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Old 22nd September 2020, 04:27 AM   #1
cellojazz is offline cellojazz  United States
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Question Upgradng Yaqin MC-13S - Parts Questions

First, my appologies, I may not know the best formatting as I'm new to this forum, so I hope my post is functional enough. If not I'm willing to learn!

I have an audio repair person helping me with some upgrades for my Yaqin MC-13S. I am also getting started with DIY audio and am planning to try a preamp soon - but I'm not ready yet and I want my amp functional before the holidays :-) Also, I might not have gotten the specs right from my repair guy. I think I'm close, but looking for help there too.

The upgrades we are attempting are listed here... although the documentation is a bit sparse:

Yaqin MC13s Upgrades and Switchable Feedback Installed – AD Audio Consultants

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The quick version is that they made these changes:
Elna Silmic bypass capacitors,Mundorf ZN coupling capacitors, and Takman carbon film resistors, and a switch to disable negative feedback.

My repair person gave me the parts I would need, although I wanted to double check because he's ultra busy - and I want to make sure I understand as best I can.

1) Coupling Capacitors: .47mF 600v(or more) x 4
2) Bypass capacitors: 470mF 25v x2
3) Grid Resistors: 2w (or 3) at 820 ohms
First - could someone confirm this is accurate from this schematic:

Second I was planning on:

Mundorf Supreme SilverGoldOil caps
and Audio Note Silver non-magnetic Resistors (820R Ohm, and 2Watt).
Are these decent choices?

Thank you in advance for looking over and helping me.
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Old 7th November 2021, 11:12 PM   #2
Marintz is offline Marintz
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Join Date: Apr 2017
Hi, I know this is a year old thread but i'm also interested on this!
Did you go ahead with the mods? I thought the major change would come from swaping the 4 coupling caps, not the bypass caps. Can anybody share their experiences about changing caps on this or similar amps?

I was thinking about using cheaper caps, the most I'll be willing to pay for would be Audyn Cap Plus, Mundorf Evo Oil or Jantzen Superior Z... I'm considering too Jantzen Cross-caps, Solen Fast, Wima MKP10, Russian PIO k40y or k42y, Illinois Caps...

Last edited by Marintz; 7th November 2021 at 11:21 PM.
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Old 8th November 2021, 01:08 AM   #3
vinylkid58 is online now vinylkid58  Canada
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Location: Victoria, B.C.
Originally Posted by Marintz View Post
Russian PIO k40y or k42y,
I've got K40y-9's in a couple of my amps. They work great for coupling. 630v .22uf. Haven't tried k42's.

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Old 8th November 2021, 03:22 PM   #4
Marintz is offline Marintz
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Thanks, I feel I need to try for myself these PIO caps and some other PPs.
By the way, I think the original poster put this in the wrong section, maybe that's why he got no answers? I might open this topic somewhere else later...
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Old 8th November 2021, 06:23 PM   #5
kartk is offline kartk
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Join Date: May 2014
I was reading this post yesterday as I got my hands on a MC-13s recently. In past I have used WIMA and JFX coupling caps in Cayin amps with good results. Russian pio caps surely have better SQ but the size is something I am not sure will fit underneath preamp board in MC-13S.
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Old 8th November 2021, 06:25 PM   #6
kartk is offline kartk
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Join Date: May 2014
Also I wanted to check on feedback mod.Tthere is a mention of adding a switch to disable negative feedback does it mean I bypass R229/228 as per the schematic shared below?

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Old 8th November 2021, 10:24 PM   #7
Marintz is offline Marintz
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Join Date: Apr 2017
Thanks for the info.
I can't help you about removing the negative feedback... but IMHO I don't think the amp needs that, i'd fear it could add noise floor
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