2. amps-preamps
  3. 1109824073

Volume level mystery - can you solve it?

I recently replaced a pair of Linn LK power amps (85 and 140, in passive biamp mode) with the much more powerful Linn 2250 amp (just one). My preamp is a Linn Kairn. I have noticed that in order to achieve the same volume levels with the 2250 as I was getting with the 85/140 combo, I need to crank the Kairn volume setting much higher. By way of example: on a scale of 1-100, 50 used to be my normal listening level, but to achieve that level I now need to turn the Kairn up to 70 or higher. The Kairn only goes up to 100, but with the new amp, everything below 60 or so is very, very quiet. After 70, the volume ramps up pretty quickly, whereas with the 85/140, the distribution seemed more of an even straight line graph. Does anyone have any idea what this is all about? Are amps just calibrated differently? If anything, I would have expected the 2250 -- a more powerful amp -- to produce higher volume at lower settings, but the reverse seems to be true. Any thoughts about this would be much appreciated. I am a little worried that something is wrong with the amp, but aside from the volume issue the sound seems good. Thanks.
kdl6769
slappy
903 posts
 
maybe a higher impedance on the amp's input?
eldartford
4,262 posts
 
Gain of the more powerful amp (volts out per volt in) can be lower than the less powerful amp. It's just that the more powerful amp will continue increasing it's output beyond the voltage where the less powerful amp quits. Like the story of the rabbit and the tortoise. The tortoise wins.
gs5556
1,235 posts
 
Not knowing the speaker, I would guess the 2250 amplifier and speaker setup is running less efficient than the 85/140 biamped setup. With only one amplifier connecting both high and low drivers, the overall power consumption of the speaker to produce sound has to be greater beacause of the crossover inefficiency. Most of the amp power is wasted as heat. Even though the speaker produces so many db per watt, the actual watt that gets through is maybe 20% of the power drawn.

With the biamped setup, each amp feeds the high and low drivers separately. Since the output doesn't split in the crossover and gets converted to heat, more amp output makes it to the drivers. Also, since each amp feeds either an inductor (woofer) or a capacitor (tweeter), the overall impedance is greater at lower tweeter/higher woofer frequencies - so the (bi)amps are operating at lower current outputs which enables them to better maintain their power ratings. So at lower volume levels, more of the power is actually consumed by the drivers, especially if the gain of all three amps are the same.

The 2250 will be louder at higher volume pot settings because the extra power capability will eventually push its way through to the speaker's drivers.
gregm
3,405 posts
 
Also think of the new amp's input sensitivity -- it may not be the same as the older amps'.
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