DIY Audio Projects Forum

Hi everybody,

I managed to get a few of those TA7642 chip AM receivers. I immediately build a simple radio to compare it with my 4 Germanium transistor radio. Well, the 4 transistor radio is a reflex receiver and it is therefore much more selective than the TFR chip. I have a super strong station right in front of my door, 200 kWatt of Jesus Christ (the church station, haha), 24/7. The station is only maybe 2 miles air distance from my house, so selectivity is very important to me. It seems thee are two kind of people, the one kind that loves the chip and the kind that hates it. The ones who love it live in the country side, I suppose, haha. For me, to have any fun with it, I'll have to somehow teach it more selectivity. I have to do some research, I do not know if it is possible to give this circuit some regeneration, if not I will try to build a receiver with a second tank circuit, this will help, too. Any suggestions are very welcome.

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Greetings from Holland, Ben

My DIY Audio Projects:
- Single-Ended 12B4A tube amp with ECC802S driver
- DIY Push-Pull KT88 tube amp (OddWatt amp from scratch)
- 832 / GU32 tube push-pull amplifier project

Here are some interesting schematics.

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Greetings from Holland, Ben

My DIY Audio Projects:
- Single-Ended 12B4A tube amp with ECC802S driver
- DIY Push-Pull KT88 tube amp (OddWatt amp from scratch)
- 832 / GU32 tube push-pull amplifier project

Hi Ben!

I´m happy to see you into the radio business!

You find excellent selectivity with super-heterodyne circuits (455KHz IF).

With transistors you need some thick wire for the inductor coil, to low its impedance to match you input circuit in order to get better selectivity.

You can also use another input circuit (before the receiver) to work as an antenna tuner. With this you can tune the antenna circuit to select only the desiring station instead of overloading the receiver´s tuning circuit. This can be done with a single 4 gang varaiable air capacitor (2x for the receiver + 2x for antenna), and so you´ll have only a single knob! My advise is to get one with small tuning capacitors to help.

With tubes, things are a little bit easier, because tubes have much higher input impedance ready to match a coil (with thinner wire) and excellent selectivity.

Keep posting!

Best Regards from Lisbon!
Miguel

Hi Ben,
if you need more selectivity with your TA7642, tap the maincoil at 1/3 winding
from ground. You can also try 1/4 or less.

Best regards
joe

Hallo everybody,

I just survived my 5th heart attache, got home today. I am alive and kicking, well hard to kill, I suppose. Anyway, here are some pics of my latest radio, it uses a AC128 and a 1000 ohm to 8 ohm transformer, works great with just one volt and consumes only 2 mAmpere, but is still powerful enough to drive a speaker with room filling volume.

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Greetings from Holland, Ben

My DIY Audio Projects:
- Single-Ended 12B4A tube amp with ECC802S driver
- DIY Push-Pull KT88 tube amp (OddWatt amp from scratch)
- 832 / GU32 tube push-pull amplifier project

Good to have you back Ben.

Cheers

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[ DIY Mains AC Power Cable Cord ] - [ K-12 Tube Amp Kit ] - [ Tang Band D4-1 Horn Speaker Kit ] - [ Monoblock Push-Pull KT88 Tube Amp Kit ]

can you please give me advise on where to buy TA7642 or MK484 in and around Amsterdam, I will be there for a few days in June.

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etherman55

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