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C3M0350120D can be a substitution. 1200V instead of 1700V. Should be good in this role. Otherwise, the new 1700V next generation Sicfet will be released soon as Wolfspeed said will be in stock Q3 2025.

C2M1000170D produced by SUPSIC and Inchange Semiconductor. But don't know if they are reliable or not. PS: Is it possible to replace costly LT1021DIN8-10, something with Negative Shunt Reference (only 2 active pins)?

I think he was very honest about the goals and contributions from corporate donors - it's a project viewers wanted and we viewers are curious about the results, which are somewhat predictable. I'm sure the Walmart bike's (Ozark Trail Ridge) sales will spike as word spreads - I think a good value deserves to be shared around. A better frame, etc. would result in a better bike, but that is super obvious. 🚴‍♂️

{also a reminder that the February release - ARBORESQUE - is still in my queue}

I've discovered that the C2M1000170D is now obsolete and currently out of stock on Mouser as well as several other distributor sites. Has anyone found a good alternative for output transistor for the Carbon? Thanks in advance.

Seth is fantastic; have been following him for SO long.

I'm not surprised this happened but it just makes me sad. They just don't give a shit and sell unsafe trash at extreme prices.

Ok, I stand corrected. The Megatron XL uses a 'hybrid' biasing scheme for the 300B. The grid is adjustable between 0 and 0.99% of B- ('fixed'-biasing), which cancels out less than 10% of the bias generated by the cathode resistor (self-biasing). The voltage between the cathode (K) and the grid (G) is the actual grid bias (Vgk), regardless of self-bias or fixed-bias. In a fixed bias setup, you’d measure between GND and G when K is grounded.

Chicken tinga enchiladas

If the output tube (like 300B) is self-biased, should I measure the voltage between the cathode (K) and the control grid (G1) to determine the actual grid bias (Vgk), and then adjust the trimmer resistor accordingly? I understand that in a fixed bias setup, you’d measure between GND and G1, but in a self-bias configuration, G1 might be at 0V and the cathode elevated — so the true bias would be relative to the cathode, right? Just want to make sure I'm adjusting based on the correct reference. Thanks in advance!

The Megatron final stage is CCS-loaded single-ended output working in class-A. There is no problem selecting operating point that way. However the final stage is self-biased. The grid bias eats up part of the B-, in other words B- is not equal to Eb in the tube datasheet. 20 to 30mA is more than enough for an estat amp. Since 300B has a low mu (2.85), which is about 1/3 to 1/4 of a triode-strapped EL34, the undistorted output voltage will be less than with EL34. But the DHT fame and the aesthetics probably more than compensate for that.

Thanks for the feedback! I wasn’t aware of the differences in operating point strategy between push-pull and single-ended, so I’ll definitely take the time to study the article you linked—much appreciated. Also, if it’s not too much trouble, could you share what grid voltage you typically use for the 23mA setting? And when you went up to around 30mA, did you notice any significant sonic differences? Thanks again for the quick and helpful reply!

I'd say that's a high operating point for this amplifier; the math of push-pull output stages is different from single ended and as long as the transition is smooth you can pick much lower operating points. See for example: https://www.valvewizard.co.uk/pp.html Sorry, I should have remembered; Megatron is NOT push-pull. Megatron (XL) has about 22-23mA through the EL34 current sources. I've tried up to ca 30mA but not beyond that.

Irish feminist country is good country.

This is a couple a months ago but a Woo Audio energizer blew the driver of a SR-X9000.

Thanks for your help, MLA. Another thing I’d like to confirm: based on the 300B datasheet (see chart below), I’m planning to use a 400V B+ supply. According to the curve for Eb=400V, it looks like a plate current of 70mA corresponds to a grid bias around -85V. Would you consider this a good operating point?

I listened to that album before going to sleep every night for probably 5 months.

Putting $6,000 of parts on a Walmart bike:

Six worthless posts in the first 30 minutes on Head-case is a recipe for pain. If there is still a welcome message, I suggest that you read it and heed it.

Rest in peace big guy.

> "Ohhh you like electrostatics so you don't like bass!" The humble HD600 sighs in relief, as STAX takes the blame.

Oh, and they're running on the SRM-Xh. I don't even know if they're re-capped but they seem to work well. Should I be concerned about my headphones blowing up if a cap dies?

“Wendt showed up as Norm over the years on St. Elsewhere, Wings, The Simpsons, Family Guy, Frasier and The Tortellis and as himself on Seinfeld and The Larry Sanders Show. He also had recurring roles on The Naked Truth and Sabrina the Teenage Witch and guest-starred on other series like Alice, Soap, Hart to Hart, Becker, Hot in Cleveland, Columbo, Harry’s Law, Fresh Off the Boat and The Goldbergs.“ That’s pretty impressive. Also in Hairspray on Broadway.

I think that's going to be the least of your concerns if you look on other forums

Ohhhh so that explains their gamer planars