15VDC heater supply in Traynor YCS100

[FrancisOnTubes]

I have a Traynor YCS100 on the bench and found a schem ( http://www.eserviceinfo.com/downloadsm/54196/Yorkville_YCS100.html ) which shows the preamp tubes (12AX7) with 15VDC heater supply.

this is a new one for me.   Anyone want to comment on why this is a good/bad thing?

[PRR]

> preamp tubes (12AX7) with 15VDC heater supply.

WITH an 18 ohm series resistor!!

Ass-uming series heater 0.150 Amps: 0.15A*18r = 2.7V drop. 15V minus 2.7V = 12.3V, which is a correct heat for a 12.6V heater.

> why this is a good/bad thing?

Because the system is riddled with +/-15V chips. (Good or bad; your choice.) Having forced themselves into a non-trivial +/-15V supply, and surely a PCB where AC heat is problematic, it is no-brainer to use the chip supply as much as possible (even though this means fatter winding and big heatsinks).