• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

LS7B Marantz 7 Clone PreAmp


2013-03-21 5:21 am
Hi Folks,

I'm a newbie in tube audio. A friend of mine gave me a modul kit (assembled) of
LS7B PreAmp Tube Marantz 7 Clone.

After I read some threads, I know some of you would say that this PCB/Kit is a "junk" but since I spent no money for it I think I should try it.
I plan to to finish assemblying it as I already all necessary parts but I need some knowledge on how to complete the PreAmp.

1. How do I set the B+ of this PreAmp? Should I do it by turn the VR1 (20 Kohm)?
2. If I should so, should I put all the tubes in place?
3. What is the best value of B+ for it?
(I use 2×EHG12AX7, 1×EHG12AU7 and 2×JAN5687).

Thanks and appreciate any advise from you guys, the tube masters!
Here's the original 7C power supply section, with DC output voltages annotated.


  • Marantz7Cpsu.png
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