[uzziah]

is the only reason to use a lower gain than 11 that you will be able to use more of the sweep of the volume knob? or, does sound quality increase with a lower gain?

 

[dsavitsk]

I think that quality should not change, but many volume pots don't track well at low volumes, so being able to turn them up is a good thing. This also, it makes it easier to listen at low volumes.

 

[DaKi][er]

most opamps have increased bandwidth at lower gain, but this is in the 100khz-mhz regions

but then if you're using the mint/pimeta/ppa/m3 designs, they have the inner loop at high gains to force the bandwidth down so changin the overal gain wont do anything for bandwidth here

 

[skyskraper]

i experimented with gain in the last pimeta i built, first with gain 11. running my akg k240's it sucked. 3/4 of the pot travel was unlistenable. but with my hfi500dj1's it was completely unlistenable for all but the very beginning of the pot travel.

i kept swapping stuff round til i ended up with a gain of about 5.3 (perfect for the akg's, and i still got 3/4 of the pot movement for my ultrasones) . running that from the headphone out of my ipod or mixer its perfect. but with the headphone out on my sound card, line outs on that and my mixer its not quite enough. so up it will go to 6ish.

my philosophy when building amps for myself is to socket the resistor locations now, and then swap as required. then for the gain, i'll basically have my source at its normal listening level (if it isnt a straight line out with no adjustment) then max the pot on the amp and find a level just below ear splitting or headphone ripping. i like to be able to have full control over my amp across the whole range of the pot.

 

[peranders]

Quote:

Originally Posted by uzziah is the only reason to use a lower gain than 11 that you will be able to use more of the sweep of the volume knob? or, does sound quality increase with a lower gain?

The answer is: have as much gain as it's appropiate. Not too much so you'll get noise, not too little so you won't get high enough volume. Bandwidth is most of the time not a problem, nor is distortion.

Gain of 2-4 is normal and up to 10 if you have a weak signal source and/or high impedance phones.

 

[mono]

I suspect there is a sound quality issue at play, because use of the POT at high resistance (ie- barely rotated) does lower the signal strength. Better to keep signals nearer maximum and ajust gain to get near full pot travel, typically around 3, up to 8 with crossfeed and poor source. I have no qualms about limiting the output to the point my ears don't throb though, your hearing or philosophy may vary.

 

[miketriple]

using my e3cs with my mint, the default gain of 11 made my volume knob pretty pointless.. i could barely turn it before it was silent or deafening.

i just lowered it to increase the sweep i could use..

 

[jasonhanjk]

I use the gain of 2 for 2 reason.

1. Lower noise.
2. Better resolution on the volume knob.

 

[morsel]

Jason is right about lower noise and greater useful volume control range. Don't use more gain than you need. If your headphones are low impedance high efficiency types and you never use high impedance phones, a gain of 2-4 should be plenty.

 

[tangent]

The only reason you see a gain of 11 so often is because the resistor values are easy to come up with, and it'll work with just about any combination of headphones and sources.

I can only think of one of my 'working' amps (as opposed to those on a shelf after having been built for some more specialized purpose) that has a gain over 6, and that one is scheduled to be lowered as well.

 

[uzziah]

Quote:

Originally Posted by morsel Jason is right about lower noise and greater useful volume control range. Don't use more gain than you need. If your headphones are low impedance high efficiency types and you never use high impedance phones, a gain of 2-4 should be plenty.

unless i'm using opa637's (which i will in MMM by the way). then i suppose i'm limited to gain of 11 for stability. somewhat unfortunate considering i only use MS-1's, but i really enjoy the burr-brown laid back nature with my grados. i could certainly use 627's, but i already have the 637's. oh well. i get nearly half of the sweep of the volume knob with my 637's in my gain 11 pimeta.

 

[amb]

Quote:

Originally Posted by uzziah unless i'm using opa637's (which i will in MMM by the way). then i suppose i'm limited to gain of 11 for stability.

I have tested the M³ with OPA637 in the L & R channels, and was able to get good and stable operation at a gain of 6 (Morsel's excellent PCB layout and good supply bypassing plays a role, I'm sure). However, that's probably too close for comfort and maybe not everyone would be as lucky, so I recommend a minimum gain of 8 for these opamps on the M³.

 

[Quacker]

How would you put a gain adjuster on a pimeta board so that you could change the gain without having to switch the resistors?

 

[Syzygies]

Look at the schematic; R3 and R4 form a voltage divider. So does a pot. You swap the dual pot in for the dividers. Leave in a resistor so the lowest gain is 1, not 0.

I'd consider it exceedingly dangerous to follow someone else's recipe here. I'd write myself directions three days in a row, and if they all agreed, I'd go for it.

In other words, I wouldn't try this unless I could figure it out for myself. There are too many variables for someone else to anticipate.