Express build burn-in

[mss1]

"Question asking is an imperative part of the learning process." I need to cram for this test...

Now that I did the filament transformer burn-in on my new Celestions for a couple of days, I want to do the same for the components in my amp.

I have read it takes about 100hrs for the caps and other components to smooth out and wonder if there is an accelerated process for this. Can you share your experiences?

Rather than going at it by individual components, does it make sense to just run a signal through the whole amp?

Using the low level hiss as white noise sounds like a reasonable idea, but does that really drive the whole frequency range? Would another test signal or a varied musical track be better to imitate the normal frequency variances and dymanics of a guitar? Perhaps a looped recording of a guitar track chugging and singing?

Do we really need to drive the power tubes for a complete burn-in? (I do have older sets and microphonic pre-amp tubes that could be used for this, but would like to save this wear if possible.) Would it suffice to pull the power tubes and focus on excercising the Preamp and PI tubes, signal capacitors and components?

If I need to burn-in the power tube components as well, I was thinking of using an airbrake with an iso-cab, to run the amp overnight for a couple of days. Playing at sufficient volume levels at home would take me forever and I couldn't stand the noise level (from the girlfriend)...

How high should the (amp) volume be, so the burn-in is effective? I don't want to gererate to much continuous heat or strain (amp or girlfriend) over long periods...

Any other considerations?

Zip008

[ampgeek]

Greetings Zip,
Although I don't know the answers to all of your questions, I recently built an Express and contemplated all of the same items that you are.

I ended up pulling the power tubes, setting the knobs at the postions that had sounded the best to me before the burn in process, wiring up an iPod set for continuous play in the classic rock genre and letting it rip over night for a week (~80 hrs). I even left in the pre-amp tubes that sounded the best pre-burn in.

I can't say objectively whether or not the burn in process is complete...but...it sure sounded a whole hell of a lot better (e.g., smoother, a tad more responsive, more musical to my tin ears) than it did prior to the burn in.

I have since played it live for ~20 hrs and it seems to be holding pretty steady as is.

Hope this helps,
Dave O.

[Cliff Schecht]

My amp has had enough time to do its own "natural" burn in. I've played it for hours on end going between band practice and bars in one night on many occasions. I think the sound has changed slightly at most, but it seems for the better. Something I noticed is that I find myself turning up the treble and presence just a bit more than I used to, but that could be changing tastes as much as it would be the amplifier actually mellowing out. It's hard to do such subjective tests without doing some sort of A/B test. A good way to do this is to finish a build, setup a cab and mic in a corner and record a clip. Without moving the cab or mic, burn-in the amp using your favorite method and record another clip playing the same riff. This would tell you how much the sound has changed.

I think on my next Express I'm going to do a gamut of lab style tests for frequency response, THD and what not. I'll take some measurements every few months and see how things have settled in over time. I think it's time we take a more scientific approach to Express building!

[Zippy]

I think the sound has changed slightly at most, but it seems for the better. Something I noticed is that I find myself turning up the treble and presence just a bit more than I used to, but that could be changing tastes as much as it would be the amplifier actually mellowing out.

Or the amp is sounding more mellow as your ears lose high frequency response.

[M Fowler]

I find myself turning up the treble and presence just a bit more than I used to

Cliff when gigging I find I increase the cut control (amps that have one) or treble to cut through the mix and hear myself. At home the Express is really brite to my old ears.

Mark

[selloutrr]

becareful using external signals i.e. ipods due to the line level versus instrument level mismatching. if you set it up as a guitar and then pound the input with a line level signal. you risk overloading your input stage and burning down your preamp or other components.

Make sure you level match if that is your plan.

I'm guessing the Express with the ipod burn in sounds smoother and duller because the first preamp tube is aged from the burn in. if you put a new preamp tube in the amp probably sounds the same.

I agree the components need to settle in to a point but most of the audible burn in process is speaker related. Otherwise it's just tube life you could be using for your enjoyment wasted on a dummy load or keeping the neighbors up.

I don't recommend you leave any amp / speaker running for more then 8 hours to prevent over heating. make sure the amp can breathe and keep the air moving. burning in speakers, due to the heat if you burn longer then 6-8hrs you can cause the speaker to burn up.

[wallybob]

Burn-in schmurn-in - practice your guitar through it and the amp will eventually be "burned-in" and you'll be a better guitar player to boot!

[WhopperPlate]

practice your guitar through it and the amp will eventually be "burned-in" and you'll be a better guitar player to boot!

+1 I have to agree with that, if you have the time and capability. Not that a burned amp doesn't sound any nicer.

[Cliff Schecht]

Burn-in schmurn-in - practice your guitar through it and the amp will eventually be "burned-in" and you'll be a better guitar player to boot!

That's kinda what I was implying with my last post (minus the playing better part ). I consider an amp burned-in if it stays on for a few hours and doesn't explode or fart out.

[mss1]

So it sounds like it is mostly the signal capacitors that would benefit from the excercise and the difference will indeed be marginal.

Because I will not have a lot of time for the "Just play it for the hours of break-in it takes" I guess I will go with the "it sounds a little more mellow now, I think", responses.

Thanks for everyone's advice, which I will integrate for the final recipie;

Sweet and Mellow Sozo's

- Crank it and record at least 1 hour of noodling and crunching,

- Loop the recording into the amp and simmer in the iso-box for about 8 hours.

- Provide ample airflow (checking for smoke and farty sounds/smells)

- Cool at room temperature for 16 hours (all day).

- repeat a second night and then check for doneness.

- repeat as necessary and enjoy with jam.

zip008

[paulster]

I've got a sine wave sweep which covers the guitar range that I leave on repeat into the front end for 24-72 hours with my disposable startup preamp tubes and no power tubes in.

The difference pre- and post-burn in is quite audible when you compare with the same tubes (good tubes, not the tubes used for burn-in) in so I reckon it's well worthwhile.