The Amp Garage

Here's a pic of a previous build if that helps.

For me speaker choice is always a matter of compromises. In a hypothetical world where I had more money and roadies I would probably use Celestion Blues or Silvers for everything, in 2x12 or 4x12 cabs. But a single 15w Blue is not going to fly for an AC30 and I have never been happy with 2 x el84 ci...

So I discovered why the TB channel was so loud. A 100R slope resistor instead of 100K will do that :shock: . This upside of my goof is that it motivated me to install a PPMIV which works really well even though the dual pot only just barely clears the tube sockets in the cramped chassis. On a final ...

Another consequence of a seriously underloaded PT is that the heater voltages would probably be too high and result in short tube life. You could do a high power tweed twin but it would still be 80 watts. I did one with 100w Peavey iron and it sounded glorious and very different than any AB763 circu...

All done. It turned out that the source of the hum was boneheadedness, as in the failure to ground the output jack. Came in at 32 lbs vs about 50 lbs for my Hayseed 30. I will live with it for a while and might go back and return to some of the stock values I changed to tame the gain. We will see. N...

I was able to knock the hum down a fair amount by pulling the unused 4 and 16 ohm OT wires out of the chassis and cutting them as short as possible (still enough length for a splice if needed later). There is still a fair bit of hum but it's tolerable to me. The next issue was that the TB channel wa...

I answered my own question re. the 220K resistors by trying them - no difference. I also know that the hum is 120hz as per the scope. The hum does not go away when V1 and V2 are removed but does go away when the PI is pulled. I have the pots and preamp grounded to a lug below the input jack and the ...

It passed the lightbulb test so I fired it up this AM. It is loud as #%#, but all is not yet as it should be: 1. It's also noisy as ##$#. I haven't started working on this yet but I expect it will take a while to sort out. 2. Unlike my last build where the Normal channel was too dark and the TB chan...

The Fretting and Staring ™ phase has already paid dividends. I was staring at the filter caps and it occurred to me that they would be more effective if they were connected to something.

Wiring is done. Now comes the all important Fretting and Staring ™ phase of the build where I ponder what I have done wrong before moving to the light bulb test. This phase can take days. After several attempts I final got the ON-ON-ON switch suggested by sluckey installed. A while back I bought a r...

sluckey wrote: ↑Sat Sep 21, 2019 2:09 am Are those four sockets shown above for the power tubes? If so, you'll want to rewire the filaments.

Of course I will. I was just testing you.

I haven't done this in a while and forgot how many mistakes I always make. I didn't wait long enough before clear coating the chassis decals and the whole thing wrinkled up and has to be redone. While waiting for the paint to thoroughly dry and parts to arrive I got started on the power supply. Agai...

xtian wrote: ↑Thu Sep 19, 2019 3:23 pm Is this a tubes-down build? Suggestion: Leave a little room at the edges of the chassis, around the trannys, so you can slide the chassis into the cabinet on rails.

Too late for that but I did install cage nuts so getting the chassis in should be relatively easy.

There will be a single input jack feeding both the Top Boost and Normal channels and I want to be able to select either or both (in parallel) on a switch. I haven’t figured out the details on that or on how to get both channels in phase. Here's how I used a C&K 7211 ON-ON-ON switch to select either...

I haven’t built anything in a while but I am finally getting around to making myself a lighter, cheaper AC30 clone. I made one for a friend back in 2015 https://ampgarage.com/forum/viewtopic.php?f=6&t=27318&hilit=cheap+ac30 and liked it a lot. This time I’m working from the Hoffman AC30 schematic bu...