Hello all of you,
Im new overhere altough i visit the website from time to time 🙂.
Have some trouble with a mark levinson jc 2 amplifier wich has a defective line module. The owner (my uncle) managed to get the left module working most of the times by adjusting the pots now and then, probably assuming there was a bad contact. In fact he was messing with the offset so i guess finally one of the fets died since there is still some output but it has lack of dynamics and lesser output than the right one. Also there is a negative voltage of 1.6 volts on input and output stage wich is probably caused by a bad fet. Unpotting the module is a crime and with the lack of partss i have decided its hopeless to fix the module as allready stated in other threads....😀
I came with this idea to make a little pcb with an opamp and i wondered if anyone had good results with a specific opamp and offcourse experience with matching it as much as possible with th the other side. Altough im a tech and my profession is repairing stuff i do not have much experience in building my own circuits and stuff so this will be a first timer regarding to making my own amplifier circuit. And the days of lessons in inverting, non inverting and difference amps are a bit forgotten 😎 A little Help or examples or a complete scheme would be great 😀 my first choise of opamp is a tl072cp. Just because i have a few laying around overhere 😀
Best regards
Olav
Im new overhere altough i visit the website from time to time 🙂.
Have some trouble with a mark levinson jc 2 amplifier wich has a defective line module. The owner (my uncle) managed to get the left module working most of the times by adjusting the pots now and then, probably assuming there was a bad contact. In fact he was messing with the offset so i guess finally one of the fets died since there is still some output but it has lack of dynamics and lesser output than the right one. Also there is a negative voltage of 1.6 volts on input and output stage wich is probably caused by a bad fet. Unpotting the module is a crime and with the lack of partss i have decided its hopeless to fix the module as allready stated in other threads....😀
I came with this idea to make a little pcb with an opamp and i wondered if anyone had good results with a specific opamp and offcourse experience with matching it as much as possible with th the other side. Altough im a tech and my profession is repairing stuff i do not have much experience in building my own circuits and stuff so this will be a first timer regarding to making my own amplifier circuit. And the days of lessons in inverting, non inverting and difference amps are a bit forgotten 😎 A little Help or examples or a complete scheme would be great 😀 my first choise of opamp is a tl072cp. Just because i have a few laying around overhere 😀
Best regards
Olav
Just build a Levinson JC-2 line amp from a modern schematic often put up here on DIY audio. Sorry, when the modules go, there is no easy replacement.
Hi john,
I assumed by reading some threads it was verry difficult to obtain the components that are needed for the modern schematic. So i tought i go the easy way and use an ic. Im afraid yet prety shure i do not have the same skills as the designer ( you) and fabricating a real pcb is out of my league 🙂 well there is a first time for everything offcourse...so using an opamp is really a waste of time?
I assumed by reading some threads it was verry difficult to obtain the components that are needed for the modern schematic. So i tought i go the easy way and use an ic. Im afraid yet prety shure i do not have the same skills as the designer ( you) and fabricating a real pcb is out of my league 🙂 well there is a first time for everything offcourse...so using an opamp is really a waste of time?
You could always buy a JC-2 clone kit from a good affordable source, build it, get it working then if you want to you could upgrade some of the components at a later date. Jims Audio in Hong Kong sell a decent kit version on ebay.
Or it you don't need the gain you could build a buffer stage instead.
Or it you don't need the gain you could build a buffer stage instead.
Thats an idea, but it looks like a 2 channel circuitry and i doubt if it will fit in the case without removing the good working module....
Im going to reread some of the threads and try to obtain the needed components for a single channel and wire them on a experiment pcb board.
This ebay clone kits are "similar" to the original jc-2 circuit at best. I rather would
recommend you build the line stage like I did (and use daily ever since then):
http://www.diyaudio.com/forums/solid-state/10160-need-build-jc-2-preamp-4.html#post2092626
The FETs you can get matched from Spencer (who is a member here, FET Audio | Hi-End Audio Projects ) anything else is easy to get from Mouser for example.
Substituting the line stage with a TL072 is a sin ;-)
recommend you build the line stage like I did (and use daily ever since then):
http://www.diyaudio.com/forums/solid-state/10160-need-build-jc-2-preamp-4.html#post2092626
The FETs you can get matched from Spencer (who is a member here, FET Audio | Hi-End Audio Projects ) anything else is easy to get from Mouser for example.
Substituting the line stage with a TL072 is a sin ;-)
Tnx for the advice. For now i've installed the tl072(yes im a sinner, please dont shoot me for that😉) just plain as if its the module, and buffered the voltage supply with two caps. What a joy to hear the unit play again!!! the tl 072 produces (to my ears) a little bit more presence in midhigh but overall it sounds good especially when listening to a normal stereo situation (instead of comparing left to right). Didn't do
measuring yet but will measure harmonic distortion tomorrow... Maybe i will try some better fet input opamps and if my uncle is willing to spend some money i will try to rebuild the original schematic. Problem is i live in the netherlands so shipping costs for some matched fets will probably be expensive 🙂
Best regards,
Olav
measuring yet but will measure harmonic distortion tomorrow... Maybe i will try some better fet input opamps and if my uncle is willing to spend some money i will try to rebuild the original schematic. Problem is i live in the netherlands so shipping costs for some matched fets will probably be expensive 🙂
Best regards,
Olav
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