I fortunately found long ago at a recycling center more than 50 destroyed no-brand walkmans (the cheap ones that were produced in mid 2000). I managed to salvage some 40 brand new LM386 and many transistors that all were new from factory. For my needs, I think I have enough. I tested them and all were functional in the specs from datasheet.
A couple of diodes between the bases of the output transistors, with a trimmer resistor across them to set idle current, would eliminate most all of your crossover distortion. Keep in mind that the fast slews of the op-amp trying to eliminate the crossover distortion (caused by running the output transistors in pure class B) might well create noise in your receiver. This would disappear with my suggested change, which converts the output stage to class AB.
But that would reduce efficiency and power handling. For voice reproduction class B with NFB is good enough and I don't think it creates much interference. 0
The LM4871 'boomer' (or clones like the 8002) have taken the place of the LM386 in my uses. Cheap, super easy to set up, flexible, and bridged. something like 3W from 5V supply. That said, a buffered op amp like this is pretty easy to set up too, and permits surprising power. I modified your circuit a tiny bit, and am getting about 2W output (on an +/-9V supply), with a (very) small amount of crossover distortion, using an NE5532 op amp and some random TO-126 transistors. Component count is minimal, especially if used on a split power supply.
Thank you forn the information on the ICs. I'm back after a few decades off the key and needing to find more modern amp chips. I've seen videos telling / showing how to tame / perfect the LM386 by using .27 capacitors on 3 of the pins. That's done to make the IC quieter (noise) and to eliminate some BCI. I'm wondering if there's the need for that sort of mod for the 8002 etc. Thank you.
Привітання,як вам гарно жилося, років 50 назад у нас не було такого для дітей 10-15 років,бо не було такого різноманіття у радіо деталях, дякую вам,але я всерівно мав успіх
Back in the early 1980s the 741 was my first IC. I remember studying it's schematic and trying to work out how they got all those components into such a tiny plastic box.
Thank U for this video. By the way there is a lot of IC's which considered very good with less components as well as it has a wider operation voltage rang Such as TBA820m , TDA7052 , TDA2822 TDA7231 , TA7331 , TA7368 , CD7368 , LM4871 , FM8002a and the powerful TA7252AP
Surprised how clean that output is. That said, most of the circuits I've seen for this include two diodes to bias the transistors apart from each other.
I’ve never heard it call Manhattan style construction… but they always look interesting when built as long as they are built well and in so,e ways can be more pleasing than using traditional stripboard or veroboard. I always like designing a PCB although, can’t beat a PCB
Pardon me for asking, but what are the purposes of R7 and R8 on the +V rail. Also is it suitable as an audio amplifier, as I can't get any sound out to a speaker. Thanks
R10 is in the circuit to provide a load on the output transistors at high frequencies. The reactance of C4 is high at audio frequencies, which essentially takes R10 out of the circuit. But at much higher frequencies, the reactance of C4 is reduced and R10 becomes an increasingly heavy load on the output. This helps prevent high frequency oscillation.
I don't think you need R9. Unless I'm missing something, I don't see it doing anything useful. I'm also worried that U1B is going to have stability problems. My quick suggestion would be to have a series resistor between its output and the bases of the transistors. (My gut says 47R to start.) I'd also add a small value capacitor as direct feedback from the output to the inverting input. It may be fine now, but I think you'll get oscillations if you use an opamp with a higher GBP. When using op-amps with output boost stages in the feedback loop, you need to keep the GPB of the op-amp lower than that of the boost stage. However, it's working for you, so my suggestions could be unnecessary. :D
It's very easy to build a 3 transistor circuit which is functionally near equal to the LM386. I do think the LM386 will continue to be fabricated into the future, but it is a bit under engineered, as it prefers 16 ohm loads at higher power supply voltages. Your circuit is nice, though.
Thanks for the video, it didn't occur to me that the ubiquitous 386 would be put out to grass but it happens to us all in the end. Newbie question, what would be the nearest drop in replacement/alternative when a schematic calls for an LM 386?
tda2822M is used very often has 2 channels which can be bridged. If you want to do discrete transistor 8050 8550 is a great pair. also used a thermally compensated bias with a pot and a sense transistor. 3-5 ma bias is enough. Opamp is not needed at all. just 1 single transistor can drive it . May want to bootstrap load resistor for driver transistor.
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I fortunately found long ago at a recycling center more than 50 destroyed no-brand walkmans (the cheap ones that were produced in mid 2000). I managed to salvage some 40 brand new LM386 and many transistors that all were new from factory. For my needs, I think I have enough. I tested them and all were functional in the specs from datasheet.
I love that Simpson analog multimeter! I have a RadioShack analog multimeter that I still use that I made from a kit when I was a kid in the 1970s.
A couple of diodes between the bases of the output transistors, with a trimmer resistor across them to set idle current, would eliminate most all of your crossover distortion. Keep in mind that the fast slews of the op-amp trying to eliminate the crossover distortion (caused by running the output transistors in pure class B) might well create noise in your receiver. This would disappear with my suggested change, which converts the output stage to class AB.
But that would reduce efficiency and power handling. For voice reproduction class B with NFB is good enough and I don't think it creates much interference. 0
@@westelaudio943 Well, that of course falls under the aegis of one of my favorite adages: "If it works, don't fix it." 🙂
I would enjoy seeing the schematic for your regen .unfortunately i dont have much luck with them
Nice use of cad to design manhatten boards
The LM4871 'boomer' (or clones like the 8002) have taken the place of the LM386 in my uses. Cheap, super easy to set up, flexible, and bridged. something like 3W from 5V supply.
That said, a buffered op amp like this is pretty easy to set up too, and permits surprising power. I modified your circuit a tiny bit, and am getting about 2W output (on an +/-9V supply), with a (very) small amount of crossover distortion, using an NE5532 op amp and some random TO-126 transistors. Component count is minimal, especially if used on a split power supply.
Thank you forn the information on the ICs. I'm back after a few decades off the key and needing to find more modern amp chips.
I've seen videos telling / showing how to tame / perfect the LM386 by using .27 capacitors on 3 of the pins. That's done to make the IC quieter (noise) and to eliminate some BCI. I'm wondering if there's the need for that sort of mod for the 8002 etc.
Thank you.
I remember using a 741 as a simple amp some 50 years ago.
Привітання,як вам гарно жилося, років 50 назад у нас не було такого для дітей 10-15 років,бо не було такого різноманіття у радіо деталях, дякую вам,але я всерівно мав успіх
Back in the early 1980s the 741 was my first IC. I remember studying it's schematic and trying to work out how they got all those components into such a tiny plastic box.
@@ПашаПитецкий- Yes, I had electronics as a kid but I was very poor and had to save up to buy anything so it was all very precious to me.
Thank U for this video.
By the way there is a lot of IC's which considered very good with less components as well as it has a wider operation voltage rang Such as TBA820m , TDA7052 , TDA2822 TDA7231 , TA7331 , TA7368 , CD7368 , LM4871 , FM8002a and the powerful TA7252AP
Surprised how clean that output is. That said, most of the circuits I've seen for this include two diodes to bias the transistors apart from each other.
Yes, I experimented with a few such circuits and the crossover distortion was too high for my liking.
I’ve never heard it call Manhattan style construction… but they always look interesting when built as long as they are built well and in so,e ways can be more pleasing than using traditional stripboard or veroboard. I always like designing a PCB although, can’t beat a PCB
I really like the look of that construction. what pcb material did you use for the positive bus bar? It looks a lot thinner than normal clad pcb.
I think R6 and C2 are redundant. The output of the first stage is at the correct DC bias to connect directly to the second stage.
One diode between the transistor bases halves the slewrate requirements.
Nice informative video. Can you give a link to the schematic?
It's at 4.19 in video
Thanks! Nice project.
Very interesting video. Thank you. (I just subscribed.)
Pardon me for asking, but what are the purposes of R7 and R8 on the +V rail. Also is it suitable as an audio amplifier, as I can't get any sound out to a speaker. Thanks
Voltage divider to reference U1A and U1B at 1/2 Vcc.
sorry for a stupid question, but what is the purpose of R10?
R10 is in the circuit to provide a load on the output transistors at high frequencies. The reactance of C4 is high at audio frequencies, which essentially takes R10 out of the circuit. But at much higher frequencies, the reactance of C4 is reduced and R10 becomes an increasingly heavy load on the output. This helps prevent high frequency oscillation.
I don't think you need R9. Unless I'm missing something, I don't see it doing anything useful. I'm also worried that U1B is going to have stability problems. My quick suggestion would be to have a series resistor between its output and the bases of the transistors. (My gut says 47R to start.) I'd also add a small value capacitor as direct feedback from the output to the inverting input. It may be fine now, but I think you'll get oscillations if you use an opamp with a higher GBP. When using op-amps with output boost stages in the feedback loop, you need to keep the GPB of the op-amp lower than that of the boost stage.
However, it's working for you, so my suggestions could be unnecessary. :D
It's very easy to build a 3 transistor circuit which is functionally near equal to the LM386.
I do think the LM386 will continue to be fabricated into the future, but it is a bit under engineered, as it prefers 16 ohm loads at higher power supply voltages.
Your circuit is nice, though.
thanks
Thanks for the video, it didn't occur to me that the ubiquitous 386 would be put out to grass but it happens to us all in the end. Newbie question, what would be the nearest drop in replacement/alternative when a schematic calls for an LM 386?
Tda2822. 8 pins IC. 2channel 2x1watt or. 1x3watt. Work from 3 to 18 volt. Cost. 3 US dollar. ..
Це є великий клас
nice
Buf634 saves everybody
tda2822M is used very often has 2 channels which can be bridged. If you want to do discrete transistor 8050 8550 is a great pair. also used a thermally compensated bias with a pot and a sense transistor. 3-5 ma bias is enough. Opamp is not needed at all. just 1 single transistor can drive it . May want to bootstrap load resistor for driver transistor.
Быстрее будет вырезать кружочки или прямоугольники на плате
But more prone to short circuits to ground.
Интересный материал, но не на русском. И переводчик технический не осилит.