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Ultra-Linear


 
9/22/1998 5:18 AM
Mook
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Ultra-Linear
What is ultra-linear?
 
9/22/1998 7:59 AM
Whit
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Mook,  
 
Very straight? ...  
 
But seriously, it refers to an additional  
tap off the primary of an output transformer,  
about %40 of the way between the centre tap  
and the end. (PP tranny assumed here, although  
SE OT's can have the UL tap too)  
 
In use, the B+ goes to the centre tap, and  
the ends of the winding feed the plates as usual. The UL taps are then used to feed the screens.  
 
A bunch of guys, far wiser than I,  
discovered back in the golden days that this  
allowed very ultra linear performance of the  
power, with the magic number around 40%  
 
Of course, you could be saying about now  
"Yeah, I know that, but what is ultra-linear?"  
 
It refers to linear equations, you know the  
old x = 2y + 5 stuff. Essentially straight  
lines. So when the change in input signal  
is plotted against the change in output signal  
, a straight line results.  
Much easier to draw, but basically it means  
that the output follows the input more precisely, without signal distortion at the  
peaks and valleys of the wave forms.  
 
Don't want to get to deep into the math here, since it really doesn't matter much in  
a practical sense; all the "figurin'" has been  
done already.  
 
Also, UL is seen more in hi-fi applications,  
since striving for minimum distortion in  
guitar amps is like dating your sister...  
 
... Whit
 
9/22/1998 8:39 AM
anonymous
Whit> in your opinion,if Mook or anyone else had a OT with the UL taps,would they have to use them or could they be not hooked up and just use screen grid resistors? To make it more like a regular ot.
 
9/22/1998 8:48 AM
Whit
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Anon,  
 
No, you don't have to use the UL tap at all. Just tape it up the UL tap lead, so it  
doesn't ground to anything, and you have a standard OT...  
 
 
 
... Whit
 
9/22/1998 7:04 PM
Reid Kneeland
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For that matter, you could tape up the *ends* and just use the screen taps - you'd have a standard OT with lower impedance and less power handling (which might actually be useful).  
 
Reid  
 
P.S. If RS tries to patent this, I'll sue him. :-)
 
9/22/1998 11:16 PM
R.G.
"Ultra Linear" is a term coined by David (?) Keroes and David Hafler (yes, THAT Hafler) for their connection of the screen grids to taps on the output transformer to make the output tubes look more linear that either triode or pentode.  
 
The local feedback into the screen grids linearizes the tubes and may increase available power - I'll have to get the article out.  
 
They published this in a '50's issue of Audio Magazine.  
 
Ultra linear has proven to be a bad idea for guitar amp operation as it makes the output stage too clean in most people's opinion. The Fender 135W Bassman is a good example of an amp that uses ultralinear, and one that profits by its removal. The sound is a bit hard or too clean. It's a good hifi tube technique, though.  
 
You can tie off the taps in an ultralinear amp and reattach the screen grids to screen supply voltages. This warms the amp up a bit and is recommended for the 135W.
 
9/22/1998 11:33 PM
Richie
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RG: Almost all sunn amps have the UL taps.[Richie]
 
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