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Old 5th May 2004, 11:56 AM   #1
boq is offline boq  Poland
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Question Question. Preamp

Hello.
I have question that probably makes most of You laugh.

What is advantage of use a preamplier (BOSOZ for example) since its output level is 2V (best sound quality). The same as directly from CD.
At input signlal is attenuated then signal is distorted and amplified to similar level.
What I get by using preamp. (except valume control ).

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Old 5th May 2004, 04:52 PM   #2
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boq,

With a Bosoz or X-Bosoz even CCS-X-Bosoz you get the finest unbalanced to balanced adaptor.

You can switch between inputs, using balanced or unbalanced

You can also get a fine impedance adaptor.

And even a balanced stepped volume attenuator with 128 or 256 positions...

Perhaps a remote control for inputs and volume... + mute...

And finaly a trigger to start the class A amplifier you are listening to...

.... Otherwise you can use a dual 10 K pot right after the CD...

Regards.

Alain.
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Old 5th May 2004, 10:12 PM   #3
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Quote:
What is advantage of use a preamplier
much better sound!

Bartek
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Old 6th May 2004, 06:05 AM   #4
boq is offline boq  Poland
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Thanks Alain and Bartek.
My question was related to sound quality and I still don't know why preamp is better than simple potentiometer.

Wojtek
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Old 6th May 2004, 06:09 AM   #5
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The #1 reason is convenience.

Alternatives to a potentiometer in a box include using a player or DAC with variable outputs or passive systems that are generally superior to potentiometers, like transformers and autoformers.
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Old 6th May 2004, 06:49 AM   #6
MBK is offline MBK  Singapore
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A passive colume control is fine in theory. But in many, many cases the CD output, though it has enough voltage, doesn't have enough current output capability to supply the loss through cable capacitance, attenuator and attenuator capacitance, and input impedance of the power amp. If you experiment with a breadboard, it's easy to test a simple pot against a pot with a unity gain buffer in front of it (an active preamp in other words). Whenever I did that, the dynamics improved a lot with the active stage to boost the CD output.

Many people like the fine microdynamics of passive volume controls. I suspect it's because the macrodynamics don't make it over to the power amp
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Old 6th May 2004, 01:19 PM   #7
boq is offline boq  Poland
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Thanks MBK for explanation.
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Old 6th May 2004, 02:14 PM   #8
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Quote:
Originally posted by MBK
Many people like the fine microdynamics of passive volume controls. I suspect it's because the macrodynamics don't make it over to the power amp
I suspect you haven't heard a system with a TVC.
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Old 6th May 2004, 02:32 PM   #9
MBK is offline MBK  Singapore
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Actually I haven't, and I keep an open mind. The impedance matching and CMRR (and inherent RF rejection) of a TVC is something I can see clear potential advantages from. But simple resistive passives often don't work all that well IMO. Unless the previous stage has a strong output of course.
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