New guy, first question

[thundernotes]

Hi there;

Looks like a fun forum here!  I'm new to modifying and building pedals, but have worked in electronics (in some capacity) for about 24 years.  I'm initially interested in modifying my pedals for lower noise, etc. and may then take on building from scratch.  I built a few of the PaiA kits way back when, so I'm not completely lost.

With regard to modifications, I'd like to try replacing some 8-pin SIP op amps in my pedals.  The problem is, most of the IC's I'd like to try are only available as 8-pin DIP's (as far as I know)  Does anybody have a reliable method for making the conversion?

Thanks!

[petemoore]

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[Mark Hammer]

Replacing as in upgrading to higher quality or as in "I fried the existing one and don't know where to get a replacement"?

If the latter, then Small Bear Electronics has a number of them as do a number of other larger mail-order houses.

If it's the former, you pose an interesting challenge.  To the best of my knowledge, no one here has, as yet, whipped up an adapter board for public consumption.  There are several ways to accomplish this task, both of which pose spatial challenges.

The adapter would use something like a row of pins from one of those make-your-own-header strips.  The adapter board has a socket (or at least pads that could accommodate an 8-pin dip socket), and the header pins connect to pads on the daughter board that then simply go left or right to the associated DIP pin.  You could do this in a "T" fashion (i.e., parallel to the main board) or create something like a "surfboard" adaptor, with a daughterboard perpendicular to the main one.

Either way, the challenge would seem to be that it would need to be tailored to the individual mainboard.  Keep in mind that SIPs provide the convenience of fitting tight spaces as well as lining either side of the chip with passive components.  The question that arises is whether any T-style  or perpendicular board would fit the allotted space.  The T board would need to rise above the level of the adjacent components, and I'm not sure a simple header strip would provide the necessary elevation.  A perpendicular board might be able to fit the space better since the board wouldn't have to be longer than the SIP (an 8-pin dip is only 4 pins long, right?), but then you have to anticipate whether the side-mounted DIP would bump into anything.  My guess is that if the board was tall enough you avoid that, but then you run into the same issue you have with a T-style: is there sufficient clearance above the "forest" and below the chassis for the daughter board?

In any event, you came to the right place.  We'll figure this out.

[thundernotes]

Nothing's smoked - I just want to upgrade component quality.  I had the same idea of the perpendicular board with pins coming off the bottom to insert in the SIP holes on the mother board.  If it was done with a small PCB, a surface mount IC could be used to save some room.  These guys are local for me and may be able to do something, but I'd probably need to have 1000 pieces made.

http://www.accutekmicro.com/product_detail.cfm?Product=Custom%20%26%20Specialty%20Modules

Who knows, maybe I'll get rich off this whole idea! 

[Mark Hammer]

Yeah, an SMD op-amp would certainly make it do-able.  Heck, that might even be thinner than the SIP it's replacing, even with the added thickness of the board!

We have been slow to adopt SIPs here, partly because of the focus on restoration and cloning of older pedals, and partly because the sorts of pedals often attempted, and the sorts of chassis used to house them.  That, and the relative ease of buying/sourcing DIPs compared to SIPs, create a certain laxness about space and reluctance to migrate towards SIPs.  The attitude is further entrenched by the plentifulness of PCB layouts that people have kindly contributed, based on DIPs.

I don't think any of that is "wrong", but when you see how much flexibility and economy a SIP provides with respect to layout, it seems a shame to ignore the possibilities.

[thundernotes]

My interest in the SIP's is strictly for upgrading mass-produced commercial pedals.  When I get around to building my own pedals, I see no reason to use them unless it's absolutely necessary.

[Mark Hammer]

Of course they aren't absolutely necessary, but once you sit down and attempt to lay out a board with a SIP instead of a DIP, you realize "Holy crap! These things are a breeze to lay out with!".  The increment in convenience (assuming you can source them) starts to make them "absolutely necessary".

When using, say, a dual op-amp in DIP form, one is constrained in terms of where the passive components can be located without necessitating complex traces.  With a SIP, you could huddle the feedback cap and resistor snug against one side and the output cap snug against the other side, or if you wanted/needed to, stick the feedback cap or resistor on the other side of the same two pins.  Makes no difference.  Now THAT's convenience.

The inconvenient part is that you can't get as many devices in SIP form as in DIP form.

[spud]

I recently "mistakenly" ordered some SIP NJM386 from Mouser.  I redid my layout for the Ruby based on them and you are right about easier.  One thing is that it doesn't really take up "less" space just different (long vs square).  I did my layout on a Radio Shack IC type perf using DIYLAYOUT.   If I had used a regular perf it would be even less space.  I just hate the close tolerances when everything is jammed together on regular perf so I started using the RS IC perfs.  I'll try to up load the layout when I can get a site to host it (and I get home). 

[Mark Hammer]

I suspect you are right about the chip itself not taking up less space.  That being said, the layout can be made more compact with a SIP by having the latitude to stick things on whichever die of the chip you want, saving space in the grand scheme of things.  Of course, if one had the skill and wherewithall to produce double-sided boards then DIPS might not be less convenient or space-efficient, but in the world of single-sided homebrew boards, SIPs rock, big time.