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91

Tube Amp Building - Tweaks - Repairs / Re: Favorite 6AQ5 SE and PP power sections?

« Last post by TIMBO on January 20, 2026, 02:23:36 am »

They worked very well in this amp
THE HOWLER

92

Tube Amp Building - Tweaks - Repairs / Re: Champ-ish "pocket"-amp

« Last post by Banjan73 on January 20, 2026, 02:21:55 am »

No, I didn't build the cabinet - that's what it came in. Pretty cool looking tiny thing.

Very cool! Such a nice amp!

I did one like that a while back - a vibrochamp circuit mounted on my own custom Ally folded sheetmetal plate squeezed in an old Behringer Thunderbird box. Stancor A-8092 SE OT, PT out of an old Jap signal jennie and a Mojo Choke. Makes any geetar sound awesome with a Celestion 15W 8" speaker (also has plug for external speaker cab)

Guess I am not the only one here thinking about making such an amp, hehe. This thing also looks awesome! We should come together and have a tiny-amp.jam session, hehe :-)

Great projects!


Tubeswell, I'm curious about the Electrical Safety sticker on the back panel.  Did you have it independently evaluate?

Yep - here we we are, if you want to use any electrical appliance in a performance situation in someone else's venue, there's a legal requirement to have it tag-tested for the integrity of the safety ground and the adequacy of insulation between the AC power supply source and the mains earth. There are independent contractors who have the calibrated equipment who'll do that for $20 and print out the certification label. (The tag is normally supposed to go on the power cord but this has a jug cord, so I slapped it on the back of the chassis, and nobody has complained yet LoL).

I used to work at Nemko in Norway. So I know alot about these tests.

93

Tube Amp Building - Tweaks - Repairs / Re: Where to ground the first filter cap?

« Last post by Willabe on January 20, 2026, 12:51:32 am »

So I wanted to know if it would be better for me in an effort to reduce hum, to keep those ground wires as short as possible and just ground them directly to the buss near the component, rather than running them back to that star ground where there might be, in some instances, 4-5 wires coming into the star.

Your wording is throwing me off. But if I'm understanding this right;

What does it show/say in Merlin's grounding page? Look at the drawings.

Fig. 14:14 a and 14:14b answers your question.

14:14b shows the improved ground star/ground buss wiring. That's how you want to wire it up. Including with the filter cap right there at the circuit it feeds. Not back on the far end of the chassis by the PT like Fender did.

If you ground a component as soon as you can to the buss instead of running a wire from the component over to the buss. Then even though you shortened the ground wire from the component, now the buss wire is doing the same as the wire. So it's still just as long as it was.

I'd rather get the component grounds gathered together closely at 1 point and have the filter cap that feeds it right there at that ground star. So all those component ground leads and the filter cap ground lead come together at 1 point on the ground buss.

And the way the 1st filter cap ground lead is wired up is the most important ground to get right.

... but because the components for some of the nodes are at the Input Jack end of the chassis, it results in several long wires, maybe 5" or a little less in length, being run to get to that Node's star grounding point on the buss.

Because their long, you have to watch out for what other wires are they running close too or along side of?

All ways better to keep wires short if possible so there's no cross talk/interference with other wires. So short ground loops are best practice when possible.

It's part of doing your layout.

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Tube Amp Building - Tweaks - Repairs / Re: Favorite 6AQ5 SE and PP power sections?

« Last post by mountainhick on January 19, 2026, 06:34:37 pm »

Here are two. Just posted the first in the other thread, but this seems a good place to collect them.

1 - MIJ single ended amp with single diode rectifier, 12AX7, and 6AQ5
2 - A Champ-type amp schematic by Adam Alpern that I found elsewhere, with diode rectifier, 12AX7, and 6AQ5. I built an amp very similar to this but haven't done a complete schematic yet - I used a toroidal transformer, added a switchable tone control, switchable V1a bypass cathode, and a pot for variable NFB. This one sounds particularly good with a strat.

That Micro Champ is just about spot on what I've been thinking for a happy SE 6AQ5

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Tube Amp Building - Tweaks - Repairs / Re: Favorite 6AQ5 SE and PP power sections?

« Last post by dogburn on January 19, 2026, 06:22:07 pm »

Here are two. Just posted the first in the other thread, but this seems a good place to collect them.

1 - MIJ single ended amp with single diode rectifier, 12AX7, and 6AQ5
2 - A Champ-type amp schematic by Adam Alpern that I found elsewhere, with diode rectifier, 12AX7, and 6AQ5. I built an amp very similar to this but haven't done a complete schematic yet - I used a toroidal transformer, added a switchable tone control, switchable V1a bypass cathode, and a pot for variable NFB. This one sounds particularly good with a strat.

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Tube Amp Building - Tweaks - Repairs / Re: Champ-ish "pocket"-amp

« Last post by dogburn on January 19, 2026, 06:13:14 pm »

Niice!
Yes, it looks as somewhat the same type of amp.
Did you build the "box" (dont remember the english word right now) yourself?

No, I didn't build the cabinet - that's what it came in. Pretty cool looking tiny thing.

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Tube Amp Building - Tweaks - Repairs / Re: Champ-ish "pocket"-amp

« Last post by dogburn on January 19, 2026, 06:11:54 pm »

Do you have a schematic for the Single Ended 6AQ5? Thanks
[/quote]

Yes, I've got the schematic that was inside the amp, and I added the values to the best of my ability - it was not easy to see all the caps and resistors because of the way it was made. I've attached that here.

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Tube Amp Building - Tweaks - Repairs / Re: Favorite 6AQ5 SE and PP power sections?

« Last post by astronomicum on January 19, 2026, 05:49:28 pm »

looking for info for just SE and PP

Univox made 3 PPs: the U-72/U-75, U-102, and the U-155R

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Tube Amp Building - Tweaks - Repairs / Re: Favorite 6AQ5 SE and PP power sections?

« Last post by mountainhick on January 19, 2026, 05:37:21 pm »

 I have yet to find a guitar amp SE schematic.

Univox U-41/U-42/U-45

That one is more on target in terms of my experience running 6AQ5.

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Tube Amp Building - Tweaks - Repairs / Re: Favorite 6AQ5 SE and PP power sections?

« Last post by astronomicum on January 19, 2026, 05:28:55 pm »

 I have yet to find a guitar amp SE schematic.

Univox U-41/U-42/U-45