Tag Archive: audio

My 1960's Nutone vacuum tube intercom

I have a 1960’s house that I purchased from the original owner. As a result I have the original Nutone intercom which is vacuum tube based and works really well considering it’s almost 50 years old. When I bought the house, the intercom didn’t work so I popped it off the wall and took a look at the tubes. You can’t tell if they are good or bad by looking at them but I wrote down the model numbers and went on eBay. I found all the tubes I needed for about $15 shipped. When they arrived I popped them in and it worked perfectly but being a 50 year old intercom, it only would receive AM radio. As nostalgic as that is, I like techno and electronic music. I noticed that the intercom had a switch that said radio or phono. I pulled the unit off the wall again and looked for the phono input and couldn’t find it. Finally I crouched down and looked up. There it was on the bottom of the unit. Since my stereo system is on the wall directly behind the intercom, I soldered in a nice piece of Canare coaxial cable with an RCA end on it and dropped it down the wall and put in a plate. Now with the switch set to phono, I hooked up to the tape recorder output on my stereo and have a CD player or airtunes pumped through the whole house. That’s how I’ve had it set up for the near four years I’ve lived here.

This has been great but from time to time I’ve noticed something missing out of the music so I tasked my friend James with building me a small two channel mixer that could fit inside the wall plate. He’s been on a roll lately of designing and cooking circuit boards for various projects and trying to perfect his techniques so I figured this would be a good, easy little project to hone some skills with. The board looks fabulous! It’s higher quality than many electronic devices I’ve opened up over the years even which is kind of scary really. It has a 78XX  series regulator for the positive side of the op amp and a 79XX regulator for the negative side of an op amp. The gain is fixed but there is a potentiometer that adjusts the attenuation on the output side. It works on 12-18VAC.  The PCB was made with the laser printer toner transfer method using glossy paper cut from catalogs that came in the mail and a cheap Scotch TL901 laminator.

Front side of the two channel mixer

Back side of the two channel mixer

He gave me the finished product and I hooked it up to test for a bit. When he had it and built it, he was testing with a 15vac wall wart so when I plugged in my 18VAC wall wart, it wasn’t being loaded down much (maybe 20mah) so there was really no typical voltage drop. That being said, it was putting almost 20 volts into the circuit and essentially running parts of the circuit at peak capacity. He suggested that I should use a lower voltage power supply.  I stopped in at a local goodwill the other day and found a 12VAC 300mah wall wart for $1. That was one problem.

The other problem was apparent when listening to it because it was distorting the audio. I handed it back to James and he took the circuit home for troubleshooting. He found that the filter caps on the output side were slightly undersized.  This was causing the negative power regulator to oscillate.

He sent it back my way with larger filter caps and I plugged in my new power supply.  Now it’s good to go and ready for installation.

Airtunes and the emu 0404

I’ve had my stereo system since 1994. For electronics that is getting old but I bought good stuff to begin with so I’ll continue to use it for many more years. It’s a Marantz system with the MA500 monoblocks that they made for years and years. It has a single cd player since that was the best I could afford as a teenager and I don’t mind changing the disc manually. All in all, it still sounds good but I was shopping in Canada with my wife’s uncle who is a real audio nut. We were at a store and I kept seeing these Sonos boxes everywhere so I asked for a demo. The salesman was really excited about it and I could see why. It basically allows you to stream audio from Napster, your pc or hundreds of Internet radio stations. The quality was entirely dependent on the bit rate of the source recording.

Needless to say I was very impressed with this setup. Of course the fact they had it hooked to a $2,000 Bryston DAC didn’t hurt I’m sure. After coming back home I did some research to figure out how I could set up something similar at home.

I hadn’t ripped my music collection yet so I had the opportunity to chose a format. I decided to go with Apple lossless. There are a couple of reasons for this. First off, it’s lossless. This means when it’s decompressed, it is bit-perfect when compared with the original wavform. The second reason is because of the transport mechanism I chose which is the Apple Airport Express. When the audio is sent across the network for playback, it is converted from whatever native format into Apple lossless anyways so I thought it would be prudent to save a step.

My “transport” the Airport Express looks just like the AC adapter for my Macbook Pro only without the cord. It has a network jack for setup and for certain uses and also has a 1/8″ audio jack that has analog and digital optical output. This is the key to my setup. With that digital output, I was able to feed the input on my new Emu 0404 USB DAC.

Is the DAC worth the extra $185 it added to my setup? YES! It made the sound noticeably clearer and crisper. Listening without the DAC, it sounds like hooking up an iPod direct to your stereo. It decent, not as bad as tape but definitely not as good as a CD. With the DAC the audio actually sounds better than my CD player. To be fair, my CD player is over 15 years old so it’s to be expected that DAC technology has come a long way since then.

The last piece of the puzzle is the interface. For this, I purchased a used iPod touch off Craigslist. There is a remote app in the iTunes store that allows you to browse your collection and playlists. It also allows you to turn on and off your speakers. This is cool because you can have several Airport Expresses in the house but choose which ones are playing at any given time. It also allows you to turn off the speakers on your computer if you desire.

There are a couple of caveats to my setup. First off, my Macbook has to be turned on, in the house and iTunes has to be open. Next, don’t try to hook anything else to the DAC. The inputs are not isolated even though it looks as if they should be. Lastly, wifi and wired networks are not perfect. I have not had many glitches and almost all have been when I’ve been downloading Linux ISO’s or something similar. Not a big deal but something to be aware of.

Overall, I’m totally satisfied with this setup. I’m confident it would sound good on a far more expensive setup than mine even. Furthermore, there is no reason someone couldn’t feed a $2,000 Bryston DAC with the Airport Express and theoretically have an even better system. I thought about it for a minute but then remembered that my wife would probably leave my if I spent $2,000 on something like that. The emu 0404 is a secret gem in the audiophiles community. It is not well respected because it look like pro audio gear instead of audiophile gear but don’t let that put you off. I’ve people spend way more for less true benefit. Cable stands and hospital grade power cords anyone?

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