Neurochrome 686 power amplifier - GBP £2200
Collection North Notts - close to M1 J28/29 or Lincoln or mid point handover. Too big and heavy to post.
Not cheap by any means, but if you are seeking an ultra high performamce amplifier this is it. Despite its high power output this differential/balanced amplifier has incredibly low distortion figues and is totally safe. It turns on and off without a thump or buzz, just a small click as the relay clicks over.
This is, in my opinion, the ultimate Neurochrome 686 power amplifier built as the Neurochrome designer orginally intended. Unlike many builds this amplifer includes the Neurchrome PSU boards, the Neurochrome Soft Start Board and the Neurochrome Speaker Protections boards. Construction dual mono, fully balanced circuits with XLR inputs and 4mm banana speaker terminals. The rear panel also includes a 4mm earthing terminal for subwoofers. Not all Neurchrome 686 builds are the same. It is important to check what is and what is not included and where non Neurochrome parts are fitted that compromises have not been made.
Power
Output Power 240 W 8 Ω, < 0.01 % THD+N
Output Power 360 W 4 Ω, < 0.1 % THD+N
Case Dimensions in mm (approx)
450 wide v 410 deep x 190 high
(Note: the sockets and switch add depth so allowing for cables etc front to rear depth in use is about 490mm The amp fits on my Target rack)
In addition to the two Neurochrome modulus 668 amplifier boards this buildh as the following fitted.
2 x Neurochrome Power 686 power supply boards – one for each channel
2 x 400 watts windings @ 25v ac. One winding for each channel
The transformer feeds the Neurochrome 686 power supply boards which have 88,000 uf of reservoir capacity for each channel.
1 x Neurochrome Intelligent Soft Start
When a power amplifier is first turned on, the mains transformer will draw significant current for the first few mains cycles as the magnetic field builds within the transformer core. The inrush current can reach several hundred ampere, which severely stresses the transformer. Furthermore, to accommodate the high inrush current, the mains fuse used to protect the transformer and connected circuitry must be grossly oversized, which limits the effectiveness of the fuse in the event of a catastrophic fault in the circuit. The Intelligent Soft Start (ISS) solves this issue by limiting the inrush current to a safe value using a NTC resistor. Once the magnetic field has been allowed to build within the transformer, the soft start circuit shorts out the NTC resistor with a relay.
2 x Neurochrome Guardian speaker protection boards – one for each channel
The Guardian-86 is a high-end protection circuit designed to protect speakers against two common ways that power amplifiers can misbehave:
Note: the above rear panel, is an older image, the screws are no longer loose and the hole above the right speaker terminals has a semi flush green 4mm banana
socket fitted - which is wired to ground/earth.
Collection North Notts - close to M1 J28/29 or Lincoln or mid point handover. Too big and heavy to post.
Not cheap by any means, but if you are seeking an ultra high performamce amplifier this is it. Despite its high power output this differential/balanced amplifier has incredibly low distortion figues and is totally safe. It turns on and off without a thump or buzz, just a small click as the relay clicks over.
This is, in my opinion, the ultimate Neurochrome 686 power amplifier built as the Neurochrome designer orginally intended. Unlike many builds this amplifer includes the Neurchrome PSU boards, the Neurochrome Soft Start Board and the Neurochrome Speaker Protections boards. Construction dual mono, fully balanced circuits with XLR inputs and 4mm banana speaker terminals. The rear panel also includes a 4mm earthing terminal for subwoofers. Not all Neurchrome 686 builds are the same. It is important to check what is and what is not included and where non Neurochrome parts are fitted that compromises have not been made.
Power
Output Power 240 W 8 Ω, < 0.01 % THD+N
Output Power 360 W 4 Ω, < 0.1 % THD+N
Case Dimensions in mm (approx)
450 wide v 410 deep x 190 high
(Note: the sockets and switch add depth so allowing for cables etc front to rear depth in use is about 490mm The amp fits on my Target rack)
In addition to the two Neurochrome modulus 668 amplifier boards this buildh as the following fitted.
2 x Neurochrome Power 686 power supply boards – one for each channel
- Optimized PCB layout featuring the elaborate use of copper planes and pours to minimize parasitics.
- Simple capacitor snubber to minimize diode switching noise. Option for CRC snubber for advanced builders.
- Four discrete diodes with individual heat sinks.
- Four x 22,000 µF, 50 V reservoir capacitors. Snap-in capacitors up to 40 mm in specified diameter supported.
2 x 400 watts windings @ 25v ac. One winding for each channel
The transformer feeds the Neurochrome 686 power supply boards which have 88,000 uf of reservoir capacity for each channel.
1 x Neurochrome Intelligent Soft Start
When a power amplifier is first turned on, the mains transformer will draw significant current for the first few mains cycles as the magnetic field builds within the transformer core. The inrush current can reach several hundred ampere, which severely stresses the transformer. Furthermore, to accommodate the high inrush current, the mains fuse used to protect the transformer and connected circuitry must be grossly oversized, which limits the effectiveness of the fuse in the event of a catastrophic fault in the circuit. The Intelligent Soft Start (ISS) solves this issue by limiting the inrush current to a safe value using a NTC resistor. Once the magnetic field has been allowed to build within the transformer, the soft start circuit shorts out the NTC resistor with a relay.
2 x Neurochrome Guardian speaker protection boards – one for each channel
The Guardian-86 is a high-end protection circuit designed to protect speakers against two common ways that power amplifiers can misbehave:
- Sharp voltage transients on power-up and power-down, resulting in annoying clicks and pops in the speakers.
- Excessive DC voltage on the output of the amplifier, for example resulting from amplifier failure or from unruly signal sources.
Note: the above rear panel, is an older image, the screws are no longer loose and the hole above the right speaker terminals has a semi flush green 4mm banana
