Blend/Tone Only - Jazz Bass

[amphlett7]

I'm getting read to re-wire my Mexican Jazz bass after finishing it and want to try something different.

I've had it wired standard VVT and V-3 way switch-T, but neither has worked for me.

I solely use my basses in my home studio, so I rarely have use for the volume control.

Is there reason to wire a jazz bass as Blend/Tone only?

I've heard that because the blend control is effectively 2 volume pots linked in reverse that using one in addition to a volume pot can create an additional load to the pickup.
Would a 250K blend pot be effectively the same loading as a standard VV setup?

Followup question!
Is it possible to treble bleed a blend pot?

Thanks guys!

 

[ELynx]

OK, first post I would check out would be
Ultimate No-load Ungrounded Blend Pot (Pics!)
It has schematics, pictures and user experience.
For your questions:

Is there reason to wire a jazz bass as Blend/Tone only?

I see no specific reason to do so, unless there is not enough holes for a knob. Since blend pot with MN resistance has zero load in "middle" position you will have to put a load resistor in there somewhere, to keep the circuit the same.

I've heard that because the blend control is effectively 2 volume pots linked in reverse that using one in addition to a volume pot can create an additional load to the pickup.

Well, this is how blend works, essentially. In middle position there is no additional resistance, away from it it is added, so output volume of pickup is decreased.

Would a 250K blend pot be effectively the same loading as a standard VV setup?

No, it would not be. Resistance in blend pot is in series, volume pot is a "load" for pickup and act as voltage divider in the circuit. Maybe you are thinking dual volume pot? This is two distinct circuits.

Is it possible to treble bleed a blend pot?

Guess so. Depends on schematic you will use, you can put treble bleed somewhere in. _But_ there you will have to consider a lot more interplay. Any schematic you want to use?

Edit:
Also, with blend pot you cannot dial "off". It always has some signal going out.

 

[amphlett7]

This info is perfect, Thanks! A lot of my questions were based around my misunderstanding of the blend pot.

I see no specific reason to do so, unless there is not enough holes for a knob.

My thinking was that a single blend control would load the pickups in the same way as the two volume pots in a standard Jazz bass circuit.

Since blend pot with MN resistance has zero load in "middle" position you will have to put a load resistor in there somewhere, to keep the circuit the same.

This is interesting to note. It would be possible then to put a variable resistor before the pickups allowing you to choose how to load them (Not entirely unlike the Z switching in the Audere Pre-Amps?)

No, it would not be. Resistance in blend pot is in series, volume pot is a "load" for pickup and act as voltage divider in the circuit. Maybe you are thinking dual volume pot? This is two distinct circuits.

I had read this post in another thread on TB which may have given me the wrong impression.

A blend pot is essentially two volume pots stacked, one normal taper and the other reverse taper. So a blend-master volume system actually has three volume pots total where a volume-volume system has two. This affects the overall impedance of the system, which does technically affect the overall sound. To what degree is arguable - some can hear the difference, some cannot.

From this I gathered that having a Volume and a blend control would be effectively the same as having 3 volume pots.
From your info you say this isn't the case?

Guess so. Depends on schematic you will use, you can put treble bleed somewhere in. _But_ there you will have to consider a lot more interplay. Any schematic you want to use?

Again, the need for a treble bleed was based on my misunderstanding of how blend controls work.
My thought being that having a treble bleed for each of the internal volume controls of the blend pot would result in less loss of high frequencies as each pickup was backed off.

Also, with blend pot you cannot dial "off". It always has some signal going out.

When recording I rarely touch the volume control and more often than not causes more issues for me.

 

[ELynx]

This is how author described it:

OK, after some prompting i finally made a diagram of the whole thing, done in my apparently now traditional goofy MS paint style

View attachment 2779754
it also works just fine without cutting the traces, you still get the smooth blending between pickups and you still avoid extra loading loss from the blend pot; the only drawback is that when you're cranked over to one pickup you still get a slight bit of the other, "off" pickup in the mix. (you don't really hear it though)

if you're a player who mostly shades between the two pickups rather than running either one solo, then this will work nicely without cutting the traces on the blend pot.

I did that mod, and added some more stuff above that.

I am about to add this blend control to my BB415, and while wondering how it works I have thought of a way to add a "bonus" output via stereo jack.
I added a picture of how I see it electrically, and describe it below.

When pot is fully rotated into one or another direction, isolated pickup is essentially connected to remaining pin, via small resistance (if cut is done in position that allows outer viper to "land").
I want to connect currently not-connected pins together, load them into 220k resistor to emulate usual volume pot wide open, and connect that to ring of TRS jack.
When mono jack is inserted, pickup is grounded from both ends. When stereo jack is inserted "isolated" pickup is actually on ring.

Since I already use no-load pot (made in same manner) for tone, I expect signal to be pretty consistent in stereo with tone wide open.

Will try to do it, and post results.

Here is more "graphical" way, I found it easier for myself to think of it in this mixed electric-mock-mechanic manner.
https://images.talkbass.com/attachments/photo5443024011865991323-jpg.2896257/

Here is "three volumes" sketch. There are three variable resistances in circuit, although I would not call all them volumes.

 

[RobbieK]

From this I gathered that having a Volume and a blend control would be effectively the same as having 3 volume pots.
From your info you say this isn't the case?

No, you are correct. A blend pot, wired as standard is electrically identical to two volume pots. (Also wired as the standard Jazz bass way - IOW with the pickups going to the wipers.) So a blend and a vol does add more of a load than two volume pots. However, as others have said, a blend pot still works just fine without connecting to earth. Disconnecting the earth from your blend pot has been a common mod for around 10-12 years that I can recall. If you put a temporary switch on that earth connection, and switch back and forth, you'll hear a difference. An "unearthed" blend pot plus a volume pot will have less load than two volume pots. (This is when comparing the two vols at full with the blend in the middle.)

There's another thread right now with similar question about a P bass.

I think you are crazy having a guitar in a studio that doesn't have a vol or at least a mute switch, maybe in a home studio it's ok, but I wouldn't recommend it in a bigger studio with session players/producers coming and going.

If you want to reduce the load on a passive bass, try a no-load tone pot. Or yeah the un-earthed blend trick. You can even make a no-load volume pot if you really want. I posted a how-to last year on my little YT channel.

 

[amphlett7]

I think you are crazy having a guitar in a studio that doesn't have a vol or at least a mute switch, maybe in a home studio it's ok, but I wouldn't recommend it in a bigger studio with session players/producers coming and going.

A mute switch I could get behind.
I have literally never had my volume control below 100% unless by accident.
I understand that running the volume lower than 100% rolls off a little high end but I’ve tried and never found it useful.

I’ve not played a session in another studio ever.
The only time I play bass on a recording that’s not my own is when I’m working with a solo artist who doesn’t want to hire an outside artist or if a musician is having an issue.

Everyone has a different situation and I definitely see where you’re coming from.

A mute switch I could definitely use.
Maybe I could incorporate it into something else like a phase reversal or even, if possible, a load or pickup impedance switch.

 

[murphy]

Interesting read
A blend pot on a jazz bass does make more sense than two volume pots....but pretty much the same as having a stacked V V pot