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Amp Dummy Load

Sal1950

Sal1950

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The Chicago Crusher
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amirm said:
Should work. Just don't touch it during use as it may get quite hot depending on how much power you pump into it.
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Well the 545 talks of 10 minute pre-conditioning at 1/3 power/ 33watts, and the 5400 at full power 120watts for 5 minutes. In any case I thought the 300 watt spec of the 8 ohm resistor to be sufficient but yea probably not a good idea to touch it in any case. LOL
Thanks
 
Do your amps have a problem, or are you just trying to create one?
 
Scrutinizer you are funny! But true though, setting amp bias needs to be down slowly and over time/temperature, and if its fairly close, I would not touch it given the age of the pots etc. I did try a long time ago to bias my old hafler amp closer to class a but all it did was make the darn thing get too hot and no change to the sound.
 
RayDunzl said:
Do your amps have a problem, or are you just trying to create one?
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LOL, Neither, just that seeing as all 5 are at a minimun of 20 years old I thought it might be interesting to see what there is to see after all that time, how much drift there's been, etc.

amirm said:
I don't feel good at all cooking the thing at full power for 5 minutes. Recipe for potential damage. Just run a bit till it is warm and good and then set it.
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tomelex said:
setting amp bias needs to be down slowly and over time/temperature, and if its fairly close, I would not touch it given the age of the pots etc
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Yes I agree, thanks. I wonder how far off from the spec'd 7mv you'd live with before an attempt to adjust was made? I'm thinking +or- 1/2mv would be called good enough but......... Never tweaked SS amp bias before. I did my VTL tube amps a couple times a year and they could be held to a fairly stable 300-325 of the 300mv spec?

Fitzcaraldo215 said:
You wimp!
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You just want to see the smoke come out. :eek:
 
Theres bias and offset, offset at the output of the amp, I would say if it is within plus or minus 10mv its fine, up to +/- 20mv as well would not touch. Bias is setting the idling current in the output transistors, consult your service manual for both adjustments. Solid state should hold its settings for decades and be within spec. Millivolts of offset will not even get passed your crossover components in your speakers, its not that important until you deal with headphones.
 
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tomelex said:
Theres bias and offset, offset at the output of the amp, I would say if it is within plus or minus 10mv its fine, up to +/- 20mv as well would not touch. Bias is setting the idling current in the output transistors, consult your service manual for both adjustments. Solid state should hold its settings for decades and be within spec. Millivolts of offset will not even get passed your crossover components in your speakers, its not that important until you deal with headphones.
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Thanks bud. Offset is self-adjusting. Bias spec for the 545 is 7mV, +/- 1mV. We'll see how they measure
 
What a group of supportive friends I have here. :eek: LOL
 
1528693896026.png
 
The bias setting is just like setting the idle speed on a carb.

Too low, no good.
Too high, no good.
 
Bias setting occurs in many audio forums.
 
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