Radio Related Projects
This is a page of projects I have worked on, or am working on that is related to radio or vintage electronics.
Push-Pull 6T9 Stereo Amplifier
This is a project I recently finished. (November 2008)
It is inspired by an article in Nuts and Volts magazine of the Stereo 6T9
amplifier, however I decided to use the 6T9 in push-pull configuration. Except for a very slight bit of background hum, the performance is absolutely wonderful! It outputs about 8-10 watts undistorted and has plenty of gain.
The chassis is made with a sheet of brass for the top surface with a frame of Poplar wood which can be purchased from Lowes in various small dimensions. I stained the Poplar wood with Minwax Red Mahogany stain, then finished with Zinsser Amber Shellac. I have to admit the results came out beautifully! Therefore I have been using the same technique on many other projects!
I just love the look of wood with brass and black bakelite!
Here is a view from the rear. I included 3 stereo inputs with a provision for a 4th. If I can gather the parts, it will be an optical S/PDIF port.
My amplifier project is showcased on DIY Audio Projects where more information about it can be found. Thanks goes to Gio for having my project on his website!
Push-Pull 25L6G Stereo Amplifier
Here is another of my amplifier designs. This one was intended on being a series string heater design without a power transformer. It worked that way, but I now use it with an isolation transformer. I will NEVER build another stereo amplifier this way again!
it works quite well and has excellent fidelity! The audio transformers are Edcor GXPP10-8-8K which were made before Edcor put the pretty blue bell covers on them. I decided to put cast aluminum relay covers over them as they don't look near as pretty.
The chassis is steel painted with black wrinkle spray paint I bought at O'Reillys Auto Parts. Again, the wood trim is Poplar bought at Lowes stained with Minwax Red Mahogany and finished with Zinsser Amber Shellac.
Regenerative Radio Receiver
This is a project currently under construction. I originally built it in the Spring of 2001, however, I had problems getting it to work properly and one day I accidently left it in the car during an incredibly hot sunny day. The shellac finish blistered. I decided to totally tear it apart, repair the damaged finish and rebuild it using knowledge I gained from the problems I had in 2001.
It uses a type 32 tube as an RF amplifier, a type 30 as a regenerative detector and another type 30 as an audio amplifier. It is designed to drive headphones. Also, for the AM Broadcast band, I plan to use a loop antenna which I built for this set.
This is the loop antenna I built to go along with the Regenerative Receiver above. Though, I can use it with other projects.
It stands 50 inches tall and 40 inches wide.
Lately, I have been using it as a loop crystal radio. With ONLY a variable capacitor, 1N34 diode and a high-impedance piezo-electric earphone.
This alone without any ground or external antenna brings in WLW in Cincinnati very clearly. I have listened to 610 WTVN in Columbus Ohio, 650 WSM in Nashville, Tn as well as 740 CFZM in Toronto, Ontairio, Canada! I'm simply AMAZED what a simple thing as this antenna setup can do!
the AA0ZZ IQPro DDS VFO
Well, this is a diversion away from tube based projects. It is a "Direct Digital Synthesis - Variable Frequency Oscillator" used for signal generation and Ham radio applications.
It came as a kit from Kanga US. It is designed by Craig Johnson AA0ZZ and comes as a few circuit boards and parts which you must assemble then decide what kind of enclosure you want to put it into.
I decided to go with my tried and true use of Poplar wood with Minwax Red Mahogany stain and Amber Shellac finish.
The style of the enclosure was inspired by the 1947 Howard FM tuner which also uses a wooden box with a lexan front panel.
More details of construction can be found in this PDF file.
OTL Audio Amplifier
This is another tube type audio amplifier project which is waiting on some refinement. It uses absolutely no transformers and drives a 16 ohm speaker directly! It uses 3 type 6082 double triodes which were originally made for series pass voltage regulation in power supplies.
Its performance is not the greatest as the 6082's I'm using are quite worn out. I will try to find some new/unused tubes and try again.
More information about this amplifier can be found here
More to come