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Schematics auto switching. Not sure it's accurate, but that's what I've done. New Grid Voltage Control boards. One trimmer for offset and the other for balance so, both sides are controlled simultaneously. Two jumpers. For 300B/2A3, EL34 and EML 20B-V4. Works al right, quite easy to use. The -510V is achieved with help from GRHV 110V supply. Here is one with Hammond 2VA trafo on board - 2.75in x 2in. New idea - servo controlled grid voltage. Okey, I've tried servo controlled Megatron (with solid state CCS) before and that failed...

Thanks to @JoaMat for posting the 2A3/300B auto-switching filament supply. Although the picture isn’t very clear, I’ve been trying to figure out how it actually works. I roughly recreated the layout (still very preliminary, no routing yet. So please note it may/does contain errors. From what I can tell, the circuit likely uses the voltage comparator on the left to sense the voltage drop across a 0.05 Ω current-sense resistor, distinguishing the different filament currents of 2A3 vs. 300B. The two optocouplers at the upper right appear to be controlled by that comparator and might handle auto-bias adjustment. This is still an early interpretation. I’ll keep updating as I make progress or manage to get a cleaner schematic. That looks really interesting. Can I ask a quick question: Are the two trimmers on top each setting the grid voltage vs. plate current, or are they controlling the grid potential of each EL34 individually? Also, is the 120 V GRHV section meant to supply the bias/grid voltage reference for the output tubes?

highly similar to hev70 sennheiser amp. and by that i mean n-channel fet as current source into another n-channel fet with grounded gate drive. sennheiser amp single high voltage + 600v. this amp +/-400v (initial guess on current way off) output device is infineon imw120r350m1 which has input capacitance of 3460pf. kind of high. there are better parts to use. like this one. C3M0900170D which has input capacitance of 202 pf. calculated output current is about 12.5ma and about 5 watts per heatsink. going to get fairly hot. mc33078 opamps perform very differently inverting and non-inverting. koss esp950 uses the same part in a very different way. much better ways of doing the unbalanced to balanced conversion. power supply about as basic and cheap as possible. the chinese will do this for less than $500. which means that this is infinitely better than the topping eha5. likely sounds better too.

details -> scheme -> psu -> >Max output voltage: 280Vrms It doesn't seem like a very powerful thing. What do you think?

Some damn, dirty hippie with entirely too many guitar amps. Taken in St. Petersburg, FL in 1973 by Joel Bernstein.

I stumbled on this looking for something to listen to now that my queue is empty. I didn't know it existed. It's an interesting combo. All three of these musicians are obviously great. I enjoyed it but their styles didn't mesh all that great for me. ex.

I recently thought about joining ICE...yes, really, but not what you think...not the evil ICE that we see everywhere, but HSI. https://www.ice.gov/about-ice/hsi The ones who investigate the real terrorist networks domestically. Mostly because I have had it with what the Russian plants did to get Trump elected and cement his position there, but also...because it would be easy. I get pinged all the time, recruitment pings on LinkedIn from obviously Russian organizations. One of them even had the audacity to communicate with me in Russian. I got as far as filling out The Questionnaire. There are a lot of questions of the "are you now or have you ever been" variety, but there are also questions that are much more to the point (see attached). I have zero problem killing bad guys. The above video is why. I do realize it's a lot easier knowing who the bad guys are in the above scenarios (they're shooting at you!), and that's kind of what I was imagining, but I do also realize that real life is not so clear cut. I had to bail (on working for ICE) for other reasons. (They wanted to be able to dictate whom I investigated and whom I didn't, being the biggest one.) But I remain staunchly pro-2A, and needed to renew my vow to myself to remain grounded and moral. There may not be people worse than Trump and Hegseth and Miller and the Heritage Foundation et al, but they wouldn't be so bad for life on this planet if it weren't for the extremist MAGA and Russians who are the real terrorists. And armed.

My new guitar idol -- so virtuosic, yet so melodic And a collaboration:

I made stroganoff the other day. I put too much black pepper in, but other than that, it was delicious. It was super spicy, and I wasn't even trying to make it so (the spiciest thing I put in there was black pepper, but I put my usual amount, which is about 1 cubic inch).

RIP Ken Parker, designer of the most advanced guitar ever, the Parker Fly Deluxe. This one hits hard, I regret having to sell all my Parker Fly Deluxes over the course of the last year, they were the most amazing guitars. I just pulled the bass out of storage to fix and sell (it's just the battery compartment).

The pressure gauge looks like one I used for fuel pressure on a 2009 Challenger I tracked for years. Love it! HS

Not For Lack Of Trying by dodie (2025) https://open.qobuz.com/album/ukgy6v7yfn6tb Example: Second time through the album, and like it better than the first time. Released the same day as queen T above. This will have staying power in my queue.

Mobland The same leads as The Thursday Murder Club, But an entirely different , (Guy Ritchie) vibe. Plenty of dodgy and diamond geezers in an underworld setting. Great pacing, visuals, intrigue, banter and twists. And Tom Hardy. Satisfying. MobLand review – Tom Hardy can pull off miracles! And this show needs a few | Television & radio | The Guardian https://www.theguardian.com/tv-and-radio/2025/mar/30/mobland-review-tom-hardy-guy-ritchie

I like them a lot and they are technically proficient but lately I've been a bit off on ported designs as they lack involvement to me. Not enough engagement compared to the greats but, not nearly as bad as the Hifiman Shangri-la mini where the sound just hangs there. I've been meaning to make a proper review of them but this year as a whole has just sucked.

RIP, Dame Jilly Cooper

Nelson Pass apparently mentioned it at Burning Amp last weekend. I wasn't there so don't know what he said about it, but the insinuation was that he was favorably impressed by it.

I like the DAC discussed in the P-F article! Looks like it'll be about $12K USD though......

A colourful Chicken and veggie stir fry.

^ Never understood going after Mann. Have two of her books. Spent Sunday at a lowrider event at Montalvo, likely my last one of 2025. Decided to take two cameras and have a little test between them - a dusty, slow Hassy 500cm with II 50c 50MP digital back & old Zeiss Distagon 50 f/4 T* and a shiny, snap-like Sigma 24MP BF (Beautifully Foolish) with a matching new 35 f/2 Contemporary. For fun shot at 1:1, which most definitely isn’t natural for me. Hassy Sigma

I know these aren't Stax, but have any of you tried Audeze CRBN2 in lieu of the 007s? Bob Katz seems quite enamored with them using one of Birgir's Carbons as the amp. Kinda expensive, but not sure what 007s are running these days either. https://positive-feedback.com/reviews/hardware-reviews/imersiv-d1-dac/

https://theonion.com/travis-kelce-gets-cold-feet-after-listening-to-new-taylor-swift-album/