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    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

5670 Thoughts?


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The 5670 is a nice little tube. I have assembled several breadboard circuits with it. Take a look at the curves; they look well behaved; straight and evenly spaced. There are many of them around for not much money. They were built to be used in a M1 tank.
All just for Fun!

It's pretty popular in this neck of the woods for line and phono stages, reputedly a good sounding tube. I have a number here and a line stage that uses them that I never finished.. :D (Someday?)
5670 Tube

The 5670 triode is used in S5 electronics K-16LS amp kits, among others, as a phase splitter, and in their add-on 'preamp' and tone circuits. I have built a few of these kits and never had a reliability issue with the 5670 or for that matter the 6005 pentodes used in the power amp section. Cost for a 5670 is $6.00.
The Russian and Chinese 6N3 are also equvalent. Used in many amps and CD plyaers sold on Ebay.

Do you mean 5670 is similar garbage? :confused:


Last edited:


2006-04-17 6:27 pm
Yup, evenly spaced curves make a linear tube. That shared cathode is something to consider when designing, perhaps doubling up triodes for half Ri.

How does that work with a higher current heater? Is the cathode made thicker to have the same emission as the lower current heater or did they do a re-design with alternate electrode distances?
i have 10 pcs 6386 unused...

NOS 6386's are worth their weight in gold! The 6386 is a variable Mu version of the 5670. It was designed for AGC control in RF or IF amplifiers. It was used as the control element in virtually audio compressor made during the vacuum tube era. The Fairchild 660 and 670 are still being used, and the tubes are getting scarce.