Creating a differential signal from a single-ended signal for bridged amps

[mikelm]

Have you tried using half of the primary instead of all of it ?

I prefer this option.

It means that my 'balanced in' is now psuedo balanced with the earth from the source connected to the centre of a resistive divider across the balanced o/p (and to the case of the TVC)

Using the 102 with a primary centre tap earth is not a good idea as the windings are not symetrical and in these circumstances I do find that treble is reduced.

But I prefer this half primary option even for unbalanced in.

mike

[analog_sa]

I prefer this option.

So do i. Btw i've only used it unbalanced.

[darkmoebius]

Originally posted by Peter Daniel
How would it be to combine transformer with an active line driver, like AD815 for instance (or discreet buffer)? I think there is even an example like that in application notes.

Which of these two looks better?

From AD815 datasheet :

Another means for creating a differential signal from a single ended signal is to use a transformer with a center-tapped secondary. The center tap of the transformer is grounded and the two secondary windings are connected to obtain opposite polarity signals to the two inputs of the AD815 amplifiers. The bias currents for the AD815 inputs are provided by the center tap ground connection through the transformer windings.

One advantage of using a transformer is its ability to provide isolation between circuit sections and to provide good commonmode rejection. The disadvantages are that transformers have no dc response and can sometimes be large, heavy, and expensive.
This circuit is shown in Figure 51.

Two types of circuits can create a differential output signal from a single-ended input without the use of any other components than resistors. The first of these is illustrated in Figure 52.

If a resistor (RF) is connected from the output of Amp 2 to the + input of Amp 1, negative feedback is provided which closes the loop. An input resistor (RI) will make the circuit look like a conventional inverting op amp configuration with differential outputs. The inverting input to this dual output op amp becomes Pin 4, the positive input of Amp 1.

The gain of this circuit from input to either output will be ± RF/RI. Or the single-ended-to-differential gain will be 2 X RF/RI.

The differential outputs can be applied to the primary of a transformer. If each output can swing ±10 V, the effective swing on the transformer primary is 40 V p-p. The optional capacitor can be added to prevent any dc current in the transformer due to dc offsets at the output of the AD815.

[wensan]

How about this.

[wensan]

It is a hard job to translate this article.

Does anyone can help me?

[carlmart]

Originally posted by wensan
It is a hard job to translate this article.

Can we have an idea what are they trying to achieve?

If it's just a differential signal from a single ended signal, it's too complicated and certainly far from the GC spirit.


Carlos

[darkmoebius]

Originally posted by carlmart
If it's just a differential signal from a single ended signal, it's too complicated and certainly far from the GC spirit.

Hi Carlos,

What do you think of the two designs from the AD815 datasheet?

Do you think they have any potential for sounding good?

I need a simple, but very good, preamp to convert the single-ended signal from my DAC(Tube-Lover's TDA1541A kit) to differential for the Zeus amp I'm building.

I suppose it really wouldn't cost too much to just breadboard Figure 51 and see how it works. But, I don't know what type of input transformer to get - 1:1, etc

[acliao]

Rowland Synergy uses similar topology from Figure 53 mentioned above.

[darkmoebius]

Hey Acliao,

Good to see someone else from this town is active around here. Are building anything interesting right now?

Rowland Synergy uses similar topology from Figure 53 mentioned above.

Any advantage over Figure 51?

I suppose that since Fig 53 has a transformer on the output, it is easier to lock the output impedence at a desired level like the standard differential 600 ohms or lower if need be.

Of course, you could just add another 1:1 line output trans to Fig 51 and get the same effect.

[peranders]

Peter what are you after really, a simple solution or?

DRV134 is simple but this IC a bit odd.

Buffer plus an inverting opamp, easy simple and works good (like in my QRP01) but not so cool or exotic maybe.

You can also use a differential stage etc etc.

Specifications?