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Chip Amps Amplifiers based on integrated circuits

The best sounding audio integrated opamps
The best sounding audio integrated opamps
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Old 19th October 2016, 11:11 AM   #2291
AndrewT is offline AndrewT  Scotland
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I also have the 389s for these PCBs.
But can you trust your post to allow them through customs?
You can fit a pair of closely matched LSK170b into thses PCBs.
I have a very few supermatched pairs.

I went with the B1 XO using unity gain followers as the S&K filters
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Last edited by AndrewT; 19th October 2016 at 11:16 AM.
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Old 19th October 2016, 04:30 PM   #2292
Carl_Huff is offline Carl_Huff  United States
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Quote:
Originally Posted by carlmart View Post
Hi Andrew,

Thanks, but those pcbs had a 2SK389 at the input, which is expensive and rare nowadays.

They looked like very promising indeed.


Carlos
Carlos,

You can edit the PCB layout to accept NEC uPA68H matched FETs. Salas is doing that on his DCG3 preamp here on DIYAudio. I took his suggestion and mapped the uPA68H into the MOX op amp and configured the circuit as a 2520 DOA plug-in. It works very well.

AndrewT,

I appreciate your offer. The MOX project that you describe makes for a very nice active crossover. However in my case I have adjusted the packaging of the MOX op amp to be a '2520 plug-in' and recreated the Linkwitz-Riley circuit using them.
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Last edited by Carl_Huff; 19th October 2016 at 04:32 PM. Reason: Grammar, grammar, grammar ...
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Old 19th October 2016, 05:41 PM   #2293
carlmart is offline carlmart  Brazil
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The question is where to get them if they fail, and that's not so difficult to happen.

If I am not wrong, the uPA68H came in the top Luxman power amps from the early '90s. Superb amps. A friend of mine has one.

The dual FET was hard to find when it blew. It came on a piggy back board that Luxman used, sometimes encapsulated.

In the case of those discrete ICs that were mentioned, I got to get a schematic, This uses two K170s. and a trimmer to balance DC offset. It should drift, though.

A cap or DC servo might be necessary to block DC offset. But you can use higher voltages.
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Old 19th October 2016, 05:51 PM   #2294
carlmart is offline carlmart  Brazil
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These are the discrete ICs:

New Dual Channels Full Discrete Op Amp Module Replace OPA2604 LME49720 | eBay
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Old 19th October 2016, 06:02 PM   #2295
Carl_Huff is offline Carl_Huff  United States
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You can still find uPA68H as NOS (New Old Stock) if you go looking for it. You will pay roughly $2 each in small quantities. Of course the LSK389 is back in production, this time by Linear Integrated Systems.

The best place that I have found to buy them is here: https://www.trendsetter.com/Transistors-s/23000.htm
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