Cheap headphone amp (low impedance)

[BeerBear]

I'm looking for a cheap amp to drive low impedance (32 Ohm) headphones. So I'd like to have low output impedance on the amp.
I just need analog line in and headphone out. No DAC and no battery.
A potentiometer is not even strictly necessary. Ideally it would be powered via USB, but I can live with an AC adapter too.

Does anyone know how these perform:
"AU-10X NE5532"
"Classic 47"
?

I'd be willing to spend more too, but then I'd expect some nice features like a "digital" pot (for the perfect LR balance).

 

[solderdude]

The used opamps are not suited to drive low impedance loads and the used coupling cap values are too small for 32 Ohm which means you may get bass roll-off.

The do make sound and it won't be bad but is not upto standards.
Easy to modify though (within limits)

 

[bobbooo]

I'm looking for a cheap amp to drive low impedance (32 Ohm) headphones. So I'd like to have low output impedance on the amp.
I just need analog line in and headphone out. No DAC and no battery.
A potentiometer is not even strictly necessary. Ideally it would be powered via USB, but I can live with an AC adapter too.

Does anyone know how these perform:
"AU-10X NE5532"
"Classic 47"
?

I'd be willing to spend more too, but then I'd expect some nice features like a "digital" pot (for the perfect LR balance).

What headphones do you have?

 

[BeerBear]

@solderdude: Is this for both of those amps or just one of them?
There are slightly different versions of that DIY "47" amp on Ali, but I can't find much info about them.

@bobbooo: Eartools RP-21 (for now).

 

[solderdude]

Both amps use the same opamps and low value output caps.

Different opamps (with higher current outputs) and increased value capacitors would make sense. The problem is getting higher value capacitors to fit on the PCB. When you plan to make it in a bigger enclosure this should not be much of a problem.

 

[AnalogSteph]

@bobbooo: Eartools RP-21 (for now).

Specs are 32 ohm, 100 dB / 1 mW (so approx 115 dB SPL / 1 Vrms). Apparently had a penchant for cracking hinges (reminds me of certain Sony MDR-V700 / Beyer DT440 issues).

The "Classic 47" is basically the old apheared-47 circuit (an old favorite for driving Grados, so should do a decent job with yours as well), not sure why this one seems to be an all-single-supply job with AC coupling though. You'd think that with a floating power supply, they'd take advantage of being able to DC-couple the output.

Schematic pinched from this listing:

A few values seem to differ (mostly the rail splitter resistors) but it should give you an idea.

Not sure I would trust the supplied NE5532s much (they may or may not be fake), or the electrolytics for the matter. 100 uF on the output also is way too small, 220-330 µF is about the bare minimum for 32 ohms. While squeezing in some bigger caps almost always works somehow, modifying the board for split supply operation (à la cMoy) would not be trivial, unfortunately.

I would keep my eyes open for a $25-30-ish battery-operated portable amp that allows USB charging in operation. Do use a known solid USB charger, some of the dodgy cheapies have a rather tense relationship with electrical safety or EMI.

 

[JohnYang1997]

Just get a meizu dongle....

What exactly do you want to achieve?
Just to play music for your headphones or you want some DIY and learn a thing or two?
Those core circuits can give very good performance if modified to death. And it's simply better to just design a better circuit from ground up. @Bamboszek has a good open source amp with really good performance.

 

[jasonhanjk]

DIY can be real cheap. Single 9V supply for a cmoy to work.
If you want something with 5V supply, you can look into HT97220.

 

[BeerBear]

@solderdude and @AnalogSteph: Thanks for the info. I can solder things somewhat, but I don't have much knowledge about electronics otherwise. So I'd prefer something assembled or at least something with step by step instructions. And I'd rather not have a battery for something that is always plugged in.

@JohnYang1997: I'm looking to use the amp with my soundcard, because I can't find one that has all the features I need plus a good headphone amp. After a lot of searching I found just these two: Babyface Pro and Motu M2. The first one is too expensive and the second one has reliability issues.

@jasonhanjk: Yeah 5V would be ideal, it it means I could power it from a USB port.

 

[JohnYang1997]

@solderdude and @AnalogSteph: Thanks for the info. I can solder things somewhat, but I don't have much knowledge about electronics otherwise. So I'd prefer something assembled or at least something with step by step instructions. And I'd rather not have a battery for something that is always plugged in.

@JohnYang1997: I'm looking to use the amp with my soundcard, because I can't find one that has all the features I need plus a good headphone amp. After a lot of searching I found just these two: Babyface Pro and Motu M2. The first one is too expensive and the second one has reliability issues.

@jasonhanjk: Yeah 5V would be ideal, it it means I could power it from a USB port.

Since your budget is not so tight and you are not really looking into starting DIY. Why not just grab an Atom or an L30. The meizu pro does work also with built in DAC.

For DAC D10s does the job for cheap. You probably can still get the old D10 for cheaper.

What function do you need exactly? Do you need ADC? If that's the case M2 is indeed pretty good option. Or do you just do mixing and stuff? This case you don't need an audio interface just get a decent usb dac and get the XMOS driver. Back to audio interface options, focusrite scarlett 2i2, 2i4, clarett 2pre all work, or you can get a second hand focusrite forte for pretty cheap. M4 is probably more reliable then M2?

 

[BeerBear]

I need a couple of ins and outs, multi-client ASIO and a decent low impedance headphone amp. This combo is not that common, especially the headphone amp part, which is still an afterthought in large parts of the industry. Hence, this thread.

And I don't want to spend more than $30 for just a headphone amp, it feels wrong paying that much for something that is relatively cheap to produce. I get it, though, it's a niche market that's why the prices are what they are. And even that $100 Atom you mentioned isn't that great, with its an analog pot and 0.6dB channel balance.

 

[JohnYang1997]

I need a couple of ins and outs, multi-client ASIO and a decent low impedance headphone amp. This combo is not that common, especially the headphone amp part, which is still an afterthought in large parts of the industry. Hence, this thread.

And I don't want to spend more than $30 for just a headphone amp, it feels wrong paying that much for something that is relatively cheap to produce. I get it, though, it's a niche market that's why the prices are what they are. And even that $100 Atom you mentioned isn't that great, with its an analog pot and 0.6dB channel balance.

Actually. The issue here is the expectations. You want to pay 30 dollars for something that literally cost that much (or more) to produce. Sure the proposed 47 amp is much cheaper but at what cost... (you lose 40dB or more performance just in case you don't know)
And actually you don't need low impedance headphone amplifier. You can live with 5 to 10 output impedance without any issue. Just get a focusrite 2i2. Done.

 

[maverickronin]

And even that $100 Atom you mentioned isn't that great, with its an analog pot and 0.6dB channel balance.

Pretty much anything with a pot is going to be a crapshoot.

 

[jasonhanjk]

Less than $3.
https://www.aliexpress.com/i/32958965813.html

THD+N for 32 ohm is 0.0035%.

For single-ended, you may need to short the audio input gnd to the board's gnd.
If the USB supply and audio source is from the same ground (your PC sound card for example), then do not short additional ground on the PCBA.

 

[JohnYang1997]

Less than $3.
https://www.aliexpress.com/i/32958965813.html

THD+N for 32 ohm is 0.0035%.
For single-ended, you may need to short the audio input gnd to the board's gnd.

Right. Why not get an opa1622 opamp in DIP and claim it's 0.00015% 32ohm.

 

[jasonhanjk]

Right. Why not get an opa1622 opamp in DIP and claim it's 0.00015% 32ohm.

OPA1622 IC only available in VSON. There's no IC in DIP.

 

[JohnYang1997]

OPA1622 IC only available in VSON. There's no IC in DIP.

I meant those with converter board on aliexpress and ebay. And it's obviously sarcasm. If one is gonna touch things like that he would be better off getting a better board like O2. Or 1622 EVM board from TI. Hundreds times better.
https://www.mouser.com/ProductDetail/Texas-Instruments/OPA1622EVM?qs=vcbl%2BK4rRlcswYI1Ei3IKw==

 

[jasonhanjk]

I meant those with converter board on aliexpress and ebay. And it's obviously sarcasm. If one is gonna touch things like that he would be better off getting a better board like O2. Or 1622 EVM board from TI.

Well, he wants something cheap and can run on a single 5V supply.
OPA1622 EVM is $30 exclude shipping, also it requires 2 DC adapter.

By the way, we still don't know OP's source. High end amp won't be 100x better without a very good source.

 

[JohnYang1997]

Well, he wants something cheap and can run on a single 5V supply.
OPA1622 EVM is $30 exclude shipping, also it requires 2 DC adapter.

By the way, we still don't know OP's source. High end amp won't be 100x better without a very good source.

That leads to my other reply previously. Spending 100+ dollars on headphone amp anything but unreasonable. A LOT goes into the design.

 

[maverickronin]

That leads to my other reply previously. Spending 100+ dollars on headphone amp anything but unreasonable. A LOT goes into the design.

You'd think that more of these audio interfaces could at least use a JRC 4556 as their output stage and get lower output impedance.

It doesn't seem like the OP is expecting power, noise, or distortion to complete with L30 or something.