Profiling newbie questions

    Last Saturday, I tried my hand at profiling a miked amp, a Vox AC15CH through an AC30 2x12 extension cab from North Coast Music with Eminence GB12/V12 speakers miked with a Sennheiser e609. (Hey, it's what I have lying around the house. :D ) I had kind of mixed results, and it left me with a couple questions about the profiling process.


    Before I get started with my experiences with the AC15, I did want to ask about one statement in the profiling guide that I found curious:

    Quote from Kemper

    However, there are a few exceptions: some distortion pedals use a special design that cannot be profiled accurately, for instance the Tube ScreamerTM.

    What exactly is this "special design"? I mean, the Tube Screamer is common as dirt and has a huge number of knockoffs and derivatives, so it doesn't seem all that "special" to me. Is it the input buffer on the TS that's the problem? If not, what is it? And if that's the case, why do I see so many profiles that claim to have a TS or similar boosting the reference amp?


    Anyway, first I did direct and studio profiles of the Top Boost side of my AC15 set slightly crunchy, which turned out great. I created a merged profile from the two, and that worked great as well. So far, so good. Then I set up the Normal side of the AC15 "Brian May style" (dimed with a treble booster, a BBE Bohemian, out front). The direct profile of that worked OK. Then I tried making a studio profile... and that's when things went off the rails.


    First, the profiler complained that there was a noise gate on in the signal chain. Now, there was a noise gate in the signal chain, an EHX Silencer (the recent version) which had the Bohemian in its loop, but it was off. Maybe "off" on the Silencer isn't really off, but I didn't try to rewire things because I had a larger issue (see below). But could the Kemper really be complaining about the fact that there's a noise gate present in the signal chain even if it's off?


    Second (and more problematic) was that the resulting profile sounded nothing like the real thing. The profile was MUCH bassier and less midrange-y than the real thing. So I tried combining the direct profile of the Normal channel with the cab from the Top Boost profile, and got more or less the same result. That leads me to think that the huge bass in the cab is almost certainly an artifact of the mike, probably from proximity effect. (I had the e609 about 1-1.5" off the grill cloth.) How do people generally handle mic proximity effect in cab profiles? Run the mic through a mixer or mic preamp with a low cut filter? Mike the amp from further away? Tweak it with the Low Shift cab parameter?

    "Love is a snowmobile racing across the tundra and then suddenly it flips over, pinning you underneath. At night, the ice weasels come."
    --Matt Groening


    "Cannot run out of time! There is infinite time. You are finite, Zathras is finite, this... is wrong tool. No, not good, no, never use this." --Zathras

    Quote from tabaer

    How do people generally handle mic proximity effect in cab profiles? Run the mic through a mixer or mic preamp with a low cut filter? Mike the amp from further away? Tweak it with the Low Shift cab parameter?

    All sensible options that I'm sure people use, Troy. Personally, I'd start with mic'ing it closer to the edge of the cone, and if that doesn't work, from further away - nothing radical to begin with 'though (I'm thinking 6" to a foot max).


    Also, and I'm no amp expert so I'm only raising this as a possibility, are you using much power-amp distortion for the "Brian May style" setup? The manual details the issues with this, and it only affects a few amps as it's the old-school approach to distortion and isn't an option on many modern amps. If this is the case, try lowering the power-amp gain and compensating by increasing the preamp gain a little. Do it in increments of 10% maybe, but don't be surprised if you have to go as low as 40% power-amp gain.


    If the amp doesn't offer power-amp gain, I'm afraid I'm all out of suggestions. No need for concern 'though; I'm only repeating what I've read here in the forum so hopefully someone who has experience Profiling the amp will chime (get it? Vox amp - chime? Uugghh...) in.

    I've got the dreaded noise gate in chain alert but only when I was going for almost stupid max gain on Boogies and a Cream Machine or using a treble booster into an amp set loud. Did you refine the profile? Sometimes this makes things much better and sometimes it makes them worse. It's weird. Anyway, if I get close, sometimes I'll skip the refining. There is just so much you can do with eq, boosting and compression within the Kemper that close is perfectly cool sometimes, and you can always reprofile tomorrow.

    I'll agree with Nicky that every time my profile is crazy bassy I move the mic out more towards the edge. Seems like more towards the middle with Celestions and more toward the edge with alnico mag speakers works well for me.

    Sometimes profiling is just routine as it can be and sometimes you throw the Kemper for a loop and the profile is nothing like the original. The usual problem is too much gain on your set up. Back things down and remember you can add tons of gain later, after the profile is saved.

    I finally got a decent profile of my AC15 in Brian May mode, but it required a combination of things:

    • moving the mic out to about 6" off the grill cloth and in between the two speakers
    • using the bass cut on the mic preamp
    • lowering the gain on the treble booster from ~75% to ~50%
    • tweaking the pre-profile EQ on the Kemper with as much bass cut as possible
    • making some post-profile EQ tweaks (boosting bass and mids a little and cutting treble)

    Even so, it's got a little bit of harshness in the upper mids that I don't quite like, but the real amp has that too...

    "Love is a snowmobile racing across the tundra and then suddenly it flips over, pinning you underneath. At night, the ice weasels come."
    --Matt Groening


    "Cannot run out of time! There is infinite time. You are finite, Zathras is finite, this... is wrong tool. No, not good, no, never use this." --Zathras

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