Well I built a Valvecaster running on 12 v with a 12AU7.  Did I enjoy building it? Yes. Do I like how it looks and sounds? Yes. Did I make the tube  unnecessarily visible to look cool? Yes. Was it worth the trouble? Yes for me. Will I build more? Probably

12au7 starved plate guitar preamp clip 1 https://imgur.com/gallery/dV5ogqh

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BTW the volume pot is 1M ohm which is not ideal as its 'off' from 1 to 9 and everything happens from 9.1 to 10. Can I improve that by adding resistors in parallel?

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The caps were not charged in at least 3 years so I should be OK. I've used the Kemo amps a lot and I like them. They need good shielding and grounding for noise. I also have the 40w version and you can hammer it with fx pedals without the amp distorting. This 12w one will distort a bit more with a guitar. They are durable though, compared to some cheaper PCB modules which dissolve once a soldering iron is introduced.

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It's been a while but this is going to be a powered speaker and maybe guitar amp. It has some of the lovely old radio sound due to the speaker and the enclosure even if theres no valves in the signal path. On the right is a whopper of a volume/tone/power switch. Pot seems noisy but I will definitely use the on/off element. The front panel lights up with good old fashioned incandescent bulbs. I plan to leave the chassis intact and in situ.  Should I discharge the old capacitors for safety?

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Quote from: joecool85 on July 11, 2020, 05:45:47 AM

Quote from: flester on July 08, 2020, 06:15:06 AM
BTW I reversed the polarity on the GDI21 and I got smoke but it still works. The only effect is that the LED now stays on whereas it should only be on when an input is plugged in.

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Not sure I would trust using it revered polarity for any length of time.  Honestly I'm surprised it still works!

Yes I know. That pedal was so cheap I don't mind if it goes. Might put reverse protection on the whole rig though. The pedal PS and all the pedals are centre egative and the amp is centre positive so theres a lot of opportunities to mess it up.

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Power amp is just a Kemo m034n module with in/out Jack's and volume pot. The module is supposed to give 40w into 4 ohms and 16V supply. I am using 12v laptop supply or car battery and its plenty..

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BTW I reversed the polarity on the GDI21 and I got smoke but it still works. The only effect is that the LED now stays on whereas it should only be on when an input is plugged in.

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Just finishing my pedalboard/ box which includes a power amp plus all my pedals. 2 switchable inputs, 12v power via dc jack, and one output jack to cab. Signal path is
Mooer ABY pedal
Boss DS-1, Danelectro Fab overdrive, Behringer Tremolo, Behringer Delay, Mooer Shimverb, Behringer GDI2, Power Amp. Yes, I am a fan of cheap pedals.
Needs a bit of cable management maybe. Not shown is the lift-off lid to be attached with case clips. Demo to follow.

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Probably expensive but should get cheaper over time

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I have not yet tried to make PCBs but this looks interesting

https://www.hackster.io/news/print-instant-circuits-from-an-inkjet-with-silver-tape-743962a056ef

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** Removed duplicate posts and fixed link in original post **

Thanks for the tip. I now have some lead solder and it is indeed easier to use.

I decided to use wire links instead of repairing the broken traces and have good connections now. I am left with 2 issues, which I can live with but would be nice to fix if possible. One is that there's still quite a lot of hiss.  Also the overdrive still goes crazy from about half way up, after which I get a very loud low frequency buzz.  While half way is more than enough overdrive for me most of the time,  theres obviously still something wrong.
The pot is new, works smoothly as measures correctly (250K linear). All pots have been cleaned with contact cleaner. Could this point to the opamp or the clipping diodes?

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You're right about cleaning up my soldering. Yes, its lead-free solder. And I will continue checking the ground connections.

No crackles when I wiggle any of the pots or jacks.
Joe, your mention of ground connections focused me. I think I soldered the overdrive pot, middle leg incorrectly to ground. See before and after photos below. What do you think?


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Thanks. I will try those checks.

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Correction:.
1.At low levels, with overdrive at zero, a. Pretty good clean signal with a lot of hiss via internal speaker.
b. Signal disconnects intermittently when using headphones

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