A mere 50 years of misunderstanding

[Pilgrim]

I've been surfing info about the Standby switch on my 1967 Fender Bassman and it appears that I've had its function backwards since I got it 50 years ago.

As a radio/TV guy, I always assumed that the proper sequence for turning on this kind of gear was first to turn on the Standby (assuming the meaning is literally "OK boss, I am awake and standing by for orders..."), then to turn the Power switch on when I was ready to make noise.

When taking a break, I have always turned Power off (down) and left the Standby switch in the Up position. In other words, I assumed that Standby On meant "Power is partly engaged, I'm standing by for action."

Now I gather from readings on a variety of websites that I've had it backwards.

It appears that I should have been flipping up the Standby switch first, then turning the Power switch on (upward position) when preparing to play.  When taking a break, it appears I should leave the Power switch on/up and flip the Standby switch off/down position for breaks.

There is much lack of clarity in the language and functional definition of Standby switches.  It is unclear whether leaving the switch in the Up position is "Standby On" or "standby Off." And given the lack of clarity around what Standby actually DOES, is "Off/down" the Standby engaged position, or is it Standby disengaged?

I figure that aside from the potential of prompting train/tunnel, airplane and tank jokes, I can get better info here than any place I know.  So kindly illuminate this poor Padawan, compadres.

• What does the fabled "Standby" switch do?
• Is On/up engaging the function of this switch, or does Down/off engage the function?
• In what sequence should Standby and Power switches be used, (a) turning the amp on, and (b) when taking a break?
  

[Rob]

Being old and playing tubes early on we would bring up power as soon as possible and leave the amp on standby.  (Think Midwest and cold weather )
I was always told that it was good for the filaments but it could be folklore.

[Basvarken]

Yep, I always switch the amp on as soon as possible to warm up the tubes properly before actually using the amp.
Of course I leave power on during a break, using the standby knob to silence the amp, while keeping the tubes warm.

[lowend1]

The popular theory was that the standby switch, by not allowing full voltage to hit the tubes immediately, helped prolong tube life. You hear tales of a boogeyman called "cathode stripping" from not "preheating" the tubes by using the standby.  Opinions differ on whether the standby is even necessary, in part because tube hi-fi amps don't generally use them - but the majority of the tube hi-fi gear I've owned has been tube rectified, so I guess that debate can continue... They are less common on small amps (lower voltages), and typically those with a tube rectifier because they "turn on" slower than their solid state rectified brethren.
Psycho, yer thoughts?

[amptech]

A stand by switch should always be used on tube gear, and as mentioned above it lets the tubes warm up before high voltage is engaged.
Some tubes warm up ok within 10-15 seconds or so, but I usually recommend at least a minute or two. There is no point powering up the amp three hours before using it, you actually wear out tubes somewhat that way too. Most tube datasheets will tell you how long a tube needs to be warmed up.

Amps with very high voltages, silicon diode rectifiers and no stand by switch wear out tubes fast and sometimes develops issues with the amp because of that. but that does not mean that an amp with a tube rectifier is 'safe' without a stand by switch. I've had maaany VOX AC30's that powers up and within 2 seconds develops all kinds of horror that could be avoided with a stand by switch. Early Orange amps comes to mind too.

That said, remember that a small amp does not always run on low voltages. Many early 5W amps with a 12AX7/6V6GT/5Y3GT layout runs the B+ way over 400VDC.

Different tube rectifiers have different heat up time too, there are amps that use the indirectly heated 5AR4/GZ34 tube and does not have a stand by switch that should not be used with directly heated tubes - like the 5U4. Some directly heated tubes put out full potential very quickly. Then again some indirectly heated ones are wey nice and slow - I love the Bendix 6106 (a military 5Y3GT) - it is so slow warming up that a stand by switch is not needed.

Then, on top of that is the fact that some tubes of today is just not as stable as old ones. I'm thinking of the 5AR4/GZ34 tubes here in particular, many of the current ones have stability issues compared to the philips/mullard originals. Being a tube distributor I won't debate wich is better or worse, but lots of amps that made it without a stand by in the 60's might benefit having one installed today.

[BTL]

Power up sequence = Power "on", then Standby "on" = Amplifier is live.

Power down sequence = Standby "off", Power "off" - Amplifier is completely off.

[Highlander]

Hiwatt... standby off, power on... standby on when in use... standby off when resting... standby off then power off when shutting down... same with my old Marshall too...

[Pilgrim]

 

Power up sequence = Power "on", then Standby "on" = Amplifier is live.

Power down sequence = Standby "off", Power "off" - Amplifier is completely off.

Thanks, that addresses the basic question I'm asking.

From the explanations, it sounds like Standby sends voltage to half of the tube structure, and Power sends it to the other half. (I'm not clear on the difference between the grid, the filaments, and the cathode/anode functions.)

I notice that if the Standby switch is flipped DOWN, the amp ceases to function. Therefore I assume that Up = On for the portion of the tubes it powers.

When powering up the amp, I now understand Standby goes first, then Power. That's good, since that has been my practice. So far, so good.

I guess I only have one question left, since I have the power up and power down sequence.  (Thanks, BeeTL!)

During a break, which switch should be flipped to the DOWN position?  When I am playing and want to take a break, I have always flipped Power down and left Standby Up.  It now sounds like I should have done the exact opposite.

[Rob]

OK, still very basic questions:

From the explanations, it wounds like Standby sends voltage to half of the tube structure, and Power sends it to the other half. (I'm not clear on the difference between the grid, the filaments, and the cathode/anode functions.)

On my Fender Bassman, there are Standby and Power switches next to each other. In the UP position, is Standby On or Off?

I notice that if the Standby switch is flipped DOWN, the amp ceases to function. Therefore I assume that Up = On.

When powering up the amp, which should be flipped up first, Standby or Power? I have always flipped Standby up first, then Power. This may be precisely wrong.

So - during a break, which switch should be flipped to the DOWN position?

Once I am playing and want to take a break, I have always flipped Power down and left Standby Up.  It now sounds like I should have done the exact opposite.

Well yeah but "Standby" meant ready to go in the old Fender stuff .
I think the terms were reversed compared to what we are saying now.

[Pilgrim]

Thanks, Rob.  I apologize for editing my post a number of times so that what you quoted isn't exactly what appears in my post now.

[FrankieTbird]

Most standby switches are set up to cut off the hi-voltage supply to the tubes; the low-voltage to the heaters/filaments remains so that the tubes stay warmed up.  Turning off the power switch is the same as unplugging the amp, the circuit sees no voltage at all.

[Pilgrim]

Most standby switches are set up to cut off the hi-voltage supply to the tubes; the low-voltage to the heaters/filaments remains so that the tubes stay warmed up.  Turning off the power switch is the same as unplugging the amp, the circuit sees no voltage at all.

So if that's the case, when taking a break, the Power switch should be left on (up) and the Standby switch should be off (down). That will leave the low voltage /heaters/filaments on, but kill the high power side.

Glad to have some clarity on this after so many years! I did indeed have it backwards.

[Psycho Bass Guy]

So if that's the case, when taking a break, the Power switch should be left on (up) and the Standby switch should be off (down). That will leave the low voltage /heaters/filaments on, but kill the high power side.

Yes. Standby is more controversial among guitarists who tend to elevate every part of the signal chain except practice to near-religious icon status. Most bass amps made in the past 60 years already have one and need it and it should be used as described in the above quote. I've seen it recommended to never put the amp in standby once it has been in use already (ie- a set break) but I disagree.

[Pilgrim]

Thanks, PBG. I've always tried to respect heat up/cooldown cycles as an inherent maintenance item in using tubes, so it's comforting to me to finally get this sorted out. 

But I've also used a lot of tube gear in my life (as have all of us with grey hair). I don't find tubes to be as vulnerable as many of the younger set think they are. Granted they're not something you toss around like baseballs, but I've worked with enough tube equipment to feel that all they require is reasonable handling. IMO that includes respecting heat/cool periods.

[Psycho Bass Guy]

Thank Aspen Pittman's marketing of Groove Tubes in its early days for the ideas the kids have about tube life.  Between his and Mesa Boogie's asinine suggestion that tubes barely last six months (convenient when you sell them, no?) the modern myth about tube life exists. In the early days of Chinese and Russian imported audio tubes when dealers were selling REJECT tubes from said countries, caution was more in order, but making tubes is not rocket science and nowadays modern tubes equal the sound and robustness of nearly anything from the past. The most dangerous thing for tubes outside of vibration and physical shock is very rapid cooling of the envelopes, which will shatter them, but you really have to try to do that.