Total System Gain Question

[greg788]

I am considering an amp with 25dB of gain and 575mV input sensitivity for rated minimum output, and considering a preamp with 18dB of gain. So total system gain would be 43dB. My speakers are 88dB efficient.

Is too much gain for a 2V line level DAC source? I don't know what the input sensitivity of the preamp is. I worry I'll be stuck in the bottom (non-linear) portion of the volume pot due to the total gain ...

I don't have a feel for this since I'd been using an integrated amp forever.

 

[DimitryZ]

I am considering an amp with 27dB of gain and considering a preamp with 18dB of gain. So total system gain would be 45dB.

Is this adequate or excessive gain for a 2V line level DAC source? I don't know what the input sensitivity of the preamp is.

I don't have a feel for this since I'd been using an integrated amp forever.

One other question: the manual for the amp says its gain is 18x. I calculated that to be 27dB of gain. Did I do that correctly or is it something else?

It's more than enough gain. My all Emotiva amplification chain has similar overall gain and my speakers are pretty insensitive at 84dB. I rarely listen at greater than -30dB from 2V sources.

18x is more like 25dB - 20*log(18)

https://www.silisoftware.com/tools/db.php

 

[davidsrsb]

2V +43 dB is 281V, so you must have a lethal power amplifier or more likely too much gain

 

[david ellwood]

It kind of depends on the sensitivity of the speakers

 

[John Phillips]

I am considering an amp with 25dB of gain and considering a preamp with 18dB of gain. So total system gain would be 43dB. My speakers are 88dB efficient.

Is too much gain for a 2V line level DAC source? I don't know what the input sensitivity of the preamp is. I worry I'll be stuck in the bottom (non-linear) portion of the volume pot due to the total gain ...

If that preamp gain is from line-level input to output with volume control all the way up then yes - it looks like far too much gain overall.

In your calculation you should note that a normal but good volume control potentiometer in a preamp will function adequately at 20 dB or maybe 25 dB of attenuation (-20 dB to -25 dB of gain). As you write, if you have to set the volume control lower than this you will likely run into problems with channel balance and finding that very tiny rotation leads to big volume changes.

To me, problem number 1 is the preamp. For a line level input you definitely need no more than 10 dB of gain and 0 dB is usually fine. May I suggest you check the 18 dB gain in detail. If I had 18 dB in a preamp, I would be looking at adding attenuator(s) in the right place(s) to tame what looks like a wild gain distribution.

 

[Darren L]

I recently watched an interview with Robert Koch who builds the Robert Koda Takumi preamp and poweramps. One of the things he talked about was preamp gain, I think his has 6db of gain, he also mentioned the Audio Research Ref preamp which has 8db of gain.

In the past whenever CD players were introduced and became popular a common issue was too high an output resulting in inadequate variation on the volume control and a vast difference became obvious when switching between a digital and analogue sources. This of course lead to attenuated interconnects and plugs. Whether they're a cure or a sticking plaster is probably something that's been discussed before but IME I found it to be beneficial.