Ok, so I've built Bean's MXR117 SAD 1024 version. It's up and running and sounds great except for the noise. While I can live with a little noise there is just too much to make this pedal usable. I'm out of my element on how to reduce it to where it's tolerable. I've tried it on a One Spot as well as my Voodoo Lab's PS and it is the exact same. It is not in a chain of pedals.
Noise wise, you hear the clock but if that was all I heard it is low enough to where I could get by and not sweat it too much. But the classic swooshing thing is just too much.
Any thoughts on how I might attack this problem would be helpful. I realize the SAD has more inherent noise however no way do I believe that all the old SAD chips were this noisy by 'design'. Now, this SAD chip could be in and of itself 'bad' but before I decide that I'd like to try a few things to bring it down some.
I have pics below to see if anyone spots anything out of whack. All the pots work however the one that jacks this pedal up is if I take the Regen past 75% there is an immediate squeal and I don't mean the kind that you go huh and it goes up when you keep turning. I mean the kind that will make you come out of your skin immediately.
Also of note the trimmer nearest the top and nearest the SAD chip is very scratchy while turning.
Thoughts from anyone?
(https://live.staticflickr.com/65535/48579752116_94083cb7b1_c.jpg) (https://flic.kr/p/2h1PVP3)
(https://live.staticflickr.com/65535/48579752081_1f4bd13cbd_c.jpg) (https://flic.kr/p/2h1PVNr)
(https://live.staticflickr.com/65535/48579751906_3728b9eeb8_c.jpg) (https://flic.kr/p/2h1PVKq)
Well it's been 8 years since I built it so I cannot remember a damn thing about it other than mine was pretty noisy too. But, I don't remember it being too much so or not. Looking at the schematic again the two caps to embiggen would be C7 (150pF stock) and C17 (10n stock). Maybe 1n and 47n resp would tame it without totally killing the top end. Or, socket and experiment.
It could be the layout itself, too. Cramming that circuit into a single sided 125B was more of a d**k measuring contest for me rather than actually being practical. And, when it comes to d**k measuring contests I come up short ADEQUATE.
Well if you don't mind me saying that I thought you measured up quite well when creating this PCB ;D Yeah, if I could tame it just a bit I could use it.
Thanks for a few tips Bean. I'll socket those this week and see what I think.
I built two of these previously. Had noise issues with both. The only way I got around it was to either feed it regulated 18V or, on another build, I incorporated the same transformer that was in the originals.
And... shielded wiring. Input to PCB and PCB to output.
Good Luck ;D
Quote from: Govmnt_Lacky on August 20, 2019, 09:42:40 AM
I built two of these previously. Had noise issues with both. The only way I got around it was to either feed it regulated 18V or, on another build, I incorporated the same transformer that was in the originals.
And... shielded wiring. Input to PCB and PCB to output.
Good Luck ;D
Thanks Gov. I thought about shielded wiring but didn't know if it would do anything. I guess every little thing might lower it.
Of note:
Do you have an oscope to verify that the clock is the proper freq's? It may help as well. Here are the proper numbers to look for:
- Set MANUAL and WIDTH pots fully CCW
Measure SAD pins 3/14 or 8/10 for 29-32KHz. Adjust the 500K pot as necessary. (the timing cap value might need to be adjusted)
Also, make sure your REGEN is properly trimmed:
- Set REGEN pot to full CW
Adjust 20K Regen trim until Feedback 'just' starts to oscilate. then, turn trimmer back until the oscillation just stops. (at full CW on REGEN pot you should NOT hear oscillation)
No, I don't have a scope unfortunately. Always meant to get one. Never did like with many things.
Quote from: TNblueshawk on August 20, 2019, 11:37:10 AM
No, I don't have a scope unfortunately. Always meant to get one. Never did like with many things.
What about a multimeter with frequency measurement?
Quote from: Govmnt_Lacky on August 20, 2019, 11:46:31 AM
Quote from: TNblueshawk on August 20, 2019, 11:37:10 AM
No, I don't have a scope unfortunately. Always meant to get one. Never did like with many things.
What about a multimeter with frequency measurement?
Well I have to admit that I've never noticed if I do. I'll check it out tonight. I want to say no on my one meter but maybe.
Another item to note:
After looking over the MBP 117 project doc, I wonder if the SPEED pot is actually supposed to be a C500K pot instead of an A500K ???
Brian???
EDIT: After looking at the Collosalus doc... it should be C500K. Is that what was used in this build?
EDIT2: What voltage are you running at? I do not see a 15VDC regulator on your Road Rage board. Are you just feeding the charge pump output voltage directly into the 117??
Well, for sure all the speed pots are C rather than A on the builds I've built but i don't recall if I caught that when I built it. I built this several months ago but got into a kitchen project and didn't get back to this one for a bit. I'm at work so I'll have to look at the build.
My multimeter doesn't have Freq measurements. This is the model https://www.circuitspecialists.com/digital-multimeter-csi2010.html
So, in my docs it calls it a Sweep pot and not Speed. But if you look in the original manual for this pedal on line it is called a Speed pot. So, I'm thinking maybe it should be C500k. I used an A500k. I'm not sure that solves anything noise related but interesting nonetheless.
Speed should be C500k, that's nearly always the case unless the pot is being used as a voltage divider but that will only help with the action of the speed pot.
Your wiring could do with being a bit neater, wont help with hiss but it will with any stray sweeping noise. Or just shield it as already discussed.
But mainly, as Lacky pointed out, where's your regulator? An unfiltered/unregulated charge pump running in to a flanger is going to be noisy, the circuit doesn't have any kind of power filtering on the audio. It would probably be worth running a 2W 10R after the regulator to the board as well to create a filter.
It should be a reasonably quiet flanger, S/N is good and there's a decent amount of audio filtering.
Quote from: Scruffie on August 22, 2019, 06:59:49 AM
Speed should be C500k, that's nearly always the case unless the pot is being used as a voltage divider but that will only help with the action of the speed pot.
Your wiring could do with being a bit neater, wont help with hiss but it will with any stray sweeping noise. Or just shield it as already discussed.
But mainly, as Lacky pointed out, where's your regulator? An unfiltered/unregulated charge pump running in to a flanger is going to be noisy, the circuit doesn't have any kind of power filtering on the audio. It would probably be worth running a 2W 10R after the regulator to the board as well to create a filter.
It should be a reasonably quiet flanger, S/N is good and there's a decent amount of audio filtering.
Hey Scruff, I'm using an LT1054 if I recall right on the Road Rage with a regulated 9v PS off a Voodoo Labs PS for either 15v or 18v operation. I forget what I decided to try to run it on off hand. I do plan to shield. My wiring looks worse since I've been taking it out and playing with it but I'll route things better when I shut the box up for good.
I am a little confused though with respect to the Speed pot. In the BOM for this project there is not a Speed pot. There is a Sweep along with the Manual, Regen and Width. But, I'm guessing the Sweep should maybe be a C500k?
Are you saying I should regulate more with the 2w10r in some way?
You need a 7815 or 78L15 regulator after the charge pump, whatever you're powering it with, put that in and see how you get on before doing anything else.
Sweep is Speed so yes it should be C500k.
Quote from: Scruffie on August 22, 2019, 09:12:16 AM
You need a 7815 or 78L15 regulator after the charge pump, whatever you're powering it with, put that in and see how you get on before doing anything else.
Sweep is Speed so yes it should be C500k.
To add to Scruffie's post... and to clear up any possible confusion...
You need to install a LM7815 onto your Road Rage PCB. The pictures you provided do not show one being installed. So, you are NOT getting 15VDC regulated from that board. You need to install one of these:
(https://i.ebayimg.com/images/g/AEIAAOxyE-dRzJq1/s-l500.jpg)
It finally hit me after Scruff's second post. The word "Doh" came to mind with a forehead slap. I plan to do all these things on my long weekend. I'm off work tomorrow.
Thanks to both of you and I'll report back.
So as it turns out, I should never rely on memory at work, I was running it at 18v and that is the reason I didn't put in a regulator. I'm using an old Road Rage board which corresponds with Bean's 2012 build doc.
So I figured let me rewire for 15, add a regulator and see what happens. Well. when I did that all I got was this huge hum and the pedal pretty much didn't work any longer or I could just barely make out an audible swoosh but he hum is so loud, even with guitar volume off, I have to shut the pedal off or something like my speaker might blow! So because of this hum and my lack of time this weekend apparently I didn't bother with shielding the wire yet. I did put in a C500k Speed pot though.
So, I ran out of time to fiddle around. How about if I punt and start from scratch here and I'll work up a new RR board to power this thing.
If you were me would you run this thing at 18v no reg per the RR BOM or 15 with reg? Also, the correct orientation of the 7815 was where the metal backing would lay flat on the RR board (I made sure it didn't so as not to touch the SAG control eyelets), correct?
Out of curiosity, would running it at 9v be such a bad idea I wonder?
The original MXR Flanger ran at 15VDC (regulated internally)
According to the datasheet for the SAD, the MAX operating voltage is 20VDC however, the MAX clock voltage is 17VDC :-\ Now, I do not know if that means 17V for EACH clock input or 17V to be split in half for each individual clock input or 8.5VDC
Either way, I would recommend that you go for the 15VDC option to stay true to the original design.
Quote from: Govmnt_Lacky on August 26, 2019, 11:26:30 AM
The original MXR Flanger ran at 15VDC (regulated internally)
According to the datasheet for the SAD, the MAX operating voltage is 20VDC however, the MAX clock voltage is 17VDC :-\ Now, I do not know if that means 17V for EACH clock input or 17V to be split in half for each individual clock input or 8.5VDC
Either way, I would recommend that you go for the 15VDC option to stay true to the original design.
So with the RR board I just want a second opinion on this. When installing the regulator I want to make sure I have the right pinout. I read the data sheet on the 7815 but I'm not settled on where pin 1 is on the RR board. My reading of it is that when installing the metal back of the 7815 would lay flat (again I won't flatten it) on the RR board, correct? As opposed to the plastic 'box' laying flat on the board.
Quote from: TNblueshawk on August 26, 2019, 12:07:23 PM
So with the RR board I just want a second opinion on this. When installing the regulator I want to make sure I have the right pinout. I read the data sheet on the 7815 but I'm not settled on where pin 1 is on the RR board. My reading of it is that when installing the metal back of the 7815 would lay flat (again I won't flatten it) on the RR board, correct? As opposed to the plastic 'box' laying flat on the board.
If you have a multimeter, just make sure the 15V out on the RR board is connected to Pin 3 of the 7815 regulator (Vout)
EDIT: From what it looks like in the build doc, you can add the regulator tab down on the component side of the PCB (I would add a buffer material so the tab does not touch any exposed pads) and you will also have to install C6 (10uF)
Just to update the thread I replaced the Road Rage board and the pedal worked with minimal or I guess normal noise. While I can't pinpoint why in looking at the old RR board as it looks good apparently there was an issue on that board. But in a comical moment, one has to laugh at times, I had 2 of the SAD chips so I wanted to test the second one. I pulled the chip out and noticed that pin 16 of the socket pulled up. Never had that happen before. I pushed it back down wondering if the socket was buggered up. I put the chip back it and of course nothing works. Dead quiet when I kick the pedal on. I said one has to laugh right?
So I guess I'll desolder a 16 pin socket. This should be fun. Hope I don't jack up the board doing this. I suppose I could attempt to solder in the pin that is not connecting but then all kinds of bad crap could happen. I could solder it in with of course chip in there and it still doesn't work. I could burn out the chip maybe, dunno.
Who says this hobby isn't fun :o
Well it was going so well desoldering the socket for the SAD then pin 16 I lifted the trace. Or, that was the issue the whole time as that was the pin in the socket that got all floppy jawed on me. So, per the data sheet it calls this pin NC and says it should be connected to ground.
If you guys were me and you wanted to make this work as opposed to tossing the board what might you rig for this lifted trace?
(https://live.staticflickr.com/65535/48659574563_9b0b30e218_c.jpg) (https://flic.kr/p/2h8T3f8)
Quote from: TNblueshawk on September 01, 2019, 09:41:31 AM
So, per the data sheet it calls this pin NC and says it should be connected to ground.
Well, if you want to get literal... there are several pins on that board that are NC and should be connected to ground according to the datasheet. Best advice would be to look at the schematic for the original and see what they did with those pins. From what I can see of original PCB pics from the MXR, it looks like they did tie NC pins to GND.
In the body of the data sheet it says the NC's should go to ground. I'm just trying to figure out how I could rig something to where the IC works and Ive tied that pin to ground. I was thinking I could solder a wire in on pin 16 with the socket and the IC but then that IC will have to stay there given I'm soldering it in. The down side, assuming that would even work, is I can't test the other chip. Of course I do have a second board as Haberdasher etched me two but I hate to ditch this board if somone has a more ingenious way of saving it.
Question. I assume I can ground that anywhere or do I have to tie it into the board?
If it were me...
I would use my Dremel to drill a hole into the large ground plane closest to Pin 16 and another hole right next to Pin 16. Install a jumper on the component side of the board. Solder one side of the jumper into the ground plane. Solder the other side of the jumper directly to Pin 16.
You are still leaving Pins 4, 13, and 16 as NC though... :-\