unbalanced to balanced converter

[lumanauw]

The x amp like alephx, SOZ, are indeed a very-very good amp. But mostly we have unbalanced input source (cd player, etc).

I think about having balanced zen line stage, to make a perfect unbalanced to balanced converter. but Grataku said this :

This topic has been popping up about once every four months for the past 2 years so you maybe aware of it. You shouldn't expect miracles from this circuit. The BOSOZ is not a great unbal-to-bal converter, actually a user has already posted simulations of the circuit that quite clearly show different voltage levels from the hot and the cold outputs when the cold input is unused, or grounded, in SE operation. The same guy has already posted a version with current source which performs better "instrumentally". If you want a Pass original circuit you could go for the AlephP that has a full complement of current sources

So what will be the perfect unbalanced to balanced converter will be like, in terms of x passlabs diy amps.
I'm trying not to go to opamps, to match the novelty of aleph amps. What will it be like if we wanted to use hot mosfets?

 

[jh6you]

Which one is perfect?
Which one is the miracle?

If the gap is acceptably narrow between imperfection and perfection, the imperfection could be considered virtually perfect. BOSOZ with the constant current sources (even without CCSs) reaches to our satisfaction technically and musically, in my opinion.

I would like to see who comes up with the perfect one with both technical and musical satisfactions.

 

[sianturi]

BZLS with CCS

Hello lumanauw,

Salam audio!

the original BZLS will have an absolute voltage difference between hot and cold output if you run it with unbalanced source. I have already simulate it.... A guy from china had also probed the real world BZLS circuit with unbalance input, and it indeed showed the voltage difference (he posted the result in this forum with the picture of his osciloscope readings).


If you want to make BZLS a (near) perfect unbal-to-bal converter (in terms of voltage diff at the outputs), i've made some simm in this thread:

http://www.diyaudio.com/forums/showthread.php?threadid=25489

Probably you have to change the Q5 transistor for a higher voltage ratings. I'm still collecting parts for that circuit, and haven't had time to make the PCB at Bandung (I'm in Jakarta). Also, I'm having trouble with a low WAF.

Budak nu kasep,

 

[Faber]

The simplest way is to introduce a current source that replaces the two 750Ohm resistors.

This works fine for me and the mod is simple and fast to implement.

Bye!

 

[hifimaker]

Here's another thread regarding unbalanced-to-balanced converters that might be helpful.

http://www.diyaudio.com/forums/showthread.php?s=&threadid=2687

-David

 

[eLarson]

And when you use the current sources you can decrease the value of the negative rail to decrease dissipation.

 

[Luke]

Nelson suggests the use of pots on the outputs to trim the output voltage so as its balanced. This seems quite easy to do.

 

[Nelson Pass]

That's a nice circuit, Fabrizio, and would do the job very well.
Input and output pots are a welcome addition to make certain
that it fits into all occasions, and it is my experience that a cap
across the zener will drop the noise quite a bit.

But I do think you need some Emitter resistors on the
current source transistors to stabilize the current values.

 

[kristijan-k]

Quote Faber: 'The simplest way is to introduce a current source that replaces the two 750Ohm resistors'.

The circuit below is an X design of the BOSOZ and with the CCS.

The circuit runs at 88 mA bias per rail, so watch out on the
power rating of 680 R resistors (dissipation around 5 W ).

Best regards,
Kristijan Kljucaric

 

[kristijan-k]

XCCS-BOSOZ Power Supply:

The transformer rating is for the one channel.
For stereo use 80 VA or higher.

 

[lumanauw]

jh6you,

You have been in this problem for some time. Could you share what is your unbalanced to balanced converter you are using right now?

So, BOZOS can be made to a perfect match for unbalanced to balanced converter for passlab x amps. But some noted that it has to have CCS instead of resistors.

Wouldn't this be the AlephP 1.7? Looking at the sch of ver1.0 and 1.7, the difference is there are CCS on every corner at ver1.7. Would this really helps the imbalance problem?

One more thing. BOZOS are +/-60V, alephP1.7 are working only by +60V. If I have to choose, I will go for the lower rails, that is the alephP 1.7.
Could this AlephP 1.7 working from +/-30V instead of +60V? The inputs and outputs are Capacitor coupled, so I think there should be no problem in making this AlephP working at +/-30V. (I will put the grounds at original AlephP to -30V, and put the input and output resistance to ground).

 

[jh6you]

My BOSOZ is as follows. I hope this will be a useful reference for you.

Here is the amp.

 

[jh6you]

and the psu.

 

[Faber]

it is my experience that a cap
across the zener will drop the noise quite a bit.

But I do think you need some Emitter resistors on the
current source transistors to stabilize the current values.

Thank you Nelson.
Do you think this kind of values shoul work fine? Or the cap can be smaller?

thanks!
bye

 

[protos]

Ok a question for the experts.How would you go about getting a minimum absolute dc offset between the halves without resorting to complicated solutions and extra semiconductors.The reason I ask this is that absolute DC becomes quite high when you start decreasing the inter source resistor to very low values or none at all.

 

[PMA]

With OA:

 

[thanh]

How is the gain of XCCS_BOSOZ?
thanks!

 

[kristijan-k]

Hello thanh,

The gain is little over the 10 dB, but it can be adjusted by
changing the 68 R resistors, or place the pot between
sources of the gain transistors.
The 68 R resistors should be rated at at least 1 W.


Best regards,
Kristijan Kljucaric

 

[jh6you]

Your post#9 preamp can work also as an unbalanced-to-balanced converter...??? If so, how it works...???

 

[thanh]

HI Kristijan-k!
So how can i calculate the gain of it?