Better than LM386 on batteries?

Hello!

I intend to build a stereo headphone mixer/amp type device for mixing bass guitar signal and the output of an mp3 or cd player. The preamp will be a couple of TL082s or similar dual opamps (plus various stereo pots and filter circuits, etc), and for the power section my first pick was going to be a pair of LM386s. I was going to run it at 18V for the clean headroom, and I was going to leave the gain set at 20 instead of

200 (pins 1 and 8 not connected).

IIRC, even in this state, the 386 is actually overkill for headphone operation, and it tends to consume a lot of power. I would prefer this device to be battery powered (so I can walk around with it wirelessly). Are there any newer, more efficient, or lower-powered-but-adequate-for-headphones type of chipamps that anyone could recommend?

Or is battery life just the price you pay when you want to physically move stuff with electricity?

Thanks!

-phaeton

Reply to
phaeton
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How loud do you want it to go ?

You can drive headphones from an op-amp output (typically via 100-150 ohms) if you don't need deafening volume.

I wouldn't suggest a TL082 for that stage btw, a 5532 would be a better choice.

Graham

Reply to
Eeyore

TDA7053 for a battery powered headphone amp;

NJM4580 or NJM4560 give more power if you have +/- 12 or 15V. You can also use the two sections of a TL072 for each channel (FidoCAD,

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:

[FIDOCAD ] LI 65 70 65 55 LI 65 55 90 55 MC 95 75 0 0 080 LI 90 75 95 75 LI 65 80 65 90 LI 65 90 90 90 LI 90 90 90 75 SA 90 75 LI 110 75 105 75 MC 95 35 0 0 080 LI 90 55 90 35 SA 90 35 LI 90 35 95 35 LI 110 40 110 75 LI 105 35 110 35 LI 110 40 110 35 SA 65 30 SA 65 40 LI 110 55 125 55 LI 125 55 125 60 MC 125 80 0 0 045 LI 125 75 125 80 SA 125 75 SA 125 65 LI 125 60 125 65 TY 20 30 5 3 0 0 0 * OP AMP inputs TY 130 65 5 3 0 0 0 * Headphone SA 110 55 TY 70 45 5 3 0 0 0 * TL072 MC 65 70 0 0 580 TY 75 70 5 3 0 0 0 * b MC 65 30 0 0 580 TY 75 30 5 3 0 0 0 * a TY 90 25 4 2 0 0 0 * 100 or 150 Ohm TY 90 65 4 2 0 0 0 * 100 or 150 Ohm

Gianluca

Reply to
LAB
Reply to
Brendan Gillatt

Yes, charge pump is very noisy. For audio I use NE555 / push pull

2SB1166+2SD1723 / a little toroidal transformer / fast diodes @120kHz... No Noise!
Reply to
LAB

In message , Eeyore writes

You can drive headphones from an op-amp *and* have deafening volume if you really want! Think LM48 and L165B plus any number of newer devices.

--
Clint Sharp
Reply to
Clint Sharp

Google for "CMOY headphone amp" That should get you one such example. I've actually built a CMOY,not bad at all,for such a simple amp. It might have troubles driving low impedance 'phones to insanely high volumes,but it doesn't have any problem driving my 32ohm Panasonic's to ear-splitting levels. (well above any 'normal' listening level!). But I'm using +/- 9V rails,delivered by two small DC-DC converters. (salvaged from old 10meg Ethernet cards.)

Reply to
PhattyMo

Where do yoiu get the little toroidal transformer ?

Graham

Reply to
Eeyore

I salvage switching components everytime i get broken PSU's. I measured inductance of a few turns and chosen the core, only the core. Diameter is about 16mm. Primary is 24 turns 0.7mm, secondary is 80 turns 0.4mm, then I get +/-15Vcc rectifing + and - separatly. Primary L is about 120uH, frequency is 120kHz.

There is NO feedback. I thought: when I connect a transformer to 240Vac I rectifier the output, nothing else. Let's do the same... Negative feedback introduces low frequency (audio) noise due to the correction delay. If I have no feedback, I can't have noise before the switching frequency, that is

120kHz.

Gianluca

Reply to
LAB

Thanks everyone! Hopefully this long holiday weekend will afford me some time to breadboard up some bridged opamps. I presume that they'll automagically run like a Class AB. Special thanks to LAB for the link to FidoCAD. Excellent program! It's the stripped-down no- nonsense SPICE I've been looking for.

Graham, are you unrecommending the TL082 for the headphone driver, or just the whole circuit in general? And, why?

Also, *could* opamps drive a typical 4 or 8 ohm speaker without blowing up?

I had looked at the CMOY once a couple years before, and forgotten about it until PhattyMo just mentioned it. I forget why I didn't build it then, maybe because (at the time) I thought the opamps it lists are "special" somehow and they aren't carried by my fave distributor, or something. Maybe I should just try it out with the op amps I have.

Thanks again!

-phaeton

Reply to
phaeton

Not the TL082 since its current drive isn't that good but a 5532 or

4560/4580 op-amp can drive headphones quite effectively if you use a 100 ohm series resistor.

Because the LM386 has rubbish audio performance ! It's real dog of a chip.

They won't 'blow-up' because they have internal current limiting. They would however be entirely unsuitable as speaker drivers as they can only deliver some 30mA or so.

His choice of op-amp is somewhat esoteric. You certainly don't need the OPA2132. Try what you have but the TL07/8x series isn't a good choice in this instance.

Graham

Reply to
Eeyore
Reply to
Brendan Gillatt

It has insanely low THD figures (0.00008%). Somewhat better than the LM386's

0.1% or so.

It's only +/- 40mA actually. A mere 2mA better than a 5532.

Don't forget the 100 ohm series resistor.

Graham

Reply to
Eeyore
Reply to
Brendan Gillatt

A 3 hour practice session on the guitar or bass probably should be followed by a break anyways.

That said.....Oh how i pine for the days when we will have small, safe, and adjustable nuclear power cells that will put out a constant amount of power and last forever. That may be lofty, but i sure hope that some huge revolution in battery technology is within the decade.

For this device, I was probably going to use rechargeables. Or just plug it in and deal with the lack of mobility. I even mused taking apart an old sony Discman, identifying the necessary circuit bits, and kitbashing my circuit and the Discman all into the same housing with a single power supply, but I guess I'm not that ambitious.

The Burr-Brown chips are significantly overspec'd for my application, at least as far as the THD figures are. Especially since I'm kinda sorta planning a distortion circuit for the instrument input anyways. Ideally, it would have that and some sort of mid-hump tone control, but the more I think about it, the more features I want to add, and I tend to overcomplicate everything I do. I've been trying to practice the K.I.S.S. philosophy. Just go back to the original plan of 3 simple audio channels each with their own separate volume and pan control. In any event, I've got 3 RC5532s in my parts collection. I'll still have to use TL082s or some other opamp for the rest.

Thanks!

-phaeton

Reply to
phaeton
Reply to
Brendan Gillatt

Excellent circuit! Looks like it will be a lot of fun.

Say, btw... is there anything else I should be using to search for

100K stereo pots w/ audio taper? I'm completely striking out at the following places:

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with permutations of "stereo potentiometer" and "dual ganged pot" and "stereo volume pot" and such. Even rifling through the hits of "potentiometer" doesn't seem to show them. Radioshack has it, but they're a last resort.

I could swear I bought one online once before, and I would expect these to be a fairly standard item. Did someone cut down the last stereo pot tree?

Reply to
phaeton

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Reply to
Michael A. Terrell

TL082s will be good for the high input impedance input stage you should have to avoid destroying the 'tone' of your guitar. Mind you it's less of an issue with bass guitars.

Graham

Reply to
Eeyore

Thanks for the links. Mouser's website search feature is pants, but I forgot that the PDF catalogue is the way to go.

Btw, in that FidoCAD example, (I could provide a jpg if necessary), I can hook up the top opamp like a normal inverting or non-inverting gain stage, right?

Thx

-Phaeton

Reply to
phaeton

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