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Old 13th June 2012, 04:27 PM   #11
bcmbob is offline bcmbob  United States
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Another option just discovered.

Symmetric Complementary J-FET preamplifier JC-2 PCB stereo !! | eBay
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Old 14th June 2012, 08:14 AM   #12
erin is offline erin  Australia
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Out of curiousity, have you ever run a square wave through the pre amp?
I'm curious to know at what frequency the square wave starts to visibly start rounding off.
This is an arbitrary request, i know it would have little to do with the subjective sound.
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Old 14th June 2012, 10:26 AM   #13
bcmbob is offline bcmbob  United States
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Quote:
Originally Posted by erin View Post
Out of curiousity, have you ever run a square wave through the pre amp?
I'm curious to know at what frequency the square wave starts to visibly start rounding off.
This is an arbitrary request, i know it would have little to do with the subjective sound.
I just started collecting tools to get into this area. Installed RMAA6 and Visual Analyzer, dug out my signal generator - but it will be a while till I understand what I am doing.

I did shoot off a message to Stanton requesting any publishable data he may have from the development process.
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Old 14th June 2012, 10:41 AM   #14
AndrewT is offline AndrewT  Scotland
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I would expect to seeing "rounding" at 10kHz square wave. That would imply attenuation of frequencies around 100kHz.
I would NOT expect to see overshoot, if the circuit and it's necessary input filter are correctly designed.
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Old 14th June 2012, 11:17 PM   #15
squalor is offline squalor  United States
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I have a few questions

What transformer do you use for this preamp ?

How does the JC-2 compare to the DCB1 ?

Have you tried any parts substitutions to boutique parts ?
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Old 14th June 2012, 11:37 PM   #16
SoIL4x4 is offline SoIL4x4  United States
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Quote:
Originally Posted by squalor View Post
I have a few questions

What transformer do you use for this preamp ?

How does the JC-2 compare to the DCB1 ?

Have you tried any parts substitutions to boutique parts ?
16v to 20v transformer dual secondary. Or, are you asking what VA rating?
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Old 15th June 2012, 01:04 AM   #17
bcmbob is offline bcmbob  United States
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Hey squalor,

Antek AN-0518 right now and have no problems. I intend to try an R-Core at some point primarily because I've never had one and they are reported to be quieter. The toroid itself is silent and there is no hum from the JC-2. The only advantage I could imagine is just cleaner power to drive the circuit.

I've thought about building a DCB1 but the difference in cost would have to better this pre, a bare pot and the Lighter Note for me to make that jump. From what I have read - it doesn"t. Dario will be able to make a direct comparison in a few weeks. He is also working on a boutique BOM. Mine is still a stock unit/kit as shipped from Jim's Audio.
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Last edited by bcmbob; 15th June 2012 at 01:15 AM.
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Old 15th June 2012, 02:27 PM   #18
bcmbob is offline bcmbob  United States
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FYI,

I did some testing this morning. The Lighter Note had been in a different build till last night when I reconfigured it as a stand-alone piece with new wires and RCAs. This was the first time I was able to try it with the FEs. The source was the Mini DAC fed with a computer. I set the volume on both the Ln and the JC-2 to peak ~ 88 db.

The Lighter Note still sounds as clean and pure as ever. There are element of sparkle, airiness and immediacy I have never found with any other device. Bass is full and controlled, mids are punchy and balanced and I get the impression there is nothing being left behind on the source. A pleasant surprise was a lot more available SPL when attached to the FEs. I could not max out the LN pot as was necessary with the V1.2 and V1.3 builds. I would assume that is much the result of the giant 300VA toroids as well as some of Dario’s approach.

The JC-2 held its own, was super close with a few cravats. More than ever I detected some horizontal drift as the volume pot was adjusted. It was serious enough that I wasn’t sure I was getting a truly centered image. I used some audio software to create a mono version of a song with a strong vocal (Paul M’s “Say Say Say”) and played it through the system while adjusting the LN balance pot. The musicality and range of both units was a very, very close match. The stage width was almost identical but the LN had a clear advantage in depth.

I still think the JC-2 is a top choice here for a few reasons.

1. The “Swap & Twist” dance (Dario’s Salsa shuffle) we did on the FE beta run convinces me that proper component choices and placement could recapture the superlative upper end of the Lighter Note. Same for the depth of stage.

2. The stage drift is not present with the JC-2.

3. Cost differences – The JC-2 may be a more likely choice for builders on a tight budget.

I do want to state clearly that I still believe Uriah’s LDR devices are IMO – top notch. He has openly stated a redesign of the Lighter Note is in the works with the goal of simplification and I suspect he will also address the drift. I'm sure some of what I have mentioned can be corrected by adjusting the many on-board trimmers while listening to live signals, as Uriah suggests. To date I've done all my calibrating on the bench with a VOM. Nothing needs to be changed in terms of sound quality and purity. I’m looking forward to his quick recovery and more of his magic tricks.

I’ve also taken the time to read through the other two JC-2 threads and am more convinced than before that this is a great point of departure. It appears Stanton has done his homework and several people are quite pleased with the results.

I did hear from John Curl and his response was similar to that from Parasound. Paraphrasing – “Have at it boys, just remember that the eBay offerings are not my circuits/implementations, nor those of M Levenson or Parasound."

So there we are. There's lots of schematic and components variations on the other posts for those so inclined.
Attached Images
File Type: jpg LN1.jpg (160.6 KB, 305 views)
File Type: jpg LN4.jpg (71.9 KB, 294 views)
File Type: jpg LN3.jpg (921.4 KB, 295 views)
File Type: jpg LN2.jpg (166.6 KB, 282 views)
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Old 15th June 2012, 03:50 PM   #19
squalor is offline squalor  United States
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Reason I ask, I own a 30VA 15+15 Avel from TP that is currently unused. I also have a Antek AS-1215 that I bought for a DCB1. I also have a DCB1 hypnotize PCB. I have not populated it yet because of my FE issues and I don't know who to buy matched sets of 2SK170-BL from.

For my situation, I probably don't need JC-2 or DCB1 . All sources will be within 2ft of the amp and speakers are very efficient. I'm catching flac from the wife again but did leverage a C-note limit after a lick and a promise. Isn't it interesting that wedlock rhymes with headlock.

I had a quick look at the other threads. The conflicts and reasoning of the others are beyond my understanding. Is it true that the original circuit can not be built unless NOS parts can be sourced; the kit Jim is selling is quite different than the Mark Levinson product ? due to adjustments in values to accommodate the newer jfet ?

If I understand right, the JC-2 has something the DCB1 does not; gain. Gain = Loud , loud is good.
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Old 15th June 2012, 05:03 PM   #20
squalor is offline squalor  United States
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Quote:
Originally Posted by SoIL4x4 View Post
if the LN does not work out.
Are you building a Lighter Note or a LDR ? Did you see my reply to your question on the FE thread ? (anything else should I order with my Mouser FE order) I suggested the regi-reg. It's a great way to power a LDR without buying a dedicated transformer for it.
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