Transistor equivalent

[spec]

What is PoP? Peak power is simply the real RMS power number doubled. An amplifier output power rating must include its supply voltage, its load impedance, the frequency, the distortion and the duration of the test before the IC melts.

List not intended to cross what you say- just a rough list taken from the data sheets as a matter of intrest- blast from the past. My little boards had a minature mains txformer 1mf cap and two diodes producing 12V. I used them as a standard audio amp for small jobs. As I said very pleasent sound but not hifi of course.

Up to about 10 years ago, Philips and others produced about 76 amplifier ICs, mostly for cars. Not many are available today.
You will not get much output power with a supply as low as 2.5V but Texas Instruments has 42 low voltage class-AB and 36 class-D amplifiers, most are bridged, some with a voltage boosting circuit for higher output power and some have AGC.
A single rechargeable Lithium cell is 4.2V when fully charged but there is a new one (Li-Fe?) that is less.

Yeah, I know about LiIon bats. The voltage range is my spec for general purpose from a coulple of NiMh to a single LiIon to logic lines. Perhaps I could come up to the 2,000s and go class D. What class D chips would you recommend for low, medium and high power. I know I can look it up but I always like the opinions of actual users.

I see that ST have dropped their range of TDAxxx type chips. Always liked them. Much used in cheap guitar amps.

 

[spec]

here is a website that sell components,spec can you go to this link and read all the transistor can be use, I don't know a lot of them. there are 3 page, roll down, you can see button to jump to page 2 or 3. I apologize because let you to involve this problem, but I am busy now, learn to pass the first important exam of this year. The next year I will have even more important exam in June so wait for my amp in the next year summer holiday
https://mualinhkien.vn/danh-muc-san-pham/185_tran-cam.html

Hi Nikolai,

Here is the answer to your amplifier needs from your preferred store:

https://mualinhkien.vn/san-pham/864/lm3886.html

This would make a nice 40W amp

Let me know what you think?

 

[audioguru]

I have never built a class-D amplifier. Their spec's are good and they sound good.
I am glad to see that the excellent class-AB LM3886 amplifier IC is available in Vietnam.

 

[spec]

 

[Nikolai Petrenko]

I have never built a class-D amplifier. Their spec's are good and they sound good.
I am glad to see that the excellent class-AB LM3886 amplifier IC is available in Vietnam.

Yes, but cost very high: 120000VND, while TIP41: 3000VND, 2N3055: 18000VND
Can you post both circuit of LM3886 and dicrete transistor,spec? I will consider to choose later.
I have known LM3886 has excellent sound, I have heared it at least 4 times at my friend house

 

[Nikolai Petrenko]

Class A room heater

You know of some great gear- dont let Nikola see this. Six heat-sinks. If it is a monoblock that means output tripples. How much: many $Can I would think

You don't happen to have a shematic?

(I started life in civvy street as a test engineer- many stories)

Tell the truth, servo systems have always scared me to death- much too complicated. Even the feedback in audio power amps does my head in!

HoHohO, HaHaHA lol "dont let Nikola see this"

 

[spec]

Yes, but cost very high: 120000VND, while TIP41: 3000VND, 2N3055: 18000VND
Can you post both circuit of LM3886 and dicrete transistor,spec? I will consider to choose later.
I have known LM3886 has excellent sound, I have heared it at least 4 times at my friend house

I see -thanks for info Nikolai

HoHohO, HaHaHA lol "dont let Nikola see this"

 

[Nikolai Petrenko]

wow, why the circuit look not "well", I mean the ground too funny. Can you tell my what small transistor will use?

 

[Nikolai Petrenko]

View attachment 95620

Thank a lot because you spend a lot of time to help me. How many watts of this circuit?

 

[spec]

 

[spec]

wow, why the circuit look not "well", I mean the ground too funny. Can you tell my what small transistor will use?

'Circuit look not well' because that is how you must wire it, especially in class AB, not so critical in class A but still very important. If you want to know why just ask, but I think you must be getting a bit tired of all the theory.

The wiring is vital for two reasons:
(1) Minimise distortion
(2) Minimise chance of oscillation

There are three different families of transistors: darlington drivers, voltage amplification stage, and the rest.

I will choose some transistors, hopefully from your preferred supplier.

 

[spec]

Thank a lot because you spend a lot of time to help me. How many watts of this circuit?

I am learning Eagle circuit capture, so it is good practice. It's also good for me to brush up on audio amps.

TIP41/TIP42 Amp
Power with TIP41A/TIP42A & 60V total supply= 40W
Power with TIP41B or C/TIP 42B or C & 70V total supply= 50W

LM3886 Amp
+- 30V supplies= 40W
+- 35V supplies= 50W

 

[audioguru]

Here in the West, electronic parts are very inexpensive because money here grows on trees (it is easy to make a lot of money working here). I am usually shocked to hear that many people on the other side of the world that I have never seen get paid in a week about what I got paid in a couple of hours. Now I am retired and my government is paying me a comfortable pension, I can buy almost anything I want (but not a Lamborghini car yet). We pay a lot for government taxes but there is plenty of money to pay for it.

We had a special shopping day recently called Black Friday. Stores were selling large 4K Ultra High Definition flat screen TVs for the price paid by working for a few hours. Amplifiers were selling with so many channels (7.2) that there are speakers all over the place.

 

[spec]

Yeah, we are lucky, but I remember when I first got married things were tight. If the cooker or boiler failed it was a major disaster. It always worries me the things that people throw away too. I was at the local munisciple dump (council tip in UK) and this bloke rolled up in a posh 4x4 (SUV) and chucked a top-of-the range, almost new excercise bike in the metal dumster (skip in UK). I asked him about it and he said he had bought it recently but it got in the way so he decided to get rid of it.

Where I live, you can get amps & speakers, PCs, laptops for nothing. If they have a slight fault they just chuck and buy a later version. Also just outside town they crunch perfectly good cars (autos). Many are better than my car which is 17 years old now.

The trouble is that labour costs are so high and products are so complex the often it is not economical to repair them. With me labour is free.

 

[KeepItSimpleStupid]

The parallel resistor/inductor combination right before the speaker is called a Zobel Network.

The inductor is "made" by usually wrapping an insulated solid wire, usually about 18 AWG around a 2 to 5 Watt Carbon composition resistor. Carbon is important in this case.

 

[spec]

Keep, I think you meant the R and C to ground. The inductor is there to decrease the load the the amp sees at high frequencies and the 10R resistor damps the inductor to prevent ringing. In the audio band, the inductor is effectively just a piece of wire. With the LM3855 you can leave the inductor, damping resistor, the cap on the inputs and the 50p cap and resistor in the feedback network out. In fact many circuits on the net do just that. There have also been some posts on the net about frequency instability with the LM3855-probably why. The belt and braces approach is always best in the end.

 

[KeepItSimpleStupid]

Right Church, wrong pew. Thanks for that.

https://www.trueaudio.com/st_zobel.htm

L1 and R11 in post #330 https://www.electro-tech-online.com/threads/transistor-equivalent.146091/page-17#post-1240572

The network is still made the way I said. A wire wrapped around a carbon composition resistor.

 

[spec]

thanks for the info about inductor construction.

Only my view, but I think that one of the critical factors in realising a good sound from an audio amp is to get it unconditionally and absolutely stable- this is where all the sevo loop stuff comes in as previously discussed. Like I said before, most of my amp experiments have ended up as highly stable 4MHz oscillators and I had a graveyard of incinerated drive units to prove it!

 

[spec]

It always amazes me how well class AB amps work when you think about what is going on with the output power transistors, drivers, and voltage amplification stage (VAS).

(1) Current from zero to max

(2) voltage from max/2 to zero to max

(3) non-linear gulps of current from the power lines

(4) Very complex load of speakers, Xover and speaker cable- current and volts can even be out of phase.

This is an area with many views, as we have seen already on this thread, but this is my thinking:

(1.1) Provide the transistors with over-the-top heat sinks

(1.2) Provide as much current capability as you can, at least 2X theoretical minimum, for a given power.

(1.3) Provide as much volts as you can

(2.1) The extreme voltage excursions are very demanding and cause all sorts of problems, including the Early effect, which is a major issue with the voltage amplification stage (VAS), where, by definition, you need to provide voltage gain which implies common emitter operation. A cascode configuration gets around the problem but increases the amps overhead (dropout) voltage. Emitter follower configuration for the output trans and drivers are commonly used for this reason.

(3.1) Use big caps connected to the output trans. Put HF capacitor in same position. Use massively thick wires- multistring or single core- not sure. Use audiophile caps with low ESR etc

(3.2) Use correct-order connections especially earthling and use massive star points.

(4.1) This is the killer because, like with lab power supplies, you never know what the load will be. Having a good voltage and current capability is the first start but getting unconditional frequency stability with such a wild and undefined load is difficult/impossible. And electrostatics look like a huge capacitor with all that that implies in terms of absolute current and the phase between voltages and current.

Being an engineer, I rubbished all the talk in the late 1970s about speaker cables, gold contact connectors, speaker stands and the like, but was proved wrong.

At one time we did some experiments with different speaker cables and there definitely was a difference; the ludicrously expensive Van den Huls sounded the best, but some thick speaker cable from the local store wasn't too bad. 30A single copper-core mains cable was even better. Being a skin-flint, that is what I had- nice grey finish.

Best stop now, but I haven't said anything about the speaker load and cable matching.

Strangely, the LM3886 does not have a symmetrical output stage which is surprising. The rest of the chip looks nice though- perhaps National could't fabricate PNP power trans on the chip.

 

[Nikolai Petrenko]

If you want to know why just ask, but I think you must be getting a bit tired of all the theory.

May "ground loop"? I have test on small TDA2822M amp, if I wire the ground like a loop, the amount noise will increase.
You can explain all reasons, I feel interested in learning about electric, my favor led me to good at physic in the class. (I am 14 years old, and like a young bull )