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  • Playing a guitar through a bass amp

    I've been playing the Rumble 500 all weekend and I really dig it. Just for giggles and grins, I plugged a regular 6-string guitar into it. I'm sure opinions will vary on this, but with some eq tweaking I personally think it sounds quite ok! It's no '59 Bassman but the Rumble's built-in overdrive works great with a guitar as well.

    So I know that plugging a bass into a guitar amp will destroy the guitar amp's speaker, but is the same true when using a bass amp as a guitar amp? With or without overdrive/distortion effects (including boosts and pedals)? Playing chunky palm-mutes and screamin' leads, eliciting feedback and all the usual rock guitar stupidity? With or without the compression tweeter turned on or off?

    Dumb questions I know, but I'd hate to be wrong.

    Thanks.
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    It's funny how nowadays the only decent metal around is the theme music for a cartoon that makes fun of metal bands.

  • #2
    No, you wont hurt it. Mainly its the design. The lower the frequency, the more powerful and durable the amp and speakers need to be to produce those frequencies. Bass requires a higher wattage amp to produce the same perceived loudness as a low wattage guitar amp. This is because our hearing is not linear.

    Our hearing peaks and is most sensitive at about 1000~2000Khz which is the pitch of our speaking voices. (and the center of guitar pitches) Our hearing drops off drastically below 200hz and above 10K and it takes more wattage on the low end to make it sound even with the mids. Maybe this is why men are able to block the higher pitched nagging voices of their wives so easily? We feel allot of the bass end tinstead of using our ears to hear it too.

    Bass amps can be fairly good for guitar depending on the type. I've heard many which are major dogs. I even owned a few. I have a Traynor Bass cab with a pair of 15" Celestion in it that sounds wonderful for clean guitar, especially rhythm guitar. I have other bass speakers that sound awful. I have a pair of 10's from my EV bass cab that don't produce anything over 2.5K. You try and high notes with them and you have dead notes. The speakers themselves are rolling off all the top end.

    I've seen many bass heads that roll off all high frequencies above 3K too. My Crate bass head has an EQ that maxes out at 2.5K. That's fine for getting some slap bass tones, but guitar has double the frequency range of a bass and gets up to around 5~6K before it rolls off.

    Most bass amps just aren't voiced to target those high frequencies very well, plus the EQ ratios are in the wrong places. The bass knob on many heads boosts/cuts lows 40~150HZ, Mids 150~500hz and highs 500-2.5K

    The low EQ targets frequencies below what many guitar pickups can produce, The mids are bass tones on a guitar and the highs are mids, essentially leaving you with no treble control for guitar. (not that it matters, most bass speakers wont produce the highs even if the head did produce them)

    There are other items too. Bass speakers are thick and heavy. They are stiff, carry allot of inertia, and take allot of power to get them moving. They respond properly to a low frequency bass string and can "keep up" with the speed of those low waves. A guitar string snaps much quicker, quicker then many bass speakers can respond. If you have a thinner cone with a wider frequency you may not notice it but some 15's will flatten and distort high frequency transients and eliminatee many overtones guitar strings produce.

    One other factor, when playing in a band with other players, a band sounds good when the instruments work within their own frequency ranges. There's a thing called masking that occurs when two instruments are competing for the same frequencies. If you've ever played in a band with two guitar players using similar gear trying to dial up the same response, you wind up in a volume war trying to be heard over the other guy. One has to take the higher frequencies over the other or one has to have a mid boost and the other a scooped mid to be heard separately from the others.

    When you play through a bass amp your tone can be shifted down into the bass ranges and you'll either get creamed by the bass guitar or you'll interfere with him being able to hear his notes.

    Now it may sound good playing solo or playing without a bassist because you're producing some lows where the missing bassist should be, but for most bands and music played you'd simply be an annoyance copping those lows. Guitar is a midrange instrument, not a bass. There may be some exceptions with undertuning, Barritone guitars and acoustic guitars. Acoustics can sound huge through a bass amp (so long as you have a High frequency horn for the highs)

    My rule of thumb for frequencies ranges are simple. I use the drummer (live or machine) as a guide to dialing in my tones. I want my lows to extend down and roll off just above the kick drum. The kick needs to be open for the bass so you don't want to mask either going too fat on the bottom.
    I get my mids to compete with the snare. You can scoop it so the snare stands out of course but you want the mids to impact the same .

    The highs are the tricky part. You want them to compete with the high hat but no higher. You want to leave the highs open for the drummers cymbals and the high end of the vocals.

    The big mistake guitarists who don't play in bands make is they try an cover the entire frequency range of a band from bass to the high cymbals so they dial up this excessively wide range of tones (or as in your case maybe just an excess of lows) This wont work in a band with other players. They'll simply stick their fingers in their ears and tell you to take a hike.

    Targeting your frequency response is probably just as critical as being able to play the instrument well. I've seen countless bands where the guitar sounds great standing directly in front of the amp but you walk 10' away and it sounds like Sh!@. Reason being is he's a bedroom player and has no concept of dialing up his sound so it projects long distance. Playing live you want the guy on the back wall to hear you great. Noone gives a dam id you're grooving to your own tones. Of course you may find it uncomfortable playing with tones that project a longer distance but it does in fact get easier the more you do it.

    Same thing with recording tones. I played out for time for 20 years and had a great live sound happening. When I first started getting into recording seriously I had to reeducate myself all over again. I can say getting great recording tones goes a long way to getting good live tones too. Dialing back so its at least 1/2 clean was the biggest lesson of all. It makes playing leads a bit more challenging but over time you become a much better player.

    Anyway that's my take on it. If you think a bass amp sounds good then I'd think your guitar amp is hurting for solid clean tones and/or you were getting board with the driven tones it produced. I'd think the fender could produce some decent cleans but I wouldn't want to use it live, at least not with the stock speaker. Maybe with am old JBL or Altec speaker. Those speakers produced come crispy highs with an aluminum dust cap that can produce some jangle and get some SRV tones.
    Last edited by WRGKMC; 03-08-2016, 02:19 PM.

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    • #3
      Designed for acoustic bass guitar. The SWR was pretty popular with acoustic guitar players

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      • #4
        As previously mentioned, you won't hurt a bass amp playing a guitar through it. You won't hurt a guitar amp playing a bass through it either, provided you keep it turned down and don't go crazy with the volume. I've played bass through my Fender Frontman but not very loud. Before I got a "real" guitar amp, I played a Strat copy through my SWR LA12 bass amp. My Frontman stays at church and I still use the LA12 as a practice amp.
        You can see from this example that a guitar has most of its energy at around 200 Hz but it also has plenty at 100-600 Hz and a decent amount clear up to 1 KHz:
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        A typical single coil guitar pickup has a peak at 2-5 KHz with a sharp cutoff above that (a humbucker has two peaks) but it will go down into bass territory with ease. The notion that the pickup won't produce lower tones is a myth.
        It helps if the bass amp has a "tweeter" or high frequency driver like my LA12. A number of bass amps have them; the main reason is that the smaller, lighter driver handles the fast transient at the leading edge of the wave. Your Rumble 500 has a HF horn and a pair of 10" speakers, which means it can handle the tones of a guitar just fine. An open back guitar cab or amp generally doesn't have much bass because the wave from the back of the speaker cancels out the wave from the front. Higher frequencies work differently. A guitar played through a bass amp can sound boomy because the lows that are normally missing are there. Proper EQ can go a long way toward getting a decent sound.
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        • #5
          Playing a bass through a guitar amp is probably not a great idea. It's fine as long as you don't get too loud. You won't hurt the amp but you can pretty easily blow the speakers. Playing a guitar through a bass amp, I see no problem with.
          Ampeg SVT II, Ampeg SVT Cl, Ampeg Heritage 8x10s, Rickenbacker 4001, Spector NS4XL, Fender Am. Deluxe J.

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          • #6
            Originally posted by Bassbob View Post
            Playing a bass through a guitar amp is probably not a great idea. It's fine as long as you don't get too loud. You won't hurt the amp but you can pretty easily blow the speakers. Playing a guitar through a bass amp, I see no problem with.
            If the speakers have a higher wattage then the amp you shouldn't blow them but they will sound blown out with all those bass tones happening.

            You can crank mid and High tones up much louder before you saturate the speakers. Wattage wise the bass frequencies are probably producing the same wattage when the speakers begin to fart but because our hearing is non linear (and probably a guitar cab isn't tuned to produce allot of bass, we don't hear the bass as being as loud as guitar.

            The bottom line on this graph shows what I'm talking about. The threshold of hearing at around 1~3K is extremely low because our ears are sensitive to those frequencies. If you follow the curve to the left you need about 70 decibels of low frequency just to begin to hear those frequencies.

            Bass farts the speaker out because you need so much more volume to hear it well. The guitar sounds much louder because its in those mid frequencies are ears are sensitive to.


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            • #7
              These curves can help you understand how different amps produce different responses.

              Here's a Marshall Vs Fender. The frequencies are dipped in the middle to flatten out the instruments response and make it sound linear to our ears. Marshall has a higher "Female" voice dip compared to Fenders Lower "Male" voice dip



              Fender EQ controlls









              Marshall -








              A bass amp is going to have its EQ control contours shifted over to the left

              This is from a Traynor amp. The bass knob contours the bass between 40hz . The mids are countoured in the 500Hz range and Treble is 2K and above. Looks like the treble may shift the mids a bit as seen by the Green vs Red line. That's pretty common with Tone stacks using basic Caps and Resistors.



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              • #8
                Originally posted by WRGKMC View Post
                . . . A bass amp is going to have its EQ control contours shifted over to the left . . .
                Likely but it also depends on the amp. Here are the specs for the OP's Rumble 500:
                TONE CONTROLS:
                BASS:
                ±15dB @ 80Hz
                LOW-MID:
                ±12dB @ 280Hz
                HIGH-MID:
                ±12dB @ 1.2kHz
                TREBLE:
                ±15dB @ 10kHz
                The "Low-Mid" is the only one that looks like it's bass specific. According to the manual, the controls on my SWR are centered at 80Hz, 800Hz, and 5KHz. So the controls on both bass amps look like they'd behave pretty much the same as on the Marshall guitar amp in your illustration.
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                • WRGKMC
                  WRGKMC commented
                  Editing a comment
                  You're forgetting the impact of speaker response curves and how those broad ranges are limited by them.

                  The Marshall has a wide bass notch that affects frequencies all the way up to 200hz. It doesn't matter if it affects frequencies in the sub bass ranges, The guitar speakers aren't going to reproduce them anyway. The speaker itself produces a high pass filter in the bass ranges and a low pass filer in the high frequencies.

                  What you do want to look at is the first order harmonics which are the natural sounding bass frequencies of a string. (not the sub harmonics or the primary note)

                  As I've mentioned dozens of times before. What we hear as normal string tone is the first harmonic, not the fundamental note. You don't seem to believe me on that or neglect its impact. Even on your earlier graph it shows the guitar rolling off to nothing below 100hz on a guitar. 100Hz and below begins the sub harmonics for guitar and boosting 80hz will only produce mud tones. Bass guitar rolls off to nothing below 80hz and even if you did push the 41Hz primary you'd only "feel" it compared to the upper harmonics which can be heard by the ears.

                  The Primary frequency is used to warm the tone a bit but you can filter any/all frequencies below the first harmonic and the instrument will still sound normal to most peoples ears. (This "is" done on most recordings to minimize masking, provide separation between bass and guitar, and to conserve power)

                  A low E bass string has a primary frequency of 41 hz but the EQ is centered very close to the first harmonic of 82 Hz not 41 hz. (That should tell you something right there)

                  An amp "head" (minus the speakers) is going to amplify all frequencies from 20hz up to 10K or more because the components are full frequency. Where you place the filters within that frequency range is going to focus the power peaks.

                  When you superimpose both the speakers frequency response over the amplifiers frequency response range, The speaker acts as a band pass filter which limits highs and lows beyond the instruments range.

                  Add to that a pickups response curve and the actual notes the strings produce and a bass amp targets frequencies an octave below a guitar more efficiently then a guitar amp would and vice versa.

                  Unless a bass amp has a horn you wont be hearing anything as high as 10Khz from the amp. The upper mids are at 1.2K which is OK. (800hz is where you hear finger picking tone from bass strings)

                  1.2K on guitar is in the lower mid range. Upper mids is between 2~4K. That doesn't sound like its a big shift in frequencies but the ears can discriminate very small changes in the mid bands because that's where they are most sensitive to changes.

                  The Treble on the rumble boosts everything above up but it doesn't matter. The bass speaker is going to roll off everything above a certain point. (4K just a guess but its likely close) It doesn't matter is the amps Treble can vary frequencies up of 10K, its not going to be heard anyway.

                  But that treble boost does have its benefits. Everything between 2K to the speakers upper 4K limit will be varied including its slap frequencies in the 2~3K range (that's extremely bright metallic tone for a bass)

                  It also create a very steep drop off at 4Khz instead of a gradual roll off. (much like a parametric filter can) This gives the strings a sharp attack tone up to the edge of the speakers upper frequency limit, instead of a gentle roll off which blunts that edge. This is good too because the nasty high frequency metallic string noise and amp hiss is removes above 4K by the speaker, and keeps the instrument out of the guitars high frequency ranges of 5~6K (which also get rolled off above by their speakers.

                  Anyway this is all kindergarten stuff to music. They move the tone stacks down an octave to target an instrument that's tuned an octave lower, and use speakers that are more efficient at those lower frequencies. Most bass amps (and their speakers) roll off the higher guitar string harmonics and make it sound like it has a blanket over the sound.

                  If this wasn't so, guitarists and bass players would use the same amps and just use different speakers.
                  Last edited by WRGKMC; 03-10-2016, 10:01 AM.

                • DeepEnd
                  DeepEnd commented
                  Editing a comment
                  The fundamental of the open A on a guitar is 110Hz, well within the 100Hz and above range. We don't know what chord was being played in my example, which would also make a difference. There are peaks at a tad above 90 Hz and a tad below 200 Hz, which would correspond with F# (92.5 Hz) or maybe G (98 Hz).
                  FWIW, there is no such thing as a ''first harmonic.'' There's a second (2 X the fundamental) and a third (3 X) and a fourth (4 X), etc. but the ''first harmonic'' is the fundamental. Sure, the second harmonic dominates the fundamental but it's there, which you seem to be ignoring. I've seen YouTube vids of output measured from miked cabs while the guitarist was playing (and you probably have too) and there was plenty of energy 'way down to the fundamental range, so the notion that the speaker won't reproduce them is false. The OP's amp has a tweeter so it will indeed reproduce higher frequencies easily.
                  In any event, you said ''A bass amp is going to have its EQ control contours shifted over to the left'' which isn't the case.

              • #9
                My mistake on the harmonics. I meant to say second harmonic.

                You don't have it right on the rest of it however. Prior to the mid 60's/70's allot of bass amps were beefed up guitar amps and simply had beefier speakers, power supplies etc.

                From then on nearly all manufacturers modified bass amps to target the bass strings better. If you look at your tone stacks in amps and were to actually test them you'd have some clue to what I'm talking about.

                This circuit is one of the easier ones. The bass channel uses a .1uf cap for bass instead of the normal channels .047 cap. Because of that one cap the bass channel both the treble and bass are shifted to lower frequencies more suitable for bass guitar. There is also an additional deep switch which adds another .1uf cap for even deeper bass response and less treble frequencies.

                If you understand what tone stacks are and what they do, to the signal you'd understand how bass amp tone stacks are more in tuned with bass strings then guitars.

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                • #10
                  Originally posted by WRGKMC View Post
                  . . . If you understand what tone stacks are and what they do, to the signal you'd understand how bass amp tone stacks are more in tuned with bass strings then guitars. . . .
                  I know what a tone stack does, thanks. What I understand is that not all bass amp tone stacks shift the frequencies. If I can trust the specs, the one in the OP's Fender Rumble 500 doesn't and neither does the one in my SWR. What I said originally is that it's "Likely but it also depends on the amp." This is a qualified statement that takes the facts into account. You made a blanket statement that doesn't and it's not necessarily true. You've done this before and as long as you keep doing it I'm going to keep challenging your assertions. Finally, Traynor says the YBA-1A in your last graph was "also good for guitar" (http://traynoramps.com/legacy/vintage/product/yba-1a/). We were discussing whether you could play a guitar through a bass amp and Traynor says yes.
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                  • #11
                    Geez, so many words!!!

                    Using a guitar AMP for bass is not a problem as far as damage. I think all here agree on this. Regarding EQ/tone, where the controls are centered only changes how the sound is contoured. One amp set a certain way will sound *different* than another amp. Whether this difference is "good" or "bad" is totally subjective to the listener. That's all.
                    "If you don't know where you are going, you might wind up someplace else" - Yogi Berra, 1925-2015

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                    • #12
                      I once played a guitar though my bass amp and my cat died.



                      note: I don't even own a cat.
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                      • #13
                        Originally posted by Craig Vecchione View Post
                        Geez, so many words!!!

                        Using a guitar AMP for bass is not a problem as far as damage. I think all here agree on this. Regarding EQ/tone, where the controls are centered only changes how the sound is contoured. One amp set a certain way will sound *different* than another amp. Whether this difference is "good" or "bad" is totally subjective to the listener. That's all.
                        Sorry but the original question was about using a bass amp for guitar, not the other way around.
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                        • Craig Vecchione
                          Craig Vecchione commented
                          Editing a comment
                          Yeah I meant to write, "and vice-versa" but with all the dissonance and controversy over tone centers I plum forgot!

                        • DeepEnd
                          DeepEnd commented
                          Editing a comment
                          S'okay. I knew what you probably meant. It's easy to get disconfabulated in the midst of all this silliness.

                      • #14
                        FYI this has been an informative and entertaining thread. Thanks everyone!
                        __________________________________________________ __________________________________________________

                        It's funny how nowadays the only decent metal around is the theme music for a cartoon that makes fun of metal bands.

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                        • #15
                          Just from my brief experiences with it, plugging a guitar into a bass amp can give a pretty good jazz or old school blues tone but other than that its just not meant for the frequencies of a guitar pickup so i don't think you could ever get a great tone out of it even if it is possible

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