Raspberry Pi AirPlay Tube Radio

Intro: Raspberry Pi AirPlay Tube Radio

Vintage tube radios are nostalgic. The crackle of the game on the after dark high powered AM station from 500 miles away. The smell of the tubes and the warmth of the tones. They remind us of simpler times. Times when families sat together - not blankly staring unengaged at the TV, bur rather talking, reading, playing games and enjoying each other’s company.

So often I see these beautiful old radios ripped apart and stuffed with trendy soon to be outdated electronics. This is not that kind of story. This is a story of a radio rescue and a modern modular non-invasive upgrade.

STEP 1: Radio Resurrection

I was clunking around the depths of a damp dark warehouse garage of a charity thrift store. They proprietor walked by and asked if he could help me find anything. I told him I was looking for an old radio. He pointed to the corner and said lets look in this pile. We pulled two empty mid 70's cabinets off this well worn console under the pile of junk. He said he plugged in it a while ago and it did not work. (I know better than to plug in a tube radio without checking it first.) We pulled it out and the leg broke off. I felt bad for him, asked how much. He said $20 and it went into my truck.

After getting it home I realized he was pointing to the wrong switch to power it on. I pulled the chassis and checked for wax capacitors. To my surprise this 1967 Westinghouse had modern capacitors and some changed out tubes. This radio was taken care of and repairs in the past. Re-assembly and a quick power on test and it played wonderfully - even the turntable worked. One side did not play as loud so I had to get that sorted. It turned out to be a weak tube. $5 later I was back in business.

I wanted to find a way to modernize this radio while still preserving its original integrity. I noticed the turntable had 2 RCA jacks on it for sound output. That means I can hijack that input for an auxiliary source. I just got a Raspberry Pi 2 and this was the perfect project.

The cabinet was beat up. It had white and brown paint on it. I gave it a quick sandpaper scuff and a wipe down in a walnut stain. I opted to keep the wear marks in the wood and not do a full refinish job. The broken leg got a few few screws and some glue.

I'm no finish carpenter but overall I like how it turned out.

STEP 2: Raspberry Pi

The central piece of this build is the Raspberry Pi. I wanted the process to be simple and out of the box. I chose to install OSMC as the operating system.

I won't go into detail here because the process is so simple and well documented. At the time I wrote this article OSMC is in Alpha. Still very new, but it is where XBMC is headed. Installing it was very easy. Go to their website, download the installer, choose the install location (you will need a card reader), put in your wifi info and it is working off the bat. TheETReviews has a great 2 min video on how to install OCMC on your Pi.

I run mine without a keyboard, mouse or a TV. However during initial setup you do need to use a TV and keyboard once to change two things:
Enable AirPlay
Enable Remote Control App

They can be found under Settings - Services - AirPlay and Remote.

Grab the XBMC Remote from your mobile device's app store for remote reboots.

Note - please save your self a pile of hassle and find a wifi card that has the correct chipset. It will save you so much grief. Any of the adapters on the AdaFruit page will work. In theory anything with the Realtek RTL8188CUS Chipset will work.

Pi Parts I used:
Pi 2 (Any Pi will work)
Pi 2 case
USB power adapter
USB cable
16 GB MicroSD card (should to be between 8 and 32gb)
3.5mm stereo to RCA adapter
WiFi nub adapter

STEP 3: Input Hum and Building an Audio Isolation Transformer

The real secret sauce here is the audio isolation transformer. Tube radios have energized chassis, meaning current is flowing through the metal. If you touch it you will get shocked. This is why it is so important to keep the back on while in operation. Lets say in theory you plan on using the phonograph inputs to run a Raspberry Pi. Guess what - you will get a nasty buzz or hum from the power supply. (Not the I have a cheap transformer and it makes noise kind either.) Additionally if you have a metal device - say an aluminum macbook or iPhone - when you have the audio plugged in and you make physical contact with the metal device case you get a nice buzz out of the speakers.

This buzz is so loud you can't hear the music. No bueno. The only solution is complete electrical separation - but how in the world do you do that and still use the input? You use an inductive field from a transformer. Unlike magic smoke or snake oil this actually works - and it was about $8 to build.

As an added benefit you get a passive amplification of the input volume to the radio.

This is what I used:

Project Enclosure - Radio Shack 2701801
4 RCA Panel Mount Jacks - Radio Shack 2740346 or 2740852
2 Audio Transformers - Radio Shack 2731380

Drill and mount your phono jacks.
Glue the transformers in the middle of the enclosure with the wires in the same orientation.
The wire scheme I used is as follows:
White Input -
Red Input +
Green Output -
Blue Output +
Black Not used

Mark the input and output sides on the case.

STEP 4: Put It All Together

I picked up a four channel audio selector (Radio Shack 1500313). This allows us to use one amp input with multiple sources. Currently I'm using Input 1 for the Pi and input 2 for the turntable. I opted for the extra channels incase I wanted to add a cable for a computer or an iPhone.

The Pi, switch and cables are tucked into the record storage next to the dials. A small hidden hole in the rear of the storage area allows for cables to pass between the selector and the factory amp input line that was originally used for the turntable. You will need a few RCA cables. I also had to fab up a pair of female to female RCA adapters.

STEP 5: Operation

Dial Selection:
AM/FM selectors work as they should.
Phono selected and input 2 on the selector switch operates the turntable.
Phono selected and input 1 on the selector switch operates the Pi.

AirPlay:
Open your AirPlay enabled app
Choose the three dots
Choose the AirPlay icon
Choose your OSMC AirPlay Device

App Reboot:
Open XBMC Remote app
Click OSMC Name in the top of the app
Choose the gear icons
Choose reboot

STEP 6: Failure and Oppertunity

So....my turn table failed. The transformer that drives the motor died. Don't worry I didn't throw away the turntable, I just pulled it out. I realize this was an unfortunate failure but it allowed for a chance to think outside the box while I make a plan of attack for the turntable.

I picked up a piece of birch paneling at my home store and stained it with the same walnut stain as the cabinet. It has a good grain pattern. I cut the paneling to fit and drilled a hole for chords. Now it is a nice charging station for my laptop. It keeps my computer tucked away and out of sight.

Additional thoughts:
With the turntable out of service I can now remove the audio switch and tie the Pi to the phono input. This frees up enough space to put my blu-ray player in the console where in the record storage space. If I added an IR blaster I could easily hide it in there. I could easily see this in my living room with the TV mounted on the wall over it so the cabinet still opened. Maybe that is a project for another day.

Comments

[bricabracwizard]

Great rebuild! I wish it was only the TV taking over...but now it's tablets/iPads etc taking over!

[jscott71]

Excellent instructable. I also wanted to thank you for reviving the old tube amplifier. I'm a younger guy, but I love valves!

[Graeme_P]

About using the Phono input for the RPi - it is NOT a good idea. Records (vinyl or other material) use a type of compression to control the amplitude of the signal in the record grooves. This is called the RIAA Equalization Curve. It boosts high frequencies and cuts low freqencies before cutting the master. The phono input amplifier is specifically designed to reverse that equalization and pass the corrected signal to the audio amplifier. If you put in a signal that does not have RIAA equalization, the output will sound awful. High frequencies won't be loud enough and low frequencies will be much too loud. So it's best to continue using the other input.

[More Cowbell]

I am aware of the RIAA standards that came out in the mid 50's. That is why the phono input on modern transistor radios does not sound the same as the other inputs. However it was my understanding on analog tube radios the amplifier is signal in signal out only. It has no post input changes and all RIAA curve standards were taken care of in the record needle cartridge.

I can't speak for all radios but mine sounds good.

[Graeme_P]

If your radio sounds fine on the phono input then go for it. It could be that yours was made before equalization was standard for the phono input. That time frame is a soft target, because different manufacturers adopted the RIAA standard at different times in the 1950s - 1960s. Even in the 1970s - 1980s stores like Radio Shack sold add-on phono equalizing preamplifiers to conect between a turntable and an audio amplifier; they were about the size of a couple of decks of cards and plugged in to AC wall power.

Recently (in the last 10 -15 years), some audio systems have not come with a phono input because of the declining use of records. More recently I have heard of a few new turntables that have the equalization preamplifier built in so they can output to a "straight" amplifier and to USB.

You mentioned equalization being built in to some phono cartridges. That may be but in over 50 years of interest I have never heard of it. (But I don't always keep up with the bleeding edge, because that stuff is generally far outside my budget.) Maybe it's possible now in a microchip, but it and its power source would have to be extremely small and light. Remember that a phono cartidge is a transducer, convering mechanical motion (microinches) to electricity (millivolts). Manufacturers make them as light as possible, because the vertical force of the stylus must be as low as possible to reduce damage to the record - commonly no more than a few grams. An equalizing preamp in the turntable is reasonable, but IMO one in the cartridge is not.

[rambunctius]

I'm with you. Still using tubes and record players here and I've never heard of RIAA in a cartridge. Not saying it's impossible but..... Check where the phono signal left the arm and went into the preamp. That is where the riaa is implemented.

[More Cowbell]

Gentlemen you are absolutely correct. It is out of the cartridge but still on the turntable itself. Would you consider that standard? I've read a fair amount of classic radio guys using the phono input to run an MP3 player of some sort - which is where I got the idea. I had to whip up the at isolation transformer to get rid of the nasty buzz.

[mrandle]

I have done it with an mp3 player to the phono jack before. Sounded great but then again I'm no audiophile. I think the radio was from the 50's but yeah anything with bass in it sounded a bit muted. It was mono too so I had to fun both channels into one with resistors. other than that it worked great!

[rambunctius]

That sounds right. More Cowbell, loved that skit by the way, you should be able to bypass the riaa pretty easy. You sound like a very do it yourself kind of person. So why not try it both ways. I am guessing that you will get a more accurate signal without the record equalization curve messing with your signal from whatever you decide to run thru it. Anywho, please let us know what you come up with.

[rambunctius]

And I love your rework of the piece. Nice job!

[itobor2525]

Nice job! Everyone, run to Radio Shack before they disappear!

[mrandle]

They've been gone from canada for a long time and became "the source" I don't know why the American side didn't change.

[More Cowbell]

During this process I sourced parts from 1 store that was closing, 1 corporate store that was not closing and their website with free ship to home. I'm really sad that I won't have a component supply store in town. I know buying a pack of resisters once every few months won't keep a store in business....but I really hope whoever buys the company can make a killer online presence.

[Beergnome]

they (radio shack) are shutting down around 2000 locations, the rest will apperntly be cobranded with sprint. at least thats the plan as far as i know. so hope is not completly lost.
also, great project and great explinations! i use a vintage console hifi as 5.1 entertainment center.. unfortunatly 'll ine didnt come with anything original except the really nice kingston speakers. those now function as my front surronds.