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Old 17th August 2010, 01:39 PM   #4461
RCruz is offline RCruz  Switzerland
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Hi SGregory

So you are building a TT ?
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Old 17th August 2010, 01:57 PM   #4462
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Yes. I would like to build a similar unit to what coleman presented earlier. I plan on building two. The first will use the rd-80 bearing/motor and inner platter. The plinth/outer platter will be made new using wood, and will use the magnapan tone arm.

The second table will be an all out design, using magnetic bearing (being machined now), composit wood platter, and whatever else I learn from the firts build. I hav even thought of building the Schroeder arm 12".

My current rd80 is basically a drum. I was so sure of myself 20yrs ago on the virtues of mdf that I tore apart the original plinth and made a new one out of it. The suspension subplinth is now mdf as well. The only thing I did right was keep the geometry the same between the two tables. Turns out that the original geometry wasn't right for the magnapan arm.

The Generation2 table will be designed for the magnapan arm geometry, it won't have a suspension but will be antiresonant. I hope this won't take too long.
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Old 17th August 2010, 02:05 PM   #4463
RCruz is offline RCruz  Switzerland
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Please be so kind to post some pictures in the future.... maybe a new thread would be more apropriate

I also have a modded RD80, but want to build a heavier unit in the near future !

PS: I also liked your riaa case... did you build it yourself also ?
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Old 17th August 2010, 04:27 PM   #4464
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Yes, I build all my cases. It is the one thing that I can do autonomously. Aluminum is easy enough as it can be worked with carbide bits and jigs. I have an old table saw fitted with a fine non ferrous blade. The steel enclosures are a different story. My friend works for a heating/AC company, so I asked him to make the internal steel enclosure. I tried to do it myself but without proper sheet metal tools it looked like my first clay pot I made in pre school.

I will start a new thread soon on the Gen2 turntable build as the project develops.
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Last edited by SGregory; 17th August 2010 at 04:29 PM.
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Old 17th August 2010, 05:36 PM   #4465
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Default Late arrival to this loooong and very interesting theme.

Dear Salas,

During the all day I've tryed to read all posts (yes from the very start), and saw a big evolution on this very good implementation.

I am almost new to TT life, been around for some time on DIY Audio, mainly on amps and preamps.

Now I am very much interested in building your design, could you please direct me to the right schematic post for a Denon DL 103? + the Shunt supply?

I am now just finishing my lattest 300B amp to use with OB speakers, I have used a lot of good parts like Mills, Hashimoto C cores, Lundhal, Tant resistors and teflon Yamamoto valve bases, I will post a photo tomorrow.

By the way are their any PCB's for this implementation?

Many thanks in advance.

PS- Ricardo I see that you are deep in this, and I see that you leave near me in Cascais (I am from S.Pedro), I have NO interest in the commercial aproach (I am a Mechanical Eng by formation but working in the Financial world for more than 17 years), just for my own enjoyment, maybe we should get toghether and change some experiences. I can only share my thoughts of DIY with Rui Borges a good friend from very long, and the one that built my wonderfull TT.
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Old 17th August 2010, 05:58 PM   #4466
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rclourenco,
1) Obtain a batch of 2sk170BL's and measure Idds. You will need to match up several pairs to get the values right. I started with a batch of 30 and it was enough barely. I got lucky.
2) There are no PC boards as it is very individualistic. Making a PC brd is easy enough though.

3) This is a worthwhile effort!!!
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Old 17th August 2010, 06:24 PM   #4467
Salas is offline Salas  Greece
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Quote:
Originally Posted by rclourenco View Post
Dear Salas....
As SGregory pointed out, any PCB would be very individual due to huge dimensional differences in passive components selected or tried out when tuning later. In the round up PDF there were a few board layouts but I have seen nobody using somebody else's yet. In my view the circuit's nature lends itself to point to point and that can have some benefits on top.

As he said, on the other points also. After you got some IDSS pairs and you give more info about the gain structure of your system, only then the best values can be pointed out.

This is open loop you see, means no auto gain control, plus the JFETs varying gm nature reflecting in IDSS, keeps it much individualistic. A recent mistake of 2mA in IDSS in just one stage threw it off THD spec as you have read in the previous last pages for instance.
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Old 17th August 2010, 08:51 PM   #4468
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Quote:
Originally Posted by SGregory View Post
rclourenco,
1) Obtain a batch of 2sk170BL's and measure Idds. You will need to match up several pairs to get the values right. I started with a batch of 30 and it was enough barely. I got lucky.
2) There are no PC boards as it is very individualistic. Making a PC brd is easy enough though.

3) This is a worthwhile effort!!!
Hi, thanks for your help. Could you just tell me the best way to measure Idds?

cheers
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Old 17th August 2010, 09:02 PM   #4469
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Quote:
Originally Posted by massimo View Post
Does the "simplistic star ground" work?
Next step: "star power"

Take a look what's going on and..... enjoy!
Hi Massimo,

Fantastic design; Have you implemented this? if so could you send the silk screen with component placement and values?

thanks in advance.

cheers
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Old 17th August 2010, 09:41 PM   #4470
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rclourenco,
Be patient in the pc board department. You will want to gather some parts first as your board may end up different..

Measring Idss is easy. First get a bag of 2sk170BL's.
You will need a DMM, 9Volt battery, a 200+/-Ohm resistor.
I accurately measured the resistor and wrote the value down. I connected the DMM across the resistor. Use ohm's law to calculate the current.

by shorting the gate and source together you measure the current it passes to the drain with the resistor in series with the 9V battery. It will be in the range of 6 to about 12 mA for the BL's.

I then taped it to a sheet of paper with its value to keep it sorted.
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