Electra distortion mod (bass)

[nchauhan890]

I'm currently in the process of designing/deciding on a circuit to use for my first guitar pedal build. I'd been debating whether to make a Bazz Fuss, but I ended up on an Electra Distortion since I don't want to go overkill on the clipping. I've done some research on modifications for bass guitar and have come up with the following design:



Is this a plausible circuit (remember, it's intended for bass guitar)? My attempt at the blend/clipping section is after seeing people saying that distortion will lose the root note on bass. Any feedback would be appreciated.

[PRR]

Welcome.

> Is this a plausible circuit

Yes.

I don't know what it will sound like. But it should amplify small sounds bigger and big sounds to distortion. No won't-work error that I see. Not a budget-breaker even if it is too boring to live. Ample room for changing components to try varied sounds.

[nchauhan890]

Thanks, I think I'm going ahead with it all.

Just a question: since I'm using a plastic enclosure (yes, I know you're probably going to say use a metal one), from anyone's experience or knowledge, do they put up with the "foot switch stomping"? I'm hoping they're rugged enough as I can't get my hands on a metal enclosure atm.

[vigilante397]

Depends on how thick. I picked up some RadioShack plastic "project enclosures" a couple years ago for rough prototyping and they absolutely withstood some stomping. I mean obviously I didn't jump repeatedly with both feet to try to break it, but a reasonable plastic box will take some use without breaking.

[nchauhan890]

Quote from: vigilante397 on Today at 01:18:44 PM<blockquote> but a reasonable plastic box will take some use without breaking.
</blockquote>


Hmm. I think this box should be decent:
https://www.bitsbox.co.uk/index.php?main_page=product_info&cPath=185_186&products_id=1408


Also, with that, what are your thoughts on shielding as I don't intend to do any. In addition , would I need to shield vertical resistor/transistor legs with the insulation off a wire?

[vigilante397]

what are your thoughts on shielding as I don't intend to do any. In addition , would I need to shield vertical resistor/transistor legs with the insulation off a wire?

I wouldn't bother personally. Shielding never hurt anyone (that I'm aware of), but for a simple, medium gain circuit like an Electra you should be fine without.

[nchauhan890]

I think I'll go with not bothering with shielding. However, I have another challenge:I hav that blend pot at the end of the schematic, but I want to add a switch so that I can have the "clean" signal at 100% at all times and choose to blend in the distortion channel

Here's my idea for the blend switch with a DPDT:
https://easyeda.com/NChauhan890/blend



The top 2 circuits show the states desired between positions on the DPDT. The bottom shows DPDT pins with my idea of what I could do:

• When the switch is in the top position, input 1 (clean/low pass) goes directly to the output (vol pot) and lug 1 of the blend pot is shorted to ground effectively making it an individual volume pot for input 2 (distortion channel)
• When the switch is in the bottom position, input 1 simply goes to lug 1 of the blend pot - making it function as intended from before

Would I need a resistor on the end of the channel which goes directly from input 1 to the output as it would not be affected by the pot and (maybe?) could cause volume irregularities when adding the distortion channel in?

[vigilante397]

Would I need a resistor on the end of the channel which goes directly from input 1 to the output

Don't you already have a volume pot at the end of the distortion circuit? You're obviously not going to have the same volume in both switch positions unless you crank the blend pot to the distortion side before switching, which is the same results as flipping the switch anyway.

So I guess I don't really see the point of the switch. If you just want your distorted sound without the clean blend wouldn't you just turn the blend to the distortion side?

[nchauhan890]

I see your point, but what I want to achieve is for the switch to make me able to have the clean channel at full volume and effectively add the distortion as necessary with the blend pot. In the current state, as I believe, if I turn the pot from 50/50 towards distortion, the clean channel decreases in volume which is not really what I am after...

If you just want your distorted sound without the clean blend wouldn't you just turn the blend to the distortion side

What I was looking for is a way to keep the clean and vary the distortion without loosing the clean

Edit: I think I'll leave this idea and leave the blend pot as it is. Although... I'm fairly sure I'll come up with some random new idea for mods...

[vigilante397]

What I was looking for is a way to keep the clean and vary the distortion without loosing the clean

Ah, okay. I see what you're saying, I apologize for misunderstanding.

The best way to do that (in my opinion) would be to buffer the clean signal and have a mixer at the end. Not sure how much you want to complicate the project, but you could look at something like this: http://tagboardeffects.blogspot.com/2013/01/2-channel-mixer.html

You could find the level you want the clean signal to stay at and replace the clean volume with fixed resistors then leave the distortion channel adjustable.

Just spitballing ideas here, I hope something in there is useful

[amz-fx]

There is no clean channel. There is unfiltered clipped, and clipped with a low pass filter. (I may be misunderstanding what you are calling the two signal paths.) I have redrawn it to show why there is no clean signal path:



As you can see, the clipping diodes are active all the time. If that is okay, then you are good to go! 

regards, Jack

[nchauhan890]

There is no clean channel. There is unfiltered clipped, and clipped with a low pass filter. (I may be misunderstanding what you are calling the two signal paths.) I have redrawn it to show why there is no clean signal path:

As you can see, the clipping diodes are active all the time. If that is okay, then you are good to go! 

Hey Jack! Thanks for pointing that out. Do you know if there is any way to create a "true" clean path? My first instinct would be to add another transistor and split the input at the start... But I'm concerned about spacing issues- I'm building in a 1590B-ish size equivalent (130mm*68mm) and as I'm a first time builder here I don't think it'll be feasible.

I found this, though...

Just another idea: (assuming I had properly separate channels) I came up with this easier circuit which would have an on-off-on switch to choose between:
- send input 1 to the output
- send input 2 to the output
- send both inputs to the blend pot (this would be in the off position)



If I made this into a DPDT switch, if I am correct I could crisscross the 2 inputs on the 2nd set of 3 lugs and in the middle have a ground line to ground the channel not in use. This would make it kind of like an "ABY" switch

[amz-fx]

You can just lift the bottom connections of the diodes off ground and then you have 4 sounds:

Clean, clean with low pass, clipped, clipped with low pass.

It only takes one switch pole since the two diode legs can be connected together. It might be good to inset a resistor in series on the clean signal path between the top of the diodes and the 100k pot. I'd start with 22k and see how that sounds.

regards, Jack

[nchauhan890]

Ah, that seems sensible (and with less hassle!). I actually had a quick notion previously about a distortion switch.

But, would it work if I wired a pot as a variable resistor between the output of the transistor section and the clipping diodes to adjust clipping? That'd give a decent "interface", let's say, to adjusting the distortion amount. 

So there's no way to isolate the low-pass side easily? (Not even by having a high pass on the second channel with the same corner freq? )That's quite an important aspect for bass as I need the root note to give a strong foundation.

[amz-fx]

Maybe something like this:



Not sure the 10k is large enough but probably okay.

regards, Jack

[nchauhan890]

Would this be any good? The bottom transistor one is the low pass and I know I've missed out some output caps and the diodes.
If that is any good, could I just move the input the of the top transistor section to the end of the capacitor on the LP filter to send all the signal that isn't very low to the distortion side which then goes to the blend?



(And thank you all for your invaluable advice and guidance)

[amz-fx]

How about this one:



Simply Wonderful Clipping Control (SWCC)   

regards, Jack

[Elektrojänis]

Maybe you should try the basic electra circuit before adding mods.

It is quite a low gain circuit and as such it the root note (fundamental) should not be lost that easily. If it does, I'd start by checking that the coupling caps are not limiting the lows. (Just put in bigger ones and see if the bass gets stronger.)

The problem with the fundamental getting lost usually comes when you want higher gain or certain more midrangy grunt to the distortion. Higher gain means more and higher harmonics generated and it can mask the fundamental. More midrangy grunt means you have to cut bass before distortion and that means the fundamental really gets quieter.

And depending on circuit even with a bit more gain the fundamental can stay quite strong. I'm using my own Fuzz Face variant for bass and I don't feel that the fundamental get's lost. (And my band mates have not complained about that either.) It's not that high gain though (lowish gain for a Fuzz Face) and the coupling caps are bigger than in a regular Fuzz Face.

Anyway... Usually it is worth trying out a circuit as is to see what actually needs changing.

How about this one:



Simply Wonderful Clipping Control (SWCC)   

regards, Jack

And after suggesting trying the original circuit to OP... I have to say I like the thinking on that one. One day I might try that on something.

[nchauhan890]

Hmm... I think I will take your friendly advice and stick with the simple circuit first. Luckily I haven't assembled the perf board yet so I can re draw my circuit. I'll stick with the vol pot but I think I'll switch the blend for a bass cut/tone pot. 2.2uF capacitors on the in/out should do the trick rather than the tiny little 100nF ones originally there.

Just something before i go ahead with it: could I create a low pass filter before the clipping diodes and place the diodes after the capacitors where the higher frequencies go?

[nchauhan890]

Looks like this is what I'm going for (obviously with the transistor section preceding it)... kinda like what had been suggested so thanks a lot. I found this article on Saturation Control on the AMZ effects page: http://www.muzique.com/lab/sat2.htm

Maybe you should try the basic electra circuit before adding mods.
It is quite a low gain circuit and as such it the root note (fundamental) should not be lost that easily.

I take on board your point, but I don't really want the extra work of getting more parts if the ones I choose don't work. This new option seems safe enough anyway.

Maybe something like this:

Seems like this suggestion... thanks!