New Amp Build. This time, an Express

syscokid said:
What brand and type of orange drops are you using in this build? Are they old Mallory’s?
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Oh! Those! Thanks, J.
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Yes, they are old Mallorys. I'm pretty much done. I ran out of black wire, so I'll need to grab a piece when I can get to Amp Club. Otherwise, it's in the box and ready to have Scott or Tim double check my work, plug it in to the Variac, dummy load, and Oscilloscope, and bring it to life.

As for that 1K 25 Watt resistor, that was the best I could do right now. I bought the boards pre-built. I am toying with the idea of buying everything I need to make a board that looks more like one of Ken Fisher's. I found three of those resistors at You-Do-It Electronics the last time I was there. I need to keep a copy of of the build sheet in my car in case I drive by there again during my commute. They've cleaned out the archives, and stocked a lot of old US and Japanese made resistors and capacitors since covid on the shelves. I need to stock up while they still have some of the good stuff available.


Missing wire from fuse to switch.

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Nice aluminum bottom cover to help fight interference.



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Pretty much what it will look like for now on.





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There will be tubes installed soon....



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Was able to get to Amp Club today. It was the first gathering at Alex’s house, as Tim is getting ready to sell his house in Cambridge.

Scott, who is the lover of all things EL34 jumped right into double checking my work, and starting with simple stuff like making sure all the grounds were good. And because the high quality stainless steel pots had plastic faces, the ground rail connecting the pots wasn’t going to ground. So I made a temporary ground point, and we continued.

Powered up with no blown fuses, and we moved on checking voltages. Ended up forgetting the wires from the bias circuit to the plates on V4 and V5. A bit more soldering, and we were checking more stuff. Finally plugged in some tubes and checked voltages. Everything was within 2-3 volts according to the voltage chart on the Amp Garage.

At that point we disconnected the dummy loads, and hooked up a speaker and guitar. It squeeled like a Pterodactyl. Scott said it’s the most aweful sounding, but easiest thing to fix. Swapped the phase inverter wires, and turned everything back on.

It did everything it’s supposed to do. With just a ballpark bias and an Edwards Les Paul, it sounded pretty good. After I create a real ground point for the bus between the pots and swap the wires to the standby switch, we’ll set it up for real. Hopefully that will be next Saturday.


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So, it looks like I need to flip the standby switch upside down. No matter how I wire it, it works backwards. I wanted to throw some tubes in it with a quick and dirty biasing of -31 volts on the turret between the 220K resistors R16 and R17 to see how it sounds, and to check my recent changes. Other than some minor tweaking and a proper biasing, it sounds really good with an SG plugged into it. I like how you can roll the volume and tone knobs of the guitar up and down to change the varying amounts of clean and filth with no real change in volume. I think when this is dialed in, it will really work well with how I like to play. For only 30 watts, it's pretty darn loud and a lot of fun to play with. Using the Matamp cabinet now, but can't wait to try one of the Marshall cabs with old G12M-25 Greenbacks that are right behind it.

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John sounds correct a loud amp is a happy amp Express is power amp distortion
You can also use 6V6 biased at -29 mA still loud use your Airbrake to tame the beast.
This was the amp I was going to send you Maxine the arctic wolf glad you built one enjoy.

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Between work trying to kill me, getting my mum placed into a nursing home, the oil pump on my car giving up the ghost, and a ton of other less than spectacular crap going in in my life this week, I got a half hour to work on the ground issue I was having tonight. It is now fixed! A couple of new wires on the ground buss to the board and a couple of cold joints on the pots, and it's come to life! If it wasn't so late, I'd give it a thorough flogging. Hopefully that will come over the next couple of nights.

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My mom had a stroke last year not long after my dad passed and if my brother and his wife hadn't stepped up and insisted she move in with them I'd would have been in the same boat. Hope your Moms ok man.
 
SG John said:
So, it looks like I need to flip the standby switch upside down. No matter how I wire it, it works backwards. I wanted to throw some tubes in it with a quick and dirty biasing of -31 volts on the turret between the 220K resistors R16 and R17 to see how it sounds, and to check my recent changes. Other than some minor tweaking and a proper biasing, it sounds really good with an SG plugged into it. I like how you can roll the volume and tone knobs of the guitar up and down to change the varying amounts of clean and filth with no real change in volume. I think when this is dialed in, it will really work well with how I like to play. For only 30 watts, it's pretty darn loud and a lot of fun to play with. Using the Matamp cabinet now, but can't wait to try one of the Marshall cabs with old G12M-25 Greenbacks that are right behind it.

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Like the colour of your Strat!
 
DirtySteve said:
My mom had a stroke last year not long after my dad passed and if my brother and his wife hadn't stepped up and insisted she move in with them I'd would have been in the same boat. Hope your Moms ok man.
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That was very nice of your brother. I finally got mum into a home last Monday. It was plan C, as I wanted one of two homes closer to her house. That way the grandkids and great grand kids could more readilly visit. Instead, she's only a couple of miles from me. She's always been a bad patient, and now is no exception. SInce I'm nearby, I'm expected to be constantly delivering food and snacks. She is in real tough shape, as the chemo for her lung and liver cancer left her mostly blind. Now the cancer has spread to her bones. If I wasn't falling asleep at the wheel driving home from southwestern New Hampshire for work, I'd probably be just leaving there now. SInce one of my nephew's visited today, I asked for a reprieve. I can't wait until I'm finally done dealing with state agencies switching her over from Medicare so that her stay will be paid for, and not me holding the bag.
 
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