Orange Bass Butler  [schematic]

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

still very curious about R33 ?
R15 is awfully large value at 470n - are you sure it is this large ?, if so R33 could indeed be a lower resistance value, however this would load Q5 significantly if as low as 30k ? hmmmm
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Post by temol »

Also - to me, MID pot looks like B50K, not 25K. At least text on a pcb.
OB-mid4.jpg
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Are there any markings on the LDR except those visible on the picture?

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tuck
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Post by tuck »

Thonk uses the dots as model marking
Two yellow dots = RoHS compliant VTL5C3
https://www.thonk.co.uk/wp-content/uplo ... 3-RoHs.pdf
I will desolder R33… :-)
I wrote down the value that is printed on the sides. More pictures will follow.

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Post by tuck »

R33 1,017M
But how are these bands brown?!? Totally greyish not like the other resistors.

The Mid value is 25 because as mentioned the picture was mirrored and it is up side down. The values are printed on the lower side of the pot symbol on the pcb. The top of the 5 is the bottom of the 2.
Mid pins are not shorted.

Be aware that the bottom side of the pins on the top side of the pcb is turned by 180° for the clean channel because the pots are facing another direction than on the dirt channel as you can see on the first page of this thread. I marked pin 1 and 3 for that.
pots.jpg
C15 is 470nF
cap.PNG
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Post by bajaman »

Excellent work Tuck :-)
so it was 1M !
I wonder why they made C15 so large at 470n ?
47n would have been more than sufficient ;-)
SO - here is hopefully the final schematic
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Bass Butler final hopefully.pdf
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ps: i notice that all the resistors are mounted the same way around on the board - must be an ocd person that stuffed this board :-)
bassbutler final hopefully.zip
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Post by temol »

Hi bajaman.
Looks like pin 3 of the RV3 goes to pin 1 of the RV4. Pin 2 of the RV3 to C20.
OB-mid5.jpg
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Post by tuck »

Yes temol that's correct.
Unfortunately the pcb manufacturer I order at will send out his free shipping pcbs starting next year :-(
Can't verify until next year... no parts for the breadboard... horrible :lol:
Thank you guys for figuring it all out! :applause:
This is just great!

PS: somewhere I read that you can see the work of Ade Emsley by looking at the resistor placement :)
But if there is some OCD going on then why is there no mid control to even out the number of pots?
If one can add one this would be a nice modification.

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Post by bajaman »

ok - my mistake with the mid to bass connection
here is the final schematic
Tuck - the placement of the resistors is strange in many ways - I would keep the feedback resistors and HF compensation capacitors around the op amps MUCH closer to the pins than this
The fact that all the resistors perfectly align with the screen-printing is pure OCD - does Ade know something about 1% metal film resistors like Dumble knew about polyester coupling capacitors ?
Makes it VERY easy to read the colour code on them correctly as they are all the same way round ;-)
Adding a mid control to the clean channel can be done by adding another variable filter section around IC2b, but perhaps Ade deemed this unnecessary - or you could always add another dual opamp and build a high mid and low mid section around each like Bob Gallien does in his GK amplifiers - perhaps Ade ran out of board space !
Anyway - thanks for all the work and help in bringing this trace to a final schematic - an interesting concept that could be implemented quite differently by another designer - i am already looking at running the whole circuit from a bipolar 15v power supply using a dc/dc convertor powered by a standard 9v dc dc input, and this may be a good project to occupy my mind over the impending Christmas break
cheers bajaman
bassbutler final.zip
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Bass Butler pcb.zip
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tuck
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Post by tuck »

Thank you!
Please send an update regarding the bipolar 15V.
I used Traco d/dc converters in two build but why make this Bass Butler more expensive than it already is? :-)

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Post by bajaman »

Thank you too Tuck :-)
I have my own very simple and low cost dc/dc convertor circuit using the XL6007 chip ;-) - I have already simulated the drive section running on +15v and -15v (had to increase drains to 75k and modify the potential dividers between stages to maintain same gain structure) and the frequency response is identical with approximately 3dB greater headroom - same current draw through the jfets (approximately 120uA)
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Post by temol »

Any suggestion where to buy 9mm dual A500k? :) I think I would replace all the 9mm potentiometers with 16mm.

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Post by bajaman »

Bass Butler drive section up to tone stack.gif
the frequency responses at each jfet drain - PR5 is at the end just before the tone stack - notice the broad midrange peak at 2k5Hz ;-)
(PR1 is the first jfet gain stage) - ignore PR6 !
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Post by bajaman »

Hi Tuck
How about the gerber and drill files ;-) I could not upload in personal message section
Let me know if you need anything more :-)
Bass Butler final trace.zip
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cheers
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Post by tuck »

Again, thanks a lot!
16mm pots will be my choice for a pcb.
The weight can be compensated by using a Hammond 1590XX enclosure instead of a „tank“.

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Post by bajaman »

I just discovered a missing trace on my pcb layout between R80 and R81 !
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Post by bajaman »

On the subject of enclosures - the pcb will fit inside a Hammond 1590DD box BUT even using the low profile mini pots , there is still not enough space to fit the two XLR sockets - if you were to use balanced stereo jack sockets there will be enough room but the beauty of using XLR sockets is the ready availability of balanced microphone cables - still you could always build some short adaptor cables using stereo 6mm jacks to male XLRs I suppose ;-)
Another problem is the footswitch - it will not fit inside the enclosure unless the pcb is modified and the status leds moved
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Post by temol »

There's something not right around Q1. R4 connected between Gate and Source? Also, the pinout seems to be reversed. Top-right pin of the Q1 it's a Drain and should not be connected with R5.
I haven't checked other transistors yet.
OB1.jpg
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j201.jpg
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Post by tuck »

That's how it is on the original but i found this on the datasheet:
package.PNG
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https://experimentalistsanonymous.com/d ... s/J201.pdf

In another data sheet the drain is on Pin 3
https://www.mouser.de/datasheet/2/308/1 ... 811729.pdf

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Post by temol »

I know that S and D are interchangeable. But this would be the first time I see it on a pcb.

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Post by tuck »

My mistake, I drew a line to R4 in the early picture but it should connect to R3.
The latest schematic is correct but the PCB not. It was also corect in my first schematic but not in my drawing bajaman made the first layout from.
r3.PNG
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