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Post by pablogilberto on Jan 19, 2020 21:31:01 GMT -5
Passive electronics usually use 250k to 1Meg pots for volume and tone controls.
Active electronics usually use, 10k, 25k, 50k and 100k.
Sometimes, I also see some active combine low value pots like 10k to 50k, to high value pots (250k to 1Meg).
For passive electronics, I understand the effect of changing the values of pots.
Will the effect be the same with active electronics?
If I have a component that is using a 25k ohm pot, and I changed it to 50k, what will be the effect?
Or I cannot simply do this for active electronics?
Thanks
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Post by thetragichero on Jan 20, 2020 1:37:59 GMT -5
the point of active electronics (in my view) besides better onboard tone shaping is the low output impedance. higher value pots with active electronics act like more of an on/off switch than a usable volume control
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Post by Deleted on Jan 20, 2020 4:12:28 GMT -5
G&L active guitars are passive ones plus amp.
Been looking at active for bass guitar like the musician range (another of Mr fender)
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Post by pablogilberto on Jan 20, 2020 6:42:47 GMT -5
the point of active electronics (in my view) besides better onboard tone shaping is the low output impedance. higher value pots with active electronics act like more of an on/off switch than a usable volume control I agree with the tone shaping and the low output impedance. "higher value pots with active electronics act like more of an on/off switch than a usable volume control" - Why does this happen? |
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Post by pablogilberto on Jan 20, 2020 6:43:30 GMT -5
G&L active guitars are passive ones plus amp. Been looking at active for bass guitar like the musician range (another of Mr fender) Sorry I don't get your point here. |
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Post by Deleted on Jan 20, 2020 8:06:41 GMT -5
G&L active guitars are passive ones plus amp. Been looking at active for bass guitar like the musician range (another of Mr fender) Sorry I don't get your point here. That the great and late Mr Fender used active but only we a amplifier than as a active circuit .. liked to passive control the tones than what he did on the musicman bass guitar |
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Post by thetragichero on Jan 20, 2020 9:51:35 GMT -5
@pablogilberto: from a bit of goggling, it is due to the series resistance from the pot (because it's just a variable voltage divider) reacting with a low impedance source
also of note with active pickup systems: since the pot value is considerably reduced, the time capacitor must be considerably increased (i find 100nf at the bare minimum) or else the tone pot acts like an on/off switch
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Post by blademaster2 on Jan 20, 2020 9:58:11 GMT -5
One benefit of active electronics is that the pickup can be loaded less with a higher input impedance feeding the preamplifier (like the 1Meg pots compared to 250k pots on passive electronics), can be shaped as Trag says, and in turn the amplified pickup signal at the output of a preamplifier can be much lower impedance such that you can use lower resistance pots to control the volume (or control it and subsequently buffer it so that a low impedance feeds the output of the guitar and makes the loading effect of cables less influential on the tone).
The drawback is noise and other non-idealities of the preamplifier circuitry in negative feedback topologies (slew rate and other transient response attributes that are the majority of what we call 'tone') and the need to put a battery in the instrument.
Given the subtleties of the tone of a guitar I could never prove it with instrumentation, but my impression from those I have tried is that the sound is okay in an active guitar but there is something missing or changed that I would prefer to use pedals if I want anything other than the passive signal feeding my amplifier.
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Post by thetragichero on Jan 20, 2020 10:43:48 GMT -5
i found adding a preamp to my basses was beneficial for tone shaping as they are generally plugged into a di sent to the mixing console, so being able to adjust bass and treble and have a low impedance output is a good thing
i have one active pickup guitar and that was mainly because i wanted to build a metal guitar. kind of a one trick pony but i like the trick. definitely not as responsive for things besides heavy riffing as my passive guitars
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Post by sumgai on Jan 20, 2020 13:43:40 GMT -5
Boys and girls,
Certainly not the only one, but the very mainest of main reasons that active circuitry was put into a guitar was to elimintate the capacitive effects of the standard guitar cable. A normal guitar cable tends to reduce the higher frequencies. And the longer the cable, the worse the effect. By how much, that's a matter of quality of the cable itself (meaning, made of better components to reduce the capacitance effect), but the effect never goes completely away... not without some help.
Enter active buffering. The necessary words here are "low impedance", and that simply cannot be achieved without help. By definition, a standard guitar pickup is high impedance. (The cutoff between low and high is set at 600 Ohms.) Low impedance pickups can be made, and are still available on a few factory guitars, but they are expensive by comparison to the usual goodies all know and love. Hence, the help needed is to convert a high impedance to a low one, and that means a powered circuit. We usually call this a buffer, even if it might add a bit of amplification.
The net effect, particularly for those using a DI to a Sound Reinforcement system, is that low impedance cables can be run several hundred feet, not just 10 or 15 feet... and they can do so with absolutely no loss (or other distortion) of the signal. Nowadays of course, we have radios to take the place of cables, and they can be had at reasonable expense when you consider the clean stage benefit as well as the signal quality. But for many players, that's still a lot of sets of guitar strings, so they stick with cables.
A buffer doesn't care what kind of cable is connected to its output, it does its magic just fine. Here's a link to JohnH 's thread on buffers:
John's JFET Pre-amps
There are a couple of other links within that thread, you might wish to persue them as well.
HTH
sumgai
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Post by ashcatlt on Jan 20, 2020 14:29:50 GMT -5
Yeah so on a passive guitar the value of the pot does two things that affect tone.
The big one is the way it acts as the R in the LR lowpass of the inductive pickup. Assuming the amp load is big enough, a bigger pot will mean more treble out of this part.
The other thing that happens is that when you turn the V pot down from full, it increases the R of the RC lowpass that is created with the cable. It will be largest right around halfway down. A bigger pot here means less treble when turned down.
It’s a compromise we make with passive guitars and we either live with or t or we add a “treble bleed” which sort of counteracts the the cable loss part. It’s actually a kind of shelving highpass, but we’re not talking about that really ATM.
The output of the active stage doesn’t have the LR filter at all. It actually has an RC highpass instead. Too small of a pot here will mean a loss of bass, but the C is usually specified to be plenty big that any reasonable sized pot will work.
It does, however, still have the cable filter. Assuming that output C IS sufficiently large, we can get away with a much smaller pot so that even turned down to center it’s not cutting off much if any audible treble.
But that of course assuming the pots are on the amp side of the active stage. If they’re on the pickup side - going into the active stage - then you’re back to the passive scenario.
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