The Robot is a low fidelity 8 bit pitch transposer with absolutely no feelings what-so-ever. It is completely synthetic and transforms any input into a spuree of resynthesized robot jargon.
Originals need a dedicated power supply as the HT8950 chip runs off 2.4-4 volts and the power section of the original will not play nice daisy chained with other pedals. To make it a little more user friendly, I've altered the power supply to use a 3.3v regulator (LM1117V33C or similar, though watch the pinout). Here's my modified schematic:
Note: I've also included 4 extra pads on the PCB layout in case anyone wanted to do the mod lvlark describes here.
Interesting....it sounds as made for a wah pedal housing with the pedal-pot wired to the control setting. I especially liked the fx / sounds produced, while turning the control-knob. Another one on my list. Awesome work!
ReplyDeleteWow, this is very nice pedal
ReplyDeleteI wish i could build one right now, but i don't have any 8950 sadly
How about bearfoot candy apple fuzz gold from tagboard for the next fuzz friday? I can verify their fixed layout ;)
Looks interesting. Can you find an actual schematic? Trying to decipher stripboard is not my favorite. haha
DeleteSure, I'll look for it and post here
DeleteThis one should work https://guitar-gear.ru/forum/index.php?app=core&module=attach§ion=attach&attach_rel_module=post&attach_id=40804
DeletePotentiometer "A" its mean linear or logarithmic?
ReplyDeleteA-Logarithmic
DeleteB-Linear
C-Anti-logarithmic
4p3t seems wrong to me, why not a 3P4T switch instead? Many layouts around seem not to work... updates?
ReplyDeletehey! awesome proyect.. is it verified? i've seen some builds with a pot instead of the trimpot for gain... i can't decide whether to do that or not as I don't know if it's really worth it... i'd love to hear someones opinion on the matter
ReplyDeleteAlso thought on adding a exp pedal input to the control knob... i think it would get some weird and interesting sounds out off the pedal... specially in arpegiator mode
ReplyDeleteDidnt work for me i get low volume and nothing i do can fix it
ReplyDeleteit doesnt work well it needs a negative 3.3 power supply to work propperly i think i built it and is not working well
ReplyDeleteSomeone has verified this?
ReplyDelete1000 %
ReplyDeleteVerified
ReplyDeleteUpdate: replace potentiometer of 100k by 1k for correct operation of VOLUME, JOIN PIN 1 AND 2 OF CONTRO, DO NOT LEAVE
CONTROL PIN 1 IN SOLITARY
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DeleteWhat does this do though? It doesn't seem to make a difference either way.
Deletehttps://www.youtube.com/watch?v=gjJ7p9m8E3k&feature=youtu.be
ReplyDeleteNice! Thanks for verifying
DeleteHow much Ohms have you set on trimmer?
DeleteHi, do you think a HT8970 could also work? Cound find a HT8950. Thanks in advance!
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ReplyDeleteHow much Ohms have you set on trimmer?
ReplyDeleteHi ! Thanks for the layout and thanks Dan for your advices !
ReplyDelete- I have set the trimmer at 3/4 , because at full level the noise is heavy, but this control is (for me) not usefull.
- Remove 470pF on output TL072 is a good way to have some trebles, I have put a switch between the two possibilities.
- I confirm that A1k for volume is necessary instead of A100k for a good range of control
- Instead of LM1117 I used a LM1086CT-3.3, same pinout.
This layout is OK for wire the 4P3T :
http://johnkvintageguitars.homestead.com/Effects/Fuzz-ODs/DBA/01-DBA_ROBOT_VERO.png
Simon
Many many thanks!!!
DeleteAnd what about normal mode, btw? In the wiring you gave link to there's two positions for arpegiator. I did everything like pictured.
DeleteHow do you wire the 3p4t?
ReplyDeleteHi all ! Someone has verified this one with the mod ?
ReplyDeleteI'll be trying with a rotary switch 1P4T in the right side of the HT8950 ...
Puede usarse con daisy chain?
ReplyDeleteHas anyone ever successfully added an expression input for "control"? I've been trying for a while, and it primarily just behaves like the pot is fully clock-wise (0 ohms basically) with only the tiniest sweep, as soon as you plug anything in. It's all crazy sensitive to interference. I even tried making a special trs cable with shielding between the wires, but to no avail.
ReplyDeleteFor those wondering where to get the HT8950, Ali Express has them cheap and they work.
ReplyDeleteAs for the 4P3T, you can also use a 3PDT on/on/on switch in conjunction with diodes (since SW A goes to ground) as follows: pin 1 into diode cathode into SW3, pin 2 directly into SW A, pin 3 into cathode into SW 2, pin 4: (not connected) NC, pin 5 directly into SW 1, pin 6: NC
Actually, after watching a few videos on this pedal, it looks like it would need a switch that goes four ways instead of three—a 1P4T (or 2 or 3P4T, wouldn't matter). SW A is ground, and the three other connections are for three different pins of the HT8950. I found that the arpeggio effect occurs when none of those three pins are grounded, and the other three settings are accessible by grounding only one of the three other pins. I managed to use two DPDT switches instead.
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