• 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.

Looking for a simple circuit

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Skitch72

Member
Joined 2004
Looking to build a small project for some kitchen audio. I am looking for a mono circuit that would take iPod output and sum it together and just use the iPod volume for control. Trying to keep iron to a minimum....otherwise open to any designs.


I haven't had much success finding anything that fit this bill...

Anyone have some ideas?

Thanks

Tim
 
S

Skitch72

Member
Joined 2004
Thanks for the suggestion, but definitely want to keep to a tube circuit.

I have plenty of hammond transformers lying around and boxes and boxes of tubes just looking for the right application!

Some added info too...I am thinking this will be driving just a small 4" full range fostex or something similar.

Thanks
 
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mashaffer

Member
Joined 2004
tubiespad.angelfire.com/index.html
I am thinking push-pull to keep the output iron small and a triode pentode combination such as 6BM8 or 6GV8 to keep the tube count and cost down.

Summing the two channels should be as simple as an input resistor in each channel (value would depend on Zout of the pod) connected together at the grid of the input tube. The resistors would keep the pod outputs from seeing a short to ground at any time.

For simplicity I would consider Common cathode VAS into a cathodyne phase splitter. Output pentodes could be either triode, UL or pentode mode with optional (probably not optional in pentode mode) negative feedback (say output tranny secondary to input cathode). Could use LED bias on the VAS to eliminate the cathode bypass cap.

Could pick up either an Edcor OPT or an old console OPT of the proper rating off of the bay. For a kitchen system I would really take a close look at the safety grounding scheme that you plan to use an make sure that it is up to snuff. If your outlets are not GFI fix that too.

If I were you I would also seriously consider putting in a volume control as it is only a couple of bucks for the pot and gives you more flexibility in case you want to connect something without output level control at some point.
 
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Skitch72

Member
Joined 2004
Alright a quick off the cuff inventory:

125SE transformers
125C universal SE/PP transformers
misc chokes 2-4H (know for sure I have some 155H somewhere)
bottlehead PT-1

As far as tubes go, I have quite a few in my collection and couldn't even begin to list them...everything from some 801's to compactrons so if you have any thoughts throw them out!

Thanks

Tim
 
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mashaffer

Member
Joined 2004
tubiespad.angelfire.com/index.html
6EM7, 6LU8 and 6LR8 make some nice SE amps and I think they all like about 5K on the output plates. If you have the right iron would make for some nice 1-3W spuds. 6LR8/6LU8 is discussed in detail here.

http://www.audiokarma.org/forums/showthread.php?t=163886

I am using something like this for my integrated amp project. Any of these could also be used PP if desired.
 
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arhi45

Member
Joined 2003
http://nmwilliam.tripod.com/ecl82.html
ecl82.jpg
 
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