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My spitifire B+ measured about 350v from memory > I'm also using jj 5ar4 recitifier.

Told you to put it in the Bassman Frank, you won't listen
Nigel

Nige, I don't listen to my own wife! What makes you think you'll have more pull!

I'm not convinced it's the choke yet either. I'm going to pull out the other DMM and see if I get any change in things....I'll report back soon.

-F

OK,

I did some experimenting. On my previous amp, I was using a hammond 270FX, which had 2 problems. One, it was too much PT for the amp....Two, it was expecting 115v incoming ac. So in that amp, I needed a 50 ohm resistor in series with the incoming ac, to get the PT to behave as expected.

In this amp, although the heaters are within spec, they were still above normal...as was the secondaries....So I slapped a 10-ohm resistor in series on the incoming ac. It only dropped the incoming ac from 122.4 down to 120....but it was enough to drop the B+ from the 380s right down to 359.

So Now, the B+ is 359, the el84s are running in the 350s and the heaters are exactly 6.3 and 5.0.

Perfect!

So I'm a happy camper...I'm going to seal this puppy up in her stage dress...and I'll post pictures soon!

-F

Good news. You obviously live in a 'Hot' neighborhood. Close to the power generating plant are we?

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Yeah, I think I do. Granted, s2 (where's he been) says his home ac is 127, which is higher than me....Mine, when my ac is off, hovers around 123-125....Dropping it down to 120 exactly makes all the difference in the world....instead of a 389 B+ you get 360....

So having the resistor in there is a good thing...I've never come across a single place I've ever played where the incoming ac was less than 120...most places have ac's between 122 and 125....so this amp will play nicely anywhere....

Plus, I actually think the tone is a little better with the B+ at 360...but it might just be my imagination...

Have you considered using a Variac or some sort of line filter/volatage regulator?

Voltage Regulator = several hundred dollars.
10watt resistor from radio shackj = $0.50


Given the above information, and that the resistor is a perfectly viable option....no

B&V,

So the power resistor thing works quite well for you? I often wondered why people didn't use that method as oppossed to using a zener diode on the secondary CT. I never have needed to drop voltage yet but maybe with my next project. Is there any downside that you have noticed? Do you put the power resistor on the hot leg of your power cord before the fuse?

Thanks,
Denny

It works like a charm. If your heaters are also a bit hi, then it'll work for you.

In the case of my first amp, I was using a hammond PT which was rated for 115v...and putting a 50ohm between the end of the fuse and the lead that went to the power switch knocked down the incoming AC enough to have a perfect 6.3vac on the heaters and the expected secondary voltage as well.

In the case of my lightning, I didn't need much at all...just a hair drop....and it probably would have been fine if I didn't do this. the heaters were something like 6.6 or 6.5 and the B+ was about 20-30v too high. A 10-ohm resistor knocked it down to perfect levels...6.3 on the heaters, 5.1 on the recto....350v B+..etc..

-Frank

Hey Frank - I wanted to know what the wattage was on the 10 Ohm resistor you used to lower your incoming AC voltage? Was it a 10 watt 10 ohm? The voltage at my wall outlets is 122-124 volts and I have an old transformer that puts out 660 volts - 330-0-330. I want to see what it puts out if I drop the wall voltage to 115-117.
Joe