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Old 18th November 2010, 10:29 PM   #1
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Location: Coventry
Default Using MiniDSP's in a pre amp.. ideas.

I'm hoping to build some class-t amps and using some minidsp boards to make a four way active sleaker setup (initially I will be running my current 2 way speakers actively to get used to the minidsp setup and to provide a modular upgrade path).

At first I want to use my Denon AVC-A10SE as a dac and pre-amp feeding the analogue inputs of the minidsp boards. From what I have read on other peoples threads, this does provide a good sound, though from what I can see the optimal setup is full line level into the board, providing the biggest dynamic range and lowest noise floor.

So:

Later on, as a major upgrade I'd like to make a pre-amp with the minidsp boards integral.

I have read the user manual of the minidigi board and am I right in thinking I am able to configure the following:

Analogue input, into the minidsp board.
2*spdif input, into minidigi.
2*toslink input, into minidigi.
USB input (with a USB to I2S adaptor card), into minidigi (via I2S).

These would be switched with a 3 pole rotary switch.
When an analogue source is selected the first pole is L, the second R and the third closes the jumper on the minidigi card that runs the minidsp in analogue input mode (is this right, I'm having trouble getting my head around this).
When a digital source is selected the third pole closes the jumper to switch the unit to digital input, then the second or first pole closes the appropriate jumper on the minidigi card for that source. (in this case how is I2S selected? I would want to input the USB from a USB to I2S such as the ministreamer).

Would this input switching work?

After the minidsp I would need some sort of attenuation (which is why I want to know if this is possible now - so I can choose which version of the board to buy). I understand the minidsp balanced cards output at 2v? I think this would give me enough voltage to be able to use a passive potentiometer to control the level of all 8 channels, and have a high enough output to run the Hifimediy inputs (1.5v sensetivity, each with an alps pot to trim). I'd have to drop the minidsp outputs to single ended, I think you can do this with transformers, is that right?

I saw this on ebay and thought about stacking it up for 8 (or more!) channels: Balance XLR 23 Stepped Attenuator Potentiometer 10K Log on eBay (end time 19-Nov-10 13:16:54 GMT) Would this work?

I hope this thread makes sense, I'm just getting started at this stuff...

Regards,

Jai Stanley
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Old 22nd November 2010, 01:44 PM   #2
theresa is offline theresa  United States
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Join Date: Aug 2009
I have two miniDSPs in a box. One provides the crossover between mid-woofers and tweeters for the L/Rs, the second for the center and equalize my subs. The crossover from sub to the other fronts is handled by an Emotiva UMC-1. It all works very well and provides more control of the drivers than I ever had before. The miniDSPs are between the UMC-1 and the amps. I haven't experienced any noise issues whatsoever and the sound quality coming from the speakers is indistinguishable or better than not having the dsps in place and using a electrical crossover.

Last edited by theresa; 22nd November 2010 at 01:51 PM.
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Old 24th November 2010, 07:01 AM   #3
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Location: Coventry
Thanks Theresa. It is reassuring to know that the minidsp units sound good.

The thing I am having trouble getting my head around is the inputs to the minidsp. It seems that you can run I2S signals to the minidsp via the minidigi board, but my knowledge of I2S is very limited. If the USB to I2S converter (ministreamer) is set to master clock, the minidigi would have to be slave, correct? Then can the minidigi send an I2S signal to the minidsp boards if it is set to slave?

Hmmm... Complicated!

Regards,

Jai
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