56 - Building An Audio Amplifier
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- Опубликовано: 18 сен 2024
- Nick M0NTV showcases 3 different audio amps you could build for a Direct Conversion Receiver. Then he adds a fourth - his own simple design which uses only two transistors.
Downloadable Resources
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Charlie Morris ZL2CTM Audio Preamp Design (using an NE5534):
drive.google.c...
A good resource for building an LM386-based audio amplifier:
www.circuitbas...
Dieter Gentzow W8DIZ Generic Audio Amplifier:
drive.google.c...
Pete Juliano N6QW Push Pull Audio Amp:
drive.google.c...
M0NTV Simple Audio Amplifier:
drive.google.c...
LTSpice Simulation of the M0NTV Simple Audio Amp:
drive.google.c...
Thanks for watching.
Happy radio building!
73
Nick
M0NTV
What a shocker to hear Vasily Ivaneko (Todd VE7BPO)'s latest video on DCRX audio amplifiers, then yours. His went totally over my head, and yours is down on the bottom shelf for us kiddos! I appreciate your 2 transistor amplifier!
Thanks Ed! 73, Nick
@@M0NTVHomebrewing Apples to oranges. Todd wrote a 2 part deep dive into a specific audio amplifier. No one has ever done this. His work is amazing and yes it is advanced
I guess everyone is at different stages and is looking for something different. Good thing that in this hobby we are blessed with people who are willing to share their knowledge and experience in order to help and encourage others.
I'm spoilt for choice! Thanks for the video and information Nick. I may well try one of these during the dark nights of the Winter months. Best 73, Ace
Thanks very much Ace! Hope you are doing OK. Let me know how you get on if you do have a go at one of the designs. All power to your elbow! 73, Nick
Hello Nick, this has come at a very good time, in my retirement, 'I'm building a 40m receiver, and always start back to front, I will give your amp a go the speaker I'll use is a 3.5 inch 8 ohm , so this will be more than adequate for the job, Vero strip board is still my favourite way of building, if it's OK I will let you know how it's going. 73 Paul M0BSW
Thanks very much Paul. That sounds great. Hope you get on well with the audio amp. 73, Nick
Just put an audio amp in my QMX+ from QRP Labs. Took the lazy route and used a kit but it went really well! Love this, as I was looking for home rolled options 73 de VK2AOE
Thanks George! I like the fact that you can mess around on a breadboard with audio circuits without even heating up the iron. As long as you don't pull too much current and melt your breadboard that is! 73, Nick
Nick. I think this is one of your best video's. I like the way how after explaining the earlier amplifiers, you then give us your two transistor simpler design. I could have happily listened to the music coming out of that speaker, via your amplifier all day. My query is, you said you had the phone audio input at its lowest level. How is this going to compare with the output of the product detector? Is it possible you might need a preamplifier, like one of those other amplifiers had? As well as the remainder of this project, I'm also looking forward to the separate video I think you said, on how you arrived at the component values for this little amplifier. Thanks for the video. I'm learning a lot.
Thanks very much Trevor. Glad you enjoyed it. Your question is a very valid one. Spoiler alert: I've already used it in a thrown together DCR with passive diode ring product detector but with an RF preamp. It gives me more volume than I need. If I wasn't using an RF preamp up front then it probably wouldn't give me the gain I need but with more audio power coming out of the PD then the audio amp doesn't have to work as hard. As always, your mileage may vary! Once I've built all the modules I'll do some onscreen testing so you'll be able to hear for yourself. Thanks again. 73, Nick
I just finished with an AF amplifier design this last week or so. I have a few of the QRP Labs transceiver kits I built that can drive earbuds (which I can't stand wearing for long term.) My criteria was to drive a 4 ohm speaker from a single 12 VDC supply. I have tried several LM386 amplifier circuits, but for some reason I kept blowing them up. I did find a class AB discrete circuit on RUclips that I had to adjust the bias resistors some to work with 12 VDC. I am getting around 8.2 Vp-p before it starts to clip which is around 2W (more that enough for the speaker I am using). The output transistors are TIP31/32, which is overkill for this circuit - but they are inexpensive and hopefully gives me some abuse margin to keep from blowing them up. Since the output is a Darlington push-pull arrangement 8.2 Vp-p is about all you are going to get from it. It was a fun little circuit to build (I created a PCB for it) with bootstrapping applied to the input bias circuit and a Vbe multiplier for the crossover power transistor bias. I'm really happy with it so far.
Thanks for sharing. That sounds great! I think the class AB push pull is a winning combo really - if you want a discrete transistor amp that actually generates some power. In truth I was going to design one of these (and I did) but I wanted to see how simple I could make an amplifier and it still be practically useable (at least for me). Thanks again and well done on your own design. 73. Nick
👍Very good. Like a little bit of Bach.
Cheers Steve! 73, Nick
Of course the speaker would sound less tinny with a baffle plate of some sort. Other than that, a nice bit of construction that works :) Just in the process of doing something similar with TDA2030A. 73's de G4LEN.
Thanks very much. Yes, you are absolutely right about the speaker. Other (enclosed) speakers I've tried give me more lower frequencies. Once it is in an enclosure it will probably do for the 300 Hz - 3 kHz range I'll be using it for. As I say, not remotely Hi-Fi but good enough! 73, Nick
Nice one Nick. I seem to start from the back to the front.
73.
Paul HS0ZLQ, G0MIH
Thanks Paul. Yes, the joy of building backwards!!! 73, Nick
Great video, looking forward to the next video on designing your amp.
What was that enormous looking spec an in the background of the breadboard shots. Its screen seemed huge.
Hi Greg! Thanks very much. The Spec An is my Siglent SSA3015X Plus. It has got a generous screen but the best bit is the built in LAN which means I can see it and control it from my iMac. Very useful for making videos! 73, Nick
The Tip31c and Tip32c Transistors will get hot should be mounted on a suitable heatsink with transit ok r washers and heat sink compound mounted near end of PCB or wired, Traditionally Class B Amplifier s were used in portable Radio designs as used less current in quieter modes. The only bad point of Class B Amps is that there is some distortion but for portable Radio s was ok as it saved Battery current lasting longer
Hi there. I guess it depends on how much current you are pulling through those TIP transistors. I've not noticed mine getting so hot that I've had to resort to heat sinking but you are right that this would be a good idea. If by distortion you are referring to crossover distortion then this is largely avoided by running the transistors in class AB with some DC bias. Both of the amps with push pull configurations that I show in the video are like this. I have to say I'm quite interested in some of the higher switch mode amplifier classes like E. I've never delved into these before but the efficiency is wonderful and ideal for battery operation. Something else for me to explore ... Thanks for watching and commenting. 73, Nick
Is it true, that 'Diz' (Dieter) Gentzow has died?
I am so sorry to hear that! He had German based roots, ... !
A lovley and all through the heart, a real HAM-(amateur) radio guy!
I have buildt two 'one-watters' he designed, a realy good little TRX! (30m and 40m, mine was 1,6 Watt!)
The 'one-watters' are simple 'super-hets', only for CW, with a clever Super-VXO that made nearly 22kHz on 30m (10MHz), enough for 'CW-only' use!
The than follow-up '5-watters', are a little 'better' for 'DX-ing', ... Hi Hi ! ! ! I used to work w1aw/kp4 with 1,6W in the middle of the night, on 30m!
- CW only ! -
This '1,6W QSO' was "One of the QSO's", you want to made once in your "life-time" ! The "QSO' I can say, ... !
Better then 'making VK' on 20m, with a Kilo-Watt of PA-power and a yagi-antenna, direct short way, ... !
Sorry for my bad English, it's not my native tounge, so please appologies the faults I made here, ... !
73 de Markus db9pz JN39fq 5km/3miles east of LX
Hi Markus, no need to apologise my friend! Thanks for your comment. Yes, I'm afraid that Dieter died in March this year. His enthusiasm and his clever designs will continue to inspire hams for many years I'm sure. 73, Nick
👍Thank you sir.
You are welcome! 73, Nick
Gotta say my experience with LM386 has been fraught with frustration. Probably as my chips were purchased very cheap on Ali Express and are probably dodgy! 😂
I know what you mean. I managed to buy a batch of dodgy NE5534 audio preamp chips. Turns out they weren't even NE5534s at all - just some generic 741 op amps that had been rebranded and sold on. I wouldn't have minded so much if they'd actually worked! Never mind. 73, Nick
@@M0NTVHomebrewing yes…. Tried fixing AWG in my Hantek scope….. same deal…. Fixed but amplification and freq range 😫.