hybrid treble control?

BarkerBass · #1 01-08-2010, 06:17 PM

is it possible to mod an existing active preamp so that the treble control boosts when clockwise from the detent but installing a cap so that you get a passive tone control when turning counter clockwise? I know Human Basses have these when in passive mode but I want it just for general use. For reference it's a MIM deluxe jazz from 200 that I intend on modding. I don't understand active wiring and so my basic idea of a plus and a negative wire which is activated when the pot is turned in it's direction is probably wrong but if it were the case then could not a cap be put in place of the negative side?

Any Ideas if this is possible?

**line6man** · #2 01-08-2010, 06:39 PM

It would basically require a dual ganged pot designed so that one pot works from the center to one direction, and the other pot works from the center to the other direction.
They need to be different values as well, one 25K/50K and the other 250K/500K.

I emailed Dingwall once about their Jeff Frey designed treble control on the Aguilar OBP-1.

Here is what they said about it:

Quote:

Hello,

I was perusing your website, and I noticed in the spec sheet for the Super J model that it includes an "Aguilar OBP-1 preamp, Jeff Frey designed Active/Passive hybrid treble, active boost/passive cut on a single knob".

Is this a feature exclusive to your basses, or would it be possible for me to purchase this modified OBP-1 preamp on it's own?

Quote:

Hi Joey,

We have discontinued the Aguilar pre and now use Glockenklang (see attached word doc.) which offers the same passive tone control. This is a stock item that you can purchase through any Glockenklang dealer.

Best regards,

Barry Lamb
Int'l Sales Director/ Artist Relations
Dingwall Designer Guitars
www.dingwallguitars.com
Tel. 250.545.4423 PST
Fax. 250.545.4497 PST
blamb53@shaw.ca
Check out our forum.
www.dingwallguitars.com/forum/

Quote:

Hi Barry,
Thanks for the quick reply.

So there is no possibility of ordering this preamp then?

Was it made exclusively for Dingwall, or is there possibly a dealer that would still sell it?

Quote:

Hi Joey,

Yes it was made exclusively for us, Jeff is our head tech and designed the modification around our thoughts. The preamp was never made as a stand alone item, only as installed in our basses., as a result the preamp is not available.

Best regards,

Barry Lamb
Int'l Sales Director/ Artist Relations
Dingwall Designer Guitars
www.dingwallguitars.com
Tel. 250.545.4423 PST
Fax. 250.545.4497 PST
blamb53@shaw.ca
Check out our forum.
www.dingwallguitars.com/forum/

BarkerBass · #3 01-08-2010, 06:44 PM

hmm... oh well, I was thinking that i remembered it being mentioned a while back and seeing a website that offered it but I couldn't recall which one. Cheers for the help

cybersnyder · #4 01-08-2010, 07:10 PM

There was an ad in a recent Bass Player for a manufacturer that can do custom pots. I believe it was a German company and they do the pots for Glock and Warwick. I can't find their name. Maybe someone will know.

SebbyNC · #5 01-08-2010, 07:28 PM

Quote:

Originally Posted by cybersnyder

There was an ad in a recent Bass Player for a manufacturer that can do custom pots. I believe it was a German company and they do the pots for Glock and Warwick. I can't find their name. Maybe someone will know.

It's MEC (www.mec-pickups.de)
I also think it has to be a dual ganged pot, and probably put after an active/passiveswitch. My Noll preamp has such a treble pot, witch is treble boost/cut when the bass is in active mode, and passive tone control when in passive mode via the push-pull volume switch. I haven't tried it yet, as I'm still waiting for my SGD pickups.

cybersnyder · #6 01-08-2010, 08:14 PM

Quote:

Originally Posted by SebbyNC

It's MEC (www.mec-pickups.de)
I also think it has to be a dual ganged pot, and probably put after an active/passiveswitch. My Noll preamp has such a treble pot, witch is treble boost/cut when the bass is in active mode, and passive tone control when in passive mode via the push-pull volume switch. I haven't tried it yet, as I'm still waiting for my SGD pickups.

Yeah, that's it. Thanks.

**line6man** · #7 01-08-2010, 08:17 PM

Quote:

Originally Posted by SebbyNC

It's MEC (www.mec-pickups.de)
I also think it has to be a dual ganged pot, and probably put after an active/passiveswitch. My Noll preamp has such a treble pot, witch is treble boost/cut when the bass is in active mode, and passive tone control when in passive mode via the push-pull volume switch. I haven't tried it yet, as I'm still waiting for my SGD pickups.

Oh, I was thinking of a treble control like the Dingwall's that when set flat will actively boost when turned clockwise and passively cut when turned counter-clockwise.

If you just want a regular active treble control that will change it's function into a regular passive tone when you play the bass passive, you could just get a dual ganged pot and swap one of the wafers out so that you will have the right values, then use a 3PDT switch for your active/passive to connect the passive tone control in passive mode.

Also, as mentioned above, MEC does custom pots.

BarkerBass · #8 01-09-2010, 05:26 AM

wow, I didn't understand much, if any of that... wafers? any chance you could draw me a quick diagram?

**line6man** · #9 01-09-2010, 11:23 AM

Quote:

Originally Posted by BarkerBass

wow, I didn't understand much, if any of that... wafers? any chance you could draw me a quick diagram?

What I meant was to buy two pots and then disassemble them and swap out the insides so that you can mix and match the two values that you need.

walterw · #10 01-09-2010, 11:30 AM

How about a 500k m/n pot, with one side loaded down with a resistor to 50k or whatever is right for the preamp in question's treble control, and the other wired after the pickups but before the preamp? The one side would be a treble boost when turned up but do nothing when turned down, and the other side would be a passive tone rolloff when turned down but do nothing when turned up. I'm not sure about wiring the active side to just boost and not also cut, but there might be a way.

BarkerBass · #11 01-09-2010, 01:26 PM

ok I'm understanding a little bit better now.
so a dual ganged pot is two pots running form one shaft and the function changes when the switch selects which pot is wanted for which task.

since I plan on doing this to my new MIM deluxe jazz then it's have to be dual ganged with the mid pot so that'd need a 100K centre detented pot while the tone half would require a 250/500k pot for the cap to run from...

Line6, how easy is it to splice and dice, swap and change parts from pots like you said?

Passinwind · #12 01-09-2010, 02:02 PM

Quote:

Originally Posted by walterw

How about a 500k m/n pot, with one side loaded down with a resistor to 50k or whatever is right for the preamp in question's treble control, and the other wired after the pickups but before the preamp? The one side would be a treble boost when turned up but do nothing when turned down, and the other side would be a passive tone rolloff when turned down but do nothing when turned up. I'm not sure about wiring the active side to just boost and not also cut, but there might be a way.

Wiring for boost-only is trivially easy with something like a Bart preamp. Offsetting for more boost than cut or the other way around is pretty simple too.

**line6man** · #13 01-09-2010, 03:59 PM

Quote:

Originally Posted by BarkerBass

Line6, how easy is it to splice and dice, swap and change parts from pots like you said?

It depends entirely on the individual pot actually.

With regular full sized CTS style pots (not dual ganged), you can just pry up the four tabs, remove the back and pull out the wafer.
A sealed pot OTOH, it's pretty much impossible to disassemble without destroying.

It might be difficult to find the right pots to swap out.
You might be better off just contacting MEC about a custom job.

ac3320 · #14 02-14-2011, 06:31 PM

Quote:

Originally Posted by line6man

What I meant was to buy two pots and then disassemble them and swap out the insides so that you can mix and match the two values that you need.

would this scheme work for this setup (ala dingwall):

clockwise you're boosting treble (engaged only in active mode of course), counter-clockwise you cut treble passively (works in both active and passive modes)

1. Where you one have to place the active/passive switch with respect to this special treble/tone pot?

Thanks!

SDB Guitars · #15 05-08-2012, 08:53 AM

Quote:

Originally Posted by ac3320

would this scheme work for this setup (ala dingwall):

clockwise you're boosting treble (engaged only in active mode of course), counter-clockwise you cut treble passively (works in both active and passive modes)

1. Where you one have to place the active/passive switch with respect to this special treble/tone pot?

Thanks!

What you see in the diagram above would *not* work as the Dingwall hybrid tone control setup. The diagram is for "active treble control when preamp os active, passive tone control when preamp is bypassed".

The effect you are looking for would not have to be a switched circuit, it would just necessitate a very specific component that wouldn't be easy to source.

I can't speak to whatever circuit Dingwall used, it's proprietary, and I don't blame them for not wanting to give away their hard-earned R&D.

As I see it, however, the simplest way for this to work as requested (active boost from 5 up to 10, passive treble cut/standard tone control from 5 down to 0), would be to use a very special ganged pot. Fender has something like what you would need, but the pot values are WAY off. It's called a "TBX tone control", and it works like this:

From 5 back to 0 it acts as a standard 250K tone control (high pass filter), which when turned anywhere *above* 5 is removed from the circuit by having no conductive material on that part of the wafer, making it act like a "no load" tone control.
There is a center detent at 5 to show you when you are zeroed out.
From 5 up to 10, it acts as a bass cut with the addition of a resistor to set the peak frequency.The key in this case is that from 0 - 5 the wafer in this half of the ganged pot pair is at 100% resistance, and then the resistance tapers to 0, which rolls off the bass as you turn the pot from 5 - 10.

The "wafer" is the part inside the pot that is the variable resistance conductor.

To make an "active boost/passive cut" control, you'd have to have a ganged pot where one half (e.g. the lower pot) was exactly like the "high pass" portion of a Fender TBX, and the other half (upper pot) would have to have something like 0 resistance from 0 - 5, and then linear or audio taper from 0 to 25K from 5 - 10.

As I have described it, it *should* work. However, it would be a PITA to build, and if you tried to do it yourself, you would likely destroy the pot. A while back, I placed a call to Alpha Potentiometers to see what they'd charge to build this. Last time I checked, it would cost upwards of $5000 to prototype this pot, and then I'd have to order like 10,000 pieces. Since this is not worth ~$50,000 to me, I'd personally pass on it.

khutch · #16 05-08-2012, 10:44 AM

Quote:

Originally Posted by BarkerBass

is it possible to mod an existing active preamp so that the treble control boosts when clockwise from the detent but installing a cap so that you get a passive tone control when turning counter clockwise?

I think you could do that with a dual ganged blend pot actually. You'd have to put a resistor in series with one leg of the pot to replace the missing half of the pot resistance. You'd just connect a capacitor and the pickup(s) to the other section. Getting the right values would be tough, you'd have to go with a pot that is suitable for the tone control and probably pad down the preamp section to make it work right with the preamp.

Ken