I’m building a media streamer (Wi-fi, Pi local USB and Spotify) consisting of Volumio running on a Pi 5, RPi DAC Pro, Fosi amp and a small display for the album art.
I’ve tested the Volumio “now playing” plugin to a HDMI monitor connected to the HDMI port on the Pi. Seems to work fine.
This hardware will all go into a timber box I’ll make. I’d like this box to be as low profile (height) as possible.
What I’m after is a high resolution colour display of >=50mm in physical height. As said, I’ve proved the HDMI connection but I can’t find a small display with HDMI. I assume I can do some other protocol (SPI?) via the pass through pins on the DAC Pro?
Looking for display suggestions please.
Also looking for suggestions re a VU meter. Could be LED bars, a round (wearable I assume) LCD or god forbid (!) a back lit analogue dial. No idea re SW/HW design to make this part work as yet.
You need to be a little bit careful here. The analog VU meter is not just a moving coil meter with a VU marked dial.
To be accurate it has some pretty stringent specs including the actual meter ballistics. It is designed to present an impedance of 7k5 to a 600Ω properly terminated line. The meter itself has a resistance of 3k6 or 3k9 I forget which now and is intended to be used with a series resistor of 3k9 or 3k6 to make up the 7k5. Adjustment as to what exact level is required for 0VU is done with attenuators.
I think there are electronic Bar or Dot VU displays which simulate the definition of a VU meter electronically. These seem to have a peak hold feature which catch audio peaks and linger for a time before dropping off. Don’t quite know how this is done and have had no reason to investigate personally but I think they are sold as “VU Meters”.
I am sure a search on “VU meters” would turn up the specs and possible sources.
I actually have an analog VU meter which I made up to check audio phasing during installation and commissioning of TV studios. I remember the actual meter was purchased as a "VU meter from Farnell (now Element 14) and was pretty damn expensive.
Cheers Bob
Wikipedia article here
Hi Mark
Thanks for clearing that up.
If it just has to look the part I don’t suppose it matters much what it all means as long as it looks like a VU meter and does not interfere with the attached audio circuit all OK.
If it is pink noise you are monitoring it will be a fairly constant reading anyway if the noise is constant.
As a point of interest Jaycar used to sell a small MU45 series meter with a VU scale but I think from memory it had to be driven with an OpAmp, Nor very real or convenient . This seems to be no longer available. EBay seems to have a lot for sale. Whether they are real as in proper VU meters it is hard to say but for your application as long as it meets the criteria above what does it matter.
Cheers Bob
Of the two on your list, I’d pick the 640×480 HDMI model (E). That extra resolution is going to make the image quality so much better. Plus, these displays are so much easier to work with than GPIO based solutions, particularly from Waveshare (Pimironi displays are a bit better).
I’m hoping the VU meter is much simpler than I first thought. Volumio has a VU plug in that’ll drive an LCD1602. Once I get the parts and try it I’ll reports back.
