To socket or not to socket?

[Magnus Danielson]

From: Michael Moncur <mgm at starlingtech.com>
Subject: To socket or not to socket?
Date: Fri, 04 Feb 2000 16:21:49 -0700

Hi!

> Hello, I've been lurking on this list for a couple of weeks and am just 
> getting into DIY synths. My main experience is at the complete opposite end 
> of the spectrum (digital synths and software synthesis) so I'm interested 
> in going back to my roots, as it were.

OK, wellcome Michael!

> I do have experience designing, soldering and assembling circuits, but not 
> with synths specifically, so I'll undoubtedly have lots of newbie 
> questions. Here's one now.

There's a good start, acknowledging the lack of own knowledge.

> I just received the PAiA FatMan kit, which should be a good starting point, 
> and am starting on it now. One thing that caught me off guard was this 
> statement in the instructions:
> 
>     "Sockets are notorious for being the weak links in the chain of 
> connections between electronic components. We use them only in places where 
> their advantages outweigh their lack of reliability."

I think I would second that statement. It is for much of my experience true
with audio and synth curcuits. For us sockets are notorious sources of evil,
especially if you have bad sockets. There are things that should sit around
in sockets, but for most things it is just a waste of money and time.

>From a reliability perspective will sockets easilly start to add up to provide
great part of the error you can experience.

> This has generally been the opposite of my philosophy, but perhaps things 
> are different with synths. I'm tempted to add sockets for those ICs that 
> don't come with them. Would this adversely affect the circuit much? Has 
> anyone done this?

Well, there is a huge diffrence between relative slow digital curcuits
(say < 10 MHz) and analog curcuits in general. In digital designs you tend to
work with pretty high tolerance for noise and you have a rather strict range
of impedances as well. For most part you can talk about a TTL or CMOS output
and about a TTL and CMOS input and within each category the diffrence isn't
that large really. For analog curcuitry you have a much wider range of source
and input impedances and at the same time you have a higher demand for the
dynamic range of your curcuit, which can peak in about 130 dB when you do
things right.

Now, for some curcuits will you be very sensitive to small currents, and the
socket will add another possible kreeping path for currents. But that is really
nothing for the notorious problem of oxide and the eventual loss of connection.
I have many experience when I have had to "wiggle" the IC a few times before I
got the contact back. I have even seen cases where the contact force has been
so weak that virtually no power was needed to pull the chip out, it makes you
think what could happend if it got a longer sequence of vibration beeing held
in the wrong orientation - the chip would vibrate out of the socket. This could
happend during transport.

> I'm also planning a few homebrew synths, mostly based on Tom G's excellent 
> plans. Should I plan on avoiding sockets for the ICs in these too?

Yeap. Please adopt the Paia rule, it actually makes sence!

> Thanks for the info and for the making this one of the most useful lists 
> I've ever subscribed to.

Please stay tuned, and do ask questions since this will also make the list
usefull for others aswell. I have many times found that I have learned stuff
just because someone asked the right question on the list. Synth-DIY still
remains one of the absolutely most usefull lists I have been on.

Cheers,
Magnus