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Do "pre-amps" even exist?
- Thread starter CharlesC
- Start date
- Thread Starter
- #3
Last year on a podcast I heard a maker of expensive pre-amps say that pre-amps are important because the signal (impedance?) coming off a DAC might not perfectly match what the power amp is expecting. Not sure I believe this but I've been wrong before, today even.
solderdude
Grand Contributor
Pre-amps exist in many forms, active, passive (yes, one can even amplify passively !) , phono RIAA pre-amp, MC->MM preamp.
Some pre-amps have many functions, input selectors, tone controls you name it.
So the word pre-amp is kind of a wide concept.
Some pre-amps have many functions, input selectors, tone controls you name it.
So the word pre-amp is kind of a wide concept.
House de Kris
Member
Your question caught my eye, and made me think a bit. I haven't actually shopped for a preamp in a number of years, so I, too, began to wonder if they exist. My current preamp is an old Theta Casablanca, so I searched for Theta and found they still make a Casablanca, several generations newer than mine, plus another model. I came away from that quick Web search confident that preamps STILL do exist. Even searching on "stereo preamplifier" at Amazon yielded a number of good leads. Where did your investigations take you?
Heck, even everyone's favorite punching bag around here, Paul McGowan, makes a couple preamps. These things are everywhere!
Heck, even everyone's favorite punching bag around here, Paul McGowan, makes a couple preamps. These things are everywhere!
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It can certainly have an effect especially at high attenuation levels. Check out the Schiit Saga preamp review and you'll see that output impedance of the preamp changes depending on the attenuation level. Of course, if the power amp has a low input impedance, the sound can deviate from the original due to damping factor effect https://www.audiosciencereview.com/...easurements-of-schiit-saga-tube-pre-amp.6520/
- Thread Starter
- #7
Although I’m sure this is all true, it’s odd that DAC makers add attenuators to their devices and say “just hook them up to a power amp and you’re good to go”.
Most of the built-in preamp function are digital attenuators and as such they do not need resistors/potentiometer to attenuate an analog signal which makes them immune to output impedance variation
Hypnotoad
Active Member
- Thread Starter
- #10
Fascinating. Thanks.
Dimitri
Senior Member
Once upon a time, there were two types of source and the need to select among three or four.
Low level and high level.
Low level sources were from microphones and record cartridges and the level was in the 1mV to 5mV range (1mV being 0.001V)
High Level sources were things like Tape/Cassette players and Tuners. (CDROM not invented yet).
Those "high level" sources were outputting a level around 300mV, (line level)
Most sensible people, the ones that listen to music with imperfect speakers in imperfect rooms with non standard ears, wanted to be able to tailor the sound so that's where tone controls came in. You could adjust the Lows, the mds and the highs (As in Bass, Mid, Treble).
...and that 1-5 mV or 300mV from the selected source had to to somehow get boosted to be able to drive the final stage of an amplifier.
So a line in the sand was drawn (not sure by whom, or when and when it came to "separates",
a preamplifier included the Input selector, tone control and enough amplification to get the output to at least 1Volt (although most preamps could do a lot more )
...and the final amplifier "expected" at least 1V or 2 in order to reach it's rated output.
Once CD players came around they were outputting close to 1V or more.
You could connect the output of a CD player to the input of a final amp and rock the neighborhood.
And then since digitall was so clean, pure and pristine (cough cough), the Tone controls were "marring the sound".
In fact since digisal as so clean, pure and pristine, you didn't need the the tone controls messing with the purity of the digital sound.
So the need to "pre" amplification kinda went away. The elimination of the "dirty" tone control went away (to the satisfaction of the ears of the purists and let's not forget eliminating the added cost in design and manufacturing of these tone controls.
So you ended up needing an input selector and volume control.
So the oxymoronic term "passive preamplifier" was born.
And it all went downhill from there.
A box with a selector switch and volume control for two grand.
<insert swear words here>
We still have microphones that need preamplifiers.
We still have phono cartridges that need preamplifiers with fr. equalization.
Just to name two. And we may have good reasons to use very good linear preamplifiers even for digital sources, as shown elsewhere.
We still have phono cartridges that need preamplifiers with fr. equalization.
Just to name two. And we may have good reasons to use very good linear preamplifiers even for digital sources, as shown elsewhere.
Pre amplifiers were useful to bring inputs to the same level (and apply an RIAA equalization curve to phono), to control volume, have balance and tone controls (plus sometimes filters) and to switch between sources. If you no longer use analogue sources, and since the 2 Volt CD redbook standard has become the de facto standard for other digital sources as well, a DAC with volume control and multiple inputs can easily serve as a preamplifier. Here, the RME ADI-2 DAC is particularly useful since it also has the traditional and still very useful options of balance and tone control, dynamic loudness, and some filters. So I use it as a preamplifier into my Quad 606-2 power amplifier (with some inline attenuators to match levels, but that is a Quad specific issue, given their traditional 0.5 Volt input sensitivity). It works a treat.
[QUOTE = "CharlesC, publicación: 282529, miembro: 11534"] para ir ". [/ CITA]
Well, I thought it was to connect directly to the amplifier to the dac and use it beforehand (before I had a previous rotel rc970bx between the d50 topping and the nx255mp hypex ncore amp). Yesterday I sold my pre-Rotel and changed my d50 topping on Amazon for the new 50s and I have it connected directly to the hypex. But my problem is that I believe that the dac cannot lead to the amp, but I feel that there is no gain. For normal listening I have to take it up to -30 dbs. does anyone know what could be happening to me ??
Well, I thought it was to connect directly to the amplifier to the dac and use it beforehand (before I had a previous rotel rc970bx between the d50 topping and the nx255mp hypex ncore amp). Yesterday I sold my pre-Rotel and changed my d50 topping on Amazon for the new 50s and I have it connected directly to the hypex. But my problem is that I believe that the dac cannot lead to the amp, but I feel that there is no gain. For normal listening I have to take it up to -30 dbs. does anyone know what could be happening to me ??
For a while I wanted to build a modular system with a separate general preamp and amp, but it seems to be the norm that standalone preamps for whatever reason seem to cost like an order of magnitude more than integrated amps/receivers. So at some point I threw up my hands and said "audio stuff is stupid" and just kept what I have, which is what I usually do. It's funny to think how much more money I'd spend on this stuff and how much more fun I'd have if everything wasn't so egregious.
- Thread Starter
- #16
I have a D50S running into a pair of NC250MPs at about -20db to -30db. Didn’t know it was a problem. I suppose I could get it lower by purchasing an XLR DAC but for the moment I’m sticking.
MRC01
Major Contributor
Most active preamps have more than unity gain at max volume. So the "amp" in "preamp" seems appropriate.
That's before we even talk about phono head amps, which typically have 30 to 60 dB of gain!
That said, most listening on typical headphones or speaker systems is attenuated something like 16 to 32 dB from full scale. So how the preamp performs at these low output levels that we actually use, seems more important than its performance at full scale / max volume. I believe comparing a preamp's SINAD at max volume vs. 50 mV output says a lot about how well engineered and built it is.
[QUOTE = "CharlesC, post: 310369, member: 11534"] Tengo una D50S que se convirtió en un par de NC250MP a aproximadamente -20db a -30db. No sabía que era un problema. Supongo que podría bajarlo comprando un DAC XLR, pero por el momento me estoy quedando. [/ CITA
It's what I thought. It is also worth buying a d70 topping and spending money on it and not spending it on a pre amp. No?
I find it strange the difference so big when I had the pre rotel so I asked. thanks
It's what I thought. It is also worth buying a d70 topping and spending money on it and not spending it on a pre amp. No?
I find it strange the difference so big when I had the pre rotel so I asked. thanks
When I read the heading I thought you might go down the route of how much time preamps are actually acting as amps rather than attenuators (given line level DAC inputs). Seems like most of it IMO, except perhaps in those low power tube systems.
In theory, digital attenuators on DACs could be problematic, if the DAC isn’t oversampling first. And it seems to me of the output impedance is ill-matched to the amp, we have a design or execution flaw at one end or the other. No?
In theory, digital attenuators on DACs could be problematic, if the DAC isn’t oversampling first. And it seems to me of the output impedance is ill-matched to the amp, we have a design or execution flaw at one end or the other. No?
The miniDSP SHD & NAD C 658 are two preamp/streamer/dac units.
