music, guitars & other obsessions


Tube Amp Test Rig

I finally got around to put together a guitar amp test rig for trying out different designs, the idea came from several experienced builders online, my version is based on a cheap Chinese amp kit, since I don’t have the time nor the skill to make the rig from scratch.

Here is a picture of the chassis before the conversion. The chassis is actually a bit crammed for a multi-stage guitar amp, but it will have to do for now. The chassis came with 5 pre-cut holes for octal tubes, so I ordered some 8-to-9 pin adapter plates to mount the 9-pin dual-triodes that are typically used in guitar amps onto the chassis.

Here is a shot with the terminal strips taped to the chassis with double side tape, not ideal, I may have to drill some holes so they stay put, they already moved around when was wiring up the power supply… Anyway, these strips form the “bread-board”, so I have the ability to change the passive parts easily without having to solder, or if parts substitution can improve the sound, even modify the design to tweak it to suit my own taste.

Side note, I quickly found out why these friggin’ Chinese kits are so cheap (I paid RMB458 for a stereo amp with all the parts) – because they are cheaply made, duh! The chassis is full of sharp corners, the un-finished edges are like shrapnel that can slice the fingers, knuckles if one is not careful, I already got a few cuts, ouch!The first thing I did was to wire up the power section, transformer, rectifier, choke, filter caps, and the heater wires, since the PS is pretty much the same in all the amps. I don’t plan to spend much time tweaking the PS. Although, I may add a switch later for selecting solid state or tube rectifier to see how that affect the sound.

Here is a shot of the heater wiring which unfortunately wasn’t done the “proper way” i.e., twist, measure, cut to length then solder (should have read the online tutorial before I started wiring), I just wire them point to point then twisted the wires… For the actual build, I will definitely do it the proper way!

Tomorrow the whole rig should be wired and functional, I will then start bread-boarding the AX84 SEL. Can’t wait!


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s