The reason for "negative" supply

[zamproject]

Hi all

My console use negative supply for audio and signalling rail, I always wonder why but never search a lot

There is a equal mix of NPN and PNP so this might not be the reason, anyway, at audio side the supply is bipolar (regulation at each channels) from 0/-22 to 0/-11/-22 (with the ref at -11V)
So I was thinking the Studer engineer take care of the chemistry ? whole desk is in aluminium, and of course lot of copper at electronic. I have some quick read since and seem possible...

This is one of my summer reflection, what is your thought ?

Best
Zam

 

[JohnRoberts]

my thought is that this exact question was asked here only weeks/months ago.  :
---------
The obvious benefit of split supply is referencing AC signals to 0V while DC coupling drive electronics.

JR

 

[zamproject]

my thought is that this exact question was asked here only weeks/months ago.  :
---------
The obvious benefit of split supply is referencing AC signals to 0V while DC coupling drive electronics.

JR

I'm not talking about the fact that local electronic is bipolar ? if that's what you say ?
But why the desk is feed with only negative supply (ref to ground)

Main supply is 0/-22V
local supply is 0/-11(ref)/-22

Best
Zam

 

[JohnRoberts]

Old discrete designs routinely used only one rail...

Studer may be based on some legacy design...

or in other words, I don't know why they did that.  :-[

I will stop blathering now.

JR

 

[moamps]

But why the desk is feed with only negative supply (ref to ground)

Maybe just because the chief engineer drove Volkswagen T1 Beetle which was  6V positive ground car. 

Or because the first transistors were Ge PNP type.

 

[zamproject]

Maybe just because the chief engineer drove Volkswagen T1 Beetle which was  6V positive ground car. 

Ha ha 

Or because the first transistors were Ge PNP type.

No it's not, early MKI design (I have MKII) already use NPN+PNP Si transistor
and for what I know before that design is tube at Studer.

So still my assumption about minimizing oxidation in a large frame full of Al and Cu crazy ?

Or maybe they start the design with Ge transistor in mind and flip to Si during the development ?

Best
Zam

 

[benb]

Ha ha 

No it's not, early MKI design (I have MKII) already use NPN+PNP Si transistor
and for what I know before that design is tube at Studer.

So still my assumption about minimizing oxidation in a large frame full of Al and Cu crazy ?

Or maybe they start the design with Ge transistor in mind and flip to Si during the development ?

Best
Zam

"minimizing oxidation" - oh, so THAT's what you meant by chemistry. I didn't understand your original question/statement.

I've designed electronics, but I never would have thought of using a positive versus negative ground based on what might oxidize. I'm not familiar enough with chemistry/electrochemistry to know what would do what anyway.

 

[PRR]

The history of audio is deeply connected to the Telephone System.

Early telephone relays had less corrosion (from dampness in the silk wrapping) if the central battery was positive ground. (And before that, electric railroads.)

https://electronics.stackexchange.com/questions/10851/why-do-pbx-systems-use-48-v (much blather here)

Single 24V or 48V power, positive ground, is the common supply in telephony, and by association, much older "low" voltage radio network gear.

A side-branch is single 24V, sometimes negative ground, as seen in older Neve. I have always assumed this was to run on a truck battery when trouble came and utility power went out.

Also single-supply means less wiring across the racks (but more parts in each unit).

 

[zamproject]

Hello

Thank PRR fo the light !!

Make total sense now

Single 24V or 48V power, positive ground, is the common supply in telephony, and by association, much older "low" voltage radio network gear.

Main clients for this desk in the 60' and 70' were radio broadcast

A side-branch is single 24V, sometimes negative ground, as seen in older Neve. I have always assumed this was to run on a truck battery when trouble came and utility power went out.

Also, the small frame version were for sure used for remote broadcast/recording

My desk is a "studio" version, different (bigger) frame but it's the same console family and share the electronic design.

Best
Zam