Quick question about the definition of "true bypass".

[Bill Mountain]

I'm working on a pedal design that will be using some tubes.  I want to have an on/off foot switch for power and then an on/off switch for the effect.  I want to do this so I can turn on the heaters for the tubes so they will be ready when I need the effect on.

The effect on/off switch will be wired true bypass so I figure that the pedal itself will be true bypass.  In your minds does true bypass have to include switching on and off the power at the same time?

Is there an easier way to do what I'm trying to do?

Thanks for reading!

[R.G.]

In your minds does true bypass have to include switching on and off the power at the same time?

No.

Read "The Technology of True Bypass" at Geofex - http://www.geofex.com.

[wavley]

To me the true bypass is only relevant for the signal.  It's nice to power something on and off to conserve batteries, but something you're not doing with tubes anyway.  Many around here would agree that everything being true bypass is a bit overrated.  I build a lot of stuff that's true bypass simply out of convenience because it's easy, but I have strategically placed buffers throughout my rig also.  But all that stuff is for another debate.  My real question is why you need a footswitch for your heaters, seems like a toggle for that would be just fine.  In the case of the EHX tube pedals which are true bypass via a relay the heaters are just always on, I have a couple of those and that setup works wonderfully.  A member of our board, puretube, is the one that designed the switching and power scheme for those things, you might try reading some of his musings on the subject.

edit: RG posted while I was typing, so... what he said

[Bill Mountain]

In your minds does true bypass have to include switching on and off the power at the same time?

No.

Read "The Technology of True Bypass" at Geofex - http://www.geofex.com.

I have read your site many times.  It's always a pleasure to see you on the board.  I will read your bypass article again (I read it many moons ago).

[Bill Mountain]

To me the true bypass is only relevant for the signal.  It's nice to power something on and off to conserve batteries, but something you're not doing with tubes anyway.  Many around here would agree that everything being true bypass is a bit overrated.  I build a lot of stuff that's true bypass simply out of convenience because it's easy, but I have strategically placed buffers throughout my rig also.  But all that stuff is for another debate.  My real question is why you need a footswitch for your heaters, seems like a toggle for that would be just fine.  In the case of the EHX tube pedals which are true bypass via a relay the heaters are just always on, I have a couple of those and that setup works wonderfully.  A member of our board, puretube, is the one that designed the switching and power scheme for those things, you might try reading some of his musings on the subject.

edit: RG posted while I was typing, so... what he said

I'm not stuck on my method of turning on the power.  I accidentally left a Valvecaster plugged in over night and I started to worry that I may do that again so, I was thinking of putting a foot switch with an led to tell me when the heaters are on.  I could use a small toggle switch as well, I just figured a foot switch is simpler.  Two small clicks with with my foot is easier than having to bend over to flip switches.

[iccaros]

To me the true bypass is only relevant for the signal.  It's nice to power something on and off to conserve batteries, but something you're not doing with tubes anyway.  Many around here would agree that everything being true bypass is a bit overrated.  I build a lot of stuff that's true bypass simply out of convenience because it's easy, but I have strategically placed buffers throughout my rig also.  But all that stuff is for another debate.  My real question is why you need a footswitch for your heaters, seems like a toggle for that would be just fine.  In the case of the EHX tube pedals which are true bypass via a relay the heaters are just always on, I have a couple of those and that setup works wonderfully.  A member of our board, puretube, is the one that designed the switching and power scheme for those things, you might try reading some of his musings on the subject.

edit: RG posted while I was typing, so... what he said

I'm not stuck on my method of turning on the power.  I accidentally left a Valvecaster plugged in over night and I started to worry that I may do that again so, I was thinking of putting a foot switch with an led to tell me when the heaters are on.  I could use a small toggle switch as well, I just figured a foot switch is simpler.  Two small clicks with with my foot is easier than having to bend over to flip switches.

Don't know that redundancy is a good reason to add another switch, read anther part that can break or need trouble shooting. I use a power strip for my amp and effects (APC filtered) and turn that off, so I know everything is off.
for the tube, leaving it on, will just reduce  a few hours of life, at these low voltages, really the heaters turning on and off will kill it first.. so a switch could lead to premature death if over used. I just leave mine on when plugged in and put a LED under the socket, one to make it glow more, two to remind me its on..

IF you forget to unplug it sometimes, you will also forget to turn it off, so 50/50 on benefit..

Case in point, I have my work like, and soldering iron on a switched outlet, the iron has its own power switch on its base, can you guess the number of times I have left to do something else to come back a while latter and find I left all of it on.. Two switches did not help....

[wavley]

I have nearly everything in my studio running to the same place mostly to avoid ground loops, so one flip of the switch and everything is off.  I've got a few lamps running off the same thing so that it's very obvious when the power is off or on, just to remind me to turn it off.

[Bill Mountain]

To me the true bypass is only relevant for the signal.  It's nice to power something on and off to conserve batteries, but something you're not doing with tubes anyway.  Many around here would agree that everything being true bypass is a bit overrated.  I build a lot of stuff that's true bypass simply out of convenience because it's easy, but I have strategically placed buffers throughout my rig also.  But all that stuff is for another debate.  My real question is why you need a footswitch for your heaters, seems like a toggle for that would be just fine.  In the case of the EHX tube pedals which are true bypass via a relay the heaters are just always on, I have a couple of those and that setup works wonderfully.  A member of our board, puretube, is the one that designed the switching and power scheme for those things, you might try reading some of his musings on the subject.

edit: RG posted while I was typing, so... what he said

I'm not stuck on my method of turning on the power.  I accidentally left a Valvecaster plugged in over night and I started to worry that I may do that again so, I was thinking of putting a foot switch with an led to tell me when the heaters are on.  I could use a small toggle switch as well, I just figured a foot switch is simpler.  Two small clicks with with my foot is easier than having to bend over to flip switches.

Don't know that redundancy is a good reason to add another switch, read anther part that can break or need trouble shooting. I use a power strip for my amp and effects (APC filtered) and turn that off, so I know everything is off.
for the tube, leaving it on, will just reduce  a few hours of life, at these low voltages, really the heaters turning on and off will kill it first.. so a switch could lead to premature death if over used. I just leave mine on when plugged in and put a LED under the socket, one to make it glow more, two to remind me its on..

IF you forget to unplug it sometimes, you will also forget to turn it off, so 50/50 on benefit..

Case in point, I have my work like, and soldering iron on a switched outlet, the iron has its own power switch on its base, can you guess the number of times I have left to do something else to come back a while latter and find I left all of it on.. Two switches did not help....

I had an instructor that had his soldering iron hooked up to one of those timer outlets (like you see in some bathrooms).  He turns it to get more time every 20 minutes or so.  He prefers that to leaving his iron on and causing a fire.

[boogietone]

I can just imagine the gig where the guy turns around to his band mates and says "No more extra tags at the end of the songs. You know I can't do more than a 20 minute set." 

True bypass deals with the signal. It's cool if you want an extra power switch, just stick a second LED to let you know the powered state in addition to the effect on/true bypass LED. I would use a toggle myself in this case. But, during a session or a show, I would not be turning tube heaters on and off. Get 'em hot and leave 'em hot. They will be happy. The simplest solution is to use a power strip that has a on/off light. Then the power to everything is covered.

[R.G.]

If I was worried about heater time on in this kind of situation and didn't want to have a physical switch, I'd use an 8-pin microcontroller and a dual opamp. The dual opamp would amplify the signal up by X amount till I could reliably sense audio coming through above noise levels. Then I'd use the A-D converter in the uC to sense the audio above X level, and when it senses, turn on an output that turned on the heaters.

Internally, the uC would count seconds and hold the heaters on for an hour (or whatever you chose) after the last audio was sensed, and then turn the heaters off. That ought to cover starting up instantly after a break, and would guarantee it would go off if left powered overnight.

You want to leave heaters on while the practice or session is going and not turn them on when you punch the footswitch, because heaters take 10-30 seconds to get the tube up to operating temp.

[Bill Mountain]

If I was worried about heater time on in this kind of situation and didn't want to have a physical switch, I'd use an 8-pin microcontroller and a dual opamp. The dual opamp would amplify the signal up by X amount till I could reliably sense audio coming through above noise levels. Then I'd use the A-D converter in the uC to sense the audio above X level, and when it senses, turn on an output that turned on the heaters.

Internally, the uC would count seconds and hold the heaters on for an hour (or whatever you chose) after the last audio was sensed, and then turn the heaters off. That ought to cover starting up instantly after a break, and would guarantee it would go off if left powered overnight.

You want to leave heaters on while the practice or session is going and not turn them on when you punch the footswitch, because heaters take 10-30 seconds to get the tube up to operating temp.

That is one hell of an idea.  Just like my tube amps I leave my tube pedals on for the entire session/practice/gig.  I think a plain foot switch or toggle will work just fine for me.