The VRX-1 receiver kit uses a TDA7052 audio amplifier IC, which is a bit different from your run-of-the-mill LM386. Because of its push-pull output, if you use a phones jack, you must isolate it from ground. This isn’t something you have to worry about if you use a non-conductive enclosure or if you have an isolated phones jack. However, more often than not, you won’t have an isolated jack, and many of the enclosures that we use are metal.
This little hint will allow you to modify a “standard” grounded ring phones jack with a conductive enclosure (such as the 4SQRP Clear Top Tin, like the one I used).
Bill of Materials
- 3.5 mm phones jack
- Small length of 3/8″ OD (1/4″ ID) Polyethylene Tubing
- 1/4″ nylon washer
- CA glue (optional)
Cut off a piece of the 3/8″ OD polyethylene tubing approximately 1/16″ long (about 1 mm).
Place the small piece of tubing over the phones jack, so that it rests against the body. You may want to glue the tubing to the body of the phones jack.
Drill a 3/8″ hole in your enclosure to accommodate the tubing, then place your phones jack in the hole so that the 3/8″ tubing is centered in the hole. Place the 1/4″ nylon washer over the jack from the outside of the enclosure, then use the knurled nut to secure the jack to the enclosure. It’s as simple as that!
5 thoughts on “DIY Isolated Jack”
I am wanting to build a VRX 1 RECEIVER, however I can find no mention to the size of the magnet wire for the inductors. would appreciate this info Thanks
It’s nothing too critical. AWG 28 was used here, but something close should also work.
I found that there is a common rubber grommet with a 3/8″ ID requires a 1/2″ dia hole in the chassis which works well.
You can also purchase isolated 1/4″ phone jacks. They have a plastic screw part. I found them difficult to find.
I notice that, in the build instructions Step 15 it refers to connecting collector of Q6 to 12V. Template and schematic seems to indicate the emitter. Correct?