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PR-800 ClassA/AB Amplifier Kit
PR-800 ClassA/AB Amplifier Kit
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Old 28th December 2016, 10:20 PM   #21
kronzilla is offline kronzilla  Belgium
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Default PR-800 amplifier

I was wondering how the amplifier would perform in class A?

Or are there better designs?
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Old 28th December 2016, 10:49 PM   #22
roclite is offline roclite  United Kingdom
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PR-800 ClassA/AB Amplifier Kit
Hi kronzilla,

I cant answer your first question but its not very likely with the standard off-the-shelf amplifier purchased from on-line retailers. There are too many potential issues - oversensitive (unnecessary?) protection circuit, bad design, poor implementation to name but a few. I might finish off the project I started last February to see if my re-designed SAB-800 version lives up to its higher performance LTspice simulation figures or should be relegated to the disco amp or mains re-generator duty that many use it for.
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Old 29th December 2016, 10:13 AM   #23
kronzilla is offline kronzilla  Belgium
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so the spec's are a little over-rated?
I'm curious to hear how the project is going
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Old 29th December 2016, 12:04 PM   #24
roclite is offline roclite  United Kingdom
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PR-800 ClassA/AB Amplifier Kit
Definitely over-ambitious in all respects . I am generally quite interested in single-board amplifier modules since messing around with Maplin Mosfet amplifier modules in the 80's. I will take a look at my LTspice simulations and stripped-down PR-800 to see how much work is required to get a working channel. However, I will pretty much always be constrained by the possible poor layout and limited ability to hack the original design too much. I quite like the idea of having the on-board PSU capacitors though the designer could easily have put a full-wave rectifier and Zobel protection network on-board too (see what I mean ). I believe that reducing inter-wiring or tracking to the bare minimum can pay sonic dividends through reduced resistance and thus higher peak currents. Something that was used to good effect on the Cyrus amplifiers, amongst others, and probably one reason why they sound so good. Watch this space for further details but not too closely
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Old 9th February 2017, 06:03 PM   #25
sergio1968 is offline sergio1968  Ukraine
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Hey. Prompt me for some circuitry assembled PR-800? Whose clone?
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Old 21st February 2017, 07:19 PM   #26
sergio1968 is offline sergio1968  Ukraine
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Launched today, the Chinese miracle ... Supply voltage +-60 volts. The bias current set about 55 mA (15 mV to 0.27 ohm resistors). heatsinks idle half an hour later warmed up to 50 degrees is 60. Prompt, and this temperature should be?
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Old 22nd February 2017, 10:25 PM   #27
phase is offline phase  United States
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I try and make sure the heat sinks are below 48 degrees centigrade myself.
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Old 23rd February 2017, 05:04 AM   #28
sergio1968 is offline sergio1968  Ukraine
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Thank you, I will continue to adjust.
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Old 23rd February 2017, 02:31 PM   #29
roclite is offline roclite  United Kingdom
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Join Date: Dec 2011
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PR-800 ClassA/AB Amplifier Kit
Hi Sergio, as a minimum mod you should replace the 51R 1/4 Watt resistor immediately in front of the heatsinked driver transistor MJE15033 for one of higher power rating, at least 1W but 2W even better. If you are running the PR-800 at high bias, this resistor will cook and eventually fail.
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Old 23rd February 2017, 02:56 PM   #30
sergio1968 is offline sergio1968  Ukraine
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I'm understood, thank you . A PR-800 circuit is not? I plugged in instead AC6-12 DC12V.
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