Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Mars-Hall on March 29, 2013, 06:20:58 am

Title: 72 Quad Reverb heater wires crossed?
Post by: Mars-Hall on March 29, 2013, 06:20:58 am

This week I came upon a great deal for a Quad Reverb.  The newest part in it are the Oxford speakers made the 37th week of 72.  I'm calling it a late 72 model.  Going through my normal routine, opening it up everything is original, minus one speaker. 

Getting to the point, I noticed the heater wires are crossed at every tube down the line.  I've read, in the library here, the importance of having the heaters wired to the same pins of each power tube.  Is it equally important for the preamp tubes to be wired in the same manner?  When I played the amp there were no hum issues, using my Les Paul.

Title: Re: 72 Quad Reverb heater wires crossed?
Post by: sluckey on March 29, 2013, 07:14:12 am

Quote

Getting to the point, I noticed the heater wires are crossed at every tube down the line.  I've read, in the library here, the importance of having the heaters wired to the same pins of each power tube.  Is it equally important for the preamp tubes to be wired in the same manner?  When I played the amp there were no hum issues, using my Les Paul.

Sounds like a strong argument against the myth of "proper heater phasing".   :grin:

Title: Re: 72 Quad Reverb heater wires crossed?
Post by: Willabe on March 29, 2013, 08:15:34 am

Freddy King at 1 point in his career was playing through 2 of those on stage.


              Brad     :w2:

Title: Re: 72 Quad Reverb heater wires crossed?
Post by: Mars-Hall on March 29, 2013, 09:17:03 am

Yes, Albert Collins used them as well. This thing sounds real good.  Gonna change the caps, thinking I might leave the tubes alone for now.  For the heaters, I'm getting a "leave well enough alone" vibe here.

Title: Re: 72 Quad Reverb heater wires crossed?
Post by: stratele52 on March 29, 2013, 10:13:58 am

I reed myself it is very important to be in phase ( weber Books ? ), but my experience in many amps with heater out of phase did not see anything work wrong .

Title: Re: 72 Quad Reverb heater wires crossed?
Post by: floyd on March 29, 2013, 06:48:24 pm

Freddie King in the October '70 issue of " Collectable Guitars" states, " I used to think heater phasing didn't matter, 'till I learned better  from none other than Duane Allman.. that cat knows guitars AND amps."

Title: Re: 72 Quad Reverb heater wires crossed?
Post by: jeff on March 29, 2013, 08:02:54 pm

I think the thing with heaters is this:

-If they're wired the same then both the push and the pull tubes will pick up hum in phase. And since the power tubes are connected by the OT out of phase, that hum will be combined out of phase and cancel.
-If they are wired opposite then the hum will be out of phase on each tube and that hum will be combined in phase and will not cancel.
(That is, of course, assuming that each power tube is picking up hum, and that all tubes are picking up the same amount of hum)
   
If you're not getting hum then: it ain't broke, don't fix it.