Non-working Bassballs

[Baran Ismen]

I see that this circuit is somehow cursed and works (or not) however it desires lol. All 3 threads, I read different voltage values for IC1 per pin.

Not cursed it just needs some specific behaviour from the opamp.    Many circuits need specific opamps as they push certain operational boundaries.   I think the problem here is the circuit has a subtle design flaw in that only *some* LM1458's work - that's an annoyance to DIY'ers.   Back in the day EHX might have used a specific brand.

The easy way out is to use one of the opamps people have found to work.  The mod I suggested tries to make the circuit more robust and work with more opamps.   You might need to use two or three diodes.  It's worth trying.   More than three and you will probably need to design out the problem altogether.

Mark Hammer suggests something about being one of the diodes in opposite, I wonder it would be the case.

It's not a circuit "mistake".  It just life with opamps in these types of circuits.   Look up single op amp rectifier - the single supply versions all require "special" opamps.

Ok ill give a try tomorrow. Its just a 100k resistor and 2x 1n914 diodes in series, fed with 9v and goes to pin5 right? I wonder how its gonna work while pin5 is still connected to gnd.

Yet finding one or more spesific 1458 will be a pain in the back really. How will i know if its gonna work or not?  mooer released an smd version of this pedal even, it should not be that complicated 😮‍💨

[antonis]

to see who's paying attention?

Definitely not me..
Can't pay attention to 4 or 5 different schematics and 2 or 3 different layouts..

I beg for your clemency,,

[Rob Strand]

Ok ill give a try tomorrow. Its just a 100k resistor and 2x 1n914 diodes in series, fed with 9v and goes to pin5 right? I wonder how its gonna work while pin5 is still connected to gnd.

You have to connect pin 5 to the point where the diode and resistor meet (not ground) - it's marked on the schematic I drew.   The whole idea is not to have pin 5 ground but to have it at a voltage above ground.

If your LM1458 is not a real LM1458 then two diodes probably won't be enough.   Your IC1 pin 7 measure makes me a bit suspicious it's not a real LM1458, more like a TL072 or some mysterious made-in-China generic opamp.

If you had an LM358 hanging around you could just plug it in and then you would know the unit works or not.   No need to try any mods.  If the LM358 doesn't work then it's likely you have a bit more debugging to do.

Yet finding one or more spesific 1458 will be a pain in the back really. How will i know if its gonna work or not?  mooer released an smd version of this pedal even, it should not be that complicated

There's lots of options for better opamps.   Especially if it's SMD.   It's a solvable problem with one of the more modern opamps.

[Rob Strand]

This idea might be a better alternative.  It designs out the problem and allows pin 5 to be biased at VREF.



You maybe need to tune R6.  Smaller R6 values will lower the idle DC voltage at the opamp output.  220k to 390k are most likely values.

Forgot to mention, for a long term solution  the VREF cap C101 might need to be increased.

EDIT: update R6 range.

[Baran Ismen]

http://tagboardeffects.blogspot.com/2013/06/ehx-bassballs.html

Even though being an unmodified layout, some folks here had the very same problem with me, even with the same voltages. Buts its quite old and i doubts no one would answer about their findings.

[Rob Strand]

http://tagboardeffects.blogspot.com/2013/06/ehx-bassballs.html

Even though being an unmodified layout, some folks here had the very same problem with me, even with the same voltages. Buts its quite old and i doubts no one would answer about their findings.

Speaking as a electronics designer I'm not surprised at all since it is operating the opamp outside of the guaranteed working range.  It's a design asking for trouble.   With the number of posts about the issue it's clear there is trouble to be found.

There's plenty of possible solutions:
- different opamp, different brand of opamp
- biasing pin 5 a bit ; my first suggestion.  a "minimal workaround"
- biasing pin 5 a lot and then adjusting the output ; my second suggestion, fix by design, works with most opamps.
- bias pin 5 in-between those two cases and add voltage drop at the output with some extra diodes.
  That's like my first case by with more diodes, then add some diodes at the output -
  that would be more diodes in series with D1 (pedalPCB low-baller schematic).
  A similar idea is used in Dr Quack, which is what Duck was referring to a few posts ago.

The aim of the above is to make the rectifier work, which in many cases it's not working at all.    You need to do something because the original design isn't guaranteed to work.

In the original bassballs there is a distortion output taken from IC1B.   In order not to affect the tone it's a good idea to stick with the LM1458.  If the distortion output isn't use and IC1B is only used as a detector to drive the attack/decay filter then you don't have to worry about the sound of the opamp itself.

[Baran Ismen]

Just as a warning the part designations on the two schematics are different even though the circuit itself is basically the same.  We should stick to the pedal PCB designations otherwise there's going to be a lot of confusion 

OK.. Both show pin5 of IC1.2(or B) grounded..
So, what's the purpose of O-13 cut..??

What's the O-13 cut?

I'm pretty sure there's something wrong with the IC1b (pins 5, 6, 7 ).

As I mentioned before this measurement looks off, it should be around 0V to 1V.

IC-1 (1458)
7- 8,54

It could also explain why there's no signal in one of the switch positions (down = Distortion mode)

Last night I finished my 2nd project with great hopes, however all I got was a DI sound mixed with a rather hi-freq hiss, and nothing else. I've followed the below project. Also the dist. switch (which is an on/on, 3-pin switch) totally kills the sound when switched on one side.

The opamp is operating with the inputs are near 0V.  Perhaps the IC1 LM1458 is faulty, or doesn't work like an old-school LM1458, or isn't a real LM1458.   On some opamps pushing the input towards ground can cause a phase-inversion at the output - that might explain the 8.54V on IC1 pin 7.

Maybe you should try something like this as a test/debug workaround:


The idea is to put some DC bias on pin 5 without affecting the operation of the ckt.

Progress!

I've done that bias-thing you mentioned with two 1n4148n diodes and 100k resistor, didn't make any difference on pin5, but on pin7 it did a lot. The dist. section wasnt working again but some of the pots started working and I got a richer filter sound that decayed within seconds upon touching.

[Rob Strand]

One of these should work:

direct link
https://i.postimg.cc/wMCQG7Xs/bassballs-pin-5-bias-hack-reupload.png

direct link image in forum


normal thumbnail


FYI, the method with the resistor is more like to work.

[Baran Ismen]

Progress!

I've done that bias-thing you mentioned with two 1n4148n diodes and 100k resistor, didn't make any difference on pin5, but on pin7 it did a lot. The dist. section wasnt working again but some of the pots started working and I got a richer filter sound that decayed within seconds upon touching.

[Rob Strand]

I've done that bias-thing you mentioned with two 1n4148n diodes and 100k resistor, didn't make any difference on pin5, but on pin7 it did a lot. The dist. section wasnt working again but some of the pots started working and I got a richer filter sound that decayed within seconds upon touching.

pin 5 should be at about 1.0V to 1.2V, that's set by the diodes
If pin 7 has moved to a lower voltage that is good progress, if the opamp has a wide swing it might be a little higher than the pin 5 voltage.  However it could be anything between 1.2V and 2V region, limited by the opamp swing.

If you try three diodes you might need to add another diode in series with D1.   Beyond that it's probably more economical to a red LED but you will need to drop the 100k resistor value.  If it's working with two diodes you can leave it.

[Baran Ismen]

I've done that bias-thing you mentioned with two 1n4148n diodes and 100k resistor, didn't make any difference on pin5, but on pin7 it did a lot. The dist. section wasnt working again but some of the pots started working and I got a richer filter sound that decayed within seconds upon touching.

pin 5 should be at about 1.0V to 1.2V, that's set by the diodes
If pin 7 has moved to a lower voltage that is good progress, if the opamp has a wide swing it might be a little higher than the pin 5 voltage.  However it could be anything between 1.2V and 2V region, limited by the opamp swing.

If you try three diodes you might need to add another diode in series with D1.   Beyond that it's probably more economical to a red LED but you will need to drop the 100k resistor value.  If it's working with two diodes you can leave it.

Current readings are as below (this probe touched to pin 7, not 5);

IC-1 :

1- 4,06
2- 4,06
3- 3,97
4- 0
5- 0
6- 0,67
7- 0,75
8- 8,1

IC-2 :

1- 4,06
2- 4,06
3- 4,05
4- 0
5- 4,05
6- 4,06
7- 4,06
8- 8,1

[Rob Strand]

Yes, something weird going on with pin 5.

What voltage do you measure across the two diodes, ground to the anode of the top diode?

Pin 5 is connected to the diodes so you should see the same voltage.

Pin 6 and 7 voltages look OK.

[Baran Ismen]

Yes, something weird going on with pin 5.

What voltage do you measure across the two diodes, ground to the anode of the top diode?

Pin 5 is connected to the diodes so you should see the same voltage.

Pin 6 and 7 voltages look OK.

If you mean the this "bias" diodes, I currently have one connected and its reading 8,4v between gnd and the pin7 point.

Note that, when i touch the pin 7 with this, filtering (actually dual filtering) sound starts to decay from a high freq and stops somewhere and once down, its not responsive to input guitar signal.

[Rob Strand]

If you mean the this "bias" diodes, I currently have one connected and its reading 8,4v between gnd and the pin7 point.

Yes across the bias diodes.

If pin 7 is going to 8.4V with a single diode then that means you need at least two diodes.

[Baran Ismen]

If you mean the this "bias" diodes, I currently have one connected and its reading 8,4v between gnd and the pin7 point.

Yes across the bias diodes.

If pin 7 is going to 8.4V with a single diode then that means you need at least two diodes.

I got some other didoes at hand, shall I give a try like germanium etc.

[Rob Strand]

I got some other didoes at hand, shall I give a try like germanium etc.

Germanium is a waste of time.  The simple small silicons are all you need.
All the diodes are doing is creating a voltage drop.

Have you cut the from IC1 pin 5 to ground?

[Baran Ismen]

I got some other didoes at hand, shall I give a try like germanium etc.

Germanium is a waste of time.  The simple small silicons are all you need.
All the diodes are doing is creating a voltage drop.

Have you cut the from IC1 pin 5 to ground?

I've made some more progress btw.

This bias probe you mentioned; I've made it with 2x 1n4001 in series (tried with 4148 as well) and one 220k resistor.

I clamped to PIN 7 of IC1, actually the D1's Anode side according to the layout, and I made some trial & errors and connected of Sens 3 lug to this bias probe as well gave me a working unit right now, but the output volume is low. Decay, Treble and Dist switches are working (switch is not distorted btw on either side), Attack, Sens and Low pots are not working at the moment.

OK disregard the above:

I've lifted up the IC1-5, and connected this bias probe into it and it works like I mentioned above.
Also connected another cable from sens 3 to D1 (namely IC1-7) and auto filter is working. Though, input gain was low, changed 2m2 input res with a 1m and gain is much better now. Yet I doubt everything is working as it should.
Readings now are;

5- 0,9V
6- 1,26V
7- 1,41V

With 4 diodes, its 1,76v - 1,92 - 1,92v's consecutively. Its much more responsive, but there's this a bit annoying decay effect when the signal goes to zero, it doesn't naturally fade away, but cuts somehow.

So, what does this mean? Is it about the IC or a faulty layout? Most of the schematics are sending the IC1-5 to ground 

[duck_arse]

This idea might be a better alternative.  It designs out the problem and allows pin 5 to be biased at VREF.



You maybe need to tune R6.  Smaller R6 values will lower the idle DC voltage at the opamp output.  220k to 390k are most likely values.

Rob - do you want new R6 to Vcc or Vref?





slammer - observe this layout - you need to lift the links at the two circled points, and then join the two free wires together. then pin 5 is free, connected to nothing. use that strip for whatever you like.

maybe this is why that pin 4//5 cut is there.

[Baran Ismen]

Latest news.

With the probe 3 diodes in serial + a 56k resistor behind, the board works quite well now, only the bass pot seems irresponsive (maybe it's about the resistors in front of it, I don't know). I lifted up the pin5 and connected the probe into it directly and voila.

I've also exchanged the 4n7 and 22n caps in-between, and dist. section is much much better and working how it is supposed to be right now, a tight, notched fuzz. It was clipping hard before this cap exchange.

Just for my taste also, I've played around with some transistors I've got in my hand and I've found that 2n2222 (metal cap, I got'em for Big Muff but not used) sounds more natural than 2n5088, as with 5088 it sounds not much "deep" and decay sounds a bit feint. Maybe a bit more powerful for my guitar signal, I'm not sure.

Now, as it's working with the bias probe, what should I do next for a proper finish? Get an LM358 or LM1458 (this one is MC1458P) and mount directly? On paper, there's not any difference and all the layouts I see are grounding this 5th pin, but I don't know which IC they're using, probably LM- series.

[Rob Strand]

I'll have to get back to this tomorrow.

Some quick answers.

5- 0,9V
6- 1,26V
7- 1,41V

With 4 diodes, its 1,76v - 1,92 - 1,92v's consecutively. Its much more responsive, but there's this a bit annoying decay effect when the signal goes to zero, it doesn't naturally fade away, but cuts somehow.

So, what does this mean? Is it about the IC or a faulty layout? Most of the schematics are sending the IC1-5 to ground

There's a few things going on that are all interlinked:
- The first is the *input* needs to be biased in order to stop pin 7 going to a high voltage.
   This might only take one or two diodes but the opamp still might not be quite working correctly.
- The second is the output side DC voltage.
   If you need to add a few diodes to the input side then you might need to add some diodes to the output
   side (in series with D1)  to compensate.  The diode(s) in series with D1 might fix the decay.
- The third is the sound of the distortion output.

For bias four diodes you probably should *also* add two diodes in series with D1.  You might even need three diodes.   You can even experiment to see what works better.   It might help to change the 100k bias diode resistor to 10k, that will increase the voltages a bit.    Once you get start using four diodes it might be more economical to use RED LEDs instead of diodes.

The advantage of the second method I suggested is it might work better.   This method starts with the opamp inputs well within their working range.  You can also play with the R6 resistor value to tune the sound.  Much cleaner than playing with many diodes.  You try one extra diode in series with D1 with this method but you should re-tune the resistor value, a higher resistor value is required.

- do you want new R6 to Vcc or Vref?

It's definitely as shown:
-  pin 5 to Vref to bias the opamp *input* to a working voltage
-  R6 to Vcc to set the output bias voltage.  (Without R6 the opamp would bias at Vref but we want to bias the output round 0V to 2V to mimic the original behaviour of the ckt.)

In theory the second method should use a 220k but given the original circuit is no operating the opamp in a good zone I allowed for some tweaking of R6.    This is where putting the finishing touches comes in.