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Once properly warmed up for an hour or so, the transistor legs sit at around 110, transistor casing at 100 and hottest part of plastic tab at 90 (all in degrees Celsius and with at least +/- 5 degrees or error possible; the IR-gun I use is not the most sophisticated). Definitely too hot to touch, though still a bit cooler than the EL34s . So a bit of margin on both die temperature and what PLA Pro can withstand, though I guess the latter will age quite a bit faster than it would at ambient temperature if I would leave the amp turned on 24/7. I normally don't post pictures because my case work is rather poor, but I found a long exposure mode on my phone which after some experimentation captures the tube glow without leaving the rest in darkness, so I thought I'd make an exception. Pardon the somewhat battered front panel. Should also add that it sounds great.

12 years from this:

Someone noticed the d-_-b airplane 🤣

Thanks for the pin tip. This beyond my understanding. But as I see it, with 400V/22mA the Vgk will be what it will be with offset zero. 12 W with EL34 shouldn’t be much of a problem. My EL61 will also handle that, I hope.

Oh boy. New OL post. Yes, I am going to repost all of them here.

Thanks for your comments, @simmconn. The heatsink gets warm and user is aware of it. I think he is running at 400V/22mA and so far, it seems to work. If it gets too hot than he can’t use this thing - that’s life. For pin dimension. The first version used Neutrik XLR3 pins. They were perfect, diameter slightly undersized. But to short to be soldered direct to main PCB. When looking for brass rod the best I found was 2.5 mm so, I decided to try that. 2.5 mm works with my Teflon tube sockets. The user is informed of that pins are soldered only on one side and if pins come loose, we have to find a better solution or perhaps abandon this thing. I use Addnorth HT-PLA Pro filament. Better heat performance than PLA but not as good as ABS. I’m confident the socket isn’t a problem. It might be a problem with the transistor tab cover. I haven’t thought about the cover until your post - thank you simmconn. Now the user is informed, and he promised to keep an eye on the cover.

I don’t think the non-grata is an issue. It’s just that improving from a Benchmark isn’t easy and most of us haven’t been into audio much lately, or at least enough to offer any insight worth reading.

Unholy carp, it's Ren, doing a different song than "Hi Ren", and well!

About the pin choice. I think this one might be closer to the original tube pins: MPN:6835-0-00-15-00-00-44-0 https://www.mouser.com/datasheet/2/273/MMMC_S_A0004813843_1-2556643.pdf I haven’t ordered it yet to confirm, but maybe it helps you. Also, I’d like to get your advice: At 400 V / 22 mA, would you consider setting Vgk around –95 V a good operating point? I’m also thinking about increasing the static current to around 27–30 mA. From what I see, the EL34 max plate dissipation is ~25 W. At 400 V / 30 mA, that’s only about 12 W, so it looks safe on paper. I’d love to hear your thoughts on this.

I'm persona non grata. Guess I'll stick with with the DAC1.

I didn't watch it, but I imagine they're speaking truth.

This one is for the fathead.

Interesting design! I’d be a bit worried about the thermal and mechanical side of things. The thermal resistance of the heatsink this size is probably going to run above 5C/W without forced air flow. It is going to run too hot to touch at 350V to 400V/20mA (7 to 8W). With 3C/W theta JC on the 10M90S, there is still margin on the die temperature. If I were to design a PCB to be plugged into a tube socket with soldered pins, I’d use slightly undersized pins and whatever copper I can get for adhesion to the board (double layered board with plated-thought holes in 2-mm or thicker PCB), especially if the counterpart is the unforgiving “modern” tube sockets with tulip type spring contacts. Last but not least, when the whole thing gets very warm, I’d use materials with higher working temperature such as ASA or ABS. PLA is probably not going to last very long.

Your presence there is not going unnoticed.

That's wild, as it uses a white Apple logo some 15 years before it became the company standard.

We weren't expecting this. But we got to sample the dark ambient of inscissors

^^Yup.

I like the idea of dessert on the house. As do the local cats

Fresh Fish

It might be a binder of Apple printed documentation for the Lisa.

Via Flickr, two fun bits of history: Edit: Anyone know what is that rectangular thing to the left of the Lisa? Behind the "bar of soap" mouse. I think it might be a software box.

Family started chipping in so I'm now over the 75% threshold. Just a little bit more to go.

Apparently you've never watched the Alien movies.

Well that's reassuring. /s