The Red Light District - another PP EL84 amp - diyAudio
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Old 14th June 2006, 04:38 PM   #1
SY is offline SY  United States
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Default The Red Light District- another pp EL84 amp

I've got a more complete write-up appearing in Bas Horneman's diy magazine, but wanted to put up some schematics for those who want to get a head start. It's easy to build, sounds great, and is a good answer for the common question, "Does anyone know a good 15W amp I can build...?"

First, the basic signal circuitry. Input stage is ECC81 (preferably JJ). Output stage is EL84 (again, JJ is a good choice).
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Old 14th June 2006, 04:38 PM   #2
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The power supply. B+1 is for the output stage and runs 300-350V. The regulator is for the screens (idle current adjustment) and runs from 250-300V. Adjust idle current to 85mA per EL84 pair. B+2 is for the driver stage and is 350-400V.
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Old 14th June 2006, 04:40 PM   #3
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The LED array.
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Old 14th June 2006, 04:45 PM   #4
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I've run this amp on LS3/5A, modified Acoustat 1+1, and NHT Super Zero. The Acoustat needs more power, but the amp didn't do too badly! On the NHT and Rogers, it was close to optimum.
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Old 14th June 2006, 05:21 PM   #5
navin is offline navin  India
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beautiful SY. I was thinking of mating a small amp like this to a small 4-5" fullrange (tangband, fostex, etc...).
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Old 14th June 2006, 05:45 PM   #6
Giaime is offline Giaime  Italy
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Hello Stuart!

Great design, as usual.

But I NEED to see where you mounted all those leds, how, and would like to see a photo of the amp in the dark
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Old 14th June 2006, 05:49 PM   #7
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Trust me, you really don't want to see any pics of SY's constructions...
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Old 14th June 2006, 05:49 PM   #8
poobah is offline poobah  United States
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Giaime,

The photos are restricted by the US NAVY... they are trying SY's amp for night time carrier landing lights.

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Old 14th June 2006, 06:09 PM   #9
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Quote:
Originally posted by Giaime

But I NEED to see where you mounted all those leds, how, and would like to see a photo of the amp in the dark
http://www.diyaudio.com/forums/showt...474#post840474

And a darker shot:
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File Type: jpg amp 003.jpg (31.0 KB, 10999 views)
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Old 14th June 2006, 08:52 PM   #10
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and for the more "creative & artistic" you could change a couple of the red led's for another colour and spell something out... EL 84 POWER
or whatever floats your boat. Why worry about a few milliamps one way or the other for the biasing, whats the worst that could happen?
It may stop working, distort, a runaway tube...
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