mxr envelope filter probs

[Artcool]

  Hi to all,

in need of some help here...just build the Envelope Filter (tonepad layout) without the modifications possible in this circuit and explained in the schematics, but, i just cant get any sound thru it nor the effect of course  ..

here goes my readings hoping someone can help me debug it

************

1.What does it do, not do, and sound like?

No sound passing thru

2.Name of the circuit =

MXR-EF (tonepad layout)

3.Source of the circuit (URL of schematic or project) =

http://www.tonepad.com/getFile.asp?id=113

4.Any modifications to the circuit? Y or N

Y - Changed C5 from 0.05uF to 0.47uF. Changed R16 to a 100k trimpot.

5.Any parts substitutions? If yes, list them.

IC1 and IC2 (tried with ST 4069 / 4066 and with Ti 4069 / motorola 4066 ) and combinations of these ( just waiting for fairchild chips, but i saw some reports somewhere , its possible with chips non-farchild , using the trimpot to adjust voltages...)


6.Positive ground to negative ground conversion? Y or N

N

7. What is the out of circuit battery voltage? =>

8.09v (used it since new in this circuit)



Voltage at the circuit board end of the red battery lead =

8.09v

Voltage at the circuit board end of the black battery lead =

0v



voltages as follows:



IC1 (or U1)

P1  : 1.51v
P2  : 1.52v
P3  : 1.51v
P4 :  1.43v
P5 :  1.51v
P6 : 1.52v
P7 :  0v
P8 : 1.50
P9 : 1.51
P10 : 1.60
P11 : 1.48
P12 : 1.48
P13 : 0.96
P14 : 3.44

IC2 (or U2)

P1: 1.56
P2 :1.80
P3 :1.81
P4 :1.58
P5 :1.58
P6 : 1.44
P7 : 0
P8 : 2.97
P9:1.13
P10:0.89
P11:0.30
P12:1.95
P13:0.34
P14: 3.44


IC3 (or U3)

P1: 0
P2 :0
P3 :0
P4 :0
P5 :0
P6 : 2.96
P7 : 0
P8: 1.51
P9: 1.52
P10:1.51
P11:1.49
P12:3.00
P13:0
P14:3.44


D1
A  =1.98
K = 3.44

D2
A =0.78
K =1.97

********************

thanks!

[Artcool]

after some more time with it, i found it is working , only the sound is very low ... tried to change R2 to 150k and even 100k with no big diference, it seems the sound gets low at input stage (im testing with line level signal ... i imagine if i use a guitar it will be weaker ...)...what could be the problem here?

[jefe]

4.Any modifications to the circuit? Y or N

Y - Changed C5 from 0.05uF to 0.47uF. Changed R16 to a 100k trimpot.

Assuming that this is not a typo, then maybe this could be your problem? If you substitute from 0.05 to 0.047, then it should be fine, but you wrote 0.47 - is that what you meant?

[Artcool]

  oops... its not a typo and you're right , i will put back the original value and see what happens ... trying to make it sound i made that mistake...late night of course

thank you for helping

[jefe]

oops... its not a typo and you're right , i will put back the original value and see what happens ... trying to make it sound i made that mistake...late night of course

thank you for helping

Cool, no problem! Keep us posted.

[Mark Hammer]

Even though your battery is less than optimal, the voltages on the V+ pins of the chips are conspicuously low.  Something is amiss with the distribution of power to the chips on the board.  The fact thjat it affects all 3 chips suggest something more central and along the power lines, rather than something specific to an individual chip.

[Govmnt_Lacky]

Even though your battery is less than optimal, the voltages on the V+ pins of the chips are conspicuously low.  Something is amiss with the distribution of power to the chips on the board.  The fact thjat it affects all 3 chips suggest something more central and along the power lines, rather than something specific to an individual chip.

+1. I would definitely look into your V+ signal flow on the entire board and check for component values, orientation of components, etc.

[Artcool]

thanks to all, i have some clues now  where to look, tonight will mess a little bit more and see..

[Artcool]

finally and after a complete look at component values and placements, i found a bad pcb trace  ... now it is working and seems responding to controls... is it normal in this effect  to limit the audio bandwidth , filtering almost all the bass region and the top treble ? i'll try to tune it a bit, and also try the Farchilds i received today.

by the way, the ICs pin 14 voltages are the same i reported before...

thanks to all!

[Artcool]

After messing a little bit more with the circuit i found if i connect a low level signal at input (i tried with my Hohner Clavinet D6, which is basically a guitar with keys , and with a internal preamp (9v)...i cant have the effect working, but if i connect a MP3 player output (headphones out) it starts working...which components can i adjust so to adapt the input sensivity ? I heard about a little preamp+millenium bypass which i can connect before this pedal, but want to try first without this if possible...after all this pedal is intended to work even with a passive guitar at input...

regards

[Govmnt_Lacky]

finally and after a complete look at component values and placements, i found a bad pcb trace  ... now it is working and seems responding to controls... is it normal in this effect  to limit the audio bandwidth , filtering almost all the bass region and the top treble ? i'll try to tune it a bit, and also try the Farchilds i received today.

by the way, the ICs pin 14 voltages are the same i reported before...

thanks to all!

I remember reading somewhere that this circuit had issues when using any other ICs other than Fairchilds.(Tonepad's build reports maybe??) If you have not done so yet, you may want to install the Fairchild ICs and give it a try.

[jefe]

After messing a little bit more with the circuit i found if i connect a low level signal at input (i tried with my Hohner Clavinet D6, which is basically a guitar with keys , and with a internal preamp (9v)...i cant have the effect working, but if i connect a MP3 player output (headphones out) it starts working...which components can i adjust so to adapt the input sensivity ? I heard about a little preamp+millenium bypass which i can connect before this pedal, but want to try first without this if possible...after all this pedal is intended to work even with a passive guitar at input...

regards

Check out this thread, it might have some answers for you (or might not, I'm in a rush at the moment, sorry):
http://www.diystompboxes.com/smfforum/index.php?topic=66768.0

[Artcool]

Hi Jefe and Govmnt , thanks for helping.

Yes , i will try with Fairchilds, but i wonder if this will affect the input gain of the circuit, basically the effect is ok with ST chips and a 100k trimpot in place of R16, only this low input thing ... but i will try anyway ..

[Artcool]

ended making another pcb and now all is ok , sounding  very good indeed..thanks to all who helped !!