I HATE Blend Pots!

[sunbeast]

What makes MN and AC pots different?

I may sound dumb trying to explain something I don’t fully understand, but this is the internet so I’ll be confidently incorrect. I do know that MN pots blend better when moving slightly off center.

It has to do with how they taper the volumes. An A series pot tapers in a linear way like this-

View attachment 5436384

Whereas an M series pot tapers like this-

View attachment 5436385

I’m sure it has something to do with the M series having the same volume values in the center detent instead of the A series being reversed. On the Fat Bass Tone site they say that the M series blend pots are used in Aguilar preamps and the A series are used in Nordstrand preamps. Like I said, I don’t fully understand the technical part of it, but I like the M series more.

Blend pots consist of two separate pots that are adjusted using a single shaft. An AC Blend pot uses two standard audio-taper pot elements with one of them reversed (the "A" in AC is for the standard Audio taper element, and the "C" is the common distinguisher given to a reverse-Audio taper), so when you are turning one pot up you are turning the other pot down- the problem with this arrangement is that in the middle point (center detent) both of the volumes are turned down to a degree, the only way to max out either side is to turn the control all the way to one side or the other (at which point you've muted the other pickup). At any point you aren't completely soloing wither pickup then you are turning it down when using an AC Blend (which in a passive circuit affects both volume and tone via loading to ground- the tone gets darker).
An MN taper blend pot is a different approach that has all the resistance in one half of the pot's rotation inside each of the two pot elements (the two sides are reversed from each other, as with the AC pot) with the resistance at either side being in linear taper (the "M" in this case describing a half-linear taper plot and the "N" describing its reverse)- this arrangement means that in the center detent both volumes are truly all the way up and one of the two sides stays at 100% as you turn it down from the center position on either side. This means each pickup is at 100% throughout its own side of the blend rotation and is only attenuated once you cross the center detent into the other half (which in a passive circuit means you get both slightly more volume and slightly brighter tone in the middle position than a comparable AC taper blend).

If the original blend in the Thunderbird was an AC then that would partially explain the change in tone since the middle position of an AC Blend adds extra loading to the circuit (and drops the volume to a degree). Any other tonal change would probably be a result of the value of potentiometers used- if the original blend was a 250K and you used 500K stacked volumes then the overall loading of those pots on the circuit would be halved from the blend control for a brighter tone while a 500K MN Blend should sound pretty much the same as stacked 500K volume pots with the blend centered and volumes at 10 (or with either side soloed).

I also tend to prefer dual volumes to a blend in a passive form- when using two volume pots you are doubling the amount of useful taper, whereas the useable taper of a Blend control is found on a very tiny turn of the control. I also virtually never turn the volume down on a passive bass due to the effect it has on my tone, and will usually have a pedal I can turn down instead if necessary. I prefer an active/buffered blend control to anything else, but I don't want to have batteries in most of my basses so dual volumes is often the best choice for my tastes.

 

[Rib 13]

I like blend pots and I cannot lie

I sang this in my head as I read it.....thank you: I needed that

 

[Jett Litt]

Just so you know - most active basses use a passive blend control.

I'll clarify by stating fully active, pickups and preamp. A buffered blend.

 

[secondbestcody]

Blend pots consist of two separate pots that are adjusted using a single shaft. An AC Blend pot uses two standard audio-taper pot elements with one of them reversed (the "A" in AC is for the standard Audio taper element, and the "C" is the common distinguisher given to a reverse-Audio taper), so when you are turning one pot up you are turning the other pot down- the problem with this arrangement is that in the middle point (center detent) both of the volumes are turned down to a degree, the only way to max out either side is to turn the control all the way to one side or the other (at which point you've muted the other pickup). At any point you aren't completely soloing wither pickup then you are turning it down when using an AC Blend.
An MN taper blend pot is a different approach that has all the resistance in one half of the pot's rotation inside each of the two pot elements (the two sides are reversed from each other, as with the AC pot) with the resistance at either side being in linear taper- this arrangement means that in the center detent both volumes are truly all the way up and one of the two sides stays at 100% as you turn it down from the center position on either side. This means each pickup is at 100% throughout its own side of the blend rotation and is only attenuated once you cross the center detent into the other half.

If the original blend in the Thunderbird was an AC then that would partially explain the change in tone since the middle position of an AC Blend adds extra loading to the circuit (and drops the volume of both sides to a degree). Any other tonal change would probably be a result of the value of potentiometers used- if the original blend was a 250K and you used 500K stacked volumes then the overall loading of those pots on the circuit would be halved from the blend control for a brighter tone while a 500K MN Blend should sound pretty much the same as stacked 500K volume pots with the blend centered and volumes at 10 (or with either side soloed).

I also tend to prefer dual volumes to a blend in a passive form- when using two volume pots you are doubling the amount of useful taper, whereas the useable blend taper of a Blend control is on a very tiny turn of the control. I also virtually never turn the volume down on a passive bass due to the effect it has on my tone, and will usually have a pedal I can turn down instead if necessary. I prefer an active blend control to anything else, but I don't want to have batteries in most of my basses so dual volumes is often the best choice for my tastes.

Yeah, I guess if you want the long explanation this is what you want. XD

 

[sunbeast]

Yeah, I guess if you want the long explanation this is what you want. XD

The important distinction between the MN and AC approaches is that the MN only affects the volume of one pickup when turning the pot either direction from the center detent (in the graph you posted, you can see one of the colored lines of the MN stay full on the top of the graph while the other gets turned down). The two graphs you posted are showing different things so it makes it hard to visualize the difference. This is a graph of an AC taper pot that shows the same things as your MN taper plot (so you can see that center position exists only partially through each volume sweep and that both side's volumes change across the entire sweep):

 

[secondbestcody]

The important distinction between the MN and AC approaches is that the MN only affects the volume of one pickup when turning the pot either direction from the center detent (in the graph you posted, you can see one of the colored lines of the MN stay full on the top of the graph while the other gets turned down). The two graphs you posted are showing different things so it makes it hard to visualize the difference. This is a graph of an AC taper pot that shows the same things as your MN taper plot (so you can see that center position exists only partially through each volume sweep and that both side's volumes change across the entire sweep):

Yeah, you have a way better understanding of it than me. I was just being cheeky.

 

[MoireBass]

That might be due to the pot itself being made differently. They are resistors and the material used to make them can change the tone of an instrument. I have done this with a few instruments and have been blown away by the differences. With that said, really dissapointed by the tone difference from Alpha pots to Bournes.

Please explain this to me. Since resistors are frequency-independent at audio frequencies, what's the mechanism that would cause this?

 

[kgbeast]

Please explain this to me. Since resistors are frequency-independent at audio frequencies, what's the mechanism that would cause this?

Pots can be made with carbon composite or conductive plastic where conductive plastic would induce less noise than carbon composite. That said, the difference is not audible at the resistances and voltages we are discussing, but perhaps can be measured with oscilloscope if one really tries. Plastic film would last longer and feel smoother. As for one type of pots killing tone compared to another type... it is an argument for the benefit of woodlisteners and farfaronnes. Yes CTS pot can last longer than Alpha, but it is debatable, just like the orange drop capacitors blow away mylar capacitors.

 

[kyral210]

I'll clarify by stating fully active, pickups and preamp. A buffered blend.

I tried to find a buffered blend, but I couldn’t find one ☝

 

[sunbeast]

I tried to find a buffered blend, but I couldn’t find one ☝

This one works with passive pickups: Invalid Link Removed I think you actually made a thread asking about this previously and a number of us recommended the EMG ABC (“Active Blend Control”) to you. It is probably the most convenient option out there. Bartolini also makes a few modular buffered blend options as do a few others

 

[ctmullins]

The best thing I've tried is just wiring the pickups to individual concentric pots, then going from there to a master volume pot, then on to the tone control. You can adjust pickup balance much more precisely, and it sounds much better. I have found that a B500k pot works great as a master volume in most cases.

FYI, this is electrically identical to a blend pot (wired in the normal way, with ground attached) and a master volume.

Different component values and tapers can affect the circuit behavior, to be sure. And you have a point about the separate volume controls allowing the full rotation for fine tuning.

 

[Standalone]

I like VVT on single coils. But prefer BVT on humbucker or dual P.

And yes, my mid eighties Ibanez are Blend/Volume/Tone — which I like.

 

[kgbeast]

I'll clarify by stating fully active, pickups and preamp. A buffered blend.

If you have active pickups, buffered blend or active blend is unnecessary. It will only reduce the battery life and possibly add some noise even if minimal. A properly sized, 25k-50k MN blend pot is all you need really.

 

[mr80htz]

Please explain this to me. Since resistors are frequency-independent at audio frequencies, what's the mechanism that would cause this?

The material the signal passes through creates variations in tone and the value of the resistor literally resists the flow of electrons to varying degrees so different values allow different levels of signal through. For example, carbon comp resistors (bigger brown ones) change the signal to be a little darker/less high end. Blue metal film resistors will produce a slightly brighter signal when compared to the carbon comps. I suppose there's someone out there who would say this is silly but not to my ears and those of pedal builders like Analogman Mike P.

 

[jglunt]

FYI, this is electrically identical to a blend pot (wired in the normal way, with ground attached) and a master volume.

Different component values and tapers can affect the circuit behavior, to be sure. And you have a point about the separate volume controls allowing the full rotation for fine tuning.

I have a friend who is an audio/video engineer and very accomplished. He tells me the same thing, and I agree as long as that word "electrically" is in there, as it is. But I use my ears, and I can honestly say that every taper of blend pot that I tried (A, B, or MN) and every value (100k, 250k, 500k), grounded or ungrounded made my previously very beefy and punchy G&L SB-2 sound thin. It turned a lion into a kitten. Even though I wield a pretty good soldering iron and can follow a wiring diagram, I am not trained in electronics enough to know why this is the case, but the sound was noticeably altered using V-B instead of the original V-V.

 

[gregmon79]

My Thunderbird always sounded dull, even after new custom wound pickups. It had a CTS passive blend knob. Then fate intervened.

I bashed my blend knob so hard it broke. Damn! Ok, I’m rewiring the pot anyway, why not try a stacked knob? So I did. Jesus Christ the tone is better!

it’s like adding new strings. The definition is more pronounced and there’s more growl. I’m so happy that I have made this mod, and confirmed I HATE blend knobs for how they destroy tone and ‘feel’!

View attachment 5436131

is that a stacked V/V pot?

I recently got an epiphone embassy bass and I’m not a fan of the blend either. Thinking I may do what you did. So is that a V/V stacked pot?

 

[kgbeast]

is that a stacked V/V pot?

I recently got an epiphone embassy bass and I’m not a fan of the blend either. Thinking I may do what you did. So is that a V/V stacked pot?

You do not need stacked knob if you do not want the blend pot. You make the volume pot exclusively neck volume, then install another the same pot instead of blend pot and wire it as bridge volume.

 

[jglunt]

is that a stacked V/V pot?

I recently got an epiphone embassy bass and I’m not a fan of the blend either. Thinking I may do what you did. So is that a V/V stacked pot?

Here's a link to a typical jazz bass wiring diagram. I suggest re-wiring the Embassy like this, so instead of the three pots being wired V-B-T as it is now, you'll make them V-V-T, like a jazz bass. I recommend you buy two new pots for those volume pots. With those Epiphone Probucker pickups on that bass, I recommend B500k pots. If you feel uncomfortable with doing the wiring, any luthier can wire it that way.

Jazz Bass Style Wiring Diagram

 

[gregmon79]

Here's a link to a typical jazz bass wiring diagram. I suggest re-wiring the Embassy like this, so instead of the three pots being wired V-B-T as it is now, you'll make them V-V-T, like a jazz bass. I recommend you buy two new pots for those volume pots. With those Epiphone Probucker pickups on that bass, I recommend B500k pots. If you feel uncomfortable with doing the wiring, any luthier can wire it that way.

Jazz Bass Style Wiring Diagram

I'm pretty comfy with the wiring myself. I get unsure when I start schematic googling haha so thank you, I appreciate that! Sometimes I just need the correct schematic and I'm golden. Great suggestions.

 

[kyral210]

This one works with passive pickups: Invalid Link Removed I think you actually made a thread asking about this previously and a number of us recommended the EMG ABC (“Active Blend Control”) to you. It is probably the most convenient option out there. Bartolini also makes a few modular buffered blend options as do a few others

There’s one video on YouTube of a guy reviewing the ABC. That is me! Past me hated the ABC