[538] Stabilized Thermionic Amplifier

Date: October 16th, 2009 | Comments : [2] | Categories: DIY.

Tube Mu-follower

This is one of the designs in a vacuum tube amplifier patent filed in 1949. The first gain stage (V1 & V2) forms a type of mu-follower.

You can download and read the entire patent to find out more about this circuit.

Mini-Mu
The circuit can be converted to work with jfets, as shown here. Use 1M for R1 and R3, 1k for R2 and a 5k trimpot for R4.

The trimmer should be adjusted until the dc voltage at the source connection of Q2 is 5.0v (+/-0.5v). Start with it set for about 1k between the wiper and Q2’s source.

The circuit has a lot of gain, so it may not be a totally clean boost, as it can run out of headroom rapidly when powered by a 9v battery. If you try this design, let me know your results.

 

2 Responses to “Stabilized Thermionic Amplifier”

[870] RnFR Says: 11:39 am, November 28th, 2009

hey jack!

have you tried modding the whole series mu amp circuit above for FETs? i know that there are similar circuits out there, but just wondering if you had tried this one in particular.it looks to be DC coupled, which i find interesting. also, i have been having some fun lately with cascode circuits. very flat freq response, great for boosts. have you ever experimented with cascodes?


[871] admin Says: 5:45 pm, November 29th, 2009

I did breadboard the version shown above but nothing else yet from the patent.

regards, Jack




 

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