Let's Build a Guitar Amplifier that uses Television Tubes
If you live in the States, it's a tube. If you live in the UK, it's a valve
Just think of all those Television tubes/valve that were left obsolete after the transistor invasion of the Television manufacturing industry in the 1970s. There are still millions of them lying around in tube stashes, in people's lofts and sheds. In fact, there are still thousands of new old stock Television tubes/valves left. Just check out the catalogue for Billington Audio. So, what if I told you that we could use some of these television tubes/valves in guitar amplifier builds. This isn't the first project that I have done with these tube/valve types. In a previous project I used PL84, PCF80, and PCC85. In this new project we are still going to use PCF80 and PCC85, but the output tube/valves this time will be PL508s
We Need a Donor Amp
Now, rather than ordering all the parts for this project, I have decided to use a donor amp. For this project, I chose a Blackstar HT Studio 20 Head. These amp amps can be bought cheap nowadays second hand. The cabinets are sturdy, and the chassis is easy to work with. The power transformers are not great but good enough for an experimental guitar amp build. The output transformer must be changed as it is the wrong primary impedance. We take out the PC board and add a turret board. We then need to order up all the pots and jack sockets.
What about the filament Voltage?
One of the main hurdles to get over is the voltage of filament. Most guitar amplifiers use a 6.3 filament. Television tubes/valves use various filament voltages, though most draw the same current which is 300ma. The way to get round this is to use a separate transformer for the filament voltage and get the voltages exact by using the correct value resistors. You can see how we approach this in the videos.
What about the Circuit?
Some parts of the circuit have been taken from other guitar amp designs. The phase inverter has been taken from the Fender Deluxe Reverb AB763 schematic. The tone stack has also been taken from that same schematic. We fit a Presence control to the also and we use Rob Robinette's website for the circuit. The best addition to this amp is the Morph control. This mod comes from the book: Designing Tube Preamps for Guitar and Bass by Merlin Blencowe. This is a brilliant book. If you are into building tube guitar amps, this book is must have.
More about the tubes/valves used in this amp
So, starting in the preamp circuit, we use the PCF80 tube/valve. This is a Pentode triode. There seems to be thousands of these things in circulation. We use the PCC85 for the phase inverter. This is a two-triode tube/valve. The out tubes are PL508s. These have a dissipation of 12 Watts. They work well in guitar amps. All of these are available with a 6.3 Volt filament, ECF80, ECC85, and EL508. So, you easily use this circuit with the 6.3 Volt tubes.
The Videos Below and the Data Needed
Here are the links to the four videos below. The link to the schematic is also below along with the data sheets for the tubes/valves. This is an experimental project. I am not a full-time guitar amp builder. I am an amp repair tech. I do these projects because I want to provide good entertainment for the YouTube channel and to see if these tube/valves can be used in guitar amps. They are all top quality new old stock tubes, and they are cheap and plentiful It's a shame to see them go to waste. And it makes a change from building the usual run of the mill guitar amps. Just remember to be safe when you are delving into these projects. I hope you enjoy the videos and you take something from them that will help you in your guitar amp projects. Take care all.
Let's Build a Tube Guitar Amplifier Using Television Tubes Part 1
Let's Build a Tube Guitar Amplifier Using Television Tubes Part 2
Let's Build a Tube Guitar Amplifier Using Television Tubes Part 3
Guitar Amp Build with Television Tubes We Make Some Changes And Try a Set of Mullard Output Tubes