Electronics folk: would the negative part of a 12v DC power supply barrel jack be -12v?
Trying to search engine this is not simple what with the LLM bullshit x)
@renbymon Depends. Are you using the positive side as the 0V reference point? If so, then yes. The negative terminal would be -12V.
But if you use the negative terminal as the 0V reference point then it is 0V and the positive terminal is +12V.
It's always relative to a reference voltage, and typically the "negative" terminal is the reference voltage.
@dragonarchitect @Jencen I'm trying to reverse engineer a eurorack mixer to recreate on a breadboard. It uses power to run an op amp, and it used both of its +12v and -12v rails to power it. I guess the follow up question is that does VCC- need to go to negative whatever voltage I input or can it just go to ground?
Data sheet for the op amp in question: TL072 page 5 https://www.ti.com/lit/ds/symlink/tl072.pdf
@dragonarchitect @Jencen Also here's the mixer for context https://www.n8synth.co.uk/diy-eurorack/eurorack-mixer/
@renbymon @Jencen VCC+ and VCC- are your hard-stop voltage and power rails for the op amp's output. It cannot go any more positive or negative than those values, even if the input voltage swings beyond them, or if the feedback loop forces the op amp to try.
Ideally, you'll want either a symmetric DV supply or a "split rail" single supply where internally the circuit operates at an intermediate voltage above 0V that is the circuit's internal 0V reference point.
@renbymon @Jencen After firing the @Gogledd ott-signal, I can confirm what @dragonarchitect said. The op-amp is essentially getting a 24V supply, with one rail at +12V and the other at -12V, with respect to the circuit's ground or 0V reference. It's kinda like the weird mains power in the USA/Canada. Point is that AC signals can be +ve or -ve with respect to 0V, so the op-amp gets both a +ve and -ve supply to be able to swing its output proportionally +ve and -ve based on the input.
@tryst @Jencen @Gogledd @dragonarchitect Thank you all <3
@renbymon @tryst @Jencen @dragonarchitect Hi hi! I think all the right answers have been given so far from what I can see, but I do run a Eurorack module company, feel free to DM about any specific questions etc if you like ^^
@Gogledd @tryst @Jencen @dragonarchitect Oh awesome!! I'm just getting into synths at all, so I'm not looking at doing anything eurorack yet (was looking for a simple mono mixer project and aside from that one thing re the op amp I could parse everything else), but if I do get into eurorack and have any questions I will reach out! Thank you again!
@renbymon typically if a power supply only has two rails, they are labeled as reference and positive. Most of the time you need a center tap to get a negative rail. Although it is merely a frame of reference, so if you were to treat what it caused the positive as your reference, then the other one would technically be 12 volt negative.
@renbymon no. Should be +12 and 0v
Depending on country of origin 90% are center positive.
Japanese stuff is usually center negative.
Never really clocked that saying o.o should be center 0 o.o