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Old 23rd November 2010, 01:09 PM   #1921
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Hello Sam !
The Mu-Metall sheet arived today. Thanks.
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Old 24th November 2010, 01:29 AM   #1922
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I got the Hensler Coils. They are really cute. See the picture compared with a standart computer mouse.One coils is spot on and the other 2% low. I think this is really good if you consider that the 1mH tab has only 50 windings, and 1 winding is already 2% of the total. Windings are made with HF litz wire and dipped in shellac. The whole coils are clued and dipped in scellac too and heated and burned in with current. I will put them in on wednesday and report. DC resistance of the 1mH winding is 0.8Ohm so i am able to finetune with resistance.
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Old 24th November 2010, 02:00 AM   #1923
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Quote>I can send a DIN A4 sheet of self adhesive MU-Metal Foil, If you want to try it.

VG

Sam

Hi Sam I have been looking for just such a ting for quite same time could yuo help me get same of it please.

many tanks

Al
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Old 24th November 2010, 03:54 AM   #1924
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Salas, you are right. There have being passive inductive RIAAs. I found at least one example from the 50th. A Perpetuum Ebner circuit from the Black Forest that was a prerunner of DUAL.
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File Type: jpg Inductive RIAA PE 50th.jpg (97.9 KB, 511 views)
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Old 24th November 2010, 04:11 AM   #1925
Salas is online now Salas  Greece
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With an HF step switch even. Respect.
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Old 24th November 2010, 11:22 AM   #1926
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This circuit was for pre RIAA mono records and it has a rumble and adjustable scratch filter, so playing records before 1957 was a chalange that required some skill from the user.
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Old 24th November 2010, 01:40 PM   #1927
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I have now installed the Hensler coils. Hum is much reduced and soundqualiy is very good now. I also build some small Mu-Metal caps so i will listen if can can hear rising distortion when the coils are shielded.
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Old 29th November 2010, 07:33 PM   #1928
masag1 is offline masag1  Germany
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Default Hawksford Cascode Buffer - Layout is done

Hallo Joachim!

My friend Klaus did again a good job.

Thanks Klaus!

Proto-boards will arrive this week.

Regards

SAm

With
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File Type: pdf Puffer_Best_sol_cmp.pdf (95.1 KB, 156 views)
File Type: pdf Puffer_Plan.pdf (32.8 KB, 139 views)
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Old 29th November 2010, 08:18 PM   #1929
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Looks very good ! Tell me how you like the sound when its ready.
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Old 6th December 2010, 12:59 AM   #1930
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I have now recovered full from the ETF festival and of cause one of the things i am working on is a phonostage. I bought some very low noise Toshiba N-channel J-Fets recently.
The 2SK170 i use here quite often is by no means the lowest noise J-Fet ever designed.
In fact it is a 30 year old design and technology has moved on since. The main advantage the 2SK170 has, is that it has a P-channel complement and that makes my parallel symmetric open loop stages posible. Parallel symmetric design cancels second harmonic, the major source of distortion in a sigle ended J-Fet stage so low distortion open loop circuits can be build that way. Voltage Noise can be lowered by paralleling using the Faulkner circuit but that does not have a influence on the rather high 1/f frequency of the 2SK170-2SJ74 pair. In praxis noise under 1kHz is higher in a J-Fet circuit then using bipolars. Psychoacoustics help out here because of the Fletcher-Munson curve but the effect is real and measurable. In 2004 Toshiba brought out a new generation of J-Fets that had a much lower 1/f frequency and a higher transconductance of 40mS. Input capacitance did not get up much so it is posible to build a J-Fet input stage with 4 of those in parallel that is even lower in noise under 1kHz then 4 plus 4 of the older generation plus half of the input capacitance. Unfotunately there is no P-channel compliment so i started to think about a low distortion single ended N-channel design. One thing you can do is cascoding and that lowers the distortion much. Examples are the Salas Simplistic, the Pass Pearl or the Aksa Paris. Still this designs do not reach my target of -80dB distortion at 1V out @ 20kHz. Feedback can be used of cause and that is the road i took.
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