HOW LONG SHOULD YOU WARM UP A 1200s OR SIMILAR AMP BEFORE HITTING THE STANDBY ON

[usersunn]

How long should you let the amp warm up before hitting standby and pumping the bass through it??

[Oli]

Hi,

do you mean an old 1200S with 4 KT88/6550 in it? It is rather important to let the tubes heat up, so there will be an exact info on the data sheed but im my case I let it run for app 1...5 minutes. I know a lot of guys who let their amps run for 1,5h to get the sweet tone, well...Ampeg says something about 25min for re-biasing, I think that sounds better.

Greetings

Oli

[usersunn]

Thanks Oli for replying. Ive been letting it warm up around 5 min before hitting standby...and yes, its a '69 1200s

[jbopper]

I certainly agree with the 1-5 min. rule with regard to tube heater warmup before hitting the plates and screens with high voltage (turning on the standby switch connects the H.V. rectifier output to the filter bank and then the rest of the B+ supply).  After another couple of minutes being fully powered up, you're good to go. 

As far as getting the amp up to full operating temp so that it sounds "good and sweet" and is stable for setting the bias, that's another story.  Just warming up the cathode heaters, whether it's for a minute or an hour, will not get you there.  You need to have the full plate voltage on and current running through the tubes.  The reason is that, for example, an EL34 with just the heater running is pulling 8.8 watts, but when you hit the standby switch and apply plate voltage, it is now drawing (and dissipating at idle) another 18 watts or so.  This example assumes 490 Volts on the plate and a bias current setting of 36mA -- a fairly typical setup in the 40W Sunn head.  Actually playing thru the amp for a while will get temp up a bit more although now, since most of that wattage is energizing the output transformer and powering the speakers, not that much more is being dissipated by and heating up the output tubes.  So when Ampeg says a 25 min. warmup for setting the bias, they don't mean run it on standby for that long and then do your adjustments, they mean 25 min. after the amp is fully powered up.  BTW, in my experience, you really need that much warmup to get the bias current good and steady.         

[Paul of the Bastards]

How informative!

[Mike B.]

Nice thread indeed! I always warm up all of tube heads (mostly old Hiwatts) for at least 5 minutes before I throw the standby switch and start cranking out the bass lines. It's such a habit for me that I even wait about 5 minutes before I start playing my old Coliseum Bass heads!!!

Mike

[Oli]

I certainly agree with the 1-5 min. rule with regard to tube heater warmup before hitting the plates and screens with high voltage (turning on the standby switch connects the H.V. rectifier output to the filter bank and then the rest of the B+ supply).  After another couple of minutes being fully powered up, you're good to go. 

As far as getting the amp up to full operating temp so that it sounds "good and sweet" and is stable for setting the bias, that's another story.  Just warming up the cathode heaters, whether it's for a minute or an hour, will not get you there.  You need to have the full plate voltage on and current running through the tubes.  The reason is that, for example, an EL34 with just the heater running is pulling 8.8 watts, but when you hit the standby switch and apply plate voltage, it is now drawing (and dissipating at idle) another 18 watts or so.  This example assumes 490 Volts on the plate and a bias current setting of 36mA -- a fairly typical setup in the 40W Sunn head.  Actually playing thru the amp for a while will get temp up a bit more although now, since most of that wattage is energizing the output transformer and powering the speakers, not that much more is being dissipated by and heating up the output tubes.  So when Ampeg says a 25 min. warmup for setting the bias, they don't mean run it on standby for that long and then do your adjustments, they mean 25 min. after the amp is fully powered up.  BTW, in my experience, you really need that much warmup to get the bias current good and steady.         

Hi,

thanks for the interesting reply. you are certainly right. I think 40% of Ptot is quite usual for Tubeamps in "Standby". Though I think there is a slight difference in the sound after one hour when u run it full power. But I think it`s save for he heates in the tubes to let them run for 1...5min. I do it that way: 1.) Switching on Amp 2.) Opening the beer (... in case the tubes get too hot to cool them down ) 3.) Put up my bass and effect paddles. So this already takes app. 5 min. Though I`ve just opend my 350B, I`ll check the actual Standbypower on the tubes as well.
As we do talk about heating up, the cool down is also very important and can shorten the tubes lives as the amp is pushed around after the gig with the hot heaters (the temperature in the tubes can go up to 250°C !!!).

Greetings

Oli

[noel]

+1 Oli haha  Turn that baby on and get a beer going.  Plug in and go.  I'm too impatient after a few minutes. 

[Isaac]

IIRC, lots of high fidelity tube amps have no standby switch, and do not suffer as a result. I'm not convinced that turning an amp on in standby and letting it warm up helps at all. On the other hand, it might help, and certainly doesn't hurt, so I do it anyway.

[usersunn]

Yes, I have a 1973 Oliver (of Ampeg fame) tube amp which has 2 RCA 6L6 blackplates in it, and it does not have a standby and has never given me a problem...

[Soundmasterg]

Many of the guitar amp gurus out there who write books about amps, such as Kevin O' Connor, say that a standby isn't needed in tube-powered musical equipment except as a stage mute feature. He states that in the case of a higher voltage amp such as the Ampeg SVT that is just starts to become a requirement to avoid cathode stripping. My 1956 Fender tweed deluxe does not have a standby switch, and many other vintage amps don't, and their tubes seem to hold up just fine. If it is there I'll use it, especially on stage, but I don't feel it is a necessary part of musical instrument tube amps to have a standby switch that limits the B+ until the heaters are warmed up as is traditional. Keep in mind that there are other ways to achieve a standby muting condition. The Silvertone 1484 and 1485 short the grids of the power tubes together, which results in an imperfect muting of the signal. Most vintage amps interrupt the B+, but many modern amps will just mute the signal for a standby mode. I'm fine with that personally. Even when a B+ style standby is there, you don't need to let the amp warm up for 5 minutes! 30 seconds is just fine.

Greg

[Oli]

Hi,

I checked the total power consumption of my 350B:

1.) Step down Transformer, Amp off, app. 6W
2.) Amp on, Standby, app. 60...65W
3.) Amp on, Volume 10, rest flat, 1000Hz signal, app. 240...260W

Yes, I have a 1973 Oliver (of Ampeg fame) tube amp which has 2 RCA 6L6 blackplates in it, and it does not have a standby and has never given me a problem...

..well, what about your beer?

Greetings

Oli

[Wally]

I have always been a subscriber to the 'warm it up on standby' until recently. There is a lot of info indicating that none of these amps deal in the voltages that would lead to cathode stripping. One aticle I read indicated that the voltage necessary to strip cathodes would be far higher than even the 600 and 700 volts of Ampegs, Musicman and like amps. That said, there is nothing wrong with using the standby. IT certainly doesn't hurt anything to warm the elements up before applying full voltage. I wholeheartedly agree with allowing the tubes to cool a bit before moving. This might be especially true in cold winter conditions...hot glass and extremely cold temps can lead to immediate ruination.

[loudthud]

The use of the Standby switch will limit voltage surges to the filter caps, especially in solid state rectified amps. This is important these days in Sunn amps because of the high B+ voltage. 60 seconds is sufficient. There are amps where this isn't an issue, but they don't have the Sunn logo.