BOSS CE1 PROJECT: MN3002 or TDA1022P: DOC UPLOADED

[Govmnt_Lacky]

See attached video

That sounds like straight up power supply hum to me (and really, really bad at that)

What are you using as a "12V adapter?"

[Ricotjuh]

I have now tested it with this adapter. Obviously not the best power supply. But I think I had the same problem with my other adapter, but this one is now at work. I am taking this home home this morning and, to be sure, I will test it again.

But you are almost certain that it must be a power supply problem?

[Scruffie]

That is an odd one, I'm wondering if it's intereference from something else in the room, I wouldn't call that power supply hum and nor does it sound like a short.

[RDL68]

I had a similar hum issue when I did my one of these a year back. As I described in earlier posts in this thread back at that time, this circuit is very fussy with its PSU & it must be an isolated PSU. You can't just plug in any power adapter & you definitely can't daisy chain these. Also, a 9v battery lacks the required current to run it, but perhaps 2 wired up together would work to avoid the hum, even as a temporary solution to rule out other causes, but I'm pretty sure it's the lack of an isolated PSU because I went through this myself.

Hopefully someone more knowledgeable can come up with a small power supply circuit to avoid this problem, so any old PSU can be used. From memory, I don't think the small power supply PCB's (with the charge pump) Brian was selling worked for this circuit. I remember Brian was going to have a look into doing this circuit for the store, if so, sorting out a better power section would be recommended before churning out a batch of PCB's. Otherwise, it has to be a power adapter into an isolated power provider unit, then from there to this circuit.

[Scruffie]

Ohhh, yeah, it's using one of those DC/DC converter bricks, I haven't experimented with them much. Perhaps the datasheet offers some clues as to layout tips and noise reduction.

Reading back through the thread, as I said before, converting it to run on just +15V & TDA1022 would be the smartest option, more than enough headroom for a guitar and that should solve the power supply issues.

[RDL68]

Here's a link to the recom 1215D datasheet (power module), albeit not much info there :

https://www.mouser.com/datasheet/2/468/RD-958126.pdf

I also attached a schematic of the power section used in this ce1 clone circuit.
Maybe it's possible someone could re-do the support parts around it to get rid of that hum without having to resort to using an additional isolated power supply unit.
I don't know how, so if it is possible, it could need anything from a couple of extra 1n5817 diodes, a film cap or 2, maybe even a drop down resistor. The answer or solution could be quite simple for someone in the know.

All switching/switch mode power adapters are the enemy of this circuit, instant hum, but they can be used to power an isolated power supply unit, which in turn can power this circuit.

[Ricotjuh]

I just did a test with a 12V power supply with transformer and a switched power supply from Omron. But both power supplies give the same phenomenon.
You are talking about an isolated power supply, but I think every adapter with transformer is isolated. Isn't this always through the transformer?! In my opinion, the term "isolated outputs" only occurs in power supplies that have multiple outputs where the GND's are not connected to each other. But I don't think this applies to a single output. Correct me if I'm wrong.

[Ricotjuh]

I can once again look for a 12V accu battery. Perhaps then I can exclude whether it is the power supply.

[Scruffie]

It's quite possible it's inherent to your layout, that datasheet has shed absolutely no light on the situation but I'm suspecting it is the problem.

Assuming as I said, it's not something in the room interfering and that boxing it wont clean it up.

[Ricotjuh]

The layout has been copied 1 on 1 from the design of drog_trog.
So I would expect others to have this phenomenon too.

[RDL68]

I have a large box full of power adapters. Tried all I could. Also resorted to buying a few new ones specifically sold by music stores under the guise of "for pedals, no noise etc".
No luck with any of them. Always that same full-on hum when engaged. It seems all power adapters available are switch mode regardless of the blurb on the box, at least what I have are. Some say they're switch mode, some don't, which doesn't help. Only solution was a separate isolated power unit, which ironically is powered by a switching power adapter.

So basically you have 3 options. Get a proper isolated power unit (it's what they're made for afterall, ie fussy effects), come up with a better design of that circuits power section or run the circuit on batteries.

As I said, a single 9v battery doesn't have enough current, but 2 in parallel might do the trick. You could try it & being the same circuit as mine you would at least see if the hum is gone when it's engaged so you'd at least know if you're on the right track (isolated power being the cause) or whether to look elsewhere for a solution to the issue. Otherwise you'll end up going around in circles trying one switching power adapter or un-isolated power supply after another & getting nowhere.

It's a clone circuit that's extremely fussy about its power supply & I sure learned that the hard way, so I understand your frustrations, but what can I tell ya...

[madbean]

Looks to me line V- IN should connect to common ground.

[Ricotjuh]

Looks to me line V- IN should connect to common ground.

In version 2 it is explicitly said that this connection may not be linked to GND.

[Ricotjuh]

I have a large box full of power adapters. Tried all I could. Also resorted to buying a few new ones specifically sold by music stores under the guise of "for pedals, no noise etc".
No luck with any of them. Always that same full-on hum when engaged. It seems all power adapters available are switch mode regardless of the blurb on the box, at least what I have are. Some say they're switch mode, some don't, which doesn't help. Only solution was a separate isolated power unit, which ironically is powered by a switching power adapter.

So basically you have 3 options. Get a proper isolated power unit (it's what they're made for afterall, ie fussy effects), come up with a better design of that circuits power section or run the circuit on batteries.

As I said, a single 9v battery doesn't have enough current, but 2 in parallel might do the trick. You could try it & being the same circuit as mine you would at least see if the hum is gone when it's engaged so you'd at least know if you're on the right track (isolated power being the cause) or whether to look elsewhere for a solution to the issue. Otherwise you'll end up going around in circles trying one switching power adapter or un-isolated power supply after another & getting nowhere.

It's a clone circuit that's extremely fussy about its power supply & I sure learned that the hard way, so I understand your frustrations, but what can I tell ya...

I'm going to try it tonight with two 9v batteries in parallel

[Scruffie]

Right... I'm now looking at the schematic for drog_trog's/DFX's circuit and as far as I can see, he's taken out ALL the power filtering in the circuit so I'm sure that's helping... Boss didn't throw that in for fun.

That brick wants a 12V input, so why is there an 11V clamping zener? And if people are running it with a 9V supply, while I prefer the series diode polarity protection, surely in this case it's not doing the brick any favors.

Where did those 220uF cap values come from? I had a look at some of their other bricks for clues and the ones that do give some circuit examples suggest much smaller values. I assume this is a switching supply in a box (hence it not liking other switching supplies) so I'd have thought LESR caps would have been the best option too.

I think someone needs to get this circuit on a breadboard and actually do some tests to get reliable operation, because the Retro-Sonic chorus uses one of these and I can't believe they'd release it if it only worked on a handful of power supplies.