[Tyson]

[edit] I went ahead and made this a more general thread on problems w/the miniDSP 2x8.  I'm having problems with hiss and hum coming from my speakers when I hook it up at this point.  Also, all my inputs are LOUD when I put a signal on them, is there a way to reduce the gain structure of the miniDSP 2x8? [/edit]

Hi all, I just got in my miniDSP 2x8 today and I'm looking to get things hooked up.  My main question is regarding the power supply.  The miniDSP specifies 12V and 1.5a, and I have a linear power supply that is 12V and 3.4a - will this blow up the miniDSP?  Or will the miniDSP just pull whatever it needs and any extra headroom just sits around, idle?  Mainly I just don't want to blow up my board....

Here's the power supply I have:  http://www.alliedelec.com/search/productdetail.aspx?SKU=2180316

[JohnR]

The current rating is the maximum that the PSU will supply (before it shuts down/overheats). It won't deliver any more than the attached device (miniDSP in this case) "asks" for.

So you're good

Do double-check the polarity of the wiring before switching on. As a precaution, check the voltage before connecting as well - I'm always hyper-cautious the first time. Chances that there is something wrong with the supply are minimal, but it only takes a few seconds to check it.

[Tyson]

Kewl.  So, if I'm reading the schematic correctly, the miniDigi board (which came attached) is drawing it's power from the 2x8 board.  So, theoretically, I should be able to just hook up my power supply and then start making my audio connections via the RCA jacks for both analog and digital, along with the mini-USB input to synch up everything and start the programming from my computer, is that right?  Or am I missing anything important?

[JohnR]

Yep. I'd suggest connecting just the power and USB to start with and setting up the configuration (input, output, routing), before doing the rest of the connections. I think it just makes it easier that way and ensures that you know what outputs will be used for what.

[JohnR]

Oh, in fact, you can configure the plugin before you even connect the miniDSP. (Save to a file as a precaution though.)

[Tyson]

Got everything set up, all the cables plugged in, turn on my amps and..... hum and hiss from both speakers   Even if I unplug the analog inputs and the digital inputs and only leave the analog outputs plugged in, still hum and hiss   Hell, even if I unplug the power from the miniDSP there's still hum and hiss (although the hiss is quieter, but it's still audible from the listening spot).  Grrr. 

[JohnR]

Um... what happens if you disconnect the amp inputs?

[Tyson]

They hiss, unless I short them.

[Tyson]

Any suggestions on how to reduce the gain structure of the 2x8?  I checked the manual and there's no info on how to do it.  I did see something on the mini-DSP forum, but they just say it's possible, and not how (exactly) to do it.  I should be able to drop the input from 1.8 to 0.9 but I'll be darned if I can see how....

[JohnR]

There's a thread on their forum but I can't match up the "six jumpers" with my board, as I can only find four...

The documentation leaves something to be desired in some areas.

Are you using a preamp in front of the board?

On the output side, I match up the gains with attenuators on the amp inputs. Short of a full article but I put a brief outline in the "Gain adjustments" section of this article. (That was with the 2x4 boards but I'm still doing it the same way.)

[Tyson]

Yes, I have a thread on the miniDSP forum, hopefully they answer more clearly how to lower the input.  I have a tube preamp I'm using in front of the 2x8 and it's got low level hum and noise, of course, but it's amplified SUPER LOUD by the 2x8 with it's 1,8v input.  If I can get than down to .9v it'll go a long way to fixing it.

I fixed the tweeter hiss issue and the overall hum issue by using an Isomax transformer box between the miniDSP and my tweeter amp.  I had to do the same thing with the DCX previously, I was just hoping I could get away from using it w/the miniDSP....

Hey John, one other question if you don't mind - I'm trying to hook up an analog volume pot to the 2x8 board, and the manual is again less than great, can you tell me which jumper it goes to?  From the manual it "looks" like the one labeled "J16" on my board, but when I drop it in there, nothing happens, even after I enable it in the software. 

[JohnR]

Sure, no worries   It's marked as J13 on my board:

[Tyson]

Hmm, could you take a wider shot so I can see the whole board?  Mine looks like it might be laid out a bit different, and a wider shot can show me for sure.

[JohnR]

Connector lower middle:

[Tyson]

Yep, my board is a bit different.  I tried it on the J13 jack and no love   Ah well, hopefully the miniDSP guys will answer my thread on their forum soon...

[Tyson]

Ah, I had forgotten to enable the master volume control in the software this most recent attempt.  I enabled it and J13 is the magic number!  I can successfully control the volume of the miniDSP in the analog realm