Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: dynaman1 on May 06, 2010, 01:08:23 pm
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I'm interested in building a speaker dummy load with an adjustable lineout/headphone jack. An attenuator with adjustable headphone jack would be even cooler, but I don't mind starting simple. Anybody point me to some schems??
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Huge missing pieces of the puzzle.
What headphones will you be using? Do you know the impedance of them? Do you know the maximum power rating of the headphones? Do you know the efficiency rating of the headphones (maybe not too important)?
What amp is to be used? How much power output does it have? what OT secondary impedances are available?
If not thought out, or if you grab a random one-size-fits-all schematic, you could blow out your headphones, your ears, or both!
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The amp is running a pair of 6V6s in a PP arrangement, so I figure it can probably have peaks near 45W. 4,8, and 16 secondaries.
This project is for an acquaintance and he has multiple pairs of phones. I did some random searches of studio monitoring headphone specs and came up with some averages.
100-110 dB/1mW SPL
30-70 ohms input impedance
500-1,500 mW power handling
Would be cool if I could also use this with a 50W Marshall, but I'll start small first.
Thanks for your reply.
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Does your circuit have a feedback loop hanging off the OPT? Tap there and test with a set of expendable ear mittens (as my daughter used to call them when she was quite small). Obviously you'll want a big honking dummy load resistor in place of the speaker. Here's some sand state food for thought. Must be adapted to maintain the correct output impedance.
http://sound.westhost.com/project100.htm
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Ahh, thanks much fellas.