Preamp gain and matching with power amplifier

ben_

Active Member
Hello

I intent to use a separate preamp as an upgrade path from my integrated Yamaha AX-592 which is powerful enough for my speakers but I found the preamp section not so good for digital sources, because of not so good channel separation and rounded top and bottom frequency response (in direct mode). No turntable to use in this room so I did not compare phono sections from the pre amps.

The 2 pre-amplifiers I can get in my budget and needs are a NAD 116 and a Rotel RC-1070, but I cant figure out from the specifications if they will be compatible with the power section of my amp (the Rotel I think its ok)

The yam (power amp) specs states
- Main in Sensitivity/Impedance : 1V/ 30kOhms
- Pre out level/Impedance : 1V/1.2kOhms (I'll use that as reference)
- CD in Sensitivity/Impedance : 150mV/47 kOhms (For reference also)

The Rotel RC-1070 Pre spec states
- Input Sensitivity/Impedance : 150 mV/24 kOhms
- Output Level/Impedance : 1V/100 Ohms
So I calculated a max gain of 16.48dB, and it seems the output level is the same as the Yamaha built-in pre section, with a lower impedance.

The Nad 116 Pre spec
- Line level input impedance R+C : 20k +450pF
- Line Level Inputs sensitivity :
- ref. 0.5V : 80mV
- ref. 2V : 300mV
- Voltage gain : 16dB
- Output impedance (pre out) : 220 Ohms
- Maximum output level (pre out) : >12V

What does NAD means in their spec values and why are there 2 sensitivity refs ? I understand that you can drive it with 2v on the line level input and get more than 12v on the pre-out, which is 15.56dB gain. And if you drive it with a more common line level of 250mV you will get at max 1.5v on the output, and the NAD could also be compatible and wont saturate main inputs in the Yamaha.

Am I right with the maths ?

Besides that, if anyone as comments on these 2 pre-amps I'll be glad to read what you think :)

Many thanks
 
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I think I got it, the "ref." voltage in the NADs spec is the target output voltage, as there is aproximately a 16dB gain between 80mV and 0.5V, and between 300mV and 2V. If we extrapolate that to the input level in the Rotel preamp spec for a 150mV input level we also get a 1V output level.

Cheers
Ben
 
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The higher the output voltage of the preamp, the faster you get to your amps max output. so that could be 1/2 volume or a little more on the preamp volume knob. Lower gain just means you get to turn the volume knob further. Personally, it makes no difference to me where the volume pointer at near max amp output ends up. Your ears are your friends in this case

I am not familiar with this saturating of main inputs that your speaking of unless you mean pushing the amp into clipping faster?

I did not realize Yamaha was making equipment in Malaysia, I am only familiar with their Japanese products
 
I think I got it, the "ref." voltage in the NADs spec is the target output voltage, as there is aproximately a 16dB gain between 80mV and 0.5V, and between 300mV and 2V. If we extrapolate that to the input level in the Rotel preamp spec for a 150mV input level we also get a 1V output level.

Cheers
Ben

Yes, they've just done some of the voltage gain math for you.

Technically it would be pretty rare to actually overload the input of the attached power amp, because the level of signal that would push the amp output into clipping will almost certainly occur first. And most sane people stop about that point. ;)
 
No I dont intend to max it out :D

I was just a little scared with the 12v max level from the NAD Vs. 1v sensitivy on the main in on the power amp. I think, as long as it as a similar gain as the integrated preamp that should work fine with both pres
 
Regardless of the max capability, what you send out is still controlled by the volume.

I've measured my Yamaha C-80 preamp to be capable of more than 12V output, but it never goes that high in practice because usually the source level isn't high enough to facilitate that much. And, even if it was, the volume control just won't need to be turned as far to get to any given listening level so it's effectively self-limiting in that regard.
 
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