Help me understand this Grayhill Rotary Switch

Help Support GroupDIY:

Ted Krotkiewski

Well-known member
Joined
Nov 4, 2018
Messages
48
Hi Friends.  :)
I am a noob, so forgive my basic question.
I am about to build the Helios Type69 channelstrip following @Ruffrecords schematic.

My question is. Why do I need this fancy Grayhill Switch with so many pins:
https://www.mouser.se/ProductDetail/Grayhill/71ADF30-01PAJS?qs=%2Fha2pyFadugEmbNBgMqNNTbUFYC4FxyauP06d7C8c82GLNetneiyZQ%3D%3D
When there is only 6 or 10 fre´q selections being used?
When looking at Ian Bell´s schematic attached, I wonder why it cannot just be a simple Rotary like This: https://www.banzaimusic.com/Rotary-Switch-1x12-Pins.html that switches between the different capacitor values?

I m trying to get my head around what all those 18 pin connections found on the Grayhill switches are for, when for example the Bass freq´s points is only 6 selections?

For example, the Rotary Switch for the mid band on my My old Raindirk Mini (Series 3) Mixer only has a cheap rotary switch with 12 selections on a single row/deck much like the attached link from Banzai music above.
The LCR design for the mid band on my Raindirk seems (To my eyes) to be off the same heritage as Helios and many other LCR designs from that day.

Anyone care to explain for a dummie like me, what the function of the Grayhill switch is compared to the simpler cheaper switch in a circuit like this?

Super thankfull for any input you might have.
My best.
//Ted
 

Attachments

  • Ian Bell´s Type69 EQ.png
    Ian Bell´s Type69 EQ.png
    244.1 KB · Views: 33

ruffrecords

Well-known member
Joined
Nov 10, 2006
Messages
13,931
Location
Norfolk - UK
For SHi and SMid you can use the cheaper 1 pole 12 way rotary switches. For the low frequency switch you do need a two pole switch (S1a and S1b). It can be a Grayhill or any other switch with the right number of ways and poles.

Grayhills were specific in the original design because they mounted directly to the PCB.

Cheers

Ian
 

Ted Krotkiewski

Well-known member
Joined
Nov 4, 2018
Messages
48
ruffrecords said:
For SHi and SMid you can use the cheaper 1 pole 12 way rotary switches. For the low frequency switch you do need a two pole switch (S1a and S1b). It can be a Grayhill or any other switch with the right number of ways and poles.

Grayhills were specific in the original design because they mounted directly to the PCB.

Cheers

Ian

Thank you for explaining this Ian.
I just realized when you wrote about S1a and S1b, that ofc, the Bass switch needs to be 2pole, since it either cuts (1st pole) or functions as a freq selector (2nd pole) Would that be a somewhat correct explanation?

Ian, I can never thank you enough for everything you are providing and sharing.
I am a big fan forever thankfull.

My best.
//Ted
 

ruffrecords

Well-known member
Joined
Nov 10, 2006
Messages
13,931
Location
Norfolk - UK
Ted Krotkiewski said:
Thank you for explaining this Ian.
I just realized when you wrote about S1a and S1b, that ofc, the Bass switch needs to be 2pole, since it either cuts (1st pole) or functions as a freq selector (2nd pole) Would that be a somewhat correct explanation?


My best.
//Ted

That is basically it. The cut and boost section in the Helios are quite different circuits so they need separate but linked switches.

Cheers

Ian
 
Top