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

phaeton wrote:

> 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.

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

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,
http://www.enetsystems.com/~lorenzo/fidocad_win.asp) :

[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

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phaeton wrote:
> 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

Various places do specially designed headphone power amplifiers. National
do a nice looking headphone amp: LM4882. I haven't tried it out but the
specs look great. Furthermore, you can run it off 5volts if you want - no
need for a noisy charge pump.

- --
Brendan Gillatt
brendan {at} brendangillatt {dot} co {dot} uk
http://www.brendangillatt.co.uk
PGP Key: http://pgp.mit.edu:11371/pks/lookup?op= ... 0xBACD7433
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>> you can run it off 5volts if you want - no need for a noisy charge pump.

Yes, charge pump is very noisy. For audio I use NE555 / push pull
2SB1166+2SD1723 / a little toroidal transformer / fast diodes @120kHz... No
Noise!

Eeyore wrote:
>
> phaeton wrote:
>
>> 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.
>
> 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.

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.)


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

In message <476775AB.D3CA826F@hotmail.com>, Eeyore
<rabbitsfriendsandrelations@hotmail.com> writes
>You can drive headphones from an op-amp output (typically via 100-150
>ohms) if you don't need deafening volume.
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.
>
>I wouldn't suggest a TL082 for that stage btw, a 5532 would be a better
>choice.
>
>Graham
>

--
Clint Sharp

LAB wrote:

> >> you can run it off 5volts if you want - no need for a noisy charge pump.
>
> Yes, charge pump is very noisy. For audio I use NE555 / push pull
> 2SB1166+2SD1723 / a little toroidal transformer / fast diodes @120kHz... No
> Noise!

Where do yoiu get the little toroidal transformer ?

Graham

> Yes, charge pump is very noisy. For audio I use NE555 / push pull
> 2SB1166+2SD1723 / a little toroidal transformer / fast diodes @120kHz...
> No Noise!

>> Where do you get the little toroidal transformer ?

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

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

phaeton wrote:

> 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,

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.


> or just the whole circuit in general? And, why?

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



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

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.


> 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.

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

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phaeton wrote:
> 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.

Oh they are special - they're spectacularly expensive ;]
The Burr-Brown parts have fantastic specs, however, if you need it.

Furthermore, if your distributor doesn't carry them you can always
request a couple of samples. From my experience TI seem pretty good to
their customers, samples included.

- From my memory of building a CMOY, I recall that the specs for the part
he chose have an enormous current handling capability - ideal for driving
speakers/headphones without clipping.

Saying that, most regular op-amps will drive earphones to a decent level.

If you are going to build a CMOY don't don't don't use a 9v battery - the
life through a pair of 64ohm 'phones is, perhaps, 3 hours! Use some good
NiMH AAAs or consider looking at lithium polymer batteries.

- --
Brendan Gillatt
brendan {at} brendangillatt {dot} co {dot} uk
http://www.brendangillatt.co.uk
PGP Key: http://pgp.mit.edu:11371/pks/lookup?op= ... 0xBACD7433
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Brendan Gillatt wrote:

> phaeton wrote:
>
> > 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.
>
> Oh they are special - they're spectacularly expensive ;]
> The Burr-Brown parts have fantastic specs, however, if you need it.

It has insanely low THD figures (0.00008%). Somewhat better than the LM386's
0.1% or so.


> Furthermore, if your distributor doesn't carry them you can always
> request a couple of samples. From my experience TI seem pretty good to
> their customers, samples included.
>
> - From my memory of building a CMOY, I recall that the specs for the part
> he chose have an enormous current handling capability - ideal for driving
> speakers/headphones without clipping.

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


> Saying that, most regular op-amps will drive earphones to a decent level.

Don't forget the 100 ohm series resistor.

Graham

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Eeyore wrote:
>> - From my memory of building a CMOY, I recall that the specs for the part
>> he chose have an enormous current handling capability - ideal for driving
>> speakers/headphones without clipping.
>
> It's only +/- 40mA actually. A mere 2mA better than a 5532.

My bad memory then! I thought it was in the range of 150-200mA.


- --
Brendan Gillatt
brendan {at} brendangillatt {dot} co {dot} uk
http://www.brendangillatt.co.uk
PGP Key: http://pgp.mit.edu:11371/pks/lookup?op= ... 0xBACD7433
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>
> If you are going to build a CMOY don't don't don't use a 9v battery - the
> life through a pair of 64ohm 'phones is, perhaps, 3 hours! Use some good
> NiMH AAAs or consider looking at lithium polymer batteries.
>

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

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phaeton wrote:
> 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

While you're building effects might I point you to a very neat little
compressor:
http://machines.hyperreal.org/categorie ... compressor

Works great and definitely goes along with the KISS mindset =]

- --
Brendan Gillatt
brendan {at} brendangillatt {dot} co {dot} uk
http://www.brendangillatt.co.uk
PGP Key: http://pgp.mit.edu:11371/pks/lookup?op= ... 0xBACD7433
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>
> While you're building effects might I point you to a very neat little
> compressor:http://machines.hyperreal.org/categories/DIY/info/compressor
>
> Works great and definitely goes along with the KISS mindset =]
>

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:

http://www.jameco.com
http://www.mouser.com
http://www.digikey.com

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?

phaeton wrote:
>
> >
> > While you're building effects might I point you to a very neat little
> > compressor:http://machines.hyperreal.org/categories/DIY/info/compressor
> >
> > Works great and definitely goes along with the KISS mindset =]
> >
>
> 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:
>
> http://www.jameco.com
> http://www.mouser.com


http://www.mouser.com/catalog/632/574.PDF
http://www.mouser.com/catalog/632/575.PDF
http://www.mouser.com/catalog/632/576.PDF
http://www.mouser.com/catalog/632/578.PDF


> http://www.digikey.com
>
> 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?


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

phaeton wrote:

> >
> > If you are going to build a CMOY don't don't don't use a 9v battery - the
> > life through a pair of 64ohm 'phones is, perhaps, 3 hours! Use some good
> > NiMH AAAs or consider looking at lithium polymer batteries.
> >
>
> 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.

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

> --
> Service to my country? Been there, Done that, and I've got my DD214 to
> prove it.
> Member of DAV #85.
>
> Michael A. Terrell
> Central Florida


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