Yaqin MS-22b Phono Amp

[coolzero]

No No Kanishka, no grid leak! Both the Yaqin and my circuit are DC coupled directly to the preceding Triodes Anode. In the case of the Yaqin this is direct but in my circuit it is via the 180k resistor RAE.
This is what makes it much easier to try. Les

P.S. Don't forget to remove the Mosfet first

Thanks Les. Sorry for my lame questions.

BTW, what about the idea of making the first half of 12AU7 as CF buffer for DVD/CD input? Is it a sound approach?

Regards,

Kanishka

 

[Hi_Q]

Now you have lost me Kanishka. I never really understood the purpose of the MS12 as the CD outputs are usually large enough to drive a main amp direct yet clearly the first half of the 12AU7 is to get some extra gain. If it had contained some extra circuitry to control EQ like a Bass and Treble control (with a bypass of course!) then I could see the purpose of it. I suppose its value would be for those that have only one input to their main amplifier which at the same time has no volume control, indeed the MS12 may add some value here. The amplifiers I use already have a volume control and a switch to select any one of four inputs. If your amp does not have these then I can see why you may wish to preserve the controls the MS12 provides. Configuring the MS12 to the new circuit with a tube buffer yet keeping the internal volume control working is possible but would require some major changes and additions. BTW changing a 12AX7 for a 12AU7 will have no impact on the present filament supplies as their requirements are the same.

It's crazy but looking at the original MS12 circuit, I get the impression that the first half of the 12AU7 inverts the selected signal, yet it stays inverted through the buffer and out to main amp? Or am I getting too old?

 

[Hi_Q]

Kanishka, In the light of certain discoveries, perhaps you are wise to think of making the first section of the 12AU7 as a CF using the capacitor input circuit you posted. You can then directly connect the second half of the 12AU7 in the manner I have shown such that it replaces the Mosfet directly. You can then feed the outputs either to separate RCA jacks for either RIAA or CD/DVD or use the relay to select whichever buffer output you want to feed to the RCA jacks. At least you will not suffer 180 degree phase shifts on all of your sources

 

[coolzero]

Sincere apologies. I think it was too lame to ask those questions. In a way you are right because all these will damage the purpose of making MS12 a better phone stage. I will now stick to the original idea of just connecting the gate to grid and forget the rest.

 

[Hi_Q]

Let us know how it works out, you should get even better resolution in the audio.

 

[coolzero]

Let us know how it works out, you should get even better resolution in the audio.

Sure do. I will post my feedback as soon as I complete this. Thank you again Les for all your kind assistance.

 

[coolzero]

Les, I tried the change. In fact it made the sound more open and detail. Fully worth the effort. I kept 12AU7 because it maintains the original op-points you have suggested and had the best sound. FET version had more gain but without it sound more opened up. Thank you for all the help.

 

[coolzero]

Thinking of scrapping the Yaquin board fully and do my own with Les design. Try to add full tube HV PSU or Tube rectifier combine with SALAS HV PSU. Only issue with the space but I will try a different casing otherwise.

 

[Hi_Q]

Hi Kanishka, many thanks for the update and glad it all worked out OK. Probably like yourself, I did not think there was anything to be gained by swapping the Mosfet for a valve considering they are just working as Buffers. It serves I think, as an amazing example of how old technology Thermionics can excel over solid state, efficiency issues put aside. I think I would rather waste a few watts in heat if it means a better listening experience, but yes the difference between the two is so obvious, that it cannot be taken as just being perceived. Meanwhile, I have to thank you for drawing my attention to the design errors in the MS12B. I still cannot get over the discovery that it inverts all of its inputs by 180 degrees, uses unnecessarily, two buffers in the RIAA chain and lacks so much attention to design excellence in the low voltage circuits.

 

[coolzero]

Les, I completely agree with your point that even tube electronic is old school, it still has potential of challenging somewhat latest technology when it comes to the end result. That could be the reason most of the DIYers still appreciate tube electronics beside the fact that it is more fun working with tubes.

BTW, do you think that this new Yaqin design will benefit of using a tube rectifier/SALAS HV and better filament supply like ROD's? Also, have you tried different op-points than you mentioned in the schematic? Appreciate your suggestions here.

Regards,

Kanishka

 

[coolzero]

Oh man this thing can really sing now. Joni Mitchell is standing in front of me and singing live at my home. . Thank you Les. You are the man. lilc, credit goes to you as well for getting me here. Really appreciate the help from both of you.

And for everyone, I like to share this nice link I happened to came across. Plenty of good reading on electronics.

http://www.tubebooks.org/technical_books_online.htm

 

[lilc]

Kanishka,
I'm happy that things worked-out for you with this conversion and I'm glad that I was of some help to you, even if I was just the messenger. As you said, Les is the man. Besides creating the write-up that describes the work involved, I know that Les has helped numerous individuals personally (including myself) with the conversion. Thank you Kanishka for the kind words and thank you Les for everything, it's been a while since we've talked and I want you to know that my LesBox is working flawlessly and is still f***king awsome. Kanishka, good luck to you and I hope that you continue to enjoy your unit as much as I have mine, I absolutely agree with member troutmask123 when he commented "I can't imagine ever buying another phono pre".

 

[coolzero]

I understand that Jazz usually sound good through tube electronics, but rarely I heard such a speed and timing for rock/pop from a tube phono-pre before. It is truly an amazing experience to listen to this phono now.

 

[coolzero]

Les, I got the winged 12ax7 yesterday. As you rightly said, it really sings. Having very luscious mid tone is something I noticed immediately about this tube, compared to other 12AX7s I have. Also it mated well with other 12AX7s (specially with Mullard reissue) in second stage, which I haven't had much success before. Winged - Mullard combination had amazing detail but I felt the overall sound was slightly off PRAT. When I switched the secondary tube with NOS-RCA 12AU7, everything came back to live again. Never mind the little compromise in gain because end result was too good to compare.

 

[Hi_Q]

Kanishka, now that the pre is giving you the full works now, you will notice more the subtle differences that tube rolling gives. You will soon find the best combination that suits you but I think you already have :-D Enjoy!

 

[Steven0100]

Les, I have a question about the winged 12ax7 you recommended.

In your 3 tube remake of the Yaqin 22B, would you use these in all three slots?

 

[Hi_Q]

Hi Steven, yes I use the winged =c= in all three positions, even in a Cathode Follower circuit one can hear differences between different valves - crazy.
I found Electro Harmonix also sound good here too.
Les

 

[pylie]

Hi Les and everyone else! In the last few days I have ordered all items to change my MS22 according to your great manual. I was thinking about the same question like Steven and it seems to be the correct decision to order the same type
BTW I choosed the RT080 7025 WA TAD HIGHGRADE tubes from TubeAmpDoctor. Maybe some of you know this.
I have no experience in doing myself hifi components. Could you explain in some easy words what does this third valve? You wrote it's working as a buffer, but I do not understand this. Language barrier could be also a reason ;-)
Theres only one questionmark on my list. I cannot find the 1M and 1k resistor with 0.125W. I only get it with 0.25W. Does this fact make any differences?
Thanks a lot for your time and help!

Sincerely Daniel

 

[Hi_Q]

Hi Daniel, a Buffer aka Cathode or Emitter Follower provides a lower impedance output for driving signals through cables to your main amp. In the MS22B this function is provided by the Transistors on each channel output. It is quite common to have a unity gain stage to act as an isolator even in op-amp circuits, usually called a non-inverting Buffer. In the MS22B the Buffer stage not only feeds the output cables but also the EQ circuitry which one would not expect it to do. The third valve in the conversion acts solely as a Buffer and has no connection with any of the EQ circuits. In the MS12 the same circuit as the MS22 is used but the output is fed to an inverting stage before a dedicated Buffer, crazy as it sounds, all signals going through the MS12 are made 180 degrees out of phase and worse still, the RIAA stage signals go through 2 stages of Buffering. Don't worry about the wattage rating of the resistors in question, the smallest of 1k resistors however make them easier to fit on the inputs to V1 and V2. Hope this helps - Les

 

[pylie]

Hi Les! Thank you for the detailed answer. But now there are two more questions coming up.
-What is the advantage when there's no connection to the EQ circuit after conversion?
-Is the quality of the v3 important when it's not connected to EQ as long it's a ECC83 like V1+2?

This morning my V3 and holder arrived from tube amp doctor
Tomorrow on my work I will drill the hole and then I hope in the next few days I have time to change all items.
I will give you all some feedback when it's finished

Daniel