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In Reply to: Re: The Beast is here.... posted by Dr. Philosophy on July 2, 2005 at 11:16:30:
You are right. I read it a couple of times and then it dawned to me.
Still to me it is somewhat odd, to have a balanced or differential signal, to make it single-ended or turn it into a "RCA" via interstage and then to split the phase again.It is nice to allow for bypassing the transformer but if I was a customer I would have liked to see the balanced signal go directly passed the phase splitter, no destruction and recreation. I am curious of the schematic.
It reminds me of my stock Sony SACD SCD-777 player. The signal from the DAC is differential. But they make it single ended - filter it - and in the case of the more expensive brother SCD1 use 4 Opamps to recreate a differential signal again.....
I always believed that it is not so simple to split the phase correctly. And if that is the case, why take it down and do it again?
The only explaination is: the amp is designed for single ended input sources or preamp.The input transformer is then used as some sort of interstage where the input of the RCA is using the transformer as 1:1 or 2:1 while the XLR sees a 1+1:1. But then the statement of the inferior method of turning a differential XLR signal to single-ended by connecting one leg to ground and instead taking a transformer, is in the same league as the statement being the most powerful OTL amp in the world.
Follow Ups:
Well you're getting beyond me technically, but: yes, the amp is not differential; the input transformer is there only to cope with balanced signals. The balanced signal has to be converted to a single-ended one; are you saying there's a better way to do it? If in this circuit the phase splitter could simply be bypassed in the case of a balanced signal then it's extremely unlikely Rozenblit would not have done it that way. Perhaps you should try emailing Rozenblit to see why he does it as he does. On the 'most powerful' comment - well, I doubt BR makes a habit of keeping up with what other manufacturers have been doing lately. Mere enthusiasim at getting the prototype done, no doubt. I wouldn't take that comment as evidence about his theoretical knowledge or engineering talents.
> On the 'most powerful' comment - well, I doubt BR makes a habit of keeping up with what other > manufacturers have been doing lately.FWIW, the MA-2 has been in production for the last 15 years...
... I had better shut up, as I am probably getting way out of my depth, in various respects.... !
Let me jump in here...I think what the DR. is saying
The amp IS push pull. A push pull amp requires two, out of phase, signals to drive the output tubes. If the input has a transformer, that transformer could be used to create the two out of phase signals from a single ended input and also pass the balanced (two out of phase signals) from a balanced source. In other words, the amp could be push pull all the way through. No need for a phase inverter circuit. Why are they not doing that?
Dr. Please correct me if I'm wrong...Tre'
Well sort of.Take an analogy. Say we have a color picture. We then turn that into black and white. Then we take that black and white picture and hand color it again... to turn it into a color picture.
Hand coloring for old black and white film is a good idea, as there was no color in the first place. For an original perfect color picture it is not such a bright idea.
The statement on the website that there was a better way to turn a color picture into black and white .. is something i did not get.
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