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Old 11th March 2010, 09:54 AM   #1
minidsp is offline minidsp  Hong Kong
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Default miniDIGI + miniAMP: An SPDIF amplifier

While miniAMP modules are about to come out from manufacturing, we wanted to explain/clarify a bit how miniDIGI and miniAMP cards work and fit in the miniDSP product concept.

In essence, these cards are supposed to be I/O cards for the miniDSP kit, i.e. providing the input/output configuration you need for your setup. Stack it up on top of your miniDSP kit, and you can easily build a DSP processed custom product. Does it mean you need a miniDSP kit to use them? The answer is no, both miniDIGI and miniAMP were designed to work as standalone products.
- In the case of miniDIGI, an on-board micro-controller automatically sets up the SPDIF/Toslink transceiver at power-cycle. Therefore making sure that miniDIGI can run on its own, receiving a wide range of digital audio sample rate with automatic switching.
- As for miniAMP, just feed him any I2S signal and this little puppy will automatically detect the sampling rate and operate in the correct mode.

So here we are, miniAMP stacked on top of a miniDIGI card, and off you go with a custom SPDIF/Toslink all digital amplifier module!

Hope this makes sense and let us know if you have further questions.
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Old 11th March 2010, 10:24 PM   #2
gooki is offline gooki  New Zealand
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A quick question about the mini amp. For car audio use will it require a regulated power supply, or will it work fine of the fluctuating power one experiences in an in-car environment?

Also, what's the expected price?


Thanks.
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Old 13th March 2010, 08:02 AM   #3
minidsp is offline minidsp  Hong Kong
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Quote:
Originally Posted by gooki View Post
A quick question about the mini amp. For car audio use will it require a regulated power supply, or will it work fine of the fluctuating power one experiences in an in-car environment?
Also, what's the expected price?.
In answer to your questions about the regulated PSU, being a closed loop power stage architecture, the output voltage (& therefore power) will remain the same of power supply variations. That's a big plus compared to typical open loop design. Another advantage is how its good Power Supply Rejection Ration (60dB) will reject noise from a dirty power supply.

Now this being said, we never hooked up the amplifier to a car and tried to run some audio test on it. (Fitting the Audio Precision in the car, being a bit troublesome.. ) So not being aware of how bad the power can be in a car, It's hard for us to answer that question.

As for pricing, it will be released next week when power supply are back from Manufacturing on Monday.
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Old 16th March 2010, 11:09 AM   #4
minidsp is offline minidsp  Hong Kong
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Quote:
Originally Posted by gooki View Post
Also, what's the expected price?
Thanks.
Few days later, many burn-in sessions later, the miniAMP is now officially shipping!

For more information about pricing and complete datasheet, have a look at the miniDSP webstore.

Any questions, feel free to ask.

Tony
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Old 16th March 2010, 07:45 PM   #5
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Just ordered a set for evaluation today. There's one thing that's not clear to me though from the datasheet. How is the gain on the amplifier set? I see a couple of gain configuration pins for it -- do we just supply some resistance to set the gain, or is gain preset for the amplifier? There's also some 'config' pins in the datasheet.

Thanks,
Scott
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Old 18th March 2010, 02:31 PM   #6
minidsp is offline minidsp  Hong Kong
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Scott,

Thanks for your order. The gain of the amplifier is done by switches, not through a resistive network. You have 4 gain settings (-3/3/9/12dB) to toggle between. The reason being that gain would typically be controlled from the miniDSP in digital domain. However in your case, you'll have to control it at your digital audio source (whatever that is) OR on the outputs of the amplifier. Makes sense?

As for the Config Pins, they are meant to configure the amp between 2ch and 4ch mode. There is a Sub PWM output as well that can be used but it would require a PWM amplification stage. We may consider to release that at a later stage (for a sub out)...

The miniAMP manual will be available this week end so all this will be clearer by then.

Hope this makes sense,
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Old 19th March 2010, 05:59 PM   #7
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Just to make sure before I order: I can use a miniDIGI together with a miniAMP (without the miniDSP) in order to make... a Power DAC? Sounds great! I've been waiting for such a thing for ages! I'll likely order your dsp product too in time - unfortunately I have a Mac and will have to wait. :-)

thanks,
Jeremy
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Old 20th March 2010, 01:46 AM   #8
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My final concern regarding the MiniDSP is whether or not its output can directly drive my amps without having to employ a preamp in between. Your new miniamp raises a question in this regard; Could the miniamp in 4-channel mode with -3DB gain and individual level controls for each channel serve as a "preamp" for this purpose? Certainly would make a nice unit for ditribution to the amps.

Pete
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Old 20th March 2010, 03:25 AM   #9
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Quote:
Originally Posted by Diomedian View Post
Just to make sure before I order: I can use a miniDIGI together with a miniAMP (without the miniDSP) in order to make... a Power DAC? Sounds great! I've been waiting for such a thing for ages! I'll likely order your dsp product too in time - unfortunately I have a Mac and will have to wait. :-)

thanks,
Jeremy
Jeremy,

Yes you indeed use a miniDIGI + miniAMP, without a miniDSP. Your digital audio source feeding the miniDIGI which will route the audio to the miniAMP unprocessed in 2ch mode. Note however that in this configuration you'll either need to have control of your volume at your digital audio source (whatever that is) or post amplifier with a 20W volume control.

Mac support is slowly making its way... just a lot slower than we envisioned as Mac platforms are not as easy to program (at least for this application)

Hope this makes sense,
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Old 20th March 2010, 04:40 AM   #10
minidsp is offline minidsp  Hong Kong
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Quote:
Originally Posted by Peter Menting View Post
My final concern regarding the MiniDSP is whether or not its output can directly drive my amps without having to employ a preamp in between. Your new miniamp raises a question in this regard; Could the miniamp in 4-channel mode with -3DB gain and individual level controls for each channel serve as a "preamp" for this purpose? Certainly would make a nice unit for ditribution to the amps.

Pete
Hello Pete,

Could you please clarify what makes you believe that the miniDSP will not be able to drive your amplifier? It will help us to answer that question.

We and our end users been using miniDSP while driving a wide range of amps (Tube/Tripath/Small amp modules) to build multi-way active speakers and haven't had any issues so far. Maybe have a look at our miniDSP datasheet for more info about output impedance and output voltage and compare it to your amp specs.
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