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Old 22nd June 2009, 12:52 PM   #1
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Default Amp refurbishing question.....

Are there any advantages to using 40% screen taps with push-pull 6BQ5s versus staying with an original design that didn't use them?

I'm replacing OPTs in an old amp I'm refurbishing and the Edcors I'm using have this connection. If it has audible advantages, I want to use it, of course.

If this is advantageous, are any other changes needed, such as a resistor between the screen and OPT?

Thanks, Greg
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Old 22nd June 2009, 01:24 PM   #2
tim614 is offline tim614  United States
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you mean ultralinear conection?
and yes ultra linear is better less distortion
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Old 22nd June 2009, 01:26 PM   #3
tim614 is offline tim614  United States
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where in ohio?
im in dublin ohio
what amp are you working on?
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Old 22nd June 2009, 01:41 PM   #4
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I'm in Chillicothe.

Off and on for months, I've been restoring a 1959 Silvertone Model 29 integrated.

Yes, it is the UL connection. My Edcors say screen on the tap, so I just called it that. I'm wondering if the lower distortion is actually anything audible, and since the amp is only 10-15 watts to begin with, we're looking at very little power output, which isn't always a bad thing, I know. Maybe I'll install a switch and I can go back and forth.
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Old 22nd June 2009, 03:44 PM   #5
tim614 is offline tim614  United States
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Quote:
Originally posted by 69CamaroSS396
I'm in Chillicothe.

Off and on for months, I've been restoring a 1959 Silvertone Model 29 integrated.

Yes, it is the UL connection. My Edcors say screen on the tap, so I just called it that. I'm wondering if the lower distortion is actually anything audible, and since the amp is only 10-15 watts to begin with, we're looking at very little power output, which isn't always a bad thing, I know. Maybe I'll install a switch and I can go back and forth.

switch is a good idea
15watts is plenty for efficient speaker
what speaker do you use?
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Old 22nd June 2009, 04:06 PM   #6
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Assuming that the original design has them wired as pentodes, won't changing to UL require other circuit mods as well?
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Old 22nd June 2009, 04:09 PM   #7
ChrisA is offline ChrisA  United States
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Default Re: Amp refurbishing question.....

Quote:
Originally posted by 69CamaroSS396
Are there any advantages to using 40% screen taps with push-pull 6BQ5s versus staying with an original design that didn't use them?

I'm replacing OPTs in an old amp I'm refurbishing and the Edcors I'm using have this connection. If it has audible advantages, I want to use it, of course.

If this is advantageous, are any other changes needed, such as a resistor between the screen and OPT?

Thanks, Greg
"UL" is a form of feedback. You get a more linear amp but at the cost of some output power.

If all else is equal a UL amp will fall between an triode and pentode in terms of output power and gain. Many people think it's a perfect trade off.
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Old 22nd June 2009, 08:46 PM   #8
tim614 is offline tim614  United States
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, won't changing to UL require other circuit mods as well? [/B][/QUOTE]


no
compare these schem
pentode
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Old 22nd June 2009, 08:54 PM   #9
tim614 is offline tim614  United States
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Ultralinear
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File Type: jpg mag_mods webdisp.jpg (56.2 KB, 149 views)
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Old 23rd June 2009, 01:39 AM   #10
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Quote:
Originally posted by tim614



switch is a good idea
15watts is plenty for efficient speaker
what speaker do you use?

The speakers I currently use are not particularly "tube friendly". 86dB sensitivity, but they sound fantastic. Signet bookshelf from about 1994. Bought them new at Progressive Audio on High Street in Cols. Actually got rave reviews as a budget buy. However, no low end to speak of.

I have parts and plans to build an open baffle based on suggestions I got from Martin King. Just don't have the time at the present to work on all the projects I'd like to. Unfortunately work gets in the way.
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