freestompboxes.org

Friend share with a lot shhhhh? hear the original and does not.

There is shhhhhh LOL I think a lot has to do with component selection every chip is different.. I don't have an original but I have played one. I would bet there is a filter on the output. i am at stock values for he pedal right now but am going to do some tweaking today and tomorrow I will post some findings

ok have played with this . The hiss is the circuit there needs to be a filter on this thing I would bet it is after the first stage but you could tale it out after. If anyone has an Idea please yell it

1) The problem with the gain pot is that as you vary the resistance the eq changes so the caps parallel to the changing resistance will need to change... I verified this.

2) I have a on off on switch which currently has a 820pf, 320pf and 1nf caps bridging the respective poles.. leaving off the cap in the. I have put in the center causes the thing to be unstable. as an addition to #1 When I changed the gain resistance the overall output went down and the eq changed.

3) I switched to the lf353n and still have to finalize that move as a 'best choice' for me

So.... Any ideas about a filter would be welcome. There was a noise filtering for the lovepedal purple plexi circuit between pins 1 and 8 but the layout of that chip is different. I will post it here maybe it will spark and idea. I have to read over it my self with the pinout diag's to see how it might apply but if anyone has a solution before i spend the time I will take it.. (I am a lazy F*&$ LOL)

Thanks for any assistance!

PS Remember attachment is not for this build it is for the LM386!

A

The Lm386 is not an opamp, it's actually a power amp. The cap you are refering to is actually adjusting the gain, a dual opamp does not have "gain control pins" like this. I built a couple of Rust drivers a while back and did not have any more noise than the typical distortion pedal but I did find that different values of input resistor can greatly change both gain and noise (just like an input gain would). I think the original was 100k.

bigorangefan79 wrote:The Lm386 is not an opamp, it's actually a power amp. The cap you are refering to is actually adjusting the gain, a dual opamp does not have "gain control pins" like this. I built a couple of Rust drivers a while back and did not have any more noise than the typical distortion pedal but I did find that different values of input resistor can greatly change both gain and noise (just like an input gain would). I think the original was 100k.

Thanks for the response. Yes I know about the differences in the chips but I posted the other solution as a call for help LOL

The noise is just hiss. It could be from the diodes or the gain. I tried filtering it out but to no avail I just kill the output.. Must be calculating wrong...

I have a 100k input resistor. Did you build one of these layouts or did you do your own? If you did iether could you tell me which one you built?

Thanks again

Adam

So this is Bugging the F&%* out of me.. I ordered a real one... I am going to de bug this... I will put the real on eon my board LOL and give the one I de bug to a friend but there is somethign else at work here. I believe the posted schematic is wrong.....

With my luck it will be an SMT board ROFL..... Hard to trace that stuff.. Its a simple circuit though.. It has to be Power filtering/ LPF.. I would bet that the feedback circuit is different to...

What the hell do I know.. Its just driving me nuts LOL

A

I will be interested in your results. I have the hiss that you are referring. None of the filtering i have tried has helped.

The Rust Drivers and derivatives that I have built have been based on the Matsumin schematic. I have not had these noise problems. I have a few questions that you have probably already answered: have you tried batteries and different power supplies? Have you tried a 100-200UF cap across power and ground (- to 9v + to gnd)? Have you tried a 50-100UF cap across half power and ground (- to 4.5v + to gnd)? Have you tried a small (20-100 ohm) resistor in series with the power before pin 8?

bigorangefan79 wrote:The Rust Drivers and derivatives that I have built have been based on the Matsumin schematic. I have not had these noise problems. I have a few questions that you have probably already answered: have you tried batteries and different power supplies? Have you tried a 100-200UF cap across power and ground (- to 9v + to gnd)? Have you tried a 50-100UF cap across half power and ground (- to 4.5v + to gnd)? Have you tried a small (20-100 ohm) resistor in series with the power before pin 8?

1) Have not filtered the power past what the Matsumin schem had.. I will try what you did above (thank you for this... have not seen that recommendation yet on the forums! )

2) used batteries and my voodoo labs PP2...

3) Either way. I guess I had expected the debug of the original pedal to be a nuts on point to point verification. I am new to the forums. I am now learning that the verification is that the circuit works not that is a verification of the actual board to the derived schematic. Its cool just my learning curve...

4) I will when I get the pedal today see whats going on under the hood if at all possible. I will not de-goop and I hope its not smt.. I can never follow those. My dyslexia will kill that effort. ROFL

OK
1) Filtered 1/2

2) Filtered 9v-earth

3) add block resistor 33R

No change

I built on vero board funny thing is that when I hold the board end to end and the box it goes reduces big time! It is only when I hold the end corners containing the feed back wires granted the 9v is there as well but filtering that did nothing.. So I bet there needs to be some very very small capacitance to ground from the feed back loop I will have to play with that... I did some filtering tests earlier and they either did nothing or killed the output as a LP. I guess I am not calculating the resistance of the circuit correctly before the feedback or after it LOL Any ideas... The output impedance is very low so I just was using standard LPF calculations but they shut the out put off to nil even with a relatively high roll off point of 7khz using a .022 cap off the 1k in between the 2 stages reduced the total output to next to nothing.. They was no hiss LOL similarly with the same calculations off of the 22k it shut it down. any ideas would be great. I am so far from engineering school that I have forgotten most LOL. I am sure the .1uf's and subsequently the output pot and 47k are effecting my calcs but I can't remember how ....

Either way the real one arrives today.. I will be away for a few days but when I get back I will start tracing the official one. I will be checking in from teh road any ideas will help me relax LOL

Thanks A

Just came in:

So I plugged it in and there is some hiss but so greatly reduced that its very usable...

I opened it up and took some shots. I am at work so I cant really rip it apart but I id'd mistakes off the top....

1)There is a 680p cap in the feedback loop. This enables the use of a spdt on-off-on switch see pics.. the switched caps are 4n7 and 1n0 makes sense bright is 680p normal 1.68n and low 5n3





2) There are 2 diodes(Need to trace this. you will see that on the pic with the 22p below in #3 - must look on other side) and big filter caps all over the power supply 2x 47u @ 25v and 1x 100uf @25v I have to trace it but there looks to be a 2x 1.2k ohm in there too...





3)Another filter of sorts 22p attached to the 330k I have to take this apart to see if there is anything on the other side (there are solder pools and wires going underneath) but if not it looks to be in series with the 100k and .0xxuf on input.. the cap is tight cant move it to see value



4) there are 2 x 1M on the board probably one in PS and other in input

5) can anyone ID those clipping diodes?

So the existing schematic is missing a bit. The whole dpdt on-off-on with 2 caps seamed wrong as with no cap this thing would be way unstable... When I get back from Vegas I will dive into this I hope the pictures help someone.... Once I get this right I am giving the build I complete to a buddy who is dead broke Its only fair to keep the one I have and use it as The companies need to be supported

A

thanks for doing this! contributing is always awesome
this also will give you a noticable experience boost!

i love how they only gooped the ic

Seiche wrote:thanks for doing this! contributing is always awesome
this also will give you a noticable experience boost!

i love how they only gooped the ic

You are welcome.. I would always do my part That being said it is important to support the pedal co's They make it all possible. It would trouble me greatly if anyone profited other than Hao from any of this...

We are a small community and I believe that the stuff we do only causes hype for pedals and makes sales go up but .......To the community at large....

PLEASE DO NOT TAKE MY WORK AND USE IT FOR RESALE! THANKS A

OK Last thing to do from work or I will get my self in trouble (I'm the boss) Here is a shot of the bottom of the board.... now I think someone can super impose and get the final picture of this thing.....



I can't do any more until Wednesday night of next week but I will be watching the thread with baited breath!

Oh by the way the input cap I couldn't read is a 56n .... I can de goop the chip when I get back if anyone can tell me best practices...

The component solder pools are the pot which I know and the supports for the pot which I didn't LOL

A

Last thing before I go to Vegas LOL

here are 2 cropped images with the bottom mirrored and flipped so you can see it all side by side



Have a killer weekend I will check in.. I hope someone goes to town on this..

A

How´s about one (ore more) picture(s) of the inside with all of the wiring shown ?

tube-exorcist wrote:How´s about one (ore more) picture(s) of the inside with all of the wiring shown ?

Man... LOL My wife is gonna kill me ROFL. I uploaded to my mac so the pics are going to be large. For what ever reason Mac don't gots paint LOL cant resize so they are attached.

There are pictures of:

1)the whole guts with wire tie

2) the whole guts without wire tie

3) close with the wire tie cut to reveal more of the board

4) Another angle

Hope this helps.... # 4 is the best pic.. screw my camera in my phone LOL When I get back if this is all not laid to res already I will get better picks Sorry

Enjoy... Vegas here I come.. "yes honey I am getting off!"
A

tube-exorcist wrote:How´s about one (ore more) picture(s) of the inside with all of the wiring shown ?

Hey from Vegas ....

We're the wiring shots helpful ?

A

This looks to me like it has a 10k (instead of 100k)after .056 at input followed by 33k (instead of330k) across pins 1 and 2. This would really change things.

There is also a 47k resistor between 1/2 power and pins 3 and 5.