Jack for a footswitchable overdrive channel

[Mike_J]

I am in the process of developing circuitry for a footswitchable overdrive channel.  Part of that involves a jack that both energizes the relay and lights the led in the footswitch.
 
I have an extra three conductor cord that I removed from a two switch box I used on another amp.  Switched it to a five pin din plug instead.
 
I would think combining the three conductor cord with a Switchcraft 12B three conductor jack would provide the three necessary connections (ground, wire to the relay allowing it to be energized and wire to the circuitry for the led).  Does anyone have an opinion concerning the above or a better suggestion?  I will be using a single button footswitch.

Thanks
Mike

[TIMBO]

Hi Mike, You can use part of this circuit to do what you need.

[PRR]

2 wires.

[Mike_J]

2 wires.

PRR

Thank you for your reply.  The one button foot pedal that I will purchase for the amp comes with a two conductor plug.  Based on the Hoffman Relay System drawing I did (see attached) am I correct to assume a Switchcraft 11 type jack would be the appropriate jack for my purposes?  Also, would you please verify that the switch will work.  The switch would allow me to switch the overdrive on and off without having the footswitch attached.  Not too practical for gig purposes but it makes testing the circuit a lot easier.

Thanks
Mike

[Mike_J]

Hi Mike, You can use part of this circuit to do what you need.

Timbo

Thank you for your reply.  What I am trying to learn is what is the proper jack on the back of the amp for a one button footswitch / one relay amp.  I think it is a Switchcraft type 11 but just wanted confirmation from people far more knowledgeable than I am.

Thanks
Mike

[TIMBO]

Hey Mike, On some other relay switching I have just used standard switching jacks

[Mike_J]

Hey Mike, On some other relay switching I have just used standard switching jacks

Timbo

My apologies for my ignorance but what is a standard switching jack.  I have used a dpdt jack for the fet input on a Dumble clone but have never used one in a relay circuit.  Do you know why a Switchcraft type 11 wouldn't work?  It just has the tip and the ground which is what I think is required to mate the amp to the footswitch.  Does anyone agree with this?

Thanks
Mike

[Willabe]

what is a standard switching jack. 

Switch is outlined in red. This type, insert plug and switch opens. Marshall uses Cliff jacks that on some have switch contacts also.

Doug sells both types in his online store.

           
             Brad     

[EL34]

I think you already have another post started about this, right?


See the top image on this page
Looks exactly what you are trying to do

http://el34world.com/projects/relay_switch.htm

[Mike_J]

I think you already have another post started about this, right?


See the top image on this page
Looks exactly what you are trying to do

http://el34world.com/projects/relay_switch.htm

I

Yes I do have another post started addressing this.  Just thought I would ask the question while I was responding to your reply.  Your layout led me to two questions.  One does the SPST switch allow you to energize the relay when no foot switch is plugged in and two is the jack a Switchcraft 12A?

Thanks
Mike

[EL34]

One does the SPST switch allow you to energize the relay when no foot switch is plugged in and two is the jack a Switchcraft 12A

Yes and Yes

Print out the diagram twice and study it closely to see both options
No plug inserted and a plug inserted

Follow the circuit path to ground with a colored pen

No Plug Inserted:
See the switch on the jack is closed when there is not a plug in the jack?
What happens when you flip the spst panel switch?
The relay coil now has a path to ground and the relay coil is energized

Plug Inserted:
If the footswitch is plugged in, it can energize the coil by providing a path to ground

[Mike_J]

what is a standard switching jack. 

Switch is outlined in red. This type, insert plug and switch opens. Marshall uses Cliff jacks that on some have switch contacts also.

Doug sells both types in his online store.

           
             Brad   

Brad

That looks like a Switchcraft 12A switch.  If so it would be consistent with the schematic he showed me on another post I have.  In that schematic he also uses a SPST switch.  I still don't see why the DPDT switch with the type 11 switch wouldn't work.  I try to avoid the Switchcraft jacks with the tip shunts where possible as I have had problems with them recently.

Thanks
Mike

[Mike_J]

Yes,

Print out the diagram twice and study it closely to see both options
No plug inserted and a plug inserted

Follow the circuit path to ground with a colored pen

No Plug Inserted:
See the switch on the jack is closed when there is not a plug in the jack?
What happens when you flip the spst panel switch?
The relay coil now has a path to ground and the relay coil is energized

Plug Inserted:
If the footswitch is plugged in, either switch can energize the coil by providing a path to ground

Thank you for your help.  Makes sense to me now.  That is exactly what I want it to do.  I will have to draw out a layout of your diagram tomorrow and post it.

Thanks
Mike

[EL34]

Two ways to ground the relay coil

Top image = no plug in the jacks - Panel switch can trigger the relay coil
12A switch is touching the jack tip

Bottom image = foot switch cable is plugged into the jacks
Note that the switch on the 12A jack is not touching the jack tip when a cable is plugged into it
Foot switch can trigger the relay coil

[Willabe]

That looks like a Switchcraft 12A switch. 

Yes it is.

I still don't see why the DPDT switch with the type 11 switch wouldn't work.

It might, I don't know. I think Timbo was thinking it would simplify things using the shorting jack?

Haven't heard anything about bad Switchcraft jacks but maybe they had a bad batch or they changed the metal they used?

They have been a solid company with very a reliable product for decades.


                  Brad     

[Mike_J]

http://el34world.com/projects/relay_switch.htm[/url]

I have looked at your drawing and have come to the same conclusion you did that it does the same thing my drawing does.  You schematic does not include a voltage regulator or the cap across the switch which I have been told reduces switch noise.  If the cap doesn't do anything I would sure like to know because it is a pain to wire.  Also, I am not sure why you put the led next to the 180R resistor.  Could you tell me what they do?

I personally prefer the type 11 jack over the 12A because I had trouble with a shunt on a 12A not long ago that took me an embarrassing amount of time to find.  Could be me or could be Switchcraft but I know the type 11 doesn't have a shunt so that is just one more thing that can't go wrong later on.

Thanks
Mike

[Mike_J]

That looks like a Switchcraft 12A switch. 

Yes it is.

I still don't see why the DPDT switch with the type 11 switch wouldn't work.

It might, I don't know. I think Timbo was thinking it would simplify things using the shorting jack?

Haven't heard anything about bad Switchcraft jacks but maybe they had a bad batch or they changed the metal they used?

They have been a solid company with very a reliable product for decades.


                  Brad     

Brad

After I had the problem with the jack I looked on the internet and a number of people were complaining about the 12As.  Seems the solution to fixing the problem is to take some 600 grit emery cloth and clean off that little nub on the shunt so it makes better contact.  Either something coating it so it does not make contact from the manufacturing process or corrosion.  I believe it was the former more that the latter.  That was not something you used to need to do with the old Switchcraft jacks that I can ever recall.

I am going to use two 12As on my latest amp as inputs although I don't know why.  Guess I will just have to pull out my emery cloth.

Thanks
Mike

[sluckey]

Also, I am not sure why you put the led next to the 180R resistor.  Could you tell me what they do?

You must use a current limiting resistor in series with a LED. The LED will burn out without the limiter. Also note that Hoffman's LED is on the amp chassis, not the footswitch. You will need to be more creative to use the LED on a footswitch.

You don't have to use a 12A jack, but it makes it convenient to disconnect the panel switch whenever you have the footswitch plugged in. Not all people care for that feature. You can just use a type 11 jack and just wire the panel switch parallel to the footswitch. Just be aware that if you turn the relay on with either switch, you must turn it off with the same switch.

If you would like to be able to have total control with both switches at the same time, then you will have to use a common "three-way" circuit. But that will require SPDT switches and a type 12B stereo jack. Here's a schematic. You may just want to keep the switching bare bones for a simple single relay control. I just wanted to show you some other options.

[EL34]

There's nothing wrong with 12A jacks


I always run a piece of double sided 600 emory down between the switch and the contact point, even on old fenders that used the same jack.
Oxidation happens on lots of different metal surfaces and the metal in 12A jacks is not different
Who ever said this does not happen on old 12A jacks is wrong


This is my service routine on old fender amps
Put a plug into the jack
insert a thin piece of folder over 600 grit or higher emory cloth
pull the plug out
pull the emory to clean the contact points
spray a bit of tuner cleaner

[Mike_J]

Also, I am not sure why you put the led next to the 180R resistor.  Could you tell me what they do?

You must use a current limiting resistor in series with a LED. The LED will burn out without the limiter. Also note that Hoffman's LED is on the amp chassis, not the footswitch. You will need to be more creative to use the LED on a footswitch.

You don't have to use a 12A jack, but it makes it convenient to disconnect the panel switch whenever you have the footswitch plugged in. Not all people care for that feature. You can just use a type 11 jack and just wire the panel switch parallel to the footswitch. Just be aware that if you turn the relay on with either switch, you must turn it off with the same switch.

If you would like to be able to have total control with both switches at the same time, then you will have to use a common "three-way" circuit. But that will require SPDT switches and a type 12B stereo jack. Here's a schematic. You may just want to keep the switching bare bones for a simple single relay control. I just wanted to show you some other options.

sluckey

I have attached a new layout that includes the footswitch I will be using for this project.  The footswitch has a 1K resistor to reduce the voltage to the led.

The way I want the panel switch to work is by energizing the relay when the panel switch is turned to manual.  This will be used mostly when no footswitch is plugged in.  I find it very helpful when tuning the related circuit as I don't need to have a footswitch in the way while I am working.  When I want to use a footswitch to energize the relay I plug it in and switch the panel switch to the Pedal setting.

Do you think the way I can accomplish the above with the components and layout I have on the attached drawing?

Thanks
Mike

[Mike_J]

There's nothing wrong with 12A jacks


I always run a piece of double sided 600 emory down between the switch and the contact point, even on old fenders that used the same jack.
Oxidation happens on lots of different metal surfaces and the metal in 12A jacks is not different
Who ever said this does not happen on old 12A jacks is wrong


This is my service routine on old fender amps
Put a plug into the jack
insert a thin piece of folder over 600 grit or higher emory cloth
pull the plug out
pull the emory to clean the contact points
spray a bit of tuner cleaner

I sure know a 12A can ruin your day.  Since so many amp problems are tied to jack problems your advise concerning maintenance of a 12A is wise and will become a routine practice for me if I have any problem whatsoever with an amp.  Doesn't take very long to do.

Thanks
Mike

[EL34]

It's no fault of the jack itself


It's just a natural thing that metal oxidises

[sluckey]

It's no fault of the jack itself


It's just a natural thing that metal oxidises

Just as a sidebar... I recently discovered a problem with 12A jacks. My problem is not the switch contacts. Those work fine. The problem I have is the insulator material separating the three lugs. I measure somewhere between 400K and 800K between between lugs. This is on six brand new jacks! Cleaning the jacks with cleaner or denatured alcohol does not help. The insulator material is just conductive!

You may say, well 400-800K ain't much, but it will make the 1M resistor on the input jacks look like 300K. No big deal if that's the only symptom. But, I discovered this defect while jumping channels on my AC-15. That leakage resistance will allow one channel to bleed over into the other channel even when you don't want it too.

Luckily I had some old NOS 12As. They did not have this insulator leakage problem like the newer jacks.

[sluckey]

Mike, read this thread, paying close attention to what Geezer says in reply #4...

http://el34world.com/Forum/index.php?topic=14348.0

Geezer explains how the footswitch you have operates. Basically, the LED will be illuminated whenever the relay is de-energized.

[EL34]

It's no fault of the jack itself


It's just a natural thing that metal oxidises

Just as a sidebar... I recently discovered a problem with 12A jacks. My problem is not the switch contacts. Those work fine. The problem I have is the insulator material separating the three lugs. I measure somewhere between 400K and 800K between between lugs. This is on six brand new jacks! Cleaning the jacks with cleaner or denatured alcohol does not help. The insulator material is just conductive!

Weird
I have not heard that before.
I went to the bin just now and measured 10 of them and then gave up

Got absolutely nothing between the ground lug and the tip lug
Meter did not even flinch


Were they some sort of Chinese copy jack?

[sluckey]

Were they some sort of Chinese copy jack?

They came from Mouser several years ago. All have the Switchcraft logo on them. I think they are legit. Ed Chambley had a very similar problem. I found out about it while helping him sort out why his jumped channel mod was not behaving on his AC-15.

The actual leakage problem was between the switch lug and the tip lug. Not between tip and ground. Insert a plug in some jacks and see if you have any jacks that have leakage resistance between tip and switch.

[sluckey]

Try this Mike...

[EL34]

Were they some sort of Chinese copy jack?

They came from Mouser several years ago. All have the Switchcraft logo on them. I think they are legit. Ed Chambley had a very similar problem. I found out about it while helping him sort out why his jumped channel mod was not behaving on his AC-15.

The actual leakage problem was between the switch lug and the tip lug. Not between tip and ground. Insert a plug in some jacks and see if you have any jacks that have leakage resistance between tip and switch.

Just did the same thing with a dummy plug
checking between the switch and the tip
Nothing, nada, not even 30 meg ohms


Maybe it was a bum batch that got recalled?

[sluckey]

Maybe it was a bum batch that got recalled?

Could be. I never got the recall notice!     I examined those jacks with magnifiers and good light. Never saw anything suspicious.

I'll buy my next jacks from your proven stock. 

[Mike_J]

Mike, read this thread, paying close attention to what Geezer says in reply #4...

http://el34world.com/Forum/index.php?topic=14348.0

Geezer explains how the footswitch you have operates. Basically, the LED will be illuminated whenever the relay is de-energized.

Sluckey thank you for the response.

I think I had a problem on the two Dumble Overdrive Specials with the NC channel lighting the footswitch.  Rebuilt my footswitches (started with $12 footswitches and ended up with $35 footswitches the components in those footswitches are substandard at best) and now they light when the relay is in the NO position.  Can't remember what I did but it might have involved reversing the wires.

I do not want the normal position of the relay to be in the NO position (energized) when the amps overdrive is off.  During the majority of time the amp is operating I would expect the overdrive to be off.  It is my understanding that the useful life of these relays may not be very long if they are staying energized for long periods of time.

Will have to put more time into researching and discussing this tomorrow.

Thanks for the time you devoted to this.
Mike

[PRR]

> my understanding that the useful life of these relays may not be very long if they are staying energized for long periods of time.

My heating furnace runs on a relay. (Low-volt thermostat must turn-on a high power blower motor.)

If you live in Maine, I assure you the furnace runs more than you can play.

Florida, same thing except the A/C relay. (Yes A/C "contactors" are relays, and they do fail; but they have to be quite beefy so are susceptable to being under-specified. Get a good one and it will out-last several compressors.)

Furnace relay failures are rare. I've never lost one.

It's not any kind of magic relay. I think most of the small jobs are better built than my furnace relay.

I used to know too much about relay-logic elevator controls. In many of these, one or more relays are mostly-on, 24/7 for 20 years. (And yes I knew too much because they DID fail, but mostly from bad-air on un-sealed contacts in dank equipment dungeons.)

Omiron G6E Data Sheet

There is data for clack-clack operation: "5 million operations min. (at 18,000 operations/hour)". High contact powers, and many-many clacks, are what wear-out relays. Not sustained coil-hold. Charts on the next page show how these numbers vary as you change the abuse on the contacts.

They do not give any data (that I found) for constant-on lifetime. They have every other number. And Omiron sells a LOT of relays. This tells me that they think constant-on lifetime is Not An Issue for any of their customers.

Think: a relay coil is wire. When will you wear-out the wire in your amplifier? Yes, old amps (like old tractors) get rotten wire. However the small sealed relays don't get as much bad air as the wires inside your amp.

Also, if you socket the lil bugger, you can pop it out and replace it in a jiff. (However you need a wire-tie to keep the relay in the socket; and you better buy your lifetime supply now because all DIP parts are going out of production in years ahead.)

Side-track: good general oversight of relay issues

[sluckey]

I do not want the normal position of the relay to be in the NO position (energized) when the amps overdrive is off.  During the majority of time the amp is operating I would expect the overdrive to be off.  It is my understanding that the useful life of these relays may not be very long if they are staying energized for long periods of time.

I would not be concerned with the life of the relay. The relay will probably be more reliable that the amp. I've worked with thousands of relays over my 40 year career with FAA. Many of those relays were energized 24/7 for years and years.

But, if you must have the footswitch LED illuminated when the relay is energized, you cannot use that footswitch as it is wired. I see two options.

1. Rewire that footswitch as PRR showed earlier so the LED is in series with the relay coil. This will require a higher dc voltage since the relay will want 5v and the LED will want approx. 2v. That's easy. Just don't use the 7805 regulator chip. All you need is the bridge rectifier and a 470µF cap for a supply.

2. Replace that footswitch with a DPDT or 3PDT that Doug sells. Replace that type 11 jack with a stereo 12B jack. Use a 3 conductor cable between the amp and footswitch. This will allow you to use two wires to switch the relay on thru one half of the footswitch, and use a third wire to supply power to the LED thru the other half of the switch.

And there is one other option. The dead nuts easiest way to do this is to forget about the LED on the footswitch. Put the LED on the amp and wire it as Doug shows.

[EL34]

I'll just add that if you are that concerned about replacing the relay, use a socket and you can relax 


Then all you have to do is unplug the relay and plug in a new one

[Mike_J]

I'll just add that if you are that concerned about replacing the relay, use a socket and you can relax 


Then all you have to do is unplug the relay and plug in a new one

I am using your relay board and your relay power supply board.  Both items are excellent.

Thanks
Mike

[Mike_J]

Sluckey and PRR

Thank you for your replies to my post concerning the viability of the relay.  I was probably misinformed about the reliability of the relays.  If the relays are reliable then all I need to do is reverse the NC and NO contacts on the relays and the problem is solved.

Thanks
Mike

[Mike_J]

Try this Mike...

Sluckey

When I had my PT made I included a dedicated 3.15 - 0 -3.15 @ 1A secondary to supply the relays and footswitch led.  I am also going to use it to power my 6 volt square indicator lamp because I have maxed out the heater secondary with the inclusion of the seventh preamp tube.

So do I use the CT or 100 R resistors on the 1A secondary or just tape it off when I lift all these grounds?  If I don't use either will any hum get injected into the amp?

Thanks
Mike

[sluckey]

When I had my PT made I included a dedicated 3.15 - 0 -3.15 @ 1A secondary to supply the relays and footswitch led.  I am also going to use it to power my 6 volt square indicator lamp because I have maxed out the heater secondary with the inclusion of the seventh preamp tube.

So do I use the CT or 100 R resistors on the 1A secondary or just tape it off when I lift all these grounds?  If I don't use either will any hum get injected into the amp?

Having a dedicated 6V winding simplifies a lot of things. You don't need to use the CT or any 100Ω resistors. Hum is not an issue. And you can connect the negative side of the 5V power supply to chassis. And you don't have to isolate the type 11 jack. And since you are no longer concerned about having the LED on when the relay coil is de-energized, you can use that simple drawing I did. And you can use that footswitch you have.

Everything is ready to go. I can't think of anything else to say about it.

[Mike_J]

When I had my PT made I included a dedicated 3.15 - 0 -3.15 @ 1A secondary to supply the relays and footswitch led.  I am also going to use it to power my 6 volt square indicator lamp because I have maxed out the heater secondary with the inclusion of the seventh preamp tube.

So do I use the CT or 100 R resistors on the 1A secondary or just tape it off when I lift all these grounds?  If I don't use either will any hum get injected into the amp?

Having a dedicated 6V winding simplifies a lot of things. You don't need to use the CT or any 100Ω resistors. Hum is not an issue. And you can connect the negative side of the 5V power supply to chassis. And you don't have to isolate the type 11 jack. And since you are no longer concerned about having the LED on when the relay coil is de-energized, you can use that simple drawing I did. And you can use that footswitch you have.

Everything is ready to go. I can't think of anything else to say about it.

Sluckey

Good news about the dedicated 6.3V secondary having its advantages.

Your earlier post about having the led on the faceplate of the amp made me think that would be better than average.  I doubt that there are a lot of DIYers that have a led on their faceplate indicating when their overdrive circuit is on.  I think I have decided that is the way I want to go.  LED on the faceplate and not on the footswitch.

I didn't purchase the footswitch yet so I will just buy what we finally determine is best.  I did a new layout diagram that includes a footswitch with no led and led and 180r resistor placement in the circuit.  I think I did it right but would you double check it for me please?

Doug's schematic does not include a 7805 voltage regulator.  Don't you think I should have one?  Also, do I just ground the center tag of the 7805 and ground the type 11 jack to complete the layout?

Thanks
Mike