[sdiy] SOB

[Roy J. Tellason]

On Wednesday 10 November 2004 10:35 am, john mahoney wrote:
> Speakers On Board, that is! ;-)
>
> Somebody in the dotcom group (might've been Morbius) commented that
> the ARP 2600 speakers were an advantage over, say, a new dotcom synth.
> Now I'm curious about those speakers and the amps that powered them.
> Having never heard them, I had always assumed they were more gimmicky
> than useful.
>
> Does anybody know much about them? I haven't got the 2600 schemos. How
> much power did the amp produce? Was there much distortion? Where were
> the heatsinks? Separate power supply? Blah blah blah...
>
> Let's say that we wanted some SOBs. We have fairly high voltage
> levels, so is it possible to use a simple amplifier circuit, like just
> a transistor to increase the output current? Or is a complete power
> amp still needed?
>
> Adding speakers to a modular cabinet isn't a huge deal. The harder
> part is dealing with the amplifier, its hefty power supply, and all
> that heat! Unless the output wattage is pretty low.

It's been quite some time (over 25 years!) since I worked on a lot of that 
stuff,  but I did work on a whole mess of 2600s and never had the need to 
connect an amplifier to them to find out what was going on.  Not that you 
could get much of what you'd call any sort of real "power" out of these or 
anything.  I don't remember what they used in there,  but it had no separate 
power supply,  no significant heat being generated,  and worked well for what 
it was designed for.

I don't think the 2600 had anything other than a +/- 15 volt supply,  unless 
it also had +5,  which a bunch of ARP stuff did.

For my own uses,  I've done okay with surprisingly little power.  It really 
depends on the efficiency of your speakers.  I have one test speaker which 
has about an 8" cone,  and the magnet on it is *HUGE*,  probably approaching 
6" in diameter and at least 4" thick.  With as small and simple as an LM386 
chip running off 10-12 volts,  that thing kicks out pretty good...