Amp sounds better after it's been on a while.

[Boogie]

My silverface Deluxe Reverb sounds great, but after it's been on for 25-45 minutes, it opens up and really sounds glorious, even at lower volumes. I notice it quite a bit more at band rehearsals and gigs. Power tubes are good, so I don't think that has anything to do with it.

A friend told me that SRV used to turn on his amp and crank it up to 10 before he played for this reason: to get it nice and warmed up. Anyone else have anecdotes or technical explanation of why this is so?

[fenson]

Originally Posted by Boogie

My silverface Deluxe Reverb sounds great, but after it's been on for 25-45 minutes, it opens up and really sounds glorious, even at lower volumes. I notice it quite a bit more at band rehearsals and gigs. Power tubes are good, so I don't think that has anything to do with it.

A friend told me that SRV used to turn on his amp and crank it up to 10 before he played for this reason: to get it nice and warmed up. Anyone else have anecdotes or technical explanation of why this is so?

No ;but it is ture, IMO maybe something to do with electron flow , the warmer things get the faster they flow . Just my thoughts never payed much attention to why. If I took the time to study the Physics I would not have time to play guitar

[lennyb]

i notice the same thing with ALL my tube amps...i usually turn them on before supper and let them warm up while i eat ....by the time i come downstairs ...ahhh smooth tone for hours ....but if i turn it on wait 5 min and then play ...its just not the same.....so i don't think your crazy it true the warmer they get they Smoother they sound and i do believe it has to do with the warm electrons in the tubes

[Lance]

I use a Weber Mass to crank my amp. As the night goes on, I have to decrease the attenuation and amp volume as it'll get dirtier and dirtier as the night goes on. With my '65 BFDR, I'll start with the amp on 7 1/2 and by the end of the night, it'll be on 4 1/2 and be just as crunchy. With my 5E3, after around three hours....it's cooking (literally) and I turn the Mass completely off. The amp chassis after that amount of time are REALLY hot.


(it's called MOJO)

[Doug Ferguson]

I don't know why it's so, but that's long been my experience with tube amps. I keep my amp on all day, and through the day it just gets sounding better and better.

[bradpdx]

Originally Posted by fenson

No ;but it is ture, IMO maybe something to do with electron flow , the warmer things get the faster they flow.

Auggghhh!

OK, I'll calm down now. Sorry, but I'm an Electrical Engineer.

Electrons always "flow" pretty reliably at the speed of light. Temperature in this earthly realm is not a significant factor.

Tubes use heaters to warm up pieces of doped metal in order to create conditions that allow a lot of "free" electrons to become available from the metal. There is of course a strong function of temperature here, but the parts of the tube that are heated up by the filament reach a stable temperature pretty quickly - in less than a couple of minutes in most cases. After that, the tube behaves in a very consistent way. It certainly does not take 30 minutes.

If there is any difference in performance that appears to be a function time and temperature, it concerns other components. The most notable ones are the old school carbon resistors found in virtually all amps; in most cases the value of the resistor will go up a bit as it heats up. For the most part, the capacitors are unaffected, as are the transformers.

Remember, relative to a lot of things the temperature inside an amp chassis isn't really that hot. Cloth wires don't burst into flame, and many an old doobie has been found inside amp heads utterly unsmoked. Kinda dried out, but not smoked.

In most cases, an amp like a DR will achieve a stable chassis operating temperature in about 30 minutes. This only means that the resistors are now at whatever values they may settle at, but I don't expect the variations to amount to much.

I would not discount the psychological effect - I think that is really the majority cause. It just "seems right" that the amp should sound better when it is "warmed up", but in my own experience of many years on stage I have just not found this to be true. My old tube amps sound good within the first minute and stay there all night long. And that is how it should work.

[bradpdx]

I'll add a couple more things:

1. In older amps with original (30+ year old) resistors, the resistor values have often crept up. They do this even more when heated up, in my experience. If the resistors are new, they exhibit less of this behavior and are probably closer to specified values regardless. The old resistors are becoming chemically unstable.

This is one likely reason that some older amps appear to have more gain - the plate resistors have crept up 20% or so. If you have an old amp that changes a lot as it warms up, you may have a lot of old (plate) resistors. Change them for new resistors and the amp should stabilize, just like Leo intended.

2. If you wish to leave your amp on for long periods of time, take advantage of the standby switch. That turns on only the tube filaments and keeps the chassis warm without wearing out the tubes.

3. Cranking a tube amp doesn't usually cause the whole chassis to become much hotter, only a bit hotter. The only elements generating more heat are the power tubes, and they are exposed to the open air with no heat sinks connecting them to the chassis. Thus the difference in chassis temperature after an amp has been "cranked" is really pretty small.

This is very different from transistor power amps, because the small physical size of the devices (and greater temperature sensitivity) necessitates the use of heat sinks that frequently conduct all the heat through chassis components.

[Boogie]

Originally Posted by bradpdx

Auggghhh!
I would not discount the psychological effect - I think that is really the majority cause. It just "seems right" that the amp should sound better when it is "warmed up", but in my own experience of many years on stage I have just not found this to be true. My old tube amps sound good within the first minute and stay there all night long. And that is how it should work.

Typically I wouldn't discount it either, but it's definitely not my imagination. To me it does not "seem right" that once heated enough to pass electrons, the tubes should behave any differently as the amp warms up more, but your suggestion that the resistors behave differently is as close to a good explanation as I've heard.

My other tube amps do not do this, only the SFDR. My DRRI (recently sold) and Boogie Mark IV behave the same after 60 minutes as they did after 60 seconds. Ditto with both of my Twins, although they don't get much stage use so it's possible that my SFTR may be the same way.

[bradpdx]

Originally Posted by Boogie

My other tube amps do not do this, only the SFDR. My DRRI (recently sold) and Boogie Mark IV behave the same after 60 minutes as they did after 60 seconds. Ditto with both of my Twins, although they don't get much stage use so it's possible that my SFTR may be the same way.

I would count that as (possibly) empirical evidence that the old resistors in your SFDR are the culprits.

I replaced all the important resistors in my '65 BFDR long ago with much higher grade components with better temperature ratings. The result is a very stable amp that is quiet and consistent.

[11 Gauge]

When I saw the title of this thread, my mind immediately went to plate resistors.

Typically what I'll do is measure the old carbon comps, and then spec out a bunch of carbon films until I find ones that are close to the drifted value of the old CC's. I also save the old ones - bag em and tag em with info re: which gain stage they came from. In the event I have to tweak the carbon films a bit more, I will temporarily sub back in one of the originals.

Many times, folks for get about the B+ droppers on the rail. They can have the biggest affect. I like to start with those.

[bradpdx]

Originally Posted by 11 Gauge

When I saw the title of this thread, my mind immediately went to plate resistors.

Typically what I'll do is measure the old carbon comps, and then spec out a bunch of carbon films until I find ones that are close to the drifted value of the old CC's. I also save the old ones - bag em and tag em with info re: which gain stage they came from. In the event I have to tweak the carbon films a bit more, I will temporarily sub back in one of the originals.

Many times, folks for get about the B+ droppers on the rail. They can have the biggest affect. I like to start with those.

That's good advice for someone who wants to recreate the sound of an "aged" amp with more reliable parts. Alternatively, you can replace the plate and B+ resistors with new ones of the original values and wind up with a "like Leo intended when it was new" amp. Either approach is fine.

[woodman]

i've noticed this since i started playing tube amps in (gulp) the '60s. theory aside, in practical terms, hot tubes just sound better. i turn my amp on standby for about 3-5 minutes as soon as i set it up, then put it on full power for the rest of the night. i never put it on standby between sets so they can stay hot. some will argue with this method, but it's worked for me over 40 years of playing.

[Rumble]

I've thought the same thing- that my amps sound better after I've been playing through them for about 30 minutes. But I suspect it may be psychological and that my hands and timing may just be getting warmed up, and as I get into a groove everything just sounds better. This may be why so many guys "find" the perfect guitar after an hour of trying out 10 of them at their local GC.

[Paul in Colorado]

I don't notice it so much in my Fender amps, but I really notice it in my AC-15. After about a half an hour, it just gets much more toneful and seems to compress a bit more. Don't know why. It's less then ten years old.

[Boogie]

Originally Posted by Paul in Colorado

I don't notice it so much in my Fender amps, but I really notice it in my AC-15. After about a half an hour, it just gets much more toneful and seems to compress a bit more. Don't know why. It's less then ten years old.

Which models/eras of Fender amps do you have?

[fenson]

Originally Posted by bradpdx

Auggghhh!

OK, I'll calm down now. Sorry, but I'm an Electrical Engineer.

Electrons always "flow" pretty reliably at the speed of light. Temperature in this earthly realm is not a significant factor.

Tubes use heaters to warm up pieces of doped metal in order to create conditions that allow a lot of "free" electrons to become available from the metal. There is of course a strong function of temperature here, but the parts of the tube that are heated up by the filament reach a stable temperature pretty quickly - in less than a couple of minutes in most cases. After that, the tube behaves in a very consistent way. It certainly does not take 30 minutes.

If there is any difference in performance that appears to be a function time and temperature, it concerns other components. The most notable ones are the old school carbon resistors found in virtually all amps; in most cases the value of the resistor will go up a bit as it heats up. For the most part, the capacitors are unaffected, as are the transformers.

Remember, relative to a lot of things the temperature inside an amp chassis isn't really that hot. Cloth wires don't burst into flame, and many an old doobie has been found inside amp heads utterly unsmoked. Kinda dried out, but not smoked.

In most cases, an amp like a DR will achieve a stable chassis operating temperature in about 30 minutes. This only means that the resistors are now at whatever values they may settle at, but I don't expect the variations to amount to much.

I would not discount the psychological effect - I think that is really the majority cause. It just "seems right" that the amp should sound better when it is "warmed up", but in my own experience of many years on stage I have just not found this to be true. My old tube amps sound good within the first minute and stay there all night long. And that is how it should work.

Thanks for setting me straight Tech geek, on the electron flow stuff Good to have people in the know around.

[Jimo]

Maybe it is not the tubes but every tube amp I have played sounded better after about 30 minutes of warming up----heck even "I" sound better after 30 minutes of warming up---------------- JIMO

[woodman]

while i respect the theoretical considerations, i don't think it can all be dismissed as "psychological." the theoretical world and the mojo world are two different things.

try this: next time you play a three-set gig, put your amp on standby during first break and try to observe how long it takes for the amp to "come back to life" when you start second set. then on second break, leave it on full power before you start third set. see if you notice a difference. i do. hot tubes just sound better!

[bradpdx]

Originally Posted by woodman

hot tubes just sound better!

All I am suggesting is that "hot resistors" might be a more accurate description of what is happening. I don't think the temperature inside the tubes changes much after the first minute, all else being equal.

Either way, there is a possibility of "better sound" after the higher temperatures are achieved. That might indeed be true.

I have played with this effect on stage, and in my case (heavily rebuilt BFDR) it just doesn't make much of a detectable difference AFAIK. Maybe my newer higher wattage plate resistors just don't care so much.

[mwaym]

I have a Kuston tube 12a amp. It just has a tube pre-amp, and I can tell a difference after about 30 minutes or so !!! The amp seems to "come to life" then. It's a noticeable difference .

[Paul in Colorado]

Originally Posted by Boogie

Which models/eras of Fender amps do you have?

'66 Deluxe Reverb
'68 Bandmaster Reverb
'69 Dual Showman Reverb
I use a 2 X 12" small Bassman-style cab with JBL K-120's with the last two amps.

[wierdOne]

For a long while i was completely immersed in the world of tube microphones.... I know studio guys that actually leave their tube mics on ALL YEAR LONG....

strange.... but MANY of the studio guys I've talked to subscribe to this type of theory....

I use a CAD VSM at home (never understood the Neumann price vs. sound comparison).... it's a semi cheap tube microphone.... and yes... it does respond and sound better after it's been on for a couple of hours...

Bear in mind that common practice is to hang tube mics upside down to allow the heat to escape upwards....

just food for thought...

oh yeah... I've got an amp with the powertube section in the bottom of the amp to eliminate the hum of that the power transformer creates when cranked AND to allow the heat off the powertubes to escape.. without putting wear and tear on the preamp components....... and on a 3 hour gig.... NO fluctuation in the sound.... but it's got a TON of mojo.... consistent mojo..

so the heat theory sounds VERY reasonable as to fluctuation in response of the amp... but not so reasonable when talking about amp mojo.....