Balanced Crack

[JamieMcC]

Hello Ignacio,

I built this amp some years ago, before the Crack came out:

In all honesty, a single Crack sounds much, much, much better than this amplifier ever did, despite the massive amount of work and experimentation that I undertook in attempting to get this right. 

-PB

Paul I love the thought and attention to detail of your builds like the way the (Daytons?) capacitors show through the top plate or the offsets on the smaller tubes.

 

[Paul Joppa]

By doubling the amp and inverting the phase on one side, you create two other effects besides "balanced" outputs. These effects do not occur when you use a transformer to generate the balanced signal, as in the Mainline:

1) You have made a push-pull amplifier, which has quite a different distortion spectrum and does not sound the like a SE amp.

2) You double the output impedance, which is already a limitation of the Crack.

I'm not predicting whether these differences will sound better or worse to any particular listener - we are all different. And it's an exaggeration to compare this to making an automobile by strapping two motorcycles together ...  :^)

 

[Doc B]

How about two motorcycle engines in one car?

http://sundoulos.us/vehicles/sportstar.aspx

 

[ivigueras]

Thanks a lot for the answers.

You can do this with pretty much any stereo amp. The process is to invert the signal going into one half of each of your two amps. Then you configure the output +/- from the signal + output of each channel, the noninverted + output will remain as signal hot (+), the inverted + output will become signal cold (-).

Thank you, Doc. Yes, I knew that. It's not really necessary in my case because I want to use a balanced source. This is the reason why I thought in build a full symetric balanced amplifier: maintaining the signal fully balanced from the beginning until the end.

Or you could sell the Crack and use the proceeds to finance a Mainline, which is already set up to do this more cleanly and more easily. You could also do this with a S.E.X. amp by installing the impedance switching kit and making an adapter that goes from the speaker binding posts to whatever connector you use for your balanced headphone cable.

Doc, don't believe that I didn't thought it!
But, for the same reason, I don't want a SE amplifier and convert to balanced in the output as I think do the Mainline (I don't know deeply the Mainline and I can be wrong). I don't think that it will be a real improvement. In fact, the Mainline's reviews that I've read agree with the opinion that there are only a light improvement using the balanced output with the HD600. In this case, I prefer use the SE Crack that is really marvelous as well.

By doubling the amp and inverting the phase on one side, you create two other effects besides "balanced" outputs. These effects do not occur when you use a transformer to generate the balanced signal, as in the Mainline:

1) You have made a push-pull amplifier, which has quite a different distortion spectrum and does not sound the like a SE amp.

2) You double the output impedance, which is already a limitation of the Crack.

Thank you, Paul. That explains me the things.

 

[Paul Birkeland]

Thank you, Doc. Yes, I knew that. It's not really necessary in my case because I want to use a balanced source. This is the reason why I thought in build a full symetric balanced amplifier: maintaining the signal fully balanced from the beginning until the end.

The real question here is why?

Having built plenty of fully differential circuits (which has somehow morphed into being called "fully balanced"), they are all amps that sit on the shelf and don't get any play time.   

 

[Doc B]

I apologize, I misspoke. I should have clarified going into this that you are asking about a differential, i.e., push pull conversion. That is different than balanced output. Thanks Peej for clarifying.

 

[ivigueras]

Thank you, Doc. Yes, I knew that. It's not really necessary in my case because I want to use a balanced source. This is the reason why I thought in build a full symetric balanced amplifier: maintaining the signal fully balanced from the beginning until the end.

The real question here is why?

Hello Paul. Probably it will be a misconception from mine. If I have a balanced (or differential) source and I want balanced outputs in the amp, I think that is a better way keep the differential signal all the path instead convert to SE in the input and convert again in the output.

Ignacio.

 

[Doc B]

PB probably summed up the combined firsthand experience we can give you with his opinion of the amp he built. It's certainly possible from a technical standpoint. Beyond that I think you will just have to try it and see if you like it.

 

[ivigueras]

Thank you, Doc.

Yes, I must think it very slowly. Until now I was only wondering if it would be possible (due to the nature of the amplifier OTL).
It isn't a cheap experiment. Not only I need a new Crack+Speedball, I also need paired tubes.

Thanks to all for help!

Ignacio.