Spectra-Sonics 110- layout "from scratch". opinions, interest?

[JoshuaUnitt]

Hey folks,
I toyed with the idea of grabbing a few Spectra Sonics 110 cards off ebay to rack up but ultimately decided it might be more cost-effective (and educational) to start over and make my own layout. Here's that, for starters-

First off, I'm very inexperienced with doing layouts. My software design rules checker isn't beeping any errors out at me, but can anyone with some more experience spot anything blatantly wrong design-wise?

Second, if I were to have a few of these made, would anyone else be interested?

 

[mutterd]

Wow, this is pretty ambitious…

as for the layout - I would put all the I/O connections on 1 side - or at least the output +, the output -, the DC signal out and the feedback point. If you were to hook up a spectra EQ with one of those you'd either do it between the output + and the feedback point or the DC signal out (thru a 10uf tant) and the feedback point - and the termination on both ends of this is kind of tricky… since the + and - side of the eq are hung off a 5.6k resistor to ground, so those wires have to be as close to the same length as possible or the impedance differences can cause things to be screwy…

also remember that ground is NOT continuous thru the card - so input negative and output negative both have to be grounded, ideally to the PSU ground, or the amp will not work.

all the resistors should be RN60D's, or something similar - and all the places that there are pairs have to be well matched…

the hardest part is going to be the transistor pairs… they aren't really plug and play - if you're going to do it - id suggest getting a few hundred of each, setting up a jig, and testing them to match the actual hfe (beta) otherwise there might be some smoke!

finally - R1 should be 604 for best overall performance, but if not - the 2.74 should actually be 2.4k…

when flickinger first got started building consoles he used SS cards - 101's mostly - I guess he tried for a while to fabricate his own 101's but could never get it together - so don't get discouraged if it doesn't happen as easily as just buying a mouser cart and stuffing the board - i think success is a balancing act dependant on very closely matched pairs…

but keep us posted for sure!

what transistors are you going to try?

 

[JoshuaUnitt]

Lots of info to digest, thank you so much for the input!  Most of this makes sense, and I plan to get start with revising the board to make accommodations soon. For transistors, I have a few threads bookmarked on here on what other people have gone and done since I can't find a single online supplier for the original stuff. I may also try to seek out some NOS electronics stores while I'm visiting the big city (Portland, to be exact. Anyone know of any other good places along the west coast?). From there I will definitely be working to come up with matched pairs, and I really appreciate the heads-up there!

I did have a quick question-  whats the reasoning behind the need for RN60D packaged stuff? I ask only because I've been mulling over having all the resistors actually being SMDs, in 0603 package, to save on space and assembly time. Would that be an unwise choice? What if I were to go with RN60D only for the stuff that's particularly sensitive to matching?

 

[thomasdf]

Why not stard with something similar to this, and maybe tweak it a bit to match your needs.
The plug and play card is pretty cool I think but you can get rid of that part of the design pretty easily

And BTW I am flagging this because no matter what way you choose to do this I am interested!

 

[mutterd]

Why not stard with something similar to this, and maybe tweak it a bit to match your needs.
The plug and play card is pretty cool I think but you can get rid of that part of the design pretty easily

And BTW I am flagging this because no matter what way you choose to do this I am interested!

I actually kind of agree with Thomas…

and the card edge connector is also pretty handy.

you could just scan it - make a copy and then you could burn the pcb right from there… i think it would be the easiest way.

as for the resistors - all the biasing and signal path stuff should be metal film - the RN60D's are just high quality, flame resistant, precision resistors and are what they were using back then…

i can't really speak to anything surface mount - but one thing to keep in mind, these things can get pretty hot - the white copper clad they used is flame resistant, the resistors were too - if you get a bunch of these going together you can heat the control room!

as for the transistors - i was actually serious - i think if you're gonna get a few of these to work you are going to need to either find prematched pairs or get a whole lot of them to draw from…

I dont know anyplace in portland, but there are some great supply houses on the left coast for sure, my 2 favourites are:
http://www.allelectronics.com

https://www.surplussales.com

keep us informerd!

 

[thomasdf]

I've toyed with the idea of building myselfs so Spectra Sonics a while back, and I ended up figuring out it was easier to stick close to the original design... Let's us know how are thing going, I'd be interested in PCBs if you etch some...!