Chapter 1 - The Beginning

When I started this project, I really had no idea about  building a tube amp - I only know the plain and simple basics about PP and SET amps.

I wanted to build something that would outperform my Power 1's by Sonic Frontiers in some aspects.  Initially, I was planning to build a PP amp, but was a little more complicated for me to deal with (at the time).  It would have been a fun project and I would certainly make it more powerful than the Power 1's (55WPC), but I was afraid there would be no improvements. Even worse, a downgrade! Thus, I looked into SET amps - a true Class A amp. Most of the schematics found on the web and in books were quite easy to follow.  I know a little bit about reading circuit diagrams and soldering, but I didn't know enough to attack this on my own without assurance that nothing would blow me up and burn down the house in the process! Thanks for the vast amount of information on the internet provided by  DIY'fers, it has made this experience easier and faster to understand.

Now that you know I am a rookie, let's begin the epic journey.

The Plan:

Read Valve Amplifiers, The Principles of Power and various power supply design books.  That actually lead me to more questions than answers.  At the same time, I was surfing the net about tube amps until I couldn't surf anymore, mentally.  All and all, two weeks of hard core research narrowed the search down to the JEL 300B design (see JEL300B schematics).  Initially, I was going to follow it exactly, but I ended up modifying the heck out of it during the construction stage.  In two weeks, I gathered enough information to understand what to do and what not to do, but nowhere the level where I can scratch build something, but modifying can be quite easy when verified by someone who knows what they are doing.  See EAM-300B schematics

Goal:  

To build mono block SET amps with the best parts for under $1000 CDN. Due to lack of experience in this area and being too anal for not buying anything but nearly the BEST, the price shot up to $2000 (not including a $100  mistake - more about it later).  Probably can be done of much less with used parts. 

Parts: 

I bought most of the parts from The Parts Connection (great service and technical help!) and a few from Electrosonic

This was probably the most scariest part of the construction. About 800 dollars in parts and no telling what would happen when I cranked up the variac.  For starters, I tested the PSU (power supply unit) before hooking the rest of the amp up.  Good thing I did because I fried the first Hammond 274BX transformer (short circuit).  It started to bubble and smoked at around 70 volts mains and it smelt like synthetic bacon! During this construction stage, everything was soldered tightly with lots of space for probing, and making sure nothing was shorting. I double checked, triple checked and quadruple checked and cranked up a newer variac I just purchased. It has analog gauges for voltage and current; so if the current spikes, it would indicate a short immediately wherein my old variac just had a voltage dial. It would have been nice if I remembered to use a 1.5 amp fuse in the first place! BTW, I blew the original Sovtek 5U4G because of the same short. Thank goodness it wasn't the Mullard. I like using the Mullard tube over the Sovtek tube because of its soft start characteristic. However, it comes with a price, plus it's a NOS (new old stock) tube.  It costs 3x more compared to the Sovtek 5U4G (takes about 13 seconds before it starts to increase the voltage slowly to 400+V giving the filaments time to warm up.

After I corrected that problem,  I encountered another problem. I got sound, but it was sooooo quiet.  The sound was so clean and pure, and was good enough to drive headphones.  It took me a day to figure what I did wrong, but in the meantime, I just listened to music in mono with my ear pressed up against one JM Lab Daline 3.1 (a word of caution - I don't recommend anyone to use high-end speakers to test prototypes, especially during this stage, however, the first sound I ever heard from this amp came from an old pair of Pioneer speakers).  It turns out I gave the 300B's cathode the filament power supply and vice versa. I thought I wrecked the Valve Art 300B forsure, but it was fine!

Sometime during this Chapter, I was trying to measure current  in the PSU.  I thought I knew what I was doing, but I ended up frying a resistor in my analog voltmeter; in doing so, it created a loud POP; probes went into the air and my hands went flying too. I thought it was the end of me for a split second. Thank goodness for insulated probes. :-).

In this image, everything is working and sounding very beautiful but very bright in the beginning (smoothed out in 20 hours big time and slowly thereonafter). However, I can hear a very loud hum and buzz!! VERY LOUD.  I figure it needed a chassis to eliminate the problem.

I wanted to do a shameful clone of the Cary CAD 1610-SE but I ended up going back to the drawing board. The following images are self explanatory. I thought this was nice at first, but OMG, the tides have changed. Separating the PSU and amp in this configuration didn't reduce the hum at all.  I checked all wiring and appears to be okay

Hammond 274BX runs pretty hot after a few hours of play.

Note the umbilical cord between the PSU and the AMP. I later used 6' power cords for computers to make it look better, but I needed 4 power cords to do the job and it got too ugly.  At the top, you can see a skull and cross-bones.  No relation to the amp. It was something that ended on the floor that I should have picked up a long time ago. HUM reduced slightly, but can be heard 6-8 feet away. Not acceptable folks.

This looks like a joke.

Chapter 2