Wah Wah Pedal Tweaking Issues (Morley PWA)

[deadsnake]

I've recently built a wah pedal acctually the circuit it self it's more important. I decided to repost topic because some people did not understand my problem. I aprecciate their efforts to help me out and I acctually tried everything that was appliable to me.

If I plug my guitar into the amp I'm going to get a full signal strengh and no tone change.
If I plug my guitar in the wah and then in the amp I'm going to get a weaker signal (lower volume) and a quite big loss in treble.

The other issue is that when I kick the pedal in I get a louder than when it was not depressed.

I don't know what I should do to correct this.

This is a schem I made to make thinks simplier to follow. I got it from Morley pedals download web page, I did some mods to match the  PCB which used the same schem but without bypass.

I might have made a wrong schem of the (LED, pot, 10k 220uF, 100K) but this is not a problem because the circuit works well and I didn't make the pedal using this schem.

I heard some resistors and even caps can change the tone and the strength of the output. I'm wondering which one should be changed to get the right sound. I changed the TL072 IC for a TL082 because I broke one of it's lugs and I coulnd't find another one, can It make a difference?

I would like to thank everybody that reached here, and if you didn't well I'm going to thank you too, but you're never going to know I did so. My room is a mess. I was hesitating to clean it up because somebody could have replied me and given me the solution and I wanted to do a mess again.

[johngreene]

What happened to R4? Is it on your board and just not shown on the schematic? The 'second' U1 shows pin 7 connected to +9V, this must be an error? If the schematic is not correct to how you built the pedal, it's of little or no use in helping you find your problem.

--john

[deadsnake]

I've build the pedal from this PCB layout.

I'm sorry about R4 I must have forgotten to use the alt key instead of the move key. My intention what to copy just the resistor symbol to some place else
this resistor it grounded and there is nothing more in series with it.

I don't know if U1's 7th pin is 9+ but you can check the original schem at http://www.morleypedals.com/pwaes.pdf I got it from there. As you can see pin 6 is also wrong it's supposed to be 1. check the Morley Power wah II as you can see they corrected it http://www.morleypedals.com/pwa-iies.pdf

I'm sorry about the delay when I was going to post the reply the forum was offline.

[johngreene]

The board looks to be made correctly even though the schematic is not correct. Do you have voltage measurements at all the pins? Especially around the LED? You may want to try replacing the LDR with a 1Meg pot and see if it works that way. Without some idea of where everything is biased, it's not obvious where to look.

--john

[deadsnake]

thanks for the reply I just did some mesurements on the pins what follows it's what i got:

1 - 4.76V
2 - 4.76V
3 - 4.51V
4 - 0V
5 - 4.01
6 - 4.41
7 - 4.40
8 - 8.80

Does pin 8 seems off? I'm almost sure somebody told me it was too high. The PCB I made and the layout out you saw are not different, I followed it all the way to the end.

Thanks for the reply.

GGM

[johngreene]

Pin 8 is VCC for the chip and with this design should be a 1N400X diode drop less than the battery voltage. So I would say that it is just fine.

How about the LED?

--john

[deadsnake]

well I had to replace the resistor in series with the led to get the right wah range. The LED it's too bright!. This voltage it's going to vary depending of the pot's position so I'll take both voltages all the way to each end. Btw I'm using a 500K pot since I couldn't find another one. A 250K was recommended.
This is the range of the LED's voltage. It ranges from 8.47 to 1.55. It's still bright tough. The output when I get max resistance of over the LDR when the LED is at 8.47 it's too high and it's distorting the signal as it get close to to the max.

[deadsnake]

Does anybody has a clue about how can solve it? Is everything worlking as it should?

[johngreene]

I thought you had it working from your last post. You said you changed the resistor to get the right wah range. If you have the right wah range, then what is still wrong? What did you change the resistor value to? Try moving the fixed resistor to the other side of the LED.

I don't understand when you say you are getting max resistance from the LDR when the LED is at max voltage. This should be the other way around.

--john

[deadsnake]

oh yeah that's right. Thats what I meant about the LDR. When I said that I changed the LED's resistor I did that when I've built the circuit. I said this just because you asked for the voltages on the LED. If I just told you the voltages without mentioning this you might have thought I did some mistake because there was in the original layout a 100ohm resistor instead of the 3k3. The purpose of changing it was to limit the brightness of the LED to not oversaturate the output with the wah. There are no problems with the circuit, but there is a problem with the output signal I'm getting.

There are little problems tough

I get a lower output when my guitar is plugged in the effect and then to the amp.
I get a higher output when I kick the pedal in.
I get a dull sound, no presense when the pedal is not kicked in.

The wah sound it's perfect tough. no noise and all. I'm just getting an uneven output when I use the effect.

[johngreene]

I get a lower output when my guitar is plugged in the effect and then to the amp.

Lower output than what? When the effect is there/not there?

I get a higher output when I kick the pedal in.

What do you mean by 'kick the pedal in'? The board doesn't have the connection for bypass, how do you do this?

I get a dull sound, no presense when the pedal is not kicked in.

Again, what does 'not kicked in' mean? How are you doing bypass?

--john

[deadsnake]

I get a lower output than if I had no effect at all plugged.
There is no bypass installed. I thought I could get the same sound as if no effect was there when it was not "kicked in".
What I mean by kicked in is when the pedal is all the way down.

Thanks for asking this I can see your understanding since you asked.

[vanhansen]

All the way down you mean which way?  Heel down or toe down?

Install some sort of bypass system, that's probably the problem right there.  I'm not sure how these Morley circuits work but if you don't have a bypass system, you're constantly running your guitar through it and if the volume is lower with the heel down than with toe down, then it sounds more like a volume pedal than a wah.

[SuperGeo]

I've built the colorsound and I believe he's talking about a dull sound then heel is down, the bassy part of the wah travel. And toe is down the volume is higher than the bypassed.

Well that's what I could figure out

[deadsnake]

Yep that's right SuperGeo. I know it's wuite confusing for other people to get it than for me since I can hear it. And vanhansen actually there is a wha sound as the volume oscilates when I toe down which gets a lot boosted. Do you guys know how I can remove this somewhat tone sucking(lowpassing) when the pedal it's hell down, and lower the output level when it's hell down a bit to match the output when it's toe down.

These are the simptoms just to make sure you got it right

Hell down ---> high output level compared to toe down. Typical wah sound.
Toe down ---> lower output level compared to just a guitar plugged to amp. No treeble.

[SuperGeo]

Mine colorsound wah is inductorless too, and when heel down it is less louder than the pedal bypassed too, maybe it's normal in this kind of wah or something

about the loud volume when pedal is toe down, I think you can adjust it with the level pot.

[deadsnake]

This os pretty interesting you were of great help. I never had or used any kind of wah pedal before so didn't know the way it acted. Do you know anything about the relation of capacitors and resistors about high passing or low passing? I don't know if I'm right but I heard that low values capacitor can cut the high frequencies. I'm wondering if the .1uF capacitor at the input (look at the layout or schem) is doing that because my sound is really lifeless when it's hell down, I'm thinking about replacing it with a jumper and see what happens. I can turn all the treble knobs at max (DS-1 and amp) let's say and I still get a dull sound. I think this is not right.

[vanhansen]

No treble when toe down?  That should be all treble.  Heel down sounds like it's right.

[deadsnake]

man i get confused with myself.......... I meant heel down........... I should just shoot myself..........

[vanhansen]

Ok, heel down will be no treble.  That is normal.  Toe down is all treble.  Sounds like it's working to me.  Put a bypass switch in it.