Overdrive with footswitchable boost

[VolksWilliam]

I've got an overdrive and I run a boss fa-1 clone into it and I want to combine them into 1 box. But I want the boost first and I only want it on when the overdrive is on. So 2 foot switched but if I turn off the overdrive the boost is off also. I know how to combine them in one box but stuck on the boost being dependent on the drive.

I also want to cut the gain of the fa-1 in about half. What's the easiest way to do this? Switch pots or add a resistor?

[GibsonGM]

Can you post a schematic of the FA-1, VW? That would help

As for the switching....to use the same switch to do different things isn't really feasible (if I am reading what you want to do correctly).   What I mean is....if you want the boost >> OD and the boost goes off if you turn off the OD, you can certainly do that, but all the time, not independently.    The boost would not be available by itself, nor the OD, without some more complication.

It CAN be done (somehow - I'm not up on the exact method) with relays, maybe digital switching, but it is complicated.

[midwayfair]

Are you okay with the boost staying on when you turn off the overdrive, or does it have to be that next time you turn on the overdrive the boost is also off? The second can really only be done with a PIC. The first you could do with active switching where the main bypass turns off both effects but the boost has to be switched separately.

[GibsonGM]

Are you okay with the boost staying on when you turn off the overdrive, or does it have to be that next time you turn on the overdrive the boost is also off? The second can really only be done with a PIC. The first you could do with active switching where the main bypass turns off both effects but the boost has to be switched separately.

+1      Can't see a way to do more than total True Bypass with one 3PDT, and 1 of the following with the other:

OD is always on, boost is switched in/out  (or vice versa)
or

OD and Boost on or off, together

(?)  I wondered this when I was new a long time ago, and got the same answer - the solution to the problem is pretty complicated, it involve programming....

[samhay]

FA-1:

(click for larger version)

>I also want to cut the gain of the fa-1 in about half.
That's what the volume control does. You could reduce the value of R6 or remove R6 and replace the 1M volume pot with a 100k or 220k pot, but I don't really see why this would be worth while.

Jon's question is a good one. There are ways to make this work without a PIC or similar using non-latching relays, but they are not likely to be low parts-count.

[VolksWilliam]

FA-1:

(click for larger version)

>I also want to cut the gain of the fa-1 in about half.
That's what the volume control does. You could reduce the value of R6 or remove R6 and replace the 1M volume pot with a 100k or 220k pot, but I don't really see why this would be worth while.

Jon's question is a good one. There are ways to make this work without a PIC or similar using non-latching relays, but they are not likely to be low parts-count.

The problem is that the only usable boost is between about 8oclock and 10o clock on the volume knob so there isn't much control. I'll try messing with r6. Thanks!

[VolksWilliam]

Ok I think I didn't explain this well. I don't need to get too complicated. Basically I just never want to have the boost on by itself. So 1 switch would turn the eitire pedal on and then I'd have another switch for if the boost was in the circuit or not. I think I figured it out in my head. 3pdp true bypass for the whole pedal. That in it goes through the boost, which has its own 3pdp true bypass, then into the input of the overdrive circuit then back to the bypass switch. So when off, the entire pedal is bypassed. And when on it goes through the boost, which is either engaged or not depending on its switch, and then into the overdrive. Make sense?

[nocentelli]

That sounds perfect

[GibsonGM]

Volume issue:   Without creating TOO much work for yourself....

...what I would do is find out what resistance values are "between 8 and 10 o'clock" on that pot, and replace the pot with one that will cover that range.

Ex: if you find the pot measures 800k to 1M in that zone, replace it with a 250k pot, and use whatever you need for resistances in series to make your new pot equal 1M (like a 470k and 270K together).   This way you get the full sweep of the pot to use inside that range, instead of just 8 to 10 o'clock.

It's one way to make that zone have more control.

[Pojo]

Agreed. That would work especially if you're set on fitting it all in one pedal. Of course if that isn't a strict requirement you could just make a true bypass looper pedal and place the boost and overdrive in the send/return loop. Keep the boost and overdrive pedals engaged and use the switch of the true bypass looper to switch them both at the same time. That offers a lot of flexibility in case you want to swap in different pedals in the future and keeps the option of using either pedal by itself should you feel the need.

Ok I think I didn't explain this well. I don't need to get too complicated. Basically I just never want to have the boost on by itself. So 1 switch would turn the eitire pedal on and then I'd have another switch for if the boost was in the circuit or not. I think I figured it out in my head. 3pdp true bypass for the whole pedal. That in it goes through the boost, which has its own 3pdp true bypass, then into the input of the overdrive circuit then back to the bypass switch. So when off, the entire pedal is bypassed. And when on it goes through the boost, which is either engaged or not depending on its switch, and then into the overdrive. Make sense?

[Agung Kurniawan]

I planing to build FA-1 next week, how does it sounds?

[VolksWilliam]

I planing to build FA-1 next week, how does it sounds?

It sounds great. Lots of tone control. But unity gain on mine is about 7 or 8 o clock and anything above noon just distorts terribly.

[duck_arse]

that circuit shows a A1M pot parallel to a 470k at R6. the resistance in the feedback leg therefore can never be more than 470k, and at 7-8 o'clock, A1M would be in the low, flat, slow change range of the taper, so less than 200k? try a B250k pot, might even be less than 100k.

as Mike says, measure the pot resistance in the useful range, work from there.

[Agung Kurniawan]

It sounds great. Lots of tone control. But unity gain on mine is about 7 or 8 o clock and anything above noon just distorts terribly.

Since its a clone, i think theres should be somethink wrong with solder side. Maybe you forgot somethink around the feedback.
The marshall mg-10 preamp is also great. I put it in a box, Mine has a gain and volume control. Its sounds nice and put it before my Boss MT-2 and Zoom Trimetal Clone give me great character of distortion sound...

[VolksWilliam]

I didn't build the clone. I ended up with it in a trade. But I took a look under the hood to investigate and realized. There's no IC's! They are just empty on the board. Should it work without them?! It does. But that may be why it's so weird about the volume and clipping distortion.

[Kipper4]

Your 4558 is the IC.
Half of it is used as a volume control. The other half is used as an active tone control.
See how the tone stack is in the feedback loop of ic2.
The FA1 is basically a jfet buffer with tone options.
One of my absolute favourites.
If I remember right one of the online schematics has a wrong cap value too.

[VolksWilliam]

Your 4558 is the IC.
Half of it is used as a volume control. The other half is used as an active tone control.
See how the tone stack is in the feedback loop of ic2.
The FA1 is basically a jfet buffer with tone options.
One of my absolute favourites.
If I remember right one of the online schematics has a wrong cap value too.

Ok. So it's not wrong that ic 1 and 2 are empty? Should I bump up the resistor that comes off the volume pot?

[Kipper4]

The jrc4558 is fine for this. Dip8 dual in line pinout.
It looks like the pcb maker was giving you the choice of ic configuration.
You can still get the ha1457 which is a single in line configured pin ic. Smallbear stock the original ic for a couple of your American dollars (not affiliated)

I guess that's your board in the photo William?

Which resistor are you talking about?
R? In the above schematic.

It should have a ton of volume.

[Agung Kurniawan]

Ok now just wait for a secon everyone. Is that really possible to do subtitute HA1457 with 4558 since they are a different of op amp tipe?

[Kipper4]

Yep....