Black and White Version of Turret@AmpGarage's JMI/VOX AC15 Schematic (OA-031 Circuit)

[MarkusBass]

Close to V1 I was checking how the twisted wires are drawn. And I forgot to remove the results of the experiment. Please remove it.

Mark

[dchang0]

Done! Left it at v2.0 at the link above.

[dchang0]

Sorry to necro-post. I just noticed that the Turretboard AC15 schematic and layout appear to differ from the original OA-031 schematic in the wiring of the input jacks.

First of all, TurretBoard's layout and schematic don't even match each other. On the layout, the 1M resistor R7 doesn't connect to either 68k R6 or 68k R5 at all. But on the TurretBoard schematic, it does.

On the JMI OA-031 schematic, the 1M resistor R7 connects to R6 and the tip of jack J2 but then to the tip-closed-leg of jack J1.

Which is correct? I'm guessing the OA-031 schem is correct and it matches the 1994 AC30 Top Boost Reissue schem, but TurretBoard did say his drawings were taken from a real, live JMI AC15...

What happened in TurretBoard's schem and layout? Is this a typical user-mod? Does it sound better?

From left to right: 1) TurretBoard's AC15 layout for both channels' input jacks, 2) TurretBoard's AC15 schematic for Normal Channel (Ch 2), 3) JMI OA-031 AC15 schematic for Normal Channel (Ch 2), 4) VOX AC30 Top Boost 1994 Reissue Normal Channel schematic



EDIT: I found this thread on the same issue: http://vintageamps.com/plexiboard/vi...p?f=2&t=108211

Seems to answer the question of "does it sound better," as in there is lower noise. TurretBoard's layout and schem are both wrong--the correct wiring is the JMI AC15 and AC30 schem as shown.

[dchang0]

Also, note that in both Turret's schematic and layout, C11 is supposed to be wired to C9, not C7, but this will require that the Cut pot be rewired relative to C11 (and will probably reverse the direction of the pot from clockwise to counter-clockwise or vice-versa).

Turret was probably not wrong; he probably copied the JMI Vox AC15 he had perfectly. The wiring should not make a difference in the outcome (the way the Cut pot works). I am merely noting this error so that people following the original JMI Vox OA-031 schematic (as opposed to Turret's schematic) like I am are not confused.