I've been away for a week or so. Went on vacation. Just before I left, during, and on since I've been home I've read a lot about the mini-dsp. It seems the mini has some shortfalls that have been noted and that I've confirmed.
Stereodude, and several others, have been great contributors to this. I will try to list some references but the main point of this thread is to point out my
Tonight I triple checked settings and measurements. I'm driving DIY subs via a Peavy pro audio amp that requires 2.25 input volts to put out full power. My quest began to make sure i was getting full power out of my amp. I am.......... no problem there.
My Equipment -
Peavy IPR2 7500
6 Stereo Integrity D-4 subs
The problem is within the mini-dsp and its input side. Here's my procedure, triple checked. I know it's been posted a lot but bear with me.
I used the Home Theater Shacks guides to
1) determine clean output of my AVR and ( http://www.hometheatershack.com/forums/home-theater-receivers-processors-amps/35677-gain-structure-home-theater-getting-most-pro-audio-equipment-your-system.html#post317692
2) Set amp gain ( http://www.hometheatershack.com/forums/home-theater-receivers-processors-amps/35677-gain-structure-home-theater-getting-most-pro-audio-equipment-your-system.html#post317697
1) Determining clean output of my AVR
- Pure direct mode, all processing off (double checked, kept checking t-out the testing)
- MV of AVR set to max
- Sub trim set to max
- x-over set to highest
Result is 10.6 volts using DMM.
30% of 10.6 volts is 7.42. 7.42 volts out of the LFE RCA jack is ~ +1.5 on the M. Volume of the AVR. So next>>
2) Set Peavy amp gain
-Master Volume on AVR is +1.5
-Sub Trim - max (0)
-Again - pure direct, all processing OFF
-Turn amp gain to zero
-Play REW pink noise at -3.0 DB FS on the sub cal setting
-turn up the amp gain until clip lights come on steady--
Mini-dsp input is at 2.0 volt setting and is saturated during pink noise test used to set PA amp gain. Saturated at +0.7-0.1. <<--- this leaves NO ROOM for ANY BOOST on the filter portion of the mini dsp
Set subs to 75 DB using the AVR noise, UMIK-1, (calibrated by Herb at Cross Spectrum Labs), and REW SPL meter. The ONLY method of calibration to 75 DB is the reduction in sub trim on the AVR.Sub trim is now at -7, AVR is of course -0.
Test for minidsp saturation (+0 or above) using
- The REW tone AND a bass demo track w/ different songs, rap, jazz, techno, and some chest pounding bass.
- Using the REW test tone as noted above with the above settings
calibrated to the noted 75 DB and a 2.0 input voltage setting on the minidsp the mini read ~-15db.
-add 10 db to the sub trim on the AVR (10 db hot, right? everyone likes some hot bass now and then) and the mini reads ~ 4.5. THAT'S HARDLY ANY ROOM FOR ANY BOOST before the mini dsp is going to clip its inputs.
During the sub demo track (AVR MV @ 1.5, subs +3, or 10db hot, mini dsp input reached single digit negative numbers frequently. This is AT THE 2.0 volt setting.
While not clipping at those levels, REMEBER, there is NO boost applied. No LT, no nothing.
All the while I have plenty of volts from my AVR into the minidsp, and, GET THIS, more than 2.0 volts out of the minidsp. The minidsp is speced as having only 2.0 volts out regardless of input!My main complaint is ..... at the least minidsp should document some of these things. I'm going to have to play some of the movie demo discs at the same realistic demo volumes I did these tests at before Ill know if I can keep the mini-dsp with my AVR
As I mentioned I've been reading. Very few times have I seen mini-dsp give a sort of attitude to say...... towards their customers with questions RE: these issues. It seems you must 'beat them' at their game before you get any respectful answers.
I've seen read many times people suggest these exact findings need to be documented in the manuals. Yet it has not happened.Links
This is a good read-
Here's some sources, or if you're going to pick my words a part, some good reading to support my findings and complaints.