Difference in SPL among amps

[slipperybidness]

The input sensitivity on the NAD 314 is even higher than I expected in post #14. It is 0.97mV which is VERY high. It was probably done to compensate for the units low power rating of 35 WPC. The higher sensitivity will make it seem more powerful.

This confirms what you are experiencing.

Lower sensitivity is better. I would take a 200mV sensitivity over a 0.97mV sensitivity any day of the week.

When I'm working out my gain structure for DIY electronics, I typically shoot for ~29dB gain and 1Vpp input sensitivity. From my view, for my needs and design goals, this tends to be the sweet spot.

 

[<eargiant]

When I'm working out my gain structure for DIY electronics, I typically shoot for ~29dB gain and 1Vpp input sensitivity. From my view, for my needs and design goals, this tends to be the sweet spot.

I was referring to line level inputs. A quick rule of thumb is that a 200mV input sensitivity is the most useful (middle of the road) for most external modern sources with a ~2V output.

SNR is also better with the lower sensitivity (higher number). A lower sensitivity (higher number) will also allow for a greater range in the volume pot.

 

[PENG]

Thank you all.



I know, it's just that I wanted to upload the doc from hifiengine, but it's to big. The model number is 314 for the NAD. Since the file is too large, could you please read it on hifiengine? I don't want to be demanding, but I couldn't upload it.

The NAD314's service manual does not tell you what kind of volume pot they used and hifiengine does not have the PM5005 service manual. Suffice to just compare their specs, now that we know we are comparing the 5005 to 314.

For CD input:

NAD sensitivity - 170 mV, 0.97 V, input to power amp for rated output of 35 W, power amp gain 24.6 dB

Marantz PM5005 service manual not available, but based on PM6005:

input sensitivity - 200 mV, 1.18 V (calculated) input to power amp for rated output of 40 W (adjusted down from the 45 W PM6005), or 23.63 dB

The overall gain under the assumptions I made are quite similar, the NAD would be about 1 dB higher at the most.

So I would say the difference in MV positions are most likely due to the different characteristics of the master volume pots. The NAD 314, being 23 years old, it probably has a more linear taper characteristics, and the Marantz PM5005, a 2013 model, likely have a logarithmic type MV pot. I can be totally wrong, of course.

 

[PENG]

When I'm working out my gain structure for DIY electronics, I typically shoot for ~29dB gain and 1Vpp input sensitivity. From my view, for my needs and design goals, this tends to be the sweet spot.

FYI, according to the service manual, the NAD 314 power amp gain is 24.6 dB, for the preamp, it should be about 15.13 dB, calculated from input of 170 mV (that is 0.17 V) and output of 0.97 V (again, according to the SM).

I also like the 29 dB number for the more power amps, say 120 W and above, but 24.6 dB is quite adequate, for the 35 W NAD.. It is only 24.1 dB for the Marantz PM6005, likely the same for the PM5005.

 

[slipperybidness]

I was referring to line level inputs. A quick rule of thumb is that a 200mV input sensitivity is the most useful (middle of the road) for most external modern sources with a ~2V output.

SNR is also better with the lower sensitivity (higher number). A lower sensitivity (higher number) will also allow for a greater range in the volume pot.

It's been a while since I've done this type of work and calculations, but by my memory, 200mV for full output seems way too sensitive to me.

Like I said, I worked up 1Vpp for full output as ideal in my most recent situation. I also had to spec the feedback resistors to get the proper gain structure for my project.

You are also not specifying whether you are talking about Vrms or Vpp. To me, Vpp makes the most sense when running through the calcs.

Regardless, I agree that 0.97mV sensitivity does not seem like a good design decision. I'm wondering if those units were wrong and it should be 0.97V.

Edit: Yeah, check post #24, 0.97V, not 0.97mV. And, 0.97V lines up with my comments of 1Vpp has been the sweet spot for me.

 

[killdozzer]

It would be cool if all amps allowed the users to select which Gain they prefer.

My new NAD has this. Not the 316, but the 2700THX. Under input level:

 

[<eargiant]

It's been a while since I've done this type of work and calculations, but by my memory, 200mV for full output seems way too sensitive to me.

Like I said, I worked up 1Vpp for full output as ideal in my most recent situation. I also had to spec the feedback resistors to get the proper gain structure for my project.

You are also not specifying whether you are talking about Vrms or Vpp. To me, Vpp makes the most sense when running through the calcs.

Regardless, I agree that 0.97mV sensitivity does not seem like a good design decision. I'm wondering if those units were wrong and it should be 0.97V.

Edit: Yeah, check post #24, 0.97V, not 0.97mV. And, 0.97V lines up with my comments of 1Vpp has been the sweet spot for me.

This may help explain what I was talking about:

http://www.hi-fiworld.co.uk/amplifiers/75-amp-tests/150-sensitivity.html

 

[M Code]

This may help explain what I was talking about:

http://www.hi-fiworld.co.uk/amplifiers/75-amp-tests/150-sensitivity.html

In reference to the subject link..

"WHAT IT TELLS US
Sensitivity is a measure of the magnitude of input signal need for the amplifier to produce full output, at maximum volume. This tells us what signal sources the amplifier can handle, and produce full output if required. But it also tells us where the volume control is likely to be set is use and how quickly volume rises when it is turned up. This affects a user’s perception of power." [/quote]

"The amplifier to produce full output, at maximum volume..."
I don't agree with the selection of terms...
In my experience the input sensitivity refers to a set input level typically 1V RMS @1kHz, Volume Control set to 0dB then the amplifier should output its "rated power & THD"... To me "full output" means max output, and we know well a quality audio amplifier can exceed its "rated output" significantly. For example, the amplifier may put out 100W/channel, @1V RMS 1kHz input but if the Volume Control is advanced beyond 0dB. Then its output powercan/will increase significantly beyond 100W/channel. As well as the THD should go simultaneously..

Maybe I am just nitpicking certain terms but I felt it was necessary to state the above...

Just my $0.02...

 

[slipperybidness]

This may help explain what I was talking about:

http://www.hi-fiworld.co.uk/amplifiers/75-amp-tests/150-sensitivity.html

That all makes sense. And, yeah, my work that I was referring to did not include low signal sources, so less sensitivity made sense for me.

I'm still not sure that I agree with the 400mV number that they throw out in that article.

But, then we are getting down to "design decisions", and I made different decisions on my design for my gear and based on the resources that I had available (college classes and reference books).

EDIT:
I think that's the takeaway: There is not a "one size fits all" solution to this question.

And, just for completeness, we should mention that we also must consider the other end of the problem--full output WITHOUT clipping.

 

[slipperybidness]

In reference to the subject link..

"WHAT IT TELLS US
Sensitivity is a measure of the magnitude of input signal need for the amplifier to produce full output, at maximum volume. This tells us what signal sources the amplifier can handle, and produce full output if required. But it also tells us where the volume control is likely to be set is use and how quickly volume rises when it is turned up. This affects a user’s perception of power."

"The amplifier to produce full output, at maximum volume..."
I don't agree with the selection of terms...
In my experience the input sensitivity refers to a set input level typically 1V RMS @1kHz, Volume Control set to 0dB then the amplifier should output its "rated power & THD"... To me "full output" means max output, and we know well a quality audio amplifier can exceed its "rated output" significantly. For example, the amplifier may put out 100W/channel, @1V RMS 1kHz input but if the Volume Control is advanced beyond 0dB. Then its output powercan/will increase significantly beyond 100W/channel. As well as the THD should go simultaneously..

Maybe I am just nitpicking certain terms but I felt it was necessary to state the above...

Just my $0.02...

To me, I take "full output" to mean "the maximium peak to peak output, just before clipping"

 

[lovinthehd]

I'm still not sure that I agree with the 400mV number that they throw out in that article.

That also struck me as odd.....so just checked several of my manuals and they mostly (3 avrs) have line inputs spec'd at 200mV (my Sony avr has 500mV spec), as did my little Lepai integrated amp....altho neither of my old 2ch pre-amps showed an input spec in mV (but did have impedance spec'd) except for the phono inputs...

 

[slipperybidness]

That also struck me as odd.....so just checked several of my manuals and they mostly (3 avrs) have line inputs spec'd at 200mV (my Sony avr has 500mV spec), as did my little Lepai integrated amp....altho neither of my old 2ch pre-amps showed an input spec in mV (but did have impedance spec'd) except for the phono inputs...

D'oh!

I get it now, I was talking about input sensitivity to the AMP stage, not the pre-amp stage!

I think we're all pretty much in agreement now.