AR P315HO down-converter adjustment

Xmitr · 31st December 2008, 01:28 AM

On an AR P315HO speaker I have a few questions about the adjustment of the down converters.
-What input and output levels I should I aim for when adjusting RP1 and RP2?
-What is the load impedance that the amp drives? (I don't have the speaker with me and want to connect a power resistor for testing)
- is the 500 watt output a continuous level, ie. what maximum level should I not exceed.

Hope you can help.
Don Whyte

Xmitr · 1st January 2009, 09:15 PM

After some thought I figured I didn't need to consider the input and output levels. I connected a 5 ohm 50 watt power resistor and with an oscilloscope adjusted the down converters so the + and - rails tracked about 7 volts above the audio signal. Per Jack Hidley's suggestions. Thanks

The amp is rated to produce 500W rms but I didn't drive it anywhere near that.

I am seeing about a volt of some ultrasonic noise at 67 KHz and about 800 Khz in the (-) down converter and it's feeding through into the output stage. It appears at the inputs to the comparator U4-B and looks like a subharmonic of the 135 Khz oscillator, and not properly filtered in the (-) down converter. But it might be partly be parasitic feedback from the output - I can't determine. The 800 Khz also appears in the (+) down converter but is filtered out before the output. In any case it's beyond the audio range. It would be quite a bit of work to check all the filtering components. Any ideas?

31st December 2008, 01:28 AM	#1
Xmitr diyAudio Member Join Date: Sep 2008	AR P315HO down-converter adjustment On an AR P315HO speaker I have a few questions about the adjustment of the down converters. -What input and output levels I should I aim for when adjusting RP1 and RP2? -What is the load impedance that the amp drives? (I don't have the speaker with me and want to connect a power resistor for testing) - is the 500 watt output a continuous level, ie. what maximum level should I not exceed. Hope you can help. Don Whyte

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1st January 2009, 09:15 PM	#2
Xmitr diyAudio Member Join Date: Sep 2008	After some thought I figured I didn't need to consider the input and output levels. I connected a 5 ohm 50 watt power resistor and with an oscilloscope adjusted the down converters so the + and - rails tracked about 7 volts above the audio signal. Per Jack Hidley's suggestions. Thanks The amp is rated to produce 500W rms but I didn't drive it anywhere near that. I am seeing about a volt of some ultrasonic noise at 67 KHz and about 800 Khz in the (-) down converter and it's feeding through into the output stage. It appears at the inputs to the comparator U4-B and looks like a subharmonic of the 135 Khz oscillator, and not properly filtered in the (-) down converter. But it might be partly be parasitic feedback from the output - I can't determine. The 800 Khz also appears in the (+) down converter but is filtered out before the output. In any case it's beyond the audio range. It would be quite a bit of work to check all the filtering components. Any ideas?

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