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Do Preamps Sound Different


DANGERDAN
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Preamps are the soul for transfering analog or digital data to the amplifiers and are also capable of configuring the gain of frequency, now without touching the gain levels does the preamps sound different from eachother (connected from a digital source).

If so what kind of change is this, is it as big a change as between different amps ?, how do seperate preamps compare to standard receivers used as preamps.

Could you connect the RCA L/R cables directly into a power amp ? if not how come.

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I would say, No. At least they should not.

One otherwise respected audio reviewer said at one time that "all amps [power amps] sound the same." His statement has been widelystomped on.

My self authored chestnut is that all accurate amps must sound the same. Otherwise, they are not accuracte.

Power amps have a difficult job driving the speaker load. So there are issues there. Further, it is somewhat recognized that power amps which cause some forms of distortion sound warmer. Part of this may relate to our ear-brain complex. Our ear hardare causes harmonic distrortion and the brain filters it. Nonetheless, I suspect that amps with favorable distortion, and therefore are not accurate, sound better.

So we're in a difficult area, Amps which are electically accurate potentially sound worse that those which induce harmonics.

But that is pretty much the realm of power amps. Above.

If you look at the run of the mill pre-amp from years ago, you will find that they are only switch boxes for line level signals. These are the line-level signals from tape decks or CD players which just get sent to the power amp. Therefore we don't have any actual amplifier in the form of a tube orf transistor in the path.

Even if there is a transistor or tube, these devices are pretty much running in Class A bias into reasonable load, which is the best.

So, we can still look at line-level amps with some suspicion. Could it be that my "box" is messing things up? Probably not. At least before the digital age, there was a long string of similar "pre-amps" starting at the microphone output, then the mixing board, and then to some transmission or storage system.

Yet people think that the last chain in the link, which is pretty much the same design, causes a problem. Thiere is no engineering reason to think so.

WMcD

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In my experience over the years the preamp makes a huge difference. I personally think its right behind the speaker in the enormous of amount of change it makes from one to the other. I realize the source and room and location are all right up there as well but darn if the preamp hasn't been night and day for me.

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Guest David H

My self authored chestnut is that all accurate amps must sound the same. Otherwise, they are not accuracte.

I like Williams description, and agree all high quality preamps should sound very similar.

My equipment tells me all my preamps all sound the same, my experiance and amateur ears tells me they do not. The odd thing is the ones I build myself always sound better to me. BTW, my Grandchildred are cuter as well.

I am really not sure how much difference I hear when swapping preamps, but I like warmth I get from tube preamps. On a cold day I put my feet just above the tubes and can feel the warmth filling the room.

Dave

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Preamps are the soul for transfering analog or digital data to the amplifiers and are also capable of configuring the gain of frequency, now without touching the gain levels does the preamps sound different from eachother (connected from a digital source).

If so what kind of change is this, is it as big a change as between different amps ?, how do seperate preamps compare to standard receivers used as preamps.

Could you connect the RCA L/R cables directly into a power amp ? if not how come.

I have always thought that pre-amps make more difference in a stereo system than power amps, assuming that the latter are not driven into clipping. All amplifiers should be 100% accurate and thus identical, but the variations in design insure that this is not the case. Some are better (handle audio signals more accurately) than others and I have found that pre-amps are the most likely to vary. Perhaps this is because they are handling relatively low level signals, where a small change is more noticeable than it would be in a higher level signal.

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Preamps are the soul for transfering analog or digital data to the amplifiers and are also capable of configuring the gain of frequency, now without touching the gain levels does the preamps sound different from eachother (connected from a digital source).

If so what kind of change is this, is it as big a change as between different amps ?, how do seperate preamps compare to standard receivers used as preamps.

Could you connect the RCA L/R cables directly into a power amp ? if not how come.

As to comparing receivers and seperate pre-amps, the latter should be considerably better, as they are not sitting inside a metal box with tuner and power amplifier circuitry. Also, if you spend, say, $1000 for a receiver, that money must be divided between a pre-amp, AM tuner, FM tuner and power amp. Each part has received maybe 1/4 to 1/3rd of the design time and money. Spend $1000 for a pre-amp and it can be designed and built with much greater care. In this sense, less for a given amount of money really is more.
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"If you look at the run of the mill pre-amp from years ago, you will find
that they are only switch boxes for line level signals. These are the
line-level signals from tape decks or CD players which just get sent to
the power amp. Therefore we don't have any actual amplifier in the form
of a tube orf transistor in the path. "

Older preamps have about 20dB of gain from line-level inputs to the pre out.

Phono preamps have about 40dB of gain.

Power amps have about 26dB of gain.

With a 1mV signal from a moving magnet cartridge, +40dB=100mV.

100mV into the line stage +20dB=1V.

1V into the power amp +26dB=20V.

20V into four ohms is 100W.

Red Book standard for a CD recorded at maximum level (few are) is 2V out, so that will drive most amplifiers without a preamp. You will probably have to turn the level on a passive preamp all the way up to get it loud, and some program material may not drive the amplifier to full output.

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  • 2 years later...

"Passive" preamps suffer from a number of problems, not the least of which being difficulty in dealing with their (usually very high) output impedances trying to drive the capacitance of long runs of IC. In many vintage tube amps, which often have input impedances in the range of .5 meg ohm, as well as input voltage sensitivities very suitable for this application, it's not only quite possible to drive such an amp from a CD player directly, but in many cases push it into clipping distortion. Using a resistive attenuator in front of an amplifier with a fixed grid leak or grid-to-ground resistor (which in the case of the Dynaco is the .5 meg resistor to which I referred above) is NOT the same as replacing that fixed grid resistor with a variable potentiometer of the same value -- which is what is done with many older integrated hollow state amps, as well as more recent variations. The main problem with a so-called passive pre has to do with the fact that it requires not only an adequately high input impedance, but a suitably low output Z. For resistor-based devices, the balance is not always easy -- so I agree with you on that account. And that is often how passives are used simply because many don't know how to replace a fixed input resistor with a variable potentiometer. I have amplifiers that would be unbearably loud if the full ouput of a CD player were plugged directly into the amplifier, thus I will maintain that most people use a preamp, either passive OR active, as a signal reducer rather than an amplifier for modern, high line-level outputs. In such a case, one can install the potentiometer directly on the amp, and use a simple switch box, only (with no attenuator) to switch source components. If one is going to go the passive pre route, a very effective way of doing it uses transformer-based attenuators, where a very high input impedance is present (very goos thing) but where the output impedance into the amplifier is very, very low (also a very good thing) and will thus not only be able to handle long runs of interconnect, but will have arguably improved frequency response, as well. Moreover, many transformer-based passive devices, despite being essentially passive and are devoid of any power supply, are able to provide a small amount of gain, which in some cases might be helpful. The majority of amplifiers I have made have on board volume controls in placed of the fixed resistor on the grid of the first stage -- and need no greater input voltage (in fact they need much less) than that of the CD player.

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...now without touching the gain levels--do preamps sound different from each other (connected from a digital source)?

They shouldn't, but they do. The type of amplifier downstream will also help to determine the answer to your question, as well as the speakers connected to your amplifier and room/acoustics. Bummer...

Could you connect the RCA L/R cables directly into a power amp?

Note that using RCA analog connections mean that you are using the DAC in the upstream device to convert from digital domain, and then amplified by the upstream device's internal preamplifier. You can take a significant performance hit for doing this, IMHO. I recall that you are the one that has talked about high-priced DACs. I think what you are buying in higher priced DACs is actually a high-priced preamp - with a slightly improved performance from the DAC. The use of RCA (analog) cables isn't what I prefer to use, however, unless they are going directly to power amplifiers. However, I prefer using XLR (balanced connections) to the amplifier(s) to eliminate power line hum (e.g., 60/120 Hz in U.S.).

I find that using HDMI digital bus from any CD player into a high quality preamp/processor (AVP) with excellent DAC(s), analog preamplifiers, and better EMI/EMC box shielding--significantly beats any garden variety CD player with inexpensive DAC, output preamplifiers, and associated output RCA cables.

Chris

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Could you connect the RCA L/R cables directly into a power amp ? if not how come.

My OPPO has a volume control that is controlled by the remote and I have hooked it straight to the amplifiers with good results. The only downside is the inability to switch sources, so I am not running it direct right now.

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Could you connect the RCA L/R cables directly into a power amp ? if not how come.

My OPPO has a volume control that is controlled by the remote and I have hooked it straight to the amplifiers with good results. The only downside is the inability to switch sources, so I am not running it direct right now.

Alternately, you could use an amp with gain controls. I prefer that route myself, running the source full hot to maximize S/N on the signal feeding the amp. No remote, of course, but que sera sera.

Weather you use Chris' method (AVR), Dan's, or mine, the gist is this: once the signal is converted to analog, get it to the amps as directly as possible, sans any intervening analog stages, as they can be either transparent or less than transparent, but not more transparent.

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My OPPO has a volume control that is controlled by the remote and I have hooked it straight to the amplifiers with good results.

FYI: it was an Oppo DVD player (the one identified in my profile) that has severe problems in its analog output (RCA) to my preamp - that I found quite by accident using a CD that pushes the redbook limit without clipping or compression.

The same story for the PS3 analog output - it just doesn't sound very good to my ears on my setup. I now use HDMI from both sources into an AVP with excellent results: I can't hear any difference between these two players using digital (HDMI) buses.

My AVP has an effective "Pure Audio" mode that shuts down parasitic noise sources (including front panel display) inside the box to increase the preamp's effective SNR.

Chris

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I can make my preamp sound different than ITSELF...........just change the tubes.

Also, my Peach preamp sounds completely different than my McIntosh C220 preamp............yes of course using the exact same amp.

The notion that all amps and preamps sound the same is completely absurb. Sometimes 2 of the exact same model even sound different.

I'm not saying it is right or wrong..........just true.

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The notion that all amps and preamps sound the same is completely absurb. Sometimes 2 of the exact same model even sound different.

That's a rather compelling argument for skipping the pre-amp completely. After all, there is no pre-amp as crystal-clear, transparent and uncolored as literally no pre-amp.

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