preenfm Forum
PreenFM => preenfm2 and preenfm3 => Topic started by: djencode on October 06, 2016, 05:04:27 PM
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Hi is there a way to mod this to convert the unbalanced outputs to balanced?
Currently since this is my only synth that is unbalanced it is also the one with the highest noise floor and most rf interference and I'd like to bring it on parity with my analog synths.
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Hi,
Majority of synth have unbalanced output because the difference is tiny with farly short cable.
But you have to use UNbalanced cable. Do you ?
Moding the preenfm won't be straightforward because kits are provided with mono audio jack.
There's lots of info on the web on how to turn unbalanced signal to balanced signal. JLMAudio use a "floating" balanced on the output of some of its preamps, which would be an easy passive mod.
See the bottom right of : http://www.jlmaudio.com/Baby%20Animal%20Mic%20Pre%20with%20JLM14%20with%20JLM99v%20or%20Hybrid%20on%2048v.pdf
If you use UNbalanced cable, not to long cable, and if your preenfm2 is noisy with RF interference, the problem may come from something else.
Xavier
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I think your main issue is the ground.
No synth provides a real ground lifted balanced signal. This requires a signal transformer. Active circuits can also be used to tame it.
So even if your other synths have a Balanced out, they defenetly will not have transformer isolated outputs. So its a electronically balanced, but this will not provide a proper signal isolation. The only thing it does, is if you run very long cables, 20m and more, it will reduce cable noise.
If you have 5m well shielded cable, then there is no difference in signal quality.
If you run very long wires, try it with a 1m cable and see if it still is noisy, if it is, you have an issue with something else and balanced output will not solve it.
A transformer based output might solve it, a DI box will help.
OT:
Its a very hot topic in sound studios, where they think that everything has to be balanced because otherwise the quality of the signal is reduced. But never people realy think about the way all the Hardware is manipulation the signal, they are all doing it in unbalanced way.
So you have a cable in - balanced/ audio manipulation - unbalanced/ cable out - balanced.
Only real benefit for doing it is transformer based isolation for the ground and +/- noise cancelation. But the Noise cancelation actually only works for the noise that is generated inside the cable. How real is that if you have a small studio, you have a cable that is producing noise? Go buy a new cable, it costs only 100 times less than the balancing circuit.
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edit: i switched to the balanced cables, and for some reason despite it being an unbalanced output it helped with the noise floor both on USB and DC