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Thread: Can a pre-amp make a power amp sound better?

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    Default Can a pre-amp make a power amp sound better?

    I don't normally bother with pre-amps as I have just one input source (digital steam) and I can control volume digitally; I don't need tone controls.

    Am I missing out on something good sound wise?
    Last edited by Mandryka; May-17-2019 at 15:57.

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    Senior Member philoctetes's Avatar
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    Mandryka, I have two systems - small and medium size - that I added tube pre-amps to last year, and the difference is subtle but worth the investment. I especially hear the difference in the higher-quality system.

    Tubes get their distinct sound by altering pure sine waves which creates the harmonics we hear. I think of it as an electronic effect that mimics the acoustical effects of a live performance space. So the sound has a slightly more "broadband" characteristic which is less piercing to the ears and reduces listening fatigue, At least that's my theory and my ears like what they hear.
    Last edited by philoctetes; May-17-2019 at 16:05.

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    I suppose it could make it sound worse, if it's a lousy preamp. But there's nothing special about isolating preamp circuitry in its own separate box. There was an advantage in the old tube amp days. It was a good idea to separate an amp that ran as hot as a toaster oven from the rest of the system. Or you could replace a funky power amp without having to buy a whole new front end. Or swap in a preamp with more inputs without having to buy the power stage all over again. But today, electronics are dependable, clean and inexpensive and they run much cooler, so there isn't any advantage to that any more.

    It's become an object of fetish for audiophiles to split their system into as many black boxes connected by fancy wires as possible. But none of that has any impact on sound fidelity.

    The best way to choose amps is for real features... Does it support HDMI? Multichannel? Various digital audio codecs? Streaming? ...all those things are much more important than whether the amp is split into two boxes instead of just one. If you can find one box that does everything you want, buy it. If you need specialized features that don't come all in one box, then consider going to separates. But not for sound quality, because there isn't any difference there.
    Last edited by bigshot; May-17-2019 at 17:59.
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    Quote Originally Posted by bigshot View Post
    I suppose it could make it sound worse, if it's a lousy preamp. But there's nothing special about isolating preamp circuitry in its own separate box. There was an advantage in the old tube amp days. It was a good idea to separate an amp that ran as hot as a toaster oven from the rest of the system. Or you could replace a funky power amp without having to buy a whole new front end. Or swap in a preamp with more inputs without having to buy the power stage all over again. But today, electronics are dependable, clean and inexpensive and they run much cooler, so there isn't any advantage to that any more.

    It's become an object of fetish for audiophiles to split their system into as many black boxes connected by fancy wires as possible. But none of that has any impact on sound fidelity.

    The best way to choose amps is for real features... Does it support HDMI? Multichannel? Various digital audio codecs? Streaming? ...all those things are much more important than whether the amp is split into two boxes instead of just one. If you can find one box that does everything you want, buy it. If you need specialized features that don't come all in one box, then consider going to separates. But not for sound quality, because there isn't any difference there.
    You've misunderstood my question I think. I wasn't asking whether a pre/power combination in separate enclosures could sound better than an integrated amp. I was asking whether adding a pre-amp into the chain could make a sonic improvement.

    I've set up a system a Krell KSA50 receiving a signal directly from a Theta DAC, all being played through Spendor SP1 speakers. Vert cheap interconnects and speaker wire. I'm wondering whether I have any reason to think that adding a preamp of some kind -- SS, valve, passive -- could be an interesting avenue to explore.

    A traditional answer would be that all an active preamp can do is distort the signal, possibly in a way that people like, that's what philoctets has experienced I guess. And with the Krell and Audio Research pre was a classic solution. But that was in the days when people had multiple sources; and personally I'm not hankering after the warmth that valves may bring.

    What I would be interested in is whether a preamp of some kind could improve imaging. I'd also be interested in whether using a preamp is a better way of controlling volume than digitally -- I mean better in the sense of preserving signal integrity.

    The system as is is fabulous by the way. It does run hot, so I have to remember to turn it off, that's the main downside. I love the brutal styling of the Krell.

    20190515-142858.jpg
    Last edited by Mandryka; May-17-2019 at 18:59.

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    I've never heard of a preamp that has euphonic distortion. The amplifier stage is usually where that comes in. If you're interested in exploring signal processing, the best way to do that is to use a computer source and employ DSPs (digital signal processing). Digital processing is more adjustable, clean and precise than brute force analog methods.

    There are thousands of different plugins that you can use to alter every aspect of the sound. You can get DSPs that simulate a wide variety of tube amps, others employ timing correction for room acoustics or to create ambiences, others alter the dynamics or response curve, and there are noise reduction and restoration DSPs too. The sky's the limit and it's fun to learn about sound by experimenting. You can get anything a recording studio would use pretty easily online.

    I've only scratched the surface of this subject myself, but there are some knowledgeable people who have posted in this thread. It's a good place to see what is possible. https://www.head-fi.org/threads/the-...thread.867258/

    A couple of general notes... One thing I've learned about imaging is that it is very dependent on room acoustics- speaker placement, sitting position and reflections off walls are all critical to creating a precise soundstage. For that, looking into how to optimize your listening space with treatment and moving furniture around might be most effective. I have a projection room with a large screen, so I used a combination of speaker placement and DSP to increase the size of the soundstage to match the size of the screen. But that's a pretty specialized thing. In a normal 2 channel home system, just getting your room in order should do the trick without the need for a DSP.

    As for volume pots... it's unlikely if your sources are putting out line level that digital attenuation is any sort of problem. Even if your source is putting out sound below line level, you should have plenty of room so you don't bump into the noise floor. Look into that if you are hearing noise at low levels.

    Signal integrity isn't really the focus if you are looking to do signal processing. By definition you are altering the sound. Hopefully, you're altering it in a good direction! That just takes trial and error.
    Last edited by bigshot; May-18-2019 at 00:51.
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    I would like to explore DSPs, I'm not sure how to do it and keep my current amps/input method.

    The guy who restored my Krell is an experienced amp technician. He hates active preamps. When he tried it in his workshop he said it was really outstanding with a passive pre with a 50K pot, and then he tried one with a 10K pot and it became amazing, one of the best amps he'd heard, as good as the two he likes the most -- the Musical Fidelity NuVista 300 and the Radford STA25 MkIII. So I'm very tempted to by a 10K passive pre to find out! But he never tried it with no pre (he doesn't think a digital volume control is safe.)

    I'm a bit sold on pure class A SS amps by the way, the Krell is indeed a fabulous thing. I am really stopping myself going for a NuVista 300 for sale here.
    Last edited by Mandryka; May-18-2019 at 09:54.

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    DSPs are for signal manipulation. They aren't about signal purity. But they can improve sound if you use them wisely. To do that, you'll need a computer to use as a source and rip music to it. Amps amplify. Most amps are clean enough to be audibly transparent. They don't really improve sound. At best they are "a wire with gain". It's not hard at all to achieve that.
    Last edited by bigshot; May-18-2019 at 17:06.
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    Quote Originally Posted by Mandryka View Post
    I don't normally bother with pre-amps as I have just one input source (digital steam) and I can control volume digitally; I don't need tone controls.

    Am I missing out on something good sound wise?
    My advice is to use your ears and decide for yourself whether a pre-amp results in better sound quality. (The assertion that “all amps sound the same” has been beaten to death in this forum. Suffice it to say that my experience is that different amps often sound different.)

    I sometimes use Oppo UDP-205 universal players (and the older BDP-105 and BDP-95) to directly drive tube power amps (i.e., no pre-amp). The Oppo UDP-205 can play every digital classical recording that I own, including Ultra HD Blu-ray, Blu-ray, Pure Audio Blu-ray, SACD, CD, and downloaded 24bit/192kHz FLAC files. The Oppo players effectively have "pre-amp" functionality built-in by virtue of their option for variable output (i.e., volume control on the remote control), and other features such as a crossover for a subwoofer, and the ability to use its internal DAC (dual 32-bit ESS Technology ES9038 PRO reference DACs) to process external digital audio signals via its three digital audio input ports: OPTICAL, COAXIAL and USB DAC. (My understanding is that the UDP-205 supports other formats that I don’t currently use, such as DSD downloads, and MQA files from connected USB hard drives and thumb drives, DLNA servers, and SMB shares.)

    I connect the Oppo’s analog audio outputs to my vintage tube amps (some power amps, some integrated amps), and I connect powered subwoofers to the Oppo’s line-level subwoofer output and employ the Oppo’s bass management functionality (i.e., configurable crossover). I use this configuration for Stereo (2.0 and 2.1), and multi-channel (5.1).

    The only problem I’ve encountered when directly connecting the Oppo to a power amp was when playing hi-res classical recordings via my single-ended-pentode (SEP) amp, sometimes there wasn’t enough gain. (Hi-res classical recordings usually have no compression, and during quiet passages have very low volume levels compared to pop recordings.) I’ve found that I can address the issue of inadequate gain when using my SEP amp by increasing the output level of my Oppo player by adjusting its “trim levels” for the l/r speakers. (Gain isn’t an issue with any of my other amps.)

    The only other situations where I introduce a preamp (e.g., McIntosh MX110Z tuner/preamp) are for a turntable, or if I need tone controls with a particular amp or recording. (For example, I generally find KT88s to be too bright sounding with my Klipsch speakers.)

    I have 5 hi-fi systems, and 23 tube amps, 4 SS amps, plus one Class D SS amp, 1 SS pre-amp, and 2 tube pre-amps, all in good working condition. (The tube amps have all been restored.) I’ve been involved in the hobby for more than 40 years, and many more amps have come and gone from my system. Based on my experience, my advice is this: Listen for yourself.

    I suggest seeing if you can borrow a pre-amp, or listen to other peoples’ systems. If you buy a collectible used component and it doesn’t suit your tastes, you can sell it and recoup your investment.

    There are many ways to enjoy the hobby – go with what works for you. That’s my 2 cents …
    Last edited by RobertKC; May-18-2019 at 17:17.

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    Quote Originally Posted by Mandryka View Post
    I don't normally bother with pre-amps as I have just one input source (digital steam) and I can control volume digitally; I don't need tone controls.

    Am I missing out on something good sound wise?
    Yes, you are.
    I have also tried the DAC as Pre amp route, and always found myself reinserting the pre amp

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    Quote Originally Posted by Triplets View Post
    Yes, you are.
    I have also tried the DAC as Pre amp route, and always found myself reinserting the pre amp
    Did you go back to active or passive preamps?

    Did you check that the output of the DAC was a good match for the input sensitivity of your power amp when you tried the direct route?

    I'd like to know some of the equipment you tried. And more about what you think you lost when you had no pre.
    Last edited by Mandryka; May-20-2019 at 14:51.

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    Assuming that the output of the DAC suits the sensitivity of the power amp, and assuming that digital volume control doesn't corrupt the signal in a significant way, there is no way that having a preamp, even a passive one, can be a good thing from a sound point of view. All the preamp can do is distort the signal on the recording. Some people like that distortion, but if you want truthful reproduction, preamps are the invention of the devil.

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    Hell must be walled off with acoustic tiling.

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    Quote Originally Posted by philoctetes View Post
    Hell must be walled off with acoustic tiling.
    Having just reread "The Inferno" - Nope. There's a rear port.

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