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lad
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why use a preamp?

I recently hooked the denon cd player with a volume control directly to my adcom 545 II power amp and noticed an improvement in the clarity of both highs and bass response. The sound stage dimished a touch with a slight loss of airyness. My question is can I increase the soundstage by going with a passive preamp and still keep the clarity and lack of harshness I am currently enjoying?

dbowker
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Re: why use a preamp?

Yes to all your questions. A good pre-amp (active or passive) can do a lot to give the amp a better and cleaner signal, not to mention allow for more than one source.

bertdw
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Re: why use a preamp?

I think it's just as likely that a passive preamp will make things worse. Simply adding a volume control and an extra set of interconnect cables could do more harm than good.


Quote:
I recently hooked the denon cd player with a volume control directly to my adcom 545 II power amp...

Is this volume control in the Denon, or something you connected externally? If you're using the Denon's variable outputs at the moment, a better quality volume control (as in a good passive preamp) used with the Denon's fixed outputs may help. It would be nice, of course, if you could try a passive preamp in your system before you buy it.

bertdw
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Re: why use a preamp?

Here's another thought - have you tried moving the speakers around a bit since the change? I'm sure I don't have to tell you that speaker position and toe-in dramatically affect the soundstage. With your new found clarity, maybe a slight change in positioning will give you what you want.

lad
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Re: why use a preamp?

Signal goes from variable output from the denon and that provides plenty of volume. Running the system this way provide great clarity and reveals any flaws in the cd recording. I have not moved the speaker arrangement just to get a good comparison of before and after. Those adjustment will occur now that I know the difference. I removed the denon preamp because of the clarity issue and would only replace it if I can keep this clarity with a more pronounced and enhanced sound stage.

SAS Audio
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Re: why use a preamp?


Quote:
I recently hooked the denon cd player with a volume control directly to my adcom 545 II power amp and noticed an improvement in the clarity of both highs and bass response. The sound stage dimished a touch with a slight loss of airyness. My question is can I increase the soundstage by going with a passive preamp and still keep the clarity and lack of harshness I am currently enjoying?

There are some pros and cons to using a passive. Cost is one advantage as well as simplicity vs an outboard preamplifier.

The con is that of load capacitance vs impedance. The output of many use a variable output impedance, so it much be kept low in order to keep the frequency response reasonable. However, if the input impedance is too low then it will load the output of the player with possible loss of frequency response and increased distortion.

Another thought is to look at the quality of the mute and especially the analog stage(s) in the player. Many times the use of a separate preamplifier is better than that used in CD players with their cheap analog stages.

Just some thoughts.

bertdw
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Re: why use a preamp?


Quote:
Another thought is to look at the quality of the mute and especially the analog stage(s) in the player. Many times the use of a separate preamplifier is better than that used in CD players with their cheap analog stages.

Perhaps I've misunderstood, but how do you propose to bypass the audio stage in the CD player? Adding a preamp between the player and the power amp, even from the fixed outputs, will still leave the potentially inferior audio circuitry in the path.

absolutepitch
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Re: why use a preamp?

lad,
I have heard improvement in sound running a FM tuner that has a volume control directly into a power amp when compared to running the signal through a pre-amp first. And as "dbowker" says, you do get extra inputs on a pre-amp.

However, I have found that any electronics in the chain, passive or active, reduces clarity of the signal (sound). My best example is completely bypassing the tone control section of the preamp resulting in better sound. Yet that test is not completely scientifically correct, as the output before the tone controls is a different impedance from that after the tone controls section of the preamp. It just sounds better that way.

SAS Audio
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Re: why use a preamp?


Quote:

Quote:
Another thought is to look at the quality of the mute and especially the analog stage(s) in the player. Many times the use of a separate preamplifier is better than that used in CD players with their cheap analog stages.

Perhaps I've misunderstood, but how do you propose to bypass the audio stage in the CD player? Adding a preamp between the player and the power amp, even from the fixed outputs, will still leave the potentially inferior audio circuitry in the path.

Hi Lad,

I think you misunderstand me. After the DAC chip, which changes digital to analog, there is an analog stage(s) followed by a mute stage. The gain of this analog stage is only approx 9db. This stage is rather cheap and inferior.

I have been testing a few cd players with bypassing both the analog stage(s) and mute stage and running the signal output directly from the output of the DAC chip itself. It does take a superior preamplifier and costs more, but I feel it is worth it. All the parts in a cd analog stage are probably less than $5.00 total.

Hope this clears things up.

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