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miniDSP Low cost, modular Digital Signal Processor (DSP) kits for the DIYer from miniDSP.

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Old 2nd November 2010, 05:37 PM   #11
doug20 is offline doug20  United States
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Interesting point.

I guess doing a big boost down low for a sealed sub (+15dB ala LT Circuit) and connecting to a 4000Watt amp isn't going to work with the MiniDSP??

Last edited by doug20; 2nd November 2010 at 05:40 PM.
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Old 2nd November 2010, 05:46 PM   #12
Jozua is offline Jozua  South Africa
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Default Mini DSP

How does the Mini DSP compare sonically with the DCX ?

Thx !
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Old 2nd November 2010, 06:02 PM   #13
doug20 is offline doug20  United States
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Im comparing them back and forth for the past couple of weeks.

The mini DSP is as good as or better then the stock DCX in many areas. Im testing using analog inputs because that is what my setup needs.

The one bonus I have enjoyed is removing all the issues with RCA to XLR connections. Not worrying about the DCX gain structure is another bonus.

Learning bi-quads has been fun too, I want to try a 96dB Slope

I am concerned about the voltage wrt handling high end 4000Watt sealed subs.
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Old 2nd November 2010, 06:05 PM   #14
theresa is offline theresa  United States
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Thank you, that's reassuring. I am applying about ten db of boost at 20 Hz and don't know if the limited energy at that freq would overload it.
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Old 6th November 2010, 12:14 PM   #15
theresa is offline theresa  United States
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Have it all running now except for the center speaker. The bass is intense with the boost at 20Hz to the point that I will have to reduce the boost. My speaker drivers (except for the fifteen year old subs) still need a lot of break-in. Today I will be getting a speaker bracket for above the TV and hooking up the center. It has some of the best drivers made (ScanSpeak's top of the line midwoof and Discovery tweeter). I hope it doesn't make my Etons sound bad. Since they are crossed over/equalized with miniDSPs I should be able to match up their response.
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Old 1st April 2011, 12:39 AM   #16
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Quote:
Originally Posted by Davey View Post
Probably not. The inputs/outputs of the MiniDSP modules are limited to 900mV, and that's right in the neighborhood of where most amplifiers would be delivering their rated power. So, if your MiniDSP modules are feeding the amplifiers directly I'd say your chances of clipping the MiniDSP outputs are near zero. This is what I was referring to with the "well considered maximum levels" comment. Unlike the DCX (and other commercial units) a multi-channel post-volume control is not necessary with the MiniDSP units.

The Emotiva power-amps have 32db voltage gain (which is a bit more than usual) so your MiniDSP working voltage levels would be a bit less than they would otherwise and reduce the chances of clipping even further.

Obviously, if programming large EQ boosts in the MiniDSP you might get into trouble, so you have to be aware.

Cheers,

Dave.
Hi Dave,
I've been playing with MiniDSP revA for couple of months now and am very interested in your observation regarding not needing post-XO volume control. Do you just adjust the input level from pre-amp? or do you use the 10K Master Potentiometer connected to both boards to attenuate all channels digitally at DACs?
I would love to hear your input on this subject.

And second thing, i don't have an oscilloscope to measure the input voltage at which it starts clipping? I would love to know the maximum input voltage that i can feed it because i've been playing with various sources/audio cards which output anything from 0.7 to 2.77 volts and the digital meters inside the software never show any clipping(?!?), the music sound good to my ears , but the thought that I might be clipping it can't let me go?
(May be my ears are not as sensitive to clipping as I thought).

And if I understand correctly the output will always stay 0.9V even if the input is clipping?


I also noticed that the overall volume of my system with DSPs went down since my previous setup, probably because of lower output voltage from MiniDSP.

I used to run software XO and EMU 1820m connected to 6 channel Rotel RMB-1066 and had twice the overall volume level. I went back to re-measure my setup and it turns out the EMU was outputting 2.77V into Rotel amp with 1.5V input sensitivity and all these years it sounded GREAT to me!!!???? I can't trust my ears any longer. If it says input sensitivity of 1.5V do you think it could take up to 2.77V and not clip the input?
Obviously now with 0.9V output of miniDSP it sounds much quieter.(Rotel's volume on woofer is maxed out so I can't increase gain after miniDSP).

Thank you for your help!!!
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Old 3rd April 2011, 01:06 AM   #17
Davey is offline Davey  United States
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I've done it both ways. The preferable way depends upon your source level, power amp gain, speaker sensitivity, etc, etc. I think for most users with RevA units (that don't have the jumpered input adjustability) you're probably better off having your master volume control upstream in a "preamp" or level attenuator of some sort and disabling the miniDSP level control.

The maximum input voltage varies depending upon programmed EQ settings above 0db. If you just have notches, crossover filters, etc, etc, and no boosting EQ settings the maximum you can input is 0.9 volts RMS. (Any more and the outputs will clip.) Regarding the digital meters inside the software......there's a few threads on the miniDSP forum addressing the "issue."

I'm not sure why your overall volume level would reduce. The miniDSP output voltage levels should be very close to the input voltage levels on a Rev A unit with a nominal setup.

Cheers,

Dave.
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Old 5th April 2011, 08:43 PM   #18
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Thanks for quick reply,
I understand, as long as we keep the average listening level close to the clipping point we are OK (be it 0.9V or 2V, as long as the gain matching is done correctly to keep minidsp happy).

I also found unofficial specs on my amp which apparently accepts up to 5V on input which explains how I was able to listen with 2.77V and not get clipping.
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Old 20th November 2013, 04:16 AM   #19
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Originally Posted by OTMOPO3OK View Post
Thanks for quick reply,
I understand, as long as we keep the average listening level close to the clipping point we are OK (be it 0.9V or 2V, as long as the gain matching is done correctly to keep minidsp happy).
But what I can't figure out is that the difference between when I play music softly and when I play it loudly, is dozens of dB... so how do you set the level? Or do you just live with a diminished S/N at low levels?

(I'm not sure if this is in-principle different from all-analog systems.)

In this thread - as in many other places - people are asking for just a plain, simple, ordinary, regular harmonic distortion figure. Seems trivial to produce one... even better, to input 1kHz and show us the output spectrum. I haven't seen even one, no matter how many times I ask.

Why is that?

Ben
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Old 20th November 2013, 04:48 AM   #20
Davey is offline Davey  United States
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Quote:
Originally Posted by bentoronto View Post
In this thread - as in many other places - people are asking for just a plain, simple, ordinary, regular harmonic distortion figure. Seems trivial to produce one... even better, to input 1kHz and show us the output spectrum. I haven't seen even one, no matter how many times I ask.

Why is that?

Ben
Because it's just not that important.
I can easily generate one if you want, but what would you deduce from it? Simple harmonic distortions from gadgets like these are waaaay less than any speaker system you'd use them with. And there are a few experts that believe harmonic distortion measurements are completely meaningless anyways.

Cheers,

Dave.
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