DIY - Attenuator for Quad 405
Look McIntosh for Preamplifier
The outline of this DIY.
Creating of a passive preamplifier on the basis of the previous attenuator but with an addition of two vu-meters and a McIntosh look. This a esthetic favours the production of a silkscreen on front side with a professional side. Admire this look, it's DIY! No breath, no noise disturbs listening to the QUAD 405. Plan a neat wiring of the masses. The potentiometer is in the middle of the cabinet to avoid disturbances of the power supply.
Addition and Creating a 12 volt regulated power supply with a LM338K. This 12 volt power supply supplies all relays, backlight and vu-meter lighting and circuitry. Wiring the preamplifier with a switch to be able to select the mode with or without attenuator.
Making a loudspeaker connection between the preamplifier and the QUAD 405 power amplifier. Cable Connection and Brand cards: NEUTRIK NL4MP. This cable is necessary for the operation of the vu-meters and the delay of the loudspeakers.
Creating a 12 volt backlight as well as a timer for the speakers. (aliexpress.com)
Plug Speakon NEUTRIK Female NL-4FX
Speakon chassis socket NEUTRIK Male
Speakon plugs for professional HP connections. 4 poles.
The special ELEPHANT SPM4025 combi cable is one of the outstanding models designed specifically for the woofer and surround systems. The SPM4025 consists of a total of 4 conductors with a section of 2.5 mm. Due to its wiring mode similar to that of hi-fi drivers, the SPM4025 reproduces absolutely pure highs and faithful and dynamic bass.
Transmission of signals without losses, thanks to special constitution souls Very flexible, suitable for stage installations (PVC version only), easy to roll up Compatible with current Neutrik-Speakon connectors Easy transformation thanks to the excellent insulation and the numbering of the souls
Professional acoustic equipment/output amplifier Surround and woofer systems Fixed installations for buildings.
Creating a 12 volts regulated
power supply with a LM338K.
PCB Transformer 12 volts Gerth PT481201F.
Circuit of the attenuator for QUAD 405
Passive attenuator schematic
for QUAD 405. (click)
Timers for the speakers in 12 volts. (aliexpress.com)
Speaker break with 12 volts relay. (aliexpress.com)
VU-meters Circuit in 12 volts