MARK LEVINSON JC2 preamp clone

[Sabaselfsit]

Anyone who has had some experience with either of these two Chinese preamps based of the famous Mark JC2 circuit?

They look a bit different inside. One with very many capacitors - the other very tidy and symmetrical.

https://www.ebay.com/itm/Finished-Hiend-JC2-FET-Class-A-preamplifier-base-on-Mark-JC-2-preamp/163928565943

https://www.ebay.com/itm/Hiend-Reference-MARK-LEVINSON-Mark-JC2-field-effect-Transistor-preamp-C7-28/143675283176

[Barry]

I have no experience of these Chinese clones, but if they are marketing them as the Mark Levinson JC-2 preamp, then the connection is somewhat tenuous. They would best be described as a line stage amplifier, whose circuit topology is based on that of the JC-2.

To start with, the circuit of the amplifier is different to the output module (line-stage amplifier) of the JC-2; the Chinese copy uses cascaded output transistors, as well as several other small differences. There is no balance control, nor a stereo/mono switch. It is unclear if the power supplies follow the design of that for the JC-2, or are a different design to provide similar voltage rails.

John Curl (who designed the circuit; hence the designation "JC") stated that copying the circuit would not be easy as the FETs need to be carefully matched pairs. It is not obvious if that has been done for the Chinese copy.

That said I have no reason to believe either of the Chinese offerings would not sound good, and the construction looks neat and tidy - but don't kid yourself they are an exact copy of the line stage of the Levinson JC-2.

[Sabaselfsit]

Myself (or the sellers for that matter) only suggest that they are based of that design. :) Thank you for the input. It looks nice and tidy - and quality parts are used as far as I can see. It could be an interesting alternative for someone after a new simple active preamp, who don't want to spend the extra cast for a well known alternative (like the Parasound ZCustom Zpre3 and others for example).

If they in fact sound good that is.

[Shovel_Knight]

Personally I would hesitate to buy any Chinese gear that uses rare and expensive parts - and unfortunately almost all through-hole JFETs fall into this category. I once bought a Chinese kit that had fake Motorola 2N3055 transistors which are much more common and a good deal cheaper than audio JFETs...

[Barry]

I doubt the Siliconix semiconductors used in the JC-2 are available now, or even if the company still exists.

Of the two versions cited, I would be more attracted to the first as it looks to use better quality parts.

[Light Dependant Resistor]

The j500 series of jfet current sources are readily available, manufacturers being Vishay and Linear Systems

There are many audio related circuits that have specific need of the ability of of both n channel jfet p channel jfet and fixed value current sources.
You will find them in good phono stages. I presently use 7 jfet devices per main board , 4 of which are J500 series current sources.

I am presently designing a MM phono stage with 6 x J500 series per channel and 3 njfets.

[Barry]

The devices used in the JC-2 line amplifier were Siliconix E175 and E212. The phono stage of the Levinson JC-2 also used the Siliconix E110 p-channel JFET.

[Light Dependant Resistor]

The devices used in the JC-2 line amplifier were Siliconix E175 and E212. The phono stage of the Levinson JC-2 also used the Siliconix E110 p-channel JFET.

Hi Barry
Silconix was acquired by Vishay who provided some of the siliconix range, but the main supplier presently is linear systems http://www.linearsystems.com/product.html
to obtain close to the parameters of the earlier devices, it would be a matter of researching Siliconix datasheets which are on some archive document websites like here:
https://archive.org/details/bitsavers_siliconixdixFETDatabook_24133064 and then matching as best you can to the available devices.