Question. Preamp

boq · 5th May 2004, 11:56 AM

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 ).

Alain Dupont · 5th May 2004, 04:52 PM

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.

zygibajt · 5th May 2004, 10:12 PM

Quote:

What is advantage of use a preamplier

much better sound!

Bartek

boq · 6th May 2004, 06:05 AM

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

b-square · 6th May 2004, 06:09 AM

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.

MBK · 6th May 2004, 06:49 AM

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

boq · 6th May 2004, 01:19 PM

Thanks MBK for explanation.

b-square · 6th May 2004, 02:14 PM

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.

MBK · 6th May 2004, 02:32 PM

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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5th May 2004, 11:56 AM	#1
boq diyAudio Member Join Date: Dec 2003 Location: Kraków	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 ).

5th May 2004, 04:52 PM	#2
Alain Dupont diyAudio Member Join Date: Sep 2003 Location: Paris - France	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.

6th May 2004, 06:05 AM	#4
boq diyAudio Member Join Date: Dec 2003 Location: Kraków	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

6th May 2004, 06:09 AM	#5
b-square diyAudio Member Join Date: Feb 2004 Location: Seattle, WA	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.

6th May 2004, 06:49 AM	#6
MBK diyAudio Member Join Date: Apr 2002 Location: Singapore	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

6th May 2004, 01:19 PM	#7
boq diyAudio Member Join Date: Dec 2003 Location: Kraków	Thanks MBK for explanation.

6th May 2004, 02:32 PM	#9
MBK diyAudio Member Join Date: Apr 2002 Location: Singapore	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.