MiniDSP, MiniDIGI, MiniAMP 2.1 Setup

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Hello

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

An externally hosted image should be here but it was not working when we last tested it.


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
 
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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.
 
Hello

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

I must a little bit explain this issue:

The whole setup is working very linear now (I have a simple acoustical/digital measuring system).

But I still miss some control in the bass area with the 2 channels in bridged mode, compared to the LM3886 driver I used before.

Next step in my tries: I will attach the LM3886 to the analog out of the MiniDSP board to drive the bass.

I fiddled around with the gain jumpers of the MiniAMP board.

With my linear poti, every setting above 0dB is too much to find normal listening levels with the poti.

BTW: the poti is working with a delay guessed about 0.5 seconds, because the limited performance of the DSP in favour to have fast RMS meters.

Franz
 
Franz, can you tell us some details about your subwoofer? (Sensitivity, 8ohm? etc.)

Do you think the miniAMP is giving the sub all it has to give? I wonder if there are gain setup problems.



I have 2 AESpeakers TD18H+ (99db sensitive) subwoofers that I'm considering powering from a miniAMP. I currently amplify with a 100W per channel home theatre reciever, and even with only 1 sub running it is more than enough for inside my house.


Thanks :)
 
fb

Only limited data are available for my sub:

An externally hosted image should be here but it was not working when we last tested it.


I configured my desk as an open baffle. The 15" Goodmans (8 Ohm) is mounted in the backwall. Also sidewalls are mounted to the desk. The desk stands 10 to 15cm away from the wall.

It simply needs more power (and maybe another damping factor) to get the good quality bass I need :)

Franz
 
Thanks - sounds like it would be much lower sensitivity than my subs.

I'm curious, how does the amp sound when you push it hard into the sub?

I looked at the TAS5704 datasheet and at 18V power supply THD+N is already 10% at 20.6W (it doesn't show for 24V, I wonder why?)
 
I looked at the TAS5704 datasheet and at 18V power supply THD+N is already 10% at 20.6W

Yes, I know.

The TAS5704 is a fine device, but not really high end. I was expecting this, reading the datasheet.

It does not have the class of some T-amps.

The same is true for the analogue inputs and outputs of the MiniDSP. The converters in the DSP chip are not the best ones.

But, this does not make the MiniDSP solution uninteresting, it is part of the concept.

It is a very flexible base for own projects, even in the high end area, I am sure.

A path to very good solutions is:

- SPDIF in (Rev. B board of the MiniDIGI with transformers)
- I2S out to own DAC's (for example two gigawork dac)

For people who want to avoid the complexity of I2S connections, just use a second MiniDIGI board and you have two SPDIF outputs to own DAC's.

Franz

P.S.
I forgot in postings before: I used the LM3886 also in bridged mode, two channels. So it is a completely different output power than two channels bridged from the TAS5704
 
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Actually, I am very satisfied with the miniDSP.

Yesterday I downloaded the latest plugin version and EVERYthing is working fine now. Also the delay using the volume control is now within an acceptable range.

It seems to me like the soundstage is enlarged as it seemed to be a little bit limited by the version/volume control connection I used at the beginning.

Here you can look at my jumper settings I used to get a fine 2.1 system (using PEQ 2.1 plugin):

MiniDSP

An externally hosted image should be here but it was not working when we last tested it.


MiniDIGI

An externally hosted image should be here but it was not working when we last tested it.


MiniAMP

An externally hosted image should be here but it was not working when we last tested it.


Franz
 
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I have just received an email from MiniDSP, that this config is wrong. They have an updated manual now, with the right connections. I2S jumper have to be changed, so speaker output is completely different. They claim this is just a wrong 4 channel implementation. Hope you can use the info. In 2.1 config ch. the I2S ch 1&2 should now go to MiniAMP ch 3&4 and vice versa. The BTL output is now on 3/4 and SE on 1/2.
 
Hello

Wrong, as long you used the same settings as I did.

I WAS using brigded mode for the sub, by using the "stereo" sub setting in the plugin and by inverting one of the sub channels, also by plugin.

Otherwise there would not have been any sound on the sub connections.

As I dont use the MiniAMP module any longer, I have a different configuration today with my own DAC and amplifiers.

Now, it is me wishing you write all your findings in "your" thread, please!

Thanks
Franz
 
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