An unbiased topology

[sammo303]

I'm not clever enough to have come up with this myself so why isn't this used?

Charge pump to provide -9v rail, powering all gain stages with +9v and - 9v, avoiding the need for bias voltage and coupling caps.

 

[rossbalch]

It is in some pedals, but tradition (especially from the +9v battery era) still rules, and it's often less parts to do a vref than it is to add the charge pump. Charge pumps aren't free either, they have their own noise issues.

 

[drew.spriggs]

It is on multiple pedals, but it's unnecessary most of the time.

DC-DC converter is a much easier/better way to do it as you can increase the rail voltage for as much headroom as you could possibly ever bees

 

[vigilante398]

As noted it's used pretty frequently in the audio world (and frankly in other non-audio analog circuits as well), and if you read an op-amp datasheet they typically call for a bipolar supply rather than a single supply. As also noted, pedals hold largely to the tradition of 9V batteries, so we're accustomed to using a single +9V input and generating a reference voltage, usually with a simple resistor divider.

 

[Passinwind]

It is on multiple pedals, but it's unnecessary most of the time.

DC-DC converter is a much easier/better way to do it as you can increase the rail voltage for as much headroom as you could possibly ever bees

Yep, I’ll typically use +/- 15V if I’m bothering with a bipolar internal format. For me that means true line level applications such as driving pro audio amps and rack gear.