unable to Profile: Peavey Ultra +

    I've successfully completed numerous profiles with my other amp, an rm100KH with oodles of modules.
    But for some reason, I can't get a profile of my Peavey Ultra+ (?)
    Something in the Lows is coming out real ugly and unusable, overall nowhere near the crisp clarity of the reference amp
    I tried setting the amp with less gain, tightest resonance setting, different volumes
    If this was my only amp, I would think the Kemper is broken or sucks, but knowing how well the KPA profiled my other tones, I'm very perplexed on this one


    This amp yields a superior Mark-ish quality that I love on leads, so any help appreciated!
    Perhaps I'll try sending the preamp out into the power section of my Randall, and vice versa to see if any of that works...

    Hey Ray,


    What mic, how loud, and how does the original mike/amp sound in the Kemper before you profile?


    Pete

    What mic
    57, 4047, naked eye ribbon


    how loud
    a variety of dbs, from about 75-100


    how does the original mike/amp sound in the Kemper before you profile?
    sounds great


    I tried all the variables, but considering I have success on my other amp with every variable combination, this makes it quite curious

    Try backing the mic off slightly, and lowering the profile record in gain a tad. - lower the bass (if thats what the problem area is) on the amp.. let it profile.. then at refine turn the bass up again. - Ive had a few amps that just would not profile too well until I did this.


    Some amp cabs have direction chambers that emit in a wide angle so what you think you captured actually isn't..


    Try blowing whitenoise through the amp, then move the mic untill you feel the presence heighten. normally you do this with phase issues but still works on some problematic amps.


    Let us know how you get on.

    good tips here, I appreciate it
    The cab has been the same throughout different amps, so that is not it
    However, I have put the mics directly up close to the grille; I'll try backing it off and finding the presence with spotting and report back


    Appreciate it!

    Quote from ckemper

    There is a handful of amps that cannot be profiled, because of uncommon circuits.


    it's nice to hear an official reply for this coming from the man himself :thumbup:


    i'm not familiar with the ultra plus, but i discovered that my VH4 had a pseudo noise gate builtin by utilizing two antiparallel diodes bypassed by a 1M resistor. i know peavey uses a similar circuit in the JSX and perhaps also other designs (a potentiometer in place of the resistor can be used to adjust 'sensitivity' for example). this is generally placed after the coupling cap of the 3rd or 4th gain stage. i've tried this in my SLO clone and it works great, although it causes some crossover distortion.


    anyway, my VH4 wouldn't profile well at all before i completely bypassed the diodes. the resulting profile lacked bass and just sounded weird. now the profile is MUCH closer, although i haven't been able to nail the 'compression' on channel 3 and 4 of the VH4. Diezel uses quite a lot of inductors to shape the tone and response, so maybe that's giving the profiling a hard time at fitting parameters.


    oh, and sorry for derailing this thread :)

    Hmmmm... I wonder if future amps of various companies will use more of these "circuits-that-make-accurate-profiling-impossible", as sort of a copy-protection feature. :P (*semi-joking*)


    I mean, they could have their R&D-team research this first, then come up with the rest of the circuit that yields the desired tone.

    Quote from ckemper

    Are those diodes in series or parallel (that is connected to gound) ?


    a picture is worth a thousand words:


    [Blocked Image: http://lh6.ggpht.com/_WbJ1JcTROqQ/Se1RVDY4JlI/AAAAAAAACYI/01-SO852Fc4/xxx.jpg]


    basically, just the two 1N4148 diodes paralleled by the 1M resistor.


    how i understand it, the diodes will "let signal pass" above their threshold voltage, whereas the resistor determines the amount of signal that passes through the diodes. in conjuction, the diodes have sort of a fixed threshold and the resistor is the 'mix' parameter of the gate.


    the 470k resistor to ground (R96), as well as the cap (C63) are for tone-shaping. both diodes and the resistor all in parallel is essentially the complete noise gate. the whole 'gate' is then introduced in series, commonly after the coupling cap of the 2nd or 3rd gain stage. this is also what i encountered in my Diezel VH4.


    i first tried it by without a parallel resistor in my SLO clone, which causes ALL signal to pass the diodes and results in very noticeably crossover distortion. i ended up installing a 1M pot and mostly set it at around 300-400k or completely off for cleans/crunch.


    on a side note: the first time i tried profiling my VH4 ch3 i got the noisegate warning while profiling. mine's a 2007 model that was updated by peter himself in late 2011. i had noticed before that the amp has slight crossover distortion when playing with low vol pot setting on the guitar. now that i've removed the diodes, the crossover distortion is gone and of course the amp is now as noisy as other higain amps on ch3 and ch4. with the diodes it was dead quiet. literally, as if there was a noisegate in the loop. i've tried several gates in the loop now (boss ns2, ISP decimator DIY clone, line 6 gate), but i actually prefer the diodes :D


    i'm a life scientist and not an electrical engineer, so please excuse my poor jargon :D

    Edited once, last by kojak_ ().