FEMTOVERB /Wavefrontsemi/ PCB layout

[Marcvv]

Hi,

I am new to the forum regarding posting. I have been reading quite a bit and I am back to pedal building since a year. Have done quite some builds since and have learned a lot reading here. Thanks for that. This is a great learning place.

I just finished the build of the Femtoverb. Thanks to Metalguy.
I used a chipset that I got from Puretube. (thanks for that!!)

I made the PCB myself from the layout in this post. I read somewhere that this was not one that would be easy to "iron'.
My experiences was that it was easy to iron.

I live in Europe, and PNP is hard to get here. I use the photopaper method, using epson SO41126 paper. Works like a charm.
Soldering the femtoverb chips was the biggest challenge. I just realized that next time all I have to do is glue them to the pcb first then solder....

The pedal worked right away.
To my taste there was not enough wet signal.
To increase that I changed the 10k resistor between 1/2 op-amp 1 and the first 1/2 op-amp 2. This give a lot More signal going into the a/d converter later on. In my situation it can handle it easily. No distortion or whatsoever. (I am using guitars with humbuckers mostly, so it would apply to most other situations I would guess)
This helped a lot in getting more wet signal.

I read in a post somenone changed the mix pot to 1k, but to my experience that only changes how much you can adjust between wet and dry. 10 k makes a nice curve of adjustment.

Nevertheless I did not like the way the mix know works. You loose to much sound when going from dry to wet, as the drylevel goes down when you turn the mix to the wet side.
Instead of the mix pot I used two 10k resistors. one coming from the dry and the other from the wetsignal, as a 'set"mix. Then I used the mix pot as a wet level pot. In fact connected as it was: slider now going to the 10 k resistor. and the side where first the dry signal was connected now connected to Vr. This gives you a wet signal level that you mix with the level of the dry signal. For me a much better sound.

Some of the effects need the wet signal to be louder then the dry signal. To achieve that I changed the 10 k resistor of the "set" mix created with the two 10k resistors to a 4k7. In that way you can rise the wet level above the dry level.

This works really well now with a much better sound.

Overall it is a nice pedal and a very nice build. A lot of fun.

For me the reverbs are a bit modest. I do not know if it would be possible to change that?? I am open to suggestions.

Thanks again for the info.

Marc

PS as soon as I find out how I will post some pictures

[Marcvv]

Bump...

Anyone have any suggestions??

Thanks, Marc

[DaveTV]

Hello, Marc. I'm glad you're enjoying the Femtoverb. I also played around with different ways to improve how the dry and wet signals blend, but in the end I settled on simply changing the mix pot from 10k to 1k, which is how it is in the original circuit that the Femtoverb is based on. To my ears, I can get a nice blend between the wet and dry, without any noticeable drop in volume when turning knob from one end to the other.

One idea you might consider is using an op amp mixer to control the blend; maybe something similar to the output section of Scott Swartz' PT-80 delay. However, I don't think you can get 100% wet and 100% dry with this type of mix control. I'm not entirely sure, but I believe only one of the signals can be 100%, while the other just blends into it.  Still, for the Femtoverb you could design the mixer so that the reverb is the signal that can go to 100%. If you think about, is it really that important to be able to dial in a 100% dry signal on your reverb pedal? Isn't that what the foot switch is for?

[Marcvv]

Hi DaveTV,

Thanks for responding.

Yes it was your post I read on changing the mix pot to 1k, thanks for sharing the info.
I choose the solution I described which works great for me. If I get a chance I will draw up a little schematic of that for others in the future.

Did you manage to find a way to get a bit deeper reverb as, to me , the reverb could be a bit more intense. (this is not about the mix of dry and wet but about the reverb intensity)??

Thanks, Marc

[puretube]

feedback?

[DaveTV]

Marc, I agree. The reverb sounds are good, but it would be nice to be able to tweak them further. As I'm sure you know, the AL3201 chip was designed to be programmable so that it can be used in a wide variety of audio devices. All of the effects in the AL3201 chip can be accessed at the programming level and tweaked, but unfortunately this is beyond the scope of the Femtoverb (and my own knowledge and ability). The Femtoverb relies entirely on the default settings for each effect, so there really isn't any way to change the reverb sounds unless you program the AL3201 yourself. So the answer is yes, there is a way to make the reverb sound deeper, but it requires going beyond the Femtoverb's capabilities. Luckily, you'll find a lot of enthusiastic support here in this forum if you're ambitious and want to get deeper into DSP.

[Marcvv]

feedback?

Hi Ton,

Any suggestions on using feedback in this design??

Dave,
Yes it would be interesting to see if someone comes up with a solution.

Did you ever have a look at this:
http://www.profusionplc.com/products/RA-FX1V.html
It has been mentioned before. It is a complete board, afaik based on the same chipset, but it has the extra parameter control.
Would it be possible to add that to the femtoverb?

[ranchak]

Has anyone tried a dual gang pot to control the blend? Wouldn't this allow a better mix control? I read somewhere that you should use soldering paste for the chips. Where do you get soldering paste? Couldn't you grind some solder and mix it with some flux? I'm not clear on how to switch between the different reverb settings. I think I might start on this project this weekend if I have everything I need.

[puretube]

a fine point on your iron, and thin tin wire will work well, especially with magnifying glasses.
some solder-braid ("wick") will help for accidental bridges.

don`t be afraid of SMD - as long as you can clearly see what`s happening, it will work.

(i had bad experiences with (bought) solderpaste remnants underneath chips / beween pads,
that caused intermittent (high-ohmage) shorts in CMOS circuits...)

[ranchak]

Thanks Puretube. How do you control the switching of the different reverb settings?

[ranchak]

O.K. I see the Honeywell/Clarostat on Allied. How is it wired? Does anybody have a wiring diagram for the jacks and pots?

[ranchak]

C'mon guys I need some help with the offboard wiring of this. Does the 2M2 resistor go to ground? I see it does on the last schematic posted. but not on the previous ones. Would it be possible to replace the 4.7uF cap with an electrolytic? Which way would it be oriented? How difficult would it be to install a LED display to show the type of reverb being used? It could display Plate, Hall, Deep, etc. I'm really excited to get this project finished.

[Marcvv]

C'mon guys I need some help with the offboard wiring of this. Does the 2M2 resistor go to ground? I see it does on the last schematic posted. but not on the previous ones. Would it be possible to replace the 4.7uF cap with an electrolytic? Which way would it be oriented? How difficult would it be to install a LED display to show the type of reverb being used? It could display Plate, Hall, Deep, etc. I'm really excited to get this project finished.

Hi ranchak,

This is not a fast progressing post as not many have build this pedal apprently. That is probably why you are not getting a fast response.

Here is what I can contribute.
But there is a lot of information already in this thread. Go back a few pages and the answer on the wiring of the  encoder is described already. The original wiring in the schematics is not how it should be, as it will give another order of the programs. Read here to see what Metalguy wrote: http://www.diystompboxes.com/smfforum/index.php?topic=42305.60. It worked out good for me with a encoder I got from vishay (in europe)

yes the 2.2M resistor goes to ground. Are you working with the PCB of this thread, because that resitor is already in there.

I see no 4,7 uf cap? Which one are you referring to??

I can not give you an answer to your question about a program led display. Would be interesting, but not necessary for me with the rotary encoder being clear as it is.

Hope this helped?

regards, Marc

[ranchak]

Hi Mark, there is a 4.7uF cap in the upper left corner of the schematic on page 3 of this thread, it is listed as 4n7. I did read the response from Metalguy, I just wasn't sure of where to start (pin 1, etc). I need to do some studying on this topic. I'm pretty good at looking at schematics or a PCB and seeing what is happening and how to hook up the offboard wiring, but I don't have the experience/knowledge to do it on this project. I don't know how to hook up Mix A, MixW, MixB, Vol, etc. Thanks for your help, Ron

[Marcvv]

Hi Mark, there is a 4.7uF cap in the upper left corner of the schematic on page 3 of this thread, it is listed as 4n7. I did read the response from Metalguy, I just wasn't sure of where to start (pin 1, etc). I need to do some studying on this topic. I'm pretty good at looking at schematics or a PCB and seeing what is happening and how to hook up the offboard wiring, but I don't have the experience/knowledge to do it on this project. I don't know how to hook up Mix A, MixW, MixB, Vol, etc. Thanks for your help, Ron

Hi Ron,

First of all: are you actually working on the project?? Did you solder all the components already? You are saying that you do not have the experience and the knowledge but at the same time I get the impression that you are working on the project?? It is surely not an easy project.

Ok Let's see if I can help you out:
The cap is a 4.7 nf (or 4n7) and not a 4.7 uf. I would stick to that value and not use an electrolite. Maybe someone else knows exactly why?

As far as connecting the rotary encoder goes: if you look at the encoder from the top down (shaft towards you)
and if the pins are : 1-2-3-G-5
Then the encoder's pin 2 should connect to AL3201's pin 8, 1 to 7, 3 to 6, 5 to 5. G shoiuld go to ground.
(if you look at the pcb layout the reading of the pins of the AL3201 start from the dot  1-8 down)

Is that clear??

Then Mix A, MixW, MixB they go to the mix pot. A and B being the outer lugs and W being the centerlug.. Same for VolA, VolB and VolW.

Marc

[ranchak]

Mark, what I meant is I don't know shit about digital circuits. I've built many of the projects from GGG and the Tonepad site. I'm in the process of making a two stage tube preamp from a design from Hoffman amps. I've just never seen the pot wiring referred to as MixW, etc. The only thing I have left to do on this project is the 4.7nf cap, the crystal and the offboard wiring. I'm hoping everything works as I am not looking forward to troubleshooting. I'm a visual person, I need to see the whole project so I can see the big picture (a problem related to A.D.D.), that's why I am having some trouble with this project. I really appreciate your hope in this project. Thanks, Ron

[Marcvv]

Mark, what I meant is I don't know shit about digital circuits. I've built many of the projects from GGG and the Tonepad site. I'm in the process of making a two stage tube preamp from a design from Hoffman amps. I've just never seen the pot wiring referred to as MixW, etc. The only thing I have left to do on this project is the 4.7nf cap, the crystal and the offboard wiring. I'm hoping everything works as I am not looking forward to troubleshooting. I'm a visual person, I need to see the whole project so I can see the big picture (a problem related to A.D.D.), that's why I am having some trouble with this project. I really appreciate your hope in this project. Thanks, Ron

Sounds like you are almost there. Hope my information worked.
It is no problem that you do not know a lot about digital circuits with this one. If you managed to solder the smd parts then most of the project is like an analog project. The right wiring of the encoder is important but not crucial: if wired wrong you just get the wrong effect order. This is an easy fix if that would happen.

Is the off board wiring  clear now??

Have fun.

Marc

[ranchak]

I think I got it under control. What values did you use for the Mix and Volume pots? ( I see a 10KB).

[Marcvv]

I think I got it under control. What values did you use for the Mix and Volume pots? ( I see a 10KB).

Hi

50k log for volume
10k lin for the mix but I wired it differntly (see my previous post; my first in this thread) to get a better sound and a different balance.

[Mark Hammer]

I can't believe I went this long without asking or even thinking about this.

Flanger and chorus effects are created by mixing a delayed version of the signal with a real-time version of the signal.  When the Wavefront chipset is set to flanger/chorus, do you need the mix control to produce the effects or is the mix/blend pot used to combine a flanger effect in conjunction with a clean tone?  I.E., do you need to pan fully wet to hear the most intense flanging effect?