MXR - Bass Octave

All about modern commercial stompbox circuits from Electro Harmonix over MXR, Boss and Ibanez into the nineties.
Stompmodder
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Post by Stompmodder »

Hi,

This is the pedal i want to RE. Currently i work on the suface mont pcb to extract the schematic. If somebody is interested about this project, let me know.
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MXR bass octave solo side.JPG
MXR bass octave comp side.jpg
367917.jpg
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Alex Frias
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Post by Alex Frias »

Always interested... But could you tell us what your impressions about its tracking?

Stompmodder
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Post by Stompmodder »

Alex Frias wrote:Always interested... But could you tell us what your impressions about its tracking?

This is my friend pedal, and when i try it, i've fond the best clean octave down effect for bass. Better than boss OC-3 in my opinion. When the Pedal will be RE. I need you to test and see if my schematic is functionnal. I know this project is not for beginner but many musicians are looking for a good clean octaver schematic. The PCB is surface mont. Ic's and resistors are labelled. Capacitors are not labelled BUT can be read with a capacitor meter.
5 IC's , 6 TRANSISTOR, 3 DUAL DIODE IC'S AND A BUNCH RESISTORS AND CAPS. I feel this project can be done with traditional parts.

puppiesonacid
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Post by puppiesonacid »

looks very cool man, I definetly would be intrested to see it when you reverse this one.


puppiesonacid

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Post by Stompmodder »

This is my contribution to this forum. If you test this schematic, please report. I put a lot of energy to extract the schematic on the SM PCB . This effect track very well any notes on the bass but have some miss with the low E and F. Sound better than Boss Octavers. Enjoy!
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mxr.rar
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puppiesonacid
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Post by puppiesonacid »

didnt the shin ei something or other have a really good lower octave tracking? is the mxr close to this or something else? just wondering...

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soulsonic
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Post by soulsonic »

Thank you, Stompmodder - excellent work!
I have been studying octave circuits recently, and this is a valuable addition to my notes.

arctumeda
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Post by arctumeda »

hum I'm searching to make this pedal on a stripboard. Has anyone a layout for this pedal, or I must to made it myself ?

Regards

Guillaume

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modman
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Post by modman »

Great work Stompmodder (welcome btw)
I added this schematic to the index page here.
Please, support freestompboxes.org on Patreon for just 1 pcb per year! Or donate directly through PayPal

s_scud
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Post by s_scud »

Please! there is somebody whit a big heart who can make a vero for this???

:thumbsup
THANKS!!!

Alt-me
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Post by Alt-me »

Hey guys, can somebody please PM me the Schematic?

Much appreciated

OC26
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Post by OC26 »

Excellent. I wasn't aware of this.

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mictester
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Post by mictester »

s_scud wrote:Please! there is somebody whit a big heart who can make a vero for this???

:thumbsup
THANKS!!!
I'll get one done in the next few days. I'm a bit busy at the moment, but I'll get it done!
"Why is it humming?" "Because it doesn't know the words!"

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mictester
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Post by mictester »

mictester wrote:
s_scud wrote:Please! there is somebody whit a big heart who can make a vero for this???

:thumbsup
THANKS!!!
I'll get one done in the next few days. I'm a bit busy at the moment, but I'll get it done!
However, a look at the circuit schematic suggests a few errors. The use of the 4013 and the 4016 aren't quite right. I'll have to work out how it's meant to work...
"Why is it humming?" "Because it doesn't know the words!"

lsantis
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Post by lsantis »

nothing new about this??

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Brainbender
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Post by Brainbender »

too bad, i'm also interested...

pinio
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Post by pinio »

Me too....

seedseed
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Post by seedseed »

me three

retna
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Post by retna »

i've got an original issue/version of that pedal, i just need to dig it out, and take some photos of it if you want? if i remember correctly, it really didnt sound that 'great', hence why it never made it on to my gigging board(s). oh well... :?

eric

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Post by Stompmodder »

mictester wrote:
mictester wrote:
s_scud wrote:Please! there is somebody whit a big heart who can make a vero for this???

:thumbsup
THANKS!!!
I'll get one done in the next few days. I'm a bit busy at the moment, but I'll get it done!
However, a look at the circuit schematic suggests a few errors. The use of the 4013 and the 4016 aren't quite right. I'll have to work out how it's meant to work...
Hi guys,

This is a block schematic of the circuit. I'll try to explain how the circuit work. The schematic have maybe few errors but the use of 4013 and 4016 are correct.

The most important block in this octave pedal is the tracking circuit. (TRACKER CIRCUIT) in the file. This block convert the fundamental frequency of the input signal into
two digital signals. SET of 1 or 9V and RESET for 0 or 0V. These 2 signals put together generate exactly the same frequency of the fundamental frequency. Except this signal is a SQUARE SIGNAL.

Example: if you play an A note:
Fundamental frequency is 440Hz sine wave. The TRACKER circuit generate a 440HZ SQUARE FREQUENCY.

The Frequency Deviser block use the IC 4013 to devise the 440HZ to 220HZ. This square frequency is now a octave down for the fundamental frequency.

If you try to listen a audio square signal into a speaker, you will hear a electric razor type of sound. To Smooth this frequency, we use

The block SQUARE TO SINE WAVE. This block is designed to convert this frequency to a new sine wave of 220Hz frequency.

This frequency is now Mixed to the original frequency. Each signal can be adjusted individually by two potentiometers DRY and OCTAVE.

I hope that can help and sorry for my bad english!

Stompmodder
Attachments
mxr bass octave.jpg

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