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

[Giga]

If I can get away with it (microphonics), I prefer them off. It seems to give a "richer" tone...

As fas as I've always understood it, it has to do with the tube picking up sympathetic radiation/waves/vibration and amplifying those along with the base signal.

Didn't EVH put his amp in front of a blasting cab ?

Giga

 

[iplayloudly]

I've actually had a preamp tube work its way loose without the cover on. When it got loose enough, the HT fuse blew. Put the tube back in with the cover on, popped a new fuse in, and worked fine after that.

 

[thegame]

They're like tube condoms. Of course the playing feel is going to be more sensitive with them off.

 

[Ventura]

They're like tube condoms. Of course the playing feel is going to be more sensitive with them off.

This has got to be the best reply thus far - not only concise, but in a very weird way, sensible too.

I am cool with everything at the macro AND the micro level... As Steve_K and I were deemed IGNANT in another thread saying we have too much time if we're sitting here bantering about this issue/paradox/question (ahem!! ), I will say everything has an effect on everything. It's one massive atomic sub atomic qwarky soup!!!! BUT - whether I choose to sit here deciding on whether or not it makes a difference?? I just don't know... I'd rather be gettin' bizzy with my lady, or playing music.

Just sayin'...
V.

 

[Nigel Tufnel]

So how do metal film resistors sound then? Full but tight low end, grindy midrange, with a slightly darker top end?

More often than not like shit , actually they have their place but it's all about putting the right part in the right place. But since you seem to want me to try to put an aural description into words most metal films sound "hard" and "icy" to me. Some metal film types are fairly transparent but most impart the kind of tone I was describing. Now since I played your little game here's on that you can play if you like, I could truly care less but here ya go. Take a standard say xicon carbon film resistor and get a metal film resistor of your choice, 100k's would work fine. Place the carbon film as a grid stopper on a stage that gets smacked pretty hard, like the 3rd stage in a cascading amp. Play the amp, listen, ok great. Now pull the carbon film 100k and replace it with your metal film 100k. Play the amp, listen, and if you can't hear what I'm talking about well I'm sorry for ya. You can do the same experiment with plate load resistors as well but that grid stopper position is a place where it is very easy to hear the difference between carbon film and metal film. Now get back to me and tell me if they are "grindy" "smoothy" "darky" or whatever. Or maybe I am just as you put it, there's your water, are ya thirsty yet?

 

[JakeAC5253]

So how do metal film resistors sound then? Full but tight low end, grindy midrange, with a slightly darker top end?

More often than not like shit , actually they have their place but it's all about putting the right part in the right place. But since you seem to want me to try to put an aural description into words most metal films sound "hard" and "icy" to me. Some metal film types are fairly transparent but most impart the kind of tone I was describing. Now since I played your little game here's on that you can play if you like, I could truly care less but here ya go. Take a standard say xicon carbon film resistor and get a metal film resistor of your choice, 100k's would work fine. Place the carbon film as a grid stopper on a stage that gets smacked pretty hard, like the 3rd stage in a cascading amp. Play the amp, listen, ok great. Now pull the carbon film 100k and replace it with your metal film 100k. Play the amp, listen, and if you can't hear what I'm talking about well I'm sorry for ya. You can do the same experiment with plate load resistors as well but that grid stopper position is a place where it is very easy to hear the difference between carbon film and metal film. Now get back to me and tell me if they are "grindy" "smoothy" "darky" or whatever. Or maybe I am just as you put it, there's your water, are ya thirsty yet?

Alright Just wanted to see if you had actual reasons to back it up short of just reading it on some corksniffer 'how-to' website or something.

I've been using metal film resistors in all of my effects circuit projects, but carbon films in all of my guitar modifications. Not sure why, but for some reason I have the feeling that it works out better that way. In my mind, a guitar is more of a 'feel' sort of thing, whereas if I desire a certain value component in an effects build, I want a high quality low tolerance component that will give me that exact value and not an approximation. Perhaps I will experiment with using carbon film resistors at key points in my pedal mods and see how it tickles the ears.

 

[RoidRage]

Absolutely.

 

[stephen sawall]

"do preamp tube covers change an amps sound/tone?"

yes .... anyone with normal hearing can hear the difference...... here is a clue ~ try several different gain ranges on the amp.

 

[Jimmie]

not hard to understand and the reason you have heater filaments in your tubes to begin with - otherwise no electrons would flow and/or the electron flow would be poor until the tube was self heating itself with induced current from a source on the grid.

no guru here, but my understanding sees heater usage more for inrush limiting, causing tube resistance to decrease logarithmically as internal temperatures rise; when designed correctly, as the resistance lowers, the circuit becomes more efficient about the same point in time it stabilizes.

 

[Nigel Tufnel]

Alright Just wanted to see if you had actual reasons to back it up short of just reading it on some corksniffer 'how-to' website or something.

I've been using metal film resistors in all of my effects circuit projects, but carbon films in all of my guitar modifications. Not sure why, but for some reason I have the feeling that it works out better that way. In my mind, a guitar is more of a 'feel' sort of thing, whereas if I desire a certain value component in an effects build, I want a high quality low tolerance component that will give me that exact value and not an approximation. Perhaps I will experiment with using carbon film resistors at key points in my pedal mods and see how it tickles the ears.

No worries man, I hope I didn't come off like an ass, just being a little direct is all . I make a good chunk of my living working on amps so yes it's first hand experience for me. I honestly don't know if you could tell the difference in a pedal circuit or not but by all means give it try for yourself.

 

[Nigel Tufnel]

Tube shields increase the internal electrode capacitance of the tube by just a bit. Some of the tube data sheets will even specify to what degree.

Due to the effects of miller capacitance, this would generally effect the high frequency response, but not very much. Some say without the shields the high end breathes more.

Is there a noticeable difference maybe. Placebo is very powerful

A blind test would be more accurate. I have been able to tell a small difference in high gain applications. But from day to day playing with and without it is difficult to say.

It's certainly noticeable in a controlled environment like an otherwise quiet room that you are used to hearing. But with that said I agree with where you are going too, could I hear it in a band's mix coming out of the pa in a crowded bar? Nope, no way. Does the drunk dude 10ft over yelling free bird give a shit? Maybe next time I hear some dude who's leads aren't cutting I'll run up behind his amp and pull those tube shields for him. Us guitarists are funny, we'll chase these little details that really don't add up to a whole lot but if it makes you enjoy your rig more you'll play more and be more into it. I play with my tubes "bareback". Now if I could just find that tweak that made me want to practice non-stop.

 

[Jimmie]

Now if I could just find that tweak that made me want to practice non-stop.

its called Vyvanse...

 

[kirk]

absolutly not any capacitence difference ,"electron flow" whatever is so minor it cant be heard by the human ear,it is all voodoo ,the sheilds are there to protect the tubes and most importantly....to hold them in so they dont fall out ,..thats it ,if your amp is made so the tubes hang upside down,..leave them on,..if not take'm off ,but if your head is on top of your speakers like everyone elses i would say leave them on so you dont shake your tubes loose

 

[JerryP]

They do make a difference, more so on high gain amps.
Jerry

 

[fek]

I read Rocca's post about that years ago and tried it on my Rocca modded Mig60. I heard a difference and liked the tone better with them off. YMMV.

 

[Anonymous]

I actually heard the "hiss" change a bit when I took them off

 

[jkdsteve]

Yes.

 

[Anonymous]

I did notice the high end was a bit less grainy...Was smoother....Hmm?? Damn!!

 

[steve_k]

They're like tube condoms. Of course the playing feel is going to be more sensitive with them off.

And I thought they were just scared of the dark inside the covers....

You have a bottle with a vacuum inside.
In that vacuum are magnetic/metallic plates.
An electrical charge is introduced on the cathode.
Electrons flow from positive to negative, the anode.
Electrons flowing from the cathode to the anode create current.
Nothing to do with being covered or not.

Having said that, one might argue the point that heat is better dissipated with the covers removed. If the tube is cooling faster, it may discharge current at a more efficient rate. There is no such thing as tube "osmosis" as some people are trying to argue. With flow of electrons, a magnetic field is created. With heat, glass expands a little bit too, making the vacuum volume a little larger, then back to size. This to may bring on some inefficiencies. The fields though, attracts other nasty stuff, like RF, UHF, VHF signals. The an aluminum shield, this offers some protection against that.

Is it enough difference to tell? Probably not and I cannot tell it. If it made that much of an impact, there would be no covers used on any amp, and every amp would have a fan in it.

Steve

 

[stephen sawall]

I was discussing this subject with Andy Marshall about 10 years ago and he said something like ... Not only the tube it's self but how it reacts to the other tubes and the other components in relation to distance .... and he implied it was more than just for noise. He felt it was very important in the way it reacted to the other tubes .... that is why on the Flexi all the preamp tubes are under one cover.