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Need to build JC 2 preamp
Need to build JC 2 preamp
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Old 20th April 2013, 01:36 AM   #421
elektroj is offline elektroj  Europe
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Quote:
Originally Posted by gk7 View Post
R8, R9, R10 are not present in Johns schematic, but my original modules obviously have a second pot for offset adjustment so I "borrowed" this from the ML-2 power amplifier which uses the same topology as input stage.
Thanks for the info, gk7. So, it was a bit of guesswork.. Did John "blessed" it?

Quote:
Please post it, Iīm curious to see it.
It's a ML-5 record amplifier. PM me with you email - I'll send you some more.
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Old 23rd April 2013, 04:51 PM   #422
ivodonchev is offline ivodonchev  Bulgaria
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Hi guys,
because I do not need a phono stage, is it possible to build the preamp in the way shown in the picture?
Are there any possible problems with the stability?
Any ideas are welcome!
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Old 23rd April 2013, 05:09 PM   #423
john curl is offline john curl  United States
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You make it too complex. Don't use the first gain block. Come in directly to the gain pot. That is how we do it.
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Old 23rd April 2013, 05:27 PM   #424
gk7 is offline gk7
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Quote:
Originally Posted by elektroj View Post
It's a ML-5 record amplifier.
This one I knew, but whatīs inside the ULD modules ?
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Old 23rd April 2013, 06:22 PM   #425
ivodonchev is offline ivodonchev  Bulgaria
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Quote:
Originally Posted by john curl View Post
You make it too complex. Don't use the first gain block. Come in directly to the gain pot. That is how we do it.
Thank you Mr. John Curl,

You are right - the simpler schematic is better. But in my case I have tube out CD Player which is anode out and the output impedance is around 1-1.2k which is too high to drive 10k gain pot. That is the reason to put the first gain block. Is there any other technique to avoid the use of the first module? In my case, what would you do?

Thank you in advance

Ivo
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Old 23rd April 2013, 06:27 PM   #426
john curl is offline john curl  United States
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It would be best to just use an open loop dual fet follower.
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Old 24th April 2013, 12:30 AM   #427
elektroj is offline elektroj  Europe
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Quote:
Originally Posted by gk7 View Post
This one I knew, but whatīs inside the ULD modules ?
gk7, if you look at the ML-1 manual that YOU posted, you will see that line amps in the schematics are also marked ULD-4 :-)
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Old 24th April 2013, 06:13 AM   #428
gk7 is offline gk7
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Yes, I know. And what does this tell us about the content of the ULD-4 ? I donīt get your point.
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Old 24th April 2013, 06:23 AM   #429
gk7 is offline gk7
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Quote:
Originally Posted by john curl View Post
It would be best to just use an open loop dual fet follower.
Here is a nice one ;-)

http://www.diyaudio.com/forums/analo...ml#post3431096

Could be made with a LSK389:
http://www.linearsystems.com/assets/...ets/LSK389.pdf
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Old 24th April 2013, 09:31 AM   #430
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by ivodonchev View Post
Thank you Mr. John Curl,

You are right - the simpler schematic is better. But in my case I have tube out CD Player which is anode out and the output impedance is around 1-1.2k which is too high to drive 10k gain pot. That is the reason to put the first gain block. Is there any other technique to avoid the use of the first module? In my case, what would you do?

Thank you in advance

Ivo
Quote:
Originally Posted by john curl View Post
It would be best to just use an open loop dual fet follower.
located at the tube output.
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