Adding an effects loop and expression pedal to an EHX Freeze

[aion]

I'd like to add an effects loop and expression output to my EHX Freeze. There are a few people who have done this but there are no definitive instructions anywhere. I think I have it most of the way figured out, but I'd like some input before I heat up the soldering iron.

Here's some speculation from Processaurus about how it might be done:

AC couple it with a cap (.47uF would be where I'd start), and if necessary, bias it up to where the signal on the wiper was biased (wouldn't be able to guess, but just stick a meter on the unmodded circuit and see if there is a DC voltage on the wiper), and you're back in.  You're basically just finding the wet before it is mixed with the dry, AC coupling it to the send jack with a series cap, and with the return, again AC coupling it with a series cap, and biasing it to the right DC voltage (if necessary) to go on to the rest of the circuit where it was going originally before you installed your loop.
http://www.diystompboxes.com/smfforum/index.php?topic=85210.msg790604#msg790604

This guy took that advice and came up with something that apparently worked for him, but he made some changes and it doesn't seem "right" to me. He took the output from a resistor before the level control and then returned it to the wiper, but it looks like he left the existing connection intact, so I would think that at best the loop is paralleled with the existing signal. I think it wasn't working the way Processaurus described because it wasn't getting biased back to 1/2V in his case. The wiper measures about 2.7V, which is just above 1/2V (the circuit uses a 5v regulator since it's digital).

Anyway, here's the wiring diagram I came up with:



This would of course use switching jacks: the tip and ring of the loop would be connected if nothing was plugged in, and the expression jack would just go straight back to the main Level pot.

The main question I had was concerning the wire colored red, between the effects loop and the expression jack. This is where I'd need to bias back to 2.5 or 2.7V, as it's the effects return, but I'm not exactly sure how to do this. Should I trace to find the 1/2V voltage divider and then run a wire from there to the junction of the cap and the red wire? Is it important that it's at 2.7v instead of 2.5V? I did measure the other side of the R3 resistor (where the guy above connected the send) and found that it was 2.5V on the nose. I don't know enough theory to know how it got to 2.7v on the pot and whether that's important or not.

Also, just to confirm - I'm safe to leave lugs 2 and 3 of the original pot connected to the PCB, right? - since these wouldn't get seen by the circuit if nothing was connected to lug 1. I have some concerns about the sturdiness of the PCB mounting without this pot being mounted, so I wanted to make sure there wouldn't be any issues if I did it this way.

Thanks!

[gcme93]

I hope this will be useful, it's one of R.G Keen's great articles:

http://www.geofex.com/Article_Folders/xprnped.htm

[aion]

I think I'm pretty well set on the expression jack, and did read that article - I'm mostly looking for input on the effects loop portion. I appreciate the link though!

[seedlings]

Aion, did you (or anyone else) make progress with this mod?  My freeze is on the bench right now.  I've been looking at the 'dogisblue' mods, and believe there are at least a few things he's leaving out.

Right now I soldered a wire onto the right side of R3, which also goes to pin 2 of the PCM3052A chip.  This is the wet signal.  However, when that signal is routed through a cap, through a vibe pedal, and back through another cap to the Effect Level pot, the effected signal is too faint to be usable.

Thanks,
CHAD

[aion]

Yep, I actually did get it working and drew up a diagram but hadn't had a chance to post it yet. Here it is:



I would not recommend the expression pedal mod - it's very difficult to find a suitable expression pedal (10kB) and I don't see it being terribly worthwhile. It's also the harder of the two because it involves cutting a leg on the pot.

I will probably modify mine to remove the expression input and just use two standard jacks for effect send and effect return instead of a stereo jack to combine send and return with a TRS cable.

Note that it is very difficult to get the board out of the enclosure so be careful and go slowly. The easiest way to get it out is to just cut the thin strip of metal that secures the power jack. I filed mine down a little bit so it's less noticeable but that was pretty hard. Better to just cut it entirely. Then the PCB will come in and out with very little trouble. Here's a picture of what I'm talking about: http://i1249.photobucket.com/albums/hh506/aionelec/IMG_0296.jpg

Here are a couple of gut shots of the completed mod, following the wiring diagram:
http://i1249.photobucket.com/albums/hh506/aionelec/IMG_0311.jpg
http://i1249.photobucket.com/albums/hh506/aionelec/IMG_0312.jpg

[seedlings]

Fantastic!  I wondered about removing R3...  My board was not as hard to remove as everyone says.  With a gentle wiggle here and there, all went well.  I will probably put this in a different enclosure so I don't drill the original.  I also bought a Roland keyboard footswitch, which will extend the footswitch off the pedal board, with no more clickey.

Gratitude,
CHAD

[aion]

Yeah - depending on your pedalboard setup, it would be much more worthwhile to use one of the jacks for a remote footswitch than an expression pedal. I might actually do that to mine now that I think about it instead of using two mono jacks for in and out. The stereo jack works well enough already, so I may as well add some new functionality that I could see myself using.

As you can see in the pictures, I did also replace the footswitch with a soft-touch one from Small Bear (http://www.smallbearelec.com/servlet/Detail?no=672) while I was in there. That was a huge improvement that I would recommend to everyone.

You've probably worked this out already, but just for the sake of completion and anyone else looking at this in the future: if you're not doing the expression pedal mod, you'd connect the 4k7 resistor (red wire) directly to lug 1 and you would not break the connection between the pot and the board.

Probably the easiest way to remove R3 is to just get a small wire (clipped resistor lead) and get it parallel up next to the resistor, then heat it up with the iron so it touches both of the pads at once. The resistor should slide right off.

[seedlings]

I found that with R3 open, the effected signal still goes to the output, though it's quieter.  This means that the dry wet signal will blend with the wet wet signal  so that it's not all wet-wet, like I hoped. 

The signal level headed to the effects send (from where R3 used to be) is also quiet enough that my vibe pedal sounds noisy, even though your schematic does work.   So, I decided to postpone the modification until I can figure out where all of the signal comes from -or- have time to incorporate a boost/buffer in the effects loop.  I did go ahead with the auxiliary footswitch jack though.  Very helpful for me.

CHAD

[p_wats]

Glad to see people chiming in on this. I modded mine in a fit of excited adrenaline and got lucky. I didn't remove R3 though and used whatever coupling caps I had lying around.

Interesting to hear that my expression pedal isn't the only one being wonky...I thought it was just something I did wrong.

Thanks for that drawing Aion! I'll have to open mine up again and see what I hacked in there. I've honestly just been scared, because I nearly broke the toggle taking it out the first time...it's a tight fit in there!

[seedlings]

Glad to see people chiming in on this. I modded mine in a fit of excited adrenaline and got lucky. I didn't remove R3 though and used whatever coupling caps I had lying around.

Interesting to hear that my expression pedal isn't the only one being wonky...I thought it was just something I did wrong.

Thanks for that drawing Aion! I'll have to open mine up again and see what I hacked in there. I've honestly just been scared, because I nearly broke the toggle taking it out the first time...it's a tight fit in there!

Thanks for your help.  You got the ball rolling on this mod!  I'm still not quite sure how your youtube video sounds so cool.  Maybe it's the pedals you're using, but all I can get to come out of my vibe pedal (JHS Warble-Tron) is a heavy hissy swirl on top of the effected signal...

CHAD

[JFDave]

I need to use the freeze in a different way ....
I would like to place it before an AKAI Unibass (Harmonizer/Fuzz for Bass) that goes to a separate input on the mixer.
So I need that when the freeze is ON, only the effect output works,
and when the freeze is OFF, only the dry output works.

In short I would like to use the freeze only the on the effect output of unibass and continue to play along with the bass in dry mode.



Can it works if I connect the bass to Send, and the Unibass to Return?

or I should replicate the same circuit on the other side of the 'R3 and put a switch in this circuit?
In this case, can I use a momentary switch (two-way, two-position) to use only the circuit's effect out or only the circuit of the dry out, alternately?

I'm a beginner and this is my first project of pedal mod, so forgive my ignorance and my bad english.

Please HELP ME!!!!

[artifus]

does your mixer have an aux send or direct out that can be put to use? mixer out to amp or pa? expression pedal? volume pedal could control snd or rtn to/from freeze?

[JFDave]

Mixer goes to PA and i haven't aux send free for use, there isn't any pedal of expression for freeze or for send/return.
I need everything just works as explained on the drawing.

[artifus]

ok so the mixer in your image represents the front of house/monitor pa system and is not part of your on stage set up? so you only ever have clean bass out to your orange amp? am i understanding this correctly? i suspect not...

[JFDave]

Exact!
I need that in the AKAI goes only the DRY signal (when the Freeze is OFF), and only the signal EFFECT OUT (when the Freeze is ON).
If I can do this, it's as if the Freeze became the HOLD function of the AKAI pedal ... a bit like a "Sustain Pedal" on a keyboard.

If I make the "Effects loop Mod", I divide Effect Output and Dry output into 2 separate Output and the Effect Output works only when the Freeze is ON, but the output Dry continues to run EVER.
For stop the Dry Out signal when the pedal is ON, I was thinking to replace the switch on the Freeze, with a momentary DPDT (Double Pole, Double Throw), but I don't know where connect it.



Then when I leave the Freeze OFF the AKAI use the DRY signal and goes to the mixer normally,
and when I turn the Freeze ON, I could "hold" only the effected signal that goes to the mixer....
I know it's a strange thing, but trust me that has its meaning....

[aion]

I found that with R3 open, the effected signal still goes to the output, though it's quieter.  This means that the dry wet signal will blend with the wet wet signal  so that it's not all wet-wet, like I hoped. 

I actually noticed a similar thing last night for the first time... I turned the Effect Level all the way down, and it still lets some of the low frequencies through, seemingly at full volume. As the Level knob is turned up, it adds the mid and high frequencies, more like a really extreme tone knob than true volume. It's almost like the frequencies are split someplace and recombined later on in the circuit. However, since this also happens with the effect loop unplugged, I wonder if an unmodded Freeze does it as well... I'm adding .44uF in series with R3 with my mod, but that's the only difference from stock.

Can someone with an unmodded Freeze confirm that theirs does this? If this is the case, it would explain why breaking the lug connection for the Level control didn't actually do the trick earlier - if the signal doesn't all pass through the Level pot on its way out. For reference, I was using a boosted signal into the Freeze, so it's a little hotter than normal, but it was nothing outrageous.

[seedlings]

I found that with R3 open, the effected signal still goes to the output, though it's quieter.  This means that the dry wet signal will blend with the wet wet signal  so that it's not all wet-wet, like I hoped. 

I actually noticed a similar thing last night for the first time... I turned the Effect Level all the way down, and it still lets some of the low frequencies through, seemingly at full volume. As the Level knob is turned up, it adds the mid and high frequencies, more like a really extreme tone knob than true volume. It's almost like the frequencies are split someplace and recombined later on in the circuit. However, since this also happens with the effect loop unplugged, I wonder if an unmodded Freeze does it as well... I'm adding .44uF in series with R3 with my mod, but that's the only difference from stock.

Can someone with an unmodded Freeze confirm that theirs does this? If this is the case, it would explain why breaking the lug connection for the Level control didn't actually do the trick earlier - if the signal doesn't all pass through the Level pot on its way out. For reference, I was using a boosted signal into the Freeze, so it's a little hotter than normal, but it was nothing outrageous.

My Freeze is back to unmodified, except for an expression pedal output.  The effect level knob changes the volume of the effect at all frequencies simultaneously, so it does not respond like a tone knob, but a volume knob for the effected signal.

CHAD

[Sacorus]

I read the above posts and thought of;

http://www.ehx.com/products/superego

[spoitras]

I'm sorry that my first act as a forum member is to revive an old thread, but I would only refer to this thread if I were to start a new one.

I'd like to add an effect loop to my Freeze, but I don't care for the expression pedal input.  In that case, couldn't I simply solder my return to the other pad of R3 instead of going straight to the pot?  This would replace R3 with the effect loops and it seem better to me.

Any thoughts?

Sylvain

[joelpass]

I'm sorry that my first act as a forum member is to revive an old thread, but I would only refer to this thread if I were to start a new one.

I'd like to add an effect loop to my Freeze, but I don't care for the expression pedal input.  In that case, couldn't I simply solder my return to the other pad of R3 instead of going straight to the pot?  This would replace R3 with the effect loops and it seem better to me.

Any thoughts?

Sylvain

I'd like to do the same for my Freeze pedal - effects loop without the expression pedal.  Can anyone provide some guidance on this?