Did a search and only 1 post saying 75mv at the test points, and on another site the person said 100. No service manual on the net that I can find and Krell won't answer so much appreciated if someone can confirm. I believe mine is the earlier one with the Krell metal badge not the silk screened logo.
Thanks in advance
Thanks in advance
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I guess there's not much info out there. I set it at 75mv and after an hour of warmup it sounded a bit hard so I upped it to 97. Sounds pretty stellar now, much smoother and naturally detail presentation. After running for 2 hours the heat sinks right at the case measure 57c and at the out fins 51. Does that sound liveable for an amp that supposed to run the first 50 watts Class A ?
I design my own amps so have to come up with my own bias setting.
I usually set it to just enough to kill crossover distortion.
Always seems to sound OK.
I usually set it to just enough to kill crossover distortion.
Always seems to sound OK.
Thanks. I don't have gear to measure distortion so I was just curious if this temp is too hot for a normal life span. Maybe I'm in the ballpark. If I set it to measure 93 it's a bit raspier sounding.
The lower the bias the less heat is lost in the heat sinks.
You could run it at full power and monitor the temperature if you are worried about it.
You could run it at full power and monitor the temperature if you are worried about it.
Thank you. If a measurement is taken right on the transistors do you know how hot they optimally run?
On my own designs with my minimal bias setting the heatsinks dont get warm at all.
Increasing the bias for a better sound is ok so long as it doesnt over heat the amp when you use it on full power.
Increasing the bias for a better sound is ok so long as it doesnt over heat the amp when you use it on full power.
I listen at pretty moderate levels so it will never be taxed. I can keep my hand on the heats inks but it's very warm and I know these don't run cool at all. Time will tell thanks for your advice
What is the resistance of the Emitter Resistors on each Output Transistor??
The smoothest transition from Class-A mode to Class-AB mode occurs with ~26mv combined drop across both the Re resistor on the NPN output and the Re on the PNP output. So,
26mv / 2*Re = XXXma for optimal transistion bias.
A bias greater than "optimal" will supply more Class-A watts, but there will be more A-->AB crossover distortion than with the "optimal" bias current at high wattage demands.
OTHERWISE...for home use.... the lower 75ma bias that the Websites recommend is probably best.
The smoothest transition from Class-A mode to Class-AB mode occurs with ~26mv combined drop across both the Re resistor on the NPN output and the Re on the PNP output. So,
26mv / 2*Re = XXXma for optimal transistion bias.
A bias greater than "optimal" will supply more Class-A watts, but there will be more A-->AB crossover distortion than with the "optimal" bias current at high wattage demands.
OTHERWISE...for home use.... the lower 75ma bias that the Websites recommend is probably best.
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