[n3rdling]

They do have a bias supply

 

[davidsh]

  They do have a bias supply

Yeah.. But where from? 

 

[kevin gilmore]

most plug into the wall. schematics are available.

the really old koss boxes build up voltage from the audio signal

 

[davidsh]

most plug into the wall. schematics are available.

the really old koss boxes build up voltage from the audio signal

Ohh from the audio signal. That cannot be too good for the sound quality, just assumed one wouldn't do that sort of stuff. I am specifically thinking about the srd-6 adapter, which only need to be connected to an amp via 4 wires.
Whatever, I do have a dedicated amp after all.. But thank you anyway, always interested in learning more.

 

[DefQon]

Bada-boom....

 

[bearFNF]

bada-big-boom...

 

[kevin gilmore]

srd6 has a wall plug. same schematic roughly as all of them. high impedance voltage multiplier.

 

[davidsh]

My srd6 has no wall plug. You might be mistaken on that one?

 

[kevin gilmore]

srd6-sb is self bias generation, no ac power cord, original version has power cord.

 

[davidsh]

Generated from the audio signal? Quite neat, yet it can't be too good for sound quality.

 

[spritzer]

It's quite simple really and with next to no degradation to the signal.  A high ratio transformer is connected to both secondaries on the audio transformers which in turn drives a 7 fold voltage multiplier limited at the input to 82V through a transient suppressor. 

 

[edstrelow]

Generated from the audio signal? Quite neat, yet it can't be too good for sound quality.

Possibly but it avoids issues with ac line  noise.

 

[Keithpgdrb]

Generated from the audio signal? Quite neat, yet it can't be too good for sound quality.

I've used the 7sb for years, and it sounds quite excellent.  It scales with whatever amp you pair it with.

 

[bearFNF]

I've used the 7sb for years, and it sounds quite excellent.  It scales with whatever amp you pair it with.

Same here. Been using it that way since it was new...198x...

 

[NoPants]

I think spritzer has boards available for a standalone bias supply, so you can always go boutique and run lumdahl step-ups