Hello. ;)
I'm working on this circuit: http://www.sabrotone.com/?p=99
All pots work fine, but there is too hum, like a distortion pedal.
It is based on this: http://www.generalguitargadgets.com/effects-projects/eq/6-band-graphic-eq/
In my first test I forgot the two ICs and I missed R5 :icon_redface:
All componets seem ok.
Where's the problem?
Thanks guys! ;)
Hi EB
Is the issue that when you raise the gain of you favourite freqauncies it clips the op amp?
If so maybe try reducing the unwanted ones and reduce the ones you want too so as not t clip the op amp.
Maybe stick the o scope on it. It might give you some clues.
I've never got this to work but I'm glad you have. Maybe I'll try it again soon.
Thanks Kipper4.
It works fine, I mean all the pots are very useful. It is like a Bass/Middle/Treble but with two more pots, and it doesn't make the thing difficult.
The only issue is this noise always on. :( I can't use it in front of my amp using the distortion channels.
The gain pot controls the volume, and I get just a bit of clipping at very high setting of this gain pot, but setted like that the pedal becomes a volume boost, anyway the clipping is just a bit and it doesn't a real problem. And then I tested it with humbucker pickup.
I guees it is not a clipping problem, because it sounds clean.
Seems to me it is not even a problem of some frequency pot, because the hum change frequency following the tone of the equalization, but it never encreases nor decreases.
The volume of the hum is joined to the overall volume. I can hear more hum just beacuse I have more volume (gain pot of the eq or volume of my amp).
It is very tricky, and unfortunately it is not very built. But I really don't want to abandon this pedal.
You might get more headroom out of it using the dual supply.
Or a charge pump +9v -9v maybe a icl7660.
Also is your power supply regulated? If the power supply is not regulated it may introduce some additional noise.
Sounds like your using it as a kind of booster......so if you use it just as a eq with unity gain is it better?
You'd be surprised what a well tuned 2 band active can do.
If you look at the eq in the boss fa1 ,breadboard it and tweek to your ears and gear, you might like it.
If your happy with the 6 band. Go for it.
Happy playing EB.
I'm testing the circuit with a battery.
My intention is to use it like an eq.
I'm using it at unity gain, but it's definetely noiser than bypass.
I don't know what kind of problem could be.
I have built similar circuit powered with ±15V, and it works fine, no distortion at all. But I swapped + and - inputs on gyrator op amps when designing PCB, so controls behave strange. I will order new PCB with corrected inputs and I will report my experiences with that board. However, I put JFET preamp in front of this and it is working fine, and there is some (but not much) noise when EQ pots are not in the middle; when in the middle, no noise at all. Maybe using another op amp will eliminate that noise? I use TL074, but I will try with something else, too.
I thought it can works at 9v without any issue. I'm using two TL074, I guess it should be low noise.
Anyway, I want to be more clear. I got no distorion at all, the sound is clean, but the noise I get is: do you know the noise of a gain channel?
I found a casual video. Just listen few seconds at the beginning before the guy start to play.
www.youtube.com/watch?v=iIFqlSowsSQ
That hum come from the high gain channel, and that is the kind of noise I get. Indeed, if I active the gain channel of my amp the noise is intolerant. In the clean channel it's really disappointing thought it isn't so loud, but I can hear if I play softly or hardly.
Is it boxed up yet? If you've got a veroboard floating about in a room with mains power wiring running about to your amp and so forth, I wouldn't be surprised if it picked up some hum/noise.
Actual mains hum could be down to it not being shielded, or it could come from the power supply, but you said you are using a battery, so that rules the second possibility out.
Any circuit with highly selective gain stages like an EQ is going to have a tendency to be noisy. If you put five of them together, it's going to get noisier. If you'd got an error in one of the gyrator stages which boosted the Q of that stage, that might make it worse.
Beyond that, I'm not a massive fan of that low impedance inverting gain stage on the front end of the circuit.
http://www.generalguitargadgets.com/pdf/ggg_eq6bg_sc.pdf (http://www.generalguitargadgets.com/pdf/ggg_eq6bg_sc.pdf)
They've gone with an inverting gain stage because the output mixer is inverting (I'd guess) so that gives the pedal no inversion overall. But that means the gain stage design is a big compromise.
Tom
It isn't boxed yet, indeed. And I thought that was my lost possibility to solve, but I use to drill the boxs only when I'm sure enough that the circuit works right. I didn't know that an eq could be so noisy or pick up noise. Usually my distortion pedal circuit was really quite. (Big Muff, Rat, BSIAB II, Fuzz Face Si...)
I don't know if there is some error in the gyrator stages you mentioned, because I don't know what exactly it is. Seems to me there's no mistakes with resistor or caps.
Could be a voltage measurement of the ICs useful? Unfortunately, those can't tell me anything, perhaps one of you guys can help me.
About the inverting gain stage, I post here the veroboard layout, because it is a little bit modified.
(http://www.sabrotone.com/wp-content/uploads/2010/05/5-band-EQ-w.-Gain.gif)
Thanks.
I'm gonna try and explain the gyrator as best I can. Not my forte.
First off the gyrator is a replacement for an inductor. How am I doing?
There are 6 gyrators one for each EQ stage.
Ggg schematic
Ic1A
Ca1
Cb2
R6
R7
Is a gyrator
I hope that helps.
I don't know if this is the problem, but I see 3 things:
1) Vref is connected directly to the +input of the first IC amplifier (A1+in, pin3), while Vref is applied through a 220K resistor for each of the tone shaping ICs. It might be quieter if Vref also goes through a high value resistor to A1+in. As is, potential thermal noise? Confusion arises from the GGG schemo showing that input going to ground, not Vref, but he gives options for both 9V and 18V power options.
2) R6 is connected to Vref (4.5V) rather than case ground. For a 9V system, it should go to case ground (0V) (GGG R25)
3) C1 is connected to Vref, not 0V (GGG C9)
Using the Sabro layout you posted and referencing the GGG schematic,
#1 above could be done by the following:
-Cut at 5f
-Move R5 between 2a & 2c
-Move R2 between 4c & 4e (flip it)
-Extend jumper from 3h to 3c, no connection at 3f
-Shorten jumper from 7f to 7i, no connection at 7b
-New 220K between 7b & 7e
-New jumper 6e to 6f
#2 could be changed by:
-move R7 to 11a & 11c
-remove the jumper between 3i & 3n
-move top of jumper (starting at 8j) from 8a to 9a
-new jumper between 7n to 8a
#3 could be changed by:
-move C1 so it is now 3k & 3n
edits for clarity and additional mods
Double post
I've built this, don't remember mine having any hum, been a while since I've used it though.
Kaycee, did you build the veroboard layout?
Quote from: Kipper4 on March 04, 2017, 09:21:32 AM
[...]
There are 6 gyrators one for each EQ stage.
Ggg schematic
Ic1A
Ca1
Cb2
R6
R7
Is a gyrator
[...]
Thanks for helping. But caps and resistor seem ok. I'll check anyway, again.
Quote from: Cozybuilder on March 04, 2017, 09:50:41 AM
I don't know if this is the problem, but I see 2 things:
1) Vref is connected directly to the +input of the first IC amplifier (A1+in, pin3), while Vref is applied through a 220K resistor for each of the tone shaping ICs. It might be quieter if Vref also goes through a high value resistor to A1+in. As is, potential thermal noise?
2) R6 is connected to Vref (4.5V) rather than case ground. For a 9V system, it should go to case ground (0V)
Using the Sabro layout you posted, #1 above could be done by the following:
Step 1:
Cuts at 5e and 5f
Move R5 between 2a & 2c
Extend jumper from 3h to 3c
Step 2:
Shorten jumper from 7f to 7i
New 220K between 7b & 7e
New jumper 6e to 6f
#2 could be changed by:
1) move R7 to 11a & 11c
2) remove the jumper between 3i & 3n
3) move top of jumper from 8a to 9a
4) new jumper between 7n to 8a
Thanks. Before to make this mods I wanna be sure there's no my mistake. The layout should be verified.
Yes, vero from the Sabro layout, lots of pots to wire up!
Cozybuilder's points about the grounding are all very good. If the grounding is wrong, it'll be noisy.
Those GGG designs with various power supply options always confuse the hell out of everyone. Does anyone really use two 9V batteries to get a bipolar supply in a pedal? Isn't that just expensive?! Designing for a single 9-18V supply would be much better, I reckon.
Tom
Talking about the Sabrotone version, how we could explain this?
Quote from: kaycee on March 04, 2017, 11:01:31 AM
I've built this (Sabro version), don't remember mine having any hum, been a while since I've used it though.
Thanks Kaycee! ;)
Maybe I really can eliminate the hum boxing it up. ???
Looks like I made a 3 band version :icon_redface:
(http://i.imgur.com/1fJErAVm.jpg)
Been a while since I had it out, I knew it had a lot of knobs, but not enough apparently :icon_lol:
Is very quiet though, just a 9 volt supply
Thanks. ;)
I preferred the 5 pots + gain pot version.
I just drilled the box for the Bit Commander http://www.diystompboxes.com/smfforum/index.php?topic=117042.msg1085787#msg1085787
And it has 6 drill pots. I wanna try to solder the jack input and output, fit the 6 post, and probably to solder the DC jack, too. No footswitch nor LED, and close the box.
I wanna see if it can mute the hum.
Just a quickly question: what about the capacitars 10uF? Could be someone which it could give this noise? I can exclude C13 and C14 already replaced.
Doesn't matter. I've got a problem here. After a while the I got a distortion/clipping sound. I had fixed it early replacing C13, but it comes back now.
This is the voltage, the battery is a bit low: 8.45v.
IC1
1 4.85
2 3.96
3 3.95
4 7.94
5 5.84
6 5.89
7 5.89
8 3.95
9 3.95
10 3.22
11 0.00
12 3.21
13 3.94
14 3.94
IC2
1 3.94
2 3.94
3 3.21
4 7.85
5 3.91
6 3.20
7 3.90
81.51
9 0.95
10 0.94
11 0.00
12 3.16
13 3.20
14 3.85
Ic2 pins 8,9,10 do those look right ? Without looking at the schematic I can't tell for sure.
I link again scheamatic and even the layout, because it could be slightly different.
Quote from: ElectricDruid on March 04, 2017, 05:36:04 AM
[...]
http://www.generalguitargadgets.com/pdf/ggg_eq6bg_sc.pdf (http://www.generalguitargadgets.com/pdf/ggg_eq6bg_sc.pdf)
[...]
Quote from: Elijah-Baley on March 04, 2017, 07:15:29 AM
[...]
(http://www.sabrotone.com/wp-content/uploads/2010/05/5-band-EQ-w.-Gain.gif)
[...]
Anyway, the circuit doesn't work as first, when it worked fine but with noise. Now, the sound is a bit dull, the frequency pot works, but the gain pot doesn't work properly, it doens't control the volume, just the tone change a bit.
I'm gonna replace the other 10uF caps one by one because those was taken off by a failed and noisy Little Angel abandoned time ago. Honestly, I don't trust in it so much. ::) We'll see.
> gain pot doesn't work properly
It has a cap which should NOT be in there. Same error on schematic and on Vero drawing (though different part numbers?). The fix for an already-build board is to short the cap. (If the cap were not in yet, you would insert a jumper and save the cap for another project.)
(https://s3.postimg.org/ce9ht3e6b/GGG_EQ_fix.gif)
There's somthing really weird here, because I replaced other caps 10uF, resolder some point on the board, and switched between them the IC, just to see. I tested the circuit and for a while it worked fine, a lot of volume (and a bit of white noise, the first problem), and the gain pot worked well. While I was turning the other pots the gain pot work bad again. It is like a compressor, I have slightly more volume at low setting, at high setting the sound is compressed and a bit distorted. ???
About the schematic... I can try to take off that cap and put a jumper, but it should be verified.
Quote from: Elijah-Baley on March 13, 2017, 04:33:07 AM
About the schematic... I can try to take off that cap and put a jumper, but it should be verified.
C13 is definitely in a wrong place - it is not needed at all.
What about the orientation of C14? Look at the layout, look at the schematic.
On the Sabrotone layout, and on the its page, it seems has been corrected, but... ??? I'm not sure.
The orientation of C14 looks fine.
Where you thinking it is anode + to Gnd?
If you look there's a cut at A7 which isolates it from the Gnd.
Thanks for the image, PRR. ;)
I could wrong, but look this:
Quote from: PRR on March 12, 2017, 05:19:27 PM
[...]
(https://s3.postimg.org/ce9ht3e6b/GGG_EQ_fix.gif)
Schematic: Input goes in the
positive of C7 (C14 for Sabrotone).
Layout: Input goes in the
negative of C14.
Here the discussion, even about the orientation of C14: http://www.sabrotone.com/?p=99
They said: "
negative side of C14 goes to input", just like the layout, then it should be work, even if I can't explain it.
> Input goes in the positive of C7 (C14 for Sabrotone). ... Input goes in the negative of C14.
This is don't-care. Actually C7-C14 should be non-polar. There is zero DC volts across it. However polar electros work very well this way. EITHER way.
MY problem is that C8-C13 should NOT be there at all.
And one possible symptom is that things work erratically. (IC1? does not know what DC to be at, and can get stuck.)
I soldered socket pin for C13 and C14. Used a 1uF film cap for C14 and a jumper for C13. But it still doesn't work. Tried also a 1uF for C13, no changing. Gain pot works like a sort of compression pot, encreasing it I lose a bit of volume.
IC1 stuck? What I have to do? :(
Quote from: PRR on March 14, 2017, 09:49:01 PM
MY problem is that C8-C13 should NOT be there at all.
Yes, I tried even to jumper it, but there's no difference. I still have the same issue with the gain pot, low volume and a bit of clipping. :(
I tested the circuit again, immediately with a jumper instead the C13 cap. C14 like in the schematic. It worked. :)
I don't know why today it's working. Is it because of this? ???
Quote from: PRR on March 14, 2017, 09:49:01 PM
[...]
(IC1? does not know what DC to be at, and can get stuck.)
I got, anyway, just that bit of white noise, like at the first test. I have to try to put it in the drilled box.
I probed the signal. I get the slight hum in the first part of the circuit. After the first gain stage and before the gain pot. :(
http://www.generalguitargadgets.com/pdf/ggg_eq6bg_sc.pdf
Quote from: ElectricDruid on March 04, 2017, 05:36:04 AM
[...]
Any circuit with highly selective gain stages like an EQ is going to have a tendency to be noisy.
[...]
I'm trying the circuit in front of the amp, is it because of this it is so noisy in the distortion channel?
What is the typical position of the eq in a pedal chain?
Quote from: Kipper4 on March 03, 2017, 07:08:21 AM
You might get more headroom out of it using the dual supply.
Or a charge pump +9v -9v maybe a icl7660.
[...]
I can decrease the hum with a charge pump?
What of these two?
(http://www.sabrotone.com/wp-content/uploads/2011/01/Charge-pump.gif) (http://2.bp.blogspot.com/-yYGKBiFIRr8/Typ6JJ_JHoI/AAAAAAAAAhU/FSsSt8acW58/s1600/Charge+Pump.png)
If you build voltage doubler, it is much better to use LT1054 than 1044 or 7660. If you have to use 7660, make sure you use 7660S and not 7660A, because S can be used with frequency boost.
Thanks! ;)
I know what the voltage doubler does, but I don't know what the +9v/-9v does.
And what about my eq?
Quote from: Elijah-Baley on March 27, 2017, 12:56:51 PM
I know what the voltage doubler does, but I don't know what the +9v/-9v does.
And what about my eq?
Voltage inverter is something you need for this EQ if you want to run it on ±9V, and you have only +9V supply. So you build this inverter and it produces -9V, then connect that -9V to point B on EQ schematic (http://www.generalguitargadgets.com/pdf/ggg_eq6b_sc.pdf), connect +9V to point A and ground to point C. You will have double headroom, but I don't think it will reduce the noise you have.
I have also built similar EQ (4 band) and it has some noise, but not much. If all EQ pots are in the middle, there should be no noise at all!
I should to find the point A, B, C on the sabrotone layout, but if you think it is nothing to do with the noise... :(
I am almost sure the boards is ok and the eq is right so. >:(
Probably it has to be used after the distortion.
Do you have noise when all EQ pots are in the middle?
I'll do another test, but I have the same noise at any setting. Maybe change just the tone of the hum.
Have you tried to power it from the battery? Maybe your power supply is noisy?
Yes, I test the circuits with the battery, then with the PSU. No differences. :(
I started to think to abandon this circuit because I think it's all ok but it is just a bit noisy. I can build this: http://diy.thcustom.com/shop/5-band-eq-pcb/
It is based on the BA3812L chip. I hope this is quiter, I would an eq absolutely noiseless. :-\
Can anyone confirm that removing C8 from ggg schematic resolves the low volume issue? As others have mentioned engaging the pedal reduces the volume dramatically even with gain all the way up. However, if I crank the amp volume I can hear that the eq adjustments are working. Thanks and Happy New Year!