DIY EL84 Amp Update!
Wall Of Sound DIY Special Project: Thunderbirds are Go!
The Tubelab.com, Simple Push-Pull (SPP) EL84 Amplifier
PART 1: Cost Breakdown and Parts Ordering Information
By Steve Graham
But before we get right into it, a special thanks to our patron Erik in Seattle for ‘sponsoring’ this project. Thanks to Erik trusting me with some of his hard-earned dough, the build process starts now! All WOS followers will get the benefit of detailed instructions for building their own amps.
It will take a few weeks for the chassis to arrive, and there’s not much I can do ‘til then – it all starts with the boring metalwork. Don’t get in a tizzy, prospective amp builders: just some light labour with a ruler, a file or two, and a drill like the one Miss K is seen holding in the picture above are all that’s required for the chassis work.
Erik is wisely opting for the “Heavy” transformer package. See the attachments below for a description of the transformer options.
Also, thanks to Miss K. for adding a bit of glamour to what can be a subject sorely lacking in it.
No more preamble, straight to business. See the two attachments below. They detail the cost breakdown and parts ordering information. There is a Canadian dollar version for those living in the, “Great Frozen North” and a U. S. dollar version for those living south of the 49th parallel.
Please Note: If you already have, or once you get, the SPP circuit board, DO NOT assemble any parts to it until after the chassis prep is complete. The board is used as a template and only works as such without any parts on it. A few very minor modifications to the board,which will aid chassis layout, also need to be made before parts are added. As well, with the chassis I’ve chosen, some components will go on the top side of the circuit board and some will mount on the bottom.
Attachment 1: Canadian Dollar Cost Breakdown (Revised) (link)
Attachment 2: U. S. Dollar Cost Breakdown (Revised) (link)
…More to follow in the coming weeks.
Hey, Steve!
I’m super excited to hear your impressions of how this unit performs in comparison to the Aikido 12Vac. Kind of two different beasts, I know (pre vs. integrated), but despite my love for my own Aikido build I *could* be tempted to take on yet another of your thoughtfully-planned and -guided projects!
-BN
Thanks for the encouragement Brad. Our patron has requested a power amp only (no volume control or input switching) as he plans to use it with a preamp. I’ve almost always found that a good line stage is better at maximising pace and drive, though this is sometimes at the cost of a small amount of, for lack of a better word, clarity.
As you’ve successfully built the 12Vac Aikido, and if memory serves the Tetra phono as well, the Tubelab EL84 shouldn’t be too daunting. Granted it’s a bit more expensive, due mostly to the higher tube count and three transformers, but the circuit board isn’t any more complex than the 12Vac Aikido. There are more connection points linking the board to the trannies, input and feedback connections but it is fairly straight forward. At any rate, as long as you follow the build instructions, success should be a slam dunk. Please note that I’ve specified a larger than strictly necessary chassis but, in my experience, crowding transformers together is just asking for a hum problem.
Thank you for your continued interest in Wall of Sound.
Regards, Steve
Steve – this and the other projects you’ve done have been quite generous. Nice documentation too. Will follow this one with interest. Hats off to you sir.