CX-766 - obscure BBD

[MrStab]

hi guys,

just thought you guys might be interested in this. I was watching a YouTube video about the Kenwood RA-80 hifi reverberator (why the f-?!!!!!), and my curiosity peaked when it was mentioned that this unit wasn't a spring reverb. So i looked up a diagram, used bugmenot dot com to get past some stupid website's registration process, and found out the chip is labelled CX-766. Made by Sony, as far as i can tell.

this seems nigh-on impossible to come by, or to find any documentation on. maybe some of you guys know about it? were there any others made in the series? any interesting spec info, compared to the MN3007 etc.?

[anotherjim]

You can't rule out the power of something as big as Sony to have existing chips made with their own numbers and logo. The CX prefix is one Sony was known to use for CCD based cameras, but back in the day, CCD was synonymous with BBD. So it could be a Panasonic MN series behind that part number.
Sony also liked hybrid modules in consumer products, so a CX-766 could be a complete delay module in a single package in the same manner as the STK power amps they used in their hi-fi's.

[MrStab]

given the scarcity of documentation, rebranding makes a lot of sense. This seems to be a 14-pin chip, though, whereas the other popular BBDs i know of/have googled are either 8 or 16-pin.  i'm not too into BBD's myself, so i'm not that clued up on them.

not sure if i can get away with uploading the actual PDF, but you'll be able to search for that easily.

[Mark Hammer]

Differentiating between a BBD, and an epoxied module containing a BBD, can be done by looking for HF clock lines from somewhere else in the circuit.  But yeah, that's a weird one for sure.

[MrStab]

But yeah, that's a weird one for sure.

totally. why the hell would you want reverb in your hifi? lol

[anotherjim]

The simplicity of the circuitry around the bbd "chip" makes it more likely it's a custom hybrid. It was very popular in the late1970-1980 period and was an early use of surface mount tech before it was found on complete pcbs. Bare IC chips are assembled on a ceramic base together with other components to make a complete sub-circuit. The edges of the base has pins clamped on and were usually in SIL or DIL format with standard 0.1" pitch. A shiny resin encapsulation was usually added to seal the circuit in, but they were also found in bare form. The ceramic base is very brittle and they rarely survive being pulled from the pcb.
Hybrid devices still get made and you can find some IC datasheets showing an unbonded chip "packaging" option for that market. Also things like the melody chip in a greetings card under a black resin blob?

[MrStab]

interesting stuff, i had no idea that was a practise. i've definitely seen those blobs in simple stuff before. if it were something you could easily salvage from old equipment, i'd imagine i'd have heard about the IC sooner.

[willienillie]

why the hell would you want reverb in your hifi? lol

A buddy of mine had one of those back in the day.  It sounded awful, he was actually using it.  I insisted that he turn the effect off, pretty sure he never turned it back on.  We're still friends.

[anotherjim]

Reverb in the home hi-fi? In Japan, nothing is safe from Karaoke!

[MrStab]

Here's the video:

i like this guy's channel - it's a refreshing change from all the hands-on electronics stuff, plus there's loads of crazy formats i never knew existed. that display does look pretty awesome.

[idiot savant]

I remember looking for info on those awhile back.

There's some info here:
https://audio-circuit.dk/wp-content/uploads/simple-file-list/Nikko-ATDI-td-sm.pdf

A mini datasheet, and some info on the cx766 in there. 1024 stage, 3 output taps.

[MrStab]

nice one, Savant!


could this still be a custom hybrid thingy, Jim?

[highwater]

Reverb in the home hi-fi? In Japan, nothing is safe from Karaoke!

Don't be hating *too* much... karaoke reverb'll keep the PT2399 around for sure.

[MrStab]

tbh i think the PT2399 would make an audiophile have a heart attack

[Rixen]

nice one, Savant!


could this still be a custom hybrid thingy, Jim?

don't you just love the big wide curved tracks that was so popular before ecad ?

[anotherjim]

nice one, Savant!


could this still be a custom hybrid thingy, Jim?

No, now it's much more likely it's a production DIL IC - like a TDA1022, but different! You have found a rare one.
What made me suspect it was a hybrid was the lack of 2 output phases in that first scheme and no pre-post filtering nearby. That Nikko scheme has all the usual support circuits for a BBD chip and, of course, describes the bbd with the internal block diagram.

[MrStab]

Savant found it first. he is the superior Googler.

so i guess this is just a curiosity at best, or could it be worth looking around for different products which used this IC to see if they're reasonably available for a few DIY one-offs? i know some people, people with a lot more patience than me, like to desolder old chips.

[duck_arse]

nice one, Savant!


could this still be a custom hybrid thingy, Jim?

does no-one else think it odd that the pin numbering is backwards to convention?

"thick film hybrids" - that used to be a thing. if you seek out the disection page for the fuzzrite, somewhere on the mojo wires, there is a Sprague hybid module to look at.

[anotherjim]

I assumed it was backwards as it's how the component overlay was presented looking from the copper side - tho I'm not sure.
Blaupunkt stuff used to have 2 or 3 hybrids in them, mostly in radio or tape (dolby) sections. They were the bare (and most brittle) kind with blobs over the IC chip if there was one.

[duck_arse]

ahhh, reversed mirror under image, for the help of the technician. I see; makes sense.