Recent Posts

11

Tube Amp Building - Tweaks - Repairs / Adding an LED or neon lamp to tremolo

« Last post by dickjonesify on March 11, 2026, 05:28:21 pm »

So, I added this tube tremolo circuit to my amp, design courtesy of sluckey…



I want to add an LED as a visual indicator. I attached a red one between the cathode and ground, parallel to the Vactrol. It works but it’s quite dim. There’s only like 1.7VDC there.

Is there an easy way to adjust the voltage at the cathode? Spoiler alert: I already tried changing the cathode resistor and it didn’t seem to do anything (for the LED anyway).

Another thought was putting a neon bulb in series with the plate of the oscillator. It’s around 200VDC. Might be a better aesthetic choice anyway since the amp has neon bulbs for standby and power already.

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Tube Amp Building - Tweaks - Repairs / Re: Shielded Jack

« Last post by Willabe on March 11, 2026, 04:45:37 pm »

Very nice work. 

Switchcraft used to make/sell a shielded 1/4" jack.

It was in their catalog.

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Tube Amp Building - Tweaks - Repairs / Re: Shielded Jack

« Last post by Willabe on March 11, 2026, 04:38:19 pm »

Very nice work. 

Switchcraft used to make/sell a shielded 1/4" jack.

It was in their catalog.

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Tube Amp Building - Tweaks - Repairs / Shielded Jack

« Last post by astronomicum on March 11, 2026, 04:28:55 pm »

Just finished a restoration of an Omega (Japanese) guitar amp from the late 50s. The amp is equipped with a shunt jack prior to the output driver circuit to redirect the preamp out (called Output). I had a persistent 9mV hum traced to this circuit. Yes, not bad, but annoying. And while rewiring the jack with shielded cable did not get rid of the hum, bypassing it did. Feeling the issue was the jack itself, or maybe more accurately, the jack position, and since removing or moving the jack was not an option, I went looking for a shielded shunted jack. Well, you probably know how that turned out.

So I decided to see if I could put one together. I found some good quality shunted square body jacks on E-bay, and out of aluminum flashing, razor blade, Dremel, and micrometers, constructed a shield. To my delight, after installing the jack, the amp now has only 3mVs of hum.

Something to keep in mind for the toolbox.

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Tube Amp Building - Tweaks - Repairs / Re: 5879 amp favorites?

« Last post by mountainhick on March 11, 2026, 03:34:24 pm »

Gibson Les Paul GA 40

https://el34world.com/charts/Schematics/files/Gibson/Gibson_les_paul_ga_40.pdf

Sorry, I miss ed you want to change from the GA 40

Franco

No worries, Yep been there, done that, and will again, but with 6SJ7s.

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Tube Amp Building - Tweaks - Repairs / Re: 5879 amp favorites?

« Last post by mountainhick on March 11, 2026, 03:32:35 pm »

This one is worth doing
5879 Blues Bassman

I have found another version in the Jschem forum, looks potentially desirable, and easy enough to adapt to 6AQ5s.

TIMBO, what's your take on a 12AT7 as PI in that design? Have my own thoughts, but would like to hear others' take on it.

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Tube Amp Building - Tweaks - Repairs / Re: 5879 amp favorites?

« Last post by kagliostro on March 11, 2026, 03:07:25 pm »

Gibson Les Paul GA 40

https://el34world.com/charts/Schematics/files/Gibson/Gibson_les_paul_ga_40.pdf


Sorry, I missed you want to change from the GA 40

Franco

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Tube Amp Building - Tweaks - Repairs / Re: 5879 amp favorites?

« Last post by TIMBO on March 11, 2026, 02:43:08 pm »

This one is worth doing
5879 Blues Bassman

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Tube Amp Building - Tweaks - Repairs / Re: 5879 amp favorites?

« Last post by passaloutre on March 11, 2026, 02:42:28 pm »

Not in any way focused on this, but one idea, wondering about 5879 instead of EF86 for matchless/vox kind of thing.

I recently did an all "American tube" version of the AC15/Spitfire using an old BH Filmosound amp with 5879,12AX7,6V6,5Y3. I have some noise issues to work out in the tiny chassis, but overall it's a nice round, less-compressed tone than the "English tube" Spitfire I made prior.

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Tube Amp Building - Tweaks - Repairs / Re: Standel 25L15-Do you like it as is or would you like to change something

« Last post by sluckey on March 11, 2026, 02:23:16 pm »

HotBluePlates is the man to talk to.