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In Reply to: RE: OPA 627 posted by danvegso on March 17, 2010 at 07:09:56
Hey Dan and Reb - thanks for this great discussion. I have samples on the way of 1611, 1612, 2107, 827, 2211A and 2111. I ordered a SOIC-DIP 8 adapter from Brown Dog, too. I have a 627 here already that I haven't yet plugged in since I am still getting familiar with the 2132A.
And I can't recall if I mentioned that I am using this in an old Belles DMM pre that I have modded pretty heavily (and BTW it sound FANTASTIC in my system).
Here is another question for y'all. I ask this knowing full well that it isn't answerable directly.... I have a new Quad 99 pre. It has 12 OPA275s in it. I am toying with the idea of pulling them all and installing sockets to put new/better opamps in. I don't have a schematic, so I can't tell you the specific uses of the opamps in the circuit, but in a general sense, what would you recommend as replacement/upgrades for this? I am also going to try to ask Quad directly, but I don't anticipate getting an answer.
Thanks
Follow Ups:
Hey bevo!
Quite a fun discussion, eh?
Looks like you'll have quite a collection to do some op-amp rolling!
Was the 827 off backorder yet?
You will really need a schematic to play with the 99. Looks like it's about majority IC, with few discrete components. It would be pretty easy to upset the "balance" of things.
I couldn't know which to start replacing first, or with what, until you know "what goes where". I don't know how cooperative Quad is at providing schematics to non-techs, but it's worth a shot.
Nice project, though. Good luck!
Dan
Yes - it has been fun for me. This is my first time to play around with opamps. Yes, the 827 is on BO until 1st week of April. A couple others are on BO as well..
I sent a message to Quad - we will see what happens. I have already voided the warranty by replacing all the crappy 'lytics with Nichicon FGs in the power supply and Mundorf nonpolars in the phono stage. Also replaced both rectifier bridges with new ones from Fairchild. The PCB is not the best quality - lots of traces separated just from desoldering/resoldering the caps. And there were even trace separations that the factory had repaired before I even touched anything. Even though I did exact replacements for capacitance (higher V rating, though), something went wrong and it won't pwer up. From what I can tell from the PCB test points, I have lost 2V on the - power leg. The toroid output is correct, all fuses are good and the resistors I have measured are all good. I am afraid a regulator has gone bad somehow/somewhere.
I am anxious to get it up and running to do a head-to-head with my Belles. I think the Belles is winning, even with the OPA2132A...
Yep, I think that the opa1612s are b/o as well, but I thought that they were a mid March availability. I'll have to check my invoices.
While you were digging in to things, did you replace the resistors in the phono stage? I recall an old Quad preamp mod was to replace them all with like-value 1% metal film from Holco, Vishay or other "high end" ones.
Did you also do a bypass of all of the 'lytics with HQ PP/PS/whatever caps?
re: board quality-no surprise here...I've opened up a few "high end" components and had one of those WTF moments in regards to build/material quality. I've (luckily) never had a trace lift, but it has to be exasperating.
At least the regulators look to be up front and easy to test/replace.
My suspicion is that the Belles will win in any case. As has been said many times before;"The best op-amp is none at all." By extension, the fewer, the better.
Remembering that the Quad equipment (at least the ones with which I'm familiar) were "voiced" to match/compliment the Quad speakers. By design (and intent) they seemed to showcase the lower midrange to mid/upper-treble range. Extreme highs and bass were less important. This is based on old knowledge with the ESL57/63 and Quad electronics through the model 77.
This might well have changed over time and with customer request/marketability....
Happy Hunting :-)
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