25k Pots for Active/Buffered signal, tone suck?

middlepillarpath

New member
Messages
7
It's well documented the effect that various potentiometer values have on tone for a passive, high-impedance signal.  250k pots allow more of the high-end to get rerouted to ground, 500k allow less and are brighter, 1m brighter still, etc. etc.

My question is - when using an active/buffered signal such as one with EMG pickups or coming out of a preamp, do pots have the same effect? Would a 25k tone pot or 25k volume pot result in a darker signal than if I just left them out of the circuit?

Thanks!
 

mayfly

Senior member
Messages
8,228
Depends on where you intend to install them in the circuit, and the driving impedance at that point.  If it's after the preamp, and if that preamp has a low output impedance (which it should) then no.

just for my information, which preamp are you going to use?  The reason why I ask is that the volume / tone pots are typically designed into the circuit and the manufacturer typically recommends a value.
 

middlepillarpath

New member
Messages
7
Mayfly said:
Depends on where you intend to install them in the circuit, and the driving impedance at that point.  If it's after the preamp, and if that preamp has a low output impedance (which it should) then no.

just for my information, which preamp are you going to use?  The reason why I ask is that the volume / tone pots are typically designed into the circuit and the manufacturer typically recommends a value.

Thanks!

In this instance I was considering taking a single-pickup instrument and running the pickup directly into the 1m impedance input of a Bartolini buffer-only preamp, and then coming out of that into a 25k volume and 25k tone pot.

Additionally, I was also curious about the idea of adding 25k tone pot to a Stingray bass after the Stingray preamp just to have the added versatility of a traditional tone roll-off in addition to the preamp EQ.

But in both of these instances, my concern was "darkening" the signal in the same way that adding a 250k pot would do to a passive circuit
 

stratamania

Senior member
Messages
9,205
Personally the difference of pot values with passives I would say is not a thing with actives and probably it would be best not conflating the two.

EMGs are designed to work together with 25K pots and they have plenty of clarity. Actives are not going to "suck tone" quite the opposite as they are also designed to drive a signal through long cables and effects without the type of "suck" you may experience with passives in such a set up.
 
S

swarfrat

Guest
Yeah - the high frequency bleed is because of the high impedance circuit, big honking inductor, and capacitance. An amp with a 3.6k output impedance isn't really going to care whether you use a 25k voltage divider or a 500k voltage divider. If you have a passive tone control though the capacitor needs to be sized to the pot.
 

TonyFlyingSquirrel

Senior member
Messages
4,243
If anything, EMG’s have “more tone” in that inductance is not an issue with them.  Inductance is where the tone suck comes from because overwinding a pickup loses more high end the higher you go.  Actives are basically underwound pickups, which by default have more clarity and detail to them by natural science.  Add the preamp/buffer to bring the output level back up to match that of overwounds/height output passives and you have a pickup that has just as much output, with little or no tone loss.  Look at it in a scenario similar to gain staiging on a mixing console and using mic preamps.
 

JohnnyHardtail

Senior member
Messages
319
For the Volume pot, it will not affect the tone.  It is different from passives.

For the Tone pot.  Changing the tone pot value between 25k or 50k tone will have a subtle effect.  If you delete the tone pot you will end up with tighter, less bassy tone.  For a more precise tone control, EMG sell a "true active" tone control called VLPF-G.  There is also RPC control which is a "spectrum tilt" parametric control to give a brighter tone.
 
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