Discussion in 'Yamaha' started by Bratwurst7s, Sep 30, 2017.
And the CD buffer and Input section and an overview of the amp put back together...
Great and nice job, James Bravo!!
Very nice work, James. I lost the overview a bit, may I ask which type of 6800 µF Mundorf caps you used for the PS? Was it a drop-in replacement?
I see the old NCR 5532. Why not replace them with more modern OP Amps like the OPA 1612?
Last photo, a blurry shot of the first power up.
A couple of last thoughts.
Concerning the relays. In spite of buying new ones I considered Restorer-John's advice and decided that it the smartest thing that I could do was listen. So I left the 3 blue relays in place undisturbed.
I thought long and hard about deoxiting the pots and switches. And elected to leave them as is. They were all dead quiet before and I decided not to disturb them.
In spite of building up a replacement bridge rectifier out of those ultra fast soft recovery diodes I decided to wait on that. It's best to just do the straight recap and listen before taking another step. The only deviation that I took from a straight re-cap was to add the little Wima 0.1µF film caps to bypass (almost) all of the signal path caps. "Almost" because I got dumb and forgot the caps in the phono section.
After putting the pre back in place and hooking it up I did a no input sound check. If you can call dead silence a sound check. Looking at the volume knob as a clock my normal listening level is around 9:00 to 9:30. And that's pretty loud. Going up to 10:00 is as much as I can stand. So with no input I turned the amp up to above 12:00. With input the police would be here in short order but I wouldn't know it till they kicked in the door 'cause I'd be deaf. In this case it was as if the amp wasn't turned on. Dead silence, with every switch and pot cycled.
1st listening test. This just put me straight into the grin zone. Bass is tighter. Everything is tighter. The music just has more life. Piano sounds like it's in my living room. Freaking aewsome! I'm very happy about how this turned out.
That's all for now.
edit: I forgot to state earlier: Every single solder connection in the entire amp was re-flowed.
edit 2: I also forgot something else. It probably is overkill but I measured every set of caps and in every case where there is a L&R pair chose pairs as closely matched as possible.
Thanks! The Mundorf's are Mlytic AG 63v. Here's a link to where I bought them...
Yes, drop in fit. The leads just fit snugly in the inner ends of the original slots. Nice and easy.
edit: That Bonzai price is about the best that I found and they've proven to be a reliable source for odd caps.
Perhaps at some time in the future. I have about 100 of my favorite LME49720's sitting around and plenty of gold plated sockets. But I decided it was best to do only one change at a time and evaluate the results.
I know the LM 49720 and I used them . I used the LM4562 as well .Someone says they are identical.( http://www.diyaudio.com/forums/chip-amps/107344-lme49720-vs-lm4562.html )But ,believe me the LME 49990 and the OPA1612 sound wonderful. They are much better
Afaik the LM 4562 is a low cost version of the LME49720. I haven't used the LME49990 or OPA1612 but since you are recommending them I'll add them to my list of op-amps to try out. I've used the OPA2134 and OPA2107, of the 2 I much prefer the 2107.
Thanks! It was fun. And we all know the reward.
A couple of follow up items.
Over the next few days I'll finish the parts list spreadsheet that I've been working on. When it's done I'll be posting it on the first page of this thread.
Also, I haven't forgotten working on getting the schematic and layout scans added to the AK database. That should happen within the next week or 2. In the meantime if someone needs them before then PM me. Be aware that your emale account must be able to handle attachments of 55mb. 3 files that size.
I do not know the OPA3134, maybe you meant OPA 2134 (with these acronyms it's easy to make mistakes ). I have them too, but in the field of FET's Op Amp the best are the OPA 627 and OPA 827. I bought several on Ebay on 8 dip adapter are authentic and sound great. But it is a matter of taste; someone prefer bipolar someone else FET.But the LME49990 ( bipolar) fly like a eagle over them . I do not know the OPA 2107 but I read from the datasheet that are of the DFET Op Amp
Oops. Yes, I meant 2134. Thanks. I'll edit my above post.
You have me curious now. Perhaps I'll have to buy some of the LME49990's and try them in my cd player. I have some of the LME49720HA/NOPB (TO-99 form) in there now.
Bummer. The 49990 is out of production.
edit: But mouser has the OPA 1612. The price isn't bad at all. Thanks for the recommendation BG. I'll order some with my next Mouser order.
Yes I know but you can find them ( if you do not have trust in chinese's ebay sellers) as NOS on Ebay.us aka Ebay.com from US sellers. about OPA 1612 http://www.ti.com/amplifier-circuit/op-amps/audio/soundplus.html#Ultimate
and LME49990 http://126.96.36.199/pdf/0/4/3/1/9/04319768.pdf
Note concerning Wima caps. For the 10µF/50v use Mauser part number 505-MKS2B051001NJ00. These are 5% (measure more like 1%) and have long leads, something like 20mm or longer. This is a definite improvement over the earlier ones that I've bought that had pretty short leads (ca 10mm). It makes a huge difference when fitting them into a tight spot.
Also, by the end of this month I'll have the finances in place to start work on my M-70. Expect a thread start soon.
James, outstanding work and documentation! The CX-1 is a terrific preamp.
I just had my second listening session. Tonight I set the WayBack machine to 1970 and 1975. Steve Stills 1st solo album and Little River Band's first album.
Now I know this is a tired cliché, but it feels like a veil has been lifted from my system. All of us that have gotten to know how our system sounds can notice a subtle change. In the last 2 months I've gotten really attached to this pre-amp. I really liked it's sound from the start. Quite an improvement over the pre-amp section of my AX-1090. The change in SQ from last week to this week with the CX-1 is not subtle. There is a serious improvement after re-capping.
You are correct, I agree strongly that this is a terrific pre-amp! I can hardly wait to get a serious power amp attached.
Hmnn. Not to get into the "burn-in" debate, but sometimes I wonder. Do you suppose that the burn-in phenomenon is nothing more than elcos re-forming slowly in their actual working environment as equipment is used?
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