Arion SAD-1

[ExpAnonColin]

(this was also posted on the HC forums for those of you who go there)

It uses 1 MN3205.  There are 2 trimpots, one for clock bleedthrough and one for the bias.  I suppose you could make your delay sound distorted and lo fi if you messed around with the bias, but it sounds fine how it is.  The MN3205 is being driven by a 3102.  Not a huge surprise... the echo time is basically 33k + delay time pot value + 33k time 68pf.  Yeah, it's using a 68pf in there.  I'm going to be replacing SOME of those components, just trying to figure out which, because I know this thing is set up to take at least a little bit more delay time.  It's using a NEC compandor labled "µPCI571".  Funny, DG Boggs seemed to love this thing but everyone says the 570 is better .  Other than that it's pretty basic.  The feedback, buffers, boosters, etc, are all transistor based, most of them are NPN C1815 (apparently not that common of a transistor, wonder why they didn't use 3906 or something).  It also has a 4027 (CMOS) in there, so methinks that the whole thing isn't analog.  There's also a 7555 which must be used for the 4027.

That's pretty much it-I've got the circuit under my thumb now, it better be prepared for some LFO-controlled delay times and feedback amounts...

-Colin

[Paul Marossy]

All I know is that I like mine.  

I am interested to hear how your explorations go.

[Paul Marossy]

I've been considering doing a DIY version of this circuit and have been doing a little bit of research on these chips and what they do. Are the MN3205 chips still easily obtainable?

Also, I was thinking that the TA4027 chip (CMOS flip-flop, right?) and the TA7555 CMOS timer might have been used to try to reduce current consumption. That SAD-1 eats batteries like a ravenous wolf already...

[ExpAnonColin]

MN3205 are still available for $16 at smallbear.  You could also probably score one for sorta cheap off some forumite if youa sked.

-Colin

[Paul Marossy]

16$ ?!  :shock:
Wow, they are kinda pricey... that must mean that they are not very easy to find. Money is not an issue with me, though. Thanks for the info.

[Fret Wire]

[Fret Wire]

[Dan N]

The 4027 is pure switching. The TA7555 is (are) 2 TA75558 dual op amps. One a DIP and the other a SIP.

I did send you a trace a while back. I believe it to be accurate.

Dan

edit- I posted before Fret Wire's images loaded. Anyway, I hope you post your experiments here. Good luck!

[puretube]

...methinks that the whole thing isn't analog...

:?:

[Paul Marossy]

Cool Fret Wire, I didn't know that there was a schematic up on it!

I put together a tech report page on the SAD-1 on my site last night. Most of what I assumed about what was happening in the circuit turned out to be right, as far the functions of all the chips goes.

One question: Has anyone measured the voltage at points X,Y & Z? According to the MN3205 data sheet, power supply is 5V. I am assuming that is why my SAD-1 will not work on a common power supply, because "ground" in the SAD-1 is not the same as ground in my other pedals...

[Fret Wire]

Paul, interesting write up. I have more pics of the board on my hardrive.
http://diystompboxes.com/sboxforum/viewtopic.php?t=23339&highlight=sad1

The photo's were of my grey cased SAD-1. I also have a black cased one. I'll have to check the board numbers and specs against my grey one.

Quick mods that come to mind are cap upgrades, and replacing the TA5558's with NE5532's. Wet/Dry mix could be adjusted also.

I'm not sure who (originally posted) to thank for the schematic and layout. I reduced them down so the thread would post a little faster.

[Dan N]

Here's the full size schematic:

http://users.rio.com/senorris/junk/arionsad-1.gif

My trace. No rules about anyone hosting it, changing it, of even taking credit for it. I don't care. Hotlinking might not be a good idea as I clean house every once in a while and delete files from my server.

I think pcb SAD-1A was a gray case, and the pcb SAD-2C2 was black.

Sorry about not taking voltages or having component numbers.

Scott Swartz's AD-3208 is a very similar analog delay. As I recall, he took his favorite bits from a couple classic delays and worked them into one sweet DIY project. The filter component values etc. could be changed to imitate an SAD-1.

It would be fun if there were a project designed to be crazy!

[Fret Wire]

My apologies Dan. That was obviously alot of work to trace, and I prefer to give credit where it's due. Thanks for the schematic and layout.

[Paul Marossy]

Dan N -

Well then, with your permission, I would like to post that schematic from my website. Let me know if you have any objections to that.  
(I can give you credit for it, too, if you wish)

Fret Wire -

Any other information you could dig up on it and relay to me would be good. I would like to make that SAD-1 page as comprehensive as possible.
BTW, in the late 80's I remember that the SAD-1 that I owned back then had a grey case. But the one I bought via ebay earlier this year had a black one... I thought my memory was failing me.  :shock:  

[puretube]

...in the schem, the dimension (100k???) of the resistor going from wiper of the bias-trimpot to input-pin (7) of the MN3205, is missing...

[Dan N]

Paul, please do use it.

puretube, yes, it was 100K. I added it to the schem as well as the value of the first filter cap (220uf).

Dan

[Paul Marossy]

Thanks Dan.  

[jimbob]

So- if i understand this right..the 3205 cost about as much as the effect itself? If so- does anyone know how to take ic's off boards without damaging the chips? I cant seem to do that..i know theres gotta be a way...

[Paul Marossy]

So- if i understand this right..the 3205 costs about as much as the effect itself? If so- does anyone know how to take ic's off boards without damaging the chips? I cant seem to do that..i know theres gotta be a way...

Yep, but the SAD-3 does not sound the same as the SAD-1 from what I hear. I haven't heard the SAD-3, so I can't say one way or the other.

As far as removing IC chips from PCBs, if it's single-sided, careful use of desoldering braid works well. Double sided PCBs are very tough, though.   :evil: