LAL - Oscillo Fuzz (Lastgasp Art Laboratories)  [traced]

General documentation, gut shot, schematic links, ongoing circuit tracing, deep thoughts ... all about boutique stompboxes.
User avatar
Greg
Old Solderhand
Information
Posts: 3047
Joined: 03 Nov 2007, 09:35
my favorite amplifier: Tophat Emplexador & Supreme 16.
Completed builds: LOTS..
Location: Australia
Has thanked: 65 times
Been thanked: 164 times

Post by Greg »

Steven_M wrote: Perhaps it's in reference to the 4PDT. Arent those still pretty unreliable? If you mounted it back in the case and set it up too high, it would probably be very easy to break.

This is a guess, but judging by the giant washer used on the switch (inside) from the gut shot... :hmmm:
No, the Fujisoku switches are good quality.. probably as good or better than the common 3PDT I would say.
Maxon use them in the AD999 Delay pedals.
culturejam wrote: We are equal opportunity exposure artists.

User avatar
Luggi
Information
Posts: 2
Joined: 17 Dec 2010, 17:36
Has thanked: 1 time
Been thanked: 5 times

Post by Luggi »

Hi!
I have a question regarding the CV Pedal jack wiring:

What kind of jack is used for the CV in? The drawing in the schematics and the pdf by seele confuses me a bit...
I thought it's a stereo jack but there are 4 points with connections in the scematics/pdf but a stereo jack has just got 3 lugs...

Can someone please tell me how to wire the jack?

thanks!

User avatar
mysticwhiskey
Solder Soldier
Information
Posts: 227
Joined: 03 Jul 2010, 09:55
Location: Adelaide, Australia
Has thanked: 42 times
Been thanked: 175 times

Post by mysticwhiskey »

It's a switched stereo jack, with switches on the tip and ring connections that are closed when no jack is inserted. When a jack is inserted, the switches are open. The connections from the jack would be:

Tip = to R3
Tip switch = to Adjust pot pin 2
Ring = to switch 1's pole
Ring switch = to Adjust pot pin 3
Sleeve = to Adjust pot pin 1 and switch 4's pole

Soulsonic's notes say that the sleeve of the jack must be isolated from the chassis.

User avatar
stykerwolf
Information
Posts: 12
Joined: 06 Aug 2010, 19:30

Post by stykerwolf »

can someone upload the other files? This fuzz sounds really awesome

User avatar
amnesiac
Information
Posts: 10
Joined: 07 May 2009, 11:41
Has thanked: 10 times
Been thanked: 1 time

Post by amnesiac »

Does anyone happen to have the oscillo fuzz pdf as it is no longer available in previous post? Thanks

User avatar
Luggi
Information
Posts: 2
Joined: 17 Dec 2010, 17:36
Has thanked: 1 time
Been thanked: 5 times

Post by Luggi »

Have fun! :)
Attachments
Oscillo Fuzz.pdf
(1.1 MiB) Downloaded 737 times

User avatar
candletears7
Solder Soldier
Information
Posts: 194
Joined: 05 Oct 2008, 12:02
Has thanked: 3 times
Been thanked: 5 times

Post by candletears7 »

I'm really digging how the spdt's are positioned on that perf layout to sit right in. Nice! Thanks for the layout! I'm gonna give it a go.
:thumbsup

User avatar
lopsided
Information
Posts: 3
Joined: 30 Jan 2011, 21:49

Post by lopsided »

hello,

I have been looking at the schematic and layout, bur I do not understand the D4.
It has a Zener symbol, but google searches show that 1N771a is a germanium diode.
Can somebody please explain?

Thanks

User avatar
lopsided
Information
Posts: 3
Joined: 30 Jan 2011, 21:49

Post by lopsided »

Sorry for the bump, but could someone please answer my diode question?
I have it currently on my table, am close to finishing it and would love to clear the nature of the 1N771a.
Thanks.

User avatar
bubstance
Solder Soldier
Information
Posts: 168
Joined: 07 Jul 2009, 03:10
my favorite amplifier: Lab Series L11
Completed builds: more than a few, less than a ton
Location: uncanny valley
Has thanked: 83 times
Been thanked: 116 times
Contact:

Post by bubstance »

It's probably a symbol error in the schematic. You're good.
powered by 9front

User avatar
lopsided
Information
Posts: 3
Joined: 30 Jan 2011, 21:49

Post by lopsided »

I have tried to make a vero layout for myself. The switches are spdt but shown as dpdt as mine are three columns wide.
It is unverified and I am myself experiencing some problems. I have build it also on breadboard and am having the same problems so I am not sure if I am overlooking something or if there might be some problem with the schematic (members/soulsonic/schematic/LAL_SuperOscilloFuzz.GIF).
I get an extreme fuzz plus oscillation controllable with the adjust pot and guitar volume pot.
Switches 1,4, and 6 change the tone a bit and also the pitch of the oscillation. So this seams about right.
But switches 2,3,5 work only in one position. In the other I get either nothing or very low output fuzz with no oscillation.

Switch 3 works only when switched to the 10K resistor. I can make the other position work with a resistor as low as 1K5, but with lower values or with no resistor at all(as on schematic) it does not work.

Switch 2 works only when connected to the collector of Q3. Not when connected to the emitter.
Switch 5 works only when connected to the collector of Q2. Not when connected to the emitter.

I would really appreciate if a successful builder of this fuzz could give me any insight on these problems.
Would be also grateful for any comments on the Q2-Q3 section, I am having a hard time trying to understand how it is supposed to work. (especially the bias of Q3...)

Thanks a lot!
l_s


Image

User avatar
knutolai
Information
Posts: 14
Joined: 02 Sep 2011, 14:47
Been thanked: 3 times

Post by knutolai »

is the 1N771A really necessary? It looks to me like its only a part of the ON/OFF indicator LED. Wouldn't removing the component all together give the same result in lighting and sound?

User avatar
Chewbacca
Information
Posts: 22
Joined: 13 May 2012, 07:51
my favorite amplifier: Madamp A15Mk2 TSX Modded
Location: Eisenach, Germany
Been thanked: 8 times
Contact:

Post by Chewbacca »

Is anybody still watching this thread?
I have built my own Vero but I seem too run into similar problems as lopsided.
S1 S4 and S6 seem to do what they are supposed to do.
Oscillation only occurs when S5 and S2 are both switched to collector of Q2 - in other positions it is just a fuzz.
With S5 switched to the collector of Q2, switching S3 to the position without the 10k kills the sound completely. I would have imagined something else happening there.
So could anyone with an original unit please tell what positions of S2,3 and 5 actually do.

Also: I have used KC1815Y because I had them - the schematic calls for SC1815GR. Does it make difference?

Thanks
Here is a picture of my Vero layout. I left out the wiring for the Footswitch and for the LED for now.
I also omitted the CV Jack
I don't think the 1N771A has anything to do with the sound of the pedal - it is just for the LED
Attachments
SOF.png

User avatar
B3ar
Breadboard Brother
Information
Posts: 98
Joined: 24 Jan 2010, 16:11
Has thanked: 30 times
Been thanked: 2 times

Post by B3ar »

knutolai wrote:is the 1N771A really necessary? It looks to me like its only a part of the ON/OFF indicator LED. Wouldn't removing the component all together give the same result in lighting and sound?
On a similar tip, how about eliminating the whole indicator sub-circuit (D4, D5, R14), allowing use of a 3pdt switch? Am I that bad at powering issues that I am missing some obvious ill effect to doing that?

User avatar
soulsonic
Old Solderhand
Information
Posts: 3880
Joined: 27 Jun 2007, 03:38
my favorite amplifier: Traynor YVM-1
Completed builds: too many!
Location: Morgantown, WV
Has thanked: 183 times
Been thanked: 468 times
Contact:

Post by soulsonic »

The 1N771 is only for the LED, you don't need it.

I don't remember how the switches respond, because it has been so many years since I've played with it. Because of its oscillating nature, you probably should use a layout similar to the original pcb if you want it to sound the same. Stripboard is definitely not recommended here.
"Analog electronics in music is dead. Analog effects pedal design is a dead art." - Fran

User avatar
Sesh
Information
Posts: 29
Joined: 02 Jul 2020, 13:07
Has thanked: 18 times
Been thanked: 5 times

Post by Sesh »

Chewbacca wrote: 24 Dec 2014, 18:44 Is anybody still watching this thread?
I have built my own Vero but I seem too run into similar problems as lopsided.
S1 S4 and S6 seem to do what they are supposed to do.
Oscillation only occurs when S5 and S2 are both switched to collector of Q2 - in other positions it is just a fuzz.
With S5 switched to the collector of Q2, switching S3 to the position without the 10k kills the sound completely. I would have imagined something else happening there.
So could anyone with an original unit please tell what positions of S2,3 and 5 actually do.

Also: I have used KC1815Y because I had them - the schematic calls for SC1815GR. Does it make difference?

Thanks
Here is a picture of my Vero layout. I left out the wiring for the Footswitch and for the LED for now.
I also omitted the CV Jack
I don't think the 1N771A has anything to do with the sound of the pedal - it is just for the LED
Did you ever fix this?

Necrobumping this thread! There seems to be a lot of people experiencing the same problem as Lopsided over at Dirtboxlayouts vero/stripboard blog:
https://dirtboxlayouts.blogspot.com/202 ... 7388038866

Did anyone ever fix the issues?

User avatar
seele
Information
Posts: 22
Joined: 06 May 2010, 21:46
my favorite amplifier: Sunn Model T
Location: Germany
Has thanked: 14 times
Been thanked: 4 times

Post by seele »

How about using the perfboard layout? It’s nearly identical to the original and has board mounted switches... 8)

User avatar
Sesh
Information
Posts: 29
Joined: 02 Jul 2020, 13:07
Has thanked: 18 times
Been thanked: 5 times

Post by Sesh »

seele wrote: 08 Apr 2021, 08:26 How about using the perfboard layout? It’s nearly identical to the original and has board mounted switches... 8)
Is it verified, though? It seems to be an issue with the schematic

User avatar
Sesh
Information
Posts: 29
Joined: 02 Jul 2020, 13:07
Has thanked: 18 times
Been thanked: 5 times

Post by Sesh »

OK! The good folks at Dead End has traced the Oscillo Fuzz. It appears that Q2 should be a PNP - this fixes the issues with the switches.

User avatar
Gila_Crisis
Resistor Ronker
Information
Posts: 404
Joined: 01 Jul 2007, 08:37
Has thanked: 3 times
Been thanked: 124 times
Contact:

Post by Gila_Crisis »

I've built the LAL88, using the PCB by Dead End FX (brilliant stuff)!

For the transistors I used 2SC1518 for Q1 and Q3 (I follow Dead End schematic for part coding), and the Q2 is a PNP BC327.
For Q1 and Q3 I have also tried some bc337 as suggest by Deadend, but I didn't hear a great difference.
The sounds I get are similar to the demo videos you find online. It's indeed a super cool fuzz, with a lot of amazing oscillations (it's very reactive to guitar's controls) but also offers some very classy non-oscillating fuzz tones as well!

Now the well known problem: indepently from the other switches, SW3+SW5 is the only combination that doesn't work at all (it'll "kill" the pedal sound). But if you engage SW2 as well, then the fuzz will work again as it should.

I had a chat with Dead End FX and they told me this issue is normal: Also the original one they used to trace the circuit has the same problem.
An ILF user who owns the orginal 88 confirmed the "issue", and LAL website & 88's manual state that: "*In some cases, no sound may be emitted at all."

I've found this 88 video on youtube. At the 07:03 mark there is the "forbidden" switch combination happening!
The guy switches 3, then 6 (still works) and then 5 (all other switches are off). After 5 the pedal is muted for a tiny bit, until he switches 2, and then 88 fuzzes again. My clone behaves the same way!
Zwischen Ordnung und Chaos fangt die Musik an

Post Reply