One of the best upgrades you can make to your studio is to get a nice outboard preamp. But it can be hard to bite the bullet. After all, you’ve got preamps built into your audio interface, right? They sound fine, so why would you upgrade them?

Well, for one thing, you don’t know what you’re missing. Imagine that you grew up without access to computers, and someone showed you a 20-year-old IBM PC running DOS, you’d think it was amazing, right? You’d have no reason to think there could be anything better, but that doesn’t mean that better computers don’t exist. (Now imagine yourself fainting at the site of an iPad.) 🙂

The point is this – just because you’re happy with the stock preamps on your interface doesn’t mean your sound can’t be dramatically improved by investing in an outboard preamp.

I must preface this review with two things:

  1. Don’t succumb to Gear Acquisition Syndrome. Buying gear for the sake of gear is no bueno. However, if you’re in a position where you’re ready to upgrade, read on.
  2. The good folks at Presonus sent me this Eureka for free in exchange for a review. That said, I only do this with items I truly believe in. (I’ve turned down similar offers from other manufacturers.)

The Presonus Eureka

The Eureka is a sweet little channel strip. I used one several years ago (before I ever started HSC), and I LOVED it. Here’s why:

  • Transformer Coupled Preamp
  • On-board Compressor & EQ
  • Impedance Selector
  • Saturation Knob
  • VU Meter
  • Master Volume
  • The Price

Transformer Coupled Preamp

Rather than go into the technical jargon of why this is cool, I’ll just give you the brief version.

There are basically three types of preamps: tube preamps, transformer preamps, and preamps with fully discrete circuits (no transformer or tube). Typically the fully discrete preamps have a very clean sound, while transformer and tube preamps add some “color” to the audio.

The Eureka has a transformer in it. At $500 (at the time of writing this), that’s awesome. Even if there were no other features on this unit, it would still be worth the money. Having that transformer simply takes the audio to another level.

It doesn’t sound like a cheap preamp. It has a very open sound. When I compare it to the preamps on my 003, I notice that the signal simply sounds more professional. It has more depth to it. The frequency response goes higher and deeper, and there’s much more detail.

You can thank Mr. Transformer Coupled Preamp for that.

On-Board Compressor and EQ

While the preamp sounds amazing by itself, the onboard compressor and EQ sound great, too. If I had to choose one word to describe them, it would be clean. There’s nothing over-the-top about the two.

The compressor gives you plenty of control over the sound without adding a lot of coloration. It has controls for Threshold, Ratio, Gain, Attack, Release, and Side-Chain High-Pass Filter. There’s also a selector for “Soft” compression (meaning a softer knee setting).

I’ve used this compressor on vocals and bass a lot, and it clamps down on them nicely. Since it’s so transparent, I can compress a signal by 10 dB and it doesn’t sound obvious at all. Great-sounding compressor.

If you’re wanting a really aggressive compressor that adds all sorts of harmonic distortion (like a Distressor), this isn’t going to make you happy. But if you want something subtle and clean, you’re in good shape.

The 3-band EQ is equally cool. It’s a legitimate 3-band EQ, meaning it gives you Frequency, Gain, and Q (width) controls for each band. You can also switch the high and low bands from shelving filters to normal bell curves. [UPDATE: This is wrong. Sorry! You can adjust the width (Q) of each of the three bands, but you can’t switch the high and low bands from bell to shelving.] Very versatile.

The EQ, like the compressor, sounds very clean and subtle. If you’re wanting something agressive and obvious, you won’t get it here. But if you want to cut a few annoying frequencies while tracking, and have everything sound natural, this will do it wonderfully.

Also, the Eureka allows you to select which comes first, the compressor or the EQ, which is very useful. (I usually like to have the EQ first, FYI.)

Impedance Selector

Most microphone preamps have a set impedance, meaning a set electrical resistance to the incoming signal. For condenser mics, this usually isn’t much of an issue, but when you start using dynamic or ribbon mics with low-level outputs, being able to change the preamp’s impedance can be a life-saver.

By adjusting the preamp’s impedance, you’re essentially adjusting how “hot” the mic is. This allows you to have plenty of gain without needing to max out the pre (which is never a great option).

I won’t go into the details of what an impedance selector does. Suffice it to say you can make your microphone sound very different depending on where you set the impedance…a nice way to get more sounds out of your existing mic collection.

Saturation Knob

Want a dirtier sound? Want the pre to sound less clean and more like a tube preamp? Reach for the saturation knob. This essentially adds harmonic distortion to the signal. While nothing can make a solid-state preamp sound just like a tube preamp, the saturation knob can give you an extra level of tone for your recordings.

For example, sometimes my vocal recordings sound a bit too bright through the Eureka. I simply increase the saturation a bit, and it “warms things up” without making them sound muddy or indistinct.

VU Meter

No studio is complete without at least one VU meter. The one on the Eureka is FANTASTIC. It’s very bright, and it’s actually usable. (Some preamps have VU meters, but they’re not really helpful.)

You have the option to monitor the output gain or the amount of gain reduction at the compressor.

Master Volume

Gain-staging on a channel strip can be difficult at times. You spend 10 minutes dialing in the perfect EQ and compressor settings, then you realize that you’re clipping your input into Pro Tools.

If you turn the preamp down, then you’re changing how much signal is hitting the compressor, which changes how much compression is occurring, thereby changing the actual tone of the audio. The Eureka gives you a master volume knob that acts a lot like a fader in Pro Tools. It’s a final gain stage, so you can trim up or down the signal without having to re-tweak the preamp, compressor, and EQ.

The Eureka gives you a whopping 74 dB of gain (54 dB at the preamp, 10 dB at the compressor, and 10 dB at the master volume), which is perfect for any type of microphone you can throw at it. (No more maxing out the pre on your interface when you’re trying to use a dynamic mic.)

The Price

This bears repeating. As I’m writing this article, the Eureka is selling for $499.95 over at Sweetwater. It’s one of those no-brainer preamp deals. I’ve heard several engineers tell me that they like the Eureka as much as preamps that cost two to four times as much money.

The Cons

No review is complete without looking at both the good and the bad. Here are a few things that I don’t like about the Eureka:

  • Rear Power Switch – The power switch for the unit is on the back, so if you’re using an equipment rack like I am, it’s not easy to turn it off. I like to have that option with my preamps.
  • Input Gain – The only readout you have on your input gain is a 3-stage LED. It would be nice to have the option of seeing the input gain on the VU meter, but you can’t.
  • Fairly Bright – The first time I used the Eureka, I thought it sounded a bit bright. I think it was because my previous preamp didn’t capture the high frequencies as well. Either way, sometimes the vocals I’ve recorded can be a bit harsh. The more I worked with it, the more I was able to dial in a good tone, but that’s something to keep in mind.
  • No Saturation on Line Inputs – It would be nice to be able to run a line-level signal through the saturation section to see what that sounds like, but the saturation is only applied to microphone and guitar inputs.


All in all I think the Eureka is a fantastic piece of equipment. If you were to only buy one preamp, this would be an excellent option. It gives you a large variety of tones without sacrificing quality. Plus it can be extremely beneficial in helping you learn how to use EQ and compression properly.

For more information, head over to the Presonus Website.

What do you think? Leave a comment and let us know!

  • Great review Joe! Thanks for that!

    • By the way, different topic, but have you read “Mixing With Your Mind” by Michael Stavrou?

  • Brandon

    How do you cange the eq’s on the Eureka between shelf and bell? I see you mentioned that you can in the artical.

    • YEah, I own a Eureka, but I don’t see the shelf/bell option. Which setting changes it?

      • I don’t see where I mentioned that in the article. ??

      • Ah I see it. Sorry, that was wrong. Corrected.

  • LKDolbear

    It seems I’m 3 years late to the party on this one but I recently got the Eureka and I’m having a problem with vocals. They seem to have a robotic type sound in places, almost like Cher with the old autotune which is really not the sound that I’m going for! I’ve tried the recommended settings in the manual and different mics (I mainly use a Blue Blueberry) but it still happens. This is the first time I’ve used a channel strip. Any advice as to what it might be would be much, much appreciated.

    • LK- the “Cher” effect you describe – called “quantizing” – is a digital effect. The Eureka is a fully analog preamp, and cannot do that sort of thing, so I’m not sure what could be happening other than something you have set up in your recording software.

      • LKDolbear

        Hi Terry, thanks for the reply. Yeah, that’s what I thought too but it’s there when there are no plugins in use at all. It’s not quite as extreme as Cher but just a very annoying sound on certain words. Hopefully, I’ll figure it out.

      • It’s not technically quantizing. It’s AutoTune.

  • This article explains pretty well why setting the Impedance control “all the way to the left” as Joe did in the podcast works so well, even if the microphone’s stated spec for output impedance is quite a bit lower!

  • James

    Hello im recently starting up my own home studio and i’m thinking about getting one of these coupled with the bluebird mic. Do these work well with a pc? My pcs relatively old and i’m wondering if it will work well with the product.

    Also for those that own the product, is there anything us “potential” buyers should know? Thanks for the help

    • They Eureka is a preamp, not an audio interface. It doesn’t connect directly to your PC. It connects to your audio interface.

  • Rich-p

    Loving my Eureka here. I also own a UA Solo 610 and Focusrite ISA One. All of these are great pres and the Eureka is certainly comparable as a preamp. The fact that you get a compressor, EQ and adjustable saturation aswell makes it a bargain!

  • Pingback: Presonus eureka | Writergoddess()

  • Just came and read, this is wow! I was seek from many blogs, but here is the best, I love it.

  • Robert

    Hi, I recently upgraded my soundcard to the RME Fireface UC. The two built in preamps sound really good and clean to my ears… would I still benefit from getting an outboard preamp? I mean, would it be a noticable quality upgrade or just a different coloring of the sound?

    • Every preamp sounds different. Are you unhappy with your current preamps? That’s really the question here.

      • Robert

        I am very happy with my current preamps. But with that said, I haven’t tried a quality outboard preamp for my setup… Do you think my rme built in preamps can compare to an outboard? I’m not sure if I’m missing out on something much better.

        • tim

          honestly the sound of this pre amp makes so much difference, get it and i garuantee youll love it, i could never get vocals to sound just right there would always be something i didnt quite like, bought this and i couldnt stop praising it everything i record pretty uch runs through one

          • And it’s so versatile…You can get a lot of sounds out of it.

  • rich

    I have been looking at this piece of year for a while and your review is consistent with others I have read. What I am wondering is if it has different preamps and a different eq, compressor etc than my StudioLive. Maybe that’s a question for Presonus, but I wonder if they are different by much.

  • Hi there

    I appreciate your review. I hope it’s not biased by the fact that you received one.

    I am considering buying a LA-610 MkII Classic, which costs around 3 times the price of the Eureka. but on the other hand, the Eureka would save some cash for a better microphone.

    Is Universal audio 3 times better than the Eureka? I know it’s a hard question…

    • I’ve used the UA. It sounds fantastic, but it’s a very different sound from the Eureka. It really depends on what sound you’re going for.

  • I must respectfully remind the readers that I have not heard the eureka, so what counts in the end is how it sounds. I think I was too strong in voicing an opinion before actually listening to the Pre.

  • I had a presonus studio channel before I upgraded to the focusrite ISA one. I had an eq on the studio channel as well as a compressor. I upgraded the cheap Chinese 12ax7 , which smoothed out the sound.
    Everything worked, and worked well. BUT, there was NO MOJO. It was not a true tube pre, just a ‘starved plate’ design.
    It’s the ‘that’ factor. It’s no always the case, but with audio gear it happens most of the time. I don’t know if many of the components of the studio channel are the same as the Eureka, but I would guess that they are.
    The ISA ONE is has no tubes, is based on a NEVE design; and boy, does it sound like it. The best way I would describe it is open, 3-dimensional, with a slight sizzle. It has no eq. It has no compressor. And, I would NEVER trade or sell it. It is that good. It really stands along side with the most some of the best pres.For the same price point as the Eureka, it is a no brainer for me.

    • The Eureka is completely different from the Studio Channel. The preamp, the compressor, and the EQ are totally different, FYI.

  • Hi Joe, loved your review. I just recently bought a eureka b stock from AMS for $300. Worth every penny and then some. I already had the focusrite trakmaster and twintrak. Both nice preamps, but the eureka was definitly an upgrade. I also have the ART MPA Pro II, Aphex 107, Studio Projects VTB1, and a couple of others. Presonus is the best of the bunch. Its sound is crisp clear and just what we are all looking for. Thanks for your postings. Love your work and your insight. Brian

  • Matt

    In my experience I have found that the right preamp does make all the difference, even with a cheap mic. It won’t make a bad mic sound amazing, but it does do a LOT. I remember the first time I got a good preamp – got amazing results out of some really not good mics. Now I have much better mics and can absolutely hear the difference. If you are trying to prioritize, I’d definitely advocate for buying a dedicated good preamp, like the Eureka, before sinking the cash on the mic. If you can afford it, just do them both at the same time!

  • Davor

    Nice review! I have an SPL tube preamp (that isn’t channel strip) and wondering what is the real need for averige home studio owner to have an hardware EQ and comp. when you have control and live room all in same room? It is difficult to adjust your output tracking sound with your headphones. I did considered of getting this Presonus preamp (it’s so pretty) and think it’s a “good bang for the buck”.

  • I also wanted to add that I did an easy mod to my Eurekas that improved the sound even more. I changed out the op-amps for less than $20 and the difference is night and day.
    No soldering involved. Just replaced them.

    • Hey phillip, was wondering where you got the op-amps and if you had part numbers or any other info that would make ordering easier. thanks Brian

      • Hi Brian, here is the website for the op-amps and the parts number. You will need to order 2 of these.

        part: LT1357CN8#PBF-ND

        • Hey Phillip, thanks for the fast reply. Ordered 2 this AM. Appreciate your help. Brian

          • For anyone who stumbles across this – indeed, this op-amp addition will improve the sound… so says Chad himself some few years ago:

            “Hi there. Thanks for interest in the Eureka and in modifying… The
            Eureka ships with a pretty good transformer, our own model, and TI
            (Texas Instruments) op-amps, which are pretty much industry standard and
            fairly quiet and transparent. Though it’s based on the same preamp
            circuit as our VXP, MP20, and M80, I would characterize it as being
            slightly brighter, perhaps. I never thought of it as edgy, but that may
            be a fair description. I think it’s slightly brighter because the normal
            impedence setting (2500) for the Eureka is slightly higher than the
            open impedance of the transformer, which provides the input imdepance
            for the older models, as they don’t have the added impedance selector
            circuit. I could be wrong, but I suspected that’s what accounts for the
            slightly different sound. Because the impedance is set before the mic
            hits the transformer, the transformer mod is a bit more subtle/harder to
            hear on the Eureka than in our older units. It’s also significantly
            more difficult to disassemble than our older models. For that reason, I
            usually suggest that people pass on transformer-modding the Eureka. Of
            course, if you really want to, you can. The only 2 direct-replacement
            drop-in alternatives that exist are the Audisar Plus-8 and the Jensen
            JT-11K8-APC. Both are very fine parts. Email me for info if you need to
            know how to obtain these. PreSonus doesn’t carry upgrade components, but
            I don’t have a problem in pointing people in the right direction. I’m a
            tweaker/mod guy myself, so I can definitely understand the urge to
            improve stuff.

            What’s alot easier to do is to replace the op-amp chips and there are
            several on the market. The most popular is the Burr Brown BB-OPA627. Our
            stock chip is actually among the quieter ones available, and so though
            you’ll sacrifice a few db in noise performance by taking ours out, most
            people claim the BB part is ‘bigger, beefier, better heft on the bottom
            end’, etc.. Second most popular is the Analog Devices AD-797AN, which
            sonically, people say is pretty much like our stock part but just
            performs a bit better. Faster transient response, greater clarity,
            clearer image, better attack, better detail, etc. … but I am talking
            subtleties. Another chip option is the Linear Technologies 1357 (Digi-Key full part number: LT-1357CN8-ND).
            This chip is possibly the most quiet one on the market, super noise and
            distortion performance. It’s actually also one of the most affordable.
            Only $4.63 each from Digi-Key. This is the piece I use myself, so I can
            capture the cleanest, most accurate sound and then give it color later
            if I choose to. If you want surgical accuracy, this is the way to go. If
            you want added warmth/bottom, the BB part is the way to go. The TI and
            AD lie somewhere in the middle. I hope this info is useful, have fun!

            Chad Kelly

            PreSonus Audio”

            Found on gearslutz forum. Google “mod to eureka preamp opamp” for more.

            Post reference:

            Just ordered two of them myself – USPS First Class mail about 3 bucks shipping. Two units totaled $9.38, so with shipping well under $15.

  • rick garcia texas

    hey Joe, that really open my eyes
    i thinking of getting one


  • I’VE used the EUREKA for a few yrs. now and think it’s amazing, for anything. You forgot to mention the send & return on back. Try this with your GTR., WHATEVER,Plugged into the inst. IN & RUN A PEDAL OR A POD,whatever thru the S&R and wow! My biggest con is that whoever designed the numbering around the pots should be shot-[ er, at least spanked hard]; Besides needing an eagle’s eye you also need to be somewhat of an contortunist!You also need to be aware of engaging the line button or not depending what you’re running thru it. All n’ all the sound is supreme and it is a class A for 500 which is unreal.Plus their support is slow but HONEST as you get a life-time free of maintenance . They have already re-placed my whole board once with no hassle.
    Take Care,
    TOMMY… /

  • angel

    Excuse me Joe, but the best piece of gear in your setup is that beautiful newborn baby of yours. Congratulations.

    My wife and I are expecting a baby girl for next march.

  • rick

    Great review, Joe!

  • I own 2 Eurekas.

    That says it all.


  • Christopher w

    that thing looks gorgeous. and hey I don’t mind if any companies send me stuff for free in exchange for a review *wink, wink, nudge, nudge*

    I don’t know why but I don’t find outboard EQ’s that necessary, it seems like its thrown onto everything just because it can be.

  • Paras Pradhan

    What about using this with external effects processors like Boss Me 70 to do rock/metal instrumental suffs?


  • Nice review…I always perceived Presonus stuff as ‘cheaper crap’ but a friend of mine just tracked his band with Presonus stuff and it sound really good…looking through your review it looks a lot like the kind of Channel strip I really want! Definitely going to check one out when I get round to pre-amp shopping (but not just yet…acoustic treatment, prioritising etc…)

    Am I right in assuming you used this on vocals for your album?

    • ACTUALLY…I got this right after I was finished with vocals for my album. They were done through my Trakmaster. Song #10 was done through a Universal Audio LA-610.

  • David Ellis

    Thanks Joe. I second that a shoot out would be awesome!

  • David Ellis

    Great review. I’ve been looking for something like this for a while. How did you connect this to your 003? Was it XLR, TRS or did you go for the digital output option?

    • No digital on this one. I just use either the TRS or XLR outputs, and run it to one of my TRS line inputs on the 003.

      • Michal

        Does the built-in pre-amp on your 003 actually impacts the sound?

        • Absolutely. Preamps always impact the sound.

  • Jeremy H

    Thanks for the review. I’d love to hear a shoot-out between the Eureka, Trakmaster Pro and 003 preamps. It would really help me get an idea of how the Eureka affects the signal, compared to the other two.

    • Great idea!

    • Matt Needham

      I definitely agree. I have not invested in a preamp, but I would love to hear the difference between built-in preamps and an independent preamp.

      • Christopher w

        me too, as being on a super budget I don’t really know if getting a good mic would be worth it if it would just sound bad on a cheap interface preamp. or if dedicated preamps are just an extra sprinkle on the audio.

        • It could go both ways. A nice pre will make a cheaper mic sound better, but if the mic doesn’t sound that great anyway, then it will just amplify the “not-greatness.” 🙂

          I’ve heard something as simple as an SM57 SING through a nice preamp.

          Check out tomorrow’s podcast, and you’ll hear what a $100 microphone sounds like through the Eureka.