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Old 28th February 2013, 12:03 PM   #21
gpapag is offline gpapag  Greece
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Dave, I only have 2x4 modules/plug-in.
I don't know what is happening with a 2x8
If you measure one of these, please report here.

George
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Old 13th March 2013, 03:55 AM   #22
minidsp is offline minidsp  Hong Kong
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Hello,

Here is a little update and thanks for your patience.

Our team compiled a new set of plug-ins with a new DSP structure allowing us to fix that metering bug. We also figured out a way to not "break" the configuration you may have had in the past. That's why it took us a bit of time to release all this to you.. :-)

Note that this issue only appeared on the miniDSP 2x4 based platforms (balanced/unbalanced).The 8x8, 2x8, 4x10, 10x10, nanoDIGI, miniSHARC, OpenDRC are all using a different metering that didn't that bug.

If you log-in to your user downloads section, you should have access to the Beta version.
IMPORTANT NOTE: Please take the time to read the "README" file that was included as part of the ZIP file. It does recommend to perform a backup of your old configuration first.

Hoping this info helps.

DevTeam
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Old 13th March 2013, 04:40 PM   #23
gpapag is offline gpapag  Greece
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DevTeam, thank you for responding back here.
Iíll download the beta version, check it and report in a couple of days.

Regards
George
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Old 15th March 2013, 10:03 PM   #24
gpapag is offline gpapag  Greece
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Default Report on using Beta version A. Behaviour of plug-ins ref. PC operating system

Report on using Beta version
MiniDSP 2 Way advanced Plug-in Version v1.09 (Release date 12/3/2013)
MiniDSP 4 Way advanced Plug-in Version v1.08 (Release date 12/3/2013)

A. Behaviour of plug-ins ref. PC operating system
See attachment for details.
The problem is that the beta version does not load old configuration .xml files.
I used an .xml editor e.g.
Download XML Notepad 2007 from Official Microsoft Download Center to read my old .xmls and copy the settings into .xml created with the beta version.

George
Attached Images
File Type: jpg Tables.JPG (124.6 KB, 241 views)
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Old 15th March 2013, 10:11 PM   #25
gpapag is offline gpapag  Greece
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Default B. Attenuation slider steps. C. RMS Meter reading with sinusoidal signal

B. Attenuation slider steps.
Each step of the input (and output) attenuation slider is 0.4db all along down to the maximum attenuation of –70db.
There are two numerical indicators for the applied attenuation in db.
One is just above the mute button always visible. This is the correct attenuation reading.
The other appears when we click with the screen pointer over the slider. This comes inside a blue frame and it’s indication is a bit in error, on some steps it read 0.1db below the actual attenuation.


C. RMS Meter reading with sinusoidal signal

Input and output RMS meters read correctly in db, following the voltage law [ db=20*LOG (V/Vref) ]
The Vref is the 0db of the meter which correctly represents the maximum signal before clipping.

For 2V boards:
0db at input meter corresponds to 2.173Vrms analogue input sinusoidal signal.
0db at output meter corresponds to 0.851Vrms analogue output sinusoidal signal.

For 0.9V boards:
0db at input meter corresponds to 0.981Vrms analogue input sinusoidal signal.
0db at output meter corresponds to 0.851Vrms analogue output sinusoidal signal.

Now, the top of the moving band can be used as a visual level indicator as it fluctuates close to the attenuator’s db scale.
Meter’s moving band disappears below –70db signal level.
For precise signal amplitude monitoring, the numerical signal level in db appears below the meters moving band (resolution 0.1db).

The output meter correctly registers the signal level reaching the output, that is, it is affected by any attenuation setting at the input and any boosting by the filters.
As long as the cumulative boosting by the filters in any specific frequency band do not exceed 24db, the output meter reading below 0db can be reliably taken as an indication for undistorted analogue output signal, that is unclipped and unskewed signal.

If boosting in any specific frequency band exceeds 24db, signal waveform will be skewed and this distortion does not reflect in the amplitude, thus output meter may continue to show negative db numbers. The logic is a bit complex and I will explain if you want, but always remember not to exceed this 24db cumulative boosting.

George
Attached Images
File Type: jpg Meter-attenuator readings.JPG (108.1 KB, 188 views)
File Type: jpg Attenuation Slider.JPG (15.5 KB, 180 views)
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Last edited by gpapag; 15th March 2013 at 10:15 PM.
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Old 15th March 2013, 10:13 PM   #26
gpapag is offline gpapag  Greece
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Default D. RMS Meter reading with dynamic music signal.

D. RMS Meter reading with dynamic music signal.

I find the RMS meters in this version to respond somewhat faster to dynamic signals than the meters in the previous version. But still, they do not have the ballistics of a peak meter.
A led indicator showing instantaneous peaks exceeding 0db (with holding time 1 sec) is still in need.

I spent some hours watching in real time and playing back pc screen video recordings, comparing behavior of miniDSP RMS meter to VU meter, peak meter, PPM and bit depth meter.
In case you don’t have a signal generator to set the 0db level and you don’t know the maximum output of your source, I would suggest:
For heavily compressed music, the input meter not to exceed –3db level (3db headroom). These recordings are close to 0db most of the time and have encoded already clipped material (good stuff actually for setting zero level if you don’t have a signal generator).
For relative uncompressed light music, the input meter not to exceed –12db level (12db headroom).
For good recordings (jazz, classic and opera fall in this category), the input meter not to exceed –22db level (22db headroom).
For live unprocessed takes, the input meter not to exceed –30db level (30db headroom).

George
Attached Images
File Type: jpg Comparing meters 1 screenshot.JPG (422.0 KB, 189 views)
File Type: jpg Comparing meters screenshot 2.JPG (431.6 KB, 182 views)
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Last edited by gpapag; 15th March 2013 at 10:28 PM.
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Old 16th March 2013, 09:50 AM   #27
gpapag is offline gpapag  Greece
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Doing the output measurements shown in Table 3 http://www.diyaudio.com/forums/attac...r-readings.jpg
I have to add two issues which are related to hardware, not to software.

1. The output noise of the miniDSP 2x4 board (Input shorted, open or with 50R across and no signal applied. Output loaded with 10k,) is 15mVpp 2MHz and harmonics.

2. Switch-off thumb:-200mV. Switch-on thumb: +2mV.

Duration of these thumbs depend on the capacitance of the psu that feeds the board.

Switch-off thumb is large and considering the gain of an amplifier connected to the output of the board, is a bad story for speakers. Always turn off amplifiers first, wait some tens of seconds and then turn off miniDSP board.

George
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Old 17th March 2013, 12:46 AM   #28
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Is this file still available?

Only file showing in my User Downloads section is a "miniDSP Xover 2way PEQ" dated 02/08/2011
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Old 17th March 2013, 05:22 AM   #29
boris81 is offline boris81  United States
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Composing the gain structure correctly on the miniDSP was indeed the hardest part of setting it up. Everything else was straight forward and intuitive. I did not realize that my input signal was clipping for some time until forum members repeatedly suggested that I it probably was.

I think a Gain Structure section with a simple step-by-step guide should be included in the manual. It should describe how to check your gain structure with a software signal generator or a wave file that can burned on a CD.

A very helpful addition to the software will be a clipping indicator. Fixing the peak meters will be fine but I think it will be great if there is an additional way to show an error when the system clips.

I lower the input level by the highest amount of gain I add later with filters. It was pointed out earlier that the numbers on the input level are not dB so my gain structure could still be wrong. I suspect that not a lot of people who use miniDSP know to do that. Some open baffle designs call for filters that add 40dB and more. I doubt that many people understand you can't really do this with DSP.
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Old 17th March 2013, 04:32 PM   #30
gpapag is offline gpapag  Greece
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Quote:
Originally Posted by KenTripp View Post
Is this file still available?

Only file showing in my User Downloads section is a "miniDSP Xover 2way PEQ" dated 02/08/2011
It is still in my User downloads section.


Quote:
Originally Posted by boris81 View Post
Composing the gain structure correctly on the miniDSP was indeed the hardest part of setting it up. Everything else was straight forward and intuitive. I did not realize that my input signal was clipping for some time until forum members repeatedly suggested that I it probably was.

I think a Gain Structure section with a simple step-by-step guide should be included in the manual. It should describe how to check your gain structure with a software signal generator or a wave file that can burned on a CD.

A very helpful addition to the software will be a clipping indicator. Fixing the peak meters will be fine but I think it will be great if there is an additional way to show an error when the system clips.
Boris I agree to what you say. Do you have some questions as to how you can test the gain structure within miniDSP board?



Quote:
Originally Posted by boris81 View Post
I lower the input level by the highest amount of gain I add later with filters. It was pointed out earlier that the numbers on the input level are not dB so my gain structure could still be wrong. I suspect that not a lot of people who use miniDSP know to do that. Some open baffle designs call for filters that add 40dB and more. I doubt that many people understand you can't really do this with DSP.

Input and output attenuators were always in db, as well as filters gain.
The meters were not.
With this beta version, everything is in db. Nice and correct.

If one is adding up to 24 db total boost in a specific freq range, he does not need to lower input level.
He can attenuate at the specific output where the boosted frequencies are rooted.
E.g.
Boosting 24db total at 50Hz.
Apply attenuation at LF output of 24db. No input attenuation required.
Of course you can apply this attenuation only at the input, but then you will attenuate the HF as well.
You can split the attenuation as you please, 2db at input, 22 at output if this serve your setting better.
Total attenuation will have to be of equal amount to boosting.



When exceeding this 24db boost, one has to apply attenuation at the input too.
E.g.
Boosting 40db total at 50Hz.
Apply attenuation at LF output of 24db. Required attenuation at input of 16db (16=40-24).
Of course you can apply 40db attenuation only at the input, but then you will attenuate the HF as well.
Again, you can split the attenuation, 20db at input, 20 at output if you like.
But do not apply 2db at input and 38 at output. You’ll have skewed output.
For ensuring skew free output, output attenuation shall be limited to 24db max.
The rest of the attenuation has to be applied at the input.This attenuation in db should be equal to total filter boosting in db minus 24db.

All this may be correct or false, depending if one has checked first the max voltage of the signal applied at the input of the mimiDSP board. This is the first and most important step for gain planning.

George
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Last edited by gpapag; 17th March 2013 at 04:36 PM.
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