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  • PRESONUS ADL 600 (tube preamp)

    PreSonus ADL 600 – Prologue

    When I did a Pro Review of the Mackie Onyx 400F, I thought it wouldn't last more than a week or two…after all, what can you say about an audio interface for a computer?

    Well, it turned out there's a lot you can say about an audio interface. And in the case of this Pro Review of the PreSonus ADL 600 (a collaborative effort with Anthony DeMaria Labs), I suspect we'll have a lot to talk about as well. What makes a preamp worth $2,295.95? One of the purposes of this review is to find out if the price tag is justified, and if it is, what that buys you.

    But what’s also going to make things really interesting is that this is a preamp intended to have "character." It's not supposed to be a straight wire with gain, but a straight wire with attitude. That’s just begging for controversy right there, but the ADL pedigree says a lot, and PreSonus has gotten to where it is by picking and choosing its products carefully.

    Another point worth considering is that I've never been a "my slew rate can beat your slew rate," boutique kinda guy. I have my preferences, but if what comes out of a preamp is suitably close to what came in, I'm happy. So part of my interest in getting "up close and personal" with the ADL 600 is to find out exactly what a pricey puppy can do for my sound.

    As with other Pro Reviews, I see no point in restating material that's available elsewhere. If you want specs, a block diagram, applications, and the like, PreSonus has quite a complete "product landing page" for the ADL600 at http://www.presonus.com/adl600.html. You might want to swing by there for a bit and get some background before getting into the review. To see what the ADL 600 looks like, click on the attachment to view the front panel. To get an idea of what it feels like, get a bunch of telephone books and some bricks – it weighs in at a hefty 28 pounds.

    For those of you not familiar with how the Pro Review concept works, it's simple: This is a forum, so everyone's invited to participate in this "open source" review. If you have questions, comments, or concerns, step right up and voice them. As usual I’ve also invited PreSonus to participate, and I’m sure they’ll be more than happy to talk about the fine points of vacuum tube design, or whatever else strikes your fancy. Please note that this is a sponsored review; for details on what that means, click here for the Pro Review FAQ, as well as links to other Pro Reviews.

    Okay, that’s enough blather for now. Let’s open up the box, and get started.
    CHECK IT OUT: Lilianna!, my latest song, is now streamable from YouTube.

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  • #2
    The ADL 600 has rear panel XLR connectors for line in, mic in, and line out. Click on the attachment for a view of the rear panel. I would like to have seen a combo jack for the line ins so you could feed in 1/4" phone jacks without adapters; I assume PreSonus would say that XLR-only jacks are sturdier. I’ll ask when a company representative checks in.

    1/4" input phone jacks are on the front for instruments, along with a switch to select among the various ins (note the four different impedance options for the mic in; more on this later). While you can't mix different ins together, note that the two channels are completely independent so you could, for example, use one channel for mic and one for guitar. Speaking of guitar, the input impedance for the instrument input is 100kohms; I would prefer to see that doubled to avoid any chance of loading with passive, single-coil guitar pickups. However, 100k is considered an acceptable value for high-impedance guitar inputs, as evidenced by the many effects that use this value.

    On the right channel, the +48V phantom power switch (and it really is +48V) is located between the Power and Polarity switches. This makes unlikely that you’d hit it by accident, as you won't be flipping these other switches much. For the left channel, the phantom power switch is located between the instrument input and polarity switch - again, the odds of hitting it accidentally are remote.

    There are also filters, gain controls, and so on, but we'll get into those as we delve into real-world applications. In fact, as one of the ideas behind a Pro Review is to evaluate a product in context, I'd like to speak a bit about that context.

    One of the reasons I'm starting the Pro Review now is because I have several NAMM videos to complete for the HC NAMM report. I’m doing these last because they all require narration, so it seems like a perfect chance to put the ADL 600 through its paces. I'm also working on some library music, which requires guitar, synth, and drum machine parts. This gives a good chance to check out the instrument preamp, as well as what kind of "character" the line ins add to various electronic instruments.

    I'll also be doing some miking with the ADL 600 at Maricam studios in Santa Fe, which specializes in recording classical and acoustic music, as well as recording some percussion and other sounds in my own studio. Finally, I'll use the ADL 600 in mastering applications to see if there's any real advantage to adding a "tube sound" to certain types of material.

    Along the way I'll comment on the build quality, ease of use, documentation, and whatever else seems worthy of note – or more importantly, whatever you ask about! Meanwhile, it's getting late…rather than start doing narration now when my voice is shot, we'll revisit this in the morning. See you tomorrow.
    CHECK IT OUT: Lilianna!, my latest song, is now streamable from YouTube.

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    • #3
      i'm glad you did this review, since i've been a lover of PreSonus for years and when they came out with (correct me if i'm wrong here) their first BIG TICKET item, i was curious to see how good it was going to be. i currently record with a PreSonus Firepod and i love it, but my preamp is an Avalon 737. (amazing) how would you say it holds up in comparison?
      gschmitt - singer/songwriter/producer

      - The Official gschmitt Website
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      Thanks for your support. Really.

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      • #4
        Well the Avalon stuff is great, but I don't have one here for a direct comparison. I'm going to be dealing with the ADL 600 on its own merits, and try to describe what it does as accurately as possible...hopefully that will be enough that you'll know what to expect, and how it differs from other units out there.

        I will say my initial impressions are very favorable...three tubes, high voltage, and an output transformer (a very important element IMHO) do make a difference.
        CHECK IT OUT: Lilianna!, my latest song, is now streamable from YouTube.

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        • #5
          Craig,

          I am so glad to see you reviewing this fine preamp. I just got one a week or so ago and am taking it through its paces during some tracking sessions and have been amazed so far by the results.

          While every preamp has its own sonic "fingerprint", the ADL 600 has really blown me away so far.

          Looking foward to experiencing this unit along with you.

          Neil

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          • #6
            Okay, testing time. I’d written the script for the IK Multimedia video, and it was time for narration. I chose a Shure SM58 dynamic mic because I know it better than any other, and plugged it into the ADL 600 input. I plugged the output into my Panasonic DA7 mixer, which has quality preamps that I thought would provide a good standard of comparison – again, I know them well. I didn’t have an A-B switch per se, so I dedicated one input to the ADL 600 out, and another to the straight mic in, and spent a lot of time patching between the two of them for comparison.

            Click on the attachment to see a close-up of the controls we’re about to cover.

            There’s a “master” gain control with eight stepped settings in 5dB increments, from 35 to 65dB of gain. I was pleasantly surprised that turning it didn’t produce any pops. An additional Trim control alters the gain plus or minus 10dB. I was also pleasantly surprised by the lack of noise; I expect some degree of hiss out of tubes (especially three of them), but the ADL 600 seemed quieter than average.

            As the input switch has four choices of impedance, I figured I’d explore that first. Choices are 150, 300, 900, and 1500 Ohms. There’s no “right” setting; it depends on which you like best. The most dramatic difference was between the 150 Ohm setting and everything else: It had slightly less output and low end. This isn’t necessarily a bad thing – if you’re close-miking and doing the proximity effect thang, this might be the best option. However, I was keeping the mic several inches from my mouth, and wanted more of an intimate, “FM DJ” sound. I was drawn to the 1500 Ohm setting, which gave a really full, round bottom. But after a while it seemed a little exaggerated, so I dialed in the 900 Ohm setting and it seemed perfect for the task at hand.

            The best way I found to test out the positions was to sing a constant, fairly low note and turn the input knob. The difference among positions is subtle – any changes don’t hit you over the head – but I can’t imagine anyone not being able to discern a difference.

            The input knob was a little loose, but the ADL 600 comes with a Allen wrench for the knob setscrews, so I tightened it up. (It makes me wonder if they loosened that knob on purpose just before shipping so I’d appreciate the inclusion of the Allen wrench!)

            Having gotten the low end the way I wanted, I started to mess with the HP filter. There’s a switch to bypass it, and a three-position frequency switch: 40, 80, and 120Hz. The response is gentle (the specs quote response as being 12dB down at the selected frequency) so if you have some serious low end problems, you’ll likely need to take care of that in your host, or with a different processor. It’s definitely not a digital brickwall filter. Having said that, though, it’s effective. Engaging a response drop at 40Hz “tightened” the vocal sound, while the 120Hz position definitely started affecting the vocal range. Hmmm…so what happens if you use the HP filter and the input selector together?
            CHECK IT OUT: Lilianna!, my latest song, is now streamable from YouTube.

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            • #7
              Hey Neal, welcome aboard. One advantage of Pro Reviews is they get people to post who otherwise just lurk

              However, you're not getting off that easy! Could you let us know a bit about how you're using it -- what are you miking, where do you think it works best, what exactly about it blows you away -- that sort of thing. The more opinions are expressed here, the more effective and helpful the review.
              CHECK IT OUT: Lilianna!, my latest song, is now streamable from YouTube.

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              • #8
                As I said at the outset, I’m not a boutique kinda guy. But I am a tweaker and a perfectionist, so I couldn’t resist seeing how the HP filter and input impedance selector interact. And actually, they do interact quite a bit, thus allowing more tailoring of the mic sound than either option allows by itself.

                I need to emphasize that again, these are subtle differences. For example, popping in the 80Hz filter with the 1500Ohm position tamed the low end compared to just using the 1500Ohm setting by itself, but the sound was different compared to just the 900 or 300Ohm settings, which also tamed the low end – but in a different way.

                At this point, it would be logical to say “But why don’t you just use EQ in your host program to dial in the changes you like?” And yes, you could create a similar effect solely with EQ. But again, there are subtleties to consider. Of course, a passive filter sounds different compared to a digital filter. But perhaps of greater importance is that your choices are limited and repeatable. In other words, if you find that a particular input impedance and filter setting works well with a particular mic for narration, well, it’s easy to dial in the next time. Of course you can save presets with plug-ins, but there’s always an immediacy about flicking a switch.

                Another point is that by making these changes in the “front end,” you’re influencing the recording process. Cutting out bass rumble before hitting your recorder means you can get more level into the input, as opposed to recording a signal with rumble and then trying to get rid of the rumble at a later time, like while mixing. It’s also worth considering that the interaction between mic and input with respect to impedance is a complex one with many variables; I think it will be quite some time before we see an “impedance matching modeler” plug-in. Yet this does make a significant difference to the overall sound.

                I was a little surprised to find myself paying such close attention to these minutiae, but hey, they’re built in to the unit and I’m doing a Pro Review, so I gotta check it all out. You can definitely get hung up seeing how close you can dial the sound in to perfection, but frankly, the results were worth it. I felt I found a combination of settings that provided a good match for the mic, and flattered my voice.

                Now it’s time to concentrate on trying to define the ADL 600’s “character,” because it does have one.
                CHECK IT OUT: Lilianna!, my latest song, is now streamable from YouTube.

                Subscribe, like, and share the links!

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                • #9
                  So how does it compare to using the plain, yet very competent, DA7 preamps? Unfortunately attachments with this forum software are limited to slightly over 100k, which precludes providing WAV or AIFF samples of any reasonable length. But actually, it’s not too hard to describe the difference.

                  The most noticeable difference is that the high end has a bit of a “sparkle.” It’s a certain clarity that isn’t strident or bright, but does add definition. I’m not sure what specific aspect of the circuitry accounts for this (any PreSonus people out there who can answer this?), but I think that using a higher impedance setting at the input selector might account for at least part of the clarity. As a dynamic mic is an inductor, and high frequencies are loaded down more by lower impedances than lower frequencies, this doesn’t seem like an unreasonable assumption.

                  The next most noticeable difference is a slight sort of compression. Yeah, I’m going to use the term “subtle” again. I can’t tell if this is solely an amplitude-related phenomenon, or if perhaps there’s a very slight bit of overdrive short of distortion; in any event, I felt it added a bit more intimacy to my voice.

                  Another slight difference is a sort of “creaminess” or “thickness” in the midrange. I’ve often heard this effect in gear with quality output transformers, so presumably that’s the factor at play here; the ADL 600 has an output transformer driven by a tube output stage. Another interesting aspect is that the vocal sound through the ADL 600 is (and I hate to use this word) is more organic-sounding. The DA7 preamps sound accurate, but the ADL 600 kind of coats the signal with a certain veneer of richness.

                  Just to see if this was psychological, I recorded a little bit of vocals through the ADL 600 and through the DA7 pres. On playback, there was a definite difference. Although I couldn’t exactly do a double-blind test, nor could I maintain a totally consistent vocal quality at exactly the same level, I think that given a sufficiently consistent vocal sample of sufficient length, it would be easy to identify the two preamps in a listening test.

                  Bottom line is that I feel my narration vocal quality was considerably improved compared to the DA7 pres; as a “real world” reality test I also tried the preamps in the Digidesign Mbox2 and PreSonus FireBox. Again, there was a definite difference when using the ADL 600; the sound was rounder, more defined, and more intimate.

                  It will be interesting to see if these differences hold up after the video goes through the mixing and encoding process. There are two NAMM videos posted on this site using other preamps, so I’ll be able to compare them to the newer videos that use the ADL 600. My initial reaction is that the degradation in quality caused by the data compression process will mask any differences, but we’ll see.

                  It’s dinner time now, and I doubt I’ll get the video finished tonight…but I might. In any event, when I do, I’ll move on to the next part of this Pro Review: The instrument input. If this holds up next to my big-bucks Class A DI box by Radial Engineering, I’ll be pretty impressed.
                  CHECK IT OUT: Lilianna!, my latest song, is now streamable from YouTube.

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                  • #10
                    Hey Craig, I was present at one of the shootouts the studio next door to us was doing to write their upcoming ADL600 review in EQ Magazine. I also have a fair amount of time using the pre myself, and I'm curious to see your findings!

                    War
                    Warren Dent | Owner | www.ZenProAudio.com

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                    • #11
                      This is great timing... I just got my ADL 600 last week and started some recording tests this weekend. I agree with your assessment of the "creaminess". That was how I described the sound of my violin and acoustic guitar recorded thru Earthworks TC-20 omnis. When I record through these direct to the FF800, the sound is very clean and detailed, but without added character, which is fine in some cases. However I got this unit to counteract the impression some clients have of digital being too sterile. Actually I think that some people can't stand the actual sound of their instruments, but that is another debate.....

                      In any case I was amazed at the difference in sound, definitely a richer sound, like the difference between black coffee and a mocha latte!

                      OK, now I need to go back and try some other mics and the direct input. I have a collection of decent but lower end condensors, Marshall and Octava, which I am hoping this unit will make even better sounding. My fav mic is the Marshall V69 tube, so it will be interesting to see if the ADL 600 improves that already great sound.

                      Thanks for starting this thread, Craig, I was really looking for some seasoned input on this unit, after dropping $1800 (Sweetwater B-Stock, great deal!). I am looking forward to hearing more of your opinion.
                      -- Barn Jazz - music from the transition zone --

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                      • #12
                        <<I also have a fair amount of time using the pre myself...>>

                        So, whaddya think? How do you use it? And tips or tricks?
                        CHECK IT OUT: Lilianna!, my latest song, is now streamable from YouTube.

                        Subscribe, like, and share the links!

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                        • #13
                          I'm certainly not in the market for any big ticket pres at the moment, but I thought I'd drop in to say that Anthony DeMaria is an old friend of mine from grade school, that he still lives around the corner from me, that his nickname is D-Mo, and that he's a really good guy who loves his work...so, uh, buy this unit!

                          I do have some experience with his gear. He left a prootype of his single channel comrpessor in my wee little composing studio for the better part of two years, even though he knew its price was way out of proportion with the economics of my studio.

                          ...But in the 8th grade one-on-one basketball tournament, D-Mo beat me in the finals when the gym teachersrefused to call him for clearing me out, again and again, with his left arm as he drove to the basket...

                          carry on

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                          • #14
                            Interesting side comment! I must say the unit has the "vibe" of someone who was designing the unit for himself, not for a focus group. There's a lot of "spare no expense" stuff going on, like the component quality, that probably wouldn't make it through a team of accountants but easily passes muster with engineers.

                            I don't know how much I'll get done today, I haven't had the chance to try anything new...still doing narration. But the one thing I will say is that my initial impressions are holding up.
                            CHECK IT OUT: Lilianna!, my latest song, is now streamable from YouTube.

                            Subscribe, like, and share the links!

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                            • #15
                              Originally posted by Anderton
                              <<I also have a fair amount of time using the pre myself...>>

                              So, whaddya think? How do you use it? And tips or tricks?


                              It's HUGE sounding is my main thought when using this preamp. It's not just the low end that sounds large and extended, it has a big presence to it from top to bottom. It's also very quiet, as quiet as most solid state stuff really. Another standout feature of this tube pre is the detail, there is great detail going on that is not normally associated with tube equipment and transformer in and out preamps.

                              As an example, when used on overheads against several other high end preamps (KM100 mono setup) the ADL600 was the only preamp where a kick mic might have been optional. The low end was just there, pulled to the surface and present. On kick drum it was insane how much of EVERYTHING it delivered top to bottom, and I've talked to several other guys who are now using it as the go to kick pre.

                              My only tip thus far would be to use the ADL600 when you need a huge track like vocals, kick, maybe a featured guitar etc. When mixing it's impossible to make everything sound large so for guys with multiple preamp setups this preamp will come in quite handy for featured tracks that need that size.

                              War
                              Warren Dent | Owner | www.ZenProAudio.com

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