After many tries of building this wicked circuit i finally got the hang of it.Here is a sound example of the octave down (https://drive.google.com/file/d/1f66TjnkEy2xh_Gjjpu9YfMYmGWxJZUQ4/view?usp=drivesdk)
I gave myself a bigger breadboard to work with and this may have solved the issue.
(https://i.postimg.cc/VSwbMzmB/IMG20250213200804.jpg) (https://postimg.cc/VSwbMzmB)
And here is an unverified veroboard for it if anybody want to build it.
I will try building and see if i can verify it.
(https://i.postimg.cc/4mhKSY3Q/OCTAVEEE.png) (https://postimg.cc/4mhKSY3Q)
Thank you sir mike and antonis and electric druid and many others for all the help you gave me.
If you manage to squeeze layout a bit (e.g. 35-36 columns) it will nicely fit into a 1590BB (or similar) enclosure.. :icon_wink:
Quote from: antonis on February 14, 2025, 04:23:54 AMIf you manage to squeeze layout a bit (e.g. 35-36 columns) it will nicely fit into a 1590BB (or similar) enclosure.. :icon_wink:
Thank you antonis,
I will try to do that!
So i built the layout i made and it worked first time, no problem.
However there is 1 issue with the noise with the octave up.
When the octave + pot is turned all the way down, there is hardly any noise. But when i start to crank the octave + pot there is some kind of noise that's really bothering me. Idk where it is coming from.
I used an audio probe with a sine wave generated at 1khz and followed the IC4 (octave+) path to see if something is wrong. However i didn't find that noise anywhere. Even when i probed at where the octave up middle pin connects, so i can hear only the octave up effect and there was no noise at all.
Here is a Sound clip of the noise. (https://drive.google.com/file/d/1sPBn5CkFFi2jDbnIGga4QK7cDZOLquAW/view?usp=drivesdk)
Also one thing to note is that noise increases when the bright switch is engaged.
Here are some pics of the board.
(https://i.postimg.cc/LnzfqdY2/IMG20250330190006.jpg) (https://postimg.cc/LnzfqdY2)
(https://i.postimg.cc/KKsgXxVr/IMG20250330190047.jpg) (https://postimg.cc/KKsgXxVr)
If there was something wrong, then it would be in the IC4 Section as the noise only appear when i use the oct+.
and here is the schematic:
(https://i.postimg.cc/tsq1YsGN/Schematic-Octarock.png) (https://postimg.cc/tsq1YsGN)
(https://i.postimg.cc/q6cR7TmF/OCTAVEEE.png) (https://postimg.cc/q6cR7TmF)
On the sample, I can only hear the sort of basic background mains hum that I tend to expect. Especially when there's a lot of gain around. Sure, would be nice if there was none, but *it's so common*...I'm not sure I really hear it it these days.
Are you hearing something else? Am I missing something obvious? (It wouldn't be the first time...;) )
Quote from: ElectricDruid on March 30, 2025, 04:02:25 PMOn the sample, I can only hear the sort of basic background mains hum that I tend to expect. Especially when there's a lot of gain around. Sure, would be nice if there was none, but *it's so common*...I'm not sure I really hear it it these days.
Are you hearing something else? Am I missing something obvious? (It wouldn't be the first time...;) )
But it sounds much louder than mains hum, and a little harsher?
I don't know :P
I thought there was something wrong. Maybe when i box it up it will be less. But the thing is, i don't remember it being like that when i tested it on my breadboard.
I took some voltage reading and here they are (they increase when the bright switch is not engaged)
IC4
1: 3.44v
2: 3.6v
3:4.02v
4:7.9v
5:3.58v
6:3.59v
7:3.58v
8:4.43v
9:3.98v
10:3.98v
11:0v
12:3.98v
13:3.98v
14:1.61v
All pots max clockwise/ battery at 8.4v/ bright swich is engaged
Quote from: Lost_soul on March 30, 2025, 04:30:43 PMIC4
12:3.98v
13:3.98v
14:1.61v
Check voltage on OCTAVE+..
Quote from: antonis on March 31, 2025, 03:55:09 AMQuote from: Lost_soul on March 30, 2025, 04:30:43 PMIC4
12:3.98v
13:3.98v
14:1.61v
Check voltage on OCTAVE+..
you mean where octave up pin 3 connects?
Bright switch on
Pot cw 1.31
Pot ccw 1.4
Bright switch off
Pot cw 3.94
pot ccw 3.94
Battery now at 8v :((
Shorted C21 (22nF) ..??
Quote from: antonis on March 31, 2025, 09:26:32 AMShorted C21 (22nF) ..??
I checked it, it's not shorted!
Should i record the trace of the octave up section with the audio probe from start to finish at some specific points that you specify and post it? Because idk if what i am hearing at some points is what should be heard or not.
Like at some points i can hear the volume becomes lower with a bit of motor like noise in the background(zzzz).
please if you can, put some circles on the points you want me to record and i will record them.
Audio probe is useful when DC voltages are all good.. :icon_wink:
For the time being, find a way to make pin 14 sit at about 4V..!!! :icon_mrgreen:
Quote from: Lost_soul on March 30, 2025, 04:30:43 PMBut it sounds much louder than mains hum, and a little harsher?
Like mains hum that's been through some high-gain stages with clipping diodes, maybe? Like IC4, for example.
Antonis is right. Pin 14 isn't happy, and that needs sorting out before that section will work correctly. Check all the components in that area. Something's up somewhere.
Quote from: Lost_soul on March 30, 2025, 04:30:43 PMIC4
1: 3.44v
2: 3.6v
3:4.02v
4:7.9v
5:3.58v
6:3.59v
7:3.58v
8:4.43v
9:3.98v
10:3.98v
11:0v
12:3.98v
13:3.98v
14:1.61
There's something wrong as far back as IC4 pin 1.
With no signal all the opamp pins on IC4 should sit at Vref.
I think your Vref is OK at 4V with your 8V supply.
If you look at IC1 pin 1 it's 3.44V, that is reflected in the pin 5 voltage and pin 7 voltage. But you can see the the pin 8 is 4.43v. It's like the rectifier has a -0.4V signal going into it all the time. And that comes from IC4 pin 1 being off.
The suspicious thing is IC4 pin 1 is approximately one diode drop below Vref. If the 100k feedback resistor (R31) on IC4 pin 1 is not connecting to IC4 pin 1 or IC4 pin 2 then IC4 pin 1 will have a DC shift, exactly what we are seeing. (It's still a bit iffy that IC4 pin 2 does equal Vref, so it' might be something more. (A short on the 220nF cap could do something but not enough IMHO.)
If IC4 pin 1 is off the rectifier won't work correctly and maybe that produces fizzies with a guitar signal.
Well i made the ic4 section again on the breadboard to see the voltages and if the noise is just part of it. It had the same kind of noise hahahah. But it sounds a little more consistent with the octave up.
Might be because pin 14 voltage is above 4v?
Here are the voltages for the breadboard one.
(https://i.postimg.cc/rdKmDgjN/IMG20250404161834.jpg) (https://postimg.cc/rdKmDgjN)
The switch was set to bright.
Why is pin 14 of the veroboard version so low though? i don't know.
Quote from: Lost_soul on Yesterday at 10:27:43 AMWell i made the ic4 section again on the breadboard to see the voltages and if the noise is just part of it. It had the same kind of noise hahahah. But it sounds a little more consistent with the octave up.
It's highly likely the gain in the circuit (from U4.1, and U1.4) is amplifying noise picked-up from the environment.
With breadboards it's often a good idea to get a metal sheet, even kitchen foil, place it under the breadboards then connect it to circuit ground. A lot of people here, including myself, have L-shaped metal enclosure with pots and connectors on the L face. The breadboards are placed on the flat part. It helps with noisy circuits.
QuoteWhy is pin 14 of the veroboard version so low though? i don't know.
A small difference like that is probably normal. U4.4 will amplifly any DC errors by 10.
Quote from: Rob Strand on Yesterday at 04:24:22 PMIt's highly likely the gain in the circuit (from U4.1, and U1.4) is amplifying noise picked-up from the environment.
With breadboards it's often a good idea to get a metal sheet, even kitchen foil, place it under the breadboards then connect it to circuit ground. A lot of people here, including myself, have L-shaped metal enclosure with pots and connectors on the L face. The breadboards are placed on the flat part. It helps with noisy circuits.
Thank you Rob for the great tip.
But what i meant with it having the same noise is that my veroboard layout was fine.
I was just confused as i saw some videos for it on youtube and there was no noise at all.
Quote from: Rob Strand on Yesterday at 04:24:22 PMA small difference like that is probably normal. U4.4 will amplifly any DC errors by 10.
I will measure the voltages again on the stripboard but with the PS at 9.13v and will post it to see if there may be something wrong. But what should i set the switch and the potentiometer at?
I will do this as you said there may be a problem as far as pin 1 in the last message.
Quote from: Lost_soul on Yesterday at 06:40:44 PMI will measure the voltages again on the stripboard but with the PS at 9.13v and will post it to see if there may be something wrong. But what should i set the switch and the potentiometer at?
I will do this as you said there may be a problem as far as pin 1 in the last message.
Well you might try setting the pot so the octave level is about the same as the dry level. When I look at the circuit it seems the octave output is much higher than the dry level. I wouldn't be surprised if you had to set the octave pot to 1 or 2 (on a scale of 10). The gain at IC4.4 might contribute to the tone. If you wanted to balance out levels perhaps add another resistor between the filter and the octave pot (pin 3). If there octave level is very high compared to the Dry level it's just going to sound noisy when you crank the pot. Perhaps when you back-off the pot for equal levels the noise is minimal.
Your new set of DC measurements look pretty good. However, the fact pins 6 and 7 don't match 5 looks like something is still wrong. When you measure pin the meter loading will cause the measured pin 5 voltage to be a little lower. So when you measure pin 6 and 7 you would expect a slightly higher voltage than what you measured on pin 5. In your measurements we see pin 6 and 7 equal, like they are connected, but we see pin 6 and 7 lower than pin 5 by quite a bit.
Quote from: Rob Strand on Yesterday at 07:05:05 PMWell you might try setting the pot so the octave level is about the same as the dry level. When I look at the circuit it seems the octave output is much higher than the dry level. I wouldn't be surprised if you had to set the octave pot to 1 or 2 (on a scale of 10). The gain at IC4.4 might contribute to the tone. If you wanted to balance out levels perhaps add another resistor between the filter and the octave pot (pin 3). If there octave level is very high compared to the Dry level it's just going to sound noisy when you crank the pot. Perhaps when you back-off the pot for equal levels the noise is minimal.
Your new set of DC measurements look pretty good. However, the fact pins 6 and 7 don't match 5 looks like something is still wrong. When you measure pin the meter loading will cause the measured pin 5 voltage to be a little lower. So when you measure pin 6 and 7 you would expect a slightly higher voltage than what you measured on pin 5. In your measurements we see pin 6 and 7 equal, like they are connected, but we see pin 6 and 7 lower than pin 5 by quite a bit.
Yes!!! I also was surprised that when i turn the octave pot from zero to say 1 the gain is instantly high, the noise is also high but definitely not higher than when it's at max but it's still pretty high.
It seems like i can never get this circuit right whatever i tried :((
Where is the filter part you mentioned on the schematic?
Idk what's wrong with pin 6 and 7 voltages. I can't find something wrong on the breadboard.
(https://i.postimg.cc/75y0DSbr/IMG-20250405-014023.jpg) (https://postimg.cc/75y0DSbr)
Can you spot anything?
Ps: i removed the orange jumper that connects pin13 to the resistor at the very down left just for the picture.
Quote from: Lost_soul on Yesterday at 07:52:31 PMWhere is the filter part you mentioned on the schematic?
It's the circuit with the switch and C21.
(https://i.postimg.cc/gxxkyZgK/foxrox-octave-level-reduction-mod.png) (https://postimg.cc/gxxkyZgK)
It's pretty normal to go over a circuit and kick the tires a bit. No matter how much time you spend on it, next week you will think of something else :icon_mrgreen:
Quote from: Lost_soul on Yesterday at 07:52:31 PMCan you spot anything?
There's nothing obvious.
Clearly pins 6 and 7 are connecting, even from the voltages. You can get weird results like that when there's a bad connection (somewhere). If pin 5 is really different to pins 6 and 7 I'd start to be suspicious the opamp has a problem.
Quote from: Rob Strand on Yesterday at 08:28:13 PMIt's the circuit with the switch and C21.
(https://i.postimg.cc/gxxkyZgK/foxrox-octave-level-reduction-mod.png) (https://postimg.cc/gxxkyZgK)
It's pretty normal to go over a circuit and kick the tires a bit. No matter how much time you spend on it, next week you will think of something else :icon_mrgreen:
Clearly pins 6 and 7 are connecting, even from the voltages. You can get weird results like that when there's a bad connection (somewhere). If pin 5 is really different to pins 6 and 7 I'd start to be suspicious the opamp has a problem.
Well you ARE right!!! The opamp really was the problem. I changed it and bam the voltages now across pins 5,6,7 are the same 4.8v. Thank you rob. Now as I understand the voltages are all right. I wish I could figure out how to read voltages and know what they should be at any point in a schematic but idk where to start.
I will try your mod in the morning and report back as it's 3 am here.
Thank you again man.
Quote from: Lost_soul on Yesterday at 09:08:00 PMWell you ARE right!!! The opamp really was the problem. I changed it and bam the voltages now across pins 5,6,7 are the same 4.8v. Thank you rob. Now as I understand the voltages are all right. I wish I could figure out how to read voltages and know what they should be at any point in a schematic but idk where to start.
I will try your mod in the morning and report back as it's 3 am here.
Thank you again man.
Cool you are pretty much there now.
For a lot of circuits the input and outputs of the opamps should all sit at about Vref (Vcc/2 or whatever). There are a few instances where the multimeter loads down the voltages and you get less than Vref but you can have an idea that's going to happen if you see a 470k or 1M resistor there. Things like oscillators/LFO are different.
I'm confused. I'm not sure I'm looking at the right, or current, thing. here, see what I see, pins 6 and 7 shorted, and the diodes not connected as per circuit dia, and 100k resistors, perhaps instead of 10k resistors.
as I say, I'm confused now, and daylight savings ends in an hour, so it's only going to get worse.
oct.rocks.jpg
Quote from: duck_arse on Today at 10:01:05 AMI'm confused. I'm not sure I'm looking at the right, or current, thing. here, see what I see, pins 6 and 7 shorted, and the diodes not connected as per circuit dia, and 100k resistors, perhaps instead of 10k resistors.
as I say, I'm confused now, and daylight savings ends in an hour, so it's only going to get worse.
oct.rocks.jpg
I am not sure what you mean. Isn't pin 6 and 7 connected together in the schematic? And there is a diode from pin 7 to a point and then another diode from pin 8 to the same point?
Quote from: Lost_soul on March 30, 2025, 01:55:18 PMand here is the schematic:
(https://i.postimg.cc/tsq1YsGN/Schematic-Octarock.png) (https://postimg.cc/tsq1YsGN)
(https://i.postimg.cc/q6cR7TmF/OCTAVEEE.png) (https://postimg.cc/q6cR7TmF)
when I look on this schem, which is the only one I can see in thread, I don't see a match. am I looking in the right place?
Quote from: duck_arse on Today at 10:16:40 AMwhen I look on this schem, which is the only one I can see in thread, I don't see a match. am I looking in the right place?
yes it's the right scheme. but could you elaborate what is the match you don't see? is it in the pin 6/7 and diode section or is it with the veroboard layout or what
we are discussing IC4 section. maybe you looked at another IC?
Quote from: duck_arse on Today at 10:16:40 AMwhen I look on this schem, which is the only one I can see in thread, I don't see a match. am I looking in the right place?
That image is all whitespace and dim details. Here's where I see 6 and 7 connected.
(https://i.postimg.cc/F1c9fPTN/White-Space.jpg) (https://postimg.cc/F1c9fPTN)