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 »

Hi bmxguitarsbmx
I agree - there are some strange design choices made with this pedal as well as some really good design choices - the individual decoupling filters on each jfet stage and the 100n ceramic caps on each of the dual op amp power rails are excellent design choices where as the 18v dc power supply seems strange in these days of dc to dc convertors that can easily transform 9vdc into +15 and -15v DC (or less if desired - bipolar supplies would remove a lot of aluminium electros from this circuit ;-) ) - then if you study the pcb layout, most of the feedback resistors around the op amps are some distance from the IC pins - weird ? And the track routing is very messy, but I suppose if it works then so be it
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tuck
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Post by tuck »

This is great;-)
But excuse my ignorance, how do you get 1M for R33&49? No matter how I turn it I don’t get it
grey black black yellow silver 8M
grey yellow black black silver 840R

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Post by bajaman »

R33 sure looks like brown black black yellow brown - 1 0 0 0000 and 1% = 1M
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Post by Manfred »

Thanks, great work as always! :worship:

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tuck
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Post by tuck »

bajaman wrote: 11 Dec 2022, 23:53 R33 sure looks like brown black black yellow brown - 1 0 0 0000 and 1% = 1M
The first two are 33 and 49
resitorsinquestion.png
It's grey and silver. The only two resistors with grey and silver.

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Post by bajaman »

Hi Tuck
Okay R33 and R49 are the same then ?
Try measuring R33 with a multimeter and let us know what it reads ;-)
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tuck
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Post by tuck »

Hi Bajaman,
R33 and R49 are the same yes. I want to avoid soldering on the preamp because I maybe want to sell it again.
Here are all the resistors (large pictures)
resisors1-67.jpg
resisors68-129.jpg

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Post by temol »

Tuck - can you measure Q2-Q5 drain voltages?

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Post by bajaman »

Hi Tuck
No - no need for unsoldering ;-) - just put the multimeter across R33 and let us know the value (R49 would be trickier to measure because R46, R47, and R48 are in parallel with it (300k) )
R33 is connected to ground but has no other dc connection due to capacitors C15, C16, C17 and C18
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Post by bajaman »

After checking resistors - R13 and R21 are both 220k
Here is the latest schematic
cheers
bajaman
bassbutler rev 1e.zip
(93.18 KiB) Downloaded 85 times
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Post by temol »

I have drive channel on a breadboard now. 18V supply, 17.5V VB, MMBFJ201 with Vp around -0.73V -> drain voltage measures around 11.7-11.8V.
Sample with a guitar. Recorded through the audio interface, added 4x12 V30 IR. Just to demonstrate EQ range
https://www.dropbox.com/s/vl63oueer1wledx/ob2.wav

And with a bass. Sorry for the crappy sound. This bass sounds really bad.
https://www.dropbox.com/s/hjpq9tm494ucnww/ob1.wav

With MID potentiometer wired like this, rotating MID clockwise scoops the mids (pins 1 and 2 shorted). Are you sure that pins 1 and 2 are shorted and not 2 and 3? BTW - with C20 connected between RV3 and RV4 it's possible to kill the signal with all pots set to min (assuming that MID 2 and 3 are connected).

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Post by tuck »

temol:
Q1 14,64 V
Q2 10,42 V
Q3 10,88 V
Q4 10,74 V
Q5 9,70 V
Q6 14,64 V

bajaman:
R13 the red and brown bands are sometimes hard to distinguish :-)
R33 = I measured 29.19K unexpected?

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Post by tuck »

The pots:
pots.jpg
Mid is not shortened at least not directly on the pot

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temol
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Post by temol »

Looking at the picture now.. can't see any trace between pin 2 of the MID potentiometer and side pins.

can you verify how the MID potentiometer is connected? 1, 2 or 3? Does turning the MID clockwise add or scoops the mids?
OB-mid.jpg
When you set the EQ knobs to zero, does the signal drop out?

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tuck
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Post by tuck »

Yes I will do it first thing in the morning. Europe here.
Beware: the pins of the top side of the pins is not directly related to the pins of the bottom side. I should have flipped them around.

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Post by bajaman »

bassbutler rev 1f.zip
(93.11 KiB) Downloaded 83 times
Hmmmmmmm
rechecked the mid pot connections and it appears that pin 3 is not connected at all, still unsure why R33 measures so low - try using an old fashioned analog multimeter (one with a meter movement) or unsolder the end not connected to ground
In the meantime here's the latest schematic
bajaman
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Post by bajaman »

Hi Temol
cool sounding overdrive ;-)
cheers
bajaman
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Post by temol »

tuck wrote: 12 Dec 2022, 21:55 Europe here.
Beware: the pins of the top side of the pins is not directly related to the pins of the bottom side. I should have flipped them around.
Europe here too.

I think it may be wired like this.
OB-mid2.jpg
Pin 1 of the MID (blue dot) to GND. If yellow dot on your drawing indicates GND than you connected pin 3 of the MID to GND.

?
OB-mid3.jpg
OB-mid3.jpg (92 KiB) Viewed 195080 times

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Post by bajaman »

yes - that is how I see it too Temol - it is twenty minutes before lunchtime here in NZ - should be in the workshop but retired (tired) of working these days (unless it is tracing pedals like this ;-) )
Last edited by bajaman on 12 Dec 2022, 22:43, edited 1 time in total.
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Post by temol »

bajaman wrote: 12 Dec 2022, 22:29 Hi Temol
cool sounding overdrive ;-)
Hi!
Indeed :)

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