The Steel Guitar Forum

I just acquired a Fender Deluxe Reverb from the 80's (silver face model with boost feature). This is my first tube amp and I bought it knowing that there is a care and cost factor involved.

First, Standby. I know it has to be active when I switch the amp on but when else should I use it. Example: Between sets in a gig, should I switch it to standby?

I know that the tubes should be replaced periodically. I guess there are is no metric to say how often but what are the audible or visual signs that this is service is due?

Is this something akin to changing a lightbulb or does it require a specialist amp repair guy to do?

Thanks in advance!

\ paul

On my Twin Reverb, I usually put the amp on standby when plugging and unplugging the guitar chord, or like you say, between sets. That way, it's ready to go when you are.

When I had my Twin, the music shop guy told me to have the standby switch in the down position,and turn on the power switch. After the tubes warm up a bit, you flip the standby switch to allow sound to come out. Don't know if that is true, but I and the guitar player in the band, always did it tht way.

Richard,
I agree with you. I believe it is easier on the tubes to have them on standby than to be turning them on and off repeatedly.

Paul Seager wrote:
...First, Standby. I know it has to be active when I switch the amp on...

Not true. It really doesn't matter if the standby switch is on or off when you turn on the amp.

...but when else should I use it. Example: Between sets in a gig, should I switch it to standby?

That's probably a good idea. It will prevent feedback and noise if someone kicks the volume pedal down, or pulls the cord out of your pedal.

When the amp is doing something it shouldn't, on not doing what it should, it's time for service!

I've recently been reading up on tube amps, and talking with some builders/technicians. I was surprised by the information available regarding standby switches.

I get the impression that 'standby' switches are more of a design/marketing mishap, and that in general they do not extend tube life - and tend to introduce more points of failure without much benefit.

There are other people more knowledgeable than I by far on these boards who can probably explain it better -- and I am sure there are differing opinions.

Here is a wonderful, lengthy, article from Peavey about it, which is a good read for anybody interested in tubes:

http://peavey.com/monitor/pvpapers/Chapter6.pdf

and a much shorter, less technical article:

http://www.londonpower.com/standby-switch

Based on the Peavey article, it seems like putting your amp on standby during 15-20 minute breaks is a good way to induce 'Cathode Poisoning' within your tube.

Personally, I've been just leaving it in the 'operate' position and turning the volume down on my amplifier.

The stand-by switch is essentially there so that the tubes have time, about 15 seconds or so, to heat up BEFORE the high voltage is applied to them. This extends tube life compared to slamming a cold tube with the high voltage.

Amplifiers like Twin Reverbs and other modern amps that use solid state rectifiers in the power supply should have a stand-by switch and it should be used.

Tube amps that have tube rectifiers don't really need a stand by switch because the tube rectifier takes time to warm up. That high voltage isn't present until that rectifier tube gets warm. This creates a soft and gentle power ON to the tubes. On my Deluxe Reverb amp I always just flip both switches up at the same time and let the tube rectifier do the work of a safe and gentle start up.

For setbreaks and pauses, it's generally a good idea to go into stand-by mode as it will let the tubes cool down and rest when not in use. It's true that you don't want to leave an amp in stand-by for extended periods of time. The hot tube in stand-by mode can eventually "poison" the cathode because all those free and floating electrons don't know where to go. So they say.

But stand-by switches in tube amps with solid state rectifiers are a GOOD IDEA, not a marketing scam. There's good science to support it. Basically the reason comes down to extending the lifespan of our expensive tubes. Other than that, it's not critical, but it is advisable.

Brad

And it's important to add- if you have a tube amp with no standby switch, turn on power with the volume off. And wait a minute before playing. Half a minute. All tube amps need to warm up. As stated, standby mode is so that you can hear up the tubes before putting sound thru them. Cold tubes will play, but you will be ripping electrons of the cathodes in a violent manner, rather than warming them and gently coaxing them to willingly give it up. (This advice applies to something else, I just can't remember what...)
Hard to imagine standby mode being harmful if used for a long time. Ah, there it is in the longer peavey article. Sounds like if you use it for over 15-20 minutes there is a sort of "battery terminal corrosion" kind of thing, on a molecular level. But once you've warmed up the amp, half a minute, the standby mode isn't of any value anymore. The tubes are warm and the amp is ready to play. As far as noise or feedback goes, you can just pull the cord, if you don't want to turn off the volume knob.

Check this article out concerning the use of standby switches on an amplifier, Peavey or otherwise;
http://peavey.com/support/technotes/har ... pter_6.pdf

Brad, I have a question for you about this statement, "The hot tube in stand-by mode can eventually "poison" the cathode because all those free and floating electrons don't know where to go." Are you saying that the the tubes would be effected by this, the power tubes and the pre-amp tubes? How long would you have to leave it in standby mode for this to effect them? Also, would this damage anything else in the amp?

Hartley is right on the money on this, IMO. Use the standby switch especially with solid-state rectifiers and non-controlled-warmup rectifier tubes like 5U4 or 5Y3. I generally use a 5U4 with a Deluxe or Vibrolux Reverb, rather than a 5AR4/GZ34. The main reason is that, especially for a Deluxe with 6V6 power tubes, the plate voltage is already mercilessly high even with a 5U4 - but yet higher with the low-voltage-drop 5AR4.

Myself, I mostly use the standby only for a few minutes in the warmup phase. Once I get a tube amp warmed up, I don't turn it off (or on standby) until the rehearsal/gig/practice-session is done. I do generally turn the amp volume down on a break. But I believe more wear and/or potential damage can occur to components when being turned on and off than just sitting there idling with no signal applied.

I think what Bob wants to know is which components might have been already damaged by improper use of the standby switch? Power tubes? Preamp tubes? Anything else?

What we hear from our tube amps is so subjective that now we can't trust our ears for worrying about damage already done. What to do? Replace the power tubes? Then stop using the dumb switch after a one minute warmup?

Paul Seager wrote:
I know that the tubes should be replaced periodically. I guess there are is no metric to say how often but what are the audible or visual signs that this is service is due?

I

\ paul

They first tube to go is usually the reverb one. Check it by turning down the reverb when the amp is making weird sounds. Just replace it. No worries. For the power tubes I wait till they go bad before I mess with them. It happens very rarely so I have a tech guy check the bias. You can find a bad tube by tapping them lightly while the amp is turned on. The bad one will be micro phonic. Sometime a tube will glow bluish if it is going bad.

If it's one of the non power tubes you can replace them with no problems by yourself.

Standby is to save the tubes. On = power first, wait 30 seconds or so and standby on.

Power off = leave the standby on and turn off the power. This drains the capacitors.

You don't have to put the amp on standby during breaks.

If the tubes are good, I doubt that you will have to replace them for a good while. Tube quality is abysmal these days so I wouldn't mess with them unless they go microphonic.

Excellent article from Hartley, Mike Brown. Thanks for sharing.

This is exactly what Brad Sarno explained to me the other day when we were discussing the standby switch on a Revelation preamp.

I thought it was a defective switch as it did not cut the power immediately when switched to standby.

Brad said use the standby switch for powering up and powering down and that is about it.

If you're going to take a fifteen or twenty minute break,hich is better for prolonging tube life, leave the amp on or turn it off?

On gigs, I advise turning the amp's volume down and leave the switches on.

One big thing about warming up tube amps is the electrolytic caps... turns out that at higher temperatures the ESR goes way down (thanks Doug Roccaforte for that info)... so the amp sounds a lot better when fully warm. This may be one reason amps that are biased hotter sound better, up to a point.

Only use the Standby position when soft-starting the amp at the first of the night. Let the thing cook a good long time before your set... leave it cooking all night... turn the amp off at the end and put the Standby on so that it's ready for the next gig.

I have always used the standby between sets, etc.
I am mainly a 6L6 or EL34 power tube fan.
I recently bought a Vox AC30 30th anniversary model for six string. I was surprised to find that there is not a stand-by switch. I was also surprised that you have to pull the whole chassis to replace the EL84 tubes.
I have never been a fan of the EL84 tubes, but this amp does have a unique voice. It won't ever replace my Fenders though.
Lefty

I have a question regarding how and if, these suggestions apply to my Carvin BX 500. It only has one tube, a 12AX7 in the pre-amp. There is a switch on the back that allows me to use the tube or to bypass if for a solid state sound. The tube makes a big difference for steel. It is a bass amp, so maybe for bass or lead guitar, solid state might be better. Like always, it would depend on the players ears and type of music as to which would be best.

Thanks for any response.

My 74(?) Princeton Reverb doesn't have a Standby switch. I think my teck put in a 5V4 for it's slower warmup time. I'd have to drag out the amp and look to be sure.

Excerpted from the link Mark Fowler gve in his post:

Standby Switches and Folklore

Many guitar amps (too many) include a standby switch. This is meant to let the heaters warm up before the high voltage is switched on. Old books called it 'preheating'. But let's get one thing straight: a standby switch does not extend the life of the valves, in fact it is more likely to reduce their useful life. The valves do not care if you switch on the heaters and HT at the same time (with a couple of exceptions explained below). Now, I know what you're thinking, "but every guitar magazine in the land says the exact opposite?" Yes, they do, but guitar magazines know next to nothing about electronics, they just repeat the same old wives' tale each year.

Now I am really confused. After reading the post written by Peavey posted by Mike Brown I started to rethink things. I never used the standby switch to fire up or shut off my tube amps and seldom if ever used it when taking a break, but I did think it was for taking a break. Now I read the post by Mark Fowler and this link seems to say the opposite. How should it be used, or should we just have it removed from our tube amps?

well all I have is 50 + years experience to throw into the cake... I have used Fender tube amps non stop since the mid 60's , still do.

Theres too much technical jargon going on here...

Turn the amp on,. standby off, for a while, go plug your cords in, get yourself settled in. I never actually thought about how long the power was on, I just wanted to confirm the amp TURNED ON !

When ready to tune or play, turn on the standby. When taking a break, turn it off. OR NOT !

I did this for over 25 years with the same TWIN REVERB. Did the life of the tubes diminish ? perhaps but not in 6 months or a year..maybe 5 years ! Don't know don't care.

From 1995 to present day , same deal. I don't worry about it or even think about it. 5 different Fender tube amps of which I still own and use 4.

I change power tubes , not the matched ones, maybe every 2 or 3 years. It makes me feel better ! Pretty much the new ones sound just the same as the old ones. In over 45 years of playing gigs, I have not one time had a tube die on a Fender amp. Preamp tubes noisy ? yep, but the amps never died on a gig.

Me, I say plug it in, play and don't worry about it. Sure there is some reasonable technical advise stated here but at the end of the day those power tubes are gonna last a very long time ( years not months) whether you turn the standby on/off or whatever.

NOW seeing you bought an older amp, it would be wise to know what the maintenance was on the FILTER CAPS. IF you don't know just go ahead and have it recapped with quality filters and tube plate resistors. Then don't look back for another 15 years...

Yes, I do this maintenance on each of my Fender amps. The amps will perform with crummy tubes but will perhaps cause BIGGER issues with bad or leaking Filter caps, plus the tone of the amp will take a nose dive.

thats all I got...yeah I know, I'm odd guy out...

true story : When I went to electronics school back in the mid 60's I bought this 12 VDC to 117 VAC Car converter. I used to drive around with a Sony Tape deck in my car listing to rock and roll. One of our Instructors at school took issue with me during class and said those converters do not work. The whole class laughed. So we took a field trip out to my car, I turned it all on and played rock and roll on the tape deck. He listened and all he said was.."It's not supposed to work"... The field trip ended.


So whats the point of the story ? The theory of it all was trumped by the actual event.