Playing with valves

[(*steve*)]

I've been playing with some funny evacuated glass tubes. And I've been starving their anodes!



These graphs are a bugger to do manually.

 

[(*steve*)]

I may not be making valves, but I have to make valve sockets!



And another view. A wooden 12 pin socket.

When I'm running tests I use a special set of probes I've made.

 

[(*steve*)]

And now I have a pair of valve breadboards. Shown with valves plugged in.

 

[Bluejets]

Steve,
Don't know if you make them because you can but there are some listed in Ebay here in Aus.....
various types ....

http://www.ebay.com.au/itm/5-x-MINI...hash=item51e6ecc017:m:mMkTeHuH-KfGdmf8I-eMbYA

 

[(*steve*)]

It's far cheaper to make them. And faster. And with as many pins as I need (found any reasonably priced 12 pin valve sockets?)

We're in an era when the valves cost less than the sockets.

 

[Minder]

They almost look like dekatron valves, if so we used to use them in counting/timing circuits in the '60's .
Gas filled IIRC.
http://www.electricstuff.co.uk/dekatron.html
M.

 

[(*steve*)]

No, they're evacuated glass IC's, aka compactrons.

 

[(*steve*)]

The Russians are coming!!!!

 

[(*steve*)]

Here are some more pretty pictures.

I'm using a 1J24B the second and third "grids" as the anode, and the anode grounded.

HT is 12V, and the control grid bias is adjusted so the "anode" voltage is 6.5V. An active load is being used which provides a constant 500uA anode current.

Enough of the blah blah. Here's some pictures.

First with a 25mV signal:


Then with a 100mV signal:


3db points are around 500mHz (yes, milliHertz) to 20kHz.

 

[(*steve*)]

And now with a 250mV peak signal (which represents probably the largest reasonable input signal.

 

[Sunnysky]

I've been playing with some funny evacuated glass tubes. And I've been starving their anodes!

These graphs are a bugger to do manually.

Irfanview makes graph snapshots easy
Alt+PrtScn to capture the window
Ctrl+V to paste into irfanview
Draw a rectangle
then either Ctrl+Y to crop
or Ctrl+C to copy
then Ctrl+V to paste here

With practice it takes me 15 seconds using a pinned shortcut to i_view in the taskbar.

Paste only works after<More options> on an edit here.

 

[(*steve*)]

And now with a 1v input signal...



Note the lower gain.

Here is the circuit

 

[(*steve*)]

The cut and paste isn't the issue, its the recording of all the raw data and entering it into excel.

 

[(*steve*)]

Some more measurements last night.

With a 25mV (RMS) input, the THD is around 0.6% with a SNR of about 65dB.

The THD remains almost constant to 100mV input. At 175mV the THD rises to 2.5%, 250mV it's 5.5%, and at 500mV it is 11%.

Measurements were almost constant from 200Hz to 10kHz. Interestingly, THD falls but the noise floor rises (resulting in a lower SNR) at 20kHz and beyond.

These results are obtained with the valve operating open loop.

Interestingly, the valve bias point affects THD fairly strongly. It was previously noted that it affects the gain and bandwidth, and I'm unsure if this is an additional effect or a result of the other effects.

 

[davenn]

interesting results
I have never played around with tubes in this way before
my stuff has always been repair/restoration of old gear


D

 

[(*steve*)]

It is certainly a learning experience.

When I report things like the snr and THD to my musician colleague he encourages me with the explanation that these are expected or even desired.

 

[CDRIVE]

Steve, I found my way here via the AudioGuru topic I started. How the hell have I missed this topic? Like you I've never done any design work with tubes but I serviced boat loads of them back in the day. I did build quite a few vacuum tube designs from the ARRL Handbooks but that doesn't qualify as designing.

You've also been keeping your woodworking skills secret. I love the box joints on your home brew sockets! If you really want to impress me you can claim they're hand cut and chiseled. Is that Boxwood you're using or maybe Holly? I ask because of its cream or white color and also because I can't see any grain.

Chris

 

[(*steve*)]

You've also been keeping your woodworking skills secret. I love the box joints on your home brew sockets! If you really want to impress me you can claim they're hand cut and chiseled. Is that Boxwood you're using or maybe Holly? I ask because of its cream or white color and also because I can't see any grain.

Does it count that I "hand cut and chiseled" the program used to create the cutting outlines for a laser cutter?

The boxes are made from a rare and valuable timber called MDF

 

[bushtech]

lol

 

[CDRIVE]

MDF! Your photos belie that awful truth. Besides using a CNC laser cutter did you also photoshop those pix?

BTW, I've rescinded your master wood worker status because using CNC and Lasers doesn't get you into that fraternity. Though using MDF and actually making that awful stuff look attractive should get you high status in the CNC Laser community!

All joking aside those sockets are both electrically and aesthetically COOL!

Chris