Anyone Clone a JOB?

[lgreen]

Speaking of Gainclones, has anyone ever tried to clone the JOB Circuit?

Here is a link to their website:

http://www.jobsys.com/products.htm

I know that the 47 Labs Gaincard is expensive and has garnered some good reviews so a clone of the same circuit is very interesting. But come on, given the chance to clone the JOB circuit used in the Goldmund Millenium amplifier (and other Goldmund amps), priced at $35,000, one would think that this would be a worthwile effort as well.

link to goldmund products using the JOB circ.

http://www.goldmund.com/old/Millennium/intro.html
http://www.goldmund.com/V4/catalog2/...ltimate/29.htm


Plus the JOB is just as small as the GainCard, so it doesn't look too tough from a complexity viewpoint. Am I missing something? Does anyone have the circuit? A photo of the insides? Any JOBclones out there?

[greg7]

The big question is, what is the Job circuit, anyway? I see no mention of IC's, nor to the internals pictures tell much. The Millenium link mentioned something suggesting IC's but who knows.

[Schaef]

If you ask me, judging from the picture of the circuit, I would throw out a wild guess of some class-D circuit. This isn't based on any hard facts or data, but simply from looking at the picture of the board.

I see two power chips per channel (don't know what they are, transistors, power op-amps, something else totally different, whatever) very few components, and a central heatsink. Its the central heatsink that has me thinking a class-D. If I recall from, who was it? National or Analog Devices that sells the class-D chipset, that the controller chip could get hot. The biggest argument against this theory is the lack of chokes, but they could easily be on the bottom of the board. (Also the relatively low visible component count, but again, only the top of the board is visible)

Am I completely off my rocker with this thought?

[mlloyd1]

I'm thinking the JOB amp design just a very simple, highly tweaked/tuned, fairly conventional circuit. They hide it because they don't want you to figure that out.

Bryston power amp designs products are often held up as an example of a fairly conventional circuit that has been tuned and tweaked well (I'm not so sure about "conventional" after looking at the output stage). You can go to the Brsyton web site and see the schematic. However, I have yet to see or hear about any Brsyton clones. And, folks seem to like the products.

Class D? I really doubt it. Did you really want us to tell you if you're off your rocker

So, who has one to cut open, take pictures and report?
mlloyd1

Originally posted by Schaef
If you ask me, judging from the picture of the circuit, I would throw out a wild guess of some class-D circuit.
....
Am I completely off my rocker with this thought? [/B]

[lgreen]

Here is the image. I don't know that I would call it a switching amp, but it does look like there might be some stuff on the back of the board.

[greg7]

What's the big heatsink in the middle of the board for -- regulators? Otherwise it looks like a typical discrete amplifier, probably MOSFET given Goldmund's heritage and the fact that MOSFET amplifiers can be made very simple. I know Redgum's amplifiers, for example, came right out of a circuit book and have only 2 gain stages and minimal feedback (from the horses mouth). They've tweaked and refined it, of course.

[jam]

My guess is that it is a comp. current feedback amplifier.

Jam

[audionline]

where is the circuit?

Thank you.......

[lgreen]

no one has the circuit, I think that's the point of the post!

[CheffDeGaar]

Well, as far as I recall, the job circuit has been patented by a group of students, and licensed to Goldmund. From what I've read for yonks, Job seems to be a particular topology, very fast they say . It's always encapsulated in a small metallic case and potted. Seems to me that it has been produced in several versions, one for preamps, and others for amps, that should withstand higher currents/voltages (hence a heatsinked case as shown). Maybe these versions also include VAS ??. From photos I've seen in magazines years ago, the preamp version has a "normal" look (no heatsinks/fins).

But I've never never seen a schematic of it... The other thing approching (but with other performances/figures) are Marantz's HDAM modules,and scheamtics can be found...

Sorry not to help at all

Edit : ANd it's absolutely not Class D. To be chosen between A/AB/B, but not more