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VR Tubes in Commercial Amps

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Posted on October 21, 2016 at 09:22:11
Triode_Kingdom
Audiophile

Posts: 10042
Location: Central Texas
Joined: September 24, 2006
 I came across these Conn organ amps on eBay recently and was surprised to see VR tubes on the chassis. Does anyone know of other examples of manufacturers using VR tubes in audio equipment?








 

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RE: VR Tubes in Commercial Amps, posted on October 21, 2016 at 10:00:08
Steve O
Audiophile

Posts: 12359
Location: SE MI
Joined: September 6, 2001
 The Allen 90W 6550 amp used them as did the RCA MI 12182 6146 amp (and others) and some Altec non-UL theatre and domestic amps.

 

Altec 350A, posted on October 21, 2016 at 11:10:26
Tre'
Industry Professional

Posts: 17293
Location: So. Cal.
Joined: February 9, 2002


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Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: VR Tubes in Commercial Amps, posted on October 21, 2016 at 14:19:48
Alpha Al
Industry Professional

Posts: 2958
Location: N. Carolina
Joined: February 16, 2004
Contributor
  Since: December 3, 2015
 Almost all tube type Leslie amps (for organ) use them for screen reg.

 

Leslie Amps - Unusual Configuration, posted on October 22, 2016 at 07:24:33
Triode_Kingdom
Audiophile

Posts: 10042
Location: Central Texas
Joined: September 24, 2006
 Leslie amps use the VR tubes as a fixed voltage drop from the B+ to the screens. The screens are only regulated relative to B+, not to ground or to the cathodes. I'm not sure how this affects the sound, or if it even qualifies as screen regulation. Pretty odd arrangement. Any thoughts on this?



 

RE: VR Tubes in Commercial Amps, posted on October 23, 2016 at 09:09:46
Blackdog
Manufacturer

Posts: 1505
Location: Ontario
Joined: March 20, 2006
 I don't think there are any current production amps except maybe a few boutique manufactures.
One that did is MFA in their power amps. They were used to drop the B+ down to 300V for the front end tubes.



Dan Santoni

 

RE: Leslie Amps - Unusual Configuration, posted on October 23, 2016 at 10:05:32
Alpha Al
Industry Professional

Posts: 2958
Location: N. Carolina
Joined: February 16, 2004
Contributor
  Since: December 3, 2015
 I've services hundreds of those, but never noticed the VR tube is in series with the screen supply.

There used to be a mod some people did on Dyna ST70's and HH Scott integrated amps where a diode was placed in series between the plate supply and the screen supply. The idea was to prevent the front-end supply from collapsing when the plate supply sagged under load.

I wonder if that was their intention?

Can a VR tube act as a diode?

 

RE: VR Tubes in Commercial Amps, posted on October 23, 2016 at 10:49:49
hennfarm
Audiophile

Posts: 535
Location: Oregon
Joined: October 8, 2008
 I think Conn liked using VRTubes. I have a little e push pull 12ab5 that uses a OD3 for the screens of 12ab5. JH

 

RE: Leslie Amps - Unusual Configuration, posted on October 23, 2016 at 15:56:02
Triode_Kingdom
Audiophile

Posts: 10042
Location: Central Texas
Joined: September 24, 2006
 I didn't realize the Leslie amps were like that either, but then I looked up the schematics as a result of this thread. Sadly, both of mine are solid state. Anyway, the series VR is acting like a Zener, not as a forward biased diode. The B+ would have to sag a lot to create the effect you're describing, enough to extinguish the tube.


 

OC3 in Leslie 122 and 147 amps, posted on October 24, 2016 at 18:05:33
FenderLover
 AFAIK, these are important for non-distorted bass. They are hardy souls. Never had to replace one. Of course, only worked on two Leslies, in my life.

Need to restore one of these, someday.

 

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