Balancer and De-Balancer on a TRS Jack to upgrade unsymmetrical gear

[Janus Audio]

Hi everybody,

I made SMD boards to balance inputs and outputs of some of my outboard gear, because I often hat hum problems with some devices. The boards are just some line receiver and line driver circuits based on LM4562s and can be fed from internal power supplies of the modded unit (as long it is a true bi-polar power supply). I tested them with up to 20dBu (which is all my DAC can do) and got THD less then 0.0012%

So far I upgraded my Quadraverb, Lexicon, LPX-1 and dbx 163A

Let me know, what you think!

Cheers, Sebastian

 

[TwentyTrees]

Great stuff, that's a very neat and compact solution to the problem. Nicely done.

 

[thomasdf]

Very clever design and neat build ! Bravo !

 

[Janus Audio]

Thank you!
I will test them with syngthesizers next. I sometimes get hum with some synths when they are connected via USB-MIDI

 

[Janus Audio]

Modding the Alesis Microverb II with symmetrical inputs and outputs

Checking the PSU where we can tap into the power rails:


Removing the old TS jacks:


Connect the sub-boards to the PSU V+ and V- taps and to the tip and sleeve solder pads of each TS jack:


Put the cover back in place:

 

[fazer]

Love it nice job.

You use to be able to buy these types of circuit kits from SparkFun for cheap. I wanted to make a hifi amp have a balanced input to work correctly with a balanced monitor controller and finally went to order the complete kits and they had discontinued them. Bummer.

 

[Janus Audio]

Love it nice job.

You use to be able to buy these types of circuit kits from SparkFun for cheap. I wanted to make a hifi amp have a balanced input to work correctly with a balanced monitor controller and finally went to order the complete kits and they had discontinued them. Bummer.

Thanks you!

I didn't know SparkFun yet - looks interesting! I don't see anything similar there though.
I will probably also sell the boards, if I manage to get a listing in the white board section.

 

[JohnRoberts]

these are called "bump boxes" and were popular last century back during the height of the -10 dBV bedroom recording gear boom, to step up/down signals between -10dBV unbal gear and balanced +4 dBu gear.

JR

 

[k brown]

Maybe I've just been insanely lucky, but in all my 40+ years mucking about with audio, I've not once encountered noise or interference from using unbalanced connections between line level gear.

 

[JohnRoberts]

Maybe I've just been insanely lucky, but all my 40+ years mucking about with audio, I've not once encountered noise or interference from using unbalanced connections between line level gear.

As you shouldn't using properly designed gear.

JR

 

[k brown]

As you shouldn't using properly designed gear.

JR

...and properly-made cables.

 

[fazer]

As you shouldn't using properly designed gear.

The controller is a presonus cs. It’s a passive design balance in out. It’s not noisy it’s just that it wants a full balanced connection to attenuate and work correctly. I build a balanced input using the circuit users in a genelec 1031 front end on a vector card and powered it off my Api power supply. It makes the controller work correctly. The Sparkfun kit was cool because the card set on the connector and mounted. Which would be great for the unbalanced amp mount in the chassis that powers my NS10 and aura tones. The mains are 1031’s. It works great because there are controls to attenuate tha ABC speaker outs to match output levels. They are pots that set across the hi lo balance lines. Everything work including the mono switches and dim with relays all passive. Everything turns to shxt when you connect unbalanced.