#204

Thanks for the tips!
I’ll give both of your suggestions a try and report back with results.

Just to be sure: Do you mean measure pot6 and R10 separately or the combination of them?
Also just to be sure :stuck_out_tongue: Did you mean pot4 and R8? Because that’s the input (number 4) I’ve got the bleed on.

#205

oh yeah, I was looking at j6, check POT4 and R8 for J4. I’d check them independently, and confirm that they are close enough to the marked resistance values. do a sweep through the potentiometer, at one end point it should be dumping all of the signal into ground and the other it should be at 0(ish)ohms. If you have a spare pot around, you might grab a spare one and just do some multimeter tests to sort out how that looks with the meter and pot before beginning on the board itself.

1 Like
#206

Thanks for the suggestions/help!

I checked/compared all pots and pots + their accompanying resistor combinations and all gave the same results, so it seems like the issue isn’t with the (simple) attenuation/resistance circuit.

So I contacted David from Antumbra and he suggested to add 2 100k resistors between ground and one of the switch pins. I tried this and it’s gotten rid of the high pitched noise :slight_smile:

IMG_20190611_225417
IMG_20190611_225417.jpg2304×4608 2.45 MB

I don’t have enough of a background in electrical engineering to know/understand why this fixed it. Anyone have any idea?

The bleed on channel 4 is still there, although it’s only noticeable with very high gain so not really a problem in practice.
I’ll build a second one and do a comparison next weekend.

#207

You need to give that pcb a good clean. That might resolve your issue as there’s loads of flux residue all over your board. Use some isopropyl alcohol and a toothbrush. You’ll need to be extra careful now that you’ve attached the pots as they can be damaged if you get any of the isopropyl in them.

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#208

I have, this was just right after doing the change to test it.
How would flux cause these issues btw?

#209

Flux can be conductive, so could be the reason for leakage.

#210

Ah, OK. The flux I’m using isn’t/shouldn’t be conductive.
I’ve also cleaned the PCB after the initial soldering and still had the same issues :slight_smile:

It seems like some minor fixes to either the PCB or even the schematic + PCB are needed in that it’s just inherent to the PCB/schematic, although I don’t understand why.

#211

any flux can be very slightly conductive after it is used; it draws impurities out of the solder, traces &c

in practice, seems unlikely to have significant impact unless you’re dealing with huge amount of gain / low impedance (tho i guess if it did have an effect it would be there, on the opamp)

still good idea to clean regardless, b/c it is mildly corrosive over time)

#212

Doesn’t the conductivity only happen after a long(er) period of time?

#213

yeah, i really don’t think this is the issue here

2 Likes
#214

One thing I did notice is that it was quiet annoying to clean the flux, it became pretty sticky when cleaning it up with IPA.
I cleaned it multiple times using IPA and a soft toothbrush and after 4 times it felt all clean again.

Does anyone have any suggestions for this? Use a different fluid to clean? Different flux? Different way of cleaning?
Or is this just how it is and you just need to clean it multiple times?

#215

I had the same experience, I think you just need to clean it multiple times.

#216

depending on how far into this you want to get there are a few options.

first is getting water soluble flux or no-clean flux. I’ve found that the no-clean works so much better to flow the solder, but you can still clean it and its really easy to do. Typically the really sticky stuff is the flux inside the solder. So, you could switch to flux free solder and only add your own, although this seems like a really tedious process.

Another option I’ve seen people do is to get an ultrasonic cleaner eg: https://www.amazon.com/s?k=ultrasonic+cleaner

But I’ve not gone this route since I don’t do that many boards. One thing to note that you should never use IPA in an ultrasonic cleaner, water only!

2 Likes
#217

Thanks for the tips! I’ll have a look at solder with no-clean flux. Do you use that yourself? Any suggestions maybe for a brand/type?

I also think that for my next board I’ll simply soak it in IPA for a while when the SMD stuff is done, then I’ll only have the flux left from the through-hole parts (pots and jacks in this case) which would already make it a bit easier to clean.
I’m assuming/hoping that soaking it in IPA for a while will just get rid of it as whole instead of ending up with it still being a sticky layer on the board.

#218

I use this flux:

I’ve tried a bunch and this is the best. Easy to clean, flows great. The only issue is that the plunger is super hard to depress and it’s hard to get the proper amount. If I ordered again I might try to see if i could find it in a jar/can or something so that I could apply it with a q-tip or small pin or something.

2 Likes
#219

At the suggestion of another thread elsewhere on the internet covering this topic I started using water soluble (washable) solder for most components and then no-clean for anything I don’t want to get wet (usually pots and trimmers and wires (ugh)) and love this combo. The water soluble stuff flows really easily and cleans up really nicely with just water (though you have to remember to wash after soldering and tin your soldering iron tip before turning it off)

2 Likes
#221

Since it looks like the DIY RIP stuff is coming along (for US buyers anyways) I was thinking about how to best build/mount one. I don’t want to mount mine in a module, but rather in my case itself, so the 1/4" jacks come out the back.

I was thinking of doing the same with the 1/8" jacks as well, so I would just reach around back when I was using it, but I thought that it might be nice to make a 2hp panel that had the 1/8" inputs to RIP along with…something else.

Does anyone know of any compact (2hp-able) DIY euro stuff that could make up the rest of the space from the 1/8" RIP input jacks? Utilities and/or signal processors would be most interesting (and probably most compact).

1 Like
#222

Have a browse through these:
https://www.thonk.co.uk/product-category/hp-size/2hp/

(I’m not affliated to Thonk, just a happy customer)

2 Likes
#223

There’s always a simple passive attenuator or maybe more interesting is a passive fixed filter or 2. Do a search for “passive Moog filter schematic” or similar or take a look at bastl’s
Propust.
Edit to add: thinking about this more, I remember reading one of the fun things you can do with transformers is add a dc offset to audio signal to introduce distortion to the output. If that’s the case you could add a little high pass filter and attach it to a switch to toggle between offset and no offset before it hits the transformer. Possibly add the ground lift switch? (Just tossing ideas out)

4 Likes
#224

I’m a big fan of that little Ginko mic input module.