Amp gurus...do preamp tube covers change an amps sound/tone?

[jasonP]

I can hear a difference in my slo clone amp. Thanks Dave!!

 

[glpg80]

Actually in my experience, frequency analyzers are pretty next to useless when it comes to decision making. You could have two very audibly different guitar tones and they both look the same or very similar through an analyzer. When we start talking about little tweaker splitting hair stuff like this that is tough for your ear to hear, you'd be wasting your time looking at an analyzer. If it makes enough of a difference to you that it makes you want to pick up your guitar and play more then it's a good change. There are some things that I can clearly hear in person when playing my guitar, but set up a mic and the difference is gone. It's just the way things are, don't fight it.

actually, spectrum analyzer's have extreme sensitivity and can easily manage well into the high Mhz - Ghz. however they are used for intensity level measurement and/or tracking RF/UF frequencies - not the same thing we are talking about here at all. as the discussion is about analyzing actual sound differences coming from the speakers - all of the signals are always going to be changing - impossible to compare two different signals in real time and look for a specific frequency due to speakers and other variables like microphones not being perfect. spectrum analysis would be jumping all over the place with fundamental frequencies and their harmonics always changing in real time as well.

in order for it to even work you would need to setup controlled variables. a signal generator, an RF cage for controlled interference, etc.

the effect this entire topic is mentioning is purely capacitive - a low pass filter created by a dialetic (air) and two plates - the plates of the tube and the tube cover attached to the chassis common ground. this creates a capacitor - a low pass filter.

the whole point i made early on is that it is independent of heat from the filaments. Dave mentioned altering the miller capacitance from anode to grid and this is 100% correct. technically speaking fender has mimic'ed this roll-off effect to round off high end notes. i have seen schematics that have done this before on purpose.

 

[JakeAC5253]

You know what would be a great comparison. Somebody should do this, seriously.

Get your amp off of your cabinet so that rummaging around through the amp will not disturb cabinet or mic position AT ALL. Record a DI signal into your DAW of you playing a riff, doesn't have to be too complicated, just something that you think will show the difference. Reamp the DI three times through the amp with all preamp tubes covers on so that you have A B and C recordings of the same input signal. Now remove all of the covers without disturbing the cabinet or mic and reamp the DI through it one last time calling this file D.

Now the fun part. Take track A and track B, which are both from the covered amp, and flip the phase on one of them. You will probably cancel a good majority of the reamped track because flipping the phase on one cancels the 'shared' data between them, that's alright though. Bounce that shit and call it "control". Now take C and D recordings and flip the phase on one of those, this will cancel out all of the shared information and what you are left with is the "difference" between the two tracks, if there is one. Now compare the control to the experiment and see what you hear.

Go on... I dare ya.

 

[petejt]

This sounds like a TGP thread.....................



That aside, only the V1 preamp valve in my amp has a cover. The rest are uncovered.

 

[FourT6and2]

I can tell a difference in my amp with the preamp tube covers on and off primarily on the V1 tube. The Tung sol in my combo amp is just barely microphonic and with the cover on, the extra noise that's produced by a slightly microphonic tube is diminished because it's not being jarred around by my 2x 12 speakers. So yes, there can be a noticeable difference.

But people aren't talking about mechanical noise or RF interference. They're saying there's a difference in the TONE of the amp. Which I find hard to believe. I have a Super Lead clone with preamp covers. I'll give it a try. But if I hear no difference I already know people are just going to respond with, "your ears aren't discerning enough..."

 

[JerryP]

The strength of analysis tools is that they give visualizations of quantitative data, which makes understanding the data more intuitive. One limitation of analysis tools is that using more than two or three at a time creates visual clutter. Small analysis windows are not very useful, so with four or five of them open at the same time, even a dual-monitor system must devote substantial space to meters. Constantly updating multiple, real-time graphic readouts is also taxing on a CPU.


There is also the human problem of paying attention. With too many dancing displays going at the same time, the analytical focus that was the impetus for using a meter in the first place becomes dissipated, and you can end up glancing from one meter to the next, trying to catch events that require attention. One way around this is to let the program watch the meters for you, alerting you when specified conditions are met. However, the only package I have found that implements alarms is Inspector XL.


Analysis tools give us useful data, but it is only data, not knowledge about the audio. So, in the final analysis, the ears remain the best and most important source of knowledge about whether something sounds good. But data can be seductive, and people sometimes come to rely more on what they think meters are telling them than on what their ears tell them. That becomes a problem if someone is not metering the appropriate information or if the quantitative data supplied by a meter does not map well to the most closely related perceptual attribute. For instance, level meters mostly give representations that are of the power in a signal. But loudness is a perceptual attribute that does not map directly to signal power as shown on a typical meter. Or the problem may be as simple as not metering the right parameter.


In any event, meters are best treated as supplements to what we hear. If there is a discrepancy between the two, further inquiry may be in order. But it is foolish to assume that the meters must be “right” and that you aren't hearing correctly.

Just a cut from an article in Electronic Musician on Analyzers I found from a link on the Blue Cat forum http://emusician.com/tutorials/emusic_analyze/index.html

From what I can read it sounds like these are reading and averaging the frequencies. That's not going to measure what you hear. It may be showing you all the frequencies present in the clips, but it doesn't show how they are put together. Knowing all the notes in a song does not make a song and if you put them together in a different order the song sound different while still having all the same notes in it.

Any differences from tube shields will be circuit dependent, frequency dependent, and gain level dependent. It's not going to be a remove the tube shield and you'll hear this rubber stamp change in every amp. Speakers, guitars, cables, etc, will all play into the final result your ear hears.

I do know there is a change in capacitance when shields are on, that's just basic electronics 101. How that change affects each amp or circuit will be different based on how that capacitance affects the tuning of the circuit. Very small changes that can make a noticable difference in the right situation. No different than trying one particular brand of tube in one brand of amp and noticing no difference, then trying it in another amp and it makes all the difference in the world.
Jerry

 

[LP Freak]

I can tell a difference in my amp with the preamp tube covers on and off primarily on the V1 tube. The Tung sol in my combo amp is just barely microphonic and with the cover on, the extra noise that's produced by a slightly microphonic tube is diminished because it's not being jarred around by my 2x 12 speakers. So yes, there can be a noticeable difference.

But people aren't talking about mechanical noise or RF interference. They're saying there's a difference in the TONE of the amp. Which I find hard to believe. I have a Super Lead clone with preamp covers. I'll give it a try. But if I hear no difference I already know people are just going to respond with, "your ears aren't discerning enough..."

Try it. I didn't really believe it either.

 

[degenaro]

I wonder why I have a box of tube shields on my shelf........

Because there's some interaction between the pre-amp tube's fields when you take the shield off...especially on old JMPs.

 

[glpg80]

fast fourier transform is a method of spectral analization using a sample frequency and applying limits dealing with nyquist rates. FFT = spectral analysis. spectrum analyzers were originally designed using bandpass filters.

if you dont know what the term is, you probably should not be using it

I really didn't care enough to look it up

considering its my major i had better know what it is

nothing meant by it dave

 

[killertone]

My head just exploded.

 

[dulrich1227]

My head just exploded.

haha mine to and i didnt even make it to my amp to take the pi covers off ....

 

[thegame]

While I do agree there is a difference, some boutique manufacturer will read this and come out with high priced tube covers that deliver better tone than generic tube covers. And it will sell at TGP.

 

[FourT6and2]

I use two shields on each tube. DOUBLE TEH SHIELDS. DOUBLE THE TONE!!! Just makes sense. it's natrual, let it happen.

 

[Ventura]

Hey everybody!

Did you know that electrons and photons behave differently when you observe them! Isn't that neat! When you're not looking they act as a wave. When you're staring 'em down, they behave as a particle! Supercool! So, next time you're playing your guitar and rocking out to some Poison or Gwar, take a peep at your preamp tubes and those totally rad (lol get the pun? rad...) electrons in your tubes will no longer be waves, they'll be particles. And that will change the sweet sweet tone of ur amps!

What the BLEEP do YOU know!!! Or are you even "further down the rabbit hole"???

Brilliant couple of shows if you've not already seen them

V.

 

[Greazygeo]

I wonder why I have a box of tube shields on my shelf........

Because there's some interaction between the pre-amp tube's fields when you take the shield off...especially on old JMPs.

Finally someone got it.

 

[FourT6and2]

Hey everybody!

Did you know that electrons and photons behave differently when you observe them! Isn't that neat! When you're not looking they act as a wave. When you're staring 'em down, they behave as a particle! Supercool! So, next time you're playing your guitar and rocking out to some Poison or Gwar, take a peep at your preamp tubes and those totally rad (lol get the pun? rad...) electrons in your tubes will no longer be waves, they'll be particles. And that will change the sweet sweet tone of ur amps!

What the BLEEP do YOU know!!! Or are you even "further down the rabbit hole"???

Brilliant couple of shows if you've not already seen them

V.

lol not sure what you're referencing there. But what I'm talking 'bout is shit I learned in physics class. You talking about a band or movie or tv show or something?

EDIT: Oh! I remember that shit! Film from like 2003 or something? I don't think I ever actually saw it. But maybe I'll check it out now.

 

[BeZo]

What the Bleep Do We Know is a great movie! Check it out. It turned me on to the whole quantum mechanics subject and I haven't been the same since. The brain takes in loads of information and simplifies it to create and experience. YOUR BRAIN LITERALLY CREATES YOUR EXPERIENCE! It's isn't that the world exists without your input.

"Atoms are not things. They are only tendencies." -Werner Heisenberg

Atoms are literally waves of possibility, existing in several places at the same time. But, when the mind comes to define them, they become particles to us. Now, taking into consideration that your mind literally creates the world around you, having an opinion cad cause the mind to amplify the opinion. That would be you hearing the amp sounding better, not entirely a difference in the amp.

Your headlights in your car may be brighter if you remove them from your car, but they need to be there for a reason. Taking the preamp tube covers off of your amp to get a different tone is fucking ridiculous. I have knobs on the front of my amp that can change the tone. If I want it brighter, I can turn up the highs or the presence. I have tube covers on my amp to hold the tubes in place. Getting a slightly better tone isn't entirely worth putting our tubes at risk of damage from the abuse of a gigging musician (some of us play our amps other places besides out bedrooms). And, just like tubes, the headlights in your car are housed, focused, and designed to work better for a longer period of time. They don't put tube covers on the tubes to chance the tone any more than they put halogen bulbs behind a sealed class enclosure to dim the bulb.

If there truly is a difference in the tone, there must be a reason for it. Is there a difference in signal going through the tube when the covers are off? Is there a difference in temperature with the tube covers off? What causes this difference everybody seems to hear?

 

[stephen sawall]

Hey everybody!

Did you know that electrons and photons behave differently when you observe them! Isn't that neat! When you're not looking they act as a wave. When you're staring 'em down, they behave as a particle! Supercool! So, next time you're playing your guitar and rocking out to some Poison or Gwar, take a peep at your preamp tubes and those totally rad (lol get the pun? rad...) electrons in your tubes will no longer be waves, they'll be particles. And that will change the sweet sweet tone of ur amps!

What the BLEEP do YOU know!!! Or are you even "further down the rabbit hole"???

Brilliant couple of shows if you've not already seen them

V.

lol not sure what you're referencing there. But what I'm talking 'bout is shit I learned in physics class. You talking about a band or movie or tv show or something?

EDIT: Oh! I remember that shit! Film from like 2003 or something? I don't think I ever actually saw it. But maybe I'll check it out now.

A great documentary .... I highly recommend it.

 

[moltenmetalburn]

I can easily hear a differnence when removing tube covers. Whether or not you favor the result is your preference.

I have an idea for the next thread like this one, he he he .

 

[Dale B]

I take them off, so I never would know the difference. After the springs put too much stress on the glass of a few NOS preamp tubes (or should I say ANOS?...LOL) I had, I decided to throw them all in a drawer.