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Old 2nd June 2010, 01:55 AM   #1
jdubs is offline jdubs  United States
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Default 45-based SET -> Pass Labs F4

Guys, what is the recommended resistor value for wiring across the output terminals of an SET amp based on the 45 tube for an SET->F4 setup?

I've seen references to 20r and 22r.

Thanks,
Jim
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Old 2nd June 2010, 01:59 AM   #2
ZUM911 is offline ZUM911  Australia
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I thought Nelson recommended 8 ohm or so. that's what I used on the output of my Yamamoto 45 to the F4. Sounded fine
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Old 2nd June 2010, 04:18 PM   #3
jdubs is offline jdubs  United States
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Thanks ZUM911. Do you know what power handling is appropriate for the resistor assuming my 45 amp kicks out about 2 watts / channel? Does it matter?
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Old 2nd June 2010, 05:13 PM   #4
DougL is offline DougL  United States
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For a 2 watt, 8 ohm load I would want an 8 watt resistor to limit power compression.

Also, think about trying higher than 8 ohms for the load.
You will probably get less distortion with a 32 ohm or higher load.
This would also allow a smaller resistor, say 2 watts, to be sufficient.
I think you should experiment a bit.

HTH

Doug
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Old 3rd June 2010, 10:38 AM   #5
ZUM911 is offline ZUM911  Australia
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I have 12 watt mills across the terminals. mostly because that's what i had on hand. also the output trannies of the Yamamoto are set to the 8 ohm tap, so that made sense to me
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Old 6th June 2010, 06:10 PM   #6
jdubs is offline jdubs  United States
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Thanks once again, guys. How important is resistor quality, here? I assume that tight tolerance levels between the resistors is important. Not that many "audiophile" 5w and above resistors out there. I think the Mills MRA-5 and MRA-12 series look pretty good.

-Jim
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