How A Valve Guitar Amp Works.

[Chuck]

Great informative post Doc, especially as I'm about to embark on building a tube amp for the first time ever. I'm using a kit from Valve Heaven - the Lamington Junior that uses a 12V plugpack to minimise the risk of higher voltages that a rookie like me could encounter. Should be interesting...

[Dan]

Great informative post Doc, especially as I'm about to embark on building a tube amp for the first time ever. I'm using a kit from Valve Heaven - the Lamington Junior that uses a 12V plugpack to minimise the risk of higher voltages that a rookie like me could encounter. Should be interesting...

I've been thinking about doing similar and have looked at those amps. I don't understand how the 12V plugpack option really makes it any safer. Sure you don't directly need to connect anything to the mains, but the first thing in the circuit is a transformer to convert the 12VAC to 240VAC to bring the voltage back up to generate the +270VDC high tension supply...

[Chuck]

I've been thinking about doing similar and have looked at those amps. I don't understand how the 12V plugpack option really makes it any safer. Sure you don't directly need to connect anything to the mains, but the first thing in the circuit is a transformer to convert the 12VAC to 240VAC to bring the voltage back up to generate the +270VDC high tension supply...

Good point Dan, not that I have any real understanding of these things! Have you seen the weekend courses that Grant at Valve Heaven runs? Two days, $500, kit supplied and supervision! He's based in Adelaide too these days. I used him years ago when he was in Sydney to service an SWR Baby Blue amp I have and he's a really good guy.

[Muzza]

I'll post a pic of an EL84 tommorow, unless someone beats me to it. I THINK one of my Orange amps has EL84's.

Sorry, they're EL34 tubes in both.
I've heard that the Orange Rocker 30 was based on a Vox AC30, so I assumed it had EL84's in them.

EL34 on the left from Orange Rocker 30, EL34BHT on the right from Orange Rockerverb 50 mkII on the right. (I have no idea what the difference is!)



[edit:] here's some EL84's courtesy of Dr Internet...

[Muzza]

As a bonus, for those that are interested, here's the 5 watt single ended harmonica amp I made that I sold for $600.

In the final stages...


...and finished!


(Cab dimensions based roughly on a Blues Junior.)

[Dan]

Good point Dan, not that I have any real understanding of these things! Have you seen the weekend courses that Grant at Valve Heaven runs? Two days, $500, kit supplied and supervision! He's based in Adelaide too these days. I used him years ago when he was in Sydney to service an SWR Baby Blue amp I have and he's a really good guy.

I have seen that and been tempted... but I think I need to build a cab first before I get onto amps.

[DrNomis_44]

Sorry, they're EL34 tubes in both.
I've heard that the Orange Rocker 30 was based on a Vox AC30, so I assumed it had EL84's in them.

EL34 on the left from Orange Rocker 30, EL34BHT on the right from Orange Rockerverb 50 mkII on the right.

That's alright mate, it's good to include some more examples of EL34 Valves anyway, cheers for that.



With those Lamington amp kits that are powered by a 12V plugpack adaptor, there'll most likely some circuitry included to convert 12V AC (I'm assuming) up to a suitable high-voltage to run the Valves properly, I might have a look at these Lamington kits cause they sound pretty interesting.

[wokkaboy]

cool amp Muzza, so you built that from scratch ?

[DrNomis_44]

As a bonus, for those that are interested, here's the 5 watt single ended harmonica amp I made that I sold for $600.

In the final stages...


...and finished!


(Cab dimensions based roughly on a Blues Junior.)

That's a cool looking amp, perhaps that could be a good design template for the PBG guitar amp.

[Muzza]

cool amp Muzza, so you built that from scratch ?

Yep. Cabinet, circuitry, logo, everything, including the amp chassis itself - all made from scratch. (I have access to a sheet metal bender at work.)

The logo on the front is an offcut of brushed stainless. I printed the logo in reverse on the back of some sticky back plastic, then cut it out with a really sharp Xacto knife. Stuck the logo on the stainless and hit it with a few coats of flat black.

When it was completely dry (I allowed 24 hours) I peeled off the stick back plastic and voila... I was pretty pleased with the result. It was going to cost about $50 to get one cut on a CNC machine.