Bottlehead Forum

Bottlehead Kits => Legacy Kit Products => Foreplay III => Topic started by: syncro on July 23, 2016, 11:20:53 AM

Title: Foreplay III - popping on power-down
Post by: syncro on July 23, 2016, 11:20:53 AM

Once I replaced the coupling caps with the big black Obligattos, the power-down pop mellowed as compared to how it sounded with the stock parts.  It has been consistent for several years.  Recently, the "pop" became profoundly and disturbingly louder and sharper.

What creates this sound from the FPIII?

Why would it have changed?  (I have an unscientific theory that it may have to do with the fact that the pre-amp has been operated by others in the house recently, more so than in the past.  Powering off, then on again after a few seconds has been part of the operational activity.)

How can I minimize it?

Thanks in advance!

Title: Re: Foreplay III - popping on power-down
Post by: Doc B. on July 23, 2016, 03:15:56 PM

Preamp on first, then amp on. Amp off first, then preamp off.

Title: Re: Foreplay III - popping on power-down
Post by: syncro on July 23, 2016, 06:39:44 PM

 8)  Simple is good.  Thanks, Doc!

So, solution to the issue at hand (build the S.E.X kit, or add a power switch to my ST-70), but I still wonder about where the puff of electrons comes from.

Title: Re: Foreplay III - popping on power-down
Post by: Paul Joppa on July 24, 2016, 05:42:53 PM

1) Normally, the pop is from the output capacitor charging (turn-on) or discharging (turn-off).

2) This gives no clue about why it might change. The likliest things that come to mind is a possible change in downstream components, e.g. an amplifier with greater gain than before, or a more sensitive speaker?