Recent Posts

71

Other Topics / Re: Anybody watching Gold?

« Last post by shooter on October 19, 2025, 02:25:41 pm »

October is usually when the stock market takes out the long knives, so with all the market "uncertainty" metals is a good place to park assets til the market stabilizes. my guess $50/oz will be the "standard" through this year  $100/oz is pretty optimistic.  but by 2030 probably low.

72

Tube Amp Building - Tweaks - Repairs / Re: 6M5 6EM5 Valves in Push Pull

« Last post by kagliostro on October 19, 2025, 02:14:53 pm »

Ciao

Franco

73

Other Topics / Re: Anybody watching Gold?

« Last post by scstill on October 19, 2025, 01:57:02 pm »

unless of course its on its way to 100

https://bullionexchanges.com/blog/20-reasons-silver-could-surge-toward-100-per-ounce?srsltid=AfmBOoqrvblMQER0687_IXGgYoBu6VKWqICaTFZ7MauBFa7-UuZbH8_Y

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Tube Amp Building - Tweaks - Repairs / Re: Weird distortion.

« Last post by Dave on October 19, 2025, 01:56:37 pm »

"What does a 1kHz output signal look like (on a scope)?"


Oooh, sorry... I already have half the OT unhooked and the board unscrewed.


Dave

75

Tube Amp Building - Tweaks - Repairs / Re: Planning single channel 6g4a

« Last post by tubeswell on October 19, 2025, 01:47:40 pm »

Can over filtering the bias supply effect tone / response at all?

No, that won’t affect tone

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Tube Amp Building - Tweaks - Repairs / Re: Planning single channel 6g4a

« Last post by bullkelp on October 19, 2025, 01:41:08 pm »

8uF was a standard size cap that was available at the time Leo designed the amp, and for bias supply it’s all you need - a Pi filter is a ‘belts and braces’ approach to eliminating supply ripple in a bias supply (as there isn’t much current anyway). 50uF will also work fine. The bias supply circuit you suggest will work. Yes play around with the tail (27k) if the output voltage isn’t right.

Thanks man
I figured it was one of those historic things and that a bit of over engineering wouldn’t do any harm.
Can over filtering the bias supply effect tone / response at all?

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Tube Amp Building - Tweaks - Repairs / Re: Planning single channel 6g4a

« Last post by tubeswell on October 19, 2025, 01:03:24 pm »

8uF was a standard size cap that was available at the time Leo designed the amp, and for bias supply it’s all you need - a Pi filter is a ‘belts and braces’ approach to eliminating supply ripple in a bias supply (as there isn’t much current anyway). 50uF will also work fine. The bias supply circuit you suggest will work. Yes play around with the tail (27k) if the output voltage isn’t right.

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Tube Amp Building - Tweaks - Repairs / Re: Planning single channel 6g4a

« Last post by bullkelp on October 19, 2025, 12:38:05 pm »

And here is the bias propsed by weber from the concert kitset  (please ignore the SS rec)

Note the weber PT specs show a 48v bias tap
The hammond DEX shows 52.8v

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Tube Amp Building - Tweaks - Repairs / Re: Planning single channel 6g4a

« Last post by bullkelp on October 19, 2025, 12:36:26 pm »

Here is the schematic bias circuit with proposed trim pot

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Tube Amp Building - Tweaks - Repairs / Re: 18W odd power problems

« Last post by Lectroid on October 19, 2025, 10:05:11 am »

HBP:
Thank you for suggesting open caps, and for laying out the math so clearly.  All of the cathode bypass and coupling caps have high resistances; I think they're good.  So we come to the C and D node filter caps.  They are under the board so I haven't tested their capacitance yet. But I've just measured their DCR (if that's the right term here) and both measure around 1500 Ω.  I'll dig them out and unsolder them for a real test--just been avoiding the pain. At least it'll give me a chance to fix a bad layout.

Point taken about the 5U4 delivering higher B+.  I was substituting it for a 5Y3 that I suspected bc I didn't have another 5Y3 on hand.  But I think you're right.  I'll go back to the 5Y3 for the rectifier.  This amp really doesn't need super-high high voltage.

So if I think about such a failing filter cap in the abstract, wouldn't such a cap not filter out as much of the AC ripple at that B+ node?  Would that 'unfiltered' AC appear on the B+ node's voltage now?  Would it be measurable?

Thanks again

PS:  I understand that 'dead' is not a technical term here.  Just writing too fast.  I will work on my posting etiqette.