Need to build JC 2 preamp

[dimitri]

‘Pooging Mark Levinson’s JC-2: Five Cheap Tweaks to Sonic Bliss!’, by Charles Hollander & John Curl, PF, Volume 8, Number 1

Back issues are available for $7. Email with your order lritsema@positive-feedback.com

 

[kamskoma]

Positive Feedback

I tried to get in touch with my former distributor of an execellent audio magazine trying to get this back issue with the preamp upgrade, but.. no positive feedback was delivered.
So can anybody post this article to me I would be very happy my address is balldanger@hotmail.com.

Thank you

GLHA

 

[mikeks]

From http://diyaudio.com/forums/showthread.php?postid=115702#post115702

Thanks, I will see what he thinks.

I know I have been on that website once before.
Probably some year ago.
I recognize some of the names of the amplifiers.

Thius is some of what he, Kostas Metaxas AUS, has to say:

The most significant difference between VALVE and TRANSISTOR circuits is the amplifier/power supply regulator circuit interaction which is far more critical in Transistor circuits.

In well designed Tube or transistor circuits, the ac gain will have nothing to do with the value of the supply rails.....easily demonstrated by using an active load....

Kostas' example is soooo flawed it beggers belief....

I suppose it goes to show you really don't need to know what you are doing to be succesful in the audio industry..... 🙁

 

[zinsula]

Continuing John Curl bashing?

😕 Did you HEAR this amp? Can you tell from that schematic that it doesn't sound good?


Tino


Edit: Where is mikeks post about the schematics gone? My point doesn't seem to make sense now.....moderators??

 

[mikeks]

Re: Continuing John Curl bashing?

My point doesn't seem to make sense ...

I agree....

 

[HKC]

After 5 years, I eventually finished my JC-2 clone. The sonic quality of my JC-2 is amazing. About 10 of my friends have listened to the pre-amp and they all give very positive comments to it.
I want to say thank you to you guys who gave suggestions and advices here.

Top view of the pre-amp:

 

[bear]

maybe put this post over on the Blowtorch thread?

http://www.diyaudio.com/forums/showthread.php?s=&threadid=71189

_-_-bear

 

[HKC]

maybe put this post over on the Blowtorch thread?

http://www.diyaudio.com/forums/showthread.php?s=&threadid=71189

_-_-bear

Hi bear

Good idea, here you go:

http://www.diyaudio.com/forums/showthread.php?s=&postid=1727692#post1727692

 

[HKC]

My next action is to build the phono section of JC-2. Here below is the original schematic:

 

[HKC]

And my pcb layout, board size 2 1/4" x 2":

 

[HKC]

Hi Mr. John Curl

VR5 forms part of the feedback network of the line stage, since I am not using balance control for my JC-2 clone, may I ask you what the value of the resistor should be for VR5?

 

[stoolpigeon]

HKC, did you find the upgrade article from Positive Feedback that John Curl mentions?

If so can you please send me a copy.

thanks, sp

 

[HKC]

HKC, did you find the upgrade article from Positive Feedback that John Curl mentions?

If so can you please send me a copy.

thanks, sp

Hi sp

Please advice your mail box.

 

[stoolpigeon]

HKC, please send to:

sandiefxz@_____.com where _____ is gmail

thanks again, sp

 

[gk7]

upgrade article from Positive Feedback

Hi HKC,

i just received a mail from Positive Feedback: "Sorry, we no longer sell or have back issues." Would you mind to send me a copy too ?
(Email: gk7@billrothhaus.at).
I own a ML-1 and one of the line modules recently started to make some crackling noise the first minutes during warmup, so it might eventually fail some time in the future. I plan to make replacement line modules (as close to the original as it is possible with modern parts, at least performance wise). The should fit in the original JC-2/ML-1 chassis of course, but would make a nice "building block" for other DIY line level applications as well, I believe.

 

[john curl]

I wish you well in making replacement modules for the JC-2, ML-1 preamps. I am just too old and tired to do it myself, but the need is there, and it is always a shame to see such a nice chassis discarded, because of lack of modules. I got a free JC-2 that way, but it was only valuable because I could fix it with pre-existing modules. Today, I am out.

 

[GRollins]

Anyone with a dead JC-2 can contact me. No, I won't repair it, per se, but I've always thought it was one of the most attractive preamps made and I'd love to build something into the chassis.
The basic circuit topology is still viable, but obtaining original parts is difficult and there are changes that could be made to update the thing to more-or-less modern standards. If I recall correctly the phono stage EQ is flawed--something I believe John would admit--although it can be tweaked to greater accuracy.
Hell, even if I don't build anything into it, I'd just like to have one around to look at.

Grey

 

[HKC]

It is very hard to found a JC-2 these days. One was selling @ USD3500.00 from Hi Fi Do Japan about 2 months ago.

 

[gk7]

It is very hard to found a JC-2 these days. One was selling @ USD3500.00 from Hi Fi Do Japan about 2 months ago.

There are currently two ML-1 for sale on that well known internet auction house, but no idea what the final price will be. (I bought mine in good condition and fully working for approx. 1000 EUR one year ago.)

 

[HKC]

There are currently two ML-1 for sale on that well known internet auction house, but no idea what the final price will be. (I bought mine in good condition and fully working for approx. 1000 EUR one year ago.)

1000EUR is a good price. It was few months ago, a ML-1 from Australia auction house end up with USD3000 something.