Home › Forums › Help/Technical Questions › EHX 12AX7 Preamp as line level/bass preamp???

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  • January 29, 2011 at 2:56 pm #81296
    danbrokenfor
    Participant

    Hi EHX peeps!

    I’m new here as I had a question about the EHX 12AX7 Mic Preamp I have lying around un-used in my studio currently. It’s probably a question for one of the more technically minded people.

    I was wondering whether feeding a line level signal (such as a bass guitar etc.) would be ok to do with this preamp? I don’t know whether it would be the wrong impedance (etc.) or whether it would just be able to work with less gain than a mic usually needs?

    Thanks for your help!

    Dan

    January 29, 2011 at 6:05 pm #114046
    KartoonHead
    Member

    Feeding it a line-level signal is unlikely to cause much upset as far as impedance is concerned, just so long as the output impedance of your DI box or whatever you’re sending into the preamp is lower than the input impedance of the EHX pre, which it will be.

    The only time you really need to worry about impedance is when going from pre to power amp, or chaining power amps, or connecting speakers. The difference it makes with low level signals going into high impedance preamps is negligible.

    Also, the output of a DI box is mic level, not line level, so going;

    Bass (or synth or anything!) -> DI -> EHX pre

    is absolutely fine.

    January 30, 2011 at 9:47 am #114048
    danbrokenfor
    Participant

    Cool! Thanks for the information, I will try what you have suggested using the DI.

    Thanks

    Dan

    January 30, 2011 at 2:33 pm #114050
    KartoonHead
    Member

    No worries! If it all goes according to plan (would you maybe please) upload some A/B’s between the EHX pre and a standard desk pre you have in your studio, would be nice to hear the sort of character it has :)

    January 30, 2011 at 2:34 pm #114051
    danbrokenfor
    Participant

    Sure! I’ll have a go this afternoon for you!

    Thanks

    January 30, 2011 at 5:28 pm #114054
    danbrokenfor
    Participant

    Ok, so here are two (badly played) samples of with the preamp and without.

    Equipment used:

    – A rubbish Stagg bass (P-bass pickup)
    – Behringer DI
    – EHX Mic Pre
    – EMU 1616m Soundcard (the mic preamp in this was used to compare)
    – Cubase Essentials 5

    To my ears the tube preamp sounds clearer and more exciting but has quite a lot of noise on it unfortunately (I’ve had this problem with this pre for a while – any ideas as to why it is noisy?). The drive is quite nice sounding, I haven’t recorded that, but you can here the subtle saturation on the bass high notes. I had to watch the gain as it was quite sensitive.

    Hope that helps!

    Dan

    Samples:

    With Tube preamp:
    http://dl.dropbox.com/u/2063075/Bass – Tube.wav

    With Solid state preamp:
    http://dl.dropbox.com/u/2063075/Bass – SS.wav

    January 30, 2011 at 7:51 pm #114057
    KartoonHead
    Member

    The compression induced by the tube pre is really obvious there, sounds much smoother and more polished than the solid state pre you used.

    As for noise there’s not much you can do, you should however remember that low frequency tracks (like bass guitar) will always sound noisier than others as there simply is nothing much but noise higher up in the spectrum. In my experience all you need to do to mask this is have a high-mid track, be it vocal, guitar, cello, anything in that range, play simultaniously.

    Here’s an example; http://dl.dropbox.com/u/14392951/In_the_Middle_of_the_Night.mp3

    Loads of noise in the first bar when it’s just bass (it’s one of my tracks so I’m allowed to slag it off xD) but when other instruments come in at the start of the second bar; guitar, synth and BVs, the noise is barely noticable. By bar 4 when the drums come in you wouldn’t be able to tell there’s any noise there at all! And remember, those other tracks contain just as much noise! I used the same microphone and the same pre for all of the tracks, and all instruments are played through the same amp. With the obvious exception of the drums, which are sequenced, because 1-mic drum takes rarely go well.

    January 31, 2011 at 10:00 am #114065
    danbrokenfor
    Participant

    Yes, actually it is noticeable isn’t – the compression. I may try out the pre with a few other things to see how it sounds, not sure when I’ve got the time though! :D

    Thanks for your help wit this!

    Interesting track btw – I quite liked it!

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