Bottlehead Forum

General Category => General Discussion => Topic started by: Larpy on January 07, 2021, 08:05:09 AM

Title: Caps and turn-on "thump"
Post by: Larpy on January 07, 2021, 08:05:09 AM

I've been rolling output caps in my Extended Foreplay III (which feeds a Kaiju) and I confess I fell under the sway of what Doc B calls "cap of the month" syndrome.  A question has emerged.  I have a preamp out signal from the FPIII that goes to subwoofer amps that are set to turn on when there's a signal present.  I've noticed that some highly regarded boutique caps produce a distractingly loud turn-on thump (which I hear through the subs) when I turn on the FPIII.  Other caps are silent when I turn on the FPIII.

Since the only difference involved is the brand of 2.2uF output caps, does the presence of a turn-on thump suggest that those caps are passing DC?  Are they flawed (or defective) caps?  Or is a turn-on thump not necessarily a reflection of rogue DC from a bad cap?  (It might be worth adding that the caps that thump don't sound very good.)

Title: Re: Caps and turn-on "thump"
Post by: Neuronal on January 07, 2021, 08:30:42 AM

I have a similar setup to yours (EFP3 ->paramounts with a powered sub directly connected to the EFP3) and with the auricaps provided with the extended kit I also get the thump.