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Rectifier differences

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Posted on April 5, 2021 at 13:11:11
marlin
Audiophile

Posts: 124
Location: Sandy, Oregon
Joined: November 20, 2012
I recently bought a re-issue pair of 5AR4 tubes to replace the NOS 5U4 tubes in my Cary SLI-80.
Comparing the quality of sound of the two, I need more time to judge, burn in of new tubes and all.

What I did notice is the volume. With the AR's I have to set the volume about six notches higher to achieve the same level.
Very familiar with my system and room so it is not my imagination.
Is there an electrical reason why this would be?
Thanks in advance.


Marlin


Without music what is there?

 

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RE: Rectifier differences, posted on April 5, 2021 at 16:16:56
Eli Duttman
Audiophile

Posts: 10431
Location: Monroe Township, NJ
Joined: March 31, 2000
Forward drop in 5AR4s is < than that in 5U4s. So, you are getting a few more B+ volts.


Eli D.

 

RE: Rectifier differences, posted on April 5, 2021 at 16:21:13
FlaCharlie
Audiophile

Posts: 889
Location: Gville, FL
Joined: June 1, 2003
The main electrical difference, once both tubes are warmed up and conducting fully, is that the 5AR4 drops less voltage (about 17v) than the 5U4GB (about 50v). The drop will vary a bit depending on the current. There are other differences in the specs too, but that's likely the biggest one.

As a result, the votages will be higher when using the 5AR4 than with the 5U4GB. This affects the operating points of the tubes.

All this assumes that both tubes meet the specs shown on the data sheets, which were developed many years back. It's entirely possible that new production versions don't adhere to the specs as closely as old production. New production 5AR4s also have a reputation for not being as stout and reliable as old production.


 

RE: Rectifier differences, posted on April 5, 2021 at 17:43:40
Tre'
Industry Professional

Posts: 15162
Location: So. Cal.
Joined: February 9, 2002
I have to ask, why would you not use the tube the circuit was designed for?

Tre'



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

 

RE: Rectifier differences, posted on April 5, 2021 at 21:24:21
Triode_Kingdom
Audiophile

Posts: 8670
Location: Texas
Joined: September 24, 2006
This would make me question whether something might be wrong with one or both of the new 5AR4s. Not familiar with the Cary schematic, but I can't think of any reason off the top of my head why a higher B+ would cause a loss of volume.













--------------------------
Buy Chinese. Bury freedom.

 

RE: Rectifier differences, posted on April 7, 2021 at 15:47:22
Tre'
Industry Professional

Posts: 15162
Location: So. Cal.
Joined: February 9, 2002
couldn't the higher B+ drive one of the stages out of an operational range?

I guess the B+ difference wouldn't be that dramatic?

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

 

RE: Rectifier differences, posted on April 20, 2021 at 07:50:20
sony6060
Audiophile

Posts: 823
Location: SE MI
Joined: August 8, 2014
5AR4s produce too high voltage. Go back to 5U4GB nd for best sound use Tung Sol 5U4GB.

 

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