my cartridges call for.
I run all Audio Technica MM carts and they all call for very low total capacitance, some call for a total no higher than 200pF, and in addition to the input capacitance of the phono pre, you have to add in the tonearm wiring, phono interconnect rcas, and any connection points. If I could replace the above caps with say, a single 1% 110pF cap on each channel, it would get me a lot closer to ideal total capacitance my cartridges call for.