Introduction

Last year my son and I decided to build a hi-gain guitar amp. We've built a couple of foot pedals but this is our first amp build. My son is into metal so the dual rectifier seemed like a good choice.

Following are some pictures of the completed amplifier. Click the pictures to view a larger image. There are some pictures of the build in progress below.

Front Panel with Case

Rear Panel with Case

Front Panel

Rear Panel

Bottom View

With Speaker

Sound Samples

The following samples were recorded using a Shure SM57 microphone and an 8 ohm Mesa Boogie 4X12 speaker cabinet. The following samples were played through channel 1 (orange channel) set to clean vintage mode. The loop circuit was engaged to generate more gain using the loop send and master controls.

	Cemetery Gates by Pantera
	Hollow by Pantera
	Enter Sandman by Metallica
	Master of Puppets by Metallica
	Orion by Metallica
	Pinball Wizard by The Who
	Seasons in the Abyss by Slayer

The following samples were recorded through channel 2 (red channel) set to modern mode.

	Battery by Metallica
	Enter Sandman by Metallica
	Holy Wars by Megadeth
	Orion by Metallica
	Welcome Home (Sanitarium) by Metallica

Channel 1 (Orange) is bright and creamy but sounds a bit fuzzy. We have to engage the effects loop and use the loop send and volume controls to get enough gain to make the amp loud when running in clean mode.

Channel 2 (red) has a nice clean crunch and lots of gain.

Parts

We ordered the circuit boards, chassis, output transformer and case from Dmitry at Amp Clones. It took a long time to get the parts from Russia but they did finally arrive. Check out this thread for some details about shipping and response times. All the parts we received from Amp Clones were of good quality (see pictures below). The "Decimator" spider logo on the chassis is not standard. Dmitry was out of Amp Clones chassis so he shipped me one of his branded chassis. I believe he builds his own line of amplifiers in addition to running the Amp Clones business. Here's a list of parts we received from amp clones.

We got the power transformer and choke from Hyeboer Transformers.

Most of the remaining parts came from Newark Element 14.

Problems

The cover on the power transformer was too big to fit through the hole in the chassis so we had to cut a larger hole. We took the covers off both the power and output transformers and re-attached them under the chassis. That way only the windings inside the transformer needed to fit through the holes in the chassis.

We wired the feedback circuit out of phase, which caused the power amp to oscillate. The oscillation stopped when we switched the channel to modern mode, which disables the feedback circuit. Switching the grid wires to the power tubes, which are connected to R222 and R223 on the PCB, fixed the problem. See this thread for more details.

One of the relays we installed on the pcb didn't work. We had difficulty removing it with a regular soldering iron. We eventually purchased a de-soldering tool like this one. It was pretty cheap and worked very well if you only need to de-solder a few joints.

We order a lot of parts before we got the circuit board and chassis but it was difficult to know the physical layout of the parts without them. The bill of materials and schematic specified the electrical characteristics but not the physical layout.