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Comment by mikece | Hacker News Reader

I am still annoyed that there's not a proper audio-in capability on the RPi4. I've been wanting to use a stack of Raspberry Pi units when building a podcasting studio featuring a recording setup for linking several remote participants, but lacking proper audio hardware support for audio-in, it's a no-go (USB audio adapters and "hats" are either too flaky or so expensive as to make it not that much of a deal to go this route). I really hope a future Raspberry Pi addresses this shortcoming.

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Are you expecting them to add a hi-fi ADC and a mic preamp to a $35 SBC? The existing audio output on the Pi is of terrible quality and I would expect any future audio input to be of worse quality than those $10 XLR->USB mic adapters.

The Allwinner H2+ and H3 CPUs are used in sub $20 and sub $10 boards such as some Orange and Nano PIs though they seem to be very different beasts sound wise from the Raspberries. From page 61 of the Allwinner H3 CPU data sheet:

------

2.1.8.1. Audio Codec

- Two audio digital-to-analog(DAC) channels

- Support analog/ digital volume control

- One low-noise analog microphone bias output

- Analog low-power loop from line-in /microphone to lineout outputs

- Support Dynamic Range Controller adjusting the DAC playback output

- Three audio inputs: -Two differential microphone inputs -Stereo Linein input

- Two audio analog-to-digital(ADC) channels - 92dB SNR@A-weight - Supports ADC Sample Rates from 8KHz to 48KHz

Support Automatic Gain Control(AGC) and Dynamic Range Control(DRC) adjusting the ADC recording input

The trouble is, most of the H2/H3 boards seem to be designed as Pi-alikes and don't bother to wire up non-Pi features like line in. I'm not sure they'd even particularly benefit from doing so - not matter how useful the extra features are, all the hobbyist sites frame their discussion of other boards around how well they do the things that the Raspberry Pi can do, so chances are most people will never find out about what those other boards do better.

That is true. Although the H2+/3 have a much better line output than the Raspberries and stereo line in plus differential mic in, on most boards the only input available is a mono mic one which is better than nothing, but a real stereo line in could turn out to be really useful. Actually, the mic input shouldn't pose any problems in some aplications, save for possibly higher noise than what could be obtained by pairing a quiet single stage preamp to a line input, however I wish board makers paid more attention to the audio world; with todays faster cores and cheap memory there are some killer apps waiting to happen. As an example, guitarix (http://guitarix.org) has been already ported to ARM, so a small board with decent audio i/o would make an ideal candidate for building a very compact guitar fx processor.

I didn't say hi-fi; AC97 would be more than enough. The point is something hardware based that's on the board. I've heard that PIs are frequently used as HTPC machines so terrible audio out, as you put it, is surprising to me.

nobody uses analog audio out in an HTPC use case. You send digital audio streams out the HDMI port.

Even a low end external ADC is going to greatly outperform anything RPi could ship onboard for a reasonable cost, and even if they did ship something onboard, at this point it would almost certainly just be a USB ADC, but onboard.

Many people use analog audio because it's good value when you have old amps lying around. Most htpc users aren't audiophiles.

Calling it terrible is entirely unfair. It's perfectly usable since the fixes went in a couple of years ago. For most use cases there's no reason to buy an audio HAT any more. Perhaps the poster is using (very) old software?

And of course, HTPC users would likely be taking their audio over HDMI anyway.

First, there's nothing wrong with using quality USB audio equipment (or hats!), that's just crazy talk.

Second, you're talking about $30 or $40 per unit to upgrade to the capabilities you want. I wouldn't wait for Raspberry Pi to include additional ports, I'd check the couch for change.

So true. I've recorded plenty of jams thru a small usb pre-amp. It sounds fucking awesome too.

Bingo! Clearly, with FOUR USB ports the I/O strategy of the Pi family has been quite USB-biased since the beginning. I'm pretty sure that means the Pi designers expected people to use USB to fill in the interface gaps!

In addition to the excellent answers from other comments, I would also say that there is a benefit to external audio devices as they are less prone to interference. On-board audio can be noisy due to improper shielding.

Delivering a SBC with audio and improper shielding isn't something good engineers would do; audio with proper shielding would increase costs and/or require a less crowded board, which isn't a good tradeoff for most uses; so the good option is no audio.

You would still have connectors and wires with sensitive analog singals picking up noise. Integrating ADC and amplifier with the mic and never pushing analog signals over wires is the best that can be done.

A £5 USB audio adapter[1] 33 Reviewers, no reports of problems.

[1] https://thepihut.com/products/usb-audio-adapter

I don't believe the are the absolute highest-end quality, but there are dedicated audio hats for the raspberry pi.

https://www.hifiberry.com/shop/#boards

EDIT: Amazon reviewers seem to think the sound quality is extremely good for the price. I guess I know what I'll be playing with next.

https://www.amazon.com/HiFiBerry-6009-DAC-Pro/dp/B01MF77LH9#...

I put on of these on a raspberry pi zero w and it sounded great to my (non-audiophile) ears.

Genuine question. Aren't most mics now USB anyway? At least any mic that is better that a 5 euro one?

There are entry level mics that are USB, but professional mics have XLR outs with a hot, cold, and ground out, i.e. balanced output. You then need some sort of an audio interface like a Scarlet 2i2 to convert and connect it to your computer. An interface can also provide things like phantom power which condensers (a type of mic) require.

Generally speaking sound cards for regular computers aren't very good, so I'd bet the pi's is probably close to non-existent. You'd want some sort of DAC/ADC anyway. For listening purposes I've used a Fiio E9(or 7?) dac, and now I use a schiit stack.

Most professional mics have XLR connectors. Condenser mics require phantom power as well (unless they are battery-powered) which a "normal" 3.5mm audio jack will not provide.

The poster can't possibly expect the RPi people to include an XLR input.

Agreed, I'm not sure what they want out of the rpi.

If it's only 1-2 (xlr) mics, I would use a Scarlet 2i2 audio interface if possible and connect via its usb out. Although I have no idea how well it works with raspbian / ARM operating systems. There may be another type of interface that works with the rpi.

Either way, this is rather niche and goes beyond the rpi is intended for. You can still achieve rather good sound on a budget with a usb microphone depending on the room setup, etc.

It's strange how since the Raspberry Pi is so capable now, people expect them to build in all kinds of professional features into a $35 educational computer (PXE boot, pro audio, etc.).

The Pi can network boot.

I think maybe the 4 dropped that feature or maybe they're adding it via firmware? I remember reading a story about a company hosting dedicated servers on Raspberry Pis and complaining how they couldn't network boot on the 4, which is just ridiculous.

It's not implemented at launch, but the boot loader code is no longer in ROM so can be changed, and they said they will bring network booting later this year.

https://www.raspberrypi.org/documentation/hardware/raspberry...

"Support for these additional bootmodes will be added in the future via optional bootloader updates. The current schedule is to release PXE boot first, then USB boot."

They released the 4 without netboot and USB boot. The rough timeline that I read regarding firmware updates indicates that network boot will be done in a couple of weeks and USB boot will be done in about six weeks.

Apparently there's a HAT for that...

https://www.hifiberry.com/shop/boards/hifiberry-dac-pro-xlr/

PC 3.5 millimeter jacks do have a DC bias similar to phantom power, it’s just lower.

Not exactly. XLR mics, as mentioned above, have a balanced output which needs to be connected to a balanced input. The 3.5mm "plug-in power" mics are unbalanced.

Phantom power is usually 48V, sometimes 12V, and rarely some voltage in between.

Most profesionnal microphone uses XLR connectors. USB microphones alreaded proces the raw signal somewhat (at least an analog to digital conversion step); usually you want dedicated hardware for that.

There are good quality USB soundcards to be had these days - most with connectors for external mics. This allows you to control the a/d step completely.

I use and recommend the Samsun Q2U, a SM58-clone which has both XLR and USB. (There's an AudioTechnica version of it too I believe.)

Most microphones used in audio production are passive with usually an XLR out, so you either need an active amplifier on the device or a usb audio interface in between

So you want to use an analog microphone with the Raspberry Pi? Why?

As far as I know there are three kinds of microphones:

* The cheap analog ones, can be USB or audio jack. Presumably you want one of these?

* The digital ones, USB. Even some MEMS microphone chips now come integrated with amplifier and ADC. This can be almost as cheap as the preceding option, but can also be high quality; seems like the best option.

* The XLR proffesional microphones. You probably do not need or want this, assuming you will use just one microphone per Pi.

Not an analog mic; analog in/out from a MOTU UltraLite Mk4

Sorry, if you have an UltraLite why do you need analogue I/O on the Pi?

A Behringer UCA202 or UCA222 will admirably handle line-level ins and outs for about thirty dollars. If you're just mixing voice for a podcast I would start there. (In terms of audio quality there is a lot to be said for using an external USB adapter)

It's Linux so the setup is a little fiddly (or at least it was with piCorePlayer) for reasons that have nothing to do with the hardware, but it works fine with the Pi.

There's such a tiny amount of people who want audio-in, can't use a USB adapter, but want to use an RPi that I am pretty certain this will never be addressed.

Would be nice if the audio connector was at least TRRS.

It is TRRS. See for instance https://www.raspberrypi-spy.co.uk/2014/07/raspberry-pi-model... (found with a quick web search).

It is, the sleeve carries the composite video signal. RasPi is intended to be usable for people from all sorts of economic backgrounds; there are still places where it's much more likely to have access to an old CRT than a modern monitor.

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