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August 11, 2020, 12:39:54 AM

Author Topic: Sweetest Whispers  (Read 2600 times)

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Offline butchbass

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Sweetest Whispers
« on: December 30, 2015, 09:02:27 AM »
I need to replace the Sweetest Whispers (SW) on my Foreplay III. I am getting a lot of static in different positions. Swiping the switches does some good but it is just a band aid. I do not see how contact cleaner would work since there are no openings in the switch body to spray it in. I am contemplating using Alps Blue Velvet pots. What value would I use? The SW are 15k which Alps does not make. Gold Points are currently too rich for my wallet because I also need to replace my selector switch. it looks like Gold Point is the best option. Any suggestions? Down the road I am looking at the Stereomour II but it is not in the cards right now. (A small price for being retired!)

Thanks
Butch
Butch Gross
Stereomour II/  Blumenstein Orcas, Dungenes/Schiit Bifrost Multibit/Amarra

Offline Paul Birkeland

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Re: Sweetest Whispers
« Reply #1 on: December 30, 2015, 09:35:20 AM »
There are many, many ways to go on this one, I'll try to outline a few easy ones.

The stock attenuator configuration has those dropping resistors that go from the selector switch out to the terminal strips close by.  These are useful to pad the incoming signal to the Foreplay preamp circuit, which allows for the 12 positions on the Sweetest Whispers controls to get you in the sweet spot.

When I have a Foreplay III come in for repair, I will generally remove both controls and all the series resistors.  I then put in a second 4P3T rotary switch and a 50K stereo log pot.  I send the output of the input selector switch to the second selector switch, where I have a series string of resistors to pad down the input (think of it as coarse attenuation).  This would be something like a 50K, 100K, and 250K resistor strung in series on the selector switch, then the output of this control goes to the 50K stereo pot.  This gives the convenience of a stereo control with the ability to pad the input so that you can use the volume pot where the channel balance is good.

Another route I have seen taken is to put a pair of 100K mono attenuators in for each 15K attenuator, wiring them as conventional volume controls.  You can probably leave the padding resistors alone in this case.  What I don't like about this is that the 100K controls have many steps, and it can be tedious to get each one set on the identical position. 

A third option is to put a 3/8" metal hole cover in one of the holes for the SW, then put a Stereo 10K log pot in place of the other control.  This would actually be very similar in terms of gain to the SW, with the lowest possible cost and least amount of work.  You could wire the control in as it is in the stock preamp (which ensures that the grid always has a path to ground), or in a more conventional manner. 

If you plan to sell the Foreplay III in order to finance the purchase of the Stereomour, keeping an eye on the resale value will be pretty important.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline butchbass

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Re: Sweetest Whispers
« Reply #2 on: December 30, 2015, 10:52:29 AM »
Paul, thanks for the quick reply and several options. I am going with the third option, ordering parts today.  I can always try the other two if it doesn't suit me.
Butch Gross
Stereomour II/  Blumenstein Orcas, Dungenes/Schiit Bifrost Multibit/Amarra

Offline syncro

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Re: Sweetest Whispers - Replacement Parts?
« Reply #3 on: March 12, 2016, 06:15:48 PM »
I have popped these apart several times to clean and apply DeOxIt to great effect.  The four prongs need prying, somewhat simultaneously, then the back half of the plastic rotary comes off.  Care at this time is required, as the bridging contact is a loose part and needs to go back or you've lost your sound.

My point of writing though is to ask, "where can I purchase a new one of these plastic rotary switches?   I'm okay with the periodic maintenance to get rid of the popping and crackling of these inexpensive parts.   Like butchbass, I am not ready to go for the goldpoints, though I like the looks of that option.
David Bogle
LinnLP12/Foobar>HagermanRipper/RotelRCD975>BottleheadFPIII>ST-70>KlipschForteII

Offline Paul Birkeland

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Re: Sweetest Whispers - Replacement Parts?
« Reply #4 on: March 13, 2016, 07:38:09 AM »
where can I purchase a new one of these plastic rotary switches?
http://www.digikey.com/product-detail/en/c-k-components/A11203RNZQ/CKN10201-ND/2043157
(I'd buy new resistors too)

-PB
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline syncro

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Re: Sweetest Whispers
« Reply #5 on: March 13, 2016, 04:01:11 PM »
Thank you, Paul!  That's a relief.   Can you also send me the details on replacing the selector switch, in kind?  Am I close with:  https://www.digikey.com/product-detail/en/c-k-components/A40315RNZQ/CKC7008-ND/181440

This is working much more quietly after I recently sprayed some DeOxIt inside.  I thought I might drill a port to make that easier in the future, but also I'd like to replace that as well and the source resistors ( see below).

Having tried to figure out from posts on this forum what specs to purchase, I thought it needed to be a shorting type rotary switch (that, if I have it right, makes before it breaks contact when switching, for us lay-electronics-persons.)  The digikey product page shows:  "Contact Timing -  Non-Shorting (BBM)"  so I suppose I had that wrong.  I see from another post of Paul Joppa (http://bottlehead.com/smf/index.php?topic=3356.msg29423#msg29423) that,  "This particular wiring sets it up so that a momentary failure of the switch contact removes the source...."  This sounds like it avoids the need for a shorting switch.

I appreciate the tip to order new resistors, and will review the original parts list and the SW instructions.  I would like to have finer low volume control, and I rarely go above 6th step.  If you can direct me toward a method to revise the volume curve I'd appreciate that greatly.  I also read from another of your posts, I think, that it may be best/easier? to increase the resistance at each input.   Will that achieve similar audible result, understandingly sacrificing the high volume settings I currently don't use.

(I was trying to configurate one from Mouser with their features configurator, and came close to this, but I always was keying in  "shorting".   Has something similar with this one:  http://www.mouser.com/ProductDetail/E-Switch/KC51A30001NLS/?qs=%2fha2pyFaduij9RhYueobLBMiVUvGkqDGb3cBebjYVfufPbi8jrysOg%3d%3d )
« Last Edit: March 13, 2016, 07:54:04 PM by syncro »
David Bogle
LinnLP12/Foobar>HagermanRipper/RotelRCD975>BottleheadFPIII>ST-70>KlipschForteII

Offline Paul Birkeland

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Re: Sweetest Whispers
« Reply #6 on: March 13, 2016, 05:46:58 PM »
The design of the Sweetest Whispers attenuator is unique in that a non-shorting switch doesn't cause the problems that you'd run into with typical attenuator designs. 

Getting more low level steps involves replacing those resistors that are installed on the selector switch. 

-PB
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Natural Sound

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Re: Sweetest Whispers
« Reply #7 on: March 14, 2016, 06:01:15 AM »
I would like to have finer low volume control, and I rarely go above 6th step.  If you can direct me toward a method to revise the volume curve I'd appreciate that greatly.  I also read from another of your posts, I think, that it may be best/easier? to increase the resistance at each input.   Will that achieve similar audible result, understandingly sacrificing the high volume settings I currently don't use.

I Think this is what you are looking for.

According to the manual 33K is the stock value to achieve an overall gain of 10dB. To pad down from the stock 10dB gain use the following guide. (See page 24 of the FPIII manual)

-6dB (80.6K ohms)
-12dB (182K ohms)
-18dB (360K ohms)

I recommend you get a few of each and experiment.

I hope this helps.