I have a N.E.W. A20.1 that I purchased re-capped and serviced a few months ago. I just noticed that the right heatsink (right channel) runs about 20 degrees F hotter than the left heatsink (left channel). This was confirmed with a thermometer in multiple spots. The channels appear mirror imaged. Is this indicative of bias issue in one channel? Or is a bit of temperature variation potentially normal or typical with class A amps? This is my first true class A amp
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The only way to know for sure is to measure it and even if there is a difference that doesn't automatically mean there is a problem.
If an amp ran on say 45 volts in total (so either 45v single rail or 22.5v split rail) and one channel pulled 1.8 A and the other pulled 2.1 amp then you have dissipation of 81 watt and 94.5 watt which all things being equal would be quite noticeable.
Also things like any non symmetrical physical layout is also going to alter temperatures within a unit.
Measure it and then you will know.
If an amp ran on say 45 volts in total (so either 45v single rail or 22.5v split rail) and one channel pulled 1.8 A and the other pulled 2.1 amp then you have dissipation of 81 watt and 94.5 watt which all things being equal would be quite noticeable.
Also things like any non symmetrical physical layout is also going to alter temperatures within a unit.
Measure it and then you will know.
NEW A20.1 Stereo Power Amplifier Manual | HiFi Engine
Nirvana Electronic Works A-20.1. - this amp is essentially a Pass Aleph J clone
SOLD_N.E.W. A-20.1_Nelson Pass "Aleph ?" clone_RARE_pics added_$350
Nirvana Electronic Works A-20.1. - this amp is essentially a Pass Aleph J clone
SOLD_N.E.W. A-20.1_Nelson Pass "Aleph ?" clone_RARE_pics added_$350
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In the absence of a service manual I'll take a stab, I'm presuming this is the insides? (attached)
I see what would appear to be four emitter resistors (arrowed), you should find a similar voltage (at least on each channel) across each of these (on both channels)
Measure these 8 voltages (average them for each channel) and come back with your findings
I see what would appear to be four emitter resistors (arrowed), you should find a similar voltage (at least on each channel) across each of these (on both channels)
Measure these 8 voltages (average them for each channel) and come back with your findings
Attachments
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Attached are pictures of the left channel (as facing amp)
Can someone advise where to read voltage and what it should be? I assume that trimpot adjusts bias? This amp is specified to deliver 20 WPC into 8 ohms
Can someone advise where to read voltage and what it should be? I assume that trimpot adjusts bias? This amp is specified to deliver 20 WPC into 8 ohms
Attachments
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A small difference might not indicate a problem. 20°F probably deserves further investigation.
Maybe post a schematic and a pic or two -- maybe get some help? 😉
Cheers
edit: Looks like I'm a little slow on the uptake -- sorry for the duplication.
Maybe post a schematic and a pic or two -- maybe get some help? 😉
Cheers
edit: Looks like I'm a little slow on the uptake -- sorry for the duplication.