[sdiy] +7 and + 2 volt supply

Tom Wiltshire tom at electricdruid.net
Mon Jun 10 09:27:36 CEST 2019


My guess is because at some point they need to use the output from the digital chips on the analog side.

I once did something similar with a PIC. I wanted to process the PIC’s 0-5V output with an op-amp, and if you’ve got a standard op-amp on a 0-9V single supply, it clips at the lower rail. Raising the PICs voltage to 2-7V puts it in the middle of the range and avoids this problem.

Tom

==================
       Electric Druid
Synth & Stompbox DIY
==================

> On 10 Jun 2019, at 03:10, Adam Inglis <21pointy at tpg.com.au> wrote:
> 
> In another thread I mention a bunch of Roland/Boss delay boxes I’m looking at.
> Most of these take the usual Boss 9 volt supply and regulate it with a 78L05 giving a +5 to zero volt supply.
> However, in one of these machines, which uses much the same circuitry as the others (the RSD-10) and the same 9 volt DC adapter, Roland have used a 78L07 next to a 79L05 to give a +7 v to +2 v supply.
> 
> Anyone care to hazard a guess as to why?
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