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Old 21st March 2008, 12:02 AM   #31
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Default Tranny Voltage too low.

Little Higher than 24V. Go for 50V or more, no higher than 84V. That's your problem. Check the datasheet. You almost have it. Get a Tranny from a dead old amp if you can. Keep the power supply seperate from the amp itself, then you can replace it later if you need to. Use the best 1000 uF caps in the amp itself so you don't have to replace them. The power supply can be very simple. Don't listen to these "snubberised" perfectionists. All you need is a Bridge rectifier for the power supply. Sorry if this is a little short.
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Old 21st March 2008, 06:39 AM   #32
Electrons are yellow and more is better!
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Quote:
Originally posted by AndrewT
Oops,
50k pot has an output impedance that varies from zero to 12k5.
This may ruin the performance of any amp that follows a passive attenuator.
I thought it was 25 k when the pot is in the middle.
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Old 21st March 2008, 08:54 AM   #33
AndrewT is offline AndrewT  Scotland
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Hi Peranders,
when pot is just above middle of the resistance range, i.e. -6db, the resistance seen by the receiver is the lower leg of ~25k05 in parallel with the upper leg of ~24k95 in series with the source resistance of ~100r. The actual
The two routes to ground are effectively 25k05//25k05 giving a source impedance of 12k525 for Rs=100r. Any other position of the volume pot will present a lower impedance to the receiver.

Output impedance=[Rpot+Rs]/4
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Old 21st March 2008, 09:15 AM   #34
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Quote:
Originally posted by AndrewT
a pre-amp
or
an active volume control
or
a buffer after the pot
and
maybe a buffer before the pot.

Can you recommend an active volume control for my setup, or a preamp?
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Old 24th March 2008, 01:14 PM   #35
Electrons are yellow and more is better!
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Andrew, of course, you are right.
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Old 24th March 2008, 01:16 PM   #36
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Default Preamp

Dont't worry about the preamp until you have the power amp going.
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