Electronically unbalanced reamp box

[tombaker]

Hello,
I'm considering whether theoretically a reamp circuit could be made electronically rather than transformer-based.

I'm aware of the inherent downsides in trying to match impedance to change a balanced signal to an unbalanced electronically. But would the unbalancing and impedance conversion that a reamp box achieves be possible with an opamp?

Using the 'Typical Balanced Input' on the Bill Whitlock paper as an example:
http://www.jhbrandt.net/wp-content/uploads/2014/11/Interconnection_of_Balanced_and-Unbalanced-Equipment.pdf

Thanks in advance

[karbomusic]

The thing that is going to bite you is you need the isolation or it will find a ground loop/noise somewhere  (especially if this is connecting to a DAW). Ask me how I know that.

[ashcat_lt]

In fact that (^^^) is the only good reason to use anything but straight wire.

[tombaker]

Righto, noted.

Would implementing GND Lift on the balanaced side rectify this, as in some active transformerless DI designs?

[PRR]

The balanced link is extra good at rejecting ground loop buzz.

The opamp will work in about any sane situation. (I once worked with many Volts of ground difference between stage and booth, and transformers were mandatory.)

The *prime* trick is to get your mixer and your guitar amp on the SAME power outlet. This minimizes the ground loop.

That done, 90% of the time you can take an unbalanced feed from the mixer (the old TASCAMs were perfect for this) and adapt it to the g-amp. If that buzzes, you need the bal-un, opamp or transformer.

There is a $13 stereo transformer sold for car-audio which is more than good enough for this purpose. Use one side, chop the leads, adapt the plugs.

[tombaker]

Thanks for the tip.

[bool]

A "electronic" circuit isn't going to do the so-called galvanic isolation - which is the prime reason to use a transformer.

See if you can do with a small "couple EUR" 220V/24V mains trafo (primary: input; secondary: ouput), with a "impedance" pot added to output (a 50k Lin would do good imho).

This should be 10EUR max with a (plastic) box and jacks.

[karbomusic]

Quote from: PRR on Yesterday at 05:50:28 PM<blockquote>
The *prime* trick is to get your mixer and your guitar amp on the SAME power outlet. This minimizes the ground loop.

This seems much less workable when a DAW is involved - or better said noise free. The only tried and true method I've found is true isolation.