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12AX7 12AU7 Tube Preamplifier HiFi Pre-Amp Shigeru Wada Japan Circuit need help
12AX7 12AU7 Tube Preamplifier HiFi Pre-Amp Shigeru Wada Japan Circuit need help
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Old 27th December 2018, 04:40 PM   #1
pghunt is offline pghunt
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Join Date: Dec 2018
Default 12AX7 12AU7 Tube Preamplifier HiFi Pre-Amp Shigeru Wada Japan Circuit need help

Hi
I've purchased a 12AX7 12AU7 Tube Preamplifier HiFi Pre-Amp Shigeru Wada Japan Circuit kit from eBay Douk Audio 12AX7 12AU7 Tube Preamplifier HiFi Preamp Shigeru Wada Japan Circuit 8112417629285 | eBay

Has anyone else built this kit. I'm new at building amps and I've been slowly going through the circuit diagram. However I was wondering if anyone has some pictures of the inside of amp, showing the wiring and connections, which I can use as a guide with the circuit diagram I have.

Thanks in advance for your help

Phill
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File Type: jpeg amp diagram.jpeg (107.6 KB, 197 views)
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Old 27th December 2018, 06:29 PM   #2
Alllensoncanon is offline Alllensoncanon  United States
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Location: NorCal, East Bay
12AX7 12AU7 Tube Preamplifier HiFi Pre-Amp Shigeru Wada Japan Circuit need help
They have a picture in your link.
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File Type: jpg preamp.jpg (295.8 KB, 190 views)
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Old 28th December 2018, 05:36 PM   #3
DF96 is offline DF96  England
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Join Date: May 2007
The picture shows how not to wire a heater, for one of them. The valve at top centre has the heater wires encircling the valveholder, to get to pins 5 and 9?. All the books say this is the wrong way to do it as it maximise magnetic hum field at the valve.

Of course, it may use DC heaters, but then why bother to twist at all?
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Old 2nd January 2019, 03:59 PM   #4
pghunt is offline pghunt
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Thanks for the info everyone. I've been using google translate to translate the chinese on the circuit diagram.

I'll definitely won't follow the pic in too greater detail, as agree I want to minimise hum as much as possible
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Old 7th January 2019, 04:45 PM   #5
pghunt is offline pghunt
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Join Date: Dec 2018
Default How to manage the ground bus

Hi all,

Thanks for your help. Looking at the images of the circuit diagram and also the physical image of the circuit. It looks like it's using the chassis as the ground bus. However I can't see how that connects to the neutral. Also it looks like from the photo, they haven't earthed the chassis. Any thoughts?

cheers

Phill
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