JC-80 eBay PCBs & Power Train

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Welcome to part two of the thread initially titled "JC-80 eBay PCBs". The goals of that thread had been totally fulfilled and, toward the end an incident of rudeness / trolling brought it to a close. Do not post to this thread anything that is in violation of the rules. If you have not read the rules, please do so NOW.

Near the beginning of part one John Curl offered his assistance in selecting components for the JC-80 pcbs available on eBay. Some of those components are rare (the originals specified by JC being totally unobtainable), others difficult to match, and nearly the entirety of the power train left unspecified. With John's help and supporting comments from many others, particularly ticknpop, a power train schematic was laid out that, in John's words

. . .is neither JC-80 or Blowtorch. It is a mixture of the two, better than the JC-80, and somewhat less than the Blowtorch. It should work just fine.

The rationale for most of it can be found in part one but reading part one of the Blowtorch thread is recommended for the serious student. The power train is split across three pcbs and housed in two separate enclosures. It is modular for two reasons. First, a minimal version might include one transformer, one rectifier pcb, one regulator, and a pair of JC-80 preamps. I have not tested that configuration and the current load would max out the Kubota but it could be done. Second, the regulators are subject to heated opinion and can be easily exchanged without much disruption.

Toward the end of part one I discovered a source for the rectifier pcb. That allowed me to specify a BOM for the power train that could be duplicated by any interested reader. In addition, pinnocchio is keeping me honest by building a replica and we will exchange thoughts in this thread. His JC-80s have been operational for some time but he is incorporating the ideas from part one into his power train.

There are many interesting tidbits in the first part such as the following "It requires a good same device match, but the complementary match is more forgiving." Builders are encouraged to follow the BOM delivered with their pcb for the JC-80 and possibly the Kubota (if purchased as a kit). No efforts will be made in this part to elaborate on (or disclose) those BOMs.

Despite John's admonition

Don't 'cheap out' too much. It is pointless to invest your time, if you are not going to make a sonically 'successful' product. Cheap bypass caps, resistors, etc will only compromise an otherwise 'elegant' design.

I have made every effort to minimize costs and offer strategies for sourcing caddocks and matched pairs of jfets. In the end builders will spend at least $300 and likely more than $400 to build two channels of JC-80s with full power trains. Some will spend much more! Keep in mind that John will sell you an assembled Blowtorch for only $2000.
 
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Lets take it from here . . .

For the sake of continuity, the following was posted shortly prior to the end of part one.

Fortunately the choice of regulator is highly modular in the power chain and thus particularly amenable to testing . . . We will soon have participants with regulators ranging from genuine Borbely through Chorbely to Kubota. The SuperTeddyReg has repeatedly been suggested but I have no comparative noise measurement for it. Perhaps we should consider a pair of beefy 24vDC batteries as well.

The Belleson.com site offers a Compare to... drop down that answers a lot of questions. Their Superpower may be lower noise, at around 30uV, than the regulators mentioned previously but, "The Optima Red battery is as good as (ok, ok, we admit it, better than) the Belleson Superpower. Unloaded noise is lower and dynamic performance is just as good."

Based on that, I will comtinue to build the JC-80 and power train including Kubota. Test plan, however, will be radically altered. I will make no attempt to gather statistics but merely report on components used and voltages measured at key points. Whether Kubota is adequate or not will, hopefully, be judged by hooking it to +/-24vDC provided by Optima Red Top Batteries.

I encourage others to use different regulators, continue to suggest ways that the BOM and Power Train might be improved, and note errors. We at least have a baseline for discussion.
 
Just received the rectifier PCBs today. I will put them to the test shortly.

That was fast. I will try to get that collection of parts off to you ASAP. I hope we can move ahead together soon. I did order three common mode chokes this morning (eBay item#380399981066) and plan to use one on the mains and one on each of the two channels. I expect to be overvoltage so plan to use these both to clean the power and drop the voltage.
 
That was fast. I will try to get that collection of parts off to you ASAP. I hope we can move ahead together soon. I did order three common mode chokes this morning (eBay item#380399981066) and plan to use one on the mains and one on each of the two channels. I expect to be overvoltage so plan to use these both to clean the power and drop the voltage.

I'm wondering how much of a cleanup they will do. I might just go ahead and order some since they're pretty inexpensive...

Do
 
You will be surprized that Erno ' PS regulator - from Audio Xpress ( or Amaeture Mag) schematics available in public domain can provide less than 5 uV noise over the entire bandwidth- in case you want. Also you have nice Cap multiplier in JC-80 should help. So go ahead making it first then evaluate the suitablity of any pre regulator ! How Ever John was pointing you to select good components wharever possible on the JC-80. You seem to be on the right track !
good luck with your build
kannan
 
You will be surprized that Erno ' PS regulator - from Audio Xpress ( or Amaeture Mag) schematics available in public domain can provide less than 5 uV noise over the entire bandwidth- in case you want. Also you have nice Cap multiplier in JC-80 should help. So go ahead making it first then evaluate the suitablity of any pre regulator ! How Ever John was pointing you to select good components wharever possible on the JC-80. You seem to be on the right track !
good luck with your build
kannan

I was trying to find the PCBs for those including the Jung regulator or ALWSR but could not find anything to buy a pcb...

I would like to try and compare with what I have.

Do
 
You could try Salas shunts as well.

I will most probably do that. I have a few boards on hand. I have to buy the parts and assemble but I'm sure it is a really good PSU.

I also have one AMB's o22 which is supposed to have lower then 12uVac @ 30V output and lower than 6uVac @ 12V output... These are really good numbers... It does not tell all the story and a listening session will be needed for all of them.

I'm also working with wolfsin on a more custom setup described above.

Ciao!
Do
 
Wow to the low noise, guyz

Wolfsin is sooooo thankful to have Do aboard this thread. Those noise numbers are amazingly better than the Kubota. I went in search of the Borbely article mentioned above but found only supplemental pcb patterns at the Audio Xpress site.

I now forsee a fair amount (re)plugging of regulators, a potentially error prone and costly activity during listening / testing. Are there suitable keyed connectors to reduce the risks?
 
Please send your email id (Wofsin) by PM - I can email you the PDF article ( is in Public Domain and hence no issue using it to make your regulator if you wish) and way to get the PCB pattern as well. I have made that PS regulator from Erno' original kit-
I can even help you with K170/J74 matched pairs sellers. However I do not want many asking me!
Kannan
 
I now forsee a fair amount (re)plugging of regulators, a potentially error prone and costly activity during listening / testing. Are there suitable keyed connectors to reduce the risks?

PS regulators and their connections to such high quality Preamps are sensitive to external noise/magnetic field - so keep the wiring minimal inside shielded enclosure if you want to evaluate them. It is a bit painful but worth all the trouble
 
+ and - 30vDC @500ma to within .0003%

Specifications for the power requirements of the JC-80 may help limit the range of regulators to be considered. Dual rail 30vDC input to the cap multiplier must supply minimum 250ma per rail. The measured noise of the regulator output is present there but is further reduced by the cap multiplier.

The Kubota noise, at <.1mv, expressed as a percentage, is <(100).0001/30 or <.0003% so even if there are quieter circuits delivering 500ma per rail at 30v, the Kubota is pretty impressive. Moreover, the cap multipliers further reduce the noise.

When the kit price of $40 shipped is considered -- WoW!
 
I just asked my friend (He's an audio engineer at a very well known high end audio company) to design me a Jung regulator with LM317 and 337 pre-regulation for the JC-80 preamp. Rectifier will not be onboard...

I need to know if anyone is interested so we could do a group buy.

The regulator and pre-reg would be on one PCB and have both positive and negative rails on it. LM317 and 337 would drop the voltage to 35Vdc then Super Jung to 30Vdc. The noise level should be around 2-4uVac but will be measured by their equipment.

Ciao!
Do
 
We will be right on John's original prescription!

The power supply does need a 337/317 DC regulator after the power supply caps, and the power transformer should be EI, or R core. The shunt regulator should not be necessary. High speed, soft recovery diodes are important, as well.

I was fixated on not doing a custom pcb but the wisdom of your approach is totally apparent with that kind of noise.
 
I just asked my friend (He's an audio engineer at a very well known high end audio company) to design me a Jung regulator with LM317 and 337 pre-regulation for the JC-80 preamp. Rectifier will not be onboard...

I need to know if anyone is interested so we could do a group buy.

The regulator and pre-reg would be on one PCB and have both positive and negative rails on it. LM317 and 337 would drop the voltage to 35Vdc then Super Jung to 30Vdc. The noise level should be around 2-4uVac but will be measured by their equipment.

Ciao!
Do

What company and what's his name?? Just curious because it might be something I want to do.
 
What company and what's his name?? Just curious because it might be something I want to do.

Unfortunately, I cannot disclose this information... He's not really supposed to be doing DIY stuff with his relation with the company...

Let's keep it quiet... ;)

Don't worry, you know the company for sure. But now I'm just teasing you, am I? :)

He's just doing the PCBs and tests for me and does not want to get involved.

Ciao!
Do
 
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