• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

woooohooo!!! 3 working el84 SEs

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well colour me happy!!!

OK it all started a while back when I bumped into this and a couple of other now long-forgotten 'sites. I was looking for a bit of a practical, technical, noisy time-wasting and toobs seemed the perfect outcome.

And how.

So, to put a bit of pressure on and to set a completion frame (always and issue for me as you will see later...) I said to the Style Arbiter "I'll build a little valve amp for each of the kids for Christmas".

Yeah, right says she, knowing full well my tendancy toward procrastination.

SO, how to start??? Where to source all this esoteric gear that was required?

Here in New Zealand we have a local better-than-you-guys auction place called TradeMe at www.trademe.co.nz and from there I got a bunch of old consoles and chassis. Around eight in total eventually at a total cost of less than $100NZD.

After we ceremoniously burnt the woodwork and dust, I was left with a pile of PTXs, OPTs, and a couple of squillion random pentodes, triodes, etc etc., a few multi-section capacitors with cool clamps and stuff, and a pile of old aluminium.

I kept everything but the aluminium and the good humour of the Style Arbiter.


Lets all vote a huge thanks to www.tubedata.org, the boozhound site, and around 70 other bookmarked locations that got me the skills to sort of draw a loadline, identify the bits of glass, figure a PP from a SE trannie and find the easiest, most applicable circuit (www.users.otenet.gr/~athsam/tube_power_amplifier_EL84.htm).

Jolly good - so, inspired by pretty pictures of incredible sheetmetal and timber manipulation, I overestimated my skill and underestimated my needs. Pictures later will show the extent of the problem, but suffice to say that chassis-wise, these are the bastard love children of enthusiasm and ineptitude.

However, a chassis of sorts was developed and the bits randomly scattered across it, itersecting from time to time at places of electrical and mechanical convenience. A number of new bits got bought and soon a somewhat stunned Style Arbiter and myself were listening to REAL MUSIC!!!!!

I couldn't believe it! THe excitement of having music, sounding like it should and coming from the places it should without smoke - what a rush!!!!

Oh, yeah, I could have got all "set the bias to 0.40ma blah blah" but wtf - it already works - don't mess with the Gods of the Circling Electron is my #1 rule. OK, admission time - I had ot adapt the circuit a bit - its perament pentode, and only two supply voltages. I didn't do the 6.3v cathode bias thing as shown on the schematic, cos frankly I didn't understand it. Dont bother explaining cos I'm never going ot change it anyway.

OK, so now I had other distractions. YOu see, I'd discovered the Full Range Driver section of this site, and I had a whole bunch of cool 10 inch, 16 ohm speakers from the old consoles.

Whats a guy to do....

My daughter LURVES her new, way cool, way bassy speakers that Dad made her. The Style Arbiter doesn't but she's such a handbrake I seldom listen anyway. And I'm making the next set with some new 4 inch drivers that will more suit the decor (don't you hate it when they start at you in French???).

So, distraction. THen procrastination. Guy Fawkes came and went (Like 4th of July and Halloween all in one for the English colonies). Christmas was approaching. AAAAARGH. FEAR set in

I mean, the first had all gone so easily, failure must surely follow. Sure enough....

Hum. Big, loud, scary, speaker-destroying hum. And here's me with a DVM as my most sophisticated tool (yeah yeah Eli, I've heard and agree - get the right tools).

Fortunately, my little brother teaches Electrical Technology across town... and has Scopes!!!! Unfortunately, my knowledge was limited, my confidence, initially excessive, dwindled, and I pushed it all into a corner marked "Too Hard" after failing ot find the fault in the first three minutes.

Weeks, including Christmas, passed. THe Style Arbiter complained bitterly about the workshop that encroached on her living area, and promptly left for summer holidays. I was not to join her until "That Mess"was finished.

Divorce threats can be quite motivational don't you think?

SO, brave pills in hand, I dived in again and found... a loose earth wire. Oh bollocks. All that time wasted for the want of a system of checking.

Number three got finished tonight. It went first time.

So, three cute-as-a-button EL84 SE amps at a total cost of less than $150 NZD. Some awesome fun and learning. And a new illness.

Anyone got a good,simple 329B based PP design?

Cheers for your unwitting help and encouragement everyone.
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