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Old 10th July 2003, 05:12 PM   #1
Quattor is offline Quattor  France
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Question Pre/power amp question...

Hi ya all!

I?m building a pre/power amplifier combination where power amplifier will actually have four amplifiers inside for bi-amping purposes. I?ve two ideas currently on my mind and I?m not quite sure which one is going to be:

a) Power amplifier will be placed between speakers, active crossover will be inside it and the signal from the preamplifier will travel in a balanced manner. For: very short speaker cables. Against: Low level signal passing through long balanced line (although there is a buffer behind the volume control in preamplifier).

b) Power amplifier and preamplifier will be placed together, away from the speakers, active crossover will be placed inside preamplifier. For: very short interconnection between preamplifier and power amplifier. Against: Long speaker cables.

Now, there are few more for and against for each of those topologies, but I?m not into typing right now ?K

Anyway, what do you think? I like the a) solution a little bit more but I?m still banging my head about itK

Thanks in advance!
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Old 10th July 2003, 09:59 PM   #2
Quattor is offline Quattor  France
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Default No comments?!

Anyone?!!
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Old 11th July 2003, 11:39 PM   #3
moamps is offline moamps  Croatia
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Default Re: Pre/power amp question...

Quote:
Originally posted by Quattor
[B]
a) Power amplifier will be placed between speakers, active crossover will be inside it and the signal from the preamplifier will travel in a balanced manner. For: very short speaker cables. Against: Low level signal passing through long balanced line (although there is a buffer behind the volume control in preamplifier).
b) Power amplifier and preamplifier will be placed together, away from the speakers, active crossover will be placed inside preamplifier. For: very short interconnection between preamplifier and power amplifier. Against: Long speaker cables.
Hi,

c) classic active speaker (2ch amp+XO in speaker)+ separate bal. preamp
d) my suggestion: 2ch amp + XO in one chassis, separate preamp. Then you can do experiments with amps positions and all cable lenghts.

Regards
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Old 15th July 2003, 03:49 PM   #4
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In my opinion you should keep the low level signal cabels (between preamp and power amp) as short as possible, and invest in some thick speaker cables.
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Old 15th July 2003, 06:13 PM   #5
PMA is offline PMA  Europe
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Place power amplifier as close to the loudspeakers as possible, use as short speaker cables as possible with minimal L and R. Preamp should be close to signal source. Link preamp and power amp by means of Audio Buffer, you will find it at http://www.pha.inecnet.cz/macura/buffer_en.html
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Old 15th July 2003, 06:42 PM   #6
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PMA:
You can do that, but you will then putt yet another component (with distortion etc.) in your signal path...................
I cant see the purpose of that in HI-FI
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Old 15th July 2003, 07:54 PM   #7
PMA is offline PMA  Europe
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I now what you mean and I understand you. But: THD and IMD inserted is about 0.001%. Many listening tests were done, speakers as good as Wilson Audio Maxx, B+W Matrix 801. Also small 2-way bookshelf speakers. Improvement is incredible (tough bass, pure mids and treble, no grain). I would not believe it if I did not build it and listened to it. The circuit can be implemented as an output stage of a preamp.
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Old 15th July 2003, 08:06 PM   #8
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PMA: And I understand you... But take a look in this forum....

Why do you think that there are so many discussions about circuit design??? Because ALL circuits adds or deducts something...

Chech even the Pass forum. Mr. Pass is quite intelligent and good at designing circuits, however they can still be mproved.....: bigeyes:

You can compare your suggested buffer to any amplifier circuits,
- meaning that there are 1000 ways to do it, each with its own advantages and disadvantages...

So my oppinion is still:
Bad sonic sound is rearly caused in high power cabels.
They are caused by bad circuits and inprober low level signal cabels... No offends!!!!
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Old 15th July 2003, 08:42 PM   #9
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Jan,

that's why the influence of signal cables is neglected by the Buffer, and the cable must be terminated (R10 and R12), probably to suppress dielectric phenomena. This was also difficult to diggest for me . I am an electrical engineer as you, for all of my life I've been designing circuits and instruments. Graduated in electro-acoustics .
It is interesting, but even a 50 cm of non-buffered non-terminated signal cable makes a trouble. And speaker cables? Forget that they are all the same when having high cross-section area. The better sound chain you have, the more you are able to distinguish. The experience is not transferable, so I am not going to argue more

Pavel
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Old 15th July 2003, 08:46 PM   #10
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Hello again PMA,
Ok! No more argue..
You have stated your point and I stated my point.

Thats the good thing about audio....
We all have our preferences....
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