New programmable switcher/looper with LCD touch screen

[Marshall Arts]

Where did you get the enclosure from? It's great as well. And yes, having a separate patch box will help with HF interference.

[vagos21]

The enclosures for the controller and looper are 1mm stainless steel sheet metal, and the top part of the controller looks like this:



Lucky me, i've been working on CNC programming for a while now! But the stainless steel finish is not easy to paint, takes special primer and i didn't have time to deal with the decals yet.
I tested the schematic you sent me about the blend/fx on, and i must say though i don't get huge pops anymore, there's quite a lot of noise when the blend is activated. Maybe it's my digital delay pedal that somehow gets its own noise in the circuit, will keep on testing this whole week on different schematics and ideas and let you know. I remember i had built a couple of years ago a nice programmable bass guitar looper, 3 loops,  5 patches, phase reversal, blend and volume stored in patches, was dead silent and all the nice frequencies came through. This was the schematic:



it was a modified version of a K&R blender and now that i see it again i have a lot of changes to suggest to myself haha 

[vagos21]

Good morning everyone, the project is progressing slowly but steadily. Today i got the first chance to test it all out, basic functions like simple switching and MIDI. It all works fine, but the midi creates a ground loop (midi cable and audio jacks on the same pedal), is this normal? Should i get rid of the midi ground, or  add a small switch to lift it?

PS: the LCD makes no noise at all, the whole setup is dead silent!  But one thing i wanted to avoid that i totally can't avoid: connecting analog and digital ground together at some point. without it, this thing like a noise beast! Why does this happen?   

Thank you all for the support and ideas, i'll keep posting progress 

[vagos21]

Hello!

Glad to report, the rig is working quite well, a demo video might be coming soon 

I use an expression pedal to control midi CC for digital pedals, and even though it works fine, if i plug in the jack while the unit is on, the board gets reset. This is because expression pedals use a TRS jack with T=analog input, R=+5V, S=Ground. So i guess the +5V and ground get short-circuited momentarily and the unit gets the reset. Any workarounds for this?

Thanks everyone!

[micahvdm]

Wowzer this project is cool! Are you gonna be making the code and schematics available for it? This would finally give me a reason to use my nextion lcd...

[vagos21]

note to self and everyone else interested: Yes, as Marshall Arts guessed in a previous post, the nextion DOES produce noise and feeds it back to the audio signal. In my case, playing really loud with the amp last night in a studio made me notice the tiny buzz. The 3 meters long cable from controller to relay unit might be helping to attenuate this noise, but i will try the following as suggested on other nextion audio projects:

• connect a 2mH inductor between LCD and +5V power feed
• weld a 220uF between +5V and Gnd on LCD.

This fix allegedly removes almost 90% of the noise, so it's test time! i will report soon with results!

[gordo]

Watching this with interest.  I've built a lot of MA's projects so I know how savvy he is.  He's a great resource and I suspect between you both you'll get this sorted out.

[vagos21]

it's really interesting to me too yes

I would like a couple of suggestions on this:
Pre/post gain: the range is +-dB and when used at +dB it will act as a buffer. But i've been reading a lot lately online that a booster can be a buffer when set to unity gain (SHO?), while there's also the exact opposite theory:

http://www.muzique.com/news/boosters-are-not-buffers/

i was thinking about incorporating the Boost and buffer 2 from here: http://www.muzique.com/tech/op-amp.htm

but i'm not a specialist and i don't know if this is the right or wrong direction... i'll use a digital potentiometer to control the gain upon loading of each patch.
any ideas are welcome!

[Marshall Arts]

The direction is OK....I tried buffers in various locations in the signal chain (up to four in my rig) and eventually decided that one on the I put (post fuzz/wah) is enough for me... YMMV. I usually build the Klon buffer (OP amp based). Using a double OP amp for buffer and boost is a great approach. Your pcb will invert the signal (no big deal, just in parallel chains to be aware of). And: Every OP amp adds a bit of noise (noticeable!), so I recommend to use as much as it takes, but not more (as always in life). :-)

[vagos21]

The direction is OK....I tried buffers in various locations in the signal chain (up to four in my rig) and eventually decided that one on the I put (post fuzz/wah) is enough for me... YMMV. I usually build the Klon buffer (OP amp based). Using a double OP amp for buffer and boost is a great approach. Your pcb will invert the signal (no big deal, just in parallel chains to be aware of). And: Every OP amp adds a bit of noise (noticeable!), so I recommend to use as much as it takes, but not more (as always in life). :-)

Affirmative! Breadboarded the AMZ buffer/booster last night and does it sound terrific! Though i have one more question: what is the use of buffering the signal before boosting it? Wouldn't just an inverting amplifier to the trick directly? Does the order of them matter impedance-wise? Buffer->Amplifier or Amplifier->Buffer?

here's also a teaser pic from the upcoming complete project of a custom pedalboard case 

[Marshall Arts]

There is no set rule for the use of buffers, unfortunately. Try and decide. Trust your ears. As I said, one buffer at the start of the signal chain worked for me. But I don't use fuzz, a lot of people do...

[vagos21]

Hello pedal gurus, merry Christmas!!!
project is on a small halt, but I'm designing the rest of the stuff to complete it. I don't know if I'll make it on time for the ΒΟΤΥ, but it's ok
I have 2 questions that would be really helpful to clarify:
1) Amp channel switching. Most switchers provide a TRS jack for dual switching. But looking at schematics, many footswitches have less with diodes and momentary or latching switches. Is it enough to use relays for the switching? Should I include optional simulated momentary action? Does this cover most of the amps?

2) about tap tempo, the pedals that support external footswitch, let's say I want to sync 2 of them, again using relays. Is it ok to use a TRS for 2 tap pedals, or will the common sleeve cause problems? So I'll need to use 2 mono jacks instead of one stereo? Sorry for asking this, I never owned any tap tempo pedals and can't think about the complications...

Thank you!
Vangelis

[nmbb]

Nice project, waiting to see more!

[micahvdm]

Hey Vagos, is this project still going?
Would love to see a video or some more pics!!

[Ricotjuh]

Have you made any progress?
I am very curious about the result.