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Old 6th May 2010, 09:36 AM   #1
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Default MiniDSP, MiniDIGI, MiniAMP 2.1 Setup

Hello

Yesterday I started to setup my first tests with a complete solution from MiniDSP:

Click the image to open in full size.

The goal of this first try of this modules is:

- SPDIF input (MiniDIGI)
- Use the 4 channel amp (MiniAMP) to drive two Fostex FE83E fullrange speakers in 10W single end mode and one subwoofer (15" Goodmans Axiom) in 20W bridged mode
- Use of the digital crossover with all its functions (Subwoofer sum, crossovers, PEQ, delay and so on)

It is my first configuration. Later I plan to attach by I2S two 2 channel DAC's and use other amplifiers.

The thingy is playing right now very satisfying.

Some support issues, some minor bugs in the software, fast and friendly reaction of the MiniDSP team up to now.

I will post later the pictures of the jumper settings.

All postings to the topic, also other 2.1 projects/users are welcome in this thread!

But please restrict this thread to 2.1 setups only.

Franz

Last edited by Franz Gysi; 6th May 2010 at 09:39 AM.
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Old 6th May 2010, 03:03 PM   #2
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Good to see others MiniDSP set-ups. How is the 20 watts for the 15" sub?
What are your gain settings on the MiniAMP? I have changed from -3dB to +9dB. That was a bit to much, but one can finetune the gain settings in the software. Changing the gain improved the bass response quite a bit. It's now more precise. With -3dB the bass was vague and very soft.

Thanks for the idea of using the two channels in bridge config. Even though it's obvious I did't thought of that.
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Old 6th May 2010, 06:52 PM   #3
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Hello

Quote:
Thanks for the idea of using the two channels in bridge config. Even though it's obvious I did't thought of that.
It was the datasheet from the TAS5704 leading me to this idea.

Indeed, 20W bridged is better than 10W SE for the sub, but not enough in my case.

Before the MiniAMP I used a bridged LM3386 amp for the sub. This was better (for the bass at least).

Independent of the gain settings (actually I use +3dB), the power is insufficient for my sub. As I wrote in my first posting: later I plan to add my own DAC's directly to I2S and use my preferred amps.

What kind of potentiometer do you use? Logarithmic or linear?

I am used (from my last job with Studer) to use linear potis together with DSP's, and the software is using a log law.

But in this case, I am unhappy with my linear poti and I will try a log version this weekend.

Franz

Last edited by Franz Gysi; 6th May 2010 at 06:59 PM.
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Old 6th May 2010, 07:15 PM   #4
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I have NXP based class d amps (80 watt 8 ohm), and they are really good in the bass region. I have to remake them, so they are out of the system right now.

I use winamp to control the volume. I do have a 10 k log pot to insert as well, but I haven't tried it yet.
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Old 6th May 2010, 07:25 PM   #5
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Quote:
I use winamp to control the volume. I do have a 10 k log pot to insert as well, but I haven't tried it yet.
So, you control the volume in the digital area and are therefore reducing dynamics and resolution in low volume levels, where most listening is happening.

I tell you a studio rule:

In the digital area and in the whole audio chain, you have to use max possible levels.

In the analogue area, you have to calculate some headroom, but not in the digital area where you have to use the whole available room.

Conclusion:

Dont attenuate your signal in the digital area (only some dB's is no problem). Do it in the output domain!!!

A master volume control has always to be directly before the power amp, this is a MUST!

Did you ever had some other software (advertisements or other spam), using your digital sound channel, bypassing your winamp?

Great experience! For example at midnight, when your neighbours are sleeping :-)

Franz

Last edited by Franz Gysi; 6th May 2010 at 07:51 PM.
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Old 6th May 2010, 08:38 PM   #6
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Thanks for the info.

I have a minidsp with both the 4-way plugin and the 2.1 plugin.
I was planning to use in 4-way mode to help set crossover points and build passives and use the 2.1 from there.
I was going to keep it in the car, but I just got things settled in and really dread digging back into the car right now. So, I'll keep it in the house for the next few months until Rev ZZ of my car.

These little suckers are sweet for sure. I'm really interested in the miniAmp version, so I'm awaiting your review on that.

I was pretty much planning on using my iTunes software to control volume. In this case, I'd be all analog with my dsp. Do you see a problem with this, as opposed to having gain before your digital input with a miniDIGI setup? I've never noticed a problem with analog gain setups, myself.
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Old 6th May 2010, 09:03 PM   #7
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Quote:
Originally Posted by Franz Gysi View Post
So, you control the volume in the digital area and are therefore reducing dynamics and resolution in low volume levels, where most listening is happening.

I tell you a studio rule:

In the digital area and in the whole audio chain, you have to use max possible levels.

In the analogue area, you have to calculate some headroom, but not in the digital area where you have to use the whole available room.

Conclusion:

Dont attenuate your signal in the digital area (only some dB's is no problem). Do it in the output domain!!!

A master volume control has always to be directly before the power amp, this is a MUST!

Did you ever had some other software (advertisements or other spam), using your digital sound channel, bypassing your winamp?

Great experience! For example at midnight, when your neighbours are sleeping :-)

Franz
I know all of the above, but just haven't had the time to implement the volume control yet. I do know some technicians (pro audio engineers) who think that bit reduction at low level, was only a problem in the past when 16 bit was the standard. If volume control is done at 24 bit, then they argue, that controlling volume digitally is no problem at all.

I must admit I don't know at what bit rate, winamp is doing the volume control.

I don't use advertisment in winamp (some radiostations use that), so no bypassing winamp in my set-up. But I have tried it, and it's a pain when it happens.
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Old 6th May 2010, 11:03 PM   #8
qusp is offline qusp  Australia
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yes and doing volume in 32 bit really you dont have to think much about it anymore at all, unless you are listening at VERY low levels, you hardly even touch the useable dnr
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Old 7th May 2010, 09:58 AM   #9
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How do your jumpers look like in 3 channel?
I would expect channel 1 and 2 in BTL mode (jumpers in position to bypass capacitors), and channel 3 and 4 in SE mode (jumpers open). The I2S jumpers I would guess would be as in 4 channel setup.
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Old 7th May 2010, 10:23 AM   #10
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Hello

Yes, that's exactly the way I did it.

I will show here later all my jumper settings.

But: actually I have reversed phases between channel 3 and 4. It is not yet clear if it is a software issue from the 2.1 PEQ plugin.

I just reversed the speaker pins of one channel (could also be inverted on one channel in the plugin software).

As soon as this problem is fixed, I will publish my jumpers.

Franz
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