Audiophile options for a HQ external USB DAC

If you're interested in something with advanced design, this Topping A-90 discrete sits at the opposite end of the spectrum to the simple quad op-amp design of the little canford amp I've got here. This is just to give an idea of how sophisticated headphone amps can get. You will pay a lot for it of course :). I have to say, this does look like a very nice amp.

www.audiosciencereview.com

Topping A90 Discrete (A90D) - Teardown and personal thoughts

I found not many teardowns with this model, especially with the output transistors uncovered and with surrounding close-ups, so I decided to purchase one for myself (second hand) to pair it with my D90 MQA then write an article here on ASR. Looks like taking the PCB out from the case if somehow...
www.audiosciencereview.com www.audiosciencereview.com
 
blackbird9 said:
If you're interested in something with advanced design, this Topping A-90 discrete sits at the opposite end of the spectrum from the simple quad op-amp design of the little canford amp I've got here. This is just to give an idea of how sophisticated headphone amps can get. You will pay a lot for it of course :). I have to say, this does look like a very nice amp.

www.audiosciencereview.com

Topping A90 Discrete (A90D) - Teardown and personal thoughts

I found not many teardowns with this model, especially with the output transistors uncovered and with surrounding close-ups, so I decided to purchase one for myself (second hand) to pair it with my D90 MQA then write an article here on ASR. Looks like taking the PCB out from the case if somehow...
www.audiosciencereview.com www.audiosciencereview.com
Click to expand...

That's a nice unit (and teardown).
 
Yes, ASR has some quality content.

I think that Topping amp would be somewhere near the current state of the art, looking at the measured performance he got, the build quality and the features they added. The op-amp version of the A90 gives the same measurements, but they added some nice upscale features to the 'D' version (covered in the 'pros and cons') section and the review conclusions. The only thing I don't like is the main-pcb mounted headphone jack sockets, I prefer headphone sockets to be mounted on daughter boards so that the sockets can be easily replaced when they inevitably break from having the jack plugs pushed in and out repeatedly; but for a home unit this is probably less important.

For anyone interested in making their own, Doug Self's website is of course one of the best resources in the world: http://douglas-self.com/
- though I wish he would update it to https!

And his book "Small signal audio design" is really the business (available on amazon, etc)

Small Signal Audio Design: 4th edition

The Douglas Self Site, audio amplifiers, Small Signal Audio Design
douglas-self.com

Another good book (that unlike the Self book is free!) is the natsemi audio book from 1977, admittedly this is now out of date, but it covers a lot of good ground.

archive.org

National Semiconductor Audio Handbook 1977 : National Semiconductor Corporation : Free Download, Borrow, and Streaming : Internet Archive

National Semiconductor - Audio Handbook 1977
archive.org
 
Just a bog-standard 3.5mm stereo cable... don't need anything special. On the one I've got the input is stereo 3.5mm jack, so I use one like this.

www.ebay.com

AUX Headphone 3.5mm Cable Male to Male Car Stereo Audio Cord Headphone PC Car | eBay

Model Number: Baseus M30 Stereo Audio Aux Cable. Style: 3.5mm Stereo Audio Aux Cable. Type: AUX Cables. Connector A: AUX. Connector B: AUX. Type: 3.5mm male-to-male Aux Cable. This cable is a great solution to protect your 3.5mm aux port from repeat pluging and unpluging.
www.ebay.com

Or if your headphone amp has 1/4" jack or 2 phonos, then you need the appropriate cable. Doesn't need to be anything expensive. It might be worth paying a little more for gold plated connectors, but I wouldn't worry about anyting like OFC cable or the other nonsense. The cable I'm using right now doesn't even have gold plated plugs.
 
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One more tip, if you're connecting the headphone output of the thinkpad into the line input of the headphone amp, then I would keep the master volume on the thinkpad fairly low, say 30%, and turn up the volume on the headphone amp itself, to avoid clipping in the headphone amp input stage. At least try that to start with. Let the headphone amp do it's job rather than feeding it with too high an input signal. You can then experiment with increasing the output of the pc's headphone socket.

Of course if you're connecting the line output of the PC into the headphone amp then this isn't an issue.
 
I checked the price of that Topping amp, it's ridiculously expensive IMHO. I would certainly want to listen to it and compare to other types before shelling out that kind of money on a headphone amp. The measurements ASR got in the review are very good, but whether that would actually sound any better listening to music, I don't know. I suspect the law of diminishing returns very much applies.
 
This looks like an interesting project for anyone who wants to try making one, and pretty low cost too. The concept is based on Doug Self's parallel 5532 investigations. He's got some very good reviews, FWIW. This uses a pair of opamps in parallel to drive each speaker, in place of one opamp with additional output transistors. It makes sense, as a dual or quad op-amp package is almost as cheap as a single op-amp, so buy the dual chip and just parallel them up to get more output drive current.

www.diyrecordingequipment.com

HC1 High Current Headphone Amp

The HC1 is an expandable, high-powered headphone amp designed specifically for critical studio monitoring. The HC1's circuit employs parallel amp stages for greater power and lower distortion. This parallel-opamp concept has been known in theory for decades and was put to practical use in...
www.diyrecordingequipment.com www.diyrecordingequipment.com

He's done a video giving an intro to the HC1.

View: https://www.youtube.com/watch?v=qU4i7Pd2PRE


Another place well worth a look is elektor magazine, they always used to publish high quality audio designs and provided a custom PCB service.
It appears they are still in business here: https://www.elektormagazine.com/magazine . It looks like you have to register to read their stuff. If you search archive.org you can find back-issues though, a lot of their older designs will still give excellent performance. Whether you can still get the pcb's from them is another question.
 
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Elektor headphone amp kit. This is an all-discrete design (no IC's). Spec looks very good, THD+noise < 0.005% @ 1 kHz (five parts per thousand, which is excellent).
Uses standard widely available transistors and they have a PCB for it. The designs they publish are usually excellent. Definitely worth a look.

www.elektormagazine.com

Low-cost Headphone Amp

There have of course been numerous designs for headphone amplifiers before this one, either more or less successful and simpler or more elaborate. The design presented in this article is straightforward, sounds quite good and can be built using well-established components.
www.elektormagazine.com www.elektormagazine.com
 
Sadly JDS labs appears to have stopped selling their CMOY kit, but they still have information on how to build it on their site here
and there are lots of other internet sites descibing how to build 'cmoy' type headphone amps. It's just about the simplest design going, although the elektor low cost one also looks very easy and has excellent specs, and the BD139/BD140 output transistors are going to beat any op-amp for current delivery. Another good site that describes the cmoy design is tangentsoft:- https://tangentsoft.com/audio/cmoy/ . A well-designed custom PCB is always going to be better than veroboard. To make something a bit better than a cmoy, ESP is another well-regarded source https://sound-au.com/project24.htm. I've listened to a couple of recent very expensive designs, a friend had one of the latest sennheiser headphone amps that cost about $2000, I honestly didn't hear much difference from the little quad op-amp design I'm listening to right now. I'm sure the expensive one measures better with the right expensive test equipment, but whether you will get any more enjoyment out of it is a moot point. I personally like the elektor design for its low cost and use of readily available cheap transistors.
 
angry_vincent said:
What cable do you use to connect line out from mobo to the amp input?
Click to expand...

I'd avoid any onboard processing of audio signals like the plague, especially if you want to listen on high-quality headphones.
I've never seen any PC onboard soundcard/chipset (especially that dirt-cheap realtek junk found on almost all mainboards) that didn't have tons of crosstalk and interference from all kinds of system load and data traffic (e.g. the typical squeaking noise from USB). Take a look on what amount of effort was taken on old PCI(e) sound cards e.g. by yamaha or turtle beach to uncouple the sound processing from all the noise a typical PC sends down its power lines, let alone all the other interferences...

That Topping D90 has a high-quality USB DAC, so one should definitely make use of it. In general, USB-DACs of more-than-adequate sound quality have become quite cheap nowadays - even way below 50$ there are many DACs available that will have a near-transparent sound and easily outperform any onboard chipset... spend a little more and you can even get a decent combination with headphone amp.
 
I dunno, they seem to have got the power line isolation pretty well sorted out nowadays. I never hear any digital / squeaking noise, hum etc. Maybe older motherboards wouldn't be so good though. All I can say is that the onboard dac sounds pretty good to me, I'm using a recent N100 mini pc, I can't hear anything nasty happening. And it doesn't cost and arm and a leg to try it! :) I would say at least give the onboard dac a try, if you have a fairly recent motherboard, before going and blowing 500-1000 dollars on an external dac+amp.

Maybe it doesn't have to be all that recent either, my thinkpad X201 is at least 10 years old, and I can't hear any noise on the audio output of that either. If you go back to pentium or 486 days, talking about things like turtle beach, sure, the PC power line noise was horrendous, but that's a long time ago.

I'm not sure that just because a chip has an "engineer crab" printed on the back and is low cost that it's "junk", either. Feel free to check out the datasheet here :-
www.alldatasheet.com

ALC889 PDF

Part #: ALC889. Description: 7.12 CHANNEL HD AUDIO CODEC WITH CONTENT PROTECTION. File Size: 1447.94 Kbytes. Manufacturer: Realtek Semiconductor Corp..
www.alldatasheet.com

www.tomshardware.com

What Does It Take To Turn The PC Into A Hi-Fi Audio Platform?

Most hi-fi audio is stored in digital form. With advancements in lossless compression, bit-perfect ripping/streaming, HD audio formats, multi-terabyte storage, and PC-friendly DACs, has the PC earned a place among high-end audio gear? At what price point?
www.tomshardware.com www.tomshardware.com
ALC889.jpg
 
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I'm not sure about the ultra-thin, cheap connecting cables on ebay though. I just got one today, I thought I would try one, it's got gold plated plugs but it doesn't sound as good as the old one. The whole cable is only about 3mm thick! The old one I'm using is a proper dual core shielded one like this, I think I would recommend one like this over the very cheap thin one. I haven't bought one for years, I didn't realise they had got so cheaply made.


I took a photo showing my old one (top) next to the new thin one (bottom) from ebay, the new one is the thin one. The new one is junk, IMHO. The old one is dual core shielded, I don't know what the cable in the new one is but it looks like rubbish. The plugs look lightly gold plated but it's extremely thin plating. Buyer beware.

IMG_20250212_174937.jpg
 
Sorry about this, but my advice is that you generally don't need an external DAC unless you have bad noise. The one build into your sound card is generally enough, just as hardworkingnewbie said three years ago.
 
I found another build-your-own headphone amp project, this time without requiring a PCB. It looks an interesting technique. He encapsulates it in resin. It's basically a cmoy-type circuit, like the others. He says heat dissipation is not a problem(!). Anyway it's an interesting project and nice to see a different approach. You will need to have some fine soldering and maker skills to build one of these :cool: . I have to admire the originality and craftmanship that went into this!

1739550062484.png


www.instructables.com

Crystal CMoy Free Form Headphone Amplifier

Crystal CMoy Free Form Headphone Amplifier: This headphone amplifier circuit is different to conventional modern construction techniques in that it is air Wired,P2P (Point to Point) or free form wiring just like in the good old Valve days before the intervention of PCB's and the transistor. …
www.instructables.com www.instructables.com
 
Chu Moy's original article is here, probably still the best read on building a single op-amp based headphone amp.

headwizememorial.wordpress.com

A Pocket Headphone Amplifier.

by Chu Moy “Thank you for your amplifier design. I built it and can’t believe how wonderful it makes my AKG K340 headphones sound as well as my Sennheiser 600.” – A DIYer. W…
headwizememorial.wordpress.com headwizememorial.wordpress.com
 
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