Anderton Frequency Booster

[Paul Marossy]

Anyone here ever build it? If so, what caps did you end up using? Likes, dislikes?

[Mark Hammer]

I've made a couple, and stuck a scaled down one in the Forty-Niner overdrive I gave to David Lindley over the summer, to give more "ring" to certain bands by pre-clip boosting.

Works great, and an easy way to get your very own Billy Gibbons tone for little effort.

Pros?  Can be condensed to one op-amp, so easily wedged into existing circuit.  Bypassed with SPST switch.  Little current consumption or construction cost.  Easily adapted to multiple frequencies and cascading (you can stick one stage after another for multiple resonances).  Compact.  Runs off 9v.

Cons? Only does boost, no cut.  Frequency selection non-continuous; requires lotsa caps and big switch for more than 3 freqs per stage.  Degree of frequency boost limited (though maybe someone could point out a way around this).

In-between.  With resonant boost minimized/cancelled, there is still a gain of about 2.

Probably the most flexibility with the least cost and space might be a couple of cascaded ones in a single box, with a 3-way toggle for selecting resonant frequency in each module.  Ideally, for pop-free performance, a 3-way DPDT toggle that runs the caps in series, shunts the one set or the other, is best.  On the other hand, nailing the frequencies you want with standard value caps is probably easier if you simply parallel two alternate sets of small-value caps with a default set; identical to what I've often recommended for the Bi-filter Follower.

Three-per-stage may not seem like much, but if you cascade one for lows, one for mids, and one for treble, you can stick what is sort of the functional equivalent of a 9-band EQ in a 1590BB, with footswitch defeat/enable for each stage (and SPST bypass means you can use a DPDT if status LED is your pleasure), all for the price of a quad op-amp, a couple of 10k pots, and a small handful or passive components and toggles. On a performance-power-per-penny ratio, doesn't get much better than that.

Sold?

[Paul Marossy]

Well, I was initially thinking that it could maybe be an onboard guitar mid-boost type of thingie. Maybe a selection of a few different caps using a rotary switch. The main thing I wanted to see is how people feel about it. I have a fairly small PCB of 1.2"x1.5" that I just designed, so I guess this will be the weekend project... 

[Mark Hammer]

I meant to add to my prior note that one of the nice things about only needing an SPST to enable/bypass is that you can use momentary switches to enable the boost for a phrase if yu feel like it.  Since the momentaries are normally open, that means you can parallel them with a latched stompswitch to have a choice of step and leave on, or press as long as needed.  Great feature for gigging.

[Paul Marossy]

Hey, that momentary switch thing is a great idea! Hmm... maybe it's going to go into a box now. 

[Penguin]

hey paul  the emg spc the original one was nearly a direct clone of the anderton.  fyi 

ps i dropped off the package for you in the mail.

[Paul Marossy]

Ah, now I know the identity of the secret Penguin! 
Umm, is it coming COD? If so, I need to know the amount...

Anyhow, that's interesting about the EMG spc. I etched the board last night and it's 90% populated. I'll be messing with it tonight to analyze its capabilities. 

[Penguin]

nah i had my bp send it regular. Hmm i thought penguin was fairly obvious. lol..

[Paul Marossy]

nah i had my bp send it regular. Hmm i thought penguin was fairly obvious. lol..

OK, well PM or something so I know where to send the funds.