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Old 16th March 2010, 04:00 AM   #1071
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Here is the seup for tonight.
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File Type: jpg Phonoclone Headphone Setup.jpg (455.5 KB, 443 views)
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Old 16th March 2010, 04:32 AM   #1072
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You are getting more hardcore DIY every night lately. What is next? Mercury rectifiers and horns? So you drive AKG etc. from its main output, or is it something cct boosted especially for phones output?
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Old 16th March 2010, 04:47 AM   #1073
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On the floor is my headphone amp. I posted it some time ago but i am still working on it.
It has 30mA class A and i whould like to bring it up to 100mA. There is also a kind of strange distortion when i crank it on the inefficient AKG701. Letīs see what i can do when i have my new measurement equipment for my home.
At work there is still a lot of construction going on and i expect to be back in my lab not before the end of April. That is also the reason i have a lot of time for my hobby.
At work i can not do much momentarily except setting up the soundroom for a party on friday.
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Old 16th March 2010, 04:59 AM   #1074
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That 701 is difficult. My neighbor has a pair and we made a single Mosfet buffer with CCS, like mini Zen, it was driving my Grados loud from CD level. AKG dead, would not bother. So I did a virtual ground to provide symmetric bcs it had just a single polarity 600mA reg, and boosted voltage gain by sticking an OPA in front. Only then the 701 woke up. That buffer was running hot bias.
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Old 16th March 2010, 05:06 AM   #1075
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I was particular disapointed by the bad soldering they did and one channel measures 10 Ohm more then the other, so tonight i listened to Sennheiser PX200.
That little thing is damn good.
Have to go to bed now. Tomorrow i am driving to the Netherlands.
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Old 16th March 2010, 03:30 PM   #1076
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Default Hanze Hifi ?

Hi Joachim,

To bad I didn't get your post earlier, in fact I didn't get it at all.
I was searching for an earlier post of you and read that you're in Holland today!
Are you visiting my friends, Jaap and Johan?
If yes, I would have done everything to be there to meet and talk to you.
Nevertheless Germany is not so far so maybe next time...........


Best regards,

Audiofanatic (José)
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Old 16th March 2010, 03:35 PM   #1077
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yes, i will visit hanze tomorrow, maybe we can meet there.
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Old 16th March 2010, 03:52 PM   #1078
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Default Hanze

Hi Joachim,

I'll check with them and see if I can be there too. After your meeting with them.

I will have to cancel some other meeting I have to be there, but I'll do my best to be there.

To bad I didn't know about this earlier.

You'll hear from me asap.

Cheers,

Audiofanatic
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Old 18th March 2010, 03:03 AM   #1079
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Default Listening to phonstages and further work on the headphone amp.

I visited a friend and we listened to phono and also listened and measured my headamp
on an Audio Precission system.
We used my REGA turntable with Lyra Helicon on a Roxan stand.
First we listened to the High Z MPP with inductive RIAA and later we substituted the MPP
with the ADA4898 phonoclone.
Noise in both setups was no problem. The MPP dead quite and the Phonoclone had a low level of hiss that sounded like white noise, ear on the electrostatic speakers at decent volume. That ADA4898 has a very low 1/F corner frequency and is superior to the AD797 in that issue.
We both preferered the MPP slightly. It had a more robust and full sound. The Phonoclone was typical for circuits like that. Very fast and clean, maybe a little sterile but with very good resolution, fascinating in itīs own right. This is a very simple little project that you can build in one afternoon. If you want even less noise you can parallel
4 or 8 but that drives the price up ( that chips are not cheep) and a discreet stage can be made for that money.
It was very interesting to listen to and measure the headamp. I had constructed it without any measurement equipment just by common sence and listening and in fact it sounds just fine. We usen the Sennheiser PX200 that worked extremely well.
This is a great bargain when you want to try headphone listening without spending a fortune. Measuring it brought interesting results. We measured the Fet buffer, the linestage and the outputstage seperately. Clipping was at 7.5V RMS. That is loud enough for hedaphone listening but i am contemplating to raise the output for my hard to drive AKG701.
The Fet produced around 0.2% distortion, mainly second harmonic and very linear over frequeny. The compleet amplifier had an exponentially falling distortion profile.
A recipy for good sound in my experience. The shunt feedback voltage amplifier was of cause 100x better and the diamond buffer alone was also under 0.002% so it is posible to run that stage open loop as an option. If you are uncomfortabe with the Fet i designed a new version with OP buffer and servo that should have neglible distortion.
Letīs see how it sounds subjectively. 0.2% second harmonic does not sound like distortion though and one version could have a provission to switch betwen the Fet and OPamp and also between open and closed loop.
I also made a headphone output for the Self phono-linestage. I use the LME49713 that can drive 100mA in the outputsatge, so headphone listen should be posible with most models except the current hungry monsters like the AKG701.
I had a chance to listen to the new Sennheiser HD1000 today and was extremely impressed. The sound was 100% my taste. Clean, fast and punshy in the bass, open, uncoloured midrange and very good detain in the treble.
Attached Files
File Type: pdf JG Headphone Amp com.TSC - TINA.pdf (60.2 KB, 106 views)
File Type: pdf D. Self Preamp DC.TSC - TINA.pdf (70.8 KB, 107 views)
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Old 19th March 2010, 07:13 AM   #1080
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Default The dirty details

Some visuals:
This picture shows prototypes of Joachims' line amp/headphone amp at the top, his very compact prepre consisting of a new hot opamp and one (yes, one) resistor at the left. The batteries that supplied power to the prepre can be seen at the extreme left (black bricks).
The RIAA preamp is in the metal box, supplied by LC Audio power. It has the inductive RIAA, and the two coils, in sowter xformer cases, can be seen external to the box.
To say it sounded great must be the understatement of the month.

jd
Attached Images
File Type: jpg headph & riaa & prepre.JPG (417.5 KB, 361 views)
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Last edited by jan.didden; 19th March 2010 at 07:16 AM.
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