The Red Light District - another PP EL84 amp

SY · 14th June 2006, 05:38 PM

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).

SY · 14th June 2006, 05:38 PM

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.

SY · 14th June 2006, 05:40 PM

The LED array.

SY · 14th June 2006, 05:45 PM

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.

navin · 14th June 2006, 06:21 PM

beautiful SY. I was thinking of mating a small amp like this to a small 4-5" fullrange (tangband, fostex, etc...).

Giaime · 14th June 2006, 06:45 PM

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

pinkmouse · 14th June 2006, 06:49 PM

Trust me, you really don't want to see any pics of SY's constructions...

poobah · 14th June 2006, 06:49 PM

Giaime,

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

SY · 14th June 2006, 07:09 PM

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:

Andrewbee · 14th June 2006, 09:52 PM

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...

14th June 2006, 05:45 PM	#4
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	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. __________________ "...we stumble and get up, we are sad, confident, insecure, feel loneliness and joy and love. There is nothing more; but I want nothing more.” - Christopher Hitchens 1949-2011

14th June 2006, 06:21 PM	#5
navin diyAudio Member Join Date: Jan 2002 Location: Mumbai (Bombay), India	beautiful SY. I was thinking of mating a small amp like this to a small 4-5" fullrange (tangband, fostex, etc...). __________________ ...still looking for the holy grail.

14th June 2006, 06:49 PM	#7
pinkmouse diyAudio Moderator Join Date: Apr 2002 Location: Chatham, England	Trust me, you really don't want to see any pics of SY's constructions... __________________ Al I conceive of nothing, in religion, science or philosophy, that is more than the proper thing to wear, for a while. Charles Fort

14th June 2006, 09:52 PM	#10
Andrewbee diyAudio Member Join Date: Apr 2002 Location: Cayman Islands	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... __________________ None of us are leaving this world alive. Enjoy it responsibly as you may.

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14th June 2006, 06:45 PM	#6
Giaime diyAudio Member Join Date: Oct 2004	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

14th June 2006, 06:49 PM	#8
poobah diyAudio Member Join Date: Nov 2005	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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