LM3886 Amplifier advice needed

[solderburn]

Wise choice. Get two of those power supplies, and use one for +V and one for -V.

The LM3886 will barely be turned on by a total of 24V, and will put out only a few watts. Hooking two of them in series for +/-24V or +/-20V gets you into the 40+ watts range.

Do you mean wiring one power supply dedicated to V+ and the other to V- or, Wire them in series similar to series wiring Batteries?

[solderburn]

After reading the datasheet, It specifies 68W into 4 ohms @ 28V+
And further down the page it lists 40W into 4 Ohms with V+ ±21.0V @ 4.5A

Is this true, Or there other factors at play?

Datasheet;http://www.taydaelectronics.com/datasheets/A-225.pdf

[R.G.]

Do you mean wiring one power supply dedicated to V+ and the other to V- or, Wire them in series similar to series wiring Batteries?

Yes. Treat them as you would two 28V batteries. The DC outputs are hooked in series, the (-) of one to the (+) of the other. This joined point connected to signal ground for the power amp. The remaining unconnected (+) terminal is V+ for the amplifier, the remaining (-) is the V- for the amplifier.

After reading the datasheet, It specifies 68W into 4 ohms @ 28V+
And further down the page it lists 40W into 4 Ohms with V+ ±21.0V @ 4.5A
Is this true, Or there other factors at play?

This is correct, as far as it goes. With  ±28V, the LM3886 will put out 68Wrms into a 4 ohm load - for a while. What they don't tell you is that it can be very difficult to get enough heat sinking on the chip to let it do this for longer than a minute or two without it turning off from being too hot. If you plan to try to run 4 ohm loads from a single LM3886, it is quite difficult to keep it cool enough, and the heat sinks needed get BIG.

It is actually much better to dedicate one LM3886 to each 8 ohm speaker. The LM3886 will happily drive one 8 ohm to about 35-40W with  ±28V to  ±30V power supplies. At about $5 per chip, it's cheaper to put in another LM3886 for each new speaker than to buy the additional heat sinking to get the power out of one chip.

I tell people a lot - dealing with power amplifiers, the actual power amplifier circuit is a minor part of what you have to do. The big parts of the task are buying and/or building the DC power supply to keep it running, and the heat sinking arrangement to keep the waste heat from killing it, as well as the enclosure to put it all in. The actual power amp circuit is almost an afterthought to all of this.

[tca]

I should also add that people usually forget how loud is a 1W amplifier in a typical living room with a >90dB speaker!

[PRR]

> how loud is a 1W amplifier in a typical living room

I think he was thinking of playing with a drummer.

That kind of level is perhaps better bought than built. (Not that _I_ ever used many pre-made amps; but take my suggestion anyway.)

[tca]

That kind of level is perhaps better bought than built.

You are correct, is cheaper to buy one than build a 1W amp,  but apart from this, I see no other reason to buy one.

Not that _I_ ever used many pre-made amps.

Same here.

[solderburn]

Thanks again!

After more research, I discovered this switching power supply http://www.ebay.com/itm/New-24V-DC-6A-145W-Regulated-Switching-Power-Supply-/130458428959?pt=LH_DefaultDomain_0&hash=item1e5feda61f
So after reading threads about people using them I'm going to use this one. After thinking more about the dual PSU, I don't want to wire it wrong a blow 'em up. the switching power supply is more convenient and eliminates the chance of the series wiring shorting. It will give me enough watts to do what I want, And It'll be fun.

And to about cost, Since I have the chassis, Two 12" speakers and a cab it cuts down the cost a lot. Adding up the parts I need its about 40$ give or take. but if I didn't have these things this would probably be in the $120+ range. In which case I would down tube amp lane.

[solderburn]

.

[casey]

 

[Brymus]

Wise choice. Get two of those power supplies, and use one for +V and one for -V.

The LM3886 will barely be turned on by a total of 24V, and will put out only a few watts. Hooking two of them in series for +/-24V or +/-20V gets you into the 40+ watts range.

Note that this will still give you some problems with AC wiring, as you'll have to provide 120VAC to two power supplies, but it's a simpler problem that wiring a mains transformer.

You shouldn't buy that power supply it isn't bi polar.

[solderburn]

Wise choice. Get two of those power supplies, and use one for +V and one for -V.

The LM3886 will barely be turned on by a total of 24V, and will put out only a few watts. Hooking two of them in series for +/-24V or +/-20V gets you into the 40+ watts range.

Note that this will still give you some problems with AC wiring, as you'll have to provide 120VAC to two power supplies, but it's a simpler problem that wiring a mains transformer.

You shouldn't buy that power supply it isn't bi polar.

Yes, a few posts further he explained how to series wire them for V+,V- and ground.

And I found this one. http://www.ebay.com/itm/New-24V-DC-6A-145W-Regulated-Switching-Power-Supply-/130458428959?pt=LH_DefaultDomain_0&hash=item1e5feda61f
Pretty sure it will work, considering on other forums people have used switching power supplys with success.

Just so happens that I was getting ready to pull the trigger on parts tomorrow and was adding them up part when I saw your post.

[Brymus]

I was perusing stuff at Mouser in DIP form and came across this :THAT 1510-1512
It seems perfect for a simple guitar pre amp for the LM 3886,It can use +/- 20v power supply,has A lot of available gain and good noise,rejection,ect.
My only question is the input impedance is listed as min 10K max 15K,seems kind of a narrow range.
So does this mean an input buffer designed to have a 10-15K output impedance is needed?
Or am I reading the data sheet wrong?
http://www.mouser.com/ds/2/407/1500data-4823.pdf

I also really like this op amp:LME49720
It seems like a dual version would/could make a great pre amp,and active tone control in one for guitar.
Or two for stereo Hi Fi chip amp use.
http://www.mouser.com/ds/2/405/snas393c-316845.pdf

Real curious if I am picking good IC choices from just searching and reading the data sheets?

I recently picked up a couple of these:LM4780
http://www.ti.com/lit/ds/symlink/lm4780.pdf
For building a 120W Guitar amp,and a 60W stereo home Hi Fi amp.
So I am trying to decide on pre amps for both.
My thought on the guitar amp was to use a super clean pre amp for the clean channel,and use a FET amp emulator for the high gain channel.

[PRR]

THAT 1510 is a MICROPHONE preamp.

Low impedance balanced mikes.

The other extreme from high impedance unbalanced guitars.

(If you have a Les Paul *Recording* guitar, the 1510 will be dandy.)

While you "could" rig a guitar preamp from a 1510, it looks like the input current hiss in 100K source will be OTOO 29uV. A TL072 will do <3uV total hiss. At 1/30th the cost.


LME49720 is the ADSL chip re-packaged as a hi-fi chip. It will deliver high outputs very-very clean. Again it has low hiss voltage but high hiss current, ~~24uV in 100K. (So it is odd they show a phono preamp.... chip-makers often post dubious applications, specially for audio.) It is VERY fast so liable to oscillate in careless layout. It also has WAY too many graphs in its data-sheet. And Figs 112-129 are stolen directly form the 20++ year old LM chips that emulate a 5532.


LM4780 has way too many pins in way too little space, and way too many Watts in too little space. This is not a cobble-up build. It would be most expedient to look at the eBay offers for LM4780 with PCB and heatsink all in one kit, much cheaper than you can alacart the parts from Mouser.


> Real curious if I am picking good IC choices

These are all good parts... in another world. I'd do a whole PA system with 1510 to accept the mikes, 49720 to buffer board outputs (but something cheaper for EQ and mixing), and maybe the Overture series for small power output (but again, you can buy whole amps at Banjo World or pawn shop cheaper than you can buy the parts to DIY).

[R.G.]

Then there's the LM3886... oh, wait. That's what we were talking about. 

There is a large class of LM3886 applications ready to go. Here's an interesting one:
http://www.ebay.com/itm/DIY-AMP-Board-LM3886-3-150W-Parallel-Mono-Amplifier-Board-PCB-/360572904360?pt=US_Amplifier_Parts_Components&hash=item53f3d1e3a8
Three times LM3886 in parallel, on a completed PCB. Add one of these:
http://www.ebay.com/itm/3-x-5-75-x-1-Heat-Sink-Heatsink-3ea-TO-3-Transistors-Audio-Amp-Power-Supply-/301147367499?pt=LH_DefaultDomain_0&hash=item461dc8284b
and one of the many PCBs or preassembled power supplies for the LM3886 amps, and one of the several toroidal or E-I power transformers there with 24-0-24 outputs at about 200VA and you start having an amplifier

... er, that is, once you have a box to put it in, and the (deadly) AC wiring done.

[Brymus]

Thank You again Paul!
So while these are good ICs,it seems a better choice for guitar is still the LM3886 with NE5532's/TL072's for the pre amp.

Yeah getting a PCB of the net is probably the way to go for the LM4780,I plan to hold onto it until I get enough pulled parts to build it.

For my LM3886 ICs I still have left,
I have a couple of recycled enclosures,the heat sinks,RCA jacks,some pulled ALPs pots from Japan,and some new toroid trannies and 68000uf caps from Apex.
Along with a LARGE selection of metal oxide and flame proof resistors,regulators,and other recycled odds and ends.

Recycling used stuff is the only way I can afford this hobby plus it's "green" too.

Yeah RG ,the PCBs for LM3886 amps are cheap and plentiful so I will just do another mono build for guitar,and use two for my Home stereo.
Chips amps has a complete dual mono kit with everything but the tranny,heatsink and enclosure for 90$.
A blank amp + PS PCB can be had for less than 20$