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Wolfsin 15th February 2012 05:01 PM

JC-80 eBay PCBs & Power Train
 
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

Quote:

Originally Posted by john curl (Post 2806686)
. . .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

Quote:

Originally Posted by john curl (Post 2777910)
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.

Wolfsin 15th February 2012 06:59 PM

Lets take it from here . . .
 
For the sake of continuity, the following was posted shortly prior to the end of part one.

Quote:

Originally Posted by Wolfsin (Post 2906065)
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.

pinnocchio 15th February 2012 07:20 PM

Thanks for the new thread!

Just received the rectifier PCBs today. I will put them to the test shortly.

Do

Wolfsin 15th February 2012 07:31 PM

Quote:

Originally Posted by pinnocchio (Post 2908117)
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.

pinnocchio 15th February 2012 07:53 PM

Quote:

Originally Posted by Wolfsin (Post 2908129)
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

kannan_s 15th February 2012 07:56 PM

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

pinnocchio 16th February 2012 12:02 AM

Quote:

Originally Posted by kannan_s (Post 2908168)
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

Cal Weldon 16th February 2012 12:45 AM

Moved. In the future, hit the report post so we know you want it moved. I just happened to come upon this.
Thank you.

Wolfsin 16th February 2012 01:05 AM

Thanks to Cal we should all be on the new thread. Wolfsin accidently started it in the wrong forum.

TheShaman 16th February 2012 08:21 AM

You could try Salas shunts as well.


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