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Quad 909 upgrade/mod list

For the input coupling cap, the original value of C2 is 330nF.

I read somewhere "You can use 470nF for a - 3dB point of 5 Hz if that value is more easy to find”.

Does increasing the value mean some high frequency information is lost?
 
Thankyou Julf, by raising the value does this mean we gain slightly more low frequency information?
 
Can increasing the capacitance of the small electrolytics C7, C9, C11 also increase bass response, or is this does this phenomenon only apply to the C2 coupling cap?
 
Can anyone advise me if its worth adding de-coupling caps (100nF MKT) for any of the Zener diodes in the 909?

Which Zeners (if any) could benefit from de-coupling?
 
I have just read through this thread ( very tedious in places ) and really wonder what drives Chris88.
He's obviously deeply unhappy with his Quad amplifiers. Like many on the Internet he is searching for some sort of 'Audio Perfection', which he'll never find.
There's a breed of audio enthusiasts that will never be satisfied whatever changes they make...
 
if you unhappy with the 909 then find something else , the original is a stable amp. and a very good one too. this circuit as been going since around 81 , the 405/1 had limited drive .that was corrected soon after..my advice do not change /add any component unless it has failured or looks in distress. If you speak to rob at quad, the number of modified units keeps their service guys/gals busy
 
If you’re unhappy with the 909 then find something else , the original is a stable amp. And a very good one too. This circuit as been going since around 81 , the 405/1 had limited drive . That was corrected soon after..my advice do not change /add any component unless it has failured or looks in distress. If you speak to Rob at quad, the number of modified units keeps their service guys/gals busy

I think your last line, about speaking with Quad, says it all...
 
If i use 100V on the boards for C7, C9, C11 (instead of stock 63V), is there any disadvantage to using 100V? Obviously there is the size, but can using a higher voltage here lessen the life of the caps or cause the capacitance to lower more quickly over time? Cheers gents
 


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