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How much gain on a pre amp

Discussion in 'Amps and Cabs [BG]' started by cnltb, Nov 4, 2010.


  1. cnltb

    cnltb

    May 28, 2005
    That is the question...
    How much gain, in "db" do bass out board pre-amps give on average...on the active and the passive side( in the case that they have the active and passive option)?

    Thanks
    :)
     
  2. Bassmec

    Bassmec

    May 9, 2008
    Ipswich UK
    Proprietor Springvale Studios
    Well thats all very variable, the earliest tube designs like the RCA OP-6 had as much as 90 dB for an output of +4 dB.
    Transistor designs such as the Neve 1073's have 80 max.
    The rest is all a case of varying the input impedance and PAD to taste.
    About 34 dB will get you there or there abouts but its all just a generalization.:D
     
  3. cnltb

    cnltb

    May 28, 2005
    Thanks!
    I am mostly interested in solid state class A things(not sure if that makes a difference).
    A pre that acts basically as a "hot wire", amplifying the signal and not doing any more.

    also...is it correct, that the input impedance should be basically as high as can be,as I was told a couple of times?
    If it isn't, how would this be defined and what would be the effects of too high an input impedance?
    And...what ,if it is correct, are the benefits of high input impedance...above 1 mega Ohm...?
    Thanks again, very much!
     
  4. Bassmec

    Bassmec

    May 9, 2008
    Ipswich UK
    Proprietor Springvale Studios
    OK. With or without the EQ section, I would try to build one of these and copy the input impedance that Rupert thought good for the instrument in:
    http://www.gearslutz.com/board/high-end/360407-building-1073-a.html
    :bassist:
     
  5. cnltb

    cnltb

    May 28, 2005
    No EQ.
    Thanks for the link!
    :)
     
  6. bongomania

    bongomania Gold Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    1 meg input impedance is a common, and perfectly good, value for bass. If you're running a passive bass into a long cable, then maybe higher than 1 meg could be beneficial; but 1 meg would be fine in most cases, and will capture all the highs and tone. With short cables or active basses, you don't even need to go as high as 1 meg.

    For a "wire with gain", look into mic preamps that have a DI input. For example, check out the half-rack unit by Grace Designs.

    35 dB is a bare minimum if you want to drive a power amp; I like to have at least 50 dB available. For recording, a lower amount is perfectly fine.
     
  7. bongomania

    bongomania Gold Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    To clarify, the deal with the input impedance is that the higher it is relative to the output impedance of your instrument, the better able it is to receive the highest frequencies; and a lot of what people hear as "tone" is upper harmonic content. So if you want crystal clarity and sparkling highs, go for the 1 meg or higher. But if you like a dark Motown/vintage amp tone, then high input impedance is meaningless. Some people feel that going much higher than that can make the signal "harsh" due to the amount of high-frequency content, but that is easily solved by turning down the treble, at one end of the cable or the other.
     
  8. cnltb

    cnltb

    May 28, 2005
    This is pretty much what I thought.
    Thanks very much!!
    I use passive instruments and use the pre for recording as well as for driving a power amp. I tend to record with short(1m) cables if possible and like to keep it as short as I can, live too.

    I do like to hear as full a picture as possible to begin with, as that can be trimmed a lot easier I recon, than going the other way and starting from a muddy place.

    I guess if I ever use an active bass I can always turn down and adjust the eq on that.

    Thanks again, very much !:)

    One other thing...
    You have a basslab soul?
    How is it working for you and do you have soundclips of it?

    I have to say that I quite liked those basses when I tried them,which is quite a while ago.
     
  9. bongomania

    bongomania Gold Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    I do have the Soul V, but I am in the process of selling it. The main reason is plain finances, I really didn't have the money to spend--I just so badly wanted to try a Basslab that I bought it anyway. :) The preamp is very nice, very low-noise and flexible. The electronics on the whole had a clean, dry, hi-fi sound. I feel it's very much a "what goes in, comes out" kind of instrument, that is, it won't sound amazing unless you play amazing, but if you can then it will.

    Do check out the world of high-end mic preamps. A good percentage of them have DI input jacks and plenty of gain on tap, and many were also designed to be a "wire with gain", more or less.
     
  10. cnltb

    cnltb

    May 28, 2005
    Thanks for the info on the bass!
    As to mic pres and the reason why I asked all the questions I asked;That was basically because I was thinking about certain alterations to be done to my main pre amp which is a one volume button kind of thing(has one mute button too)
    It's a great pre amp and sounds/performs fantastically well.
    I was nonetheless thinking about upping the gain and input impedance on it,to get even more from it,(as I had heard that this may be beneficial) as well as possibly changing the output transformer on the DI outs( It's got two balanced line outs and two transformer isolated DI outs).Your input and that from Bassmec has helped me decide on doing it-since my own technical insight knowledge on these things is rather limited.
    The mic pre connection comes in as the pre was made by Buzzaudio, whose mic pre amps I like very much and seeing them kind of gave me the push to call them and ask if they'd do me a custom pre amp in the first place.:)
     

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