Good Headphone Amp

[mateus]

Hello there guys! Hope everyone doing fine during these harsh strange times we're all living in.
1st of all thanks everyone for doing this and sharing all this amazing knowledge summed in here, I can't stress enough how much I rely on this group for the many many projects I've came across all over the past few years!

I'm a small record producer from south of Brazil and for years I have been struggling finding a way of listening my mixes tru my chosen consumer headphones. I do own a decent Pro Tools rig but I just can't stand listening anything using the headphone output of my old Control 24 and I can't stand bouncing and sending the bounces to the cloud to be able to hear 'em using my old iPhone as my headphone amp. Taxes and dollars being to expensive makes it just impossible for me buying a decent headphone amp so it's time to build something again!

What should I build?

Thanks all in advance!

 

[Bo Deadly]

Do you just want to have a nice headphone out or do you want to build something?

You definitely DON'T want to use an iPhone. The iPhone will almost certainly boost bass and do other stuff to skew the mix. If you want to hear things like you mixed them, then you need something with a really flat frequency response.

If you just want a good headphone out with a flat response, I would get a small monitor controller. For example, I have the Drawmer CMC2 and I use it a LOT. I have two sets of speakers and I route I/P2 and output B through my patchbay normalled to my secondary speakers. It's got a headphone out and 3.5mm stereo aux in. It's basically the minimum essential I/O with the right buttons to source and output in the usual ways.

If you really just want to build something, then I would just make a little PCB with two circuits like this (one for L and one for R):

but with RC4580 because it's got the right amount of kick and output swing. I would use the SOIC8 package with 4 square cm around each IC with ground plane above and below stitched together with vias as a heat sink. Put a PCB mount 3.5mm jack on the edge with a 1K pot for a level control w/ wiper to Vin. Make R1 and R2 like 1K and 2.2K respectively which I think is ~10dB boost so that the source signal can be well below output. That should make ~150mW which would be painfully loud but it probably wouldn't hurt your ears permanently if you had an accident.

 

[abbey road d enfer]

What should I build?

There are litterally thousands of HP amps schemos on the internet, some are crappy, some are overengineered, and most are good. The reference to your i-phone shows that you are used to a system where the inherent weaknesses of in-ear transducers are electronically compensated.
You need to start with the headphones themselves. In-ear or circumaural, open or closed-back? Are there documents that support the flatness of frequency response.
I believe that, if you want to build a HP amp that can suit most HP's, you need to include some form of adjustable EQ, because most HP's are simply not flat.
Regarding the amp itself, I would use one of the many power amp chips available, like the venerable LM380 and 386, the NJM2113, or the mighty TDA2050, that is capable of 30W output, but also operates brilliantly at much lower load. You can buy ready-made modules at dirt cheap prices. Actually, the 2030 or 2040 would work as well, but the price difference does not justify it.
https://fr.aliexpress.com/item/32814339462.html?src=google&albch=shopping&acnt=248-630-5778&isdl=y&slnk=&plac=&mtctp=&albbt=Gploogle_7_shopping&aff_atform=google&aff_short_key=UneMJZVf&gclsrc=aw.ds&&albagn=888888&&ds_e_adid=438856512841&ds_e_matchtype=&ds_e_device=c&ds_e_network=u&ds_e_product_group_id=743612850874&ds_e_product_id=fr32814339462&ds_e_product_merchant_id=107694425&ds_e_product_country=FR&ds_e_product_language=fr&ds_e_product_channel=online&ds_e_product_store_id=&ds_url_v=2&ds_dest_url=https://fr.aliexpress.com/item/32814339462.html?&albcp=10191220517&albag=107473525088&gclid=Cj0KCQjwufn8BRCwARIsAKzP697G-hpvEeCWrHbBopAa570Urb9oGvPqhXblut1R3FTsml46g__gxjkaAtN9EALw_wcB

 

[gyraf]

My to-go headphone amp is this, we use it in the studios as well as for demos at tradeshows: http://www.gyraf.dk/gy_pd/hpamp/HP-Amp.pdf

/Jakob E.

 

[abbey road d enfer]

My to-go headphone amp is this, we use it in the studios as well as for demos at tradeshows: http://www.gyraf.dk/gy_pd/hpamp/HP-Amp.pdf

/Jakob E.

It basically comes out directly from an opamp cookbook. The magic in it is running it a 20+ mA quiescent current.

 

[gyraf]

..yes, absolutely no magic about it, but has turned out very usable for many purposes over the years..

/Jakob E.

 

[peterc]

Agreed Jakob, very good design.

 

[JohnRoberts]

..yes, absolutely no magic about it, but has turned out very usable for many purposes over the years..

/Jakob E.

That looks like serious class A bias. Of course it will sound good, while giving up a couple volts of signal swing.
===

A question for the OP when you say "consumer" headphones that covers a lot of ground. I won't bore you with details about my last HP amp design (last century) but to be all things to all people you must drive headphones ranging from 4 ohm to 600 ohm impedance... Most built-in HP amps use significant build out resistors (10 to tens of ohms) to handle that wide range of loads. Too much build out resistance can compromise accuracy and response with difficult loads. Of course too low or no build out resistance can stress the design when driving low Z cans. (My old HP amp design would drive speakers and I had to power limit the wall wart to avoid popping the thermal fuse). 

There are many good designs out there, and this general topic has been well discussed right here. Good luck. Perhaps start with understanding more about the specific headphones you want to drive, and what you don't like about your current rig.

JR

 

[mateus]

Thanks for the replies so far guys!!
Loved the Gyraf amp! Like all things Gyraf!

To be honest I have some good phones here:
AKG K240 - 55 ohms - 200mW
AKG K702 - 62 ohms - 200mW
Beyer DT770 Pro - 80 ohms - 100mW

And the iPhone headphones, no idea it's specs tho.

The thing is, I love using this phone, I listen to music with it and i'm very used detecting a few last details faster when finishing a mix with it, but as I said, it's a pain in the ass having to bounce, upload, send to phone and play, since I can't just connect the headphone to my Control 24 phone jack, no headphones BTW, they all sounds terrible in that jack, so my idea is building a box that I can simply send a stereo signal level to it, straight from my Avid Analog HD I/O, and plug the phone in this box, listen, make the adjusts in the fly and voilá, bounce! =)

 

[Gold]

If you want to use your iPhone headphone amp I’d get a USB 2.0 compliant usb interface and run a DAW app. That would let you just listen through the iPhone.

 

[abbey road d enfer]

Has anyone measured the frequency response of an iPhone? I would bet it's seriously doctored...

 

[john12ax7]

My to-go headphone amp is this, we use it in the studios as well as for demos at tradeshows: http://www.gyraf.dk/gy_pd/hpamp/HP-Amp.pdf

/Jakob E.

Is it not necessary to AC couple the output?

 

[gyraf]

..nope..

 

[Gold]

I have an iPhone 7 and the headphone out has flat frequency response. I’ve sent tones through the output and measured.

 

[JohnRoberts]

Thanks for the replies so far guys!!
Loved the Gyraf amp! Like all things Gyraf!

To be honest I have some good phones here:
AKG K240 - 55 ohms - 200mW
AKG K702 - 62 ohms - 200mW
Beyer DT770 Pro - 80 ohms - 100mW

That's useful data...  That calculates to between 2-3V AC average, and tens of mA so not heavy lifting. Since music has a crest factor including peaks several times average target larger clean signal swing, but still not heavy lifting.

JR

And the iPhone headphones, no idea it's specs tho.

The thing is, I love using this phone, I listen to music with it and i'm very used detecting a few last details faster when finishing a mix with it, but as I said, it's a pain in the ass having to bounce, upload, send to phone and play, since I can't just connect the headphone to my Control 24 phone jack, no headphones BTW, they all sounds terrible in that jack, so my idea is building a box that I can simply send a stereo signal level to it, straight from my Avid Analog HD I/O, and plug the phone in this box, listen, make the adjusts in the fly and voilá, bounce! =)

 

[Gold]

Apple takes its audio seriously. They are always recruiting at AES shows. Every time I've seen tests done on the audio hardware in iOS devices it has been quite good.

 

[Bo Deadly]

I just got a new iPhone about 2 weeks ago and it definitely boosts the bass big time. I don't know if it's the iPhone, the new DAC-in-cable or the earbuds or what but it's actually super annoying because there's no EQ control with the Amazon Music app. Only the iTunes app has EQ controls but even with "Bass reduce" enabled, it's still pretty tubby. Not good for listening to prog rock. I'm really disappointed about the lack of an analog out actually. Sometimes new tech is just not better. They're just trying to remove a port that most people don't care about. Plain and simple.

 

[Gold]

I just got a new iPhone about 2 weeks ago and it definitely boosts the bass big time. I don't know if it's the iPhone, the new DAC-in-cable or the earbuds or what but it's actually super annoying because there's no EQ control with the Amazon Music app. Only the iTunes app has EQ controls but even with "Bass reduce" enabled, it's still pretty tubby. Not good for listening to prog rock. I'm really disappointed about the lack of an analog out actually. Sometimes new tech is just not better. They're just trying to remove a port that most people don't care about. Plain and simple.

There are a lot of variables in there. I'd bet on the ear buds.

 

[Bo Deadly]

Then I want to know who makes headphones with the lightning connector and a deliberately very flat frequency response because I need some.

 

[Gold]

Then I want to know who makes headphones with the lightning connector and a deliberately very flat frequency response because I need some.

Frequency response in headphones is somewhat subjective because of the physical differences in humans ear canals. The best you can hope for is flat frequency response out of the DA. Then pick headphones that you like.