Passive Transformers Audio Splitter

[Strawtles]

Hi, I need to split a line signal, and I'd prefer a passive circuit (also considering I own some 600 ohm 1:1 trasnformers)
Do you think the below schematic is good?

 

[gyraf]

..you'll most probably want to have a single transformer core with several secondaries..

What levels you need to transfer will define the size of transformer you need

The LL1588 - https://www.lundahltransformers.com/wp-content/uploads/datasheets/1588.pdf - is a really decent transformer for this - you can use one of the windings as primary, take three isolated splits out of the other windings

/Jakob E.

 

[Strawtles]

Hello Jakob!
I have to split the outputs of a mixer and I have at home 6 Edcor XSM 600 transformers and 4 Lundahl LL1539, too
Do you think it works?

 

[gyraf]

I'd probably use the LL1539's as 2:2+1+1

but you need to try yourself

are you sure you need isolated splitting?

our SSL4000 had simple passive splitting, paralleled outs.. very rarely had any trouble with that

/Jakob E.

 

[JohnRoberts]

Be aware that paralleling transformers is similar to passive parallel inputs (mults) so will present a load 1/4 the value of just one.

JR

[more- it is possible to configure a transformer with constant load impedance by reducing the output winding voltages. -6dB per drop will increase the reflected load 4x so 4 in parallel equals 1x  previous nominal load. /more]

 

[Strawtles]

Jakob, I am not sure I need an isolated splitting, but in this way I have a complete separation beetwen the different outputs to prevent any future problem

 

[DerEber]

You could use any common 1:1+1 Transformer to get 3 outputs.
One without transformer and two of the 1:1+1

 

[abbey road d enfer]

Jakob, I am not sure I need an isolated splitting, but in this way I have a complete separation beetwen the different outputs to prevent any future problem

This is a very common misunderstanding. Separation is only galvanic, but if one of the outputs is shorted it reflects on the other windings and overloads the source.

 

[Strawtles]

Thank you and merry Christmas to all
I think I have to considerate an active splitting circuit
Someone has a schematic to suggest?

 

[Bo Deadly]

Inputs are almost always 10K. Only old designs like pultec stuff, some older 1176 or cinema engineering filters and such have 600 ohm inputs. If you don't have gear like that, then a simple LL1539 isolator / splitter would work fine.

But it might help if you described what problem you're trying to solve in more detail. Are you experiencing some noise? If not, using a patchbay "mult" or Y cable should work pretty well. Mixer outputs are probably at most 100 ohms and a really good mixer probably quite a bit lower depending on the output which is fine driving multiple loads. I have patchbay mults with 4 positions so 1 output drives up to 3 inputs. It's almost always fine but I do have some 600 ohm stuff that can act funky under certain circumstances.

 

[rackmonkey]

PRR would tell you to ditch the transformers and use a simple resistor network. I recall him telling me that a fistful of 10k resistors will get you there cheaper and without the (relatively speaking) tricky loss calculations. While inferior to a well designed active splitter, it may well be perfectly suitable in this case.

 

[Strawtles]

I need a circuit to split the stereo output from my mixer to different machines: active monitors, subwoofer, two separate headphone amplifiers (one in control room and another in recording room)

I fear that parallel outputs can create problems and I thought that the use of transformers was the best way to avoid it

In any case, I want to keep the mixer outputs free from noises and interferences that may be created connecting the other machines

 

[rackmonkey]

I need a circuit to split the stereo output from my mixer to different machines: active monitors, subwoofer, two separate headphone amplifiers (one in control room and another in recording room)

I fear that parallel outputs can create problems and I thought that the use of transformers was the best way to avoid it

In any case, I want to keep the mixer outputs free from noises and interferences that may be created connecting the other machines

In this situation then, I’d go with an active approach.

 

[Strawtles]

Something like this with OPA2134?

 

[abbey road d enfer]

Something like this with OPA2134?

No. This is a typical example of the "Tascam problem". You can't connect the outputs to an unbalanced input. You'd be better off with impedance-balanced outputs.

 

[Strawtles]

Yes, before the circuit I have to unbalance the signal from mixer.

 

[abbey road d enfer]

Yes, before the circuit I have to unbalance the signal from mixer.

I mean the splits cannot be connected to an unbalanced inputs.

 

[Strawtles]

I think it is better to have a fully balanced circuit, but I have found only circuits with unbalanced inputs.

I found the block diagram of a Sonifex splitter where the input signal is converted to unbalanced for returning balanced in the outputs