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Svar på spørsmålet fra eraudio som resturerer og leverer deler til Quad:
Hi Atle,
The Quad 63 operates with around 1kv to 8kv (maximum permitted but rarely used) peak to peak voltage across the stators.
A typical operating voltage expressed across the stators for normal listening levels would be 2 to 3 kv. This will be difficult to reach with direct drive unless very high voltage tubes are used.
An alternative which may give a sonic improvement is to have the output transformers of the tube amp wound to have a turns ratio of say 1:6 or perhaps 1:8. This will allow the tubes to see the correct impedance and would deliver sufficient voltage to the speaker for satisfying SPL. This type of transformer would be simpler to build than a traditional output transformer while maintaining good frequency response as the turns ratio is considerably lower.
In theory eliminating the 2 input transformers from the speakers should improve the sound, however there may not be sufficient improvement to justify the cost.
It may be better to simply replace the 220uf electrolytic input capacitor for a decent polypropylene type. This will improve the sound quality. Mundorf make a 220uf 250 volt rated polypropylene cap that are quite large but will fit inside the base of the speaker. These are not too expensive and will give a good improvement.
Best regards from hot and sunny Oz
Rob
