Would a preamp with 25 dB of gain be "too high" for McIntosh amps? ....

[joeinid]

Would a preamp with 25 dB of gain be "too high" for McIntosh amps?

Specifically the new MC1.25KW amps? I notice that McIntosh preamps have typically 12-15 dB of line level gain.

I know that having too much of anything is no good, especially gain. Thoughts? I know conventional wisdom says try it and see. Before I start down that road, I'd like to hear from the McIntosh experts if it's something that I should dismiss outright.

 

[whoaru99]

It won't hurt anything, but likely it will have a more narrow range of volume control between loud and soft. Can make it a bit harder to make fine adjustments of volume, particularly if the volume control is stepped rather than continuously variable/not stepped.

 

[joeinid]

Thank you, that’s what I was thinking as well. Technically I know it will work but probably not an “optimal” combination.

 

[c_dk]

Via what input? A phono gain stage should have a lot more gain than 25 dB. A typical phono gain stage would be 40 dB +, moving coil well over 50-60 dB.

Most higher end amp like to see a preamp that can put out over 2.5 volts, THX theater specs reigned that in by specifying 1.7 volts as the pro theater spec. It was not uncommon to find mass market receivers that could barely put out 1 volt whether 70s units or newer theater pieces.

The preamp output I have found to be more important than line level gain....phono is a different story.

 

[whoaru99]

The preamp output I have found to be more important than line level gain....phono is a different story.

Yes, ultimately it is the point, generally, to have enough pre out signal to drive the amp to rated output. But, also some cushion in gain in case you encounter a source with low output.

You can have low gain and still get a lot of preamp output...if the source has a lot of output. However, if the sources are weak, relatively speaking, then you need more of gain in the pre amp to get a lot of output. Phono is a good example of the latter.

 

[c_dk]

Without mentioning a brand, input or source component, Joe is asking a question that can not be precisely answered.

 

[twiiii]

25 db gain referenced to what input level. If its 200 mv that's fine, if it 1.7 volts we may have an issue. The more gain after the Volume control, the more noise, and the more possibility for distortion.

 

[joeinid]

Without mentioning a brand, input or source component, Joe is asking a question that can not be precisely answered.

For example, a McIntosh C1100 has a 15 dB line level gain. A Conrad Johnson GAT has a 25 dB line level gain, which to me can be too much depending on amp used. From experience, the CJ GAT that I used to have was a little noisy depending upon what amps I paired it with. I don’t remember if I ever tried it on the MC601s that I used to own. I know I would really need to try it. I would have expected some of you guys might have experimented with non McIntosh preamps to have a feeling about how much gain is too high for McIntosh.

It looks like I might end up with a C1100 anyway unless McIntosh introduces something new in the next month or two.

 

[joeinid]

PS,

I am not talking phono stage. They typically need 40-60 dB gain on their own.

 

[c_dk]

If your source puts out .75 volts at full content output and your amp needs 2.5 volts to achieve it's rated output, How much gain do you need?

As twii can attest to: at syd aud con we were taught to work the equation backwards....how much volume in dB do you need at the listening location and then how much gain at each stage, from microphone to amp to get that level with a speced headroom.

 

[damacman]

One of the challenges here is understanding that voltage specs are provided with respect to test tones and music doesn’t approximate that at all as it’s dynamic in nature. In 30 years of system building, I’ve come into only one case where the preamp would overdrive the next component in the signal path - and it wasn’t a power amplifier.

 

[whoaru99]

If your source puts out .75 volts at full content output and your amp needs 2.5 volts to achieve it's rated output, How much gain do you need?

...

~10.5dB.

 

[ron-c]

There is a simple answer. The preamp needs NO gain to drive the 1.25k amps as a high level input level such as CD player (2+ Volts) or tuner will drive the amp to full output. So in the case of C1100 it is unity gain, 2 volt in- 2 volt out, somewhere around 75% of volume and yes it can be turned up beyond this to 16 volts balanced.
If you have a very weak source you may use some of the preamps gain which is where the improvement in signal to noise ratio that McIntosh preamps offer will pay off.
The job of a preamp is to turn the volume down and switch inputs without adding any noise or distortion.
The phono gain of current McIntosh preamps is +40dB on MM and +60db on MC inputs.

Ron-C

 

[joeinid]

Thank you Ron. I fully understand your answer and appreciate the explanation.