miniDSP kits, our answers to your technical questions

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anybody know how much is the ouput impedance of the balanced 2x8 kit?
is it 560ohm like the single ended?

 

[Davey]

anybody know how much is the ouput impedance of the balanced 2x8 kit?
is it 560ohm like the single ended?

Yes. 560 ohms per side.

Dave.

 

[back]

thanks

 

[wyan]

Newbie to DSP. I am thinking to try out a Minidsp blance 2*4 kit for my open baffle preject. A few quick questions:

1) There is an optional volumn control pot. Is the volumn control on the digital or analog domain?

2) I might need bass boost at lower octaves. What is the maximun boost at a certain frequency (6db? 12db? etc)?

3) I might need some extra output voltage. What are the simple class A gain stages availabe? Any recommendations?

Thanks a lot.

W.YAN

 

[OllBoll]

Newbie to DSP. I am thinking to try out a Minidsp blance 2*4 kit for my open baffle preject. A few quick questions:

1) There is an optional volumn control pot. Is the volumn control on the digital or analog domain?

2) I might need bass boost at lower octaves. What is the maximun boost at a certain frequency (6db? 12db? etc)?

3) I might need some extra output voltage. What are the simple class A gain stages availabe? Any recommendations?

Thanks a lot.

W.YAN

1. Digital of course, the analogue volume pot just controls the amount.

2. In DSP you don't really boost anything, rather you reduce the volume elsewhere. The cost is that the total headroom on other frequencies might be lowered, so you need to make sure that you still have enough gain to get your target SPL. Speakers are usually more efficient on higher frequencies so this is rarely a problem though. So in short you can relatively boost however much you want as long as you still have enough voltage gain =)


3. Don't, just get the 2x8 which has higher output capability =) And if you need even more then try to get a balanced woofer amp so you can use the even more powerful balanced outputs.

 

[wyan]

1. Digital of course, the analogue volume pot just controls the amount.

2. In DSP you don't really boost anything, rather you reduce the volume elsewhere. The cost is that the total headroom on other frequencies might be lowered, so you need to make sure that you still have enough gain to get your target SPL. Speakers are usually more efficient on higher frequencies so this is rarely a problem though. So in short you can relatively boost however much you want as long as you still have enough voltage gain =)


3. Don't, just get the 2x8 which has higher output capability =) And if you need even more then try to get a balanced woofer amp so you can use the even more powerful balanced outputs.

Thanks. The problem is that now I only go with unblanced (the source is unblanced).

 

[OllBoll]

Thanks. The problem is that now I only go with unblanced (the source is unblanced).

Personally I'd just discard the source and just get digital input for the miniDSP board. Then you won't have that problem anymore and it will perform better as you have to do 2 conversions less (digital to analogue to digital to analogue again becomes just digital to analogue.

You wouldn't have to worry about input gain and over driving the analogue inputs either which is nice.

 

[DrDyna]

Here's a question that might have been answered already, but can anyone tell me for sure what the limit is for running 24/96? I've seen some reviews / posts that say things like "can run at 24/96 with fewer channels" and I'm curious to know, if I use a 10x10 HD for 3x 2 way xo, will I be at 24/96?

Edit: Or is it completely dependent on the plugin? I'm starting to think I can't get 24/96 if I need more than the 2 analog inputs that the 4x10 plugin offers.

 

[Davey]

Yeah, it's dependent on the plugin. The miniDSP 10x10Hd plugin runs at 48khz and the 4x10Hd plugin runs at 96khz.

So yes, if you need more than two analog input channels and switch to the 10x10 plugin, you'll be limited to a 48khz sampling rate within.

Dave.

 

[DrDyna]

Yeah, it's dependent on the plugin. The miniDSP 10x10Hd plugin runs at 48khz and the 4x10Hd plugin runs at 96khz.

So yes, if you need more than two analog input channels and switch to the 10x10 plugin, you'll be limited to a 48khz sampling rate within.

Dave.

Thanks for confirming my suspicions Not a dealbreaker, I was just curious after I read that review.

I'm actually really damn excited for this 10x10 to get here.

Oh, one more question if you have experience with this unit, do the 4 preset configs change pretty fast from a remote, or is there a loading delay?

 

[tb303]

Oh, one more question if you have experience with this unit, do the 4 preset configs change pretty fast from a remote, or is there a loading delay?

I can only speak for the 4x10HD but I am sure it's the same with the 10x10.
yes, unfortunately there's a delay when switching presets. about 2 or 3 seconds.

And be careful with the unit. While it delivers great sound quality for the money, it has its pitfalls and you really have to know what you're doing.
- noise with improper gainstaging: run the unit's inputs and ouptuts as hot as possible and do coarse gain adjustments with passive pads
- MASSIVE power off thump/pop that can kill speakers: miniDSP says it's fixed on the new models, they offer a DIY hardware fix for rev1.3 models, which I did, but it's still there, but at least not as insanely loud as before
- filters in the region below ~20Hz don't always behave like shown
- no stability check with custom biquads: if you enter wrong, instable biquads that will output fullscale DC or fullscale oscilations, the miniDSP will output them with no mercy, possibly ruining your equipment connected to it.

 

[DrDyna]

Sounds scary. Maybe I should plug it into a UPS. I don't plan on turning it off, unless the power fails suddenly, I don't worry too much about thumps.

Now the biquad sanity check thing worries me a bit, so hopefully REW never erroneously generates biquads with garbage in them, that's pretty much the only thing I ever use biquads for, anyway.

My only adjustment below 20hz will be an HPF at 14hz, which should be easy enough to verify.

 

[Davey]

Any good program/spreadsheet that generates biquads performs a stability check. I think tb303 is referring to an event in which you paste them incorrectly, or get the syntax wrong, or fat-finger a digit in the wrong spot, or similar. So, you could get into trouble that way. However, the miniDSP graphic screen would be a visual indication that something is screwed up.

The thumping thing is problematic, but not that unusual with gear that has fairly large electrolytics as blocking capacitors on the outputs.

That said, there are a number of valid idiosyncrasies with the miniDSP gear. You have to be aware.

Cheers

Dave.

 

[tb303]

My only adjustment below 20hz will be an HPF at 14hz, which should be easy enough to verify.

This is something you should definitely verify with a REW loopback measurement.

I think tb303 is referring to an event in which you paste them incorrectly, or get the syntax wrong, or fat-finger a digit in the wrong spot, or similar. However, the miniDSP graphic screen would be a visual indication that something is screwed up..

Exactly what I mean.
However if you accidentally enter a full scale oscillator biquad, the graphic indication won't help much because it'll already be too late.
It's best to always turn off your amps when experimenting with biquads.

Of course these are worst case scenarios, but every miniDSP user should be aware of it.

 

[DrDyna]

Well, I have the 10x10 up and running happily. I do have one question though, for anyone with experience...what's the insertion loss, exactly? I've been rebuilding my surround channels, which don't run through the dsp, but rather are standard speaker level crossovers connected to the AVR. I noticed yesterday after plugging in a surround channel to fuss with placement, that the surround channels are way, way higher in level, while all the AVR level controls are at +/-0. I haven't mic'd it, but I'd guess somewhere around 6 to 8 db.

I haven't changed any jumper settings inside the 10x10, but is it normal for the output to be quite a bit lower than the input? I verified all gain settings and even enabled the volume control via front knob for a minute to make sure that it's at -0 as well.

Is it normal that my LCR going through the 10x10 requires +8 trim on the AVR?

Before you ask, all the drivers are of approximately the same sensitivity, pro 10" woofers and 10" waveguide/compression tweeters.

 

[Davey]

There's a wide variety of gain structure combinations depending upon the settings of the input jumpers, the output DIP switches, and the unbalanced/balanced interface hookup you utilize.

The DSP portion itself does not have any insertion loss or gain.....unless programmed to do so.

Dave.

 

[DrDyna]

The DSP portion itself does not have any insertion loss or gain.....unless programmed to do so.

Dave.

That's what I thought, with the jumpers in default positions, it should be 1v in = 1v out...so, something's wrong then. I even reset it to defaults and flashed the firmware that was included this morning, but no effect.

I guess I'll pop the top off here in a little bit and make sure the jumpers / dip switches aren't accidentally in the wrong place.

 

[Davey]

You would think that's the case but, no, 1 volt in 1 volt out is not the default position. So I don't think there's anything wrong with your unit.

They changed the default position of the internal DIP switches somewhere along the way and confused the issue. And it doesn't help that the miniDSP datasheet lists the wrong values for maximum output voltage. It should be 1.3VRMS and 2.5VRMS for the unbalanced outputs.

I'm sure your unit is working fine.

Cheers,

Dave.

 

[DrDyna]

You would think that's the case but, no, 1 volt in 1 volt out is not the default position. So I don't think there's anything wrong with your unit.

They changed the default position of the internal DIP switches somewhere along the way and confused the issue. And it doesn't help that the miniDSP datasheet lists the wrong values for maximum output voltage. It should be 1.3VRMS and 2.5VRMS for the unbalanced outputs.

I'm sure your unit is working fine.

Cheers,

Dave.

Aha, ok. *wipes brow* I was really hoping this wasn't atypical.

I guess the easiest solution is just to go ahead and lop the xlr plugs off these xlr - rca cables I ordered and land them in the phoenix block and start using the balanced outs for a little more signal.

 

[DrDyna]

Oh, one last question if I may...do you think there would be any problems having outputs 1-6 running balanced -> unbalanced with a bridge wire at the same time as outputs 7 and 8 running real balanced to an amp with xlr inputs?