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Post by rowmat on Mar 6, 2016 19:10:40 GMT -6
I'm thinking about picking up a Urei 546 stereo parametric EQ. They seem to crop up fairly regularly and I can pick one up for around $650 USD. I know they use pretty slow low bandwidth opamps and the EQ will benefit from a recap but I'm thinking about replacing the opamps with something sonically nicer and maybe upgrading the transformers with Jensen/Lundahl/Sowter's etc. Does anyone have much experience with these EQ's and if so do you think such and upgrade would be worthwhile? Cheers!  |
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Post by mhbunch on Mar 6, 2016 23:49:37 GMT -6
Not worth it IMHO.
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Post by jimwilliams on Mar 7, 2016 10:46:59 GMT -6
Those are rebuilt here. One recently sold for $1200, post mod. I use low noise opamps, remove all the signal coupling caps, add filter bypass caps, replace the mylar film caps with polyprop film and the output stage gets higher current, faster power transistors. The output transformer can be left in or bypassed.
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Post by rowmat on Mar 7, 2016 15:18:19 GMT -6
Thanks for the info.  |
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Post by rowmat on Mar 7, 2016 15:31:45 GMT -6
Someone thought it was good enough to go to the trouble of designing a DIY clone... www.pdf-archive.com/2011/10/12/eq-public-doc/eq-public-doc.pdfHowever even I wouldn't take it that far. If I can pick one up for not too much I'll try it out and see what I think. If I think it has potential I'll modify it or re-sell it if I think it doesn't.  |
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Post by rowmat on Mar 12, 2016 1:24:20 GMT -6
I just picked up a Urei 546.
It's very clean.
I took a peek inside and all the IC's are socketed and are TL084's instead of the original 4741's.
I'll stick it on the scope and run some tests before I start playing.
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Post by rowmat on Mar 12, 2016 5:38:25 GMT -6
Those are rebuilt here. One recently sold for $1200, post mod. I use low noise opamps, remove all the signal coupling caps, add filter bypass caps, replace the mylar film caps with polyprop film and the output stage gets higher current, faster power transistors. The output transformer can be left in or bypassed. Hi Jim, I've been looking for suitable opamps to replace the TL084's that are fitted to the Urei 546 I picked up in Melbourne (Australia) today. The manual specified 4741's but obviously they have been changed for the TL084's and are socketed. It appears the LT1359 is no longer available and the LME49740 is being discontinued. Would the ADA4898 with a DUAL > QUAD adaptor be a suitable replacement? www.mouser.com/ds/2/609/ADA4898-1_4898-2-541072.pdfThanks. |
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Post by jimwilliams on Mar 12, 2016 11:05:16 GMT -6
LME's work well if you can find them. You need to add feedback phase compensation caps for wideband opamps. The mylar caps need to go. The IC sockets need to be lower profile machined. The resistor arrays need to go. The carbon film resistors need to go. Ouput transistors should be faster and wide band. Filter bypass switches need to be installed.
In other words, you keep the case and replace everything else. Poor man's GML.
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Post by rowmat on Mar 12, 2016 13:06:11 GMT -6
LME's work well if you can find them. You need to add feedback phase compensation caps for wideband opamps. The mylar caps need to go. The IC sockets need to be lower profile machined. The resistor arrays need to go. The carbon film resistors need to go. Ouput transistors should be faster and wide band. Filter bypass switches need to be installed. In other words, you keep the case and replace everything else. Poor man's GML. Thanks Jim, Funnily enough a "Poor man's GML" was more-a-less what I had in mind when I was looking for a dual parametric EQ. Cheers |
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Post by rowmat on Mar 12, 2016 14:46:58 GMT -6
Mouser no longer lists the LME49740 while Digikey has none in stock but can backorder a minimum of 150 units!
There are some LME49740's on eBay but at around double Digikey's pricing.
I have no doubt the counterfeiters are working overtime churning out fakes of many of these discontinued devices.
I just took the plunge and ordered 150 LME49740's from Digikey.
I can use up 30 immediately on a few pieces of gear and what I don't use I'm sure will be easily resellable as the last stocks of these IC's dry up.
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Post by wiz on Jul 4, 2017 3:23:04 GMT -6
How did this end up?
Cheers
Wiz
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Post by rowmat on Jul 6, 2017 18:36:04 GMT -6
How did this end up? Cheers Wiz In a nutshell it ended up down the list of priorities so has been mothballed until I have less urgent stuff to do. |
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