bixonic expandora

[digi2t]

Gus, thanks for that. Your info, along with all the rest was what fueled me during this road trip. I still wonder though if the 2206 has some particular properties that make it best for this circuit, but other than the integrated resistor, the voltages say no.

Chugs, THANK YOU!!!! Greatly appreciated. One for the breadboard... as soon as I figure out the components. IC4 looks like quad opamp EQ section? IC5, some kind of CMOS thing going on?

[anotherjim]

IC4 looks like quad opamp EQ section? IC5, some kind of CMOS thing going on?

IC looks like a level indicator to me -  a ladder of 4 comparators with LED output. I'm not sure about the base of Q2 - it would clamp the output of IC3-7 when the switch is closed? A resistor could be missing?
IC5 might be a 4049 inverter. Have seen something similar using them as voltage controlled R with one power pin floating at signal level (pin 7 in this case).

[digi2t]

IC4 looks like quad opamp EQ section? IC5, some kind of CMOS thing going on?

IC looks like a level indicator to me -  a ladder of 4 comparators with LED output. I'm not sure about the base of Q2 - it would clamp the output of IC3-7 when the switch is closed? A resistor could be missing?
IC5 might be a 4049 inverter. Have seen something similar using them as voltage controlled R with one power pin floating at signal level (pin 7 in this case).

Dang... You're right on the comparator. It's for the flashing LED in the pedal. I forgot about that. Thanks Jim!

[digi2t]

Early Christmas gift...

Just so were clear;

Version 1, the "Script" model. No gain switches, just a straight forward overdrive. -



Version 2, the 2000 model, two internal switches for gain only -



The Godlyke reissue version (2000R, version 3, external switches, two for gain, one for guitar/bass voicing);







The last version (2001, version 4, all switches replaced by "Drive" pot);











My impressions;

I'm not going to cover the version 1, since I haven't tried it. I haven't tried an original v. 2 either, but right now I have a JMK board on the bench. It's representative of version 2 of the Expandora, with a single 4558, twin LM308's (I'm using LM108's), and the PC419 (I'm using an H11F1). Comparing it to the v.3, there are very obvious tonal differences. Quite honestly, given the choice between twin LM308's, or a dual op amp such as the TL072, I'll roll with the 308's any day of the week. Though they're similar gain-wise, the 308's have a bit of a rounder tone to them. Another thing, the version 2 is quieter too, especially when you kick an amps overdrive channel with it. Version 3 is much hissier, though remember, I'm comparing it to a clone of the v.2. Regardless, listening to videos of original v.2's, my clone is pretty close to it. Overall, v.2 is quieter than the v.3. The "Forbidden" modes sound different too. For that, v.3 wins the contest. While v.2 can be quite the beast in forbidden mode, with all kinds of roar, feedback, and cacophony of noises, v.2 offers a more usable effect at the lower drive settings. With run-of-the-mill humbuckers (7K to 8K range), I could get my Jack White on no problem. I could really modulate between gating notes, and screaming feedback at will, just by adjusting the guitar volume. It's quite addictive, and loads of fun. As many have reported, the forbidden mode isn't really usable on the v.2 units, though v.3 makes it quite interesting. Not sure if it's differences between the 072 versus the 308's, or the H11F1 versus the PC419. As for the schematic, I'm pretty sure it's going to be "replace dual 308's by single 072", along with some other component value changes here and there, but I'll confirm this over the nect couple of days/weeks.

Version 4 is a completely different animal. No gain switches, and alas, no "Forbidden" mode. A straight up mild overdrive, to crunch, to all out fuzz machine. OK... the flashing VU LED's are cool. I'm like a moth to a match, what can I say. It's the quietest of the bunch, especially if you're going to be goosing an overdrive channel. While some of the same tonal quialities of v.2 and v.3 can be dialed in, it's got it's own voice(s) as well. The "expandora" effect is still there though, giving you great clean-to-grind-to-clean control, simply by twisting the guitar's volume. The opto, or OPTOS in this case, are a pair of Sharp PC817's, encased in a single package. The actual Sharp number for the dual package is PC827. Interestingly enough, the PC817 is a family of optos, encompassing 1, 2, 3, and four channel models. Hey... ya learn something new everyday. A quick Google tells me that they're still widely available, and still really cheap. Maybe they can be used in the v.2 or v.3 models as well? We'll see. Anywho, v.4 is a nice overdrive in it's own right. Covers a boatload of sonic territory, so no regrets on the purchase. Besides, was worth the price of admission, just to gander at the guts. I'll compare it to the published schematic over the next couple of day/weeks, just to confirm the schematic.

[Chugs]

Thanks for the info!

[digi2t]

Here is the verified schematic for the 2001 model. Many thanks to Chugs for the original. I did a little cleaning up, and there were a couple of errors that I corrected.



I suppose if one really wanted the "Forbidden" setting of the v2 and v3 versions, it could be incorporated into the clone. I would try opening the circuit between C5 and the IC5 - pins 6-7 connection. I'll try it when I get to that stage, or if someone beats me to it, let me know how it works.

Off to work on the v3 schematic now. Damn! I hate double sided boards!

[digi2t]

Running on inspiration from the Montreal pedal show, I've completed the trace of the version 3 unit.
Here you go folks...



That's it. Stickin' a fork in this one. 

[Chugs]

Thanks!

Are C3 and R2 necessary? All versions have these parts but seems they may be superfluous?

[digi2t]

Thanks!

Are C3 and R2 necessary? All versions have these parts but seems they may be superfluous?

Couldn't tell ya buddy. As my bro Jimi would say, that's above my paygrade.

Maybe one of our house gurus can chirp in here?

[pinkjimiphoton]

whaaa-aaat, no vero??   

[digi2t]

whaaa-aaat, no vero??   

I've found that the guys over at Tagboard are a lot faster on the trigger than me when it comes to whipping up veros. I still draw them up, but I've slowed down of late, tending to wait to see if Alex and the gang spit something out first.

[pinkjimiphoton]

hahah, i was just teasing bro... after looking at the epic ludwig vero this is nothing!

i hear ya on tagboard... i use their layouts on MY builds of my circuits cuz they are usually cleaner than my widdle bwain can figger out.

nice to see a proper and verified schematic too! well done bro! i crack this cyber beer to thee

[Kennt82]

   Reposting digi2t's v3 reissue schematic, as it's been missing.



  It answers the mystery of what the 3rd  "guitar/bass" voicing  does.  A larger cap is switched in at the very end. I built mine on Sabro's v1 layout and changed the high pass values before the output to match v3's, along with switch.

  Since his trace, Tagboard has put up layouts for Expandoras v1, v2 and a hybrid version Dino came up with. This v3 schematic should complete the set.   He added a lot of helpful hints at the comments over there.

[mac]

I wonder if it would make any difference to use a diode instead of Q1 @ IC3_B 

mac

[rankot]

Early Christmas gift...
My impressions;

I'm not going to cover the version 1, since I haven't tried it. I haven't tried an original v. 2 either, but right now I have a JMK board on the bench. It's representative of version 2 of the Expandora, with a single 4558, twin LM308's (I'm using LM108's), and the PC419 (I'm using an H11F1). Comparing it to the v.3, there are very obvious tonal differences. Quite honestly, given the choice between twin LM308's, or a dual op amp such as the TL072, I'll roll with the 308's any day of the week.

Is it OK to use H11F1, I suppose you had an opportunity to compare it to PC419. I have few of the H11F1s on hand, but PC419 are not available for me

[BetterOffShred]

I'd sure try.   You may have to mess with the CLR a little to get the appropriate response.  I could be wrong

[nation]

Codtone build documents from the now dead link in the 2nd post:

https://www.scribd.com/document/235013206/Codtone-Expandra-Build-Doc-Notes-and-Mods-Rev-2-0#download

[pinkjimiphoton]

thanks mate, but any way ya can just up it as a pdf or something somewhere? i mean zero offense, but man, i am sick of signing up for accounts just to look at shit

[rankot]

There's much better service called docdroid.net, it's free for PDF sharing.

[nation]

thanks mate, but any way ya can just up it as a pdf or something somewhere? i mean zero offense, but man, i am sick of signing up for accounts just to look at shit

I feel ya. I actually found it googling. Anyway here's pdf version for downloading

https://drive.google.com/open?id=1GXcNKwDzdOBkgw4rW4wJi-zNVlS-rXUF