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Old 2nd March 2012, 03:30 PM   #131
epa is offline epa  Netherlands
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thank you for responding dbmandrake.
i redid the whole voltage probe thingy ,and now everything is ok.
did a test with a 1% 5.6 and 6.8 ohm resistor ,and it comes close
fyi, the pic i posted in post 127 is a imp measurement of a ht sub.
already did a imp measurement whitout the voltage probe ,for ts parameters,that worked fine.
tnx
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Last edited by epa; 2nd March 2012 at 03:35 PM.
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Old 6th May 2012, 08:40 PM   #132
Safos is offline Safos  Poland
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Hello Guy,

To refresh the topic I would like to ask discuss two issue:

- Is anybody who use power amplifier to measure impedance and what is the voltage influence on resonace peak. Soundcard supply about 0,1-0,3 mV but I checked it with small amplifier 2-4V. I Expcected change in fs result but there was not big difference.

- My measurments are higher than technical information of speaker about 20-30Hz. I measured few speaker to avoid mistakes and in all cases look the same. Graph, peak, phase look very good but peak is moved. Do you knw the reasons?
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Old 2nd June 2012, 05:40 PM   #133
PRTG is offline PRTG  Latvia
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I just found a way of utilizing built-in microphone preamp in Presonus FireStudio Mobile soundcard for dual-channel mode measurements with ARTA. That means dropping the need for separate mic preamp. Is anybody interested?
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Old 3rd June 2012, 08:17 PM   #134
epa is offline epa  Netherlands
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it could be usefull to share it tnx.
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Old 4th June 2012, 01:13 PM   #135
PRTG is offline PRTG  Latvia
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Quote:
Originally Posted by epa View Post
it could be usefull to share it tnx.
Ok, have look at the attached guide. I've also sent it to ARTA for review, no comments so far. I hope it doesn't have major faults.

Jānis

Setting up Presonus FireStudio Mobile for dual-channel measurements.doc
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Old 7th June 2012, 07:19 AM   #136
epa is offline epa  Netherlands
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tnx janis,good stuff
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Old 7th June 2012, 07:28 PM   #137
Pano is offline Pano  United States
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Yes, good stuff. I'll have to try this with my M-Audio USB card.
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Old 9th June 2012, 07:08 PM   #138
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Default ARTA on FOCUSRITE SCARLETT 2i2 / TASCAM US122

The Focusrite Scarlett2i2 (&TASCAM US 122MkII) is 2in-2out unlike Presonus FireStudio Mobile which has more than 2 ins allowing to connect the way PRTG has described well. Since the mic preamp out is internally connected to line in, resistor R5 cannot be inserted in between. This means proper value for ext left preamp gain cannot be entered in ARTA without having to compromise. ARTA application note no. 1 states on page 6 " There can be other way for the realization of switch box in cases when soundcard has embedded a high quality microphone amplifier (i.e. TASCAM USB-122) or when soundcard has phone output that can drive relatively low impedance. Such cases will be described in other application notes." When can such a note be expected? I emphasize: I do not want to compromise by putting R5=0 and let the 2 channels be driven by different source impedance. Any help in this regard is highly appreciated.
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Old 10th June 2012, 11:45 AM   #139
PRTG is offline PRTG  Latvia
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Quote:
Originally Posted by soundrex View Post
ARTA application note no. 1 states on page 6 " There can be other way for the realization of switch box in cases when soundcard has embedded a high quality microphone amplifier (i.e. TASCAM USB-122) or when soundcard has phone output that can drive relatively low impedance. Such cases will be described in other application notes." When can such a note be expected? I emphasize: I do not want to compromise by putting R5=0 and let the 2 channels be driven by different source impedance. Any help in this regard is highly appreciated.
I'm not familiar enough with Focusrite Scarlett2i2 (&TASCAM US 122MkII), still it may not be necessary to have more than 2 inputs as I'm utilizing only one besides Mic input. Important is the capability to have at least three internal DAW channels and to have ability to separate mic-in and have it mapped directly to one of at least two outputs independently. Not necessarily it should be done through "mute all except mic" (or "solo" for mic-in) setting in mixer. For example, for some cards it could be possible to have routing switch that maps mic-in to main-out or phones-out directly and ignoring the mix completely. Presonus don't have it so I used Mixer as the only mapping choice.

Generally you need to see at least 3 pairs of ASIO (DAW) channels in ARTA but use only 2 of them there and third one leave alone for mic (in isolated way). Then route out- DAW channel defined in ARTA to one output and out-channel of mic-in to the secondary output.

If you're confident that it can't be done with particular card then you'll obviously need separate pre-amp for mic.

I had a quick look on Focusrite answerbase

Have a look what choices you have at The Routing Section for monitor-out and phones-out and see if you have more than one DAW choice here.

Wishing success in either way,

Jānis
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Old 10th June 2012, 05:59 PM   #140
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Default ARTA on FOCUSRITE SCARLETT 2i2 / TASCAM US122

From Focusrite Answerbase:
Can I use Scarlett MixControl with the Scarlett 2i2?
No, the Scarlett 2i2 is not compatible with Scarlett MixControl. All of its controls are hardware based instead.
The mic preamp section is supposedly good and I do not want to spend on another mic pre
How about sketching the mic preamp section of the unit, calculate the output impedance and insert the necessary resistor? I think it is built around NJM2122 but the task is daunting as it is completely SMD.
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