Minidsp with high efficiency speakers; noise?

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Hello,

Hard to say remotely what could be the reason and how we can help here but we're always happy to help.

- First off, for those of you who would indeed hear some noise floor, we'd need to understand your gain staging. Now telling us you have an amplifier, a source and some speakers model isn't going to help.. :) Gain staging is how your 3 elements (the Source, the miniDSP gain settings (digital + analog) and Amplifier volume) are set. You have some digital gain in this DSP and a lot of you may not realize that running the board with a very low signal (or digital gain turned down say for the tweets) and amps without a volume control at max may not be the best way to run your system. That's the key element in this story and something that Curryman also mentioned in his post. Once we know that, we can help. Otherwise, I hope that you realize that you have 4 potential locations (Source + Digital gain input + digital gain output + Master Digital gain (via pot) + Amp volume) where this can be tweaked. With each configuration being a DIY setup (i.e. I'm pretty sure that none of you have the same setup), We'd recommend that you investigate with these gain staging as a test. A google search for "Gain structure" (please take the time to actually do that google search.. ;-) is really worth it... Finally, taking some measurements with a PC can be a way to help too.. (not acoustic) .

- Now down to the online forum in Dutch. There are few translation words that seems not really clear what's meant but we're getting the gist. e.g. Did I misread that this person testing the board doesn't have the software? We don't have a neutrik tester over here, but do have some Audio Precision units (APx515 used for this test). We grabbed 2 units out of the stock for a test back then with a similar post (most likely from the gent testing) and here is the spectrum we're seeing (overlaid graphs for outputs). See below.
I'm maybe guessing that this is an analog to analog configuration in his test?

So obviously, we don't see readings of such high noise floor which is quite odd and making use wonder which version of the board is used(There are now 3 rev online by the way). Central part seems to be hacked off/soldered.. With an analog analyzer (hard to see out of band noise) and not knowing the setup, it's hard to know why such readings are here though. Maybe this gent could send us his board?

We're doing a new batch of Balanced boards so before doing so, we could investigate once again a full array of test to track down a potential noise issue. Adding some better line drivers on the outputs (e.g. That corp) for better CMRR could be a way.. It won't solve (and wouldn't on any Digital DSP system for that matter) incorrect gain structure though. That's a key design element which we don't have control over and end users would need to take care off.

Hoping this info helps.

DevTeam
 

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I can understand the tip of using a volume control after the dsp. That would damp the niose. However, for a 2.1 setup that is just not practical. I replaced the psu in hopes of improvement, but the results were identical. The dsp is a great little tool for testing, but I am thinking of changing the filter I have implemented to an analog alternative.
 
@ Leeuwarden,

The fact that you restore your miniDSP back to default won't solve the concept of gain structure. Did u get a chance to do a bit of reading on the topic by any chance? That's really valuable information when doing any audio chain. It's all about impedance, gain staging of the various elements of your system. All to the way to ProAudio and inside an full product (e.g. AVR with source + DSP + DAC + AMP in one box), you need to take care of the gain structure to optimize your SNR.

One thing to remember is that the balanced board outputs 4Vrms while the unbalanced board outputs 0.9Vrms at its max. So expecting that the 2 boards would behave the same on the same amp with the same gain setting would not be right. You'd obviously have to perform some gain control somewhere (in digital/analog)

Do u see what I mean?

Hoping this info helps

DevTeam
 
I see what you mean. But.... As also mentioned by SuperR my set-up does not provide the means to do a set up as you say. I have an expensive pre-amp, al lot of power amps and two nice speakers. There is no way I could implement a volume control after the MiniDSP as you say. It would mean I could just throw away my expensive pre amp.

I look at it this way. There is an balanced in and balanced out on your product. In my very simple mind that means I can make an active audio system by putting a MiniDSP between my pre-amp and power amps. I would expect this to work without uninvited noises as it happens now. On your website you mention the MiniDSP works wit line level input. In my opinion I'm feeding line level input from my pre amp so I did not expect noise coming from my set-up. I guess your website is not clear about the use of a volume regulator after the MiniDSP.

Solving the, also not mentioned on your website, turn on/off thump cost a lot of effort but I solved it. This noisething is coming from the balanced MiniDSP board. And obviously I'm not the only one being a bit dissapointed. After all, I bought 2 Balanced MiniDSP boards and the situation as it is now I might as well throw them in the trashcan. If it was mentioned on your website I had to solve a (very loud, very dangerous for at least tweeters) turn on/off thumb and it was mentioned I have to use the onboard volume option, I would probably not have bought it. Really funny thing is I bought 2 unbalanced versions at first and being satisfied (except for the turn on/off thumb) I decided to go balanced all the way and bought two balanced versions. Maybe MiniDSP offers a cheap solution but if its not working as an audio device should, it is still very expensive... Not to mention the import tax I had to pay...

Last thing about the turn on/off thump. I was given the advise to last turn on the power amps and turn them off before the rest. I guess my daughter and son (12-14 years) would forget this sequence sooner or later... not to mention my wife. A safety relay is unavoidable if you want to keep your speakers in one piece...

Having said all of this it would be nice if MinI DSP offers a solution.

Regards,

Jan
 
In my very simple mind that means I can make an active audio system by putting a MiniDSP between my pre-amp and power amps. I would expect this to work without uninvited noises as it happens now.
I know it's bit tricky. The succes of the minidsp is in it's price, period. Like the movie said, "something's gotta give". No expensive ADC's, no expensive DAC's and no circuitry for an output shutdown/delayed-on. That leads to noise and plops.
Thanks to the fact I use my power amplifier as a master in a master-slave powersocket, the minidsp/pre/cd shutdown "instantly" as soon as I shutdown the power amp. Therefore I have no thumps/plops.
Indeed if I had know my minidsp would be noisy, I would not have bought it. I would have made an analog x-over which suits my wishes.
But rather than complaining, I would rather have a solution to the issue. I assume I cannot replace the ADC or DAC. The psu is a very nice piece so I am out of idea's. Although my preamp is not as expensive as Leeuwarden's, I still want to use it as my volume control and source selection.
 
Understanding gain staging really is the key to your problem. If you have invested a bomb in commercial gear then pay one of your dealers to come out and set it up for you. They (or you) could use something like this

Amazon.com: Dayton Audio XATT20 In-Line XLR Attenuator Pad 15dB: Musical Instruments

as a fixed attenuator between the MiniDSP and your power amps. The MiniDSP should easily be able to meet your requirements and will sound much better, as well as quieter, when it is driven, and driving, at the correct levels.

blakkberd
 
DevTeam? I would really appreciate a solution to this problem....
Over the week end we typically try to relax.. :) However we do our best to answer all inquiries within 3-4working days as you've seen before though so thanks for your patience. :)

Ok, so I've read these comments and before going further, I'd like to ask something to make sure we are talking of the same issue we're trying to solve here. Could you please point me to the online articles you read about gain structure? It would be a great start to be able to point out the elements few of us are trying to explain here. Most of the content we read were from books, but a simple google search pointed some very good reference. Let's see which one you read and how you understood/how they explained the issue of optimizing SNR.

On a DSP (or actually any piece of an audio chain with a DAC/DAC), optimizing the gain structure between the different elements is very important (but I've said that many times already..:) Saying that the miniDSP can't work with a preamp isn't accurate I believe since there are a lot of us doing it already. I think that we need to acknowledge that each of you have a different setup (amps with a different input sensitivity, gain control before, after, various filtering in the DSP), quite a few are DIY setup, and while some time is spent doing some measurement, little time is spent looking at the gain structure from what we see typically. Adapting your gain structure to the DSP isn't some one button fix all. :)

I'm reading some of these between the lines on few things here... (i.e. Is the gent from Triple Audio the one with your board?). But basically, our general understanding from what you are describing is as follow:
1) You have a preamp at the input side, that's fine. Many of us have this and no issue.

2) You used to have a miniDSP unbalanced, so I'm guessing that level wize, your amp was fine with the output. Going to the balanced you're talking of a 4x gain. Has any change been done to the system? (e.g. padding as suggested by blacksheep). Or you're just attenuating all these in the digital domain (i.e. DAC/ADC running at their worst SNR)

These are just few of the questions you need to figure out basically when you put pieces together.. Now, as i"ve mentioned before (but not sure if it got lost in between), and as Blacksheep is mentioning, gain structure is to be done in any audio system. Just few people pay attention to it because in most cases, you don't have a chain (i.e. Preamp going to amp). Is it possible that the gain that you have out from a miniDSP balanced is just too high for your amp (i.e. you'd need to attenuate for an appropriate level)

3) With regard to the pop noise, it's the caps discharging and this issue has actually been solved on the latest batch as we've indeed listened to the request of the community. Both unbalanced and balanced shouldn't have the issue. There are few using some delay relay which might be an alternative.

Hoping this info helps

DevTeam
 
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@ Devteam:
regarding your point 3): interesting info about pop noise problem being solved in the latest batch. May I ask how this has been solved ;)
Maybe it's possible to fix (DIY) also for the older batches :scratch:

@Leeuwarden:
I can only repeat what has been said many times before (also by me ;)): have a look at your gain structure! If you can give us some more information about your preamp and poweramps, we will try to help you optimizing your gain structure. It's really the best to stop trying (try AND error :eek:) but to systematically analyze the levels in your chain and optimize all this.
 
In my previous life as an AV consultant (or "insultant" as we joke about it), I have seen plenty of very nice (and very expensive) systems that got out of whack. Most of the time, a messed up gain structure was to blame. :mad:

I wish I had a dollar for every system we inspected, supposedly "malfunctioning" and in need of replacement according to the local contractor, that ended up being "cured" by a simple gain structure alignment procedure. :rolleyes:

I feel for those having to endure the noise challenge at hand, but having gone through similar issues myself, I strongly second the manufacturer's recommendations so far. I am not saying that this is the answer, but a pretty good starting point. :up:

My first miniDSP was ordered today, so I can play along with other DIY fellows. :)
 
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