Shorting or nonshorting switch, that is the question.

I made what I thought was a great e*** score. A whole bunch of 2 pole 12 position Grayhill switches. The seller said they were shorting. I tried one in an EQ I'm building and I'm getting clicks. I don't see a part number on the switches or on the plastic packaging.

How do I test a switch to see if it's shorting or non shorting?

set your multimeter to "diode test", connect to positions 1 and 2 and see if it bleeps when you move the pole.

Hi Paul,

I scored a bunch of 1x12s in a similar way. I tested mine by setting the switch to position 1 and connecting one of my multimeter probes to the centre pin. Then I moved the switch and until it was halfway between position 1 and position 2 (mine sat in this position, yours may not). I touched my other probe of pin 1 and 2. In my case I had continuity in both meaning my switches were shorting. A non shorting switch would give continuity in neither or just one.

Are you at liberty to say what the eq design was? I'm thinking of the Forssell swinging output plan where he mentioned using a 1 meg resistor to ground to avoid clicks if you were switching capacitors (from memory so could be dodgy).

Cheers,
Ruairi

Hejsan beat me to it with a much better suggestion

best of luck
Ruairi

[quote author="ruairioflaherty"]Are you at liberty to say what the eq design was? [/quote]

Thanks, guys. It's the Barry Porter Net EQ. I finally got the first channel working today. Most of the time of course was spent sourcing parts and going very slow to avoid mistakes. When I powered it up two out of four sections worked. I put the wrong value capacitors in the hi mid tuning section so that was an easy fix. The Hi section was a little tougher but turned out to be an oscillating op amp.

Now I have to stuff another channel and put them in a box. I have the frequency select on pots. I'll play around with it for a while and pick 12 frequencies per band. Then I'll make the switches.

Cool! Did you build it on vero or make a pcb? What opamps did you go for?

People whose opinion I trust like Dave Collins have said that it's very nice design.

Would love to see pics when you're done.

Cheers,
Ruairi

I bought the PCB's from a tech who did the layout. There is the option for using DOA's or IC's. There are 22 opamps per channel so using DOA's would be a little pricey consdering I'm building eight channels. I'm using the LME49710 to start. I have a few types of DOA's that I'll try in the In/Out and summing positions. Hopefully I'll like the IC's so I can save myself some cash. I haven't got to the critical listening stage yet. I couldn't even listen to anything at the bench until this week when I got a little fostex monitor. The only thing I've now listened to is a sine wave. It was a beautiful sounding sine wave.

I bought the PCB's from a tech who did the layout

Click to expand...

Would you share the source? It´s a very nice project!

[quote author="Gold"]I bought the PCB's from a tech who did the layout. [/quote]

I've got Gerbers for that project that I downloaded from the original page (can't remember where). Is there a reason you went with a new layout?

There are 22 opamps per channel so using DOA's would be a little pricey consdering I'm building eight channels. I'm using the LME49710 to start.

Click to expand...

I think the ICs will be fine, 22 discrete opamps is getting a little silly (must send that memo to Jaakko :green: )


Re the clicking with the switches - if you have no joy figuring out what's happening you could try posting on Bruno's forum at PSW. There was a nice discussion there on this topology a while back. Dave Collins, Bruno and others were discussing the merits.

I've committed to building one of Igor's Sontecs with Elma's throughout and Forssells on the input and output. It will end up being pricey but should be a nice thing.

Be sure to post pics when you get a stereo box up and running.

Cheers,
Ruairi

api made some EQs with IC op-amps in the filter and a DOA doing the summing and a final DOA driving the transformer... sounds like a sane approach.

Keith