• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

help with turning a schematic to point to point or tag strip


2012-07-16 8:56 pm
Hi I have all the parts to make a philips ag9016 but struggle to turn the schematic into a layout like the one in pic. The blanked area on schematic the tone as I want to build it without.
Can anyone please help me thanks.


  • AG9016_tone_blank.jpg
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  • 5F1_Layout.png
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2011-04-29 8:37 pm
You don't really need a tag board, just three terminals/channel, plus ground returns.
Mostly wire it point to point, using the leads of parts instead of wires where possible.
Keep the input tube/wiring away from the output tube/wiring. Do you want two channels?
Set the parts around the tube sockets and adjust their positions for the simplest routing.
Don't like that short circuit switch across the secondary though, WTF is that about?
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Paid Member
2003-06-12 7:04 pm
Maine USA
....Don't like that short circuit switch across the secondary though, WTF is that about?

It is perfectly safe to short the output of a self-biased SE tube amp. How is it going to hurt?

It is NOT safe to leave the output open and hit the amp with large signals. Flyback will puncture the OT insulation.

If you look close at 5F1, its speaker jack shorts when speaker plug is removed.
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2016-06-07 6:50 am
Possible Scenario:

Self Biased SE amp, with a 3K primary OPT.
Short the secondary output common and 8 Ohm Tap.
Now the primary impedance = ~ DCR of the primary.
The output tube is only 1 DCR away from B+

Now, suppose you do not remember that the speaker is not connected, and you do not hear anything, so you turn the volume control up, but not enough to draw grid current. Or you turn it up even more, draw grid current, possibly blow up the cathode bypass cap and bias resistor.
The poor output tube is drawing more plate current than it was ever designed for (for roughly half of the time).
. . . No, I will not try that trick to see if anything gives.