Active preamp with bypass and passive tone control

[Guest MoJo]

Loving my Ibanez BTB1605 with one minor niggle. There is no passive tone control when the active preamp is bypassed, so although you can use the bass passively, the tone is effectively wide open. Does anyone manufacture an active preamp that can be bypassed with a passive tone control or does anyone know of an electronics genius that could retrofit a passive tone control to my existing electronics?

[fretmeister]

Whatever is in the Sandbergs does that.

When in passive mode the Treble becomes a passive tone, just reducing it from te centre point.

I think some of the East preamps have an option to have a passive tone control on it too.

[GreeneKing]

John East's new UNI-pre's have this very facility. The blend is double pots and therefore works properly both active and passive. In passive on the 4 and 5 knob unit there is a separate passive tone that works in active too like on my ACG.

Edited to correct knob numbers.

Edited December 20, 2016 by GreeneKing

[molan]

Sadowsky have had a clever 'vintage tone control' for quite a while. Works in both active and passive modes.

Available as a complete bolt in fitting or just as controls and wires

[Rich]

The preamps in the Sire V7/M7 basses have a passive tone control. Much like the Sadowsky, it works in both active and passive modes.

[NickD]

My Glockenklang 2 band has that.

[pete.young]

Likewise the 2-band Nordstrand that I retrofitted to my Bass Collection. I can't imagine ever using passive mode though, the difference is night and day.

[Guest MoJo]

[quote name='molan' timestamp='1482243991' post='3198768']
Sadowsky have had a clever 'vintage tone control' for quite a while. Works in both active and passive modes.

Available as a complete bolt in fitting or just as controls and wires
[/quote]

Sounds just the job

[thodrik]

[quote name='MoJo' timestamp='1482249340' post='3198865']
Sounds just the job
[/quote]

I would agree. Though I have had a Metro for about seven years now and have only started using the 'vintage tone control' knob this week!

[Paul S]

The old Westone Thunder active basses used to have a tone knob that worked whether active or passive. Great feature. I am sure the Westone info pages would have a link to the wiring diagram. Page is here: [url="http://www.westone.info/wiring.html"]http://www.westone.info/wiring.html[/url]

[Guest MoJo]

[quote name='Paul S' timestamp='1482251151' post='3198892']
The old Westone Thunder active basses used to have a tone knob that worked whether active or passive. Great feature. I am sure the Westone info pages would have a link to the wiring diagram. Page is here: [url="http://www.westone.info/wiring.html"]http://www.westone.info/wiring.html[/url]
[/quote]

Cheers Paul

[dannybuoy]

Glockenklang. Sandberg use them, however my particular Sandberg Basic does not have a passive tone control in bypass!

[GreeneKing]

I've just ordered a John East Uni-pre - 3 knob variety for the GMR. It's really 3 knobs and an active/passive switch. This thread helped me appreciate that with the 3 knob model I'd lose the passive tone control so I've got back to John to change to the 4 knob model. The cavity is huge and an extra hole is needed either way.

Fans of the East U-Retro may like to cast an eye over the feature set of this replacement Uni-Pre. Not only is it modular it also has a whole lot more versatility, for the same price.

http://www.east-uk.com/pdf/UNI-PRE-4K-U-RETRO-DX-4K-COMPARISON-01-2015-03-10.pdf

Awesome!

[samhay]

>Does anyone know of an electronics genius that could retrofit a passive tone control to my existing electronics?

Do you have much room in the control cavity?
If so, it would be easy enough to replace one of the tone controls with a dual-gang pot and wire the second gang as conventional tone control. I expect you would also want to bypass this when the preamp is engaged, which may also involved replacing the switch. This won't work if you don't have any room to play with, but is fairly straightforward if you do (and I am not even a genius). The rub is that your preamp almost certainly won't use 250k tone pots (looks like 50k or 100k), so you will lose some range (brighter settings) as finding dual gang pots with 2 different resistances is not easy.

[Dood]

[quote name='NickD' timestamp='1482244851' post='3198788']
My Glockenklang 2 band has that.
[/quote]

Yup I have a 2 band and the three band circuit featuring said function. A very good stock circuit too.

I'd also recommend John East, nice preamps from an even nicer guy!

[tauzero]

I'm pretty sure the Delano Sonar 2 has that - never take mine out of active though.

[paul_5]

[quote name='samhay' timestamp='1482256818' post='3198999']
The rub is that your preamp almost certainly won't use 250k tone pots (looks like 50k or 100k), so you will lose some range (brighter settings) as finding dual gang pots with 2 different resistances is not easy.
[/quote]
It's fairly easy to make one, buy a dual ganged pot of one of the values and a single gang pot with the other. Take the back off both pots and replace the carbon trail on ONE of the dual gang wipers with the second value (from the single pot) and reassemble. You'll need a flat blade to prise the clasps off the back and some pliers to refasten them, but other than that it's fairly easy. 😄

[samhay]

^Fair point. I keep discounting this as it doesn't work very well with the cheap 16mm pots I often use for those 'little boxes full of Steve's lovely bits'. (ooh arr)
Creeping towards genius territory now though.

[molan]

[quote name='thodrik' timestamp='1482250890' post='3198887']


I would agree. Though I have had a Metro for about seven years now and have only started using the 'vintage tone control' knob this week!
[/quote]

It's my most commonly used control on my NYC, lol

I use it in active mode to make broad adjustments to my tone. Wide open for modern stuff and rolled back for older songs.