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Old 13th Dec 2018, 8:05 am   #41
Diabolical Artificer
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Join Date: Jul 2009
Location: Sleaford, Lincs. UK.
Posts: 7,637
Default Re: 120W PP EL34 amplifier re-born.

Ta Simon. I had to reduce gain as in the original design the amp went into protection and switched off at about 1 o'clock on the vol knob, but I'll bear your circuit in mind.

There are loads of mistakes on mine Andy, I cocked up on a regular basis and made loads of blunders and those joints took weeks, just keep at it and it'll be reet. My workbench is an old window sill, one end screwed onto the extension window sill outside, tother end on a table sitting on a baulk of wood, with an old vice screwed on, tools = chainsaw, an old Stanley plane that cuts wonky, Wilko tenon saw and some old chisel's and a few clamps. I did most of the planing kneeling on a cushion with the wood against the door jam, so it's possible to do reasonable work with not much. Before I made this, my woodwork was more a la' Homer Simpson than Leanardo di Vinci. i think the secret is keeping your tools sharp and checking everything with a good straight edge.

It is parky mate, I'm in a T shirt, norgy and two jumpers and am still cold and that's with the fire on. I have to put a coat on in the workshop and fire up the Tek 585A heater to remove the chill in the morning.

Talking of hum #2 still has hideous hum, I reduced it a lot, found a ground wire grounding one side of the EL34 heaters off, now suspect the ECC82 PS.

There is quite a bit of heat off them - 6 x 6.3v x 1.5A = 56.7 + 2w ish about 60w heater power, times two, strike a light, 120w! That's nuts! They do supplement the Xmas light's though.

Re post # 39, thanks for the explanation mate.

To be honest after listening to them for a bit, I'm a bit underwhelmed. Bass is good and without using too many superlative's is rich and natural sounding, IE a double bass sounds more like a double bass than on my tranny amp, but apart from that I don't know that a valve amp is any better than a tranny amp. Obviously I know there's a lot of BS and hype about hifi, but still... I won't be using them as my everyday amp, my lekky bill has doubled this year, it's likely if I used them all the time I'd be chucking more £'s to the lekky Co.

I've also found this with record deck's, a £5 cheap 70's belt driven jobbie sounds the same to me as a
£500 one. The only time I've been truly amazed by the sound of a bit of hifi kit, is with a Cambridge Audio Azur CD player with twin DAC's; I put a Gorillaz CD in and the sound was a million times better than playing said CD on a PC.

That said although building this amp has been a bit of a trial, I've learned loads and had some fun and am now itching to build another.

Andy.
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