Fidele Audio
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Fidele Audio
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Quad 34 ST Upgrade - Full Details. All operational amplifiers are replaced with Burr Brown OPA227 or OPA2227 (Dual Amps). These are far superior to the original Op Amps giving a much more neutral sound and far lower distortion. De-coupling capacitors are added at each op amp location for maximum stability. All bilateral switch ICs are replaced. These are electronic switches used to transfer the selected input signal to the main pre-amplifier circuits and also to select filter levels. The originals are cheap ICs with a very high distortion rate. The replacements are the best I can find and have a very low 'On' resistance and a distortion rating of 0.008%. (Some of the cheap modern ones have a distortion rating of 0.1%.) All signal path electrolytic capacitors are replaced with polyester film capacitors or wire links! The various stages of the Quad 34 are usually linked with large electrolytic capacitors to block any DC offset from one stage to the next. By using very low offset Op Amps we can eliminate the need for these coupling capacitors. The only exception being the tape output where we use a non-polarised electrolytic capacitor. The phono input module signal path capacitors are replaced with Nichicon Muse ES non polarised capacitors and all resistors are replaced with very low noise types. The input load capacitors are replaced with polystyrene capacitors at a value of your choice to match your cartridge. Please consult you cartridge instructions and specify an input load capacitor of 220pF, 560pF or 22nF as required. The transistors are replaced with low noise audio transistors. The motherboard input module power supply capacitors are replaced with ELNA Cerafine capacitors. All power supply electrolytic capacitors are replaced with ELNA Cerafine except that a Rubycon ZLH capacitor is used for the main capacitor. The bridge rectifier is replaced with fast Schottky diodes. Also further RF de-coupling is added to all power supply lines. |
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