Low power amplifier, what op-amp?

[Rock_on]

Decided to make a mini power amplifier to be able to use my speaker on my audio interface.

While searching for circuits, LM386 is having a bad rep. TDA7052 comes next in my searches, no bad reps tho.

Would like my mini power amp to be flat if possible or transparent so it's just up to speaker on what will it sound like. I'll be using this for playing at bedroom level so < 5W is enough through software modellers, use this for mixing also that's why I want it to be flat/transparent if possible, and just amplifying sound for music.

What op-amp or circuit can you suggest? Can't build something like LM3886 gainclone stuff, not still prepared for that kind of level circuits.

[FiveseveN]

Can't build something like LM3886 gainclone stuff, not still prepared for that kind of level circuits.

All the monolythic "power op amp" type circuits are about the same. The TDA7052 simplifies it a bit only because it has fixed gain, set internally. That spares you a couple of resistors and a cap (per channel).
By the way, you do need two channels (for stereo), right?
You can find a lot of "kit" boards with the IC and all the external components populated online or at your local parts shop, if you want to go the slightly easier way.

[amptramp]

For outputs within the op amp voltage range, there are simple current multiplier stages like these for headphone amps:



There are some classic op amp circuits with external power output stages like this one:



This gives you voltage amplification greater than the op amp is good for (and the op amp power supply is not shown here.  It will be a ±12 or ±15 volt supply) and the extra voltage gain is from the first transistor stage.  Overall amplifier voltage gain is 19.

[Rock_on]

Found another good IC, TD2822. I plan on using my 12v wall wart and tend to avoid circuits that avoid mainline... or maybe not if I could just simply recycle those mini transformers found on PC speakers.

[maiko]

huh why not go for already proven desings like noisy criket or nzdogs "lil green watter"

[Rock_on]

huh why not go for already proven desings like noisy criket or nzdogs "lil green watter"

Cause they are built specifically for guitar uses?

[Transmogrifox]

Ever look at these?
https://www.parts-express.com/sure-electronics-aa-ab32155-2x15w-at-4-ohm-ta2024-class-d-audio-amplifier-board-only--320-330

I have 2 different class D amplifier boards from Sure electronics.  Usually they amount to the Class D chip datasheet typical application reference design already done for you on a PCB.  I have 1 board that is 4 channels x 25 watts per channel (well, they say 50W, but into 8 ohms it's 25W).  I also got a 2x125W board based on an Infineon chip and it's really nice.  It powers my raspberry pi media player box...I call it  a FrankenBlaster:


If you really want to build your own and you want to do better than the LM386 then you will need to go a little beyond what you consider to be your skill level. 

Also if you want it clean sounding then you should be looking at 24V or 30V supply.  It gives you a lot of head room.  Driven single ended, then 30V - 3V for limitations op amps and such gives you a useful +/- 13V or maybe a little bit more. That equates to a peak power of 21 Watts into an 8 ohm speaker.  This gives you about 10 Watts RMS with a pure sine wave, so you probably can't expect to get more than 5 to 8 watts RMS clean power with normal music program material (I assume this will be a sort of "jam-along" box).  You can get an equivalent effect by driving the speaker in bridged output mode with 1/2 the supply...so you could get the same power with a single 12V supply, or a little more headroom with a 19.2V laptop adapter...but this takes more chips and more soldering work to get this because you are basically building 2 amps for one channel.

My Frankenblaster for example has +/-50V rails, Class D (able to use full extent +/-50V) which gives possibility for 300 Watts peak, 150 Watts RMS, and probably 100 Watts RMS usable power.

At typical listening levels I use it with approximately 10 watt or maybe 25 watt RMS (which is really loud in a residential space).  Why so much headroom?  The specs on the class D chip claim <0.1% THD at 10 watts, but it goes up to several percent as you approach 80 watts. 

I'm rambling, but where I'm getting with this is 30V supply is not unreasonable...and a pre-made class D board starts looking pretty good.

Then you can focus your soldering iron on the mixer circuit because you still need to make the mixer.
A pair of 19.2V laptop power supplies from Goodwill would make a nice power source for such an amp board.

Anyway, the board I linked uses this:

And drives the speakers in bridged mode, so you get to double the 12V rail.  Looking at the THD curve it looks perfect for you 5W to 10W power range.  The THD curve starts to rise above 5W into 8ohms or 10W into 4ohms...and it's only $18.00 USD.

This Tripath chip wouldn't be a bad basis an amp if you want to do it all yourself, but I personally would rather spend 18 bucks on a pre-made board and spend my time building a fuzz or something.

Just one of many good ways of "skinning the cat". 

Then, kind of going off on amptramps recommendations, I simulated something based upon his topology (b):

[Rock_on]

Ever look at these?
https://www.parts-express.com/sure-electronics-aa-ab32155-2x15w-at-4-ohm-ta2024-class-d-audio-amplifier-board-only--320-330

I have 2 different class D amplifier boards from Sure electronics.  Usually they amount to the Class D chip datasheet typical application reference design already done for you on a PCB.  I have 1 board that is 4 channels x 25 watts per channel (well, they say 50W, but into 8 ohms it's 25W).  I also got a 2x125W board based on an Infineon chip and it's really nice.  It powers my raspberry pi media player box...I call it  a FrankenBlaster:


If you really want to build your own and you want to do better than the LM386 then you will need to go a little beyond what you consider to be your skill level. 

Also if you want it clean sounding then you should be looking at 24V or 30V supply.  It gives you a lot of head room.  Driven single ended, then 30V - 3V for limitations op amps and such gives you a useful +/- 13V or maybe a little bit more. That equates to a peak power of 21 Watts into an 8 ohm speaker.  This gives you about 10 Watts RMS with a pure sine wave, so you probably can't expect to get more than 5 to 8 watts RMS clean power with normal music program material (I assume this will be a sort of "jam-along" box).  You can get an equivalent effect by driving the speaker in bridged output mode with 1/2 the supply...so you could get the same power with a single 12V supply, or a little more headroom with a 19.2V laptop adapter...but this takes more chips and more soldering work to get this because you are basically building 2 amps for one channel.

My Frankenblaster for example has +/-50V rails, Class D (able to use full extent +/-50V) which gives possibility for 300 Watts peak, 150 Watts RMS, and probably 100 Watts RMS usable power.

At typical listening levels I use it with approximately 10 watt or maybe 25 watt RMS (which is really loud in a residential space).  Why so much headroom?  The specs on the class D chip claim <0.1% THD at 10 watts, but it goes up to several percent as you approach 80 watts. 

I'm rambling, but where I'm getting with this is 30V supply is not unreasonable...and a pre-made class D board starts looking pretty good.

Then you can focus your soldering iron on the mixer circuit because you still need to make the mixer.
A pair of 19.2V laptop power supplies from Goodwill would make a nice power source for such an amp board.

Anyway, the board I linked uses this:

And drives the speakers in bridged mode, so you get to double the 12V rail.  Looking at the THD curve it looks perfect for you 5W to 10W power range.  The THD curve starts to rise above 5W into 8ohms or 10W into 4ohms...and it's only $18.00 USD.

This Tripath chip wouldn't be a bad basis an amp if you want to do it all yourself, but I personally would rather spend 18 bucks on a pre-made board and spend my time building a fuzz or something.

Just one of many good ways of "skinning the cat". 

Then, kind of going off on amptramps recommendations, I simulated something based upon his topology (b):

Hey, that's cool! Hahaha but meh, a bit overkill. Even 2W amp would kill my room xD

I just tend to avoid the 386 cause aside from what I found that it's old and has better modern alternatives, it suffer from noise as well.

I don't  really need something fancy, just something plug n play kind of thing. I want a transparent/flat response if possible cause... you know... mix monitoring and software amp modellers :v

Bedroom level only so yea, 1-2W is fine.

[cab42]

Found another good IC, TD2822. I plan on using my 12v wall wart and tend to avoid circuits that avoid mainline... or maybe not if I could just simply recycle those mini transformers found on PC speakers.

I once built an amp based on a 2822 from a danish electronics magazine. It sounded quite good as far as i remember. They are cheap so why not try one one breadboard.

At the moment, my desktop amp is a slightly modified powered speaker I once bought for my Walkman many years ago (as in last century). It is based on a TDA2004 and it sounds killer with both electric and acoustic guitar.

BTW, I actually like my 386 amps.

[boppy100]

For a clean low power guitar amp a TDA2822M works great. 3 caps, a resistor and you are there. 
For use with a line level input a PAM8403 works very well.  It is 3 watts per channel, class D and very clean.  I use them in mono just wiring one channel.  These are complete boards and can be had from ebay less than $1 board only and $1.50 with a stereo pot.  These are free shipping prices.  I paid $0.28 each last time I ordered from Aliexpress

TDA2822 will work well with 4 AA bats.  Use your phone charger to power the PAM 8403...5 volts max

[boppy100]

For a clean low power guitar amp a TDA2822M works great. 3 caps, a resistor and you are there. 
For use with a line level input a PAM8403 works very well.  It is 3 watts per channel, class D and very clean.  I use them in mono just wiring one channel.  These are complete boards and can be had from ebay less than $1 board only and $1.50 with a stereo pot.  These are free shipping prices.  I paid $0.28 each last time I ordered from Aliexpress

TDA2822 will work well with 4 AA bats.  Use your phone charger to power the PAM 8403...5 volts max

[Rock_on]

For a clean low power guitar amp a TDA2822M works great. 3 caps, a resistor and you are there. 
For use with a line level input a PAM8403 works very well.  It is 3 watts per channel, class D and very clean.  I use them in mono just wiring one channel.  These are complete boards and can be had from ebay less than $1 board only and $1.50 with a stereo pot.  These are free shipping prices.  I paid $0.28 each last time I ordered from Aliexpress

TDA2822 will work well with 4 AA bats.  Use your phone charger to power the PAM 8403...5 volts max

That sounds promising hahaha, I'll look in to that PAM8403.

Oh again just to be clear, I'm not looking for guitar power amp. Just power amp for speakers so I can hook it up on my interface.

-- EDIT --

WOAH! I am already looking on the internet on where can I get that. There's one with volume control and the one without. If I would be buying the one without where do I add the volume control? Before the input or before the output?

And actually, it's been so long that I want to ask this, what's the difference between adding control at the input vs the output?

[boppy100]

The volume pot is usually on the input of a power amp due to power handling considerations.  If used on the output, would need a rheostat.

The Pam8403 comes with a 50k pot, but anything from 10k to 50k has worked for me.


Also, each channel is bridged, so the speakers cannot be connected to ground.

[Rock_on]

How does it sound? Hope it's balanced and not too dark/bright. I'm so excited on getting one. I still need to wait for 1 month.

[boppy100]

The data sheet shows frequency response as basically flat from 30 - 20k.  It is all about the speaker.  I generally use 3" speakers scavenged from quality surround speakers or 3 1/2 " auto speakers in my cigar box phone docks and get good reviews on the sound.  You will do best with 4 ohm.