Building another M-4

[zaibatsu]

You can look over some threads by Mr. @Bratwurst7s if you want to see some applications.
He usually has a few builds within the first two pages of this forum, most recently a nice M-70.
I've used them in many Yamaha builds myself and had zero problems, like you I use some of the higher-spec ones occasionally also.
I use other brands too - Kemet/RIFA/Epcos, Panasonic, etc, all good gear these days.

They are barely more expensive than electrolytics in those small sizes, and electrolytics in those small-case / small-values have the worst performance of electrolytics in general, so it's a logical use. Some will argue that some circuits are designed around poor capacitors, but given most caps are used for filtering / decoupling, I think it's rare to find a situation where it'll make things worse.

 

[Bratwurst7s]

Woof!

I've been using Wima MKS2 for about the last 10 amps/pre-amps that I've re-capped.

I don't order any elcos in values under 10µF anymore. Since the MKS2 in 10µF are a little large using them depends on how much space is available.

Their ESR is always lower than the equivalent elcos, they generally measure less than +-5% for the 10% types and +-3% or better for the 5% types. Leakage is supposed to be close to zero but I can't measure that (yet) so can't back that last one up with personal measurements.

The Wima's just work, and will never drift. You could say that I like them. There is a soon to be started MX-1 thread that will be using some, although there are actually very few elcos in that beast.

Cheers,
James

 

[stoutblock]

^^^ Thanks guys! Have you used the Wima's directly in the signal path? How do you think one would work in the C401 spot on the M-4? ^^^

Maybe one of these in C401 and C402 piggy backed somewhere? Ha, they cost as much as I paid for the amp!

https://www.parts-express.com/audiocap-ppt-theta-10uf-200v-film-foil-capacitor--027-740

 

[Bratwurst7s]

I have zero experience with the M-4 so can't say anything about that particular position but I'd much prefer a film cap than an elco in the signal path because of their low leakage, and I use them in the signal path whenever possible. I used as many as possible in my CX-1. I've been very happy with the results. The M-70 doesn't have any caps in the signal path so of course nothing to say about that one. But I did use a lot of film caps where I could in the M-70.
http://audiokarma.org/forums/index.php?threads/yamaha-cx-1-thread.790203/

Cheers,
James

 

[Bratwurst7s]

^^^ Thanks guys! Have you used the Wima's directly in the signal path? How do you think one would work in the C401 spot on the M-4? ^^^
Maybe one of these in C401 and C402 piggy backed somewhere? Ha, they cost as much as I paid for the amp!
https://www.parts-express.com/audiocap-ppt-theta-10uf-200v-film-foil-capacitor--027-740
View attachment 1190369

So that means that you bought an M-4 for less than $62? Cool! Way to go!

Cheers,
James

 

[zaibatsu]

I was tempted to suggest the 10uF for C401 and C402 but like James I'm not super familiar with the M-4, you'd want to check the schematic to see if they're actually in the signal path. If they are, then for ~$8 I'd certainly consider it.

That 10uF in particular is a cool product IMO, because a) no other manufacturer to my knowledge makes a 10uF film cap anywhere near as small as the MKS2 in that value, and b) it's available in tape/reel format on mouser, so you get a generous lead length if you do want to fit it somewhere unconventional. Shorter is better of course, but handy to have the option.

 

[Beau Geste]

^^^ Thanks guys! Have you used the Wima's directly in the signal path? How do you think one would work in the C401 spot on the M-4? ^^^

Maybe one of these in C401 and C402 piggy backed somewhere? Ha, they cost as much as I paid for the amp!

https://www.parts-express.com/audiocap-ppt-theta-10uf-200v-film-foil-capacitor--027-740

View attachment 1190369

Take a look here https://www.taydaelectronics.com/ca...-105c-axial-polypropylene-capacitor-jfgd.html

 

[stoutblock]

So that means that you bought an M-4 for less than $62? Cool! Way to go!

Cheers,
James

It would take two of these...

 

[stoutblock]

I was tempted to suggest the 10uF for C401 and C402 but like James I'm not super familiar with the M-4, you'd want to check the schematic to see if they're actually in the signal path. If they are, then for ~$8 I'd certainly consider it.

That 10uF in particular is a cool product IMO, because a) no other manufacturer to my knowledge makes a 10uF film cap anywhere near as small as the MKS2 in that value, and b) it's available in tape/reel format on mouser, so you get a generous lead length if you do want to fit it somewhere unconventional. Shorter is better of course, but handy to have the option.

.

Yes, the cC401 (RH) and C402 (LH) are in the signal path. They are the only electrolytics that are in the signal path.

 

[stoutblock]

I have decided to order a couple of the new kaisei caps from audio note for c401 and c402. I guess they were able to get rubycon to make them. They are similar to black gates that rubycon once made.

 

[stoutblock]

I completed most of the build yesterday. Still waiting on the Audio Note caps but I decided to go ahead with the more proven Elna Silmic II caps for C401 and C402. The Silmic is a great sounding cap IMHO, and as this amp is going to a friend (AK'er ChristopherP), I did not want to experiment. Maybe a future build?

Chris also wants me to upgrade to Vampire speaker posts so they will be installed later. I'll also upgrade the internal speaker wires at that time (typically I use OCC here).

I use the KG type II which is the right diameter but 30mm longer (not 20mm longer as the spec shows). I like the KG because if you trim the posts just a little, they fit the PCB perfectly. They also have very good ripple performance.




Power supply PCB complete. All dis-bond glue gone, new relays and electrolytics.




Multi turn trimmers and new electrolytics for the driver and output boards. All new thermo paste as needed.




Happiness is a complete set of healthy Toshiba outputs!



Biased up perfectly. Those multi-turns are a joy to use!



As promised, these are picture of how I handle the longer filter caps. First make a couple of small spacers for the rear mount that are exactly 30mm thick. I use 1/4" copper tubing.




Then you need to reform the joggle in the factory bracket as shown. A sheet metal brake would be great but a little work with some hammers will work in a snap. You will need to cut a small notch for the transformer pad. I also like to dimple the center hole as the screw fits better and gives more clearance (it is tight). The original center screw works but is just long enough and the dimple also helps with this grip length.




Use longer sheet metal screws and the spacers in the rear. It works as good as original.




It sounds sweet! An amp that is well worth the effort!

 

[stoutblock]

I replaced the 100% original M-4 in my office system with the rebuilt one today. This other M-4 is in near new condition. Clearly the nicest one I have ever owned. Both inside and out, it is like new and was in storage most of its life. I've never had the heart to modify it as it sounds so good as it is. Problem is now this modified amp in the same place takes this system to the next level. Noticeably more delicate detail on top plus the bass is a bit fuller and deeper. These M-4s match very well with ADS speakers by the way!

Yamaha T-2 (rebuilt and aligned), Yamaha C-2x (original and works perfect), Technics SL1200MKII with AT440MLb, Nakamichi RX-505, ADS L420 speaker, all Avanti interconnects and speaker cables.

 

[avionic]

https://www.mcmaster.com/#93657a230/=1d0iwbf
or
https://www.mcmaster.com/#94669a119/=1d0ixyv

 

[stoutblock]

https://www.mcmaster.com/#93657a230/=1d0iwbf
or
https://www.mcmaster.com/#94669a119/=1d0ixyv

Yeah, that would work also (for the spacers).

 

[avionic]

Yeah, that would work also (for the spacers).

For those who are not mechanically inclined..

They are also available in stainless steel.
https://www.mcmaster.com/#92871a201/=1d0jhxl

 

[ChristopherP]

Thanks for the write up, stoutblock. Love hearing that is sounds better than the one I listened to with you the other day. Really looking forward to getting this hooked into the C2/T2 package you already fixed me up with. As the front amp for my Atomos system, and power amp for my 2 channel stereo, I’m sure my LS50s will sound fantastic. I hope folks will be able to use your M4 experience with this and your other builds to enable more of these fine amps to be appreciated far down the road. You and Avionic are doing us all a solid keeping this great Yamaha gear running.
Best, Chris

 

[Mr. Yamaha]

Great work! Neat mod on the bracket

 

[stoutblock]

Great work! Neat mod on the bracket

Thanks! This is the third bracket I have done like this. It is fairly easy to do and seems to do the job at keeping those big cans from damaging the PCB.

 

[stoutblock]

Well I have finished amp #6 for Chris. I used Furutech Alpha-18 (AWG18 OCC) hook up wire. You can see the new relays in this photo.


Vampire speaker posts fit perfect!

 

[ChristopherP]

stoutblock those latest pics show the M-4 better than new. It was the right decision to add those Vampire posts.
keep us posted on how #7 runs.

"don't panic"
- Doug Adams