Hard to Find Information Tube : LS7/CV1660

 I will try to measure vacuum tubes and post here frequently about tubes that hard to find information especially characteristic curve.

Hope this will help many people to discover good and reasonable price tubes on worldwide markets.

First is LS7/CV1660, Directly Heated Triode tube from England, ST shape with brown base.

Can make good sound small power amplifier or preamplifier.

Vf = 4V

If = 0.15A

Va = 150 Volts

Vg = -6 Volts

Ia = 10 Milliamperes

Mu = 12

Rp = 5,000 ohms

Gm = 2,400 Micromhos

Happy New Year 2022 to all of you.

Cheers!!!

Life Easy with Etracer ...

I think in Tube DIY world must know Tube Tracer that can trace tube's characteristic curves.

And now eTracer from Essues is latest smart vacuum tube tracer/tester.

You can access their website and study how it work, 

https://www.essues.com/etracer/

or find many of tube amp designers who using it and post on their blogs.

Essues Tech. supply it in kit (assembly/option), easy to assemble with 1 day man-hour ;)

Connect to computer via USB cable and fully control with program, easily change parameters

like filament voltage/current, plate voltage/current, load line, etc.

     

  Advantage that I really love are

1) match pair or match tube's sections with their characteristic curves not life time!

2) get accurate values to use in real circuit not common values from datasheet provided!

3) best for me is can plot triode curve from pentode tube that cannot find from any source!

Example : Triode curve of EL802 tube that never seen in any datasheet

I've measure and trace many tubes along 3 years that using this smart tube tracer/tester.

And know how easy to design if get the curves so I plan to post characteristic curves 

and typical operation values like plate voltage/grid voltage/amplification factor/plate resistance 

and transconductance of many tubes that common datasheet did not provided or not usable.

To be continue...

Telefunken ELA V311 Transformation Part 1

I've got the first version of V311 power amplifiers more than 10 years. 

Already took out microphone transformers (2 channels in 1 can, using as stereo) 

to use as MC step up transformer, match with many cartridges especially Ortofon SPU.

Very good sound indeed, good dynamic and musical.

But the rest has been keeping like trash until now.

(Maybe) because many reasons that hard to bring them to life.

It is too high power (100W)/ It has 100V line output (not 16/8/4 ohm)/ It's heavy 😆/

It's using expensive power tube (2 of EL156)/ I'm too lazy (maybe the main reason 😁)

But for COVID situation, I'm trying to make almost of my trashes more valuable.

So I plan to re-design circuit, make it can exchangeable between EL12 & EL156.

Bypass microphone amplifier stage also tone control stage too.

Change to fully balanced circuit with input transformer and 1 high gain tube driver stage.

And finally using switching power supply instead of all parts in rectifier stage.

It will get about 20W output power, enough for me & my friend's speakers.

Let's see in next chapter but check the original before doing anything below.

Inside with German built... (from 1950's)

Many parts need custom to fit with standard components but interesting to make it possible.

Cheers!!!