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In Reply to: RE: Quicksilver tubes on the midrange panels/ribbons - MGIIIa's posted by Davey on April 27, 2015 at 09:12:40
Thanks for your thoughts. Are you talking input voltage? I can increase the db gain from my crossover, but have no idea how much. is there a formula for impeadance difference? The input impedances are different - 100k for the Quicksilvers, and 20K for the Acurus. The QuickSilver's seem fine on the Midrange panels, but seem very week on the Ribbons. Is it safe to run a 2 ohm load into a 8 ohm output on a tube amp? I always thought this was a huge no-no.
Regards,
Jim
Follow Ups:
Computing the voltage gain gets a little tricky sometimes because of confused manufacturers specifications, but in this case 1.1VRMS yielding 200wpc/8ohm (Acurus) results in voltage gain of 31db, and 1.0VRMS yielding 25wpc/8ohm (Quicksilver) results in a voltage gain of 23db. So, theoretically, you'd need to up your voltage drive to the Quicksilver amplifier by 8db to provide the same ribbon output level as when using the Acurus. Make sense?
The difference in input resistance of these amplifiers is irrelevant in this case since you're driving with an active crossover.
Attaching to the 8 ohm tap simply couples across more of the output transformer secondary and provides an effective increase in voltage gain. You don't have a preferable impedance match, but this is just a test and you're not going to damage anything.
Cheers,
Dave.
It is the mini mono with 2 ohm taps. The output impedance of the Behringer analog outputs are 160 Ohms.
Thanks,
Jim
The output impedance of the Behringer and the input impedance of the amps are irrelevant.
These kind of relative voltage gain differences are one of the many issues active crossovers have the ability to solve. If using the Quicksilver amp, simply raise the output level on the tweeter outputs of your Behringer to compensate. If you can't get it high enough, lower the level of the other outputs.
Dave.
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