DIY Beyerdynamic A1 Clone

EASY EMI's at HiFiMART.com
Audiodoc

Audiodoc

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Finished a long pending project due to in-availability of some parts. This is a discrete solid state headphone amplifier modified from the beyerdynamic A1 headphone amplifier which costs around 50K. The clone on ebay costs around 9K.

Input capacitors are matched Axon 4.7 polypropylenes. Rest are BC electrolytes, panasonic silver micas. Mine are just 5.5K even with upgraded components! The fruits of DIYing!

LL


LL
 
Sennheiser hd650. I also have a DIY EHHA as my reference hybrid amplifier however it is 4 times costlier. This sound quiet close with a slightly different sound signature. Sounds neutral however the bass impact is a revelation and is smaller in size than the former.
 
Here is the link for the assembled one with chassis which costs $170 + customs.

GOLD- A1 Headphone Amplifier full assembled 110V/220V | eBay

Better buy the PCB and enclosure alone like I did and buy the rest of the components from your local electronics store. The polypropylenes are Axon from parts connection while silver micas and power transistors / opamps from element 14. This way you will have quality components for a cheaper price. The toroid is from torotrans and pot is a Alps blue velvet.

It is built worth trying for those who have difficult to drive cans.

Here is a review of the original A1 which only has 4 power transistors. Rest of the circuit is similar except for dual input which I didn't need.

http://www.whathifi.com/review/beyerdynamic-a1
7.jpg


4bedd183_6173166678_084b7691e4_b.jpeg
 
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Great work once again doc!

How much is the bias on the power transistors?(I am wondering if the body heatsink is enough)
 
They are warm to touch. Can easily touch for 10 seconds at normal volume levels, do get really hot at ear splitting levels. Bass is great can feel the air moving on my earlobes. Will upgrade to a better heat sink when I find one.

These solid state devices are really hardy and can work from -55 to 150 degrees with ease. The BD 139 140 translators can work on a supply of 80V I am only using +- 20 Volts.
 
Ya, the heatsinks gotta take account of Indian summer. :D

Beyerdynamic A1 has an output impedance of 100ohm, so it would indeed give a boost to mid-bass.
 
Awaiting the pictures of the beta 22 on the new backplane board. Why haven't you posted them as yet. What about the import of enclosures that abhishek had told me. i was interested in one.
 
We were hoping to put the pics up once the Beta22 got cased up, but finding a quality case of that size just hasn't been easy.Its a monster at 16" x 11" x 4" & needs lots of vents since it really gets hot.
The problem with importing apart from shipping expenses/custom is that most designs do not have the venting that I need. I could get these modded locally but that would add to cost & might ruin the finish too.
Also considering magma's new case but that might be a bit smaller than our requirements.
 
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Getting good and VFM chassis in India is next to impossible. You can try putting the Rcore and sigma 22 in one and run an umbilical to the next. it would look cool as well as may help sonically.
 
I proposed that a while back but it was vetoed.

I can get you good & VFM chassis in India, you just have to buy 100. :p
 
My HD650 has an impedance of 300 ohms so the effect of the 100 ohm output impedance which is around 80 Hz is subtle. It rather extends the lower end response of the HD650 as it has a slight midbass hump at around 250 Hz. I can reduce the output impedance of the amplifier to zero but that would lead to loss of short circuit protection.

Low impedance headphone are more prone to alteration of frequency response at the extreme ends of the spectrum.
 
Excellent work! the amp looks well built.

I wish you could built me one :p
 
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Audiodoc said:
My HD650 has an impedance of 300 ohms so the effect of the 100 ohm output impedance which is around 80 Hz is subtle. It rather extends the lower end response of the HD650 as it has a slight midbass hump at around 250 Hz. I can reduce the output impedance of the amplifier to zero but that would lead to loss of short circuit protection.

Low impedance headphone are more prone to alteration of frequency response at the extreme ends of the spectrum.
Click to expand...

You are right that the higher imp. headphones would be affected to a lesser degree by the amp's output impedance.
In the speaker world, people generally follow the rule of 1/8.Basically, the output impedance of amp is kept to 1/8th or lower than the impedance of transducer.
Anything lower would probably affect the FR to a degree.

Here's an article regarding effects of output impedance on headphone FR.
Have a look esp. at the response of HD800 which has a similar impedance curve to HD650.
 
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