Bottlehead Forum

Bottlehead Kits => Legacy Kit Products => Quickie => Topic started by: jbraveman on November 26, 2009, 02:10:21 PM

Title: Optimal gain setting
Post by: jbraveman on November 26, 2009, 02:10:21 PM
I'm running a squeezebox in front of my quickie.  The squeezebox has a variable amount of gain.  The quickie is in front of 200 watt monoblocks.  Is it better to run the squeezebox louder (and the quickie quieter) or the other way around?  I'm concerned that I'll loose some "tubeyness" if the gain on the quickie is relatively low.  Is there a "sweet spot" with regards to the gain?
Title: Re: Optimal gain setting
Post by: Paul Birkeland on November 26, 2009, 02:37:05 PM
If you have access to a scope, you might have a look at square waves out of the Squeezebox at various levels.  My general thought on this is to run the Squeezebox pretty hard, but not so hard that you don't have sufficient range of motion in the Quickie volume pot.  Also, there is the possibility that too much gain from the Squeezebox will artificially raise the noisefloor.  In any event, do some experimentation and I'm sure you'll find a balance that you'll like. 
Title: Re: Optimal gain setting
Post by: Paul Joppa on November 26, 2009, 03:45:41 PM
I second the recommendation to experiment.

My white paper on signals and noise is on the community page of the Bottlehead site, and gives some ideas about setting levels for optimal balance between overload and noise floor. But it does not much address the small-signal nonlinearities that characterize some solid state (op-amp) circuits and all digital approaches. I'm not familiar with the details of the Squeezebox analog circuitry, i.e what kind of amplifiers are used, or how the level control is implemented, so I don't know what would be best for it - hence I also recommend trying various combinations to see what works best. Please post back if you do experiment, it will help many others as well!
Title: Re: Optimal gain setting
Post by: Grainger49 on November 27, 2009, 02:39:26 AM
In the absence of a scope, try this, set the quickie volume at 12 o'clock.  Increase the gain from the Squeezebox till you get the volume you want.  The 12 setting on the Quickie should not distort.
Title: Re: Optimal gain setting
Post by: jbraveman on November 27, 2009, 03:39:40 AM
Thanks for the repliles.  I will experiment a bit.  I don't have a scope to work with.  My concern is that I would be amplifying more noise with squeezebox set at a lower level.  It is, of course, convenient to have a remote to control the volume.  The D-A converter in the squeezebox (Wolfson 24 bit) is pretty good, but I'm leaning toward a  separate at some point.
Title: Re: Optimal gain setting
Post by: induna on November 28, 2009, 10:33:55 AM
Isn't volume control on the Squeezebox performed in the digital domain? If so, you will generally be better off setting the Squeezebox volume at 100%, so no data is lost (although digital volume controls are much better than they used to be).
Title: Re: Optimal gain setting
Post by: russtafarian on November 30, 2009, 08:43:04 AM
I'm also using a Squeezebox with my Quickie.  I adjust the Quickie level so I can use the SB digital volume control in the 75 to 100% range.  Sounds great!

Russ