JC-80 eBay PCBs

[Wolfsin]

Originally Posted by kamis

Where complete parts lists could be find?

Hi Kamis,

Thanks for asking. Please accept 'the long answer'.

I wish I could find a BOM on the internet but only a schematic (part of the webpage at the url given above) seems available. Between that schematic and the one attached to post #55 you would have a reasonably complete picture of a workable preamp, but different from the JC-80.

Both of the eBay sellers of JC-80 pcbs are protective of their BOM, one helpfully so and the other angrily so. I believe it would be a breach of good faith if I were to divulge the BOM but that has certainly made this thread less readable. After I have one channel built and working I will publish a BOM for the external PCB. The Kubota BOM and schematic can be obtained with either the pcb or complete kit.

The remark following the MOSFET whose identity you requested was Toshiba Low Noise dual Mosfet, which is obviously erroneous. My first thought was to purchase one pcb from the second seller and compare BOMs but the second seller only sells pairs and, following a heated reply, helped me decide to never patronize his business. I come from a software background and have experienced both the Bazaar and the Cathedral with Linux and Windows. My heart is with open source but I respect the alternative. Errors such as the one noted in this paragraph and omissions such as leaving out the ground on the transformer center tap in the Kubota schematic are more quickly spotted and remedied with open sources.

[dr.strangelove3]

Originally Posted by Wolfsin

Hi Kamis,

Both of the eBay sellers of JC-80 pcbs are protective of their BOM, one helpfully so and the other angrily so. .

Sounds rather hypocritical to me. It is not their design to begin with.
I have bom and schematic from one seller... Just pm me.

[john curl]

I hate to see you flounder, but sometimes it pays to just get the kit, rather than trying to copy it. The is NO WAY that an exact JC-80 can be made today. The output mosfets are NOT in production. The input jfet pairs are discontinued as well and matching what can be found will be problematic.
The power supply 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.

[Wolfsin]

I appreciate your concern: "I hate to see you flounder, but sometimes it pays to just get the kit" Alas, neither vendor offers a kit -- just bare PCBs :-(

"The power supply is . . . better than the JC-80, and somewhat less than the Blowtorch. It should work just fine." Thank you for that clarification. On the plus side, many of the noisey components are external, the transformer is R-core, the rectifiers are soft recovery, the regulator can be purchased as a kit or bare pcb (so unused diodes and caps need not be bought), and the Kubota design is reputed to be easy to build. Certainly this is much better than anything I could have arrived at on my own and the credit goes to John Curl, ticknpop, et. al.

I am sorry if my response to kamis or the seller's positions seem hypocritical. IP law is messy. That may be the kindest thing anyone could say about it. There is nothing patentable about the external pcb I am using and it bears no copyright so I can freely copy it. Had a patent been issued for the JC-80 it would have expired by now and some aspects of this thread would have been different. Correct me if I misinterpreted kamis but I understood from one of his posts that the JC-80 was a trade secret. That is neither a patent nor a copyright, but in some ways the messiest.

I will continue to work toward getting one channel prototyped and tweekable. At that time I will flesh out the schematic and provide a BOM. If no source has been identified for the external PCB I will post very high quality 1:1 scans so that other fanatics can enjoy a documented pathway to building one of the finest preamps ever designed.

[dr.strangelove3]

Hi Wolfsin,
My appologies to you. My remark of hippocrisy was not directed at you! It was directed at the ebay sellers. Them being protective of something that isn't theirs.

Regards

[Wolfsin]

Apology accepted but not required. IP law izMessy!

[Wolfsin]

My trepidation regarding surface mount construction was entirely justified. Poor craftsmen often blame their tools. My shoddy soldering results could be dismissed with but one look at that old iron. Now that excuse no longer works, the iron is new, it is the case of an old "craftsman" trying to master surface mount, bifocals and all :-( After assembling a Bal-Bal 'wire' I realized the JC-80 servos were not a good first (or even second) surface mount project.

That is not to say the Bal-Bal doesn't sing. It really, really sings and I hope the JC-80 will be even better, but I need to slow down, get a magnifier and jig to hold the circuit board and a vial of that water soluble flux sold by S....Fun in Boulder. I have seen it used and the solder just flowed. That must be why my joints aren't as beautiful as opc's :-)

[Wolfsin]

Fairchild irf9510s & 510s are impossible to find, let alone match. Matched sets of 9610s & 610s are available, however. That thanks to Dr.Strangelove.

A carefully packed, sealed box containing sixteen NOS Russian polystyrene caps arrived. Sometimes there is virtually no question of authenticity!

The BAL-BAL 'wire' totally exceeds my expectations, soundwize. Aside from surface mount issues it is a quick and simple build. I have been underestimating the importance of power supplies for a long time and am particularly thankful for the guiding comments received in this thread.

I recall seeing pics of the original JC-80 showing each channel in a separate enclosure. Is that important when the power supplies are entirely separate?

[john curl]

Fairchild 610's and 9610's would OK.

[Wolfsin]

Originally Posted by Wolfsin

I need to slow down, get a magnifier and jig to hold the circuit board and a vial of that water soluble flux sold by S....Fun in Boulder.

Third hand and magnifier arrived and flux is finally back in stock. I will meet a friend in Boulder Wednesday and purchase flux. At that point my excuses will end re surface mount.

5k adjustables are the only part for the Kubota to have not yet arrived. When they show up I will build one power chain to assure that the r-core is properly sized before I order another.

I am well beyond my originally stated objective but it is already years end. Thanks to everyone for your insights and encouragement.