Soundcard: HifiBerry vs Pisound

[Bl4ck-Eyes]

Hi there,
I'm a Bass Player.
Probably it is a stupid question, but I would like to use PiPedal as a multifx-NAM Pedal in my Pedalboard and I cannot decide on the best Soundcard to use with a RaspBerry PI5 8GB using PiPedal.

What is better for my use? Using Jack adapter is not a problem for me.
HifiBerry DAC+ ADC Pro: https://www.hifiberry.com/shop/boards/hifiberry-dac-adc-pro/
PiSound: https://blokas.io/pisound/

Thanks in advance.
Fra.

[rerdavies]

I would very much recommend using an external USB audio adapter, instead of a pi hat. There are a number of downsides to using a pi hat. 

1. The inside of a Pi case is a difficult place for a DAC to live from a signal-to-noise-ratio perspective.
2. Pi hats tend to use fairly mediocre DAC chips that are intended for use as DACs on phones, where signal quality is not all that important.
3. You won't run into problems converting line-level or microphone-level signals to the correct impedance and level that (for example) an RCA jack provides. Last time I checked -- which was a while ago -- all the pi hats devices that provided 1/4" jacks were out of stock. You do NOT want to connect an instrument cable directly to an RCA jack!
4. Pro-level audio devices are insanely difficult to design properly to get the best possible SN/Rs. (If you're a musician, you automatically qualify as "pro-level" from an audio perspective. How cool is THAT?). Not to say that any of the existing hat manufacturers haven't done it right. I have no experience with that, because every time I tried to order one, they were out of stock, and expecting to do another manufacturing run "really soon now". Just saying that actually doing it right is really difficult from an engineering point of view. And usually requires capacitors to filter power rails that are too large to fit on a pi hat.

When Pis first came out, Raspberry Pi OS (and linux in general) did not properly support USB audio adapters. Pi hats were useful back then, because USB audio wasn't an option. But Linuxes (and Rapsberry Pi OSes) have been providing amazing support for USB audio for several years now. (Since linux kernel 5.15. we're on 6.something now) You will get comparable (or better) latency from a USB audio adapter these days. And, since USB audio adapters runs off power supplied by the Pi over the USB cable, that's not a problem either.

There's a small inconvenience of an extra cable and an extra box; but I really think USB audio is the way to go.

[redvoodoochild30]

Hi.
I think that you could take a look at Pisound : https://blokas.io/pisound/
I think it answers to every problem you list.

It's what I use whith pipedal, and it works like a charm.

(And thank you for your work, I can launch 2 nam instance with no Xrun, with a RPI5 and PIsound) !!

:)

[Bl4ck-Eyes]

Taking a look at Rerdavies response, It would be better to use an external USB Soundcard if I understand right what he said.

[rerdavies]

ps: if you really want to go the HAT route, you might want to investigate the HiFiBerry Studio ADC XLR. I'm not SURE that it will work better with instrument-level inputs (or that it will work at all, honestly), but, it's likely to have much higher impedance than an RCA connector (which may affect how your tone controls work). Not a total expert on this subject; but I think this true.

[Bl4ck-Eyes]

Hi!
Thanks for your response.

This is my signal chain: Bass >>> Polytune 3 Tuner with integrated Buffer >>> (NAM/PiPedal) >>> TwoNote LeBass Tube Preamp >>> DI or Output to Amp.

So I don't think that impedance would be a problem for me.
Anyway I can try to find an used VERY SMALL external usb soundcard with more quality to add on my pedalboard. Any advice?
Cause I was thinking that Raspberry + USB Soundcard + Bluetooth footswitch is large, isn't it?

Thanks in advance.
Fra.

[rerdavies]

Behringer does some good cheap USB interfaces. Not sure what the current state of the universe is with their current models, though. Disclaimer: I have no direct experience with Behringer USB devices, but by reputation, and by spec sheets, they look good.

[Bl4ck-Eyes]

What have I to look for? 24bit and 192kHz right? Like a Scarlett Solo or similar.

[rerdavies]

You probably won't use 192kHz (too much compute). And 24-bit (or 32-bit) doesn't mean you're actually getting that much signal; just that they're sending you that many bits, some significant number of which will contain absolute pure noise. My rough understanding is that amazing devices will give you about 20 bits of signal above the noise floor; adequate devices will actually do 16 bits of signal; and it not uncommon for cheap devices to give you as little as 10 bits of actual data, which is perfectly adequate for a phone ADC, but dismal for any musical purpose.

The key spec is actually anything related to Signal to Noise Ratio for the ADC (the input). It seems to be easier to do DACs than it is to do ADCs. If you are looking at a device that doesn't quote a SN/R spec on the spec sheet is an indicator that you should stay way. Unfortunately, there's a couple of ways to quote the SN/R specs. The most common is DBa (a weighted). An EXCELLENT result would be 130Db (a-weighted); a passable result would be ~105db = actually 16 usable clean bits of signal. I don't know what piece of specmanship manages to get from 16 bits (96db) to 105db, but that seems to be the going figure. I would guess that 130db translates into ... 20 good clean bits, maybe? Those 4 bits do make a difference though!

Distrust very small USB adapters. Part of the reason why the pi hats have trouble is that you ideally need a row of 3 or 4 3/4" tall capacitors to clean the power rails of the ADC -- which doesn't fit on a pi HAT very well. There may be black voodoo active semiconductor wizard magic to get around the requirement for the big capacitors these days; but I don't think so.

[Bl4ck-Eyes]

So maybe the best I can do atm Is using what I already have: Scarlett 2i2 3rd gen.
It Is not Small, but I can give It a try at least, then go for something smaller like Apogee or similar.

[rerdavies]

A scarlet would be perfect! Sorry. Should have said so earlier

…

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[Bl4ck-Eyes]

Cause I use It as desk soundcard hooked up on my PC usually :) But I Will use It in my pedalboard of you suggest It as low latency :) Thanks!
Any tips for a Footswitch too? :p

[rerdavies]

Nope. lol. Personally, I use a micro midi keyboard, that has a nice array of pads, so I can't offer you any advice.

Be advised that i have an outstanding problem report wrt/ a MIDI-over-bluetooth footswitch. It's gone stale, so I'm not sure what happened with that. For the meantime, it might be advisable to NOT buy a bluetooth footswitch.

[Bl4ck-Eyes]

Probably I Will go for Mvave Chocolate plus. Really cheap and usable on USB.

[jujudusud]

Hi here, I'm using a pisound for more than 4 years with a pi3B.
Just don't take advices from guys that do not know this card.
Pisound is a really good IS2C audio and midi card and it can come with a cheap (price) box for thé raspi5 + the latest pisound compatible with it.