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Cable Query

Discussion in 'Pickups & Electronics [BG]' started by NEBADON2000, Dec 20, 2018.


  1. Using the example of a Acoustic electric Bass. With the built in preamp at the output is it a line level signal or instrument signal? Outboard preamps are all line level. What type cable should you use and what input. Do you plug into instrument level input on a preamp/combo amp or to line level input such as 'preamp input' or any line input? Use a line level cable or Instrument Cable? If plugging into Instrument input your Bass signal now goes through another set of Volume controls, Eq, and preamp circuitry. The more electronics a signal passes through, the more chance of distortion from original Bass Tone and frequency imbalance. [I come from a High End Audio Background that preaches virtues of 'Straight Wire With Gain'] In my 25 year experience with High End Stereo Equipment although something may work with various type cables a cable is not just a cable, the type and quality are critical. I am guessing whether an AEB or ACTIVE Bass converts preamp line signal to instrument just before output. Can anyone teach me on this?
     
  2. There's no one answer to this. There's no standard for "instrument level". Some active basses have output similar to line level, but that's just anecdotal really. I mean how would you standardise it?

    Output z is also not standardised for active basses, and may well change as you adjust the volume control (depending on the circuit of course). So knowing your line input z is at least say 20k would mean most active basses could drive this OK.

    As for leads, well it's important to use good quality cables in general, but for active basses, it's more for reliability, shielding, and good connections. With a low z signal, the cable capacitance is not a factor that would degrade the sound.
     
  3. 96tbird

    96tbird PLEASE STAND BY

    Pedals are pugged into the instrument input on amps all the time with no ill effect. Why would an onboard pre be any different? They’re not. Use the pad or gain on the amp to throttle the signalthen focus your attention to not letting the thing feedback on you.
     
  4. el murdoque

    el murdoque

    Mar 10, 2013
    Germany

    First of all, musicians make no big difference between line level and instrument level cables.
    When using a passive instrument you should have a quality cable that is as short as possible before it hits the first buffer. From there differences in cables are more or less neither audible nor measurable as long as you use
    a minimum standard. Most people choose cables around 20 bucks where they get Neutrik (or other high quality) jacks and a decent wire between them. I own cables from 10 bucks to 170 bucks and in a blind test I could not tell you my $169 Vovox cable from my $13 Fender cable if my life depended on it.

    As to the desired sound: This is the making music part, not the consuming part.
    Speakers that act as a bandpass because they do not transport certain frequencies as well as pre- and poweramps that add distortion are red flags in the HiFi community but often sought after in musical equipment.
    What happens when you turn the up the gain past the breaking up point is irrelevant on a HiFi amp and crucial on a guitar / bass amp.

    So when the signal that leaves your basses onboard preamp is already exactly that signal you want to hear from the cabs AND the basses output is strong enough, you can plug that directly into an amplifiers FX return, thus bypassing the entire preamp section (at least on most amps).

    Musicians often like to stack equalizers from different units, though.
    For example, you add a little bass boost on the onboard electronics, then go through a pedal that has some impact on the tone and then you go into the instrument input of the amp and have further EQing happening there. The results of stacking these are always unpredictable. Could get mushy. Could get great.
    For some it's fun to experiment and for others it's tedious.


    The amplifiers tonal controls have another important value: When playing live, you will send a signal to Front Of House. This is usually done either with your amplifiers built in DI or with a DI box that gets plugged between your bass and your amp. When the DI on the amp is set to PRE, it does more or less the same thing the DI box does: Send a signal that is untouched by the amp's EQ. So FOH can EQ your bass to fit on the FOH speakers and you can EQ your bass to fit your own speaker(s) on stage.
     
  5. Geri O

    Geri O Supporting Member

    Sep 6, 2013
    Florence, MS
    I don't mean this the way it sounds, but as a 25-year pro sound veteran, I'm curious to know, what constitutes the difference between a line level cable and an instrument cable (unless you mean balanced/ 2-conductor shielded and unbalanced/single-conductor shielded)?
     
  6. "Instrument cables are designed to carry low-voltage instrument signals"

    "Therefore an instrument cable must have lower impedance than a line level cable, and since the instrument cable typically is longer, the requirement of low impedance per meter gets even higher. Also, the shielding needs to be better."

    This I assumed, Cables 'marked' line or patch or marketed Instrument can carry either signal but it is advised for best performance to use designated cable for purpose. Example a typical RCA cable can pass a Digital/Video signal to a D to A converter or TV BUT it is obvious to Ear and Eye using a designed Digital or Video Cable gives better performance. I don't have tech knowledge to explain why.
     
  7. PS to last post; This is why I asked original question in a AEB OR ACTIVE BASS with 'built in preamp' what signal is leaving the Bass output. If you have a separate Bass preamp and Amp you would buy a line level/patch for connection. I know most Bass preamps separate or in a combo have active passive switch to compensate. I may be unnecessarily picky here; Since many use pedals[after Bass output] with patch chords between and after preamp circuit and the industry sells Instrument marked cables without any mention of Active or Passive. Also seems Instrument cables are superior to line level and balanced is preferable if possible for long runs; based on my recent research.
     
  8. el murdoque

    el murdoque

    Mar 10, 2013
    Germany
    The active input/pad for active bass is mostly used as a last resort only. It can have audible effects on the signal when the pad is engaged, so the rule of thumb is to use the normal input and only when the gain brings serious discomfort, to use the active one.

    The impedance differences on a bass and a preamp input usually are quite large. A bass with active preamp should be well below 100 ohms, while a passive one is usually a bit over 10k.
    Modern preamps run around 1meg - so if the cable adds a few ohms to that equation, it hardly matters. In most cases, we're talking about a slight rolloff in the frequency range of 16k+ Hz.

    So an instrument cable is used to transport a rather weak signal from a low ohm source to a high ohm destination (apologies to people of the trade for the last sentence, pls don't beat me up).
    While a Line cable is used to transport a slightly less weak signal from a low ohm source to a high ohm destination. One could argue that a decent cable will do both equally good.
     
  9. LUpton

    LUpton Supporting Member

    Oct 22, 2012
    Tampa, FL
    Probably too old for this sh--
    Classic overthink in OP...

    Murdoque has the right idea.
     
    96tbird and Geri O like this.

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