BMP (adding a) tone switch problems

[DeusM]

Hey, guys. I finished my prototype of a BMP (my very first pedal) and it sounds awesome but then I decided to add an extra feature to make it unique so I came up with the idea of adding a switch so the tone control is fully opened because it sounds super high like a radio or from and old speaker and it's a cool effect. Since I'm not going to fully open the tone control under normal circumstances the only thing that matters is making the switch working properly and it means lower the volume since more opened tone control = more volume specially from 6 to 10 (being 0 fully closed and 10 fully opened) Also it does a popping sound which I can't get rid of but first I'd like to fix the problem volume which I'm not sure if it could be fixed. So here is the schematic.




Here is the tone section:




And here is the original design:






As you can see I changed some values to get the type of sound I was looking for and I'm more than happy with it but I'd like to fix this tone switch problem so I'm done with the most important part of the effect. So hope you can help me guys! Thanks! 

[GibsonGM]

Hi Deus,

Good idea there.   Ok, I hear you - what I might try to keep the level close when the tone is bypassed, or when it is not, is to do the following:

>  Wire a pot in series with your volume pot, "above" it, maybe 100k, set up as a variable resistor (NOT like the volume pot...wiper and 1 lug only)
>  Set that pot to 0 ohms, and set your tone control to a reasonable place.    Set volume to 50% (50k).
> Now switch out the tone stack (bypass it).   Volume will jump up...use the "new" pot to lower that volume to what you think is the same as it was before you bypassed it.    Measure the resistance of the "new" pot.

Hard wire a resistor of about that value in the place of the "new" pot.

Now, remove the LED indicator from your switch.   Use that side of the switch to jumper across the new resistor...when the tone stack is in use, it should be shorted out  ("jumped over").   When you flip the switch to bypass the tone control, the new resistor should be in-circuit.  If you want the LED back, use a 3PDT switch.

Does that make sense?  Seems to me like this would work.   Adding the resistance to the 'top' of the volume pot is like turning it down...the ratio for division with the pot is Vout = (R2/R1+R2) * Vin.    What I'm suggesting would allow you to 'add' to R1 in the equation.   You'll have to experiment to find the ideal value, tho.

[Quackzed]

herees a schem of a big muff version that has a tone bypass built in, theres a voltage divider with a switch setup take a look, i think gibsons suggestion makes perfect sence   and probably  what elect harm did to arrive at their solution, but for sake of ease, i figured i'd link to a pre existing solution... the red bits around the tone section are the bits you'll need to add... really just the 150p and the 47k's  in the voltage divider.. and switch of course!


http://www.diystompboxes.com/smfforum/index.php?topic=101453.0

[GibsonGM]

A picture is worth 1,000 words, Quackzed!  Thanks for posting that.

[DeusM]

Thaks guys for the answers! I'll try later and tell you how it works!

Quackzed: Wound't that 47k resistance to ground (the red one) change the tone? I think I tried something like that and that was the result but anyway I should try again comparing with this circuit.

[Quackzed]

in some cases, adding a resistance or a 'load' after an amplifying stage can 'load' down the output and you'll lose a little treble, but an op amp has a very low output impedance and can easily handle the extra load without losing any high end...

WAIT!!! your not adding it to an op amp bmp are you? with a transistor you might want to use bigger resistors instead of 47k's just to be safe...
i'd say 220k's should avoid any loading if you notice any treble loss...

[DeusM]

It's not an op amp fuzz, its a transistor one.

Anyway, I was trying to test it again since I left the circuit for a couple of weeks since I had other things going on and I'm noticing that when the tone pot if fully closed the volume drops a lot, and when its fully open it goes up a lot too so I'm thinking that there might be a problem in the circuit or maybe i F'ed up changing the componen values.

Also I have too much noise but I'm not sure if its beacuse of the circuit not being enclosured or "something else". Is it normal such a volume drop? Also, there's no distortion when the tone control is closed and it starts distorting once I start opening it.

UPDATE!!!: I tryed the same settings in my old guv'v nor and the same thing happes there. Volume drops when tone is fully closed so I guess its something normal. So, I learned something new today. But I still have the problem with the noise and since its my first pedal I'm not sure how normal it is.

[GibsonGM]

Well, since you're actually sending part of your signal to ground, yes, some vol. drop would be expected! 

Noise: lots of causes for it.  Too long ground wires, not using a 'star' scheme, wires crossing each other (coupling)...can try using a shielded wire on your input and see if that helps.

Distortions are also quite hissy, noisy...ANY noise at all in the circuit (will always be some) is massively amplified.   High gain stuff is hard to make really quiet.   I just click mine on when I start playing, or use a noise gate...

[Plexi]

May I suggest to send signal in "another" way?
I would convert your switch to an a/b: send your full treble signal to another recovery+master volume stage.

[DeusM]

May I suggest to send signal in "another" way?
I would convert your switch to an a/b: send your full treble signal to another recovery+master volume stage.

I'm not sure how to do that, I'll then have to rewire it to the volume pot.
I'm still not sure about the explanations you gave me so far. And now my circuit doesnt sound at all. Gosh! Maybe I burned something? I tried adding the 100k resistance but I wasn't sure where is was suposed to go in the volume pot.

[DeusM]

Guys, my knowledge of electronics is VERY VERY basic. I learned the necesary for making pedals and this is my first one so I migh have many problems trying to unerstand your explanations so sometimes I have no idea what people tell me about so I do my best to understand the explanations you give me .

[DeusM]

Guys! Thank you very much for your responses but I decided this is to complicated for me right now so I decided I'll do a feedback loop instead with a momentary switch and maybe try this when I'm more experienced with circuits and pedals. I don't want to waste more time on this thing because it's stopping me from creating the board and working in the enclosure so I'll try to make some kind of fixed eq pedal for that special kind of ratio tone. If you guys could give me a hint about ho to create that, it would be awesome so thank you!

[DeusM]

Solved... Don't know if anyone is interested but I made the special tone swicth with an LED and volume drop so it doesn't sound louder.

[GibsonGM]

Solved... Don't know if anyone is interested but I made the special tone swicth with an LED and volume drop so it doesn't sound louder.

I'm glad you figured it out!  It's tough when you don't have the background, I know...that's why I read tons of stuff about electronics in general, and paid attention to threads like this.  Over some time, it starts to make sense!

[DeusM]

Solved... Don't know if anyone is interested but I made the special tone swicth with an LED and volume drop so it doesn't sound louder.

I'm glad you figured it out!  It's tough when you don't have the background, I know...that's why I read tons of stuff about electronics in general, and paid attention to threads like this.  Over some time, it starts to make sense!

Absolutly true! I feel like I have a lot to learn. Lot's off places to do that on the interwebs like Khan academy or www.tpub.com/

[GibsonGM]

I used to read a few Navy personnel manuals, LOL.

Youtube has TONS of stuff...look up "EEVBlog"!   

Some demos on how potentiometers work, and how to calculate voltage divider resistances would have helped a lot with your problem, too...   

[Plexi]

Solved... Don't know if anyone is interested but I made the special tone swicth with an LED and volume drop so it doesn't sound louder.

Great!

My initial idea was to build two separate tone+recovery stage: one fixed with trimpot+ their own master, and another "normal" channel, tone pot+master.
Simply switch A/B

Next time let me know, and we talk in español... 'bolúdo'! 

[DeusM]

Solved... Don't know if anyone is interested but I made the special tone swicth with an LED and volume drop so it doesn't sound louder.

Great!

My initial idea was to build two separate tone+recovery stage: one fixed with trimpot+ their own master, and another "normal" channel, tone pot+master.
Simply switch A/B

Next time let me know, and we talk in español... 'bolúdo'! 

Jajajaja na boludo! To be honest I took your Idea but making another recovery stage was going to be a pain in the culo since I had to take in consideration the volume pot, so What I did was to create two paths for one of the resistances (R 23) wich controlled in some way the gain. When the switch is on the path with the lowest resistance will be conected. There was another resistance that did that but this one worked well. Of course to have an LED i'll need a 4pdt but it's ok. Los culiados de axis tenian 4pdt y no 3dpt 

[GibsonGM]

Some time, visit what I suggested above, about shorting out a resistor above a pot.  PM me and I will send you a drawing if you like.