Balanced Crack

albertoduarte · 11272

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Offline ivigueras

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Reply #15 on: March 28, 2014, 01:00:37 AM
Hello.

This is my first post in this forum and I'd like to recover this question.

I've recently purchased and built a Crack+Speedball. I'm very happy with that and my Senns HD600. But now I'm thinking in a balanced amplifier to use my 600 in balanced mode. I wonder if it would be possible with adding another Crack and build a simetric balanced amplifier with two Cracks.

Then, the question again is if is possible build a balanced amp with two Cracks.

In balanced mode, output to the phones must be only connect + and - lines each channel and amp, not ground. And I don't know if it is possible with a OTL, and how this affects to the output impedance.

Thanks,
Ignacio



Offline Doc B.

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Reply #16 on: March 28, 2014, 06:02:52 AM
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 (-).

So you will need an inverter ahead of each amp and of course a reconfigured headphone connection with a hot and cold connection for each channel.

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.

Dan "Doc B." Schmalle
President For Life
Bottlehead Corp.


Offline Paul Birkeland

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Reply #17 on: March 28, 2014, 07:24:37 AM

Then, the question again is if is possible build a balanced amp with two Cracks.


Hello Ignacio,

I built this amp some years ago, before the Crack came out:
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fusr.audioasylum.com%2Fimages%2F2%2F27873%2FDSCN2398.JPG&hash=6c6019c93f1c175ed221225a0a8217d729ec1bae)
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 "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Kris

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Reply #18 on: March 28, 2014, 08:14:17 AM
Paul, that looks great. I can't even imagine how much time you spent to experiment and build that beast.
Also... are these HD600? Neeeah...they are probably HD600 mutated with HD800, mutated with some Beyerdymanics... etc.
How long ago was that picture taken?
« Last Edit: March 28, 2014, 08:18:35 AM by Kris »



Offline Paul Birkeland

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Reply #19 on: March 28, 2014, 09:07:44 AM
I built that very early in 2008. 

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline JamieMcC

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Reply #20 on: March 28, 2014, 09:36:59 AM

Hello Ignacio,

I built this amp some years ago, before the Crack came out:
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fusr.audioasylum.com%2Fimages%2F2%2F27873%2FDSCN2398.JPG&hash=6c6019c93f1c175ed221225a0a8217d729ec1bae)
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.

Shoot for the moon if you miss you will still be amongst the stars!


Online Paul Joppa

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Reply #21 on: March 28, 2014, 04:02:55 PM
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 ...  :^)

Paul Joppa


Offline Doc B.

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Reply #22 on: March 28, 2014, 08:07:49 PM
How about two motorcycle engines in one car?

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

Dan "Doc B." Schmalle
President For Life
Bottlehead Corp.


Offline ivigueras

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Reply #23 on: March 29, 2014, 03:01:01 AM
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.

 :D 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.



Offline Paul Birkeland

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Reply #24 on: March 29, 2014, 08:48:50 AM
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.   

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Doc B.

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Reply #25 on: March 29, 2014, 08:52:50 AM
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.

Dan "Doc B." Schmalle
President For Life
Bottlehead Corp.


Offline ivigueras

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Reply #26 on: March 31, 2014, 05:05:10 AM
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.



Offline Doc B.

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Reply #27 on: March 31, 2014, 05:15:04 AM
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.

Dan "Doc B." Schmalle
President For Life
Bottlehead Corp.


Offline ivigueras

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Reply #28 on: March 31, 2014, 05:52:03 AM
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.