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Old 2nd January 2013, 06:28 PM   #1
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Default miniDSP pre-amp & volume control idea

Im looking for an elegant solution to house a miniDSP, with control for source, and for volume..


I have found this maker of beautiful of passive pre amps. Who can make custom units.

Click the image to open in full size.
www.akustyk.com - High Quality Passive Preamplifiers

My plan was to have three digital inputs, with a selector knob on the front.

With the DSP inside, would run into the miniDIGI board. power over usb.

Then to two volume control attenuator controlled by one master knob on the front.

Any thoughts? Would allow digital source selection, master volume control after the DA conversion. All in one handy small usb powered box.
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Old 3rd January 2013, 07:51 AM   #2
Calvin is offline Calvin  Germany
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Hi,

IŽd ask the supplier, what kind of VC circuit is used, resp. how the output impedance of the VC behaves over volume setting.
If the output impedance is not low and constant, it wonŽt be a top solution as VC regardless of resistor image or quality other than for very short cable runs.
Other than that, looks the build quality rather basic, with all those visible and protruding screws and unscreened -not even primitively drilled- cablingm, in a non-screening casing and differing color of Frontplate and knobs. But then again the pricetag seems ok for the actual VC-device.

jauu
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Old 3rd January 2013, 12:51 PM   #3
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Forgive me, what is VC?

The minisdp would output at full volume,do you think this night be too low for the passive pre-amp?
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Old 3rd January 2013, 03:38 PM   #4
Calvin is offline Calvin  Germany
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Hi,

VC stands short for Volume Control.
The Q wether or not the MiniDSP puts out enough signal voltage depends on the required input signal voltage level of the following device and rather not on the VC, assuming that the lowest attenuation -or insertion loss of the VC- stays close to 0dB/100%. The VC does nothing else but attenuate the input signal. Most amps or devices will require less than 2Vrms. Afaik the MiniDSP can put out either 0.9Vrms unbalanced or 2Vrms balanced. 2Vrms should be enough for all typical applications but 0.9Vrms might be a bit tight.

jauu
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Old 3rd January 2013, 04:27 PM   #5
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Good luck on your project. The same idea could be done using the volume feature on the basic minDSP board, and use analog inputs.
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Old 3rd January 2013, 04:56 PM   #6
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Quote:
one handy small usb powered box.
I suggest you a proper & clean linear psu inside that box instead of usb power.

A 5V linear psu will not only provide power to miniDSP + miniDigi boards but could power a usb to i2s or spdif interface like M2tech Hiface as well.

So my suggestion is to use a little bigger box and leave some room for a future linear psu.
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Old 3rd January 2013, 08:19 PM   #7
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I am using a wooden enclosure in order to house the following:
miniDSP & miniDigi.
M2teach Hiface Two usb to coaxial interface.
2 x linear 5V psu's (one for dsp boards and the other for the Hiface)

I am also planing to include 4x buffer - gain stages in order to much the low output of minidsp 0,9V to my amps (input 1,5V sensitivity).

I am using the digital volume of miniDsp.

I am not very happy from the back side of my box, but i usually look at the front so it doesn't matter.

I believe that wooden enclosures sound better than aluminum.
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Old 19th January 2013, 11:57 AM   #8
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Update*

I have purchased a miniDSP 2x8, with the Vol-FP and Digi-FP.

This i'm hoping will work as a complete digital pre-amp/active XO with digital input selection, volume control.

I have a rather unique design for a case, I'm hoping to start putting it together soon after the dsp arrives. But made from solid oak and fumed oak.

I just need to buy a power supply...
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Old 23rd January 2013, 05:04 PM   #9
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Here is the idea for the case.

A switching power supply in its on box.

2x8 in another, with top mounted turned volume control.

Oak and fumed Oak.

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Old 4th February 2013, 10:15 AM   #10
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Heres some wooden inspiration for you Studio Au
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