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| NET Audio Full Products Sonance DAC NA200 Power Amplifier Window Passive Preamp CD Player Upgrades
CD Player Clock Upgrades Quad 33 Upgrades Quad 303 Upgrades Accessories
Reviews Postage Options Downloads |
The classic QUAD 33 although very good for its vintage is now
behind the times as far as sound quality and technology are concerned.
The sound quality of the 33 can now be brought up to very high
performance levels with new plug in circuit boards (PCBs) which have been
specifically designed to fit inside the chassis just as the originals
did, but with much improved performance.
These PCBs are a direct plug and replace boards for the current items found in a Quad 33 Pre-Amp and have been designed for ultimate transparency. They buffer the volume control before the signal is fed to the tone control circuitry and second amp. This second amplifier is the output buffer and tone control amplifier. Feature of the circuit are:-
The treble is smoother and more incisive. Bass is better formed and easier to follow. Sound staging is bigger and wider with improved separation between individual instruments and voices with less smearing. Overall the sound quality is vastly improved over the original Quad Boards with it being more "out of the speakers" and realistic. The Pre-Amp with the modified PCBs has been driven from a DAC with a digital volume control so that it can be compared with the DAC feeding the power amp directly. With the Pre-Amp in circuit with high quality cables the new PCBs are virtually totally transparent compared to the DAC feeding the Power Amp directly with no Pre-Amp in the signal chain. For the PCBs to function correctly a small modification has to be made to the Quad 33 PSU PCB (Please see photo). The original 120 Ohm resistors need replacing by 68 Ohm resistors. These are also supplied preformed and ready to fit and could probably be done for a small price by your local TV repair shop. For vinyl enthusiasts there is a Disc Input Amplifier Board available. With the mod to the PSU as listed above only the Disc Input Amplifier PCB or Output PCBs can be fitted but not together as the internal power supply cannot power up both upgrade PCBs. To resolve this problem a tape input card will be available shortly which has been extended in length to accommodate a DC power socket. This enables an external 15-18V power supply to be plugged in and power up all available cards. Removing the mains from inside the pre-amp has additional benefits on the sound quality. Any upgrade which includes the tape adapter PCB will not require any internal modifications to be made and are just plug in upgrades. All signals from either the disc input (configured for either disc or CD), radio 1 and radio 2 passes through the buffer on the tape adapter PCB and then through the two output PCBs and then on to the output connector. A 33 with the full upgrade kit will surely be a vinyl enthusiast's dream. Please Note:- With the new resistors fitted to the original Quad Power Supply only one Disc Amplifier or two Output Amplifier boards can be fitted as the original PSU cannot supply enough current for both. For more info on upgrading without any internal modifications being required please see the Full Upgrade Page.
Output Amplifier Boards
If you require both the radio inputs to have the same sonic quality as the tape replay input then a tape link board is available. This is used to replace the original tape adapter board (shown above) and links the two radio inputs to the volume control, bypassing the original circuitry and therefore maintaining maximum sonic quality on all 3 inputs so that the full benefits of the Minimalist Buffer Board can be realised.
Preformed Resistors
Resistors Fitted to Quad Power Supply
Output Boards Fitted inside a Quad 33
Quad 33 Output Amplifier UpgradeOutput Amplifier upgrade includes:-
OPA627 opamps can be fitted to produce the best performance. These opamps are generally known to be of the ultimate sonic quality but are expensive compared to other audio grade devises. Total Price of OPA627 Option = £56
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