BeePree Hum

[vpeele]

Hello All,
 My BeePree 300b was player GREAT for years. The other day I noticed a hum, at startup, coming out of the speakers. At first it would quiet down. Now the hum keeps going. When I gently tap on the preamp an echo also comes out of the speakers. I switched to an old Bottlehead preamp, I think a Foreplay, the hum disappeared. That Foreplay sounds Good! Yesterday I put the Beepre back in the system and it played great. Today the hum is back. I replaced both 300b tubes and the EL-84 tubes and the hum is still there. I don't see anything wrong with the wiring but I don't really know what to look for.
I can send it to the wizards at Bottlehead to have a look but I'm afraid it will work just fine when they plug it in.
  Thank You All for all the help passed and present.
    Have a Great Weekend,
                            van

[Paul Birkeland]

Hello Van,

What is your incoming AC line voltage?  (This is the BeePre 1.0 correct?)

When it gets warm and air conditioners start running, AC line voltages drop and sometimes regulator dropout can be a problem.  This was an issue we addressed in BeePre 2.0, but there are some tweaks we can apply to the first version that help a lot. 

-PB

[vpeele]

Hi Mr. PB!,
  This is the BeePree1. I'm in Nutty New York City so the ac is 110, I think that's what you're asking, 'what is the incoming line voltage'. I'm in a new area of Queens now. Next door there is a factory with equipment, (I don't know what), maybe they have electrical equipment that's causing problems??? We are not running our air conditioner today.
   Thanks for all your help,
 van

[Paul Birkeland]

Yeah, 110V mains will make a BeePre 1 hum.  For something like that, I would recommend making a boost box (how to do this can be found pretty easily online), and I would use a 120:10V-CT transformer and a switch so you can go from 110 to 115 and 120.  I have done this once or twice also for BeePre owners who are subjected to wild line voltage variations with a good amount of success.  The only issue is that you really don't want to use a boost box unless you need it, so if you have 120V coming out of the wall and you boost it to 130V, the BeePre is going to get hot in a hurry!

(You could also build a BeePre 2, who doesn't appreciate a shameless pitch right?)

[vpeele]

Hello Paul,
 DO you think an a.c. line conditioner will eliminate the hum?? I was looking at cheep furman line protector-line conditioner. They cost about $100.00. Or a used one.
  Thanks,
     Van

[Paul Joppa]

A line conditioner won't address this problem. The cause of the hum is that the filament power regulator starts to drop out of regulation when the voltage drops below around 110 volts. The easy answer is to step up the voltage a bit with a small booster transformer, as PB has suggested.

[Paul Birkeland]

A regenerator would also solve this problem, but the boost box is significantly less expensive.

[johnsonad]

A variac is an easy fix for this.  My mains voltage gets as low as 110v and varies throughout the day.  I picked up a cheap plug in MM and for listening sessions, I use it at the start, adjust the variac to 120v output and enjoy the music.

The Amazon number for the product I'm using is: B07JN1JDC1.  There are now many versions like it but you get the idea.