Just tried it with Chrome (although on Linux) and the link took me to page 19 (with the schematic in post #188).
Maybe you have a different number of posts per side. This is a link specific
to the post #188:
http://www.diyaudio.com/forums/solid-state/10160-need-build-jc-2-preamp-19.html#post2092626
Does this work ?
Yes, I have 50 posts per page.
But it seems to be the way that folk collect data on the post to be linked to. Some get it right.
Link in post223 takes me to post188.
I re-checked post220, sure enough it takes me to the wrong post.
I have tried explaining this at length in number of threads, but the posters could not replicate the different addresses I see in the links.
What did you do different between the two links?
Obviously what you did in 223 works properly.
After redirecting 223 looks like this
tp://www.diyaudio.com/forums/solid-state/10160-need-build-jc-2-preamp-4.html#post2092626
post 220 address looks like this
tp://www.diyaudio.com/forums/solid-state/10160-need-build-jc-2-preamp-8.html
But it seems to be the way that folk collect data on the post to be linked to. Some get it right.
Link in post223 takes me to post188.
I re-checked post220, sure enough it takes me to the wrong post.
I have tried explaining this at length in number of threads, but the posters could not replicate the different addresses I see in the links.
What did you do different between the two links?
Obviously what you did in 223 works properly.
After redirecting 223 looks like this
tp://www.diyaudio.com/forums/solid-state/10160-need-build-jc-2-preamp-4.html#post2092626
post 220 address looks like this
tp://www.diyaudio.com/forums/solid-state/10160-need-build-jc-2-preamp-8.html
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Link in #220 is a link to the thread's 19th page (which is not universal since users can change posts per page in their preferences). It is done by copying and pasting the URL that appears on the browser's address bar.
This should be avoided.
Your 19th page could be my 4th page because we have different posts/page settings.
Link in #223 is a link to a specific post (which works for everyone).
This the right way to link to a specific post.
You go to the top right of the post's frame and copy-paste the link that appears on the post's number (e.g. #225).
That link will work for everyone.
For example, in my post, if you check the URL that appears on #225 (top right of the post's frame), you get:
ttp://www.diyaudio.com/forums/solid-state/120243-variation-jc-2-preamplifier-5.html#post2876002
This link is pointing to the 5th page of the thread and post #2876002 (2.876.002th post ever made in DIYAudio, more or less = unique).
Even if you have different posts per page settings, it will override the "5th page" thing and take you to my post.
This should be avoided.
Your 19th page could be my 4th page because we have different posts/page settings.
Link in #223 is a link to a specific post (which works for everyone).
This the right way to link to a specific post.
You go to the top right of the post's frame and copy-paste the link that appears on the post's number (e.g. #225).
That link will work for everyone.
For example, in my post, if you check the URL that appears on #225 (top right of the post's frame), you get:
ttp://www.diyaudio.com/forums/solid-state/120243-variation-jc-2-preamplifier-5.html#post2876002
This link is pointing to the 5th page of the thread and post #2876002 (2.876.002th post ever made in DIYAudio, more or less = unique).
Even if you have different posts per page settings, it will override the "5th page" thing and take you to my post.
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The good thing about that eBay kit is that everything is provided.
But I still want to know the schematic they use. Jim's Audio says that:
"The whole amplifier circuit is now essentially the same as JC-2, with the output stage changed from JFET to medium power NPN and PNP. We intentionally increased the quiescent current to let them work at class A. This enhances the current driving power and gives the whole preamplifier a warmer sound presentation".
What output JFets were those? There were none in the original line preamp, AFAIK?
Is there any other JC2 kit on ebay?
But I still want to know the schematic they use. Jim's Audio says that:
"The whole amplifier circuit is now essentially the same as JC-2, with the output stage changed from JFET to medium power NPN and PNP. We intentionally increased the quiescent current to let them work at class A. This enhances the current driving power and gives the whole preamplifier a warmer sound presentation".
What output JFets were those? There were none in the original line preamp, AFAIK?
Is there any other JC2 kit on ebay?
Thanks Shaman.
I had half a dozen Members arguing about this and none could see that they were doing it incorrectly.
You have explained it well.
Here is a schematic from another JC-2 kit, and I would venture to say that Jim's Audio knows his stuff from email conversations. I don't think you will go wrong with his kit. For one, his command of English is perfect and he can explain his approach effectively. The transistors he uses are from Toshiba and I think are better performing than what you may normally find in the JFET/KFET positions (due to lower junction capacitance--don't ask me to explain).
The Alps pot came from Mouser Electronics - Electronic Component Distributor, 100K resistance. The pot is not in the kit, but I think he can sell it to you for extra.
The kit has its own power supply, so it feeds directly off the transformer. That other power regulation board is for the phono stage only. It is from eBayer Audiowind.
Get the kit, it is way worth the expense. You'll get all the help you need from Jim.
Attachments
Even I am slightly confused. '-)
First, there are 2 separate schematics for the Levinson JC-2
There is the PHONO amp
And there is the LINE amp.
Most everyone builds the LINE amp, sometimes they change it slightly. It is simple enough that you can't do much 'damage' by changing the parts a little.
The PHONO amp is different:
It originally used complementary high Idss jfets in parallel push-pull, that self biased themselves. Apparently, Jim's Audio converted the output stage to complementary bipolar devices for ease in matching and construction. This is 'OK' but not as good as a complementary fet output, because the output devices are not then followers, but complementary BETA MULTIPLIERS, not as good as followers.
First, there are 2 separate schematics for the Levinson JC-2
There is the PHONO amp
And there is the LINE amp.
Most everyone builds the LINE amp, sometimes they change it slightly. It is simple enough that you can't do much 'damage' by changing the parts a little.
The PHONO amp is different:
It originally used complementary high Idss jfets in parallel push-pull, that self biased themselves. Apparently, Jim's Audio converted the output stage to complementary bipolar devices for ease in matching and construction. This is 'OK' but not as good as a complementary fet output, because the output devices are not then followers, but complementary BETA MULTIPLIERS, not as good as followers.
Now the confusion is a bit larger...
Whaleman: did Jim's audio provide you with a schematic for the circuit you assembled? Can we see it?
That circuit you showed seems to be different from the others on this thread, because it has Fet/Bipolar output that is not on the original JC-2 line-amp or on any of the other JC2 schematics I have seen.
People from Jim's Audio refuse to provide any schematic BEFORE you buy the product, and I won't buy the product until I see the schematic. This is not a renowned product that you buy at a store, this is an eBat kit supposedly cloning a certain product. So I want to know what product is the one they are cloning and how they are cloning it. The schematic will help on that.
Whaleman: did Jim's audio provide you with a schematic for the circuit you assembled? Can we see it?
That circuit you showed seems to be different from the others on this thread, because it has Fet/Bipolar output that is not on the original JC-2 line-amp or on any of the other JC2 schematics I have seen.
People from Jim's Audio refuse to provide any schematic BEFORE you buy the product, and I won't buy the product until I see the schematic. This is not a renowned product that you buy at a store, this is an eBat kit supposedly cloning a certain product. So I want to know what product is the one they are cloning and how they are cloning it. The schematic will help on that.
As far as I can tell, Jim's Audio JC-2 does not contain the cascode buffer at the outputs. I also asked him about posting the schematic, I think it is early morning in Hong Kong.
Had a seasoned audiophile come over with his music to listen to the JC-2 pre, he was quite impressed and said it was the best he'd ever heard my system sound. Now this guy does not cut me any slack when something is amiss or off. But don't take my word, try it--or buy the vintage Mark Levinson JC-2 now on eBay for about $2,400.
I bought the case as a blank box with the vents and it is solid aluminum. I do some polishing to make it look like stainless.
Here are some part numbers and sources to help get the project going:
Pick your size cabinet from Par-Metal: Par-Metal
The same place sells the toroidals, PN AN-0518 Antek - Transformers - Grid View
From Mouser Electronics - Electronic Component Distributor
Knobs
IEC connector
X-class capacitor
y-class capacitors
1M ohm resistor
selector switch 105-SR2611F-34-21RS
balance pot
Alps volume pot 688-RK27112A00AK
Power entry module 562-703W-00/03
Suppression film cap X class 75-F17734102000
Radio Shack:
Fuse holder + 1A fuse
eBay:
Jim's_audio JC-2 Kit
Audiowind phono preamp and power conditioning board
Parts Express: the #1 source for audio, video & speaker building components
on/off neon lit switch 66-2292
feet 260-774
RCA jacks 091-1120
Hope this helps someone get started and post your JC-2 pictures.
Tubeshunter sells a similar kit to Jim's audio. At least they do show the schematic, both for pre and on-board supply.
DUAL DIFFERENTIAL FET INPUT STEREO LINE LEVEL AMPLIFIER! JC-2 | eBay
I think someone on this thread also mentions having buying it. Any comments?
DUAL DIFFERENTIAL FET INPUT STEREO LINE LEVEL AMPLIFIER! JC-2 | eBay
I think someone on this thread also mentions having buying it. Any comments?
The picture of the board whaleman has used, looks identical to that from the ebay link in post #237. I believe that the schematic thus is the same (without the non original output buffer). So this is more like the original JC-2 line stage. The currents they have chosen are a bit low IMHO. The JC-2 line stage was a scaled down (current wise) version of the line driver John made for the Greatful Dead. Further reducing currents is not a move in the right direction I think, if you want the best possible performance from this circuit.
(I think it would be possible to modify the kit for higher class a current.) That said, I believe it is still better than any opamp based circuit out there as it is.
(I think it would be possible to modify the kit for higher class a current.) That said, I believe it is still better than any opamp based circuit out there as it is.
Yes, there are basically 4 resistors and a trimpot that set the currents on the JC-2, and every version I have seen, starting from the "original" one (JC could say if it is indeed the original) until the last one seem to be different.
So it's difficult to say which to go for. The circuit being a folded cascode makes it even more difficult.
Reducing currents in order to get things cooler might be better for the parts, but certainly not for the audio performance.
Should I go back to the original values (100 & 20 ohms)?
The JC-2 clone apparently choose approximately what Borbely used on his EB604 (post #45): 1K5 & 332 ohms. But EB's second stage were jfets, so currents should be small, me thinks.
Where do I start?