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In Reply to: RE: Confusion at MX110 12AX7 tube results posted by Paul Kehayas on December 28, 2016 at 20:29:49
I rebuild a lot of Mac amps and preamps.Whenever I get an MX110z that was modded by Mr Modaferri,I always put it back to the original later MX110z design.He raises the resistance values of the plate and cathode resistors and it moves it from the original operating points that produced low distortion and perfect linearity in the critical interim stages.The mod on the MR78 tuner he did was fine which Mac had updated in a service bulletin.
It sounds as tho you are lacking body to the music that the preamp had at one time and that usually indicates filter caps and coupling caps are getting tired.Your preamp may have the stock value components but take a look and see if any new caps were changed such as the can filter caps.If it is a CE on the filter cap with a little sticker,it was changed which it should be ok.
When the filter caps get old,the develop leakage and high ESR and that raises havoc. If you could pop the bottom off,you can see if they used decent coupling caps or some cheap metallized polyesters as some places do.Maybe shoot us a picture because I don't think tubes are going to correct the issue you are having to your satisfaction.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Follow Ups:
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Finally Number 8
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And another...
Paul
Ok so here's some pics.There was a failure of half the filter cap at the back next to the transformer (paper covering on it) and is now aided by a capacitor inside the amp (I believe you will understand and see what that is.
Also another filter multi cap died (the one in the middle) and that was replaced with a Mallory in that position.
Other than that I am hearing a loss of smoothness on the top somehow. I am using an EAR 834 now into the MC240 (McShane and your mod) and it sounds fuller than the once fuller sounding MX110 phono section. I am at a loss...
Did they do something wrong at the shop? Apparently they know what they are doing but have no considerations usually for audiophile tendencies. (all mods are considered idiotic by them)...
Have a look...
Paul
Edits: 12/30/16
My first love was mx 110 mcintosh ,my first tube adventure .
i love it and was my reference for years (i was 30).
I tried everything in there ,but i've always found Ge 7025
and 6201 ge do the trick ;balance between air ,smoothness and
transient attack;they must be well balanced and selected ,
don't use 5751.
Even the tubes in the tuner section influnced the phono sound
(i used sovtek 6au6)
6d10 must be a well selected ge (i remenber i had a bu nch of these
hearing a lot of difference between nos tubes )
Final 12at 7 (cathode follower )make a huge difference too(6201
ge ;my last one was a 12at7wc Tfk marked,Ge production )
Great pre for jazz (never heard miles and chet like this)
I love that sinto-pre
Enjoy(and try to avoid new production tubes in it)
It looks good underneath but can you shoot a photo of the top side cans?
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
I believe I added those three pics afterwards! Check to see them and please let me know if I'm alright here.
Thank you Michael!
Paul
Just as I thought..Those cans are original and they need to be replaced with quad 50s at 500v.It is hard to put in tons of extra capacitance in those other than for the filament circuit which I use a pair of 4700uf at 35v which is perfect..You need a pair of quad 50s at 500v and a pair 4700uf at 35v and the one for the cardboard cap may have been changed from what I see.Also,put Schotky diodes in the thing and if you do this stuff,you will adore your preamp again.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Edits: 01/01/17
That's better news!
The cardboard cap is original. Apparently half of it died and leaked so that's the reason for the extra cap underneath.
Would it be possible to get a list according to schematic of what to get and by what company (keeping the original sound please) of cap?
You mentioned and where your recommended diodes go?
Thanks for this!!!
Paul
Paul
The cardboard cap has to go as well but I didn't mention it as I wasn't sure it was replaced underneath and glued in.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
So that's three cap cans. Is it possible to get a small parts list and what to do for this so I may order it?
My email is paul.kehayas@gmail.com
I thank you for all the attention and help!
Paul
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