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Need help in choosing an amplifier IC for DIY home 2.1 speakers

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Need help in choosing an amplifier IC for DIY home 2.1 speakers

PostPosted: Thu May 10, 2018 10:10 am
by meideolian
Hello, :wave:

Could you please help in choosing a audio amplifier IC for building DIY home speakers (2.1 system)?

Whether to go for class AB amplifier like LM1875 or TDA7295. Or go for a class D/T amplifier like TPA3116 or TA2020 or TK2050 etc.

Looking at the datasheets of these class-AB and class-D amplifiers, the performance are looking similar, referring the graphs for THD+noice vs frequency and output power etc.
For all of these the THD was at least below 0.1% across the output power values under the given max for the chip. "THD vs Frequency" graphs were more smoother for TK2050, and LM1875 and on TPA3116 graphs THD was bit higher at around 5KHz region.

From what I have read, class-D is more efficient and so I may have a smaller power supply driving it and will have smaller or no heat sink. Thus a overall compact and small amplifier will result. But heard they have some EMI issues.

On the other hand with class-AB amplifier, sound quality will be very good and not sure if these currently available class-D amplifier are producing such sound quality. But they need bigger power supply as they are less efficient, and need a bigger heat sink, so overall it will be bit bulky.

Please help in selecting the suitable amplifier IC for DIY 2.1 channel home speaker system.

thanks and regards.

Re: Need help in choosing an amplifier IC for DIY home 2.1 speakers

PostPosted: Thu May 10, 2018 11:50 am
by Sam Spoons
I have a cheap (£40) Amazon TA2020 power amp driving my LS3A clones and it sounds fantastic so I'd definitely recommend the TA2020. But I can't offer a comparative assessment as I haven't used any of the others.

Re: Need help in choosing an amplifier IC for DIY home 2.1 speakers

PostPosted: Thu May 10, 2018 2:14 pm
by ef37a
Something of a misconception here about "smaller power supply for a class D amplifier".

Power is power. If you want to deliver 20Wpch into some speakers the PSU has to be capable of AT LEAST 40-50 watts. ( "our" ID 60/100W amps are class D but they still need a pretty chunky mains traff. I can only conclude that designing an SMPSU 'in house' would have made the cost prohibitive?)

The confusion arises because of the "high efficiency" of class D amplifiers and so they are, up to 90% but a class AB amp running close to full power is crowding 80%. It is the POWER supply that can be smaller, lighter and cooler running if SMPSU. They also have the great advantage of being universal, coping usually with a 100-250V mains input.

The speakers are "home made"? Impedance? Do note that most power amp specs are given for a 4 Ohm load.

The class D amplifier is really only now being considered good enough for the critical monitor market. For a home brew I would stay with conventional class AB.


Re: Need help in choosing an amplifier IC for DIY home 2.1 speakers

PostPosted: Mon May 14, 2018 6:56 am
by meideolian
Thanks Sam and Dave,

I am trying to build it for home purpose, to connect it to my TV for movies and to my mobile for songs.
My TV is having 10w+10w speakers and if raised to high volume it gets sufficiently loud. So thinking a 20w+20w+20w speaker system will be sufficient. Please comment if my understanding on watts required is ok.
Regarding the power supply for the amplifier, thinking if i can use the 65w, 19.5v laptop power supply. Is it ok or its better to go for transformer based linear power supply?
Regarding speakers, I was thinking to use car speakers, as here we can get branded car speakers like from JBL, sony etc, with 4ohm, rms 30w, and 90 - 93db sensitivity (which seems to be good sensitivity which will give loud sound with relatively less power). With branded speakers we may trust the quality of the speakers(hope so :headbang: )

Best regards!

Re: Need help in choosing an amplifier IC for DIY home 2.1 speakers

PostPosted: Tue May 15, 2018 9:58 am
by ef37a
Ok, first off this is looking to becoming a crock of, er, COMPROMIZES!

Some numbers: A 19.5 volts DC supply will give you about 9watts per amplifier if you use 4 Ohm speakers ( nearer 30W if you doubled the chips into "bridge mode" but that is getting complicated.) .

Car speakers are designed to be compact and sensitive (do NOT believe ICE power amp speccs!) not for decent audio quality. Well, I guess if you could get some drivers out of a Rolls or a top line Merc' they would be ok but the stuff from Halfords or Joe's Nah.

You could just buy some active monitors or some passive speakers and a 'hi fi amp. The two latter can be found very cheaply at Cash Generator shops and even better a charity shop. I have bought a stonking JVC 24" FSTV for a score from one such charity store, we have a big Heart Foundation store that always has a lot of 'electricals' in it. There is a recently opened, well posh Sally army store in the town doing stuff.

Maybe you want the DIY experience? Ok, I am all for that, too few people dabble these days, many cannot comprehend leave alone make the simplest of electronics devices such as an attenuator box. I do however think this is money down the drain for a very poor result potentially and a lot of time wasted.

Lasty, if indeed the TV delivers 10W per ch, you need at least 50W pch to get a significant increase on that and have decent headroom. You will find even very budget active monitors are 30+20W per side at least and THEY are a mtr or so from lugs! "In a room" you will need a good 3dB more power per channel ( 3dB = TWICE the power!)


Re: Need help in choosing an amplifier IC for DIY home 2.1 speakers

PostPosted: Mon Jun 11, 2018 4:19 pm
by ef37a
banned user wrote:I would say go for LM1875.
Power output is more than you need.
A benefit is many built LM1875 and can give advice if you have any trouble.

Not used the LM1875 but the specc'.pdf gives a max power of around 25W and that at 1% thd, not exactly state of art! I am still of the opinion that OP will need at least 40-50Wpch.

Two 1875s per channel in bridge mode (assuming 8 Ohm speakers) should give 50W but as I said before, getting complicated and bridge mode amps can be tricky beasts for stability.

My advice is still look for a second hand Sony or Denon integrated amp. (IMO Denon never made a bad ANYTHING!)


Re: Need help in choosing an amplifier IC for DIY home 2.1 speakers

PostPosted: Wed Oct 10, 2018 10:47 am
by Onayan
DO NOT use a lousy old (designed 46 years ago) 741 opamp for audio. It has hiss, its high audio frequency response and slew rate are horrible and it produces distortion.

Audio power amplifiers can be class AB or class-D and have a specified input level. Your preamp output must produce that level. If the input level is too high then the output of the amplifier clips and produces square waves.

Impedance matching is almost NEVER done for a preamp output to a power amp input. The preamp output is a low impedance and the power amp input is a high impedance.

A 2.1 preamp has a very low frequency output to feed a sub-woofer power amp and two low, mid and high frequency outputs to feed the left and right power amps. The preamp might have the frequency crossover circuits or the power amps might have them.