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

[tonefinger]

The spectrum analyzer may not show all the truth. We feel low fundamentals and perceive space with upper harmonics not shown on the 20 to 20k analyzer. Whatever pleases our personal hear is worth pursuing. Every piece of the chain changes the outcome. That’s why the same gear and guitar, sounds different with a different player handed from one to the other.

 

[kirk]

my freinds and i are experimenting with this subject,THROUGHLY,so far with the help of a scope ,several different sets of ears and lots of different amp so far 99.9% show no difference ,but there was one old marshall,low gain amp that actually showed a tiny tiny difference,but nobody in the room heard it ,even the guy watching the scope said he couldnt hear it ,the change was at the top of the wave and it was so small and out of audible range ,but i beleive it might have changed ever so slightly,but it was so small of a change ,say compared to just having your hand on the 1st preamp that showed up way more than a cover,we are not done yet and are recording all of this and will post the video soon when we finish with as many different amps that we can get to participate.My personal opinion has changed slightly,the covers are made of cheap tin and spring metal inside and maybe cause a tiny varience but it is so minor it is not worth leaving them off ,like they said here several times ,i have controls that can dial my amp to what i want ,removing a tube cover doesnt give me anything useable,i can get some fantastic sounds from my amps weather the covers are on or off,makes no difference my amp sounds great with the covers on,i guess guys who need to take them off have amps that dont sound so good with them on ,i said this once before,if you need to remove your tube covers to get a better sound,something is wrong ,many guys have stated it gives you more high end,more high end?half the time i dial high end out or people at the front of the stage run from the peirceing sound,i dial down the hi's alittle and people stand there all night
most guys owning marshall's bring them to me to mod out the hi-bypass cap's out of the amp or on a switch so they can have hi's when they play at low volumes,but in a live situation they ALL shut off that cap to reduce hi-end,so...why would you remove a tube cover to improve high end you just dial out?it's an oxi-moron
spring stress on a nos tube,..ok i understand that,those tubes cost alot and if your not carefull you can break a tube if not installed correctly or you have a really old tube but usually back then the glass was even better cause they didnt worry about cost as much back then and made them like tanks,but i've had a thin one before that broke just sliding it in the socket so,i dont use nos tubes too often,i do love a good 5751 once in a while though and i have never had any problem putting a cover on it

 

[Greazygeo]

my freinds and i are experimenting with this subject,THROUGHLY,so far with the help of a scope ,several different sets of ears and lots of different amp so far 99.9% show no difference ,but there was one old marshall,low gain amp that actually showed a tiny tiny difference,but nobody in the room heard it ,even the guy watching the scope said he couldnt hear it ,the change was at the top of the wave and it was so small and out of audible range ,but i beleive it might have changed ever so slightly,but it was so small of a change ,say compared to just having your hand on the 1st preamp that showed up way more than a cover,we are not done yet and are recording all of this and will post the video soon when we finish with as many different amps that we can get to participate.My personal opinion has changed slightly,the covers are made of cheap tin and spring metal inside and maybe cause a tiny varience but it is so minor it is not worth leaving them off ,like they said here several times ,i have controls that can dial my amp to what i want ,removing a tube cover doesnt give me anything useable,i can get some fantastic sounds from my amps weather the covers are on or off,makes no difference my amp sounds great with the covers on,i guess guys who need to take them off have amps that dont sound so good with them on ,i said this once before,if you need to remove your tube covers to get a better sound,something is wrong ,many guys have stated it gives you more high end,more high end?half the time i dial high end out or people at the front of the stage run from the peirceing sound,i dial down the hi's alittle and people stand there all night
most guys owning marshall's bring them to me to mod out the hi-bypass cap's out of the amp or on a switch so they can have hi's when they play at low volumes,but in a live situation they ALL shut off that cap to reduce hi-end,so...why would you remove a tube cover to improve high end you just dial out?it's an oxi-moron
spring stress on a nos tube,..ok i understand that,those tubes cost alot and if your not carefull you can break a tube if not installed correctly or you have a really old tube but usually back then the glass was even better cause they didnt worry about cost as much back then and made them like tanks,but i've had a thin one before that broke just sliding it in the socket so,i dont use nos tubes too often,i do love a good 5751 once in a while though and i have never had any problem putting a cover on it

It doesnt add or take away top end removing them on old Marshalls.....Its not about microphonics or heat.... I read about this many years ago in a Ken Fischer article and thought it was b.s....then tried with and without the "shields" many times and heard the difference.


On my amps (Marshall SL) when playing chords and listening to the high frequencies/ harmonics, they are clearer with them off. Its not that they increase or decrease the treble at all....my amps have the bright caps and the treb, mid and presence are all on ten. Volume is at least 7. My amps are not overly bright. Listen to the clip on my marshall plexi thread, you can hear how my amps sound.

Sounds like the guys you work for don't understand how to use these amps.....you know the louder the amps are, the less effect the bright caps have right? I can see not liking the 5K disc caps that the later amps have, but thats for another thread.....makes no sense to switch them off when playing loud. Do they have bright caps in the gtrs?

Higher gain amps I don't hear much change....but in the old Marshalls it's pretty easy. If you are using V30's, 65's etc, they don't have enough hi freq content to hear any change....try something like a CL80 or EV12L.

Anyway there is my inflation adjusted .02

 

[JerryP]

my freinds and i are experimenting with this subject,THROUGHLY,so far with the help of a scope ,several different sets of ears and lots of different amp so far 99.9% show no difference ,but there was one old marshall,low gain amp that actually showed a tiny tiny difference,but nobody in the room heard it ,even the guy watching the scope said he couldnt hear it ,the change was at the top of the wave and it was so small and out of audible range ,but i beleive it might have changed ever so slightly,but it was so small of a change ,say compared to just having your hand on the 1st preamp that showed up way more than a cover,we are not done yet and are recording all of this and will post the video soon when we finish with as many different amps that we can get to participate.My personal opinion has changed slightly,the covers are made of cheap tin and spring metal inside and maybe cause a tiny varience but it is so minor it is not worth leaving them off ,like they said here several times ,i have controls that can dial my amp to what i want ,removing a tube cover doesnt give me anything useable,i can get some fantastic sounds from my amps weather the covers are on or off,makes no difference my amp sounds great with the covers on,i guess guys who need to take them off have amps that dont sound so good with them on ,i said this once before,if you need to remove your tube covers to get a better sound,something is wrong ,many guys have stated it gives you more high end,more high end?half the time i dial high end out or people at the front of the stage run from the peirceing sound,i dial down the hi's alittle and people stand there all night
most guys owning marshall's bring them to me to mod out the hi-bypass cap's out of the amp or on a switch so they can have hi's when they play at low volumes,but in a live situation they ALL shut off that cap to reduce hi-end,so...why would you remove a tube cover to improve high end you just dial out?it's an oxi-moron
spring stress on a nos tube,..ok i understand that,those tubes cost alot and if your not carefull you can break a tube if not installed correctly or you have a really old tube but usually back then the glass was even better cause they didnt worry about cost as much back then and made them like tanks,but i've had a thin one before that broke just sliding it in the socket so,i dont use nos tubes too often,i do love a good 5751 once in a while though and i have never had any problem putting a cover on it

What kind of scope are you using that you think you'll see this with? What are you running thru the scope? Someone playing? A sinewave?
Any player playing live looking to dial out highs must be a young kid that doesn't understand the place a guitar holds in a song and what cutting thru the mix is all about. In my experience guys that play alone in their rooms want the big bottom and no highs because they are trying to cover the bass player parts they hear in songs. Guys that play live realize they have a bass player and they need to cut thru to be heard and stand out.
If dialing things out/in is as easy as just turning the EQ knobs or adjusting gain levels then why are you modding amps?
Jerry

 

[JerryP]

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?

Same question for you, if you have knobs that will fix it all why are you having Kirk mod your amps?
I hope you're not saying a vacuum tube and a headlight bulb are the same thing or work the same because nothing could be further from the truth.
As for what causes the change, capacitance is one of the main things. The shield doing it's job to block RF is another. The shield preventing vibration is another. How does a tuning fork work?
Jerry

 

[kirk]

so jerry ,nobody ever has brought a marshall and asked to cut the bright cap out?

 

[kirk]

and i mod amps to a customers request and because there are limitations to eqing in amps as you know ,some small cap changes can open up some amps and give a wider variety of eq'ing ,plus alot mods arent always frequency mods
you yourself have profited from a "clarity mod" that takes the hiss out of the 5150's,does that mod effect the high end?

i will list all parameters of our test when we are done,but i am using a generator and guitars but not normal playing,we have a tech that is going to set up the spectrum analysis machine next week
i build my own amps,thats all i play so when i build what sound i want...no need to mod it....kirk
any player old or young does not play with his treble on 10 unless his amp is dark to begin with you look at anyone amature to the pro's that play any fender,i'll bet the treble is turned down

 

[degenaro]

I'm with Jerry on this. And will add that when you play old JMPs the bright cap is fine as long as you crank the amp to levels it was intended to. Plus I'm no fan of molding them to begin with.
The Eq is where it needs to be on it's base tone. The fact that the controls don't do much doesn't matter since tweaking a jmp for Eq is akin to a monkey fucking a football...amusing at best.
Since it doesn't have gobs of gain the noise floor is fine as well.
And cascading stages on a Marshall makes sound like a jmp with dist plus in front. Might as well just do that or use a different amp

As for the test that was uploaded. Not sure how you can determine anything with the tone used. Plus the FFT capture is useless without knowing anything about the time domain.
Not a matter of ears being discerning but simply a matter of everything changing making a difference in tone. Now have much and whether I give shit is whole different story.

 

[wolfeman28]

Like I said, it was simply a test.

If anyone wants to keep on believing it makes a difference, there's nothing wrong with that.

Same reason why I will keep on using Mallory 150 series caps and certain brand transformers in my builds, because I think it makes a difference. As for preamp tube covers, well I'm not sold on that one

 

[kirk]

I'm with Jerry on this. And will add that when you play old JMPs the bright cap is fine as long as you crank the amp to levels it was intended to. Plus I'm no fan of molding them to begin with.
The Eq is where it needs to be on it's base tone. The fact that the controls don't do much doesn't matter since tweaking a jmp for Eq is akin to a monkey fucking a football...amusing at best.
Since it doesn't have gobs of gain the noise floor is fine as well.
And cascading stages on a Marshall makes sound like a jmp with dist plus in front. Might as well just do that or use a different amp

As for the test that was uploaded. Not sure how you can determine anything with the tone used. Plus the FFT capture is useless without knowing anything about the time domain.
Not a matter of ears being discerning but simply a matter of everything changing making a difference in tone. Now have much and whether I give shit is whole different story.

sure i agree with that,jmp's dont need modding,beside the fact i wouldnt do a mod on a classic like that even at a customers request,but jcm800,customer wants that cap cut,i'm cutting it ,and like i said all the parameters will be listed once we have gathered all information and stats,i lean away from using pedals at all ,so some older amps that i've owned didnt have the gain i was looking for at the time so some tweaks in the gain in the preamp and wow now i've got an amp that puts out,classic amps are just that classics and are popular because of the way they sound,so to mod it would de-value it,not a good idea,let alone you dont want to make a change that doesnt sound any better,but to say only an amature turns his treble down is a false statement

 

[kirk]

Like I said, it was simply a test.

If anyone wants to keep on believing it makes a difference, there's nothing wrong with that.

Same reason why I will keep on using Mallory 150 series caps and certain brand transformers in my builds, because I think it makes a difference. As for preamp tube covers, well I'm not sold on that one

this is the simply the best statement made in this arguement

 

[JerryP]

so jerry ,nobody ever has brought a marshall and asked to cut the bright cap out?

No. Most guys are more than capable of doing that themselves.
Jerry

 

[JerryP]

and i mod amps to a customers request and because there are limitations to eqing in amps as you know ,some small cap changes can open up some amps and give a wider variety of eq'ing ,plus alot mods arent always frequency mods
you yourself have profited from a "clarity mod" that takes the hiss out of the 5150's,does that mod effect the high end?

i will list all parameters of our test when we are done,but i am using a generator and guitars but not normal playing,we have a tech that is going to set up the spectrum analysis machine next week
i build my own amps,thats all i play so when i build what sound i want...no need to mod it....kirk
any player old or young does not play with his treble on 10 unless his amp is dark to begin with you look at anyone amature to the pro's that play any fender,i'll bet the treble is turned down

I assume that was your answer to my questions, but it seems like you asked more questions than you actually answered.
If you know that you are going to set up tests and do them so "THOROUGHLY", is it that hard to answer what scope you will use to capture this phenomenon?
Jerry

 

[JerryP]

One thing to consider when you're doing all these tests, much of this is about PERCEPTION. You can't measure my perception, Dave's perception, or anyone elses that says they hear it with tests in your shop. Different people have different levels of hearing perception that will not be included in any of your tests.
Another thing is different amps use different tube shields. The old amps used heavy plated steel shield, many newer amps use aluminum. Why did they make MIL spec shields? Ever looked at a Cinch IERC tube shield? What are the functions of that shield?
Jerry

 

[kirk]

You know what ,I am actually not conducting the test ,my freinds are,and I agree the idea of a different sound from an amp without tube covers can only be heard not seen,although I anxous to see the spectrum analysis but I'm not buying it its ok if you do I certainly don't want to go toe to toe with you on this matter, iwill agree the 5150's have to have the cover on its noisy without them.

 

[JerryP]

You know what ,I am actually not conducting the test ,my freinds are,and I agree the idea of a different sound from an amp without tube covers can only be heard not seen,although I anxous to see the spectrum analysis but I'm not buying it its ok if you do I certainly don't want to go toe to toe with you on this matter, iwill agree the 5150's have to have the cover on its noisy without them.

5150's don't have covers. The combo does but that has nothing to do with the noise. If you read what I copied and pasted above about the spectrum analysis you might wanna save your time and drink a few beers with those guys instead of testing.
Jerry

 

[LP Freak]

You know what ,I am actually not conducting the test ,my freinds are,and I agree the idea of a different sound from an amp without tube covers can only be heard not seen,although I anxous to see the spectrum analysis but I'm not buying it its ok if you do I certainly don't want to go toe to toe with you on this matter, iwill agree the 5150's have to have the cover on its noisy without them.

5150's don't have covers. The combo does but that has nothing to do with the noise. If you read what I copied and pasted above about the spectrum analysis you might wanna save your time and drink a few beers with those guys instead of testing.
Jerry

 

[kirk]

Yes they do a big steal plate with. Foam on it

 

[JerryP]

OK here are a couple videos I made today which are by no means meant to be scientific or prove anything other than something near a tube will change things.

In the first video I hold a scope tets probe near a preamp tube and move it closer and away from the tube to show how it picks up the sine wave and how it fades as pulled away. This is all going on outside the glass not touching any metal or part of the circuit. I'm picking up the signal in air.

The second video shows the test probes taped to the amp up against the tube glass and I move my finger on and off the tube and you can clearly see something is happening to the signal.

This does not necessarily show what's happening inside the tube, but it shows how something that might seem like nothing can affect things. That's all, no magic.

I also used a Marshall 2204 and hooked the scope up to the output and ran a clean sine wave thru the amp. At 700-800hz there was clearly shit riding on the wave of the scope and when the shield was installed the wave cleaned up with no ripple on the wave. I also noticed a slight change in the amplitude of the wave when removing the shield. Tried to video it, but it didn't pick it up with my phone.
Jerry

 

[JerryP]

Yes they do a big steal plate with. Foam on it

That's not a shield. It's a damper for vibration.
Jerry