0.3 watt 50 ohm speaker is looking for amp

Thread Starter

TillFly

Joined Oct 26, 2016
68
Hey,

i´m looking for an amp to drive a 0.3 watt 50 ohm speaker.

can i connect a 0.3 watt 50 ohm speaker to macbook pro 2021 audio out 3,5mm?

Best,
D
 

Audioguru again

Joined Oct 21, 2019
4,798
0.3W into 50 ohms is 3.9V RMS which is 11V peak-to-peak. An audio amplifier powered from 14V or 15V can do it.

A 50 ohms speaker usually sounds awful and is used for a gas station intercom.
The single transistor Instructable amplifier produces severe distortion and puts DC in the speaker to make it sound worse.
 

Thread Starter

TillFly

Joined Oct 26, 2016
68
0.3W into 50 ohms is 3.9V RMS which is 11V peak-to-peak. An audio amplifier powered from 14V or 15V can do it.

A 50 ohms speaker usually sounds awful and is used for a gas station intercom.
The single transistor Instructable amplifier produces severe distortion and puts DC in the speaker to make it sound worse.
unfortunately i cant change the speaker.
thanks for stating that the instructables is nothing good to follow!

i guess i should look for a AC amplifier because "AC amplifiers reject noise more easily, while DC amplifiers have better low-frequency response." ?

so something like this should work right ?
https://www.amazon.de/dp/B0B353WNZ6...jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==
 

ericgibbs

Joined Jan 29, 2010
15,726
hi T,
Your
ca. 3,872 volt and from rms to peak is 11? ,
should read as ca. 3,872 volt and from rms to peak to peak is 11v?

Vpeak = Vrms * 1.414
So, 3.872Vrms* 1.414 = 5.47Vpeak.
OK.?
E
 

Audioguru again

Joined Oct 21, 2019
4,798
All modern audio amplifiers are DC-coupled internally for good low frequency response then have input and output coupling capacitors to pass audio but block DC.

The Amazon amplifier produces 100 times too much power and uses a TDA2030 IC that is not made anymore.
It passes only low frequencies that your little speaker cannot produce.

Instructables usually have many errors. This amplifier is horrible, here is its simulation:
 

Attachments

Thread Starter

TillFly

Joined Oct 26, 2016
68
Depending on the transistor, It'll wire up in a slightly different way correctly.
I have a irf540n transistor, to reach the 11 peak to peak voltage ... what circuit would you recommend me?
I also have some potentiometers eg.25 and 50 kohm. also some capacitors...
when I google for "irf540 audio amplifier 14v" there is no obvious result for my noob eyes :/

i´m also very thankful for any amazon link to a fitting ready-made amplifier :)
 

Thread Starter

TillFly

Joined Oct 26, 2016
68
i guess this amp is too low in power, is it?
"Maximum output power: 270mW (32 Ohm THD <1%)"
with the higher 50ohm speaker this amp wont hold up to the 270mW and wont reach 300mW or 500mW at peak right?

as I understood resulting power decreases with higher resistance. or does this amp compensate that?
so same power no matter what resistances?
 

Audioguru again

Joined Oct 21, 2019
4,798
The supply voltage for the headphones amplifier is too low to produce 0.3W into 50 ohms. It produces 0.27W into 32 ohms which is 2.94V RMS (8,3V p-p, probably bridged outputs). 2.94V squared/50 ohms= 0.173W.

Please provide a link to your 50 ohms speaker specs and its enclosure.
 

Thread Starter

TillFly

Joined Oct 26, 2016
68
The supply voltage for the headphones amplifier is too low to produce 0.3W into 50 ohms. It produces 0.27W into 32 ohms which is 2.94V RMS (8,3V p-p, probably bridged outputs). 2.94V squared/50 ohms= 0.173W.

Please provide a link to your 50 ohms speaker specs and its enclosure.
specs in the picture attached.
also from the speaker enclosure
 

Attachments

Thread Starter

TillFly

Joined Oct 26, 2016
68
The supply voltage for the headphones amplifier is too low to produce 0.3W into 50 ohms. It produces 0.27W into 32 ohms which is 2.94V RMS (8,3V p-p, probably bridged outputs). 2.94V squared/50 ohms= 0.173W.
I also ordered already a speaker yesterday
this one
https://www.amazon.de/dp/B07KR3RF4H/ref=pe_27091401_487027711_TE_SCE_dp_1?th=1

it states: "With up to 320 milliwatts of power (recommended from 16 to 150 ohm impedance)"
so i hoped maybe it keeps up the 320mW with 50 ohm^^
 

bertus

Joined Apr 5, 2008
21,940
Hello,

Did you see that the amplifier needs USB 1.0 or USB 2.0 input signals?
  • High quality USB DAC - can be used either via USB 1.0 or USB 2.0
  • Full computing power - decodes DSD256 and PCM with 32 bit and 384 kHz
It needs digital input signals to function.

Bertus
 

Thread Starter

TillFly

Joined Oct 26, 2016
68
Hello,

Did you see that the amplifier needs USB 1.0 or USB 2.0 input signals?
thats ok for my use case. i have to make and test some sounds for that speaker and just need to make sure that the amp drives the speaker properly and not kills it ^^

would it be fine in terms of levels? i still have the question as above :
"With up to 320 milliwatts of power (recommended from 16 to 150 ohm impedance)"
does it keeps up the 320mW with 50 ohm?
 

Thread Starter

TillFly

Joined Oct 26, 2016
68
The supply voltage for the headphones amplifier is too low to produce 0.3W into 50 ohms. It produces 0.27W into 32 ohms which is 2.94V RMS (8,3V p-p, probably bridged outputs). 2.94V squared/50 ohms= 0.173W.

Please provide a link to your 50 ohms speaker specs and its enclosure.
despite that i bought a speaker for testing i am interested in how to put it together with the correct components :)
how to proceed with the irf540 as a starting point?

appreciate your help alot!!
 

BobTPH

Joined Jun 5, 2013
5,248
thats ok for my use case. i have to make and test some sounds for that speaker and just need to make sure that the amp drives the speaker properly and not kills it ^^

would it be fine in terms of levels? i still have the question as above :
"With up to 320 milliwatts of power (recommended from 16 to 150 ohm impedance)"
does it keeps up the 320mW with 50 ohm?
Not likely. If it can produce 320mW into 32Ω it can produce 320 * 32 / 50 = 205 mW into your speaker.

Bob
 
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