Recap a Yamaha C-2X preamp

[energyandair]

Is this really true of all Yamaha preamps? My C-4 has two sets of pre-outs, and I use the second set for my sub. It doesn't sound out of phase with my main speakers at all. I can't find anything in the manual that says they are inverted either.

Its true of some but not all.
In my C2 they are in phase (enables you to run one amp for bass and one for treble)
The manual for the C-2a says they are in parallel (in phase)
In the C-80 (a later pre-amp) they are out of phase (enables the bridging trick)

David

 

[Yamaha B-2]

i'm The the signal pins for both pre out 1 and 2 are directly connected on the PCB and therefore cannot have different phases.

Maybe the U.S model is different. An easy way to check is stick the multimeter probes into pre out jacks 1 and 2 for the left signal and check for continuity, then again for the right. If they're connected then they can't have different phases.

You are correct. When I read the schematic earlier the 1 for outputs 1 have the numerial by the lower jack in the schematic, while the lower jack for outputs two has the 2 next to it. I mistook this for the meaning that it was RCA 1 on one set and RCA 2 on the other. So they are in phase and I have to go back to experimenting with my sub location. Ah, well. Life is never that easy.

 

[morksbeanbag]

About the B-2x, RUN! And don't stop until you have it in you're arms. And when you have, don't let go again.

It was part of Yamahas statement setup with the C-2x, it is a full dual-mono amp. Some say it is better than the B-1 and B-2! MX-2000? I also believe it is more rare than the C-2x.

Got the B-2x today. Its filthy, faulty and has a broken speaker terminal. I've spent the last 6-7hrs stripping it down, washing all the casing, removing the power amp boards from the heatsink and washing the heatsinks too.

Its no wonder it didn't work for the guy. I found 2 blown resistors on the left hand power amp pcb and about 30 dry joints dotted all over the place. Its not been taken care of but the casing is fine now its clean. I can't tell if the two transformers are toroidal as they are in very hefty epoxy filled casings.

The build on this B-2x makes my Sony ES gear look like childrens toys. Those 4 22,000uF caps are huge, like the size of beer cans.

Wierdly again parts of the PCB have black gate caps fitted and when i look online at pics of the B-2x board i see other people's have black gates in exactly the same places as mine. Did Yamaha used to fit black gate caps as standard?

One other bonus was the power amp came with new WBT rca's. I've no idea where to source a new B-2x speaker terminal though.

 

[the-real-mandak]

I don't think Yamaha ever used Black Gates, it would be the first time I hear about it.
Try to look at this page and compare (it takes a while to load, use Google translate): http://amp8.com/tr-amp/yamaha/yam-b2x.htm

The important cans are not the big ones, try to look closer on those on the side you might get a chock.

About the speaker terminals, try Nakdoc or Fred Longworth.

OH and pics of those Black Gates!

 

[Yamaha B-2]

Good for you. But, :worthless

Especially want to see pic's of the Black Gates.

 

[morksbeanbag]

ok ok, i'll load on corel photo paint and get the camera hooked up this afternoon.:yes:

 

[morksbeanbag]

some B-2x snaps

Here's a few first snaps of the B-2x in the process of cleaning and repairing.

 

[the-real-mandak]

I think you can glue the speaker terminal together again, did you see the link I posted before?

 

[Yamaha B-2]

Yes....very nice. The B-2x was Yamaha's statement amp at the time. MRSP was $1500 compared to the contemporary M-85 with an MRSP of $1100. Obvious that plenty of good thought went into the modular design of same. Is it bridgeable? I would like to have one to drive my sub.

Will have to do a bit of research on that Black Gate question. Not sure they were around back then.

 

[the-real-mandak]

The patent on the BG is from late 70´s if I remember right, see the link I posted in the old C-2x thread.

A B-2x to drive sub's?, one of the finest amps ever from Yamaha. B-2 :nono:
use a M-80/85.

 

[morksbeanbag]

I think you can glue the speaker terminal together again, did you see the link I posted before?

Hi,

i saw the link. I can't really figure out what he was doing with the terminals on there, just looks like he filled it with sealant. :scratch2:

I think i could fix mine with plenty of epoxy resin. They're nice speaker terminals but only accept bare wire. I want to use banana plugs if i can really.

I can't see anything obvious about bridging. I think its too good for using on a sub.

If you go down the page of the B-2x being modded you can see he has taken out the black gates on his amp. I've checked the markings on the black gates on mine and they are EXACTLY the same as the ones in the pot of old caps/trim pots he took out. I'm sure now that Yamaha used black gates as standard in certain parts of the B-2x and C-2x. They look old now on my boards. Will a new nichicon fine gold be better than an 20 year old black gate?

 

[the-real-mandak]

Hard to say, but I don't think so. The BG's use graphite as insulator, which is the special thing about them.

Do they say Black Gate on them, not just Black?

Go here to read about BG's: http://www.acoustic-dimension.com/blackgate/bgmain.htm
I can't find the story´at Audio Note anymore, but the rest is there.

Speaker terminals: I think he is making them stronger and the stuff he is using looks like glue from a glue gun. You know the stuff you heat so it becomes fluent, it is quite strong and a flexible.

 

[morksbeanbag]

They say "Rubycon Black Gate F"

So i guess F is the series they are from.

Just seen the large caps on the amp boards are 100,000uF!

Here's a pic of the chassis and power supply now scrubbed up and polished. Ready for parts going back in.....when they're ready. Might be a while.

 

[the-real-mandak]

Still please make a pic of the board with the BG's, and then I can check with my unit.

 

[morksbeanbag]

I take it you mean for the C-2x

Here's a pic of the C-2x with the location of the black gates i suspect are fitted standard.

 

[the-real-mandak]

Really nice pic but no, I ment the B-2x.

PS. I only list the units in current setups, not my stock.

----EDIT----

See this; it is a Rubycon Black, not BG. I might have to take my C-2x apart again to look. But I think merrylander would have noticed if there was BG’s in the C-2x when he re caped B-2's C-2x (phonostage): http://audiokarma.org/forums/attachment.php?attachmentid=14872&d=1146677733

 

[morksbeanbag]

If you meant the B-2x then look at the 3rd pic along in my first set of pics. That shows where the black gates are on the power amp board.

 

[morksbeanbag]

double post-oops!

 

[the-real-mandak]

Cool THX.

 

[Yamaha B-2]

Really nice pic but no, I ment the B-2x.

PS. I only list the units in current setups, not my stock.

----EDIT----

See this; it is a Rubycon Black, not BG. I might have to take my C-2x apart again to look. But I think merrylander would have noticed if there was BG’s in the C-2x when he re caped B-2's C-2x (phonostage): http://audiokarma.org/forums/attachment.php?attachmentid=14872&d=1146677733

Credit where credit due......merrylander did the work on wajobu's Yamaha preamps. EW did the work on mine.

To answer your previous question about Nichicon Fine Gold as compared to 20-yr-old BGs, I would definitely go for the new Nichicons. New design, new materials, etc., = better caps.