Guitar Signal Path

[BlackhawkRise]

I know a decent bit about guitar circuits, and I'm wondering if I got this all accurate. We we will leave effects out for the mean time.

The signal comes from the guitar pickup producing frequencies from about 80 Hz up to maybe 16 kHz, depending on the pickup. The potentiometers load this down a small amount. At this point the signal is bright thin and useless.

It passes to the amplifier where there is an input gain into a preamp, and then it to a tone stack section, then it goes to the power amp then we get a master volume. Obviously all amps are going to be different here, but the big take away is the power and preamp distort to some extent whether you have the gain high or low. This warms up the treble frequencies and as gain goes up you lose more bass, stopping it from getting fuzzy. A lot of this frequency loss isn't strictly in the audible range, but it effects the way the electronics can handle the audible range.

After this the signal goes into a cabinet housing speakers that in any other application would be large enough to be subwoofers, filtering the guitars frequencies down to no more than 8 kHz and increasing the bass response in proportion to the rest of the signal.


This is very simplified, but am I getting it right?

 

[beaubrummels]

I thought the frequencies produced by a pickup were more narrow than 80-16k. Every frequency response plot I've seen taken directly off a pickup doesn't have quite that range.

I believe everything electronic in the path has some impedance or resistance to it (depending on if the signal is alternating or direct current). High frequencies are more affected by that.

I don't know that pre amps and power amps always distort. Usually it takes some kind of imbalance in the circuit or signal to get them to distort. Sometimes that is by design, but it's not inherent in the base design of an amplification circuit. Theoretically, amplification of a signal is just that: an increase in what's already there with nothing added and nothing taken away.

Everything in a passive system is lossy, so I wouldn't characterize a shift to a warmer sound at the speaker as an increase in bass response but more of a loss in highs creating that perception. I guess you could count the resonance of the cabinet, coupled with any ports, as further reproducing and exaggerating the bass end of the sound.

That's my understanding anyway. (Cue the physics majors and EE Engineers to elaborate in technical ways no one can understand.)

 

[Hiwatts and Gibsons]

I have through reading and practice come across the answer to this problem for me.

First, after my non buffer friendly pedals such as the various Range Master, Tone Bender, and Fuzz Face types of pedals I have owned I generally place a high quality buffer in the signal change to provide a solid strong signal through my modulation pedals and 20- of cable from my pedals to my amps.

Personally I like using a pedal switcher with a flexible buffer. On my Rocktron Loop 8 Floor I can place the buffer anywhere in the signal chain thanks to its isolated active input and output jacks. I run my non-buffer friendly pedals in the loops before it, then patch the output of the last non-buffered loop into the active input, and the active output goes to the next pedal loop on the back.

I have a/b'd the tones with all the pedals off, and only the switcher's active buffer and my two cables in the chain with the sound of the guitar plugged directly in via a quality homemade 12' foot canare cable with Neutrik plugs, and could not tell the difference at all in either quality of tones, high frequency content, or the interactions between my guitar pickups and the amp's input stage, and I am a volume and tone knob riding SOB.

If I am not using any modulation pedals my signal chain is short, generally consisting of a Range Master type, an Octaver, and a Fuzz. In that case my Range Master is first in the chain, and set with the Tone and Volume cranked, so getting a strong signal without loss of upper frequencies is never a problem.

The only times it is not on are when I am going for a huge thick fuzzed out doom type tone, and the highs are not missed, or when pairing the Octaver with the Fuzz, and the octaver has a very strong output when the levels for the sub, octave down, octave up, and/or clean level are set anywhere above noon so it compensates for the strong output the Rangemaster would normally add.

Either way high frequency signal loss doesn't ever seem to be a problem for me, even with relatively medium to medium hotish output single coils.

 

[jeremy]

i dont think the signal from the guitar is thin necessarily, but it is very low output. hence, we use amplifiers. a standard tuned low e string on a guitar is 82hz. i dont know how high the harmonic content goes but 16k seems high.

It passes to the amplifier where there is an input gain into a preamp, and then it to a tone stack section, then it goes to the power amp then we get a master volume. Obviously all amps are going to be different here, but the big take away is the power and preamp distort to some extent whether you have the gain high or low. This warms up the treble frequencies and as gain goes up you lose more bass, stopping it from getting fuzzy. A lot of this frequency loss isn't strictly in the audible range, but it effects the way the electronics can handle the audible range.

there are typically a few gain stages on a guitar amp channel. even a clean channel will usually have at least two, and some high gain amps might have five. the tone controls are usually some where in the middle of the gain stages, but could be after them too i guess. a master volume is before the power amp stage. if its after, its most likely an attenuator of some kind.

if you look at a amp signal on a oscilloscope you can see the wave form. a perfect sign wave should have almost no distortion and there are plenty of amps that can do this. having a lot of distortion doesnt necessarily cause you to lose bass or treble, that depends on the amp and speaker.

 

[htrd]

The signal comes from the guitar pickup producing frequencies from about 80 Hz up to maybe 16 kHz, depending on the pickup.

Passive pickups are the second order low-pass filters. When loaded they usually have their resonant peaks around 2-5KHz. The only pickups I remember to have something above the 10KHz region were EMG SA. Maybe there are more similar pickups but I haven't tried them all

Everything else you have covered right. Signal from the guitar goes into the preamp section where it is filtered, amplified (a lot if we are talking about the hi gain amps), filtered again, goes into the tonestack (usually it is at the end of the preamp section, but not always). Afterwards - to the power amplifier, where it is amplified and sent to the guitar speaker cab which has the most impact on your tone, working as a final EQ, cutting the lows and the highs, sculpting the mids.

 

[ehdwuld]

Yall forgot the cable

A 20 foot cable looses high dramatically

I have a musicians friend braided 20 foot cable
And an 18 foot George L cable

The MF is noticeably darker
Noticeably