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PostPosted: 06 Dec 2013, 21:25 
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Joined: 03 Aug 2008, 20:22
Posts: 386
Location: Denver, Colorado
Hi all,

Its been a while since I built anything. My other hobbies have kept me busy, as well as tie up a lot of money :).

Anyway, I wanted a very simple project that really did not focus on fidelity, but rather tuning.

I found this gentleman's version of a single tube regen, with a LM386 output.

The part count is low and the sensitivity is quite remarkable. I am able to tune in stations from 600-1600 Khz, most US AM stations. I have also tuned some other frequencies to receive the Radio Havana Cuba signal. That was exciting.

If I can only wind a coil to receive CW transmissions, that would be icing on the cake .

Here is the site I used. http://www.vk6fh.com/vk6fh/12au7regen.htm
all credit to VK6FH for drawing the schematic

Image

It only draws 149mA of current using a 12v 7aH battery. Will last weeks.

Image

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PostPosted: 07 Dec 2013, 02:00 
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Joined: 08 Aug 2009, 03:11
Posts: 2229
Location: Chilliwack, BC
That's awesome! Looks nice, too! :D

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PostPosted: 07 Dec 2013, 10:51 
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Joined: 28 May 2008, 21:53
Posts: 4580
Location: Winnipeg, CANADA
Cool! This looks like a nice simple regenerative receiver to try. Using the LM386 is a pretty a efficient way to drive a small speaker from a tube. :idea:

Cheers

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PostPosted: 07 Dec 2013, 16:35 
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Joined: 04 Jun 2008, 20:59
Posts: 4050
Location: Arizona, USA
Hi Nice build. It looks a lot like the circuit of the thing I use as an avatar. It doesn't have the 386 but the rest of the circuit is quite similar. I found that I had to hand select the 12AU7 for best performance. Some were noisy and some had too little gain.

Good listening
Bruce

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PostPosted: 08 Dec 2013, 15:59 
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Joined: 03 Aug 2008, 20:22
Posts: 386
Location: Denver, Colorado
Thanks all, yes I do agree with the 12au7 being hit and miss. The clear tops have provided the most gain and I especially like them in audio dedicated amps. The clear tops tend to be more balanced.


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PostPosted: 12 Dec 2013, 12:25 
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Joined: 11 Dec 2013, 12:30
Posts: 4
Location: Pittsburgh PA
Hi All,

I just joined the forum and I am mixture of Ham Operator, Audiophile, and AM DX'er. I have a AM regenerative radio that is a home brew and it has a 6SN7 dual triode tube that is putting out its audio in a baby impeadance matchining transformer. Right now I have to use amplified multimedia speaker.

Thanks for the reply Roger. I will send some pictures and I will see if I can draw something up in TubeCad. I bought this on Ebay and I am using it to learn from. I want to add on enhancements as I go. This looks like a great project.
Thanks Dan


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PostPosted: 12 Dec 2013, 16:00 
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Joined: 03 Aug 2008, 20:22
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Location: Denver, Colorado
Nice looking project, from the looks of it my regen is very similar in design (mine is just crammed into a little enclosure). Which B+ voltage are you working with? I see a switching power supply.

The link I posted has the design with the LM386 replacing the output transformer. If your B+ is 12 or lower you can go with the LM386, if it is 12-18, you can go with LM386N-4.

To keep the retro thing going, you can put the 100K audio pot above the platter and the chip and proto board underneath.

http://www.ti.com/lit/ds/snas545a/snas545a.pdf


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PostPosted: 13 Dec 2013, 12:21 
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Joined: 11 Dec 2013, 12:30
Posts: 4
Location: Pittsburgh PA
I am using that because it puts out 32 vdc and then I am using another wall wart putting out 6 vdc for the fillament. I will probably replace that with a 6.3 vac transformer with an in line resistor to bring it in tolerance. My mains are 122 vac and the secondary puts out 7.8 vac I think that is abusing my little 6SN7. I have a really good idea for the plate voltage. I bought a :
LM386 Audio Amplifier Module 200 Times 5V-12V Input 10K Adjustable ResistanceLM386 Audio Amplifier Module 200 Times 5V-12V Input 10K Adjustable Resistance
and a :
High Voltage DC Power Supply Great for Nixie Tubes and Magic Eye MADE IN USAHigh Voltage DC Power Supply Great for Nixie Tubes and Magic Eye MADE IN USA

Maybe you guys can help me integrate these devices.


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PostPosted: 13 Dec 2013, 13:21 
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Joined: 03 Aug 2008, 20:22
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Location: Denver, Colorado
Cadmandu wrote:
I am using that because it puts out 32 vdc and then I am using another wall wart putting out 6 vdc for the fillament. I will probably replace that with a 6.3 vac transformer with an in line resistor to bring it in tolerance. My mains are 122 vac and the secondary puts out 7.8 vac I think that is abusing my little 6SN7. I have a really good idea for the plate voltage. I bought a :
LM386 Audio Amplifier Module 200 Times 5V-12V Input 10K Adjustable ResistanceLM386 Audio Amplifier Module 200 Times 5V-12V Input 10K Adjustable Resistance
and a :
High Voltage DC Power Supply Great for Nixie Tubes and Magic Eye MADE IN USAHigh Voltage DC Power Supply Great for Nixie Tubes and Magic Eye MADE IN USA

Maybe you guys can help me integrate these devices.



Ok, the schematic I used is at the top of the thread. Did your radio come as a kit? Do you have a link to the schematic?


As for filament voltage, the dc wallwart should be fine. The one in the pic looks like a switching power supply. Not sure if you got that with the kit, or from the thrift. These are great as they usually have internal protection, in case of a quick short. They can be found at the thrift store for $1, to reproduce the internal circuitry one would have to spend close to $50 or more in discrete components and protoboards. but I digress.

The DC-DC power supply you quoted, (no link though) is used to drive "Magic Eye" tubes i/e 6AB5, 6E5. It can be used for the 6sn7 if the circuit calls for it. Not sure of the current rating, but my amp draws less than 200 mA with 12 vdc. With a separate heater power supply you should be good to go.

lastly for the LM386, the link you quoted is a separate, stand alone module, probably similar to what is inside your powered speakers. You can use it in your circuit, but the power supply will have to be separated from the 6SN7. The lm386 chip can be purchased at radio shack, it is one of the few IC's they carry.


So, when you have a chance, scan or link your Regen schematic and we can go from there.


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PostPosted: 14 Dec 2013, 17:42 
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Joined: 11 Dec 2013, 12:30
Posts: 4
Location: Pittsburgh PA
Hi All,
I purchased this regen off of ebay from a guy in Florida. He told me it was a design taken from the radio ace. I am going to attach the schematics the orig and the improved. I will sometime this weekend figure out which one of these represent what I have. I will then draw something up that is mine. This is a very good link and full of good info for the newcomer. I will turn you on to a few buddies of mine that build really nice twinplexs as well.

http://www.members.iinet.net.au/~cool386/kits/ace.html

http://w5dxs.tripod.com/6sl7.htm

http://faculty.frostburg.edu/phys/latta ... nplex.html


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