2. amps-preamps
  3. 162026-525

Sensitivity Ratings on Preamplifiers or Integrateds vs. Amplifiers

Ok, so I am interested in a better understanding of gain issues. As I understand it sensitivity values for an amplifier provide the voltage needed to achieve rated output. I am not sure about the sensitivity rating for preamps, thinking it serves as the minimum required to drive the preamp. In the case of an integrated I have seen this spec provided for the included preamp and amplifier stages.  However for many it is not.

Specifically for my Line Magnetic 211ai it is specified as 200mV and I assume this is for the preamp stage.  This seems low and may be why, when driven by my DAC having 2V output, I need not turn the volume past 10 o'clock for sufficient loudness. I understand the volume position is no measure of the wattage one is asking the amplifier stage to deliver. 

I am seeking clarification /correction on my thinking. Thanks in advance!
mesch

Showing 2 responses by georgehifi

georgehifi's avatar
georgehifi
10,312 posts
 
mesch OP Of course high sensitivity often drives one towards a passive pre. That was what drove my question.

Oh! how thoughtful of you.

Your 211ai "could" very well be just a poweramp with a passive and input selector switch at the front, many tube integrates are.
You could lower the gain some by increasing just one small resistor in the feedback loop of the poweramp section, this will give you tighter bass if you need it also, or make thing too controlled to what you want or are used to. Cost is a couple of cents and a few mins work. If you can get a ciruit diagram I can show you what resistor to change. Or maybe the Line Magnetic people will show you?

This is how the tubes are used from what I found and it does sound like a power with passive volume
12AX7 double triodes used for voltage amplification while the driver stage is realized with pair of 12AU7 double triodes for splitting Output stage consists of two pairs of EL34

I would also change the 12ax7’s (very high amplification tube btw) used a lot for phono stages, to my favorite input tube a 12AY7 (lower in amplification)

Cheers George

georgehifi's avatar
georgehifi
10,312 posts
 
Specifically for my Line Magnetic 211ai it is specified as 200mV and I assume this is for the preamp stage. This seems low and may be why, when driven by my DAC having 2V output, I need not turn the volume past 10 o’clock for sufficient loudness. I understand the volume position is no measure of the wattage one is asking the amplifier stage to deliver.
Usually this means 200mV in for the amp to give it’s full power just before clipping, which is a bit higher sensitivity than normal, 500mV to 1.5v is usually the norm. Seeing you have a preamp stage in the way I would say it’s 200mV (.2v) with the volume at full.
You need to see if the volume pot is Logarithmic (A) or Linear (b) one, should be marked on it, then if 10 o’clock seems about right for a linear with 91db speakers, as linear doesn’t "to the ear and measure" increase much past 12 o’clock, like logarithmic does

Cheers George
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