Tubes Asylum Questions about tubes and gear that glows. FAQ

---

[ Follow Ups ] [ Post Followup ] Thread: [ Display  All  Email ] [ Tubes Asylum ]

---

[ Alert Moderator ]

---

RE: An Isolation Transformer

Posted by JURB (A) on April 17, 2018 at 15:50:25

In Reply to: RE: An Isolation Transformer posted by Caucasian Blackplate on April 17, 2018 at 07:23:53:

"That transformer isn't likely to survive long with more than 2-3A of load current. "

I beg to differ. We are talking about an amp here that had 90 volt rails and was bridgeable. (90*0.707^2)/8=506.1 approximately. (albeit no load) In bridged mode each channel is working into 4 ohms if the load is 8. It had five pairs of output FETs per channel. The AC fuse is 15 amps which means it CAN pull that much in case of a short.

If the output of the transformer with the 12 ga. secondary is not solid enough, and the output really is only 250 WPC steady state then there would be no reason for a bridged mode. It would be a medium size room heater. Even at 250 watts into 8 ohms each channel would still need quite a bit of current.

I have a sort of dummy load that is actually a toaster oven, for high power amps. I am not measuring FTC power ratings here but it is adequate to load an amp and drive it to a very high level. When I get around to it I'll just connect it straight to the output of this thing and see how the voltage holds up. I will have to turn off the electric heat and run the test for a short time or the branch circuit breaker will trip. The load is 9.1 ohms cold and I don't want it to heat up. Then I can get an accurate picture of the output capability. If the voltage does not drop much supplying over 10 amps I will consider it good enough for most amps.

I am sure a really heavy load will drop that to 120 volts or even lower, if not the regulation of the transformer, the wiring itself. If I get into much high power equipment I will add a circuit to the box. In fact that is the plan anyway, I got the EMT, fittings and the #12 wire. I even have some heavy duty outlets and 4" X 4" boxes out the gazoob. I even have a mud plate so it is simple laziness stopping me, except I might run out of places to put another breaker. If I can't find something low draw to piggyback it that means a Square D QO series mini which can run a few bucks. If I do have to go get one it might as well be 20 amps and just make sure only new wiring is on the other side of it. All in good time.

Edits: 04/17/18 04/17/18

This post is made possible by the generous support of people like you and our sponsors:

VH Audio

---

[ Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2025, Audio Asylum, all rights reserved ]

---

[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]

---