Regulators

[peteko]

Hello,

Has anyone tried the "Boris-mod" regulator in TUT? This is a cascaded regulator using MTP 2n45 mos transistors. In adding a mos regulator (or any solid state regulator), is there much worry about heat dissipation?

Thanks,
Pete

[Tom Phillips]

Pete,
I haven't found where "Boris-mod" is mentioned in TUT but heat dissipation is always a factor when you are designing an analog regulator. The voltage you need to drop multiplied by the current being drawn through the regulator is the power that must be dissipated in the regulator. That power gets converted to heat. You then need to attach the main regulating device to something that will pull out the heat fast enough that the device stays below it's max design operating temperature. Most of the time for guitar amps you can mechanically attach the device to a relatively cool part of the chassis while keeping it electrically isolated. This is probably covered in TUT somewhere. Otherwise a Google search for regulator design info will give you good info.
Regards,
Tom

[peteko]

Hi Tom,

Thanks for the reply. The drawing is in figure 2-14 on page 2-12. I will take a look around and search for some more theory (about regulators).

Pete

[Steve Conner]

I've never tried any of KO'C's circuits, but I did design my own regulator using 1000V MOSFETs, for a 50W amp. I used it to drop the 550V B+ to about 470V, plus a separate 360V rail to run the power tube screens and preamp tubes. I was worried about heat dissipation, so I mounted the MOSFETs to a heatsink (about 3" square with 1" tall fins) that I fitted where air from the amp's cooling fan would blow over it. I've run this amp for 6 years, played several gigs (including fairly big ones that would have made it blow up by Murphy's law if it was going to) and never had a problem with it.