Cheap DIY Amplifiers

[momaka]

Re: Cheap DIY Amplifiers

ive been using a 12v 1.5A power brick, i think its not so much the amp as the speakers, connected it up to a sony 8 ohm cabinet i have around and it sounded a million times better, so i really dont know.

^ THIS.

1W of output power is actually quite enough when played through some proper speakers. If the speakers are ported properly, you can even get quite a bit of bass.

Remember that in order to increase the output sound by 10 dB, the output power needs to be increased by a factor of 10. So let's say you have speakers rated for 80 dB/W (i.e. 80 dB with 1W of power). That means that with 10W, you'll get 90 dB, and 100W will get you 100 dB.

I designed and tested a super-simple Class A amplifier a few months ago, and it was able to drive a pair of 8 Ohm Sony cabinet speakers at a reasonable volume despite only having a maximum output power of about 600 mW.

A switch mode power supply should be avoided because of noise from the high frequency switching.

My dad's Sony TA-F70 amp uses a switching power supply. That thing was obviously designed properly, though, because there is absolutely no noise on the output.

I myself have noticed that not all amps are sensitive to SMPSs. For example, the headphone amplifier I built which uses a Panasonic AN5272, doesn't care at all weather used on batteries or a cheap SMPS brick. It's noisy with both. I also have a pair of speakers that use a KIA6283A amp, and that thing is extremely noisy with SMPSs.

However, the thing to know about most SMPSs is that if there are any "harsh" voltage spikes on the power line from nearby light switches, motors, or relays from appliances around the house, you will likely get a loud and nasty crackle noise on the output as well. Installing proper EMI and RF filtering and increasing the bulk input and output capacitance of the SMPS may help, though.

A switching power supply will introduce some noise compared to a classic big heavy transformer but you probably wouldn't notice the difference with average speakers.

The only problem with using a normal line transformer is that you also need big output capacitors (and those can be expensive). Otherwise, you'll get lots of line hum. I guess a way around that would be to use a linear regulator and waste a few Watts of power at the expense of clean output.

[lti]

Re: Cheap DIY Amplifiers

Like I said in the above post, you don't really need to switch video hosts unless there are more complaints.

[JonathanAnon]

Re: Cheap DIY Amplifiers

Okay, I'll load it on youtube in future.

I've tried the 380N 14pin version and it sounds a lot better.

[lti]

Re: Cheap DIY Amplifiers

There are tons of ads and the video takes a really long time to load. The video quality wasn't what I was talking about.

There isn't a need to put on a different website like YouTube unless someone gets malware.

The LM386 isn't a very good chip, but it works okay for headphones and higher impedance speakers (16 ohms or greater).

[JonathanAnon]

Re: Cheap DIY Amplifiers

What you mean? The misleading buttons? I was gonna throw it up on youtube, but I didnt want to have to fill out all the forms.

I've just looked at it again, and I think you might be talking about the video quality. That's my fault, I just did a quick vid on my phone.. It's meant to be HQ video on my phone, but it completely loses focus when you bring it in close...

[lti]

Re: Cheap DIY Amplifiers

That is one lousy video hosting website.

[JonathanAnon]

Re: Cheap DIY Amplifiers

Hi guys,

I was about to post about amplifiers earlier this week only I didnt get a chance. I've made a video showing what I have made up at the moment. I dont like those kits made in the original post. I prefer to build from scratch. And this is what I'm working with at the moment..

http://videobam.com/jnDwq#

The schematic is pretty much the same as this..



I just used whatever electrolytic capacitors I had around for decoupling, and one large electrolytic cap to smooth out the DC coming from the battery..

thanks,

[redwire]

Re: Cheap DIY Amplifiers

Chip-amps are a bit of work to get lowest distortion. I've used TDA2005, TDA2030, TDA2040 etc. (they're the same family/topology), and the TDA2822 for flea power stuff (its too little for hi-fi), and STK's for bigger amps.
All the IC's sonically benefit from decent capacitors- beefy electrolytics on the rails and outputs (if single supply) and film types elsewhere.

Oddly enough, RF bypass on the rails/input and output inductors makes a huge difference. Chip-amps are very sensitive to RF coming in on the input or speaker wires, usually AM radio.

eBay has tons of Chinese TDA2040/50 amps

[Logistics]

Re: Cheap DIY Amplifiers

A TDA2822M isn't good enough for different caps and resistors to make any difference in sound quality.

I disagree. The fact that it is a very inexpensive amplifier should tell one that it can use all the help it can get. Distortion is going to be a large issue for something of this low-caliber so bypassing the electrolytics in the audio stage, even bypassing the power-cap should help eliminate some unwanted noise.

Could you explain how using bipolar coupling caps will help? Those caps will have half the power supply voltage across them.

Audio has A/C characteristics and does benefit from non-polarized capacitors. I've tested this out on cheap amplifiers myself and heard differences, first-hand. In some cases it may not seem better because, for example, you may lose low-frequency extension, but gain high-frequency extension or perhaps a gain in mid-range frequencies. Often times different parts need to be used in tandem to see a beneficial change rather than simply a change.

But if you have any equipment that has small films at the line-level stage, before the amplifier IC, try swapping them from films to electrolytics (polarized or non-polarized) or vice versa and see the huge difference, firsthand.

In any case I would never prescribe to using crappy parts because the amp seems crappy,too.

[lexwalker]

Re: Cheap DIY Amplifiers

For simple and cheap DIY amplifiers, I would usually suggest TDA1517 although its a Class B amplifier.

The nice thing about this I.C is it uses very minimal components, can use single rail supply and lower voltages. For those ingenious enough, can even build one without requiring any PCB or circuit boards.

[mariushm]

Re: Cheap DIY Amplifiers

I didn't say it was innacurate, just that tda2050 will not necessarily be just as hissy as your tda2005. It should give much better audio quality.

http://stason.org/TULARC/entertainme...hat-is-Cl.html

I'm too lazy to write my own text so I'm just gonna paste fragments from that page.

Class A refers to an output stage with bias current greater than the maximum output current, so that all output transistors are always conducting current. The biggest advantage of Class A is that it is most linear, ie: has the lowest distortion.

Class B amps have output stages which have zero idle bias current. Typically, a Class B audio amplifier has zero bias current in a very small part of the power cycle, to avoid nonlinearities. Class B amplifiers have a significant advantage over Class A in efficiency because they use almost no electricity with small signals.

Class B amplifiers have a major disadvantage: very audible distortion with small signals. This distortion can be so bad that it is objectionable even with large signals. This distortion is called crossover distortion, because it occurs at the point when the output stage crosses between sourcing and
sinking current. There are almost no Class B amplifiers on the market today.

Class AB amplifiers are almost the same as Class B amplifiers in that they have two driven transistors. However, Class AB
amplifiers differ from Class B amplifiers in that they have a small idle current flowing from positive supply to negative supply even when there is no input signal. This idle current slightly increases power consumption, but does not increase it anywhere near as much as Class A. This idle current also corrects almost all of the nonlinearity associated with crossover distortion. These amplifiers are called Class AB rather than Class A because with large signals, they behave like Class B amplifiers, but with small signals, they behave like Class A amplifiers. Most amplifiers on the market are Class AB.

TDA2005 is class B.
TDA2050 is class AB.

tda2005:

thd 0.2% avg. 1% max (f = 1 kHz; VS = 14.4 V; RL = 4 Ω; Po = 50 mW to 4 W

tda2050:
thd 0.02% avg, 0.5% max Vs = ± 22 V, RL = 8 Ω, f = 1 kHz, Po = 0.1 to 20 W, f = 100 Hz to 10 kHz;

TDA2050 will, in theory, distort less.

TDA2005 is designed for car radio aka environments which are subjected to constant noise from driving, engine humm etc, stuff that will hide some of the background noise...
The IC is also kinda designed to work in bridge mode, one IC driving one speaker, not two speakers.
It's also sort of made for 2-4 ohm speakers... tda2050 can work just fine with better 8 ohm speakers etc..
See the supply voltage rejection graphs on pages 13-14 in datasheet, see how it handles high frequencies.... or how it doesn't better put... compare with pages 8-10 in tda2050 datasheet etc etc etc

[ben7]

Re: Cheap DIY Amplifiers

TDA2005 is not the same as a TDA2050. It's a class b amp, tda2050 is class ab.

Uh, then please explain why my comment about the TDA2005 is inaccurate.
Still, it is a linear (i.e. not digital) amplifier...

[mariushm]

Re: Cheap DIY Amplifiers

TDA2005 is not the same as a TDA2050. It's a class b amp, tda2050 is class ab.

And if you really want to, you can use slightly less than average linear regulators to reject some of the noise from the smps psu. Most linear regulators accept up to 40-50v in, and since they drop only 1-2 volts, 2-3 watts of dissipated power on the linear regulator would not be a problem.

[ben7]

Re: Cheap DIY Amplifiers

Here's a tda2050 based amplifier:

http://diyaudioprojects.com/Chip/DIY...hip-Amplifier/

The tda2050 datasheet also has a circuit to make the chip work with single power supply (not + and -) so if you make that you could power the amp straight from a 24-36v DC switching power supply. A switching power supply will introduce some noise compared to a classic big heavy transformer but you probably wouldn't notice the difference with average speakers.

TDA2050 likes higher voltage, it needs a minimum of 9v (+/- 4.5v) to output about 1-2 watts of audio power and about 25-40w at 42-45v (+/- 20-23v) ... less with 8ohm speakers, more with 4 ohm speakers..

See page 8 in https://cdn.badcaps-static.com/pdfs/...31cada06bb.pdf

The IC is cheap enough and easy to put on regular prototyping board (but make good traces with solder and thicker solid core wire on bottom as in the first link) : http://www.digikey.com/product-detai...28-5-ND/634792

I once powered a TDA2005 amp off a PC power supply. Delta brand, with good caps. Lots of hissssssssssss from the speakers! These were cheapo crap speakers too.

[mariushm]

Re: Cheap DIY Amplifiers

Here's a tda2050 based amplifier:

http://diyaudioprojects.com/Chip/DIY...hip-Amplifier/

The tda2050 datasheet also has a circuit to make the chip work with single power supply (not + and -) so if you make that you could power the amp straight from a 24-36v DC switching power supply. A switching power supply will introduce some noise compared to a classic big heavy transformer but you probably wouldn't notice the difference with average speakers.

TDA2050 likes higher voltage, it needs a minimum of 9v (+/- 4.5v) to output about 1-2 watts of audio power and about 25-40w at 42-45v (+/- 20-23v) ... less with 8ohm speakers, more with 4 ohm speakers..

See page 8 in https://cdn.badcaps-static.com/pdfs/...31cada06bb.pdf

The IC is cheap enough and easy to put on regular prototyping board (but make good traces with solder and thicker solid core wire on bottom as in the first link) : http://www.digikey.com/product-detai...28-5-ND/634792

[ben7]

Re: Cheap DIY Amplifiers

A TDA2822M isn't good enough for different caps and resistors to make any difference in sound quality.

Could you explain how using bipolar coupling caps will help? Those caps will have half the power supply voltage across them.

The regular polarized capacitors are just fine, as long as you have the polarity correct. (Negative to speaker if the speaker is tied to ground, and negative to amplifier if the speaker is tied to +V)

A better one would be a TDA2050. It will require a higher power PSU, and a heatsink - this is because it has a greater output power capability. You should then use a speaker that can handle the power. The cheap half watt speaker will likely burn out. A switch mode power supply should be avoided because of noise from the high frequency switching.

[budm]

Re: Cheap DIY Amplifiers

I will not use wire wound resistor unless they are non-inductive wire wound type. Same with Polyester film, make sure they are non-inductive type also.

[lti]

Re: Cheap DIY Amplifiers

A TDA2822M isn't good enough for different caps and resistors to make any difference in sound quality.

Could you explain how using bipolar coupling caps will help? Those caps will have half the power supply voltage across them.

[Logistics]

Re: Cheap DIY Amplifiers

If it were me, I would replace the 470's with bipolar Panasonic SU's, the 10uF with an FM, and absolutely chuck those 100nf (0.1uF) ceramics and get metallized polypropylene films. Also bypass the 470's with .1 or .01uF films. Any resistors I would replace with wirewound and hurl the carbons it probably comes with.

[Heihachi_73]

Re: Cheap DIY Amplifiers

8 ohm 0.5W unbranded speaker = PC speaker. Not worth worrying about.