modified a guitar looper in order for it to take a USB cable that would
1
take midi controls via pro micro arduino
(achieved that through vital support on this forum. thanks paul!)
2
power the looper via 5V coming from the usb port
unfortunately though, the 5v usb power introduced a lot of hiss to the audio signal. don't know how to approach this, but tried this today:
cut an usb cable and spliced in 5v from a battery, while arduino data still came from the usb port. this turned out to remove 80-90 % of the noise.
so, if in principle i just have to cleanup the 5v from the usb, how would i go about this? is there a ready made solution (like a small boost converter)? can i follow a schematic and build something from scratch?
I play with Software Defined Radio and finally abandoned switching power supplies altogether in favor of a linear (transformer-based) supply. That may be overkill for your needs, but you might want to Google "linear power supply" and look at some of the products available and their specs.
We apologize for any inconvenience and look forward to serving you again soon.
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and following that link I get told by the EUROPEAN DATA PROTECTION SUPERVISOR that I am not allowed to access the Guitar Center because I'm not in a location allowed by EU regulations. Last time I looked, the UK was still in the EU !
CurtCarpenter:
I play with Software Defined Radio and finally abandoned switching power supplies altogether in favor of a linear (transformer-based) supply.
so, if i understand correctly, it's better to ceate linear 5V fresh from the 230V socket, rather than filter out the 5V already present in the usb cable. found a product that does just that (too expensive dor what it does)
You have a problem here with ground layout. You can use an inductor and capacitors to filter the 5 V, but the ground connections must be laid out in a certain manner.
i wonder what how - in terms of performance - this two different solutions differ from one another
Wow -- that is an impressive result orinocopaul, and without spending some significant money I'm not sure you'll get much improvement over it with a linear supply. I'm going to have to try that filter myself -- and thanks for the link to the article.The BLM18PG221SN1D is available from several distributors, and isn't expensive at all.
One thing you might want to test is what happens if you load one or more of your other USB ports at the same time as your filtered port. If you try it, I hope you'll share the results. Definitely a good find -- thanks again!
stowite:
and following that link I get told by the EUROPEAN DATA PROTECTION SUPERVISOR that I am not allowed to access the Guitar Center because I'm not in a location allowed by EU regulations. Last time I looked, the UK was still in the EU !
Maybe that's your problem... I can open the link just fine, and get a price in my local currency (HK$ - never been in the EU, even when it was still a UK colony).
finally understood what was meant by ground layout. thanks paul!
replicated a filtering scheme using caps + ferrite inductor. however, i did not get to the point of hearing its effect: once I plugged in the audio output jack, ground was passing through as well and looping back through pc > usb and so on. ordered an usb isolator. waiting too see what that does to the noise.
meanwhile here is my diagram. it's working fine.
the only problem occurs if I connect both the usb cable and the ac adapter. (even though the barrel connector interrupts usb ground). this happens regardless to the 5V looping through the amp. somehow:
groundless 5v from usb + 9V AC freezes the looper after half a minute of so...
).