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Old 16th March 2010, 12:35 AM   #1061
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Now for something different.
Two things came together recently .
I got a batch of brand new OPamps from BB, National and AD and i bought the new D.Self
book. I wanted to build his Precission Preamplifier since it came out in 1996 and to my surprise i found it unchanged in his new book.
I thought this could be an oportunity to try the new chips.
I enyoy a lot when other are doing good things and the Self design is clever and thourough. On the other hand he is dealing with the bipolar NE5534 that has input and ouput offset. To block all posible DC passes the signal is routed through no less then 9 high value elcaps and 6 foils ( plus a plethora of switches, potmeters and relays) until the tiny MC signal reaches the output. I do not want to start a discussion if that is audible or not but it created an unconfortable feeling in me.
I started to boil down the circuit to the minimum and by using Fet and servo technology plus leaving out the tonecontrol i could reduce the capacitor count to 3 foils in the subsonic filter. Actually i kept the subsonic filter because it is a good idea when you do not own a 10.000,-$ frontend with provision to clamp down the record.
It has the IEC extention build in with -3dB at 20Hz. That may be too agressive for some so i will experiment with the filter to find a maybe better compromise.
I am already building the MC stage. I did not use the Self design here. It is rather a very simple Phono Clone circuit with the twist that i can use a low value feedback resistor with the ADA4898-1. That comes in quite handy. I have build Phono Clones with the OP211 and AD797 that performed surprisingly well but making the feedback resistor smaller then 500 Ohm was not an option. With my Titan the gain was nearly 40dB and i had to reduce the gain at the output with a resistive devider. Not very elegant !
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Old 16th March 2010, 02:08 AM   #1062
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The Phonoclone Headamp.
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Old 16th March 2010, 02:13 AM   #1063
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Default Schematic

Quote:
Originally Posted by Joachim Gerhard View Post
The Phonoclone Headamp.

Hi Joachim,

I can't find the schematic of this phonoclone headamp, can you post it please?
Thanks in advance.

Best regards,


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Old 16th March 2010, 02:23 AM   #1064
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You find it in the DSJG i posted in post 1061.
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Old 16th March 2010, 02:32 AM   #1065
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Default That simple?!!

Hi Joachim,

Phono MC
OP5 = ADA4898-1

Well I'm all ears regarding noise and dynamics.

Please let me know how it perform.

Thanks!


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Old 16th March 2010, 02:57 AM   #1066
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I am just listening to it over my new headphone amp and inductive RIAA.
Input and output offset is nill so all is DC coupled. The inductive RIAA is very sensitive to even small offset but it works well.
Sound is quite transparent but i will listen more and will tel you.
Btw, quite fascinating to listen to vinyl over headphones.
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Old 16th March 2010, 03:03 AM   #1067
iko is offline iko  Canada
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Quote:
Originally Posted by Joachim Gerhard View Post
Btw, quite fascinating to listen to vinyl over headphones.
Yes, I miss listening to vinyl on my tube headphone amp run by salas' jfet phono stage!
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Old 16th March 2010, 03:13 AM   #1068
Salas is offline Salas  Greece
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Now we help Merlin tune it. JFETS go to Spain. Malaga is Costa Del Sol, but could not find one for Costa Brava. Sorry Merlin.
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Old 16th March 2010, 03:41 AM   #1069
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A photo of the setup cpmes later. You have to see it to beleave it.
That headphone amp was a great idea to listen at night.
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Old 16th March 2010, 03:44 AM   #1070
Salas is offline Salas  Greece
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You tweaked some valve amp for a phones out? Or you made dedicated with chips etc.?
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