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Old 18th July 2011, 02:43 PM   #121
EUVL is offline EUVL  Europe
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I never say anything like my design is better than others.

But for those few who bothered to build one, they all love it.
Especially if you have a low impedance can (like Grado or AKG), which the HD555 probably isn't.

Not that it will sound bad on a 555, but you are not using its current delivery capability to the full.


Patrick
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Old 18th July 2011, 05:20 PM   #122
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What is the impedance on the Grado or AK? Senn HD555 is around 50R.
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Old 20th July 2011, 06:58 AM   #123
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@Dr.H: Grado usually is 32ohm. AKG depend on models, 62ohm to 120ohm.

HD555 at 50ohm should be fine too... HD555 (and most Sennheiser phones) is not a current hungry phones

It is not the impedance itself, but the combination of low impedance + lower sensitivity that makes Grado and AKG need more current to really sing. While Sennheiser phones are usually highly sensitive (+ high impedance on the HD600 and above models)
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Old 20th July 2011, 07:01 AM   #124
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Copied my question from here to here...

@Patrick: sorry, for the very basic questions:
1. is this a unity gain amp (or not)?
2. could I put a potentiometer in the input?
3. what is the [maximum] acceptable preceding stage (source or pre-amp) impedance before the DAO?

thanks,
David
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Old 20th July 2011, 04:11 PM   #125
EUVL is offline EUVL  Europe
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Answered at the other place.


Patrick
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Old 5th August 2012, 08:54 PM   #126
tpsorin is offline tpsorin  Romania
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How will this amp compare to commercial amps? I am thinking of lower price commercial amps (<150USD).

I plan to use it with HD600. Is it worth bothering with it if i have Xonar Essence ST?

Thanks!
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Old 9th November 2015, 09:02 PM   #127
Hikari1 is offline Hikari1  United States
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I am reviving this ancient thread as it appears the DAO is just what I need for my Grados and I already have a nice preamp.

If I use this schematic (replacing IRFP240 for the toshiba mosfets), do the IRFs need to be matched to maintain low DC offset?

Are all resistors 1/4W except for the 3R/3W?

Any substitute for the J511? It's obsolete.

8.2V Zener is 5W OK?

Thank you Patrick, if you see this.
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Old 10th November 2015, 04:46 AM   #128
EUVL is offline EUVL  Europe
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Did you see this ?

The DAO SE all-FET Class-A ZGF Headphone Amplifier


Patrick
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Old 10th November 2015, 05:56 AM   #129
Hikari1 is offline Hikari1  United States
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Quote:
Originally Posted by EUVL View Post
Thank you Patrick. This is perfect. Looks like the info on the Dao got spread out over a couple threads but I trying to understand it all now. Interesting use of that power jfet...actually it's pretty genius. Thanks.
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Old 21st November 2016, 12:57 PM   #130
xrk971 is offline xrk971  United States
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Wow, a year has past since the last post here. I decided to give the DAO SE head amp a try. I like simple circuits. Anyhow, this is a first for me - my first ever home etched PCB! I used Uncle Carlos' trick (Destroyer X) of using nail polish to directly hand paint the traces by eye. It looks rough but turned out very functional. I hand drilled the holes with Dremel tool. Muriatic acid and hydrogen peroxide made quick work of the etching and in less than an hour I had a pair of my first hand made PCBs. Thanks to EUVL for the layout and Steen for the inspiration to make it work. Normally I would just deadbug P2P this but wanted to try etching on a simple project.

So here is one board soldered up and mounted on a Pentium CPU heatsink designed for 60w with a fan (I plan to use a small speed reduced fan):

Click the image to open in full size.

I was anxious to build something while waiting for ordered parts to arrive (LU1014 & J511, 8.3v zener). So I made some substitutions hoping something might work.

I am using a J310 JFET with gate tied to source for the constant current supply (they are 10mA capable) and since I do not have 8.3v zeners I am using 6.8v zener plus a red LED in series to get about same voltage drop. The big one is using an IRF610 in place of a the LU1014 JFET - I have no idea if this can even work but seems like it might.

I did not have my 25v class A supply handy so used the 21v supply from another project that was currently connected for a quick test. LEDs light up but the bias is all wrong as there is no current flowing. Checking gate voltage I only got 5.3v? Strange as a 6.8v drop across the zener plus 1.8v across the LED (after the zener) should present an 8.6v before the zener to drive the IRFP240 gate (through 220R). More debugging needed but at least no magic smoke was emitted and no FETs were harmed in the process. (actually, all these FETs were pulls from my failed allfet Circlotron build - tested to be functional in my new Vgs tester):

Click the image to open in full size.

So a few questions:

1. what is ideal zener voltage to use for IRFP240 to get 200mA bias?
2. can an IRF610 serve in place of LU1014 to make some music?
3. how closely do the Vgs values of both the IRFP's and LU1014's have to be matched or can we get by with adjusting source resistors by adding small parallels?
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File Type: jpg DAO-SE-HE-test-02.jpg (136.6 KB, 189 views)
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