Although I've been servicing, modifying and cloning amps for some years, I've just prototyped my first "original" (ahem!) design.
I'm blessed with some fantastic sounding clean fendery amps, so I was shooting for something quite different, built into a Princeton chassis and cabinet which can take a 10 or 12 inch speaker.
The first prototype is heavily influence by the Divided by 13 click channel, with an AC15-like power section. I originally imagined using EL84s, but got my hands on some cheap Mullard EL821s and decided to try those instead. First impressions, it's definitely not a Fender... plenty loud, warm despite having plenty of high end, and not a lot of clean headroom. Overdriven, it sounds good but not great - plenty of experimentation and optimisation ahead.
I've built versions with and without the cathode follower, I'm not yet sure which I prefer.
Just posting here to share and feel free if you spot any beginner errors, or have experience building something similar, feel free to share any ideas.
I know I'm running the EL821s far above the 275 plate rating, as they're plentiful and inexpensive I'll take the risk for now.
First scratch build - looking for feedback
Moderators: pompeiisneaks, Colossal
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First scratch build - looking for feedback
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- Posts: 4
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Re: First scratch build - looking for feedback
(With power supply)
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Re: First scratch build - looking for feedback
here is one half of 12ax7 used for not important function at all (any tube can be used for follower), and other half is unused?
so design is out of optimum?
so design is out of optimum?
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- Posts: 4
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Re: First scratch build - looking for feedback
Yes, one half of the 12AX7 is unused if I keep the cathode follower.
I'm using a 12AX7 for the 100v cathode-to-heater rating.
I'm using a 12AX7 for the 100v cathode-to-heater rating.
Re: First scratch build - looking for feedback
You don't need the CF. Try it without and see what you think.
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Re: First scratch build - looking for feedback
Thanks - I know it's not needed for impedence reasons in this circuit - I tried it with and without. Clean it's really close, maybe a bit snapper without the CF. Dirty the CF definitely seems to smooth things out.
Re: First scratch build - looking for feedback
Easy to add a voltage divider off of the plate supply for some heater elevation then you can use whatever. Added bonus of discharging your filters when unplugged and potentially less hum. Could also elevate heaters at power tube cathode, just not as much. Or, leave it as is and feel superior to all of us with the mental illness that doesn't allow an unused triode.landmarker wrote: ↑Wed Feb 21, 2024 6:25 pm I'm using a 12AX7 for the 100v cathode-to-heater rating.