It's alive! ALIVE!!!

Just tried my (finally) FINISHED "Egad" amp!!! A dual '96JLH with output protection and remote switching.


For the record, i used two (partialy fixed) Kenwood speakers and a Sony CDP-M11 CD player, fed directly to the amp. I had good impressions with the brief tests i performed earlier, but the amp sounds amazing! I understand now where all the "tube-sound" fuzz came from; i only had experience with guitar tube amps, but there's a roundness and clarity to the sound that just wasn't there with my old SS AB amp. Bass is tight and fast, the highs are crystal clear and i just can't hear any distortion, hum or other nasitnesses. I'm loving it! :) Listening to "Southamptom dock" through it sent shivers down my spine. Harder stuff is handled excelently; Tool & Joe Satriani sounded amazing.

Now, building notes, for anyone interested... the PSU is 4 Elliot' capacitance multipliers, one for each rail (two per amp), with increased capacitances (10000uf input, 3x1000uf "virtual" cap and 2200uf for output). This, and a shielded E-I transformer led to a VERY low noise output... as in "i have to place my ear half and inch from the driver to hear noise" low. I could have killed that too, but my grounding layout prevents this. And this is with a wooden case without internal shielding.
Transistors are ST 2N3055, and drivers are BD2 34/5. I had my reserves about the 3055's, but they just work wonderfully. I probably switch them to Motorolas some day soon anyway. The DC offset control system is the one Geoff suggested, and works like a charm, and the bias current control is the regular '96 JLH. Everything runs HOT (60-70ºC) with one sink per transistor, but that's the fun of it eh? :)

Well, that's pretty much it. I'll be taking pics these days and sharing it with you guys. THANKS A LOT for all the feedback and help! Really!

I'll be working to the preamp now... :)
NickC said:
Congrats on the finish amp
mine is the 69 version with + and - supply running at 3a bias
runs not so hot as yours 40-50
some questions on the amp
what output protection did you use?
what's the remote switching all about?
why did you use the bd234

Mine runs at 2A, and i can get arround 18w out of it before clipping :) Lovely. About the heat, i'm using 3 sinks that came from a welding machine and one i bought, all of them arround 1ºC/W. It's not as bad as it sounds, but yes, it could be cooler. Perhaps some day i'll replace the whole heatsink (it's on the top panel of the amp which can be dettached).

The output protection is a (slightly modified) project by Rod Elliot (#33 if i'm not mistaken), and it's a relay based one. Works great, and has already salvaged one speaker while testing a power supply! It can also be set to mute the amp during turn-on and turn-off. There's also two led vu-meters on the same board, i forgot those before.
About the remote switching... well, the amp uses a small 9v transformer to power a circuit which senses a "remote on" input, and this stays on all the time. Whenever 1.5v or more are applied there, it turns the amp on via a relay. This is so i can set the amp high in place between the speakers and turn on the complete thing from the preamp with a single button, not having to touch the power amp at all.

And the BD234 and 235. Well, they were the only drivers i could get down here that were reasonable priced and fitted the specs of the original ones. Having said so, they work very well, and could be tried instead of all the other proposed devices.

BTW, PassFan, i'm borrowing a digital camera in a few days :)
Lisandro_P, I understand how you feel. I felt the same when I was 13 and built an amp with AD161/162, AC128/01 (transistors made of germanium) and a few BC547! It gave the huge power of 8 watts in mono!

It's fun all the time, never stops! It was fun even today when I listened to my monster phono amp for the first time! You have experienced the fun of DIY!
shadow said:
Very nice amp,but i have some question.
Why you put power switch in right bottom corner?They be better in the middle and on the right side.
As i see whole amp is built with wood.You dont have too much heat inside the amp?

Dunno, it seemed like a good place, so they wouldn't bother. One switch turns on the amp and the other fires up the output protection (in case i want to plug/unplug something without letting the amp cool). In any case, the amp will be switch on remotely, so it's ok i guess...
About the heat, no, not really. The top GETS hot, but the inside sinks don't get over 10ºC above ambient (there are four made out of Al sheet and another 4 salvaged from some PC powersupplies). Just in case i drilled all those vent holes... :)

I love Heinekken btw :D
tschrama said:
Funny picture that last one .. looks allot like my room at total mess .. heineken beer ..... and .. is that a guitar-distortion pedal in the back ?

Nice to see how someone else builds his stuff.. does it sound good?

You wouldn't beleive the mess i have in that desktop, trust me :) I took the pics in a rush! The amp sounds lovely, and i like it more every time i use it. And yup, that's a distortion pedal i built quite a while ago... a soft overdrive. Kinda nice.
Re: Nice Box

chris ma said:
Nice work. I too have some questions. My 1996 JLH 2 mono in a box has 8 TO-3 transistors altogether but I only see 3 TO-3 in yours how come?
I like the copper star point, did you make it yourself? Your wiring scheme is way better than mine.

Thats 4 transistors; the 4th is "hidden" below the smaller sink (check the inside pic). About the star point, i got tired of not being able to find Cu sheet, so i simply bought some cooper piping, cut it open, flattened it with a press and then sanded it and cutted it. Once you heat it enough it can be soldered easy. Tnx!
Well, the final two ones. Notice how i was bitching about the RCA cable; one of the male connectors died on me, so it's a mono picture! :) That cable was cheezy anyway.


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heh, is it just me, or does it seem like almost everyone starts off with a diy guitar pedal?

I recall building a fuzz-face, octavia, and my pride'n joy, a wah pedal, complete with 1/4 inch aluminum rocker and this ridiculous gear mechanism to turn the pot.

Ah, brings back fond memories...

Good job! So, what's next (or should I be asking, what 3 projects are already on your mind...) ;)

I'll raise a glass of good brew to your first amp!

Cheers! And happy listening of course! :cool:
Guitar stompboxes are GREAT... easy, tweakeable and very rewarding. I still use some of the first stuff i made, specially a Big Muff clone... love that chuky fuzz tone :)

So, right now i'm working on a big scale preamp... several inputs & riaa, 10db gain, headphone amps and digital control. That'll keep me entretained for sure.

Thanks a lot! :D
Originally posted by tschrama
Funny picture that last one .. looks allot like my room at total mess ..

Lisandro_P said:

You wouldn't beleive the mess i have in that desktop, trust me :) I took the pics in a rush! The amp sounds lovely, and i like it more every time i use it. And yup, that's a distortion pedal i built quite a while ago... a soft overdrive. Kinda nice.

You blokes just don't know what a real mess is! Look at the random ambience that Circlotron does his inventing in...