Help/advice/guidance translating schematics onto a pcb

[ruffrecords]

if you take a look at the schematic I have a 10k resistor before the LED. Does that not solve the problem of 48V being too much for an LED?

However, looking at a Neve 1073 schematic from AML, theyve done what you suggested for the LED. Double pole switch, sending the main +16V power to the LED (with the same 10k resistor before hand. Gonna do some investigating and see what works best. If I can make it work with the 48V that'd be ideal so I dont have to route another big power track across the whole board

Just for completeness, the original 1073 did not have a phantom supply switch.Phantom power was switched globally across an entire mixer.

Cheers

Ian

 

[djmiggymigz]

Interesting thread and a good steer for me about KiCad. I'd always done PCB layouts on grid paper in the past or perhaps tracing paper over a 0.1" grid with red pencil on one layer for east-west, and blue pencil on a second layer for north-south ...

With "more time on my hands these days", I was looking for something to bring my PCB layouts into at least the 20th Century, if not right into the 21st ... anyway, the upshot was I downloaded CircuitMaker but I can't say I love it, so I'll be happy to look at an alternative!

Learning a lot here. Thanks gents!

Super happy to hear others are learning here too! I sometimes feel bad for my almost infinite questions but there is so much that goes into this that at the very least a little guidance in the right direction feels needed and is immensely appreciated. Thanks to all who've lent a hand already!!

I couldn't recommend KiCad enough. I only downloaded it a week ago and it makes a whole lot of sense to me already. The biggest challenge is learning the ins and outs of the actual electrical engineering side of things. Learning how to use the software itself is cake in comparison. PLUS, you can export you .gbr and drill files, drop them right into JLC and have your custom pcb's in hand within 2 weeks. So very cool to me

 

[djmiggymigz]

Just for completeness, the original 1073 did not have a phantom supply switch.Phantom power was switched globally across an entire mixer.

Cheers

Ian

Whoa meaning if phantom was on one channel it was on all the channels??

I've also noticed that the original 312 design doesnt seem to have phantom power either! I suppose maybe that's because dynamic/ribbon mics were still the majority of mic lockers? Thus 48V wasnt standard or needed until later on?

 

[zamproject]

if you take a look at the schematic I have a 10k resistor before the LED. Does that not solve the problem of 48V being too much for an LED?

No, 10k under 48v is 5mA, on the low edge for a LED (depending how bright you want it) 5k may be better

What I mean is that phantom power for one mic is specified around 10mA, let say you have a console with 16 mic input, 48V rail may be scaled to offer around 160+ mA (in fact it is often less as manufacturer cut corners and suppose you won't plug 16 phantom powered mic at once...).
If you add a LED signalling status on each input on the same rail you will overload it as you need 160mA too (@10mA each) to light the LEDs.

Also you better isolate/separate audio supply from signalling supply, usually a 5V rail (modern LED) or 12 to 24V (bulb) is used for all light visual feedback and relay.

I've also noticed that the original 312 design doesnt seem to have phantom power either!

API 312 is a part (preamp) of modular console, I never look at API console block diagram, but the P48 is probably handled outside the input module with dedicated supply bus/rail directly wired to previous routing module or mic input connectors.

meaning if phantom was on one channel it was on all the channels

yes, usual practice back then...