Minidsp Flex Review (Audio DSP)

[Genstruktur]

Hi,

I bought a Mindsp flex analog unbalanced a while ago in an attempt to replace an analog PEQ that i have and was happy with. But I thought that Flex would be easier to set up precisely.

I have connected Flex between receiver pre out and power amplifier. I understand that it may not be the primary area of use since most people use Flex as a preamp and connect various sources to it. I have still read some who use it this way and the manual specifies that you can connect it to subwoofer pre out for example.

I have installed the latest software on Flex. At first I just thought to see how it "sounded" without any filters or anything activated in Flex. So I connected it via rca from the receiver's pre out and into power amplifier. I had Flex main volume at 0 and Flex in/out at 0 and analog source in Flex at 0.

Now to the problem. At lower volumes it sounded okay but not that great and certainly not like without Flex. When I started to raise the volume at my receiver, to what i play as the loudest, it started to distort. And in the Flex device console i see that i am close to 0 dBFS on the input/output.

I tried many different variations but I can't get it to sound good with Flex in the signal path. At least if I want to keep Unity gain through it. I tried raising/lowering the analog source in Flex, raising/lowering the input/output in Flex and raising/lowering the receiver main volume to try to keep Unity gain but the result was the same. It sounds okay, not good, at lower volumes and it distorts at higher volumes.

I have a Rotel RB 1582mkII with input sensitivity 1.9V, so I think Flex should be able to drive it to max output with its 2.0V max for the outputs.

I will try again today with Flex but as it is now it is unfortunately not possible to have Flex in the signal path. Is there anybody who uses Flex like my setup and got it to work? Any suggestions?

 

[antcollinet]

Hi,

I bought a Mindsp flex analog unbalanced a while ago in an attempt to replace an analog PEQ that i have and was happy with. But I thought that Flex would be easier to set up precisely.

I have connected Flex between receiver pre out and power amplifier. I understand that it may not be the primary area of use since most people use Flex as a preamp and connect various sources to it. I have still read some who use it this way and the manual specifies that you can connect it to subwoofer pre out for example.

I have installed the latest software on Flex. At first I just thought to see how it "sounded" without any filters or anything activated in Flex. So I connected it via rca from the receiver's pre out and into power amplifier. I had Flex main volume at 0 and Flex in/out at 0 and analog source in Flex at 0.

Now to the problem. At lower volumes it sounded okay but not that great and certainly not like without Flex. When I started to raise the volume at my receiver, to what i play as the loudest, it started to distort. And in the Flex device console i see that i am close to 0 dBFS on the input/output.

I tried many different variations but I can't get it to sound good with Flex in the signal path. At least if I want to keep Unity gain through it. I tried raising/lowering the analog source in Flex, raising/lowering the input/output in Flex and raising/lowering the receiver main volume to try to keep Unity gain but the result was the same. It sounds okay, not good, at lower volumes and it distorts at higher volumes.

I have a Rotel RB 1582mkII with input sensitivity 1.9V, so I think Flex should be able to drive it to max output with its 2.0V max for the outputs.

I will try again today with Flex but as it is now it is unfortunately not possible to have Flex in the signal path. Is there anybody who uses Flex like my setup and got it to work? Any suggestions?

It should be no different using it like you are (pre out to main in) than any other analogue path.

The only reason I can think of for the distortion (assuming neither your pre out nor MiniDSP are faulty) is if your amp outputs a higher voltage than the rated 2V input of the flex. Are you able to measure the pre out with a multimeter and a test signal?

Alternatively, test with a digital input to the flex direct to the main in of your amp (make sure the volume on the flex is turned down to start with). This will tell you if the problem is on the "flex to main in" connection, or "Pre-out to Flex”.


PS - what is your amp?

 

[Genstruktur]

It should be no different using it like you are (pre out to main in) than any other analogue path.

The only reason I can think of for the distortion (assuming neither your pre out nor MiniDSP are faulty) is if your amp outputs a higher voltage than the rated 2V input of the flex. Are you able to measure the pre out with a multimeter and a test signal?

Alternatively, test with a digital input to the flex direct to the main in of your amp (make sure the volume on the flex is turned down to start with). This will tell you if the problem is on the "flex to main in" connection, or "Pre-out to Flex”.

Thank you for answering. Well i have also thought about what the pre out is outputing in Volt. But then again it wold be the same problem with out the Flex in the signal path? Since my Rotel RB 1582mkII is rated 1.9V input sensitivity(lower than Flex output 2V)? I have mesured it and got this, posted it on another forum and it seemed strange people said. But i really do not have the technical skills to interpret this.

-3dB receiver = 01.4V
0dB receiver = 02.1
+5dB receiver= 03.6
+6dB receievr= 03.5
+7db receiver= 03.4
+8dB receiver=03.2
+10dB recievrer = 02.8
+18 dB receiver(max) = 01.3V

I listen to both movies and music at -3db on a regular basis with my receiver and without Flex.

I think i will also try to hook up my cd-player directly to Flex and use it as a preamp without my receiver to see if it helps. The problem with this is i do not wish to use it this way since i have several devices i wish to route through receiver and Flex. Nvidia Shield, Xbox, CD and streaming through receiver.

 

[antcollinet]

-3dB receiver = 01.4V
0dB receiver = 02.1
+5dB receiver= 03.6
+6dB receievr= 03.5
+7db receiver= 03.4
+8dB receiver=03.2
+10dB recievrer = 02.8
+18 dB receiver(max) = 01.3V

That does look strange. What was your input signal to the reciever for those measurments.

+6dB should result in a doubling of voltage. Or +3dB = "mulitply by square root of two"

This is working from -3dB to 0dB, but above that it goes wrong. If there is no limiting then the 2.1V should go to 4.2V at +6dB.

So the pre-out seems to be clipping at about 2V rms - the increase from there, probably being from the sine wave (if that is the test signal. you were using) gradually being clipped to something like a square wave - plus possibly characteristics of your volt meter if not true RMS.

 

[antcollinet]

The problem with this is i do not wish to use it this way since i have several devices i wish to route through receiver and Flex. Nvidia Shield, Xbox, CD and streaming through receiver.

Understood. This is how I'd use it to if I had an amp with pre-out/main in. Still useful as a test though to work out what is going on.

 

[Genstruktur]

That does look strange. What was your input signal to the reciever for those measurments.

+6dB should result in a doubling of voltage. Or +3dB = "mulitply by square root of two"

This is working from -3dB to 0dB, but above that it goes wrong. If there is no limiting then the 2.1V should go to 4.2V at +6dB.

So the pre-out seems to be clipping at about 2V rms - the increase from there, probably being from the sine wave (if that is the test signal. you were using) gradually being clipped to something like a square wave - plus possibly characteristics of your volt meter if not true RMS.

It was 50 Hz sine wave. Fully equipped to 0dBFS.

Its a Denon AVR-X3800H.

 

[Genstruktur]

I have solved it.

Theres one thing I left out of my description of my system. Partly because i lack the knowledge to explain exactly how it works, especially in English.

I use Ino Audio speakers (Swedish). Ino audio pi60 which is full range speaker, together with Ino Audio bs60 which is bass support. They work acoustically in parallel – together – with the main speakers within a very large frequency range (20 – 500 Hz).

They are both driven by Rotel RB 1582mkII. Between the receiver and the amplifier you need an Ino Audio Bcx(tone control), which must be impedance matched to the amplifier for the filter effect of the Bcx to be correct.

Earlier in the thread i have connected the Mindsp Flex after the receiver but before Bcx. I usually do that even with my analog peq, and it works.

Now i connected the Minidsp Flex between Rotel RB 1582mkII and bcx instead (impedance matched bxc to Minidsp Flex, instead of Rotel RB 1582mkII as earlier) Now it sounds good!

 

[antcollinet]

I have solved it.

Theres one thing I left out of my description of my system. Partly because i lack the knowledge to explain exactly how it works, especially in English.

I use Ino Audio speakers (Swedish). Ino audio pi60 which is full range speaker, together with Ino Audio bs60 which is bass support. They work acoustically in parallel – together – with the main speakers within a very large frequency range (20 – 500 Hz).

They are both driven by Rotel RB 1582mkII. Between the receiver and the amplifier you need an Ino Audio Bcx(tone control), which must be impedance matched to the amplifier for the filter effect of the Bcx to be correct.

Earlier in the thread i have connected the Mindsp Flex after the receiver but before Bcx. I usually do that even with my analog peq, and it works.

Now i connected the Minidsp Flex between Rotel RB 1582mkII and bcx instead (impedance matched bxc to Minidsp Flex, instead of Rotel RB 1582mkII as earlier) Now it sounds good!

Good news. Glad it's sorted.

Thanks for letting us know.

 

[Genstruktur]

Good news. Glad it's sorted.

Thanks for letting us know.

Yeah.

I think you have to do it. I personally dislike it when you look for a solution to a problem and the person never post in the thread regarding if it was solved or not.

 

[SoySalsaPicante]

With all that said/sorted...wouldn't the digital input still yield better results? Avoid an entire DAC & ADC double conversion (granted I'm assuming source is digital like CD or streaming and not analog like vinyl or tape).

 

[antcollinet]

With all that said/sorted...wouldn't the digital input still yield better results? Avoid an entire DAC & ADC double conversion (granted I'm assuming source is digital like CD or streaming and not analog like vinyl or tape).

He has a number of different sources connected to the preamp that can't all be connected to the MiniDSP. In this case using the pre-out to mini DSP to power amp, is a perfectly workable solution.

The additional DA/AD step will be totally transparent.

 

[Genstruktur]

With all that said/sorted...wouldn't the digital input still yield better results? Avoid an entire DAC & ADC double conversion (granted I'm assuming source is digital like CD or streaming and not analog like vinyl or tape).

But how does it use it digitally with all the audio formats that need to be decoded in the receiver?

It feels a bit strange to write this but I actually think it sounds better with the Minidsp Flex in the chain than without it. Very strange.

 

[SoySalsaPicante]

He has a number of different sources connected to the preamp that can't all be connected to the MiniDSP. In this case using the pre-out to mini DSP to power amp, is a perfectly workable solution.

The additional DA/AD step will be totally transparent.

Ah yes, then that would explain feeding it post-preamp. Thanks.

 

[Genstruktur]

Regarding this:

It feels a bit strange to write this but I actually think it sounds better with the Minidsp Flex in the chain than without it. Very strange.

The difference was even more prominent with movies i think. Is it something with the Denons pre out clipping? Would i benefit from lowering my front speakers in the Denon set up menu and raising the analog input in Minidsp Flex with the same amount?

 

[deercreekaudio]

Gain structure 101 this is a good little primer on the topic

 

[Genstruktur]

Gain structure 101 this is a good little primer on the topic

Well i have seen this article and read it. Should the dBFS-meters in the Mindsp software console always be green for optimal Audio quality? When i have checked these have sometimes been at -5 and orange when playing especially music. They seemed a little bit lower with movies.

 

[brombo]

I have had no problems with the miniDSP Flex 8 or the Flex (balanced). I am using digital inputs (usb and toslink) for both from htpc's. With the Flex 8 I am using the usb input for my LX521.4 speakers. With the Flex I am using the toslink input for my JBL CBT 70J-1 main speakers and subwoofers. In both cases the Flex's are driving Buckeye Hypex Ncore amps. The Flex 8 uses rca to xlr adapter cables. The Flex uses TRS to xlr cables. I run the digital output at 100% volume and use the miniDSP's volume control to set the output volume of the speakers.

 

[deercreekaudio]

I have had no problems with the miniDSP Flex 8 or the Flex (balanced). I am using digital inputs (usb and toslink) for both from htpc's. With the Flex 8 I am using the usb input for my LX521.4 speakers. With the Flex I am using the toslink input for my JBL CBT 70J-1 main speakers and subwoofers. In both cases the Flex's are driving Buckeye Hypex Ncore amps. The Flex 8 uses rca to xlr adapter cables. The Flex uses TRS to xlr cables. I run the digital output at 100% volume and use the miniDSP's volume control to set the output volume of the speakers.

The RMS meters are just an approximate guide, we try to stay our of the red. If you are driving the miniDSP Flex into DSP or input clipping it results in a very nasty digital break up.

 

[brombo]

The digital sound output on the htpc (usb or toslink) is set at 100% using the htpc's volume control (0 dB). The htpc's volume control is not set for over amplification so the digital dynamic range of the miniDSP should not be exceeded (no indication of digital breakup). The volume control on the miniDSP Flex series is digital.

 

[Genstruktur]

I notice that the good thing about Mindsp Flex ease of setting it up exactly the way you want it, is also its curse compared to my analog peq . It's easy enough to end up in an endless loop of measuring, making filters and listening. I have to focus for a while now on listening to what filters actually sound better and not just different.