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Beau 22nd April 2013 01:25 AM

Mini dsp 2x4 output buffer
I have a Minidsp 2x4 (V1.5) that I want to use in my system.

Configuration is


Preamp/source selection Vol control

PGA2311 LCD Volume Remote Control Gold RCA Jeff Rowland | eBay


Ucd400 amplifiers

Problem is the input signal to the amp is too low. I need at least 2v input, my minidsp only outputs .9v and its just too quiet.

I was thinking of putting in a line driver after the minidsp, like this,

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Anyone have any suggestions?

Beau 23rd April 2013 01:31 AM

Found this, think it'll work?

Unbalanced TO Balanced Stereo Preamplifier FOR BTL | eBay

paulb 23rd April 2013 01:55 AM


Originally Posted by Beau (

No, I don't think so. This is probably set to a gain of +/- 1 (it has differential outputs). You want some gain.
The one you posted earlier should work.
It says it has a gain of 6.

Davey 23rd April 2013 02:37 PM

I would try the second board. It looks like 1k resistors in a standard configuration, so it should yield a 6db increase in output level on your UcD amp just from the unbal/bal conversion. Even if it doesn't, it's much easier to work on (with larger components) so you could modify it if necessary.



Beau 26th April 2013 05:05 AM

Thanks Dave,

Had a hard time getting a straight answer from the vendor.
Do you think there is any reason why it wouldnt work? He doesnt seem to understand that I want to use it as a line driver.

jgray 26th April 2013 10:27 AM

On my minidsp 2x4, I was able to change the internal jumper from .9 vrms to 2 vrms and avoid adding another device to get the required output. If yours has this ability, it could simplify things for you.

Davey 26th April 2013 03:52 PM

I assumed the jumper was already in the 0.9v position. Maybe not?

The miniDSP is nearly unity gain when in this configuration, so you shouldn't notice a volume difference whether it's in the circuit or out.....depending upon how you program it.

It also depends upon the power amp used and it's voltage gain and required voltage input for rated power.



Beau 27th April 2013 01:14 AM

Amp is ucd400, needs 2vrms to make full power, hence the search for a booster.
As it is the max out put on the minidsp limits the output of my amp to around 80wrms vs the 400 it is capable of.

Davey 27th April 2013 01:33 AM

The miniDSP 2x4 balanced version would be perfect for that application. I assume you purchased your 2x4 miniDSP before the balanced output version was available?

Anyways, the unbalanced/balanced converter should do the job and increase your effective power amplifier gain to 32db. If you need more voltage you can always change a couple of resistors to increase it.



Beau 28th April 2013 03:00 AM

No, second hand so no choice and no idea at the time.
I think I may have stumbled on an answer, change formst to
Input-minidsp-pga2311 pre/volume-ucd400

I think the vol control puts out 2v, no response from the manufacturer
Is there an easy way to test?

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