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I have too much distortion from my 'too hot' preamp!

Discussion in 'Amps and Cabs [BG]' started by LongHairFreak, Aug 7, 2008.


  1. LongHairFreak

    LongHairFreak Insert cool nickname? Nobody's given me one yet. Supporting Member

    Aug 7, 2006
    Twin Cities - MN
    Hey Fellow TBers

    My appologies for this long explaination. Please bear with me.

    My Low End True Voice preamp is so hot that I can't turn the gain much past 2 or 3 w/o getting distortion from my low B & E. To remedy this, I've lowered the vols on my bass (passive), but that cuts the highs more than my LETV compensates for. Also, I've lowered the bass on my LETV, but that really detracts from the sound I want. I spoke with Brian Barrett (LowEnd) about this, but our conversations didn't come up with any workable options. I also spoke with Jorg Schroeder (my cab - who also has this pre) and he suggested I might want to get my LETV modified, but that's not an option I wish to explore either.

    Then I spoke with Michael Dolan (put my bass together) and he suggested I place a second pre after my bass, to change the gain going into my LETV. Sort of like turning my passive bass active w/o modding it. I don't really want to put out $200+ for another pre with extras that are normally desired in a pre, but I don't believe a gain box exists. So, I'm guessing a used Sadowsky, Aguilar, or some other outboard would do the trick.

    What are your thoughts? Does this sound like a workable theory?


    Thanks for any and all suggestions/advice.
    Brett
     
  2. bongomania

    bongomania Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    FWIW "a gain box" does exist. There are lots of pedals on the market which are able to reduce or increase your signal level without otherwise altering it much.

    TBH it sounds to me like the problem is not the LETV being "hot"; typically when someone says a preamp has too hot of a signal, they mean it is causing the next item in line after it (e.g. a power amp) to distort. The solution in that case it to turn down the output level of the pre, or install an attenuator if no control is provided.

    Since you say it is the LETV which is distorting, the problem is that it doesn't have enough headroom in relation to your bass signal.

    It sounds like your low B and E are at much higher amplitude than your other strings, which is fairly common even with passive basses. There are several solutions:
    1) Adjust your pickup height (or the string height if necessary). This solves the problem more often than not.
    2) Use a compressor. A good one will keep the peaks of the lows closer to the highs.
    3) Use an EQ pedal. One that has more specific controls than just low/high or lo/mid/hi. Look for a nice graphic or parametric EQ. That way you can dial back the specific frequency range which is causing the LETV to distort, without gutting your lows and low mids altogether.
     
  3. RickenBoogie

    RickenBoogie

    Jul 22, 2007
    Dallas, TX
    +1, or compressor AND eq.
     
  4. JimmyM

    JimmyM

    Apr 11, 2005
    Apopka, FL
    Endorsing: Yamaha, Ampeg, Line 6, EMG
    That's fairly consistent with most Ampeg amps I've played. The distortion threshold kicks in fairly early. I can't turn my 77 B-15N or my 69 SVT up past 11 o'clock without getting distortion. It's putting out the clean wattage it claims, but the distortion threshold is fairly low. I suspect the True Voice is made the same way.
     
  5. LongHairFreak

    LongHairFreak Insert cool nickname? Nobody's given me one yet. Supporting Member

    Aug 7, 2006
    Twin Cities - MN
    bongomania08-07-2008, 03:47 PM

    TBH it sounds to me like the problem is not the LETV being "hot"; typically when someone says a preamp has too hot of a signal, they mean it is causing the next item in line after it (e.g. a power amp) to distort. The solution in that case it to turn down the output level of the pre, or install an attenuator if no control is provided.

    You could very well be right about the power amp distorting. I've got to admit, I only say the LETV is too hot b/c that's what I am told (by J.Schroeder and others). The only way to turn down the oupput level of this pre is with the gain/vol control and as I've said,2 or 3 is max before distortion.


    Since you say it is the LETV which is distorting, the problem is that it doesn't have enough headroom in relation to your bass signal.
    I'd be surprised at that, but I really don't know.


    It sounds like your low B and E are at much higher amplitude than your other strings, which is fairly common even with passive basses. There are several solutions:
    1) Adjust your pickup height (or the string height if necessary). This solves the problem more often than not.
    Lowering the pickups hasn't helped. Raising the strings?? (sigh) Well, I didn't really want to do that; I'm trying to work with a lower action.

    2) Use a compressor. A good one will keep the peaks of the lows closer to the highs.
    Hadn't thought of that!

    3) Use an EQ pedal. One that has more specific controls than just low/high or lo/mid/hi. Look for a nice graphic or parametric EQ. That way you can dial back the specific frequency range which is causing the LETV to distort, without gutting your lows and low mids altogether.
    I've got a Raven Labs True Blue EQ that I've been trying to work with, but no luck so far. I could just be not using it properly though.
     
  6. LongHairFreak

    LongHairFreak Insert cool nickname? Nobody's given me one yet. Supporting Member

    Aug 7, 2006
    Twin Cities - MN
    So a gain box is most probably not what I'm looking for, eh?
    I don't really want to mod my LETV, but could a volume pedal (as some has suggested) between my LETV and power amp work?
    Or is this not the same as what you're saying BongoMania?
     
  7. amper

    amper

    Dec 4, 2002
    US
    Try building an L-pad or voltage divider network attenuator in a small accessory box. A couple of resistors, and a couple of jacks, and it's totally passive.

    Here's a link:

    http://www.uneeda-audio.com/pads/
     
  8. you sure that it is the letv distorting, and not the first gain stage in the amp? whats wrong with keeping the letv's volume on 2-3? its designed to change the sound. use the volume controls on the amp to make it louder.
     
  9. bongomania

    bongomania Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    Yeah, the first most important thing is to figure out exactly what is distorting- the preamp or the power amp. That's the only way to know how and where to solve the problem.

    I looked for info about the LETV on the web and was not able to find out whether the Volume knob is an active control over the level of the signal going into or through the tube stage, or a passive control over the level coming out of the tube. If a LETV user knows the answer, please let us know.

    Either way though, you may need to borrow (or buy and then return) some extra gear to test the location of the distortion. You need something that can attenuate the signal at "instrument level" (like a typical pedal) and at "line level" (typically rack units, or the output of a preamp that would normally feed a power amp). An EQ pedal and a rack EQ would work, or any unit that can handle both instrument and line levels. If you're electrically savvy you can just put a passive volume pot in line for either level of signal.

    I guess what I'd recommend first is using an EQ or compressor pedal to regulate the signal going into the LETV. See if you can find a setting which allows you to turn the Volume of the LETV up without distortion. If that works, (a) problem solved, and (b) we can assume it was the LETV that had been distorting before.

    If it doesn't work, if you still get distortion turning the LETV Volume up past 3, then get a rack unit which can work at line level, and put that between the pre and the power amp. That way you can regulate the level of the signal coming out of the LETV. At that point you want to see whether you can turn up the LETV Volume (while turning down the line-level attenuator) without distortion.

    If you still hear distortion, then I'd suggest the LETV is prone to distort itself at Volume settings above 3, and you're up a creek. Need a different pre.

    However I would be surprised if that were the case. I suspect once you manage your signal peaks going into the pre, everything will be solved.

    Oh, and footnote: "Gain" means signal increase. If you want to turn down your levels, you don't need a device that provides "gain"; you want an attenuator (basically a passive volume knob).
     
  10. LongHairFreak

    LongHairFreak Insert cool nickname? Nobody's given me one yet. Supporting Member

    Aug 7, 2006
    Twin Cities - MN
    Well, there's a lot of good information here, so it looks like I've got a bit more researching/experimenting to do. Thanks guys.

    Brett
     
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    Primary TB Assistant

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