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haejuk 8th May 2012 04:20 PM

Any good DIY amps for low impedence/high sensitivity headphones?
I am new to DIY and would like to build a desktop amp that will work well with my Denon D2000 headphones. They are low impedance (25 ohm) with 106dB/mW sensitivity. I am looking to build either a solid state amp or a hybrid amp that is suitable to drive them. I have heard that the Starving Student Hybrid is too noisy to work well with these phones.

Basically I want to know which desktop DIY amps have low output impedance, a black background, and are able to deliver a good amount of current into 25 ohms. Also thinking of getting a pair of orthos, if I can find something that delivers enough current that plays nice with my D2ks.

Any suggestions? I am working on an O2, but really want a nice big thing for my desktop for my next project. I am curious about CKKIII, but don't know the specs I am interested in.

Osvaldo de Banfield 8th May 2012 05:33 PM

Perhaps a simple TDA2822 can do the job.

jcx 9th May 2012 02:59 AM

you don't need V gain at all - buffer not amp - consumer Desktop source mostly 2 Vrms, most DAP 1 Vrms 0 db fs

even then a ~12 dB stepdown audio ouptut xfmr would be best to preserve S/N

burgunder 10th May 2012 02:09 PM

Some of this will explain the above post.

haejuk 10th May 2012 08:43 PM

That did explain it quite well. It also makes me want to try to build something similar to what was made in that link, but I don't have the knwoledge to put it together without pcbs, circuit diagram, and BOM. I might be able to just get it done with a circuit diagram, but I think I should get some more experience first.

I will have to check how loud my headphones get when plugged directly into my source (I think it is 1.7v RMS). I am concerned about the prospect of just using an attenuator, and I think this blurb from sums it up: "Despite the AH-D2000's seemingly efficient impedance rating of 25 Ohms, it's overall sensitivity and heavy voice coil driver mass will still benefit from dedicated headphone amplification and control to hear exactly what it can sonically accomplish; otherwise, the sound may tend to be lightly 'flat' and un-dynamic, especially from portable audio sources."
I have had less than stellar results by plugging D2000s into my iPhone, namely a poor low frequency response. They get quite loud, but sound disappointing.

jcx 10th May 2012 08:54 PM

a buffer provides Current amplication but only unity Voltage gain

for the D2000 Z, sensitivity # you should be able to caclulate SPL: ~120 dB for 1 Vrms drive

iPods and other DAP often have too small a output coupling C which rolls off the lower few octaves - worse with lower Z headphones

if you don't need to reach 120 dB SPL often then even DAP could be used with 25 Ohm load with bass boost EQ to compensate for the RC roll off

burgunder 11th May 2012 07:55 AM

I do BTW have a pair of Fostex T50rp which need 3-4 times more power than the Denons and if I plug them directly to the relatively week line out of my Ibasso D7 they are to loud. You will BTW find measurements of a lot of headphones at Headphone Data Sheet Downloads | InnerFidelity

haejuk 11th May 2012 03:11 PM

Ok, I tried my headphones connected to my 1.7v RMS source, and it was about as loud as I would ever want it. You guys are really good, and I hope one day to be as smart and capable as you all.

burgunder: Is there a kit to make what you linked? That looks like it would be perfect for me, although I would prefer having a power supply rather than 4x 9v batteries. If there is no kit I will have to read through it a few more times and try to come up with some questions about what was used to make it and how I should start.

kawo 20th June 2012 03:08 PM

Hi haejuk:
You can try to do the HPA-2 headphone amp. kit, you can find on ebay.

ethanolson 20th June 2012 08:02 PM

I'm with @jcx on this one. I recommend you go after a CMOY with unity gain (i.e. a buffer), but configured with <1Z to get all the benefit possible from your 'phones.

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