GreeneKing

I've been meaning to get around to producing a short post that illustrates how a filter based pre-amplifier works. It really isn't rocket science, it's just a different approach to the usual 2/3 EQ and you can't really relate to one via the other imo. In addition to a volume/blend knob basically you have: 1. A Low Pass Filter The ACG01 fitted to Alan's basses has one per pickup. The ACG02 retrofitted to a (cough) few of my basses has just the one. Imagine it's a bath tap. When the tap is shut it's leaking just low frequency sound, about 20Hz if I remember correctly. As you open the tap it allows progressively higher frequencies to be added to the flow. When the tap is wide open it's allowing everything through from the 20Hz right up to 3kHz. There's another 'little tap' on top that let's through a little extra just at the cut off frequency i.e. when the big one is shut that'd be 20Hz and when it's wide open 3kHz and wherever it's set in between. This allows you alter the shape of the frequency spectrum. This knob I will call the resonant peak boost, cause that's what it does. So here's some sound samples, they're just chromatic scales to illustrate the operation of the filters. First up just the neck pickup, with no boost, the filter is being incrementally opened from 20Hz to 3kHz. [url="http://www.zshare.net/audio/559253145e7fc64e/"]Neck pup no resonant peak boost[/url] Now with half boost [url="http://www.zshare.net/audio/55925786add6ed8f/"]Neck pup half resonant peak boost[/url] Finally with max boost [url="http://www.zshare.net/audio/5592607118b32063/"]Neck pup max boost[/url] Next is just the one sound sample going through the whole above process with the bridge pickup low pass filter: [url="http://www.zshare.net/audio/5592702673b51f1f/"]Bridge pup opened with a range of boost positions[/url] The low pass filters are always letting sound through. This tone is what I'd call the 'meat'. It's always there. The High Pass Filter can be shut right down like a 'non leaky' tap. I'd describe this as the 'gravy' in that you can add some if you need to but it's not essential. If the tone through the low pass filters up to 3kHz is good for you you can ignore the high pass filter. I'll continue the thread in a min looking at the High Pass Filter.

I can understand you being chuffed to bits over this, blow away! Peter

I've got 12. I'm single

1. Volume/blend 2. Low pass filter/cut off frequency resonant peak for neck pup 3. Low pass filter/cut off frequency resonant peak for bridge pup 4. High pass filter/cut and boost for both pups. There's a few threads on operation here, on Talkbass and on Alan's site. The aftermarket ACG02 only has one low pass filter for both pups. I've just fitted one to my Spector that also has a passive tone control. feel free to pm me if you need to know more. Peter

Yes Shaun that's mine (I forget it's in my avatar - doh). It's my dream bass made real to be honest. Very similar in spec to yours but 1 string less. Peter

If you read this very thread and others on the subject of using the ACG02 you will see your questions answered several times. Once you get 'your head around them' I'd say its easier to create your tone with a filter based pre than it is to tweak your tone with 2/3 EQ. Peter

You can buy them online. One was included with my Warmoth neck too. Venture onto the Warmoth website at your financial peril Peter

More than familiar Shaun I spent over 3 hrs choosing the woods Have you seen my 4? Peter

Alan If you're getting a sore shoulder playing seated isn't it more likely to be the way you're holding yourself (ooor, errr missus) rather than the weight that's causing the problem. That Sadowsky is nice. Hollowed out I assume. Peter

Not exactly. If they sound like 2 x GS112's then I'd say I'd be more than happy with one Obviously more difficult to lug around. Peter

I missed that Stuart. Date into my diary, sounds like a lot of fun. Peter

[quote]Can you bend notes on it - that was my first thought.[/quote] In more than one dimension

I'm stuck thinking about set up and getting the string/fretline straight and more or less parallel. Amazing idea. I'm imagining taking it into a shop for P/ex and say 'the neck's supposed to be like that'. Peter

Is it a two way trussrod? Some trussrods keep going and force a relief into the neck. ACG are such an example. Peter

Here's a few sound clips taken from the Spector post modification. The blend is centred and for all except the penultimate clip the passive tone is wide open. I'm just playing intervals of major 3rds down the far end. One basic way to look at the filters is to take the 'meat & gravy' approach. The low pass filter at one extreme lets through just the lowest frequencies and as it's rotated more and progressively higher mids are added to the tone without taking away the lows. This is the 'meat knob'. The top knob enhances the peak at the filter cut off frequency. The high pass filter when shut down just allows the highest frequencies past and as its rotated progressively lower mids are introduced . The two filters do overlap so you're not missing anything. This is your 'gravy knob'. The top knob on this is a cut and boost that has the added function/beauty of enabling the signal through it to be shut right off. The passive tone is just that, a pickup tone bleed off to earth. So here's the tone with both pups, passive tone not cut and high pass midway with cut/boost at the centre detent. So the gravy is set. What I'm doing sample by sample is opening the low pass to alter my most basic 'meat' of the tone. It's not necessary to listen to every sample to get the idea. [url="http://www.zshare.net/audio/55768053cfd0911f/"]1st sample[/url] [url="http://www.zshare.net/audio/55768754ced39d94/"]2nd sample[/url] [url="http://www.zshare.net/audio/557692881b18cab1/"]3rd sample[/url] [url="http://www.zshare.net/audio/55769511c34c4a0f/"]4th sample[/url] [url="http://www.zshare.net/audio/5576968230d2d3e9/"]5th sample[/url] [url="http://www.zshare.net/audio/55769728d1f4ebeb/"]6th sample[/url] The next sample shows the passive tone 1st in and then cut: [url="http://www.zshare.net/audio/55769918103348ad/"]Passive tone being cut[/url] The final tone just gives an idea of range. [url="http://www.zshare.net/audio/557699768037ee9b/"]Tonal range[/url] Peter - who realises on listening to the clips that I may have too much 'gravy' in the mix

Ever heard of the North West? What he said...

That's going to look really nice. Peter