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Quad 3O3  FULL COMPONENT REPLACEMENT & OUTPUT   UPGRADE

Several customers have asked if we can replace all the components in a Quad 3O3 to make it virtually new throughout

 without losing the nice warm sound.

Here it is!

WHAT WE DO:

 Option 1:

Full component replacement and new front panel

All three PCBs are stripped down to bare boards and new high performance components are fitted. The four smoothing/output caps are replaced using our PCB mounted unit. The full array of transistors included those on the heatsink are replaced with modern devices.  All resistors used are high stability 1% types. Some of the resistors used are modern fusible types, under severe fault conditions they quickly puncture if a heavy current flows.  This helps prevent burnouts and increases safety. The semiconductors used in the high voltage stages have higher breakdown voltages and increased current capability. The output transistors in particular are complimentary 150W devices compared to the original 100W types. This improves the reliability and output power handling. The voltage amplifier stage (VAS) uses a transistor with low 'early effect' to improve the inherent open loop distortion.  The output stage is modified from 'quasi complimentary' format (QC) to a 'fully complimentary' format (FC). This was not possible when the Quad 303 was launched as complimentary power devices were unavailable. This modification  helps to improve the open loop distortion and therefore the overall distortion of the 3O3, which we must add, is already pretty low e.g. 0.03% max at 700Hz.  The new distortion figure THD is typically less than  0.01% at 1kHz at 10W rms. To effect the changeover from Quasi complimentary to fully symmetrical,  two resistor positions are changed over and a track is cut and linked to a different point on each PCB. For the electronically minded, the output circuit change is available as a pdf schematic on our download tab.

THE COST:

The cost for the full component replacement and output stage modification including a new front panel (virtually a brand new amplifier), is 250.00 + return carriage. If you want new FR4 fibre glass PCBs instead of using the originals, please add 20.00.

 If you prefer to keep your original front panel then deduct 40.00.

 

Option 2:

Full component replacement with redesigned circuits for improved sonic performance: 

This is similar to the above but with a major change from the original Quad circuit. The two power output PCBs are completely removed and new 'in-house designed' high performance modern circuits are fitted. For the technical minded the circuit uses long-tail pairs, current mirrors and current sources with triple complimentary output. This reduces harmonic and intermodulation distortion to  a substantially lower level than the original Quad circuit. The warm sound still remains but with a 'veil lifted'. Note: The PCBs use conventional through hole components with individually fused HT rails.

The smoothing/output caps are replaced with our PCB mounted unit.  All resistors used are high stability 1% types. Some of the resistors are fusible types, under severe fault conditions they quickly puncture if a heavy current flows.  This helps prevent track burnouts and increases safety.

The overall sound of the new amplifier is more detailed and this is borne out by the spectrum analyser plots shown HERE

THE COST:

The cost for this major circuit modification including the new front panel, is 270.00 + return carriage.

 If you prefer to keep your original front panel then deduct 40.00.

 

 

 

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Last modified: Monday, 27. April 2015 12:57