I think that circuit cropped up in another thread a few weeks ago. It has so many weaknesses I can only assume it was designed by someone who was new to valves.
This is one of the commercially available product BTW 🙂.
Can you explain how to overcome these weaknesses?
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Redesign it.
I assume you have permission to reproduce the circuit? Perhaps you could identify it. That might make it easier for you to find other threads.
Every design has its compromises. The tweaked RCA setup I've uploaded will interact badly with a few carts. and SUTs, due to the high CMiller of the 12AX7 triode. OTOH, the tweaks fix the so/so bass extension and WRETCHED drive capability of RCA's original.
BTW, the fellow who made the original drawing (from a narrative I provided), loves "boutique" parts, but good quality, industrial, stuff is fine. Notice the changes in blue.
BTW, the fellow who made the original drawing (from a narrative I provided), loves "boutique" parts, but good quality, industrial, stuff is fine. Notice the changes in blue.
Attachments
For simplicity and a shorter path... Wouldn't it be easier to go with a SS based circuit for a Phono pre-amp?
(just asking...)
(just asking...)
I checked the threads on this model. But nothing solid. All about just replacing parts.
Two things I noticed so far without doing anything to the internals. When using a SUT, sound changes drastically. Transformation was from OK to really nice. I think this constitutes to the fact that the input of this phono is not properly loaded for MC cartridges. I am using a DL103 so 100 ohms resistor in the input would change the sound I believe.
Replacing 12AU7 to 12XT7 changes the sound positively. Assume it is because of the difference in gain of two tubes.
I am a novice in to tube electronics so can someone guide me where to start? I am reading Morgan Jones these days to find some clues but I am an impatient person when comes to DIY 🙂
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It won't have enough gain without the SUT using a LOMC like a DL-103, so just leave the loading at 47k.
There are a lot of lousy sounding 12AU7's out there. 12BH7 would be a better tube, but draws double (IIRC) the heater current, which could be an issue for the PS trans.
jeff
You might find the link below to be of interest, it describes a conversion of the phono stage
(if I understand correctly) of your amp.
http://homepage.ntlworld.com/lez/Yaqin MS-22B/Putting 'Life' into the Yaqin MS-22B.pdf
(if I understand correctly) of your amp.
http://homepage.ntlworld.com/lez/Yaqin MS-22B/Putting 'Life' into the Yaqin MS-22B.pdf
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I've spent a few weeks listening to my "Les Box" (converted Yaqin MS22-B, see Hi-Q's link), and I'm back to let you know my thoughts. There is mega DETAIL here, the sound is open and big and the unit is very quiet now, it sounds excellent. Also, I want to say that Les's (Hi-Q) abilities and efforts in transforming this unit, along with documenting the procedure for others, has been outstanding and it needs to be mentioned. I can tell you from my experience, that he is a very generous and all-around good guy. Obviously, doing this conversion is considerably more involved than replacing a few caps, but if one is qualified and up to the task, the results are absolutely worthwhile. It's difficult for me to imagine that the MS22-B could be taken to an appreciably ( if any) higher level beyond this.
LesBox ftw
http://www.diyaudio.com/forums/tubes-valves/216979-yaqin-ms-22b-phono-amp-5.html#post3342427
http://homepage.ntlworld.com/lez/Yaq...n MS-22B.pdf
LesBox ftw
http://www.diyaudio.com/forums/tubes-valves/216979-yaqin-ms-22b-phono-amp-5.html#post3342427
http://homepage.ntlworld.com/lez/Yaq...n MS-22B.pdf
He hasn't taken the MS22-B to a higher level; he has replaced the MS22-B with a different circuit entirely, which just happens to use many of the same components. It is a transplant, not an upgrade. An excellent idea, as the original circuit could not easily be improved as it was so bad.
^If there are some who do not understand the magnitude or nature of this "conversion", another look at Les's link might be in order.
And although I don't refer to my LesBox as a Yaqin anymore, it did(unfortunately)begin its life as a
MS22-B, and let there be no doubt... it is at a higher level.
http://homepage.ntlworld.com/lez/Yaqin MS-22B/Putting 'Life' into the Yaqin MS-22B.pdf
And although I don't refer to my LesBox as a Yaqin anymore, it did(unfortunately)begin its life as a
MS22-B, and let there be no doubt... it is at a higher level.
http://homepage.ntlworld.com/lez/Yaqin MS-22B/Putting 'Life' into the Yaqin MS-22B.pdf
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