Relay question

[Tdale]

I finished my first relay-board today, and am about to start on the second.

Should the amp be in clean or od mode when the relay is "off"...meaning when there is no current going through the coil? Or doesn't that matter?

I remember someone wrote something about the relay might make some more noise when the coil is active, and therefore either the od or the clean should be activated when the relay is activated.....

Tommy

[Bob-I]

I prefer OD channel on when the relay is OFF. I find the OD channel to be noiser than the clean channel. One time I had a noisy relay ckt that added noise to the OD channel.

Bottom line, if the relay ckt is quiet it doesn't matter, but if there's any noise at all it can add to the OD channel's noise more.

I hope that makes since.

[Luthierwnc]

Most DPDT relays come with one side activated unless the coil is on. You'll see the designation NC (normally-closed) for the side that the contacts are engaged. On these amps, you want the NC side be the boost off and OD off. Grounding the coil turns them on only as long as there is power running through the field. That is why if you leave them on when you turn the amp power off, you will hear them click when the field collapses.

If you look at the data sheets on Mouser.com, you'll see the contact blades drawn as they would be with no power. In the case of the OMI 212D relays, the switches have the pole in the middle. The normally closed throws are nearer to the coil lugs and the hot throws are at the end. BTW, you want non-latching relays.

http://relays.tycoelectronics.com/datasheets/OMI-2P.pdf

Remember, you can't check continuity (without power) after they are installed because the pole and the NC throw will connect automatically.

Skip

[Tdale]

Yes, I know what the normally on lugs are.

The reason I ask is because I want to add led's on the footswitch, and I planned to have a red led light up when the relay is activated, just like on the schematic someone posted here.

The problem is that the led only light up when the circuit is closed....and when the circuit is closed, the clean channel is the one that's active...

Here is a picture of the circuit I'm talking about:

https://tubeamparchive.com/download/file.php?id=896

I guess I could run a separate supply for the led, and use some of the available lugs on the foot switches (I got DPDT switches) and reverse it, so that the led lights up when the coil circuit is broken, and the OD channel is active....

Tommy

[d95err]

Some amateur speculations from me:

The channel switch relay is at the end of the preamp, so any noice added will be amplified by the same amount regardless if OD is on or off. The boost however is early in the circuit, so any noice added will be amplified by several gain stages.

I'm guessing that for the channel switch, it's a choice where you would like to add potential extra noice. The OD channel should already be much more noicy than the cleans, so perhaps a little bit of extra noice does not matter too much. If the cleans are really low noice, any extra noice could perhaps be more noticable there.

[Tdale]

I planned to use a 3-pin XLR or a stereo jack for the footswitch. But now I've decided to go for a 4-pin XLR, or even a 5 pin, just have have a little extra for future new ideas.

That way I use two pins for the two coils, one pin for power to the led's and one pin for the return to ground/negative side of bridge.

That way I can have he led's light up in what position I want, and I could even have red lights for OD/Boost and green lights for Clean/no boost

Tommy

[Luthierwnc]

Most folks just figure when the light is off, the effect is off. If you have a separate hot line, you can have the LEDs do whatever you want. There are Green/Red LEDs that light up either way. Choose the resistors for forward voltage drop and amperage.

http://www.us.kingbright.com/images/cat ... P59EGW.pdf

You need a DPDT stomper but those are readily available. Each switch gets its coil ground (shown on top) but you can use a common LED feed for all of them. The ground for the relays should be another isolated wire that attaches to the bottom half of the bridge/regulator circuit. Four wires for two relays.

sh

[Tdale]

Most folks just figure when the light is off, the effect is off.

I know. That's why I had a problem when I needed the led to light up when OD is engaged by breaking the circuit in stad of closing it.

I'll have to look more at your schem, and I'm goint to post a schem of what I think I'll be doing.

Tommy

[tictac]

the resistor should be in series with the LED and not in parallel. It sets the current draw of the LED. The LED will last longer with a series resistor of the correct value.

Here's one way to do it...

[Tdale]

https://tubeamparchive.com/viewtopic.php?t=1551

Here is my schem... does it look ok?

Tommy