Someone please specify Somethings about tubes please?

[RDK]

I'm reading Dave hunters guitar amp handbook. I am having a hard time understanding some things. Help me regain hope.

Can you explain to me what the pins on a tube are referred too. Does each pin have a different name or are they simply just pins? I know he referrs to a cathode often. Where is that on a tube? Is it a visible location. Is it a specific pin number?

First time poster. Really want to understand tube amps but I do not know a single person who can help me.

Thanks

Corey Blythe

[MWJB]

A tube's "pin out", describing which pin is connected to what, is shown on all tube data sheets. However, most amps use the same 9 pin preamp tubes and octal power tubes so...

12A(X/T/Y/U)7 & 5751 preamp tube - pins 1 & 6 are the plates/anodes, pins 2 & 7 are the grids, pins 3 & 8 are the cathodes. Pins 4, 5 & 9 are the heaters/filaments. These are essentially 2 tubes in one, each half (pins 1, 2 & 3 vs. pins 6, 7 & 8) is independent of the other.

6V6/5881/6L6/6550 - pin 1 is unused, pin 2 & 7 are heaters/filaments, pin 3 is the plate/anode, pin 4 is the screen grid, pin 5 is the control grid, pin 6 is unused, pin 8 is the cathode. EL34 have a surpressor grid on pin 1 which is typically tied to the cathode, otherwise the same as the others.

Signal goes in on the grid, out on the plate, cathode connects to ground via a resistor to bias the tube (this is called "cathode bias" and is most common for preamp tubes & power tubes in low to mid powered amps), or in the case of many higher powered amps, the cathode is grounded (maybe a 1ohm resiistor for reading bias current) & a negative voltage is applied to pin 5 to bias the tube, this is called "fixed bias".

[Jazz P Bass]

There are a variety of different tubes available.
Most tube types have a specific purpose.
The tube number is the defining element.
Once you have that information you need the tube data sheet.
Link: electron Tube Data sheets - Search
The data sheet will specify the important parameters associated with the tube.
Such as pin assignment.
Here is an example of a GE 6L6 power tube.
Link: http://www.mif.pg.gda.pl/homepages/f...93/6/6L6GC.pdf

[riz]

It's a steep climb at the first, innit? Hang in there, it'll start to make sense. I don't think about the pins themselves, per se. I just stick'em in the sockets. I think about the internal components as you would see them on a schematic or layout drawing. Study the old Fender drawings, each schematic usually comes with an actual physical layout, a literal translation of the schematic, if you will, and compare the two. Learn to identify the cathode, the plate, etc. Plus, the Fenders are laid out well, and relatively easy to follow.

[jmaf]

Hi RDK, as others have mentioned, the amount of info may seem overwhelming at first but soon you'll find a pattern in most guitar amplifier tubes.

The most visible part of a tube is the plate, it's the anode - the big black or graphite colored structure. The cathode is deep within the tube, on some tubes the cathode is what lights up so you can see it, on others it sits really tight with the heater but does not actually light up.

Here is a tube I took apart last week, so you can see the plate, the cathode, two grids and the heater: http://music-electronics-forum.com/t24780/

On this image: http://music-electronics-forum.com/a...9-dsc_9704.jpg

The plate is top left, the suppressor bean forming structure is next right, then the screen grid, the grid, the cathode and still attached to the tube base, the heater string.

Round, front, are the two mica insulators which cover the top and bottom of the plate. The grid is what allows you to control the tube, it's the golden grid on the photo.

Wkipedia's vacuum tube entry is a great place to start, from the start of the electronic age to present day. Hope this helps.

[Jazz P Bass]

I would like to add that the pin assignment as shown on the tube data sheets is viewed as looking from the bottom of the tube.
So if you are working from the top/ socket side everything is reversed.

[riz]

Wkipedia's vacuum tube entry is a great place to start, from the start of the electronic age to present day. Hope this helps.

Actually, most of the other Wiki entries I've read regarding electronics components are pretty good. One day I sat down and actually made some notes based on the entries for some of the more simple solid-state devices, I think I stopped around JFETS, just to study. Anyway, I would recommend the OP does this sooner than later, too. At least learn what a resistor, diode, and capacitor do, and how they do it, even just as an overview. I waited a long time to start really getting sharp on basic theory, now I'm finally sick of being a big dummy.

[RDK]

Wow

I can't thank you guys enough. That answered all my questions and some more. I think this site will be very helpful. You guys are great.

[RDK]

I was curious. Is there continuity between pin 1&3, and also all the other paired pins? Don't know if I'm making sense. Sorry if so.

[Wittgenstein]

I can't thank you guys enough. That answered all my questions and some more. I think this site will be very helpful. You guys are great.

I suggest reading as many books as you can stand There is a great thread here (http://music-electronics-forum.com/t24553/) with several books you can read for free. I suggest The Electric Guitar Amplifier Handbook by Jack Darr if you have not read it. I also suggest anything by Merlin Blencowe (website here with some great stuff).

I'm still waiting for PDF scans of the entire Ultimate Tone series

[riz]

Well, pins 1&3 on WHICH TUBE type? See above posts re: spec sheets. Often just googling the tube type + "specs" or "pinout" and clicking "images" will pop it right up. It really helps around here to learn to do as much of your own legwork as possible, you'll get a lot more help. Other than that, stick around, grab some good books, and keep asking good questions! The Merlin books are truly awesome once you're ready for them.

[MWJB]

Riz "Well, pins 1&3 on WHICH TUBE type?" 12A#7 tubes as described above.

RDK no there is not continuity, just a relationship depending on the voltages & currents applied to each component. A signal applied to the grid is amplified & comes out on the plate, the tube is usually biased by the cathode. But all current flowing through the tube must leave via the cathode so a signal can be obtained there too. Alterntatively a signal can be applied to the cathode and come out on the plate...they are not directly connected to each other, but influence each other. Pins 1 (plate), 2 (grid) & 3 (cathode) of a 12A#7 are the 3 essential components (hence the term "tri"-ode, and a 12A#7 is "double triode") that a tube needs to work, so pins 1-3 are one tube, pins 6-8 are the other tube. The heaters are common to both triodes, but are not in the audio circuit.

[riz]

MWJB, I don't see where it was specified--I'll take your word for it!

[RDK]

Thanks again guys

After reading al your posts I went back and read the signal chain chapter in this book and felt so much more comfortable and understood so much more. Thanks MWJB!

[hack]

Signal in on the grid (BBQ grill) and out on the plate (dinner plate).