Recent Posts

71

Other Topics / Re: Meme of the day

« Last post by shooter on September 03, 2025, 12:42:37 pm »

...

72

Other Topics / Re: Anybody watching Gold?

« Last post by shooter on September 03, 2025, 12:41:32 pm »

yep, my tea-leaves say by end of year it'll stabilize out about $50.


CCP is on a tear trying to convince the world America n it's dollar are over, Europe is wetting it's pants over Russia n civil unrest, most of south America is run by the cartels, even if we manage to boost the economy here, lots of the moneyed folk are buying up all the tangibles they can get.

73

Tube Amp Building - Tweaks - Repairs / Re: B15N build question about heater elevation

« Last post by Bieworm on September 03, 2025, 11:35:42 am »

Thanks!👍

74

Tube Amp Building - Tweaks - Repairs / Re: B15N build question about heater elevation

« Last post by stratomaster on September 03, 2025, 11:12:47 am »

AI isn't an amp tech.

The bias tap isn't special. It's just a 50v ac supply.

The bias supply itself is a half wave rectifier that conducts only when the negative swing of the AC wave exceeds the diode forward voltage.

Using the bias tap for elevation mirrors this arrangement except for the positive swing.

This means neither supply is conducting simultaneously.  They do not interact, and neither one "knows" the other is there sharing the tap. Furthermore, the diodes themselves provide circuit isolation so the two supplies do not interact even when neither is conducting (there's a brief period where neither diode is conducting and the caps are discharging).

In both the heater artificial CT and the bias supply the current is very low.  The voltages, especially in the case of DC heater elevation, are just a reference. I also spec'd a relatively high fixed resistor to ground to further reduce the current through the elevation reference voltage supply. 

You can also go further and use fusible resistors to act as a safety measure if you're concerned about a heater short taking out the bias supply. But again, the two circuits are diode isolated.

I don't see a downside to using essentially an unused voltage source (positive swing of the bias tap) to create a DC reference in the configuration I've sketched up.

Both amps I've done this on are working perfectly and with less background heater hum than before.

75

Other Topics / Re: Anybody watching Gold?

« Last post by EL34 on September 03, 2025, 10:41:45 am »

The gaps continue

Next overhead resistance is $50

76

Solid State / Re: Unfamiliar with solid state amps, so maybe a dumb question...

« Last post by acheld on September 03, 2025, 10:37:53 am »

Gemini stole that answer from this forum!

77

Other Topics / Re: Split topic

« Last post by shooter on September 03, 2025, 09:37:44 am »

Hosea

 
That Book was my random-read the other night, flipped open the Bible and landed there!

78

Other Topics / Re: Split topic

« Last post by bmccowan on September 03, 2025, 08:19:26 am »

I spent a career in solar energy, owning multiple solar business over 5 decades. I remain a solar enthusiast. But, there is NO WAY that solar farms should displace forest land! Ironically both solar energy and preserving forest land reduce greenhouse gas emissions. So why have them compete? The answer, of course, is greed. Nextera is a huge company involved in solar, wind, hydro, nuclear, natural gas, oil, pipelines, etc. Their only compass points to $. I agree that solar makes sense in smaller scale. It also makes sense as canopies over huge parking lots, over unfertile lands, shared with farmland, stadium roofs, etc. State and local law should restrict the elimination of forest land. Good luck (meant both sincerely and sarcastically)

79

Other Topics / Re: Split topic

« Last post by Platefire on September 03, 2025, 08:03:24 am »

Sounds like the sentiments of Hosea 14:9

80

DIY Layout Creator and Custom Boards / Re: Pro Junior Layout

« Last post by CrasseDeMeule on September 03, 2025, 07:21:44 am »

No problem!
But as a newbie, a quick check from an expert would be safer!
Around the PT, B+, and the choke, I'm not sure 100%

Also as I didn't receive the PT yet, I mybe haven't put the right colours