Warwick Hellborg preamp transformer question

[LukeFRC]

Sorry that post above was me musing …

 

[LukeFRC]

So this is the input board
XLR to transformer - mono Jack to IC201 to get to mic level …
Then the relay is to switch between them - what’s the stuff on the right hand side for? Power to the relay? The +0v and -0v is something I’ve not seen before!

 

[vigilante398]

View attachment 93580
So this is the input board
XLR to transformer - mono Jack to IC201 to get to mic level …
Then the relay is to switch between them - what’s the stuff on the right hand side for? Power to the relay? The +0v and -0v is something I’ve not seen before!

Looks to me like those are the letter O and not the number 0. So possibly an abbreviation for positive and negative Output voltage?

Reasonable to assume that's the rail voltages for the NE5532

 

[LukeFRC]

makes sense - those 100R resistors are going to drop it slightly from +-15

 

[jwin615]

makes sense - those 100R resistors are going to drop it slightly from +-15

Also have a 40Hz LPF on each rail going on. 100R shouldn't alter the V but will current limit protection to some extent. Well. After 150mA or so. That's when you'll see V drop.