Cooking With a Yamaha C-4

Hum. If its the transformer . Not much you can do about it. Other than replace and hope you find a quieter one.
Make sure all the transformer fasteners are tightly secured.

Thanks for the tip. Will check it out. Gonna do some listening first!
 
Please report here on the comparison between recapped re-freshed C4 and C4 "original". Many folks have spent lots of money on exotic caps, lots of time replacing original with them and report little or no change in sound or rather no real improvement. Others however have reported day and night changes in sound - improvements mostly. same holds for replacing caps in crossovers. Its an ongoing discussion and varies with components and other parameters I'm sure.
 
Please report here on the comparison between recapped re-freshed C4 and C4 "original". Many folks have spent lots of money on exotic caps, lots of time replacing original with them and report little or no change in sound or rather no real improvement. Others however have reported day and night changes in sound - improvements mostly. same holds for replacing caps in crossovers. Its an ongoing discussion and varies with components and other parameters I'm sure.

The preamps are a C-6 and a C-4, not two C-4s. The C-6 was recapped by avionic a year or so ago. The C-4 is still original, so I don't know (yet!) what it sounds like recapped.

The C-6 sounds great, but I only plugged it in to see if it worked before sending it off, so I don't know what it used to sound like.

Wish I could offer more insight, but the bottom line for me is that both units sound terrific and neither's going anywhere soon.
 
caps, lots of time replacing original with them and report little or no change in sound or rather no real improvement. Others however have reported day and night changes in sound
A big benefit of recapping a unit is that it lets you go over all the solder joints, many cold/cracked in old gear. The corrosive/conductive glue doesn't help either.

There can be audible improvements just from retouching all solder joints and setting adjustments. I tried this separately (i.e. removing glue and resoldering entire boards) then listening, before recapping and listening again, and both steps had audible benefits.

IMO if the solder joints and glue aren't dealt with (and any out-of-spec electrolytics) the gear often doesn't sound as Yamaha intended, rather a butchered version of it. But if you are doubtful, the only way to truly know would be to try it on a few pieces of your own. Since these degradations vary from amp to amp it makes sense some would see more improvement than others.
 
Part of the issue in my case may be old ears that are now paying the price for a misspent youth listening to lots of loud live rock 'n' roll.

A big benefit of recapping a unit is that it lets you go over all the solder joints, many cold/cracked in old gear. The corrosive/conductive glue doesn't help either.

There can be audible improvements just from retouching all solder joints and setting adjustments. I tried this separately (i.e. removing glue and resoldering entire boards) then listening, before recapping and listening again, and both steps had audible benefits.

IMO if the solder joints and glue aren't dealt with (and any out-of-spec electrolytics) the gear often doesn't sound as Yamaha intended, rather a butchered version of it. But if you are doubtful, the only way to truly know would be to try it on a few pieces of your own. Since these degradations vary from amp to amp it makes sense some would see more improvement than others.
 
I see I have a pack of 680ohm resistors that look just like that one, with two missing... I worked on two CR-2040s... May be a connection.

Part of the issue in my case may be old ears that are now paying the price for a misspent youth listening to lots of loud live rock 'n' roll.
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Nuff said..:biggrin: Bad tinninitis. I'm always hearing mosquitoes..:biggrin:
 
I haven't heard any differences after re-capping. I consider it maintenance. You may wish to look into replacing the "slant-back" Hitachi branded 2SC458 transistors and the VD1212 diodes for maintenance reasons as well.
 
I haven't heard any differences after re-capping. I consider it maintenance. You may wish to look into replacing the "slant-back" Hitachi branded 2SC458 transistors and the VD1212 diodes for maintenance reasons as well.

Is there a particular reason, apart from maintence, to replace the transistors and diodes?
 
These are known failure parts based on the years of repair work the techs on AK have done. If your unit doesn't have problems, it might if these items are in the unit. Only 1 type of 458 transistor was called out by one person. Most talk about blanket replacement but they are not the techs, they are the AK faithful with a hot soldering iron looking for anything to replace while they are in there.
 
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In the instance of the specifically mentioned 458s those caused noticeable noise on my Sansui 2000a and many others have reported the exact same thing.
 
In the instance of the specifically mentioned 458s those caused noticeable noise on my Sansui 2000a and many others have reported the exact same thing.

Thanks for the info -- I learn so much here.
 
Could also be DC on your mains, which makes transformers hum worse.
You could add yourself a mains DC blocking filter, or use a mains filter unit with DC blocking facility like this one:
https://emotiva.com/products/accessories/cmx-2

Yes, I've heard of these. Honestly, it's so soft I don't really notice it. In fact, I'm listening to it right now -- Cannonball Adderly -- and it sounds fine.
 
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