Red Eye Preamp

Discussion in 'Amps, Mics & Pickups [DB]' started by Pat Harris, Oct 21, 2011.

  1. Pat Harris

    Pat Harris

    Nov 17, 2006
    Brighton, MI
    For the longest time my signal chain was Bass > Fishman Full Circle > AI Ten2. However, I recently joined a group where there is a significant amount of arco and pizz (about 50/50). When I had my pizz tone dialed in, the amp was way too loud when switching to arco. I couldn't dig in with the bow like I wanted to.

    Living in Austin, I decided to try the Red Eye Preamp (Red-Eye Musical Instrument Preamplifier -Home Page). Pretty much anybody that has an instrument with a piezo pickup in town uses one. It's no frills, and it does an amazing job. There is a treble tone control which I leave totally flat, and a boost button. When playing pizz, I use the boost switch, and then kick it off for arco playing. I couldn't be happier. The preamp is totally flat, and IMO much cleaner than any other preamp I've used including the Fishman Pro Platinum. With the HP Filter on the AI, things are running smooth.

    I've since been using the preamp on jazz gigs as it seems to "tighten" up the low end of the instrument. If anybody is looking for that new and exciting piece of gear in the never-ending quest for tone, I would recommend this in a heartbeat.

  2. Really interested in this box, is there anyone who has had more experience with this since 10 years ago?
  3. Ukiah Bass

    Ukiah Bass

    May 10, 2006
    Same here, and if anyone has successfully used the Red Eye with an Ehrlund EAP contact mic?
  4. Ukiah Bass

    Ukiah Bass

    May 10, 2006
  5. US$145 for the Dee-Eye looks a bit expensive to me.
    bassically_eli likes this.
  6. Ukiah Bass

    Ukiah Bass

    May 10, 2006
    So does $199 for Ehrlund's preamp! Considering that's a Gollihur's discounted price from list $350!! Ehrlund is 4.9 Mohm impedance and Dee-Eye is 1.0 Mohm so not sure if Dee-Eye can work with the EAP pickup.
  7. Have you tried Fdeck's HPFpre?
    Best small affordable preamp, IMHO, and variable HPF with that.

    Ok, the Dee-Eye has an effects loop and a balanced XLR output though...
    Must be powered with Phantom power too.
    Can be run as a (transformer) passive DI when using the effect loop input and XLR output, that's interesting!
  8. Ukiah Bass

    Ukiah Bass

    May 10, 2006
    I used to have an Fdeck. It's 10Mohm and only a few dB boost -- not enough from what I read in the EAP threads. Bob Gollihur just dropped me a note and said the Dee-Eye will work with the EAP but he's not sure if it's the "optimum" device given the impedance mismatch.

    I really like the simplicity of the Dee-Eye. Looks well built too. Perfect for a pedal board.
  9. shwashwa


    Aug 30, 2003
    If you have the f deck and you're already running a pedal board, you can plug into that first and put any preamp in the world that you want after it and it should be fine.
    Francois Blais likes this.
  10. Ric Vice

    Ric Vice Supporting Member

    Jul 2, 2005
    Olivette, Missouri
    I tried the FDeck with the EAP, when I first purchased it. It only adds enough to compensate for it's placement in the signal chain, it is not powerful enough use as a preamp for the EAP.
    While I'm sure there are others only the Grace Felix, Headway EDB-2, and the Ehrlund Preamp have enough gain to drive the Ehrlund. I don't know about the Dee-Eye, since I haven't used
    Ukiah Bass likes this.
  11. shwashwa


    Aug 30, 2003
    Use the F deck as an active buffer, wich it is, and put your preamp after it. Problem solved
    Wasnex and Francois Blais like this.
  12. Just purchased a used one on Reverb and awaiting delivery. I’ve been going Lifeline pickup direct into my Acoustic Image head and was very happy with the results until a couple months ago when I noticed a drop-off in the output of the pickup. Sound seemed to thin out as well; not as warm and robust as when I first got it.

    Read a rather glowing description of the Red-eye preamp on Gollihur which gave me the confidence to give it a try.
    JLubinsky-Mast likes this.
  13. BrandonL


    Sep 20, 2018
    Boise, ID
    So, whaddya think after 7 months? Do you still have it/use it/love it/hate it?
    bherman likes this.
  14. flatback


    May 6, 2004
    SO ....
    The red-Eye caught my attention because of something I read on the website and had to know more....I contacted Daren at Red-Eye and he has been corresponding with me about what the RedEYE does. I am going to reprint his note below but it sounds really intriguing: This preamp loads the pickup impedance differently based on frequency. According to Daren a pickup may need 4Mohm impedance on the lowest note but much less on higher notes. The RedEye adjusts impedance according to frequency on the fly. So my preamp set to 10Mohms is acting like a wet blanket for most of the notes....
    here is Daren:
    You may be aware that some piezo pickup elements can self-resonate or "ring" at particular frequencies depending on the piezo material and on the shape and size of the pickup elements. Some of those frequencies may correspond to notes you want to play or some harmonic of such a note. Depending on phasing, that note or harmonic may be increased or decreased in loudness by the ringing. That results in a "wolf" note or a missing note or an unnatural string tone.

    A typical piezo pickup has an impedance of several megohms at low frequencies and of several hundred thousand ohms at high frequencies. When the impedance of a pickup is matched by the impedance of the "load" it sees at the preamp's input, the ringing will be quickly damped.

    All of our preamps use field-effect transistors and feedback around an operational amplifier chip to match the preamp input to the pickup impedance across the entire audio frequency range. The frequency response of our preamps is flat when the treble control is centered. We do not try fancy EQ tricks to "shape the curve" of the preamp.

    ...and then when I asked for more clarity on what he meant:

    I'll try to explain more clearly...
    What I mean about a piezo pickup element "ringing" is that it is a mechanical system (like a xylophone bar). The pickup is excited by the acoustic vibrations from the strings and the body of the instrument. When a pickup element is excited at one of its resonate frequencies by the instrument it produces a louder or weaker signal at that frequency.

    Potentiometer-adjusted input impedance doesn't help because a piezo pickup's impedance varies with frequency. A typical piezo pickup will have a 3,000,000 ohm impedance when measured at 20 Hz while if measured at 10,000 Hz it may have a 300,000 ohm impedance.

    If you set your adjustable impedance preamp to 1,000,000 ohms you will match the pickup impedance at only one frequency...a frequency somewhere in the midrange where this hypothetical pickup measures 1,000,000 ohms. The Red-Eye preamp varies it's impedance across all audio frequencies to match any pickup at all frequencies. Only when the preamp input matches the pickup impedance at a resonant frequency will the self-resonance of the pickup be damped.

    sounds great. I just have to try one now and see if it translates aurally.
    BlueRock, bassically_eli and Ric Vice like this.
  15. Ric Vice

    Ric Vice Supporting Member

    Jul 2, 2005
    Olivette, Missouri
    I think you already have this covered when you use the Sarno Black Box.
  16. flatback


    May 6, 2004
    Do you? I love my Sarnos and honestly the Black Box is spectacular. But I never heard of adjusting impedance per frequency. Maybe these other boxes do it and I am just getting caught up in the way it is being explained by Daren, but it sounds like something different....
  17. Even though it is true that the low frequencies need a higher impedance than higher ones, the Piezo has one or a few eigenfrequencies at which it might ring. These are more or less constant, so it does not help to have a frequency dependent resistance (which is what the word impedance means).
    The damping is needed at the eigenfrequencies, typically the lowest mode only.

    The piezo can only deliver a certain amount of electrons in one direction before the mechanical stress reverses and the capacitor-like piezo gets loaded in the opposite polarity.
    The low frequencies need a lot more electrons to be transmitted until the polarity changes than higher frequencies. If the input impedance is too low, the piezo runs out of electrons and the voltage gets dropped because of that which results in a distorted waveform.
    BTW, this also happens with higher frequencies when present with the low ones, but a bit less. But the eigenfrequencies of the piezo are catched by higher frequencies too, so they should be damped for them too. That means the same impedance (at the eigenfrequency of the piezo) for low or high frequencies is needed to damp a certain eigenfrequency of the piezo.

    The only thing where you want different resistances at different frequencies is if you have several eigenfrequencies of the piezo. That could be higher modes, but they typically don’t ring as long as the lower modes, so not of much importance.

    That might be tuneable for a real frequency dependent resistance, but then it might be a bit of overkill to implement and the results might not be much better than damping the main eigenmode only. Don’t expect a miracle.
    A tuneable and tuned resistor for the input impedance might work nearly as well. A switchable one might miss the optimal damping a bit.

    The only reason why a lower impedance might be preferred beyond the damping of the eigenfrequency of a piezo crystal is that it is less sensitive to electric noise.
    With an open cable the input might sound noisy, so customers may reject such an amp that hisses and gets radio in it. So the lower input impedance might be a marketing decision.
    bassically_eli likes this.
  18. JeffKissell

    JeffKissell Supporting Member

    Nov 21, 2004
    Soquel, CA
    l think he means this is a vacuum tube’s inherent nature.
  19. flatback


    May 6, 2004
    So, in laymans terms: I have it covered? Well Daren is going to send me one to try so I will let you all know how it sounds....
    Last edited: Aug 9, 2022
    Ric Vice and BrandonL like this.
  20. BrandonL


    Sep 20, 2018
    Boise, ID
    Yeah, please do - it would be nice to get another report from someone after they attach it to a large acoustic stringy thing. It seems odd that there haven’t been more reviews.
    Ric Vice likes this.