Valve Amplifiers
(or vacuum tube)

Content:

1. Introduction, why this interest of valve technology
2. What different valve amplifiers technology are there
3. What valves can be find today
4. Valve amplifiers of yesterday
5. Valve amplifiers of today
6. Where to find drawings
7. Interesting readings about Valve Amplifiers

Valve Amplifiers

1: Introduction, why this interest of valve technology

Before you proceed reading this, you must know that valve amplifiers working with very high voltage and is very dangerous, 400 volts and higher are common! If it burns your house down the insurance company maybe don't pay you a nickel. And if you die, well then this is the last thing you do in your life! Don't mess with the amplifier by yourself !

Don't try to build anything, only read to get knowledge what it is. You must be a very skilled engineer to work with this!

When I was young in the 1970s I want to build everything and I didn't see any limits what could be built. Cars, telescopes, HIFI equipment and so on. Among other things I found Valve Amplifiers very interesting. I got an Jukebox valve amplifier from an old friend. It had an amplifier with Push Pull output with four P6GT valves. The jukebox speaker had no permanent magnet, it was an electric coil.

I rebuilt that one, rewrapping the transformer from 110 volt to 230 volt as we have in Sweden. When I was finished with it and connected it to a pair of Carlsson OA5 speaker I found that it sound very nice. After a while I replaced it with a solid state amplifier and I forgot the valve amplifier.

Now after all these years I got my curiosity back on these valve amplifiers. I want to know more and started to collect information. I think others also find this interesting so I collect all information her on my homepage.

But, why at all thinking of this old technology? I'm sure it will not have the best sound quality, but very exiting and heavy to look at. That's enough for me to do some investigating.

2: What different valve amplifiers technology are there

Output transformer:
A valve amplifier has very high output impedance from the valves. To connect that to a low impedance speaker there must be an output transformer between. The transformer is very important and expensive.

• https://en.wikipedia.org/ wiki/Valve_amplifier (Valve amplifier, Wiki)

There are two main type of valve amplifier constructions, single end and push pull technic.

Single End:

• https://en.wikipedia.org/ wiki/Single-ended_triode (Single End, Wiki)

Drawbacks are that it draw DC amps through the output transformer and the output power are limited to 5 Watt or a little bit more.

Push Pull:

• https://en.wikipedia.org/ wiki/Push%E2%80%93pull_output (Push Pull, Wiki)

These constructions needs two valves in the output stage, normally deliver from 15 to 20 Watts output.

3: What valves can be find today

An another name for valve is vacuum tube, more common in U.S. I think. Here are some information of how it works:

• https://en.wikipedia.org/ wiki/Vacuum_tube (Vacuum tube, Wiki)

The valves I had in my amplifier was four P6GT if I remember correct. Then maybe one ECC83 valve and a rectifier valve (which I replaced with solid state diodes).

Here is a list of what valves that has been in history:

• https://en.wikipedia.org/ wiki/List_of_vacuum_tubes (List of vacuum tubes, Wiki)

Here I have found where to by them today:

• http://www.vacuumtubes.net/ (Vacuum tubes.net)

I will ad more later.

4: Valve amplifiers of yesterday

Dynaco is one very famous good quality valve amplifier.

List of historic manufactures:

• https://en.wikipedia.org/ wiki/Dynaco (Dynaco, Wiki)
• https://en.wikipedia.org/ wiki/Luxman (Luxman, Wiki)
• https://en.wikipedia.org/ wiki/LEAK (LEAK, Wiki)
• https://en.wikipedia.org/ wiki/List_of_valve_amplifier_designs (List of valve amplifier designs, Wiki)

5: Valve amplifiers of today

Douk Audi and Music Angel seems to be popular.

List of todays Valve Amplifiers:

• http://www.decware.com/ newsite/homepage.html (Decware)
• http://www.doukaudio.com/ (Douk Audio)
• http://www.china-hifi-audio.com/en (Music Angel and others)
• http://www.audionote.co.uk/ (Audio Note)
• http://www.dynakitparts.com/ (Dynakit, kits and spare parts)

What I remember I had problem with hum from the 50 Hz power net. After I rebuilt the transformer to balanced 6.3 AC volt and the mid terminal grounded I get rid of most of that problem. The 6.3 volts power the filament and that is what glow so nice red in the amplifier.

6: Where to find drawings

It looks to be very easy to find drawings of valve amplifiers, here is a list of what I have found:

Warning! Valve amplifiers working with very high and dangerous voltage, don't try to build one if you are not a very skilled engineer!

• http://diyaudioprojects.com/ Schematics/ (Schematics valve amplifiers, DIY Audio projects)
• http://www.keith-snook.info/ schematics.html (Schematics valve amplifiers, Keith Snook)
• http://www.ampslab.com/ vintage1.htm (Schematics valve amplifiers, Ampslab)
• http://www.sarris.info/ main/tube-amp-schematics (Schematics valve amplifiers, Sarris)

7: Interesting readings about Valve Amplifiers

Here I have collected some interesting readings about Valve Amplifiers:

Warning!
Valve amplifiers are working with very high and dangerous voltage, don't try to build one if you are not a very skilled engineer!

• http://www.theabsolutesound.com/ articles/legendary-dynaco-st70-has-been-relaunched/ (Dynaco ST70 will be back!)
• http://www.tube-amps.net/ (Tube amps)
• http://el34world.com/ (El34 World)
• http://www.single-ended.com/ (Single Ended)
• http://diyaudioprojects.com/ (DIY Audio Projects)
• http://ken-gilbert.com/ building-your-own-tube-amp (Building your own tube amp)
• http://www.instructables.com/ id/Building-A-Stereo-Tube-Amp/ (Building A Stereo Tube Amp)
• https://www.youtube.com/ watch?v=QCksgN7kiv4 (RCA Electrons on parade, Youtube)