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    Effects of a Higher Capacitance Quad Cap

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    hansfob

    Posts : 18
    Join date : 2010-10-24
    Age : 52
    Location : Rickmansworth, England

    Effects of a Higher Capacitance Quad Cap

    Post by hansfob on Thu Sep 27, 2012 6:10 am

    Hi,

    I have two Mk3s with the VTA driver board and both work very well without any problem. They both have the original quad caps as far as I can make out. As they are getting on a bit in years. I am looking to mod the amps to make them more rugged such as the diode mod to support the tube rectifier and new quad caps with a bit of surge overhead for robustness.

    I just want to ask the forum if there are advantages to replacing the quad caps with ones of higher capacitance such as 80/40/30/20 uF or 40/40/20/20 uF. Does higher capacitance adversly affect the VTA driver or power transformers? Is there likely to be a noticable change in the sound of the amps? I am looking at the Authenticaps sold out of Germany only because I live in the UK and they seem to be an economical choice.

    Any comment or advice greatly appriciated.

    Best regards to all

    Brian

    Bob Latino
    Admin

    Posts : 2411
    Join date : 2008-11-26
    Location : Massachusetts

    Re: Effects of a Higher Capacitance Quad Cap

    Post by Bob Latino on Thu Sep 27, 2012 7:14 am

    Hi Brian,

    The Authenticaps out of Germany are very high quality quad caps. I routinely use the 80, 40, 30, 20 uF Authenticap in both the VTA ST-120 and the VTA M-125's. In a Mark III the orientation of this cap should be slightly different than in an ST-70. In a Mark III just orient the 80 section to face the rectifier tube. You want the RED output transformer wire connected directly to the 80 section. The cap is a low ESR (Equivalent Series Resistance) cap with very quick recharge rates.

    IMHO there is an advantage to using this cap ... It has a higher voltage rating (550 VDC versus 525 VDC on the stock cap) than the stock cap AND has more capacitance which the amp CAN use. Replacing the stock quad cap on and ST-70 or Mark III with one of these will usually give the amp a little more bass response especially at higher volume levels.

    Bob

    hansfob

    Posts : 18
    Join date : 2010-10-24
    Age : 52
    Location : Rickmansworth, England

    Re: Effects of a Higher Capacitance Quad Cap

    Post by hansfob on Thu Sep 27, 2012 12:13 pm

    Many thanks for the info Bob. You expertly anticipated and answered my next question "how to orientate the cap.........." without me even having to ask it.

    Regards
    Brian

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