Extended Foreplay 3 Help

[John EH]

Bear with me.  I'm shooting from the hip and have NOT cracked the manual.

I built an Extended Foreplay 3 a long time back and the Sweetest Whispers switches just went to crap.  The switches are just cheap.  I got really tired of looking at it gathering dust so I decided to order a couple DACT's but my mind was made up and I ran down to the local parts store and picked up two 100K ohm pots and soldered them in.

Well it's working but there's too much gain.  What was the value of the Sweetest Whispers and are my inbound 50K DACT's going to be okay?  Am I going to have to pad anything down.

On the upside I can leave them near hair trigger as my source is a Raspberry Pi with a HiFiMeDIY Sabre USB DAC (see the thread in Digital).  I'm running MOG and Pandora from my iPhone and control the volume remotely.  As it should be.

Anyway I don't care so much about my 100K pots but I do want to know what to do with the 50K's.

Thanks,

John

[saildoctor]

The stock sweetest whispers are 15k.  The FPIII came stock with 33k padding resistors on each input.  I've got ~300k on two of the pads on mine to get other things in the same gain ballpark as my seduction/turntable.

The alternative is to pad the input of your amp with a voltage divider - there's a white paper by Paul J in the technical topics folder: http://www.bottlehead.com/smf/index.php/topic,39.0.html

[Paul Birkeland]

You can try putting a 22K resistor across each pair (upper and lower) of outer terminals on your 100K pots to approximate a 15K control.

-PB

[John EH]

Thanks.  I had 25, 50, and 100k pots at home and in my mind I thought 100K.  I'm not changing it until the DACT's arrive.

John

[Paul Joppa]

When the DACTs arrive, you can connect them using the series resistors as used in the original FP-III - it is set up so that there can be different series resistors for each input. In the manual dated 2005, at the bottom of page 24 there is a photograph showing those resistors fairly clearly.

Keeping the 50K control stock will mean you'll want something like 100K series resistance to get back to the original default -10dB. Alternatively you can shunt each 50K with 22K or thereabout to make it approximately 15K, and retain the stock 33K resistors.

Note that the original FP-III had an unusual volume control connection, intended to make the switch less noisy when the contacts were erratic. With the 50K you'll most likely prefer to use a standard potentiometer setup, except for the series resistors.

[John EH]

When the DACTs arrive, you can connect them using the series resistors as used in the original FP-III - it is set up so that there can be different series resistors for each input. In the manual dated 2005, at the bottom of page 24 there is a photograph showing those resistors fairly clearly.

Keeping the 50K control stock will mean you'll want something like 100K series resistance to get back to the original default -10dB. Alternatively you can shunt each 50K with 22K or thereabout to make it approximately 15K, and retain the stock 33K resistors.

Note that the original FP-III had an unusual volume control connection, intended to make the switch less noisy when the contacts were erratic. With the 50K you'll most likely prefer to use a standard potentiometer setup, except for the series resistors.

Perfect. Thanks.

John