audio-talk

Brilliant news Paul, well done!

Hercules cluster, single 30s exposure - bit out of focus, sorry.

Narco Avionics - sounds like a Colombian import-export company…

simon wrote: ↑Fri Jan 12, 2024 8:31 pm Amazing. And amazingly little noise for ISO3200.

Yep, the A7S is getting a bit long in the tooth, but it’s still one of the best for low noise, high ISO.

Been having a tidy up on the computer and came across this photo. In 2016 we visited a part of France with pretty dark skies (Astrofarm in Confolens). This was a single 30 second shot of the Milky Way, ISO 3200, can't remember what lens but possibly a Rokinon 135mm. I've just given it a bit of a twe...

I use a pfSense based box both here and at work. Very flexible. The one at work sits behind a 10Gb line. If you have a old PC sitting about that can have two network interfaces it can be reused as a perfectly good firewall. The pfSense box here is on a tiny single board computer, and uses a TP Link...

Thanks for that very comprehensive reply Nick

I just checked my ISP router settings and I'm not forwarding any ports so that's good!

jack wrote: ↑Wed Jan 10, 2024 7:30 pm Although Defender is pretty good, I actually use AVG behind a very good firewall

Hi Nick
Could you give us any quick tips on what to look for in a home firewall solution?
Should I be looking at a hardware device behind my ISP box?
Cheers
Max

Good point, I’d forgotten that, thanks Nick

One last thought - if we use a ccs load, and it’s a perfect ccs, does it matter anymore whether we bypass the cathode resistor? Because the voltage across the resistor won’t change.

Mike H wrote: ↑Tue Dec 19, 2023 7:15 pm May or may not help, but I had considered (perhaps erroneously) 6J5 to be an equivalent for 6SN7, or near enough. In other words I lke the idea of using 6J5, if you've got them. Don't know anything about 76.

Yes, 6J5 is the same as one half of a 6sn7 or 12sn7 or 7n7

Ive never forgotten what Morgan Jones said in Vry’s flat. “Why not use youre main b+ to load your voltage amplifier with High value resistance.” My 211 push-pull amp used that idea, I had around 750 volts after smoothing. The input/gain stage used 50K loads, and the phase-splitter used about 25K to...

Sounds like an interesting evening Nick.
One of my local societies is having a stargazing evening at Rutherford Appleton Lab soon. I think I’ll check it out.

Another option might be 5687 (or whatever else you have that’s suitable) for first gain stage, and xn7 for second stage (you only need the big voltage swing for the second stage). Thinking about the cf stage, do you need the negative bias voltage to be there before the GM70 starts operating? Which m...

Hi Paul Following this with interest, looks like a nice project :) I’m a bit confused by the gain calcs - I thought 6j5 would have higher gain than 5687? (Actually it’s irrelevant because I think I agree with your conclusion that either will work :)) I have some metal envelope 6j5s and should be abl...