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Help I need to locate a part

I have owned Spectral amps DMA 50, 80, and still own a 90.
(I find the Audio Magic digitals sound like the 80)
Spectral, when last I spoke with them would not touch something if anyone else had been in it. This was in the days when they told folks that non-MIT cables could damage the amps.
I had a chip in the 50 blow, and an ex teck named Crosby helped me locate it as he and spectral had bought out the market on that chip.
Well, my 90 is literally giving me static and my current teck needs to
replace the I.C. and we really need to locate, either:
*the chip,
*any contact info for Mr. Crosby (who might know the chip intimately) or
*someone who knows cross referencing and may know a better alternative to
a very hard to find chip.
I'm not technical when it comes to circut specs.
But this is the info on the chip:

number NPD5566.
The other number which we believe is a date code only is M9384.

So if anyone can please help me, email me any leads, I will be very
grateful.
This amp already has upgraded RCAs, binding posts, I.E.C. input and output
wire, and is sounding closer to the next version as well as nearly like
the next size up.
Thank You all in advance for any assistance you may provide.
Spiro
spiro

Showing 2 responses by kirkus

kirkus
502 posts
 
Spectral, when last I spoke with them would not touch something if anyone else had been in it.
Wow, that's really lame support. If I was in their position, I'd WANT it back so I could be sure that it was working the way it was supposed to. Of course if somebody had made a mess inside I'd charge accordingly . . .

But for your part. IIRC this is the same as a 2N5566, which is a dual matched JFET. If you google it into the ground, you can probably find one. If not, you might contact Erno Borbely, he's passionate about using matched-JFETs in his own designs, and may have some ideas for substitutes. Also there's a company called Linear Systems that makes matched JFETs . . . I've tested some of their samples and they seemed to work well.

www.borbelyaudio.com

www.linearsystems.com

If your technician is making substitutions, make sure that he/she is properly equipped to check for parasitic oscillations at a wide range of frequencies and power levels. Checking for IMD isn't a bad idea, either. I'm assuming that Spectral is using this part in an input differential amplifier, so substitutions/problems here can definitely affect performance.
kirkus
502 posts
 
Rodman, your link is to an OPA627, and that's an opamp, NOT a dual JFET. They're, uh . . . different. Using it as a sub would be like trying to substitute a brake caliper for a carburetor.

These things were kinda in vogue in the early 1980s, and were used in some Urei compressor/limiters. Last time I worked on one, the 2N5566 was out of production and a pain in the butt to find -- and that was well over a decade ago. But that was also in the Internet's relative infancy, so it may actually be easier to find these days.

Subbing small-signal JFETS in a power amplifier is NOT a journeyman-technician's task . . . best left to somebody very experienced - "JFET-rolling" is a very bad idea! Small differences in junction capacitances from one type to another could at best make the amp not sound like it should, or at worst turn it into a power-oscillator, destroying both the amp and any speaker attached.

I'm still blown away that Spectral won't give factory service for your amp - that's absolutely the best option.
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