Sensitivity Ratings on Preamplifiers or Integrateds vs. Amplifiers

Thanks, George. I wasn't aware of the 12AY7 tube. I believe there is another tube, having a 4 digit designation,  that can replace the 12AX7 for lower gain. Maybe the same tube with different designations?

I am currently not in the mood to get overly concerned about the gain issue specific to this amp to the point of modifying or even tube rolling it. I purchased it slightly used at a reasonable price to use as an educational tool to better understand the power requirements of my speakers, and to play with all tube amplification. It is serving me well for that. will likely move on from it. 

Currently using the Aric Audio pre into a SS amplifier. Should I purchase a all tube integrated I believe I would look into those having a active tube preamp stage. Otherwise a tube amplifier to rotate with a SS one using my preamp.

One thing about the LM 211ai, I believe it to be better suited to a vinyl system where the sensitivity could be an asset with lower gain cartridge and phonostage.  Either way, vinyl or digital it sounds very good with my Sterlings. I will have a better feel for how it compares with my preamp/amp combo one I reincorporate it into my system. Still getting familiar with the LM.

If there is any standard for sensitivity it might be 1.23V (+4dBu), but I remember few decades ago 0.3V (-10dBV) was common.  By using higher sensitivity they tried to save money - more gain in amp, but less gain stages in all sources.

http://www.harmoniccycle.com/hc/music-26-+4dBu-10dBV.htm

I'm not sure 1.23V (+4dBu) applies to power amps, since my Benchmark AHB2 offers three selectable input levels: 2V (8.2dBu), 4V (14.2dBu) and 9.8V (22dBu).  I use 9.8V, that they recommend.  At higher input level cable electrical noise pickup is lower in relation to signal while gain stages were moved from noisier environment (power amp) to cleaner one (pre-amp).   

My Benchmark DAC3 HGC has nominal 2V (8.2dBu) analog inputs sensitivity.  Benchmark usually knows what they're doing so perhaps the "standard" is 2V and not 1.23V.  Can anybody clarify?

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

George,  thanks for your response. I usually get around to looking inside a piece of equipment I own to see what I purchased. Never in a hurry to do so with something new (to me). My LM211 is just past the broken in stage. I will play with the volume control, maybe using the SYS to allow more full sweep, to try and discover whether it is linear or log. 

Regarding the sensitivity spec, I believe 0.2V is way over sensitive for full power from an amplifier. I believe 0.5V is also. Of course high sensitivity often drives one towards a passive pre. That was what drove my question.

Is the 200mV spec for the preamp or the amp stage in this integrated?

If for the amp, is the preamp passive and the small signal tubes only input and driver tubes for the amp? It seems that no gain would be required from the preamp stage.

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

@yogiboy  Thanks for your response. I do own a SYS. I am really not overly concerned with the volume position as I am wondering how much power I am reaching at the position. I don't feel I would accomplish much adding another potentiometer and pair of cables between DAC and amplifier.

 I am going to play with my SPL meter measuring at different levels. My Tannoy Sterlings have a sensitivity of 91dB and don't drop below 5 ohms impedance. If I take that at face value, knowing the distance between the SPL meter and the speaker I might be able to get a rough guess of what power I am using. I am not interested in pushing the amp to the point of distortion. 

I have had integrated amplifiers that exhaust the amplifier stage at 12 o'clock volume. It seems the preamps in these integrateds have gain to accommodate low phonostage outputs. Often too much gain for digital sources. These days 2V from a DAC is the minimum. So many preamps have far more gain than needed for digital sources. 

As an aside to this, My Aric Audio Tube preamp has variable gain, 0-20dB. I find this a useful feature. Of course not in use with the LM 211ai.  

@mesch
Your thinking is correct. The input sensitivity of that Line Magnetic is on the low side. Since you don’t have a volume adjustment on the DAC you can always add a schitt SYS if you want to use the volume control in the higher range on the Line Magnetic!
https://www.schiit.com/products/sys