Fisher 400 sounds better at 110?

dualhead

AK Subscriber
Subscriber
Hey gang, I got my 400 back from Terry Dewick and decided it was getting a little hot so I am running it on a variac set at 110. The weird thing is the sound is much better than it was on just the power conditioner/surge protector. What gives? No harm in what I am doing correct?
 
Whats the original voltage spec, and what are you getting out of the wall? Running it a little bit lower on voltage won't hurt anything, and in fact will extend the life of the tubes a bit. It may be worth building yourself a bucking transformer to drop the voltage permanantly.

Have you ever measured the heater voltage at lower line voltage? As long as they're not under about 6.0v, you're fine.
 
Yeah, my Pilot 602 runs much cooler at 110 volts but
I can't really say it sounds any different.

When I first got it I just plugged it into the wall outlet
and after using it a few times noticed the EL84 output
tubes and the output xfmrs were running really hot.
So now I always run it off my Variac and it stays much
cooler.
 
I run my 400 at 110 volts through a variac as well.

The reason is that the tubes run cooler and will, theoretically, last longer.

The 400 is designed to run from 105 to 120 volts, just look at the back of the unit.

I will never stop using my vintage Fisher pieces.

Cheers
 
I'm wondering if in fct my wall voltage is high to begin with and the variac just remedied this? I live in a basement apartment of an old house, so there is a chance that this could be an issue.
 
Most Residential line voltage runs now between 122-125, depending on time of day, how loaded down the system is, time of year, etc.

I have a meter on the circuit I run my gear off of. Consistantly 121-122. Except in the middle of the night when most people are asleep then it creeps up to 124.

guess a bucking transformer will be in the works.

Larry
 
I run my 400 as my office rig straight from the wall at 120. It doesn't seem unreasonably warm. Sounds great too!
 
I built a bucking transformer with a Radio Shack 12.6V center tapped transformer. It gave me 2 dropped voltages to play with. -12.6 and -6.3v from line voltage. I put the 400 on the -12.6 tap and ran it all y'day and this morning. It sounds a lot better, not as strained, soundsstage has opened up (like the speakers melted into the wall), and it's cooler temp wise. With my line voltage, I get 107.8VAC from the -12.6 tap. and 114.1 on the -6.3v tap.

Larry
 
Most Residential line voltage runs now between 122-125, depending on time of day, how loaded down the system is, time of year, etc.

I have a meter on the circuit I run my gear off of. Consistantly 121-122. Except in the middle of the night when most people are asleep then it creeps up to 124.

guess a bucking transformer will be in the works.

Larry

Those voltages are exactly why I decided to run a continually regulated supply (with battery backup) to my systems. Vintage, Home Theater, Plasma TV all get the benefits of a true double conversion sinewave output that also filters noise. I have an application on my PC that shows me the voltage/wattage levels, input/ouput voltages, remaining battery time, and records all spikes, surges, and drops 24 hours a day.

The best part is when the utility company decides to F with my supply (has been known to cycle on-off-on-off-on-off-on in the course of a couple of seconds), I no longer worry that my vintage Mullard GZ34's are going to die a horrible death from arcing.

Plus, I used the regulated power supply to 'tune' the new parts I used in the final touches of my vintage Scott LK-72A amp restoration project. This allows the feed voltages to be in an optimum range in order to keep the amp running in a narrow range of 'best case' tolerances.

. . Falcon
 
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