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Stompenberg FX: Demo and play over 150 pedals live via the internet (thomann.de)
160 points by Chirono on March 19, 2021 | hide | past | favorite | 46 comments

The idea and the execution is seriously innovative and impressive.

(After troubleshooting a local issue with a failing USB microphone I can verify that the live mode works great. This is the real deal.)

Don't miss the photos of the physical setup from the gallery features to the right of the pedal detail pages; excerpt:




It's Raspberry Pi-based. Can anyone identify that presumably audio add-on board with lots of connectors? Perhaps it's a one-off inhouse design.

Looks custom. That's quite a board sitting on top. https://im.static-thomann.de/pics/images/stompenberg/backsta...


Yeah. Makes you wonder why the PI was even needed.

The PI is needed for bridging our PCM3060 based custom sound card(via hardware i2s) with a WebRTC client that connects to the customer. It also handles all the high end internet connectivity and allows us to easily flash the microcontrollers with new software. It could have been done with audiointerfaces instead, but this approach is truly modular and allows us to scale it easily.

Well, it's a well-engineered, -documented, and -supported stable platform to handle computing needs for that giant board. Makes perfect sense, I think.

I know. I was making a bit of a joke. It's a very impressive build. ;-)

It's a inhouse design with a PCM3060 as audio codec.

After doing my research: Thomann is a very large reseller (1700 employees according to wikipedia) in musical equipment.

What's the story behind how a reseller got into designing custom raspberry pi add-on boards to demo third party pedals online?

They also are behind the design of Harley Benton branded instruments, which are made in China although under a decent quality control. I have two HB 5 string basses, the former was the bare minimum I could afford to move to the 5 strings world and see how I adapted to it. That bass wasn't great but it was well set up and tuned, had a decent neck binding, the electronic was really quiet and the sound, although a bit rubber-ish and lacking some sustain, was good enough for playing in a band in which the guitarist played gear that cost 10 times more without anyone noticing. One year later I purchased one of their HBZ-2005, which besides being a piece of beauty sounds fantastic. I paid it about 220€ years ago, before they bumped the price to about 300€ - bummer, I was considering the purchase of a spare one. Apparently it was too good to be that cheap.

My dream guitar was a Gibson Double Cut Special, because of Johnny Thunders. I finally got one for almost €3000 but hated it and returned. Then, Harley Benton released a similar model for less than €200 and it became my favourite guitar. They're amazing little instruments.

Thomann are a brilliant company, old school customer service, competitive prices, great selection. I hate that Brexit has made buying from them not worth it.

Not a musician, but it's kinda cool that they grew from




I know exactly what you mean with "old school customer service". I really hope these niched retailers stray strong against Amazon.

They're still managing to ship to the UK. You lose all the consumer protection (thanks, Conservative party!) and have to pay VAT and import dues (thanks, Conservative party!) but they're managing. They're still a fab company.

According to their blog posts it was a contract work by another company: https://feinarbyte.de/projekte/stompenberg/ (german site)

Their name seems to be a pun on "Feinarbeit", or "fine work". I love how Germany is full of those small, super-specialised tech companies.

Do you know which digipots were used? Like ericwood above I too have heard anecdotal reports discouraging their use in most analog audio circuits.

afaik they are mostly discouraged because of the various challenges coming with them (like zero crossing at high amplitudes, capacitance, etc), but it's not like it's impossible to deal with all of that.

I have so many questions as to how they're handling controlling knob changes! From the pictures it looks like they've yanked the pots out and hooked the boards up to their rig, which raises more questions.

This is something I've tried myself, and it's not trivial. Digipots won't work in the signal path and are noisy and imprecise, so companies that do this (there are very few!) like Chase Bliss use vactrols. Using those precisely is still tricky, as pot values in many circuits are all over the place and have different tapers, whereas most vactrols have a voltage/resistance curve that looks more logarithmic.

Would love more information on this, as it's a topic that's difficult to research.

Most of them are controlled with Digipots, but yeah indeed it was not easy to get it working for all the different setups.

Did you run into noise issues? I actually haven't tried a digipot in a signal path (they do work great for other controls like LFOs and the delay time on a PT2399), but everything I've read online has told me to avoid it. I'm not hearing any in the demos so clearly it's workable!

Noise was a hard problem as well. In the end what helped us a lot was to keep the FX device in its own case and even solder the digi potis right in place where the real potis had been before. You can see that here: https://im.static-thomann.de/pics/images/stompenberg/backsta...

The relais modules are on the outside of the case, but on the left you will see a flatband cable (digital) run inside of the case, where the digipoti modules will sit. So all analog signals never leave the original case and the metal housing shields all kinds of external interference.

The digipotis were actually one of the hardest problems for this project. Additional to the many pot values and different tapers, you need to also cover a wide variety of voltages that can even be centered around zero (it is an audio signal after all), so you need to be able to handle negative voltage. DigiPots also have a capacitance, so when you have to replace high values like 1M-Ohm you will wind up with a low pass filter. We built a bunch of modules for common pot values and do the taper and uncommon values in software. If both sides of a poti are used, we will need to use two digipotis to simulate them.

Super interesting, thanks for taking the time to chime in! I hadn't thought about the capacitance aspect. Was noise not as much of an issue as I've been led to believe?

Many many problems (several revisions), but I cannot go into them, because fortunately I was not part of the hardware design team. Definitely nothing I would recommend as part time project.

No worries, I appreciate the responses, knowing it's a digipot has satisfied most of my curiosity! :)

Did you consider driving the original pots in place through servos fixed to the pots shafts through shaft extenders? If yes, were there any drawbacks that made you discard the option?

Our main concerns were a) the conversion process would be much more complicated b) hardware would be more expensive c) the motors would not live as long as the digi-potis

Since you seem to have been involved with this in some way: thanks! You've earned at least one customer who had never heard of your company before.

This is the only snippet of information I could find about it. Seems indeed like noise and imprecision would be issues even if replacing the knobs and switches, the imprecision you could live with as it's a demo, but the noise certainly is not wanted.

> The first step is to dismantle them, measure the potentiometers and replace them with digital potentiometers and switches.


Hats off to those who came up with this and convinced their superiors that it's worth trying.

Most pedal demos don't give a very good idea how something will sound with your setup, because well, they're using their own, filtered through speakers and microphones at that.

You can turn off the speaker simulation + route your own setup in the "live" mode. I gave it a quick try and seems to work quite well, although the latency is quite annoying. But it's a demo, not performance tool after all.

They are self hosted in southern Germany and you connect via WebRTC, so if you are far away from there it will have additional latency, sorry no way around it.

I'm in Spain so probably closer than most others here on HN, the latency is really not that bad. Seems you're related to Thomann/Stompenberg, so just wanted to thank you for this service! Will certainly help me in finding pedals without having to go through the buy/sell process I'm currently doing.

Glad you like it! Thanks!

This is an absolutely amazing tool and is one of the main reasons I keep buying stuff from Thomann - I'm looking at a pedal, see the little Stompenberg FX demo popup and I can try it out right from my home! It's great and has definitely directly influenced some of my purchases. Hope they never get rid of it!

I started on a project of this nature about 2 years ago. So cool that they've follow through.

My method was to have users record samples, re-amp them through each pedal, record the output and then make that available back to the user.

It wasn't live/realtime. And the pedal setting has to be pre-defined.

It worked, but it was limited. My intention was to use it for rare / vintage / analog pedals.

Fun project, but this execution is waaaaay better. Very glad someone got it.

There’s a couple of similar SaaS services for analog studio equipment -

https://mixanalog.com (also has a couple of analog reel to reels)


Both really good if you want full remote access to analog studio hardware worth thousands that you don’t use often enough to buy.

You can also use multiple together and chain them however you want

If there was an open source hardware/software solution for this, or some kind of easy to use platform for people to list their gear, I think a lot of people would “rent” their gear online

There's also a video showcasing this project over at their synth channel at youtube: https://www.youtube.com/watch?v=1lBYRQUTzYk

He talks crap. Housing staid on and what you see is just the control boards...

This is genius and makes me wonder why I didn't think of it.

Edit: they already thought of that!

I wanted to do the same with hardware synthesizers, and was planning on calling the service SynthCloud but that name was already taken by someone else doing something else, and that’s my excuse :p

Wow this is awesome, as an IT guy working with webrtc/voip, a hobbyist guitar player and electronic aficionado this looks amazing. Kudos to all the team working on this.

Is there some mute button I'm missing? I've tried with both Chrome and Edge to play the pre-recorded riffs for a few different pedals and am not getting any sound. I verified I have volume on my end with a youtube video.

Same problem; I had to refresh the page to get it working.

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