50asx2btl and MiniDSP plate amp project. Help needed

[AaronMat]

Hello all,
I'm trying to make a teeny travel subwoofer using an ICEpower 50asx2btl 170W amp module and an old miniDSP 2x4 (non HD).
I've run into trouble though.
The amp module has balanced inputs only and I had no way of knowing as the literature doesn't say anything about that. Also, the miniDSP can't provide enough signal to get any real output from the amp.
The DSP puts out 2v unbalanced and the requires 3.3v balanced.
The amp has an aux power supply putting out +/- 25v with a max 200ma, the dsp is already pulling around 150ma but only on the positive side of the supply.

I guess I need a very small and efficient preamp board, but I don't know the first thing about circuitry...I can solder though!
I'm sure I'm not providing enough info, so please ask questions.

 

[Sokel]

I don't know about older but icePower can work just fine pseudobalanced as well.
Mayde not to it's full potential but your needs don't seem to ask much (never heard of a travel sub before to be honest).

 

[TimoJ]

50asx2btl doesn't have real balanced inputs. It just needs one channel inverted for bridge operation. You can do that with your miniDSP.

 

[NTK]

Theoretically you can use 2 single ended (SE) output channels of your miniDSP 2x4 to create one differential output channel. Run one SE channel in the normal polarity, and run the second one in inverted polarity. The output of the first SE channel becomes the +ve side of the differential output, and the output of the second SE channel becomes the -ve side of the differential output. This will also give you the 6 dB gain (i.e. you'll get 4 V full scale output).

Source

 

[voodooless]

I use a cheap Chinese DRV134 board. I have no idea if it’s the real deal, but it works

Also note that the B&O amp has rather high input impedance and the MiniDSP doesn’t really like that. A buffer in between might be a good idea anyway. I power the DRV board via the AUX supply and another cheap bipolar regulator board.

 

[staticV3]

Also, the miniDSP can't provide enough signal to get any real output from the amp.
The DSP puts out 2v unbalanced and the requires 3.3v balanced.

(37/1.414)*10^(-27/20)≈1.17
->the BTL Mono version of the 50ASX2 requires 1.17Vrms at the input to reach the maximum rated output voltage.

 

[AaronMat]

I use a cheap Chinese DRV134 board. I have no idea if it’s the real deal, but it works

Also note that the B&O amp has rather high input impedance and the MiniDSP doesn’t really like that. A buffer in between might be a good idea anyway. I power the DRV board via the AUX supply and another cheap bipolar regulator board.

Are you saying that the DRV134 you're using acts as a buffer also? Mighty convenient if that's the case.

 

[voodooless]

Are you saying that the DRV134 you're using acts as a buffer also? Mighty convenient if that's the case.

Yes, it’s a buffer as well.

 

[AaronMat]

Thank you all for your responses, I learned a little something from everyone. I'll post the resolution as soon as I have it sorted out.