A Diamond in the Rough: Polishing Heath's AA-30 (AA-111)
- Thread starter dcgillespie
- Start date
Both Schematics here for ref.
bob smog
Creebling at the Turntables
Dug out my AA-30 after more than a decade of being “parked”. Still works and sounds good, albeit with some hum. Changed the can cap and coupling caps 15-20 years ago.
Going to attempt the Dave G. mods as a winter project. Boards are a toasted wreck - might look into getting new ones made.
Going to attempt the Dave G. mods as a winter project. Boards are a toasted wreck - might look into getting new ones made.
That's a good design with nice beefy output transformers. If it were mine, I would cut aluminum plates to replace those PCBs and install Belton sockets and a terminal strip on each one to hold the parts. If this driver circuitry were hand wired, you would never have to touch it again. Good luck with the project, looks like fun!
Jack
Jack
Now 'lurking' on this thread. Planning a 'scratch build' of the unit using OEM Iron..... but that's about it. Will update my progress after starting via a separate thread.
bob smog
Creebling at the Turntables
Finally getting around to this after 10 years. Got the parts this week.
Going to do the mods in stages. PCBs are in very rough shape - considering getting some repos done before doing all the mods. Honestly, this looks like a gut rehab at this point. I replaced the coupling and filter caps around 20 years ago.
My unit has bad 120Hz hum, so I decided to replace R21 with a choke and move the OT leads to the 2nd filter stage. Apparently, the Hammond 156R choke dimensions have changed slightly. It was about 5mm too tall to mount upright and have the bottom cover fit. Ended up having to mount is on its side. No big deal.
Listening to it now. 120Hz hum has disappeared! Still need to do the other fixes, but the choke alone is a huge improvement. Thanks again @dcgillespie
So I just acquired my iron for this build. I got an OE PT, which is still in the shipping box, but I believe both it and the two OTs I have are Stancor branded. I know the OTs are, just not sure about the PT. Anyway, just wondering after re-scanning this thread: Was there ever a new Schemo offered up, or are we still going off the original?
bob smog
Creebling at the Turntables
@Wharfcreek - are you looking for a higher rez scan of the original or one showing the mods?
Bob, Both would be good, but I didn't see one of the completed project that included the mods. Thinking I missed it somehow?
bob smog
Creebling at the Turntables
@Wharfcreek - I haven’t seen a “final” schematic. All the changes are detailed on page 1 and 2. Circuit changes are minor, with most of the benefits coming from the choke and revised grounding scheme.
Im going to go back and re-read it all in detail. But as Im building mine on a fresh chassis using just the OE iron, I'll have some layout options that might prove beneficial.
Ricntucker
New Member
I've thoroughly enjoyed this thread and I'm grateful for the shared knowledge. I found my own AA-30 at a garage sale 20-25 years ago, when real bargains could still be had. At long last I made its recommissioning a priority using this thread as a basis. Here it is on its shakedown, March 16th, 2026. Very pleased with the result; it's as quiet or as loud as the source program requires.
Nice looking amp!
Jack
Jack
bob smog
Creebling at the Turntables
Nice work - tell me more about the pcbs!
Great thread, worthy of lurking…
Ricntucker
New Member
Glad to talk about it!
I did the layout based on the original schematic but with the "DG" changes incorporated, using ExpressPCB "Classic"; also I used RETMA 9AE basing for the triode-pentode (i.e. 6U8A, 6GH8A). Dave does mention that subbing either of these for the 7199 should be accompanied by some feedback-net tweaking -- I might attempt that eventually, but so far with NOS 6GH8As installed it seems to work pretty well as-is.
For no really good reason other than improved appearance with the cover off (to my eye, anyway), I placed the triode/pentode socket on the board centerline, although this did permit marginally-improved isolation of the pentode control grid connection. I messed with the layout for weeks, and even so I feel there is room for optimization, but I got to the point where I just wanted to get the amp wired and working. I sent out the order and had the boards back within a week.
One might wonder why I opted for old-school phenolic PCB tube sockets instead of fancy ceramic ones. In a word, "availability". A chance find at a local thrift shop netted me bag of over 500 Cinch 9-pin sockets -- so I had to do something with at least some of them!
Another thing I did: I think mine must be an early version of the chassis, since it lacks the cooling holes by the power transformer; all there is in the way of ventilation is a pair of small oval slots flanking the 5AR4 (and whatever gaps there are between the transformer openings and their lower bells). So I got some 1/8" spacers for mounting the boards, providing an annular gap around each that I assert provides a bit of a "chimney" effect which ought to keep the 6BQ5s a little happier.
A fun project.
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You couldn't pay me to use Chinese ceramic sockets in my builds. Are you sure those are phenolic, not bakelite?
Jack
Jack