Heathkit AA-32- Archeology

 

The Heathkit AA-32

Good ol' Ebay

About 20 years ago I bought a sealed Heathkit AA-23 for about $200 and stuck it in a closet.  I felt an affinity to it because at that time I was working in a building Benton Harbor, MI that some of the Heathkit operations had used.  The last copyright date on the materials I could find was 1969.

Huge respect for people back then that could assemble this as a beginner with limited experience.  Society must have been better and more practical back in the day.

When I opened it everything looked brand new.

I replaced the electrolytic caps with modern equivalents.

The tubes are what you would expect from a 1960's budget kit amp, 6EU7s and the venerable 6GW8/ECL86 combo output tube.

The next pictures show the buid-up of the parts.  I have been building things for quite a while and this thing was a challenge. Part of it was the 34 page step by step instructions with non-intuitive 

"Connect a 4-1/2" wire from lug 1 of terminal strip D (S-3) to lug 1 of terminal strip E (S-2)" 

Looking up pictures of which terminal strip/lugs etc was headache inducing.  Ended up with just using the pictures and the schematic.

I uprated the voltage doubler from the supplied 30uf caps to 200uf caps and UF rectifier diodes.  I also used the Sprague Orange Drop 716p instead of the supplied caps as they looked rather powdery.  I also added a 100uf cap at the end of the chain to keep everything quiet.  The amp has virtually no hum despite the tiny 1" shallow chassis.  Full phono stage and bass/treble controls too.  It sounds like an amp, decent highs and bass for its 8 watt output.  

(One of the 6GW8 tubes did not survive hibernation so waiting on a replacement.)

A build based on Metasonix TX-1 guitar noisemaker with a
SE 6V6 output

It has a life of its own.
 

Maximum 300b (KR 842 VHD)

Pete Millet A2 Driver

Rod Coleman filament supplies

Buddha Camille Constant Current Source

Camille Cascode Constant Current Source (C4S) on the 6SL7

Three Toroidal Transformers 

Four Chokes

MOSFET B+ Regulators

Amphenol Umbilical Connectors

 

304tl - Finished!!!

Finished - Eimac 304tl Single Ended Mono Amps

They have a certain appeal

Construction was as modular as possible

Safety is critical in these amps as there is 1,100 volts on the heat dissipating plate cap

They also put out considerable heat.  Like sitting by a fireplace!

Stereo 6550 - The Dorm Amp

Building an SE 6550 amp with my Daughter

The little Output Transformers just would not do.  These are the full sized Edcors.  Now we have Bass

 Edcor 10 watt SE OPTs are fine as this amp is not asked to perform bass duties

Currently used to drive Klipsch Heresy speakers 80Hz and above.
Low end handled by a NAD2200 and a 12 inch passive subwoofer

It can provide a very high output

Building the 304tl

304tl

The tube cage is one of the most important aspects of this design. Without a safe cage, the amp is completely impractical with over 1000 volts on the heat sink plate connector. This cage uses custom cut glass and aluminum L brackets for construction. Sides and top use a metal screen from the big bin at Lowes.

Sides and top

These amps cover 4 chassis, each weighing over 50 pounds.  Being modular helped with construction but care had to be taken to ensure that the connections were safe and flexible.

Iron

Iron