Gator based Headphone amp

[StanleyB]

I was busy testing and tuning the updated TC-7510 test rig PCB, which hasn't got a headphone output, with the Gator based headphone amp test rig over the last week or so. I was quite pleased how good the headamp sounds. It's a perfect match for my HD800 :).

http://www.homehifi.co.uk/images/aos/GAOS.jpg

[Alex_UK]

Well I can certainly vouch for the Gator board in the Caiman with my Grado SR60's - :wow: - never heard headphones sound so good!

Presumably there will be an improvement by isolating the components from the DAC and giving the headphone amp its own power supply? Any more details on the headphone amp Stan - is it going to be the same size as the current cases?

[StanleyB]

Presumably there will be an improvement by isolating the components from the DAC and giving the headphone amp its own power supply? Any more details on the headphone amp Stan - is it going to be the same size as the current cases?
The plan is to make it the same hight and depth, but keep the width to the minimum required. The stand alone headamp draws very little current even at ear bending levels, but it needs a very low noise power feed to show off its best with delicate and deeply detailed music. So I am busy updating an old power supply filtering circuit to try out.

[Fi-Wi]

Will the AD826 opamp be part of the dedicated headphone amp or are you testing others as well?

[StanleyB]

The main thing I am doing right now is trying out different configurations and components. Some designs can look lovely on paper, but sound mediocre at best once built.

[Fi-Wi]

Looking at the amount of components I guess that means there are about a zillion configurations possible (give or take a few). :eek:

[Techno Commander]

Will it have a linear or switched mode PSU?

[Peter Galbavy]

Can I suggest trying to make it work with a pair of PP9 batteries perhaps ? I know folks who love their portable headphone amps for their ipods (spit!). And maybe even a 3.5 stereo jack inputs and outputs as an option, for just that reason...

I have no honest idea how long batteries would last.

[Fi-Wi]

Any news on the headphone amp Stan?

[StanleyB]

Still working on it. The digital section needs careful consideration in its layout.

[Fi-Wi]

Great, I hope you progress well.

The Caiman/Gator combo works excellent for speaker output here, but for me it is useless as a headphone amp. The distortion I informed you about is too present so I stopped using it for headphone purposes.

[Fi-Wi]

I just found out that the distortion disappeared after replacing the standard Squeebox psu for a linear one ("Best of Both Worlds" for what it's worth).

I just felt I'd to mention this on this forum because people might get the wrong idea about the Caiman/Gator.

Keep up the good work Stan!

[StanleyB]

http://www.beresford.me/images/aos/TC-7523.jpg

It's slow going, but at least we have a working PCB. Some additional work needs doing, and a suitable small case needs designing.

The idea is to have a laptop friendly small footprint portable digital headphone amp. So the USB socket doubles up as a power supply input. Headphone output supports low to medium impedance cans. There is also a stereo line output so that the DAC analogue output can be fed to an amplifier. Alternatively, the line output can be used to feed a more expensive stand alone headamp.
The DAC can be powered via the USB port on your computer, negating the need for batteries or an external power source when 'in the field'.

USB is up to 24/96
TOSLINK and Coax are up to 24/192, including the harder to find 176.8KHz.
Headphone socket is 3.5mm as requested by Peter. Inputs are selected via a little switch on the back.

The small size and simple operating functions will hopefully allow me to keep the prize down, whilst offering a powerful set of input and files support options. Nothing concrete on the final price, but £150, including VAT, delivered is the target.

[Tim]

Interesting Stan :eyebrows:

[StanleyB]

Hi Tim, glad you see some potentials there :).
I have been in negotiations with an aluminium case manufacturer down in Brighton, who can design and build me a silver coloured case, or any colour I like, at a reasonable price. It's based on a modification of an existing mould of theirs. That's far quicker and cheaper than doing my own mould from scratch, if the quantity is smaller than say 1K. I might go that route, which could give me a product at perhaps £99.99 inc. VAT plus shipping. A 96KHz USB DAC at that price :mental:??? Now that would be something, but completely within the Beresford philosophy of a lot more for far less. My competitors will now hate me even more :rolleyes:..

[slate]

Nice feature list as such. However two things from looking at the PCB.
- Line out at the front?
- Inputs are selected via a little switch on the back?

But ok things can change.... unless it is by design

[StanleyB]

It's a very small footprint design, with PC users in mind. A lot of PC users tend to need just one type of input. So putting in a properly sized input selector at the front would require a wider case, which would increase the PCB size and drive up the price.
The line out at the front is there for quick plugging in and disconnection with little chance of mix up. You'll be surprised how many people plug one side of their phono output leads into the coax input by mistake when the DAC is small. There is the problem with an increased width of the PCB and case, which would make the portability size factor an issue.
It boils down to having a nice little high capability DAC at a ridiculously low price, or a more traditionally designed DAC at £200 plus. But just as people are getting accustomed to touch screens instead of keyboards and mice, it will take time and applications to see things my way...

[ZebuTheOxen]

With reference to this post:
http://theartofsound.net/forum/showpost.php?p=187167&postcount=3

Is there going to be a seperate power supply for this? Or is all the cleverness handled only by the filtering circuitry for the USB feed?

This DAC is exactly what I was looking for originally before I got the 7520 :)

[audionewbi]

Any updates on this?