Can you specify which kit did you buy?
If it's not main related, then the noise might be oscillation of some kind.
What is the "JC tip"?
Youse are all deaf and wasting youse time....youse needs one of these 
.
Only joking, feel free to discuss.
Dan.
.Assembled MARZ Preamplifier board with ALPS potentiometer (support 4 ways input)-in Amplifier from Consumer Electronics on Aliexpress.com | Alibaba Group
Only joking, feel free to discuss.
Dan.
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Well, it would be interesting testing and comparing both, and see how they sound.
The Marantz might be improved adding a cascode on the LTP above the FETs.
Apparently it zeroes DC offset with the trimpot above, but does it hold with minimum offset?
Encapsulation of both or dual LSK might secure offset. Interesting design.
The Marantz might be improved adding a cascode on the LTP above the FETs.
Apparently it zeroes DC offset with the trimpot above, but does it hold with minimum offset?
Encapsulation of both or dual LSK might secure offset. Interesting design.
They charge quite a lot for shipping though, almost half the price. There might be some other place to get the same package paying less for shipping.
That's the more complete version that includes input selector. But they were forced to put the selector too close to the transformer, which is not a good thing.
In this case, first thing I would do is to try putting the signal selector away from the transformer. Did you try that?
I'm still not sure which is the tip. The Blowtorch is a much more complicated design.
Max, the 'Marantz' circuit is a pretty good deal, also. It is like a simple discrete version of the AD797.
Why I recommend these sorts of designs is that they are low open loop gain, which implies high open loop bandwidth, can be Class A throughout, and basically balanced, partially cancelling the even order distortion generated by the devices.
NONE of these designs, while a huge bargain FOR THE MONEY, are going to be perfectly sounding, but I do know that the JC-2 measures pretty well, so far. Perhaps there is an oscillation problem that should be addressed, however.
These basic units can be improved, but mostly by improving wiring, caps, resistors, etc. This is an interesting test for hearing the SUBTLE differences that I keep harping about. We could compare a stock unit with a highly modified unit. It is already being done.
Why I recommend these sorts of designs is that they are low open loop gain, which implies high open loop bandwidth, can be Class A throughout, and basically balanced, partially cancelling the even order distortion generated by the devices.
NONE of these designs, while a huge bargain FOR THE MONEY, are going to be perfectly sounding, but I do know that the JC-2 measures pretty well, so far. Perhaps there is an oscillation problem that should be addressed, however.
These basic units can be improved, but mostly by improving wiring, caps, resistors, etc. This is an interesting test for hearing the SUBTLE differences that I keep harping about. We could compare a stock unit with a highly modified unit. It is already being done.
Been there, done that, no counter arguments from me
.I am interested to now what results you get.
Dan.
John, I wish you would stop saying this. If you can't be bothered to read my AES pre-print and understand that NO other op-amp has to date or before incorporated the crossover distortion REMOVAL. Bruce Hofer of AP understands this. People respect your comments on face value, please stop saying the 797 is just another folded cascode like Harris op-amps of the 70's.
The workings of the circuit have been posted here by PMA and jcx in the past so you have no excuse.
BTW I got my JC2 clone yesterday and will gladly run some tests. I needed a second source selector/volume control and this seemed a lot easier than building another myself ($126 delivered). My reference is Walt Jung's AD823/AD815 composite with the Jung super-regulator and a Goldpoint switched attenuator. The build quality of the clone seems very nice and the parts seem genuine.
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Very nearly bought one of those "CJC-2" (=Chinese JC-2), but in the end i decided i didn't need the gain and wanted to build something up from parts, so went with a DCB1 kit from teabag instead.
Now that it's in the hands of some very capable people, i'm intrigued however. Wonder if it couldn't be improved on a bit with shunt regs and greater attention to detail in wiring and perhaps even PCB layout?
Maybe re-john curlify this design somehow, incorporating a few more tricks while keeping it simple?
Now that it's in the hands of some very capable people, i'm intrigued however. Wonder if it couldn't be improved on a bit with shunt regs and greater attention to detail in wiring and perhaps even PCB layout?
Maybe re-john curlify this design somehow, incorporating a few more tricks while keeping it simple?
I am told that the 4580 is the most popular IC audio op amp used today. It is just a supped up 741, but it IS fast enough, etc. 5V/us should be enough, IF TIM is the only thing that you consider important. It shares the op amp approach of other op amps, but I think I would prefer an OP42 over it. What do you think of the OP42?
Scott if you have time to take some measurements and post them it would be great. Mine seems to exhibit a lot more noise than one would expect.
With a 80KHz bw I am seeing about 6mV RMS of gunk ....see fft below.
And unless someone else can do some measurements, I will assume that this is just specific to the unit that I have. It would be nice to have someone else confirm or otherwise
I won't be tweaking this until I can get the basics working well.
P.s. the results below are after mains isolation and AC line filtering.
Ignore the H2 and 5th+ harmonic calcs in the 2 boxes on the right.
Attachments
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