[lmf22]

I have a Primare I21 integrated amp and I connected a Velodyne Impact Mini to its pre-amp output, but the signal seems to be too low.  It's so low that the subwoofer won't even power on (it has a auto-on/off feature).  I can turn up the volume of the integrated amp, but then the music would be too loud.  Is there anyway to amplify the signal of the pre-amp out?  Something like an inline attenuator, but opposite?

 

[Bones13]

I suppose you could put a line level Pre-amp device, but would not think that would be particulary useful.
 
I am assuming that you are running 2 interconnect cables, both right and left from the pre-out to the R/L inputs on the sub.
 
I am also assuming that the subwoofer is working correctly, and not malfunctioning. (swap in a different amp?)
 
If those are true, and things still don't work, I would use the speaker outs to the sub, then continue from the sub to the speakers.  You will also be able to utilize the crossover circuit in the sub to no send the lower frequencies on to the speakers (low pass frequency dial). The pre-out portion would not be used.
 
Lastly consider an "attenuator" on the speaker side to dial back their response to the volume knob.  I am pretty sure this will hurt the performance though.

 

[lmf22]

Yes, both left and right channel from pre-out are connected to the line-in of the sub.
 
Sub is working correctly.
 
I was talking to the person who sold me the Primare amp, and he suggested that I run the speaker outs to the sub, in parallel to the main speakers (i.e., running an addition set of speaker cables from the speaker terminals to the sub).  I didn't want to do Amp --> Sub --> Speakers because that will require an additional set of expensive speaker cables.  Did some Google searches and it seems like doing this (running parallel with a sub) will not increase the load of the amp.  So, I got some Radio Shack 18-gauge speaker cables and ran it to the sub.  Seems to work fine now.  The volume control on it sub is now at it's usual position, when it was paired with my previous amp. 

 

[MadCow]

I am looking at the specs of your Velodyne sub:
http://www.velodyne.com/products/specs/ImpactSpecs.html
 
... and it seems to me that it is expecting a full line-level signal instead of a pre-amp signal on its RCA inputs?
 
If that's the case, then this would explain why you are not getting enough volume on the sub.
 
The sub appears to have another input labelled "LFE" -- if I am not mistaken, I think this is the one that would be expecting pre-amp-level signals and you should be using this instead?

 

[lmf22]

If I connected the amp's Tape Out to the sub, it is too loud.  I get too much bass even at half-notch above zero.  If I use a 12-db attenuator I can get it to about 1 notch and get enough bass. 
 
The manual does it can be connected to pre-amp out though.  It says:
"if using line level connections from a preamp or signal processor, use both Left and Right inputs from your preprocessor or preamp and connect them to the Left and Right inputs on your subwoofer."
 
By LFE, it means the LFE output of an AV receiver.  It does not have a separate LFE input.  The only inputs I see in the back are one pair (left, right) RCA and left-right speaker-level inputs. 
 
Here are two screenshots of the manual.

 

 

[MadCow]

Quote:

The manual does it can be connected to pre-amp out though.  It says:
"if using line level connections from a preamp or signal processor, use both Left and Right inputs from your preprocessor or preamp and connect them to the Left and Right inputs on your subwoofer."
 

 
Note quite -- see highlighted part. It says if using line level outputs from a preamp, not preamp level outputs from the preamp.
 
Looks like you either need a line level output from your integrated amp (which you say it's too loud -- perhaps you need to adjust the level and/or crossover on your sub?), or use the speaker terminals.
 
 
(edit/clarification This means your sub is expecting a constant, line-level signal from the amp. The signal from the pre-outs are variable and usually much weaker than a full line-level signal.
 
This means they are expecting you to either:
1) use line level signals, and control the sub's volume via its independent volume; or
2) use the speaker terminals, which should have the proper volume levels
 
Seems like the ideal connection is via speaker terminals, so you do not have to fiddle with the sub's volume each time you want to listen to your music at varying levels of loudness.