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Best Mini Amp for Headphones? In Guitar?

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dudemcfly

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Hello everyone, I've recently taken on a new project, I'm building myself a travel guitar. Amongst the features I want to add, I want to install a mini amp in it, like a Ruby or Little Gem, solely for the purpose of using with headphones while away from home. I will have the output from the guitar go to two different outputs, the usual output jack, and then the amp, which will have its own jack. My question is, will that work? And which of the mini amps will work/sound best with headphones?

I would normally lean towards a Ruby, because I remember Audioguru once said the Little Gem wouldn't have enough input for guitar pickups. But since it's just headphones and not a speaker, does that mean I can get away with less? Or will I still lose something? I'm also considering that I have to put this in the already small guitar, so the smaller the better. How would you do it? Any help appreciated! Thanks.
 
But if you want to make your own try this chip and get a design and sample from TI

TPA3144D2PWPR
6-W Inductor Free Stereo (BTL) Class-D Audio Amplifier with Ultra Low EMI and AGL
TPA3144D2 is not only fully protected against shorts and overload, the SpeakerGuard speaker protection circuitry includes an adjustable Automatic Gain Limit (AGL), an adjustable power limiter and a DC detection circuit for protection of the connected speakers. The AGL allows adjustment of the maximum output voltage without signal clipping for enhanced speaker protection and audio quality. The DC detect and Pin-to-Pin, Pin-to-Ground and Pin-to-Power Short Circuit protection circuit protect the speakers from output DC and pin shorts caused in production. The outputs are also fully protected against shorts to GND, PVCC, and output-to-output. The short-circuit protection and thermal protection includes an auto recovery feature.

The TPA3144D2 can drive stereo speakers with as low as 4-Ω impedance. The high efficiency of the TPA3144D2, 90% with 8-Ω load, eliminates the need for an external heat sink, and TPA3144D2 will be able to output full power on a 2-layer PCB.

View datasheet
View product folder

<0.05% THD+N at 1 W/4 Ω/1 kHz

• <65-µV A-wgt Output Noise
• Wide Supply Voltage Range Allows Operation
protection of the connected speakers. The AGL an adjustable Automatic Gain Limit (AGL),
- SpeakerGuard™ speaker protection circuitry allows adjustment of the maximum output voltage - adjustable power limiter and a DC detection circuit without signal clipping for enhanced speaker includes from 4.5 V to 14.4 V

I think the soft SpeakerGuard looks like it should sound like a Vacuum Tube Amp when limiting. TONY.
 
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6W into headphones will blow off your head! Headphones are loud when using 100mW. You do not need a stereo amp IC anyway, use a single mono amplifier.
The expensive amplifier "designed for musical instruments" does not say it will work with an guitar pickup.
The LM386 amplifier IC used in the Little Gem and Ruby amplifiers has no crossover distortion and sounds pretty good.
The "Little Gem" is missing the important high input impedance Jfet used on the "Ruby" so use a Ruby amplifier.

A small guitar might sound "small".
 
Not all headphones are 4 or 8 Ohms . In fact, Sony MDR-7506 Headphone are 63 Ohms 1W max.
Since the chip runs from as low as 4.5V, can only output 150mW rms into 63 Ohms, making this a good choice, unless you want micropower from a certain battery and certain headphone impedance.
This one is 20mA nom. idle
 
Thanks for your responses! I'm not worried about using any specific type of headphones. I just want to be able to use whatever headphones I have handy at the time and be able to adjust the volume with the pot as needed. I plan to route the electronics cavity big enough to fit the board, 9V and other pots/switch with the other electronics.

So then, can I do that? Or do I need to shield the circuit or something? Will the amp circuit pick up interference from the pickups? Or vice versa?
 
If it's not all shielded, interference from the pick-ups won't be your issue, but I would imagine you will know when the local taxi company has a car nearby :)
 
Thanks for your responses! I'm not worried about using any specific type of headphones. I just want to be able to use whatever headphones I have handy at the time and be able to adjust the volume with the pot as needed. I plan to route the electronics cavity big enough to fit the board, 9V and other pots/switch with the other electronics.

As suggested, use the Ruby - it's simple, easy, cheap, and does exactly what you're after.
 
Evidently, according to AG.
As I recall just old cheap headphones were 8 Ohm, where 32, 60 are more common.

I like ear buds from Skull Candy . I use these direct from guitar pickup with built in amp and EQ for my acoustic.
Whenever someone asks for the best, and limits the choices to 2 for whatever reasons, then AG's suggestion is good.

Guitars usually just have Pre-Amps inside with basic tone controls and volume. and pickup selector switches. Low noise high bandwidth IC's are needed for gain and power. Often this is a compromise.

common mode ferrite chokes will improve RF rejection of AM and short wave..
 
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My 8 ohm over-the-ears headphones were gone long ago.
My Kenwood on-the-ears headphones (came with a CD player) measure a resistance of 17 ohms.
I have many ear pods that measure resistances of 34 ohms.
 
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