Does cap voltage affect tone?

[Chuck H]

So what of this "pole" added to the "loop"? And by calling any unbypassed frequencies on the cathode bypass cap and their interaction with the decoupling cap then being pulled back through the cathode circuit via 0V a "loop", it isn't much of a stretch from there to call anything or everything a loop that has a return path of any kind, however small. I think the right consideration here is a loops significance WRT a goal. Again making this an theoretical exercise rather than a real world problem to be solved for. Otherwise...

What the hell are we going to do about that butterfly beating it's wings on the other side of the earth ultimately changing air currents and pressures that interfere with speaker excursion

[J M Fahey]

When I worked in SMPS design I had access to one of these great machines:

http://www.testequipmentdepot.com/us...zers/4194a.htm

and I used it extensively to analyze all types of caps, chokes, transformers, filter circuits and even guitar pickups (in the afterhours) for impedance response, resonances, parasitic components etc.

What you get when you plot the frequency response of the impedance of an E-cap up to high enough frequencies looks like this:

[ATTACH]49633[/ATTACH]

There is always one more or less pronounced Z-minimum around the frequency where the reactances of C and ESL (equivalent series inductance or parasitic inductance) cancel, i.e. the caps self-resonance. This frequency is typically above the audio range. The minimum value of Z corresponds to the ESR.
I have yet to see an E-cap up to 100ĩF showing any anomalies in the audio range.

Thanks for posting measured results.
And not only "a plain number" with no reference which does not mean much but a clear to understand graphic.

Which shows no surprise: capacitor impedance goes steadily down with frequency (as predicted by Physics Laws) until it reaches a minimum ... not surprisingly that minimum being ESR.

Curve is smooth, showing no self-resonant peaks whatsoever which is commendable, and achieves a minimum around 40/60kHz , WELL above Audio range.

And above that, it rises, again smoothly, until at 100 MEGA Hertz it shows same impedance as that at 60Hz .

I can live with that, in any case nobody suggested a 100uF Electrolytic is a good bypass cap at 100MHz, (easy to solve anyway with a parallel .1uF ceramic), but even more important, itīs way removed from Audio frequencies in general and doubly so Guitar ones.

As of those obsessed about Guitar speaker response at 10kHz, even worse claiming it "becomes a tweeter", I suggest a couple spoonfuls of Reality Syrup twice a day, this is an actual Guitar speaker frequency response curve (Eminence 1258):


Notice it shows a rising response up to some 2300Hz, with a strong 109dB peak there, and precisely what makes it "a Guitar speaker", and then it drops like a brick, >24dB/Octave

At 10kHz itīs down to 75dB , or **34dB below the 2300Hz response**

And what if I hit such a speaker with a dreaded squarewave?

Well, it will be strongly filtered , above 2300Hz with a >24dB/octave slope.

Thatīs why guitar amps MUST be played through Guitar speakers; Hi Fi speakers of any kind (even humble car door speakers) are buzzy unusable with them, and if distorted signal is sent to wide response systems (straight to Recording or PA mixer) they NEED to be properly filtered ... or else.

Just as an example, here we have a Marshall speaker emulator: left half is a multiple feedback circuit mainly simulating speaker resonance in a closed cab, but right side is clearly made out of two cascaded 12dB/Oct low pass filters, copying typical 24dB/Oct drop found in speakers:


Much respected H&K Cream Machine (based on their Red Box, the industry standard):

[cerrem]

Thanks for posting measured results.
And not only "a plain number" with no reference which does not mean much but a clear to understand graphic.

Which shows no surprise: capacitor impedance goes steadily down with frequency (as predicted by Physics Laws) until it reaches a minimum ... not surprisingly that minimum being ESR.

Curve is smooth, showing no self-resonant peaks whatsoever which is commendable, and achieves a minimum around 40/60kHz , WELL above Audio range.

And above that, it rises, again smoothly, until at 100 MEGA Hertz it shows same impedance as that at 60Hz .

I can live with that, in any case nobody suggested a 100uF Electrolytic is a good bypass cap at 100MHz, (easy to solve anyway with a parallel .1uF ceramic), but even more important, itīs way removed from Audio frequencies in general and doubly so Guitar ones.

As of those obsessed about Guitar speaker response at 10kHz, even worse claiming it "becomes a tweeter", I suggest a couple spoonfuls of Reality Syrup twice a day, this is an actual Guitar speaker frequency response curve (Eminence 1258):


Notice it shows a rising response up to some 2300Hz, with a strong 109dB peak there, and precisely what makes it "a Guitar speaker", and then it drops like a brick, >24dB/Octave

At 10kHz itīs down to 75dB , or **34dB below the 2300Hz response**

And what if I hit such a speaker with a dreaded squarewave?

Well, it will be strongly filtered , above 2300Hz with a >24dB/octave slope.

Thatīs why guitar amps MUST be played through Guitar speakers; Hi Fi speakers of any kind (even humble car door speakers) are buzzy unusable with them, and if distorted signal is sent to wide response systems (straight to Recording or PA mixer) they NEED to be properly filtered ... or else.

Just as an example, here we have a Marshall speaker emulator: left half is a multiple feedback circuit mainly simulating speaker resonance in a closed cab, but right side is clearly made out of two cascaded 12dB/Oct low pass filters, copying typical 24dB/Oct drop found in speakers:


Much respected H&K Cream Machine (based on their Red Box, the industry standard):

These speakers are not measured at full power....they are measured at low powers and the graphs do not represent what is really happening with a cranked amp... You need to do your own measurements instead of relying on these measurements...
When speakers are driven at loud levels....part of the voice coil extends out of the gap and thus out of the field... the voice coil does become a tweeter at frequencies above the mechanical compliance limit...
According to your school of thought..... If its a guitar amp, then use any capacitor and resistor any filter cap....non of these passive components have any parasitics that have any affect in the audio range.... Well then nothing more to discuss....I have many years of customers that come to me so their guitar amps don't sound like a generic buzzy chainsaw ...

[nosaj]

These speakers are not measured at full power....they are measured at low powers and the graphs do not represent what is really happening with a cranked amp... You need to do your own measurements instead of relying on these measurements...
When speakers are driven at loud levels....part of the voice coil extends out of the gap and thus out of the field... the voice coil does become a tweeter at frequencies above the mechanical compliance limit...
According to your school of thought..... If its a guitar amp, then use any capacitor and resistor any filter cap....non of these passive components have any parasitics that have any affect in the audio range.... Well then nothing more to discuss....I have many years of customers that come to me so their guitar amps don't sound like a generic buzzy chainsaw ...

Obviously you know nothing about Juan. Glad your customers are happy, but we're hear to learn and exchange ideas rather than 'tudes.

nosaj

[J M Fahey]

When speakers are driven at loud levels....part of the voice coil extends out of the gap and thus out of the field...

The driving force ir directly proportional to BLI (and in fact BL is specifically stated in datasheets): Magnetic Flux Density * wire length (sumerged in that Field) * current into the coil .

Suppose half the coil winding is "out of the gap" , then it still weighs as much as before but "L", is half as before because only that part inside the gap counts so now that voice coill will be slower, underdamped, sluggish.
How that can lead to faster, snappier, improved frequency response as implied by the word "Tweeter" is beyond me.

the voice coil does become a tweeter at frequencies above the mechanical compliance limit...

No , the voice coils stays a voice coil, a very poor "air pusher" because itīs just a sideways sheet of very thin material, which cuts through air without pushing it.

It needs a cone (or a light but rigid dome fixed straight to it) to have some *frontal surface* and move air.

The main cone (8/10/12/15") does not count, or works VERY poorly, (as in 35dB down at 10 kHz) precisely because itīs too heavy, at those frequencies too soft, flexing a lot, so the voice coil moves back and forth but cone canīt follow it so thereīs VERY poor coupling to air (again, remember the 35dB loss at 10kHz).

Some speakers partially offset that by gluing a small light cone straight to the VC neck.

The VC is still burdened by trying to move the main cone plus the lots of adhesive used to join them, but at least you get some "free" treble extension.

Not that much and in any case, those are not guitar speakers.

According to your school of thought..... If its a guitar amp, then use any capacitor and resistor any filter cap....non of these passive components have any parasitics that have any affect in the audio range....

I never said that.
https://en.wikipedia.org/wiki/Straw_man

[The Dude]

It's "The Imaginary Whizzer Cone Theory".

[nosaj]

It's "The Imaginary Whizzer Cone Theory".

All I hear is Strawman done to the Soundgarden "Spoon man"

nosaj

[Jazz P Bass]

The new SGM.

[Chuck H]

The new SGM.

A little more like "that other guy" (the guy that liked to argue with Merlin) in that there's some tech knowledge, though it may be misapplied. SGM had less than even my tech understanding.

[Leo_Gnardo]

Do a victory dance.

Like this?



works for me . . .

[pdf64]

I don't think you guys are being fair to cerrem, his credentials seem good http://www.merrenaudio.com/home
I was hoping to get some insight into his take on things.

These speakers are not measured at full power....they are measured at low powers and the graphs do not represent what is really happening with a cranked amp... You need to do your own measurements instead of relying on these measurements...

It would be great if you could provide the measurements that you've made; they require resource beyond that which most here have access to.
FWIW I've noticed that vintage Celestions can develop a 'tizzy' edge to their tone (which I quite like) when pushed very hard.

[J M Fahey]

Not speaking for others, I never questioned "credentials" (which never were shown by the way) , nor any "personal" qualities (which is beyond he point), but some very doubtful (to put it mildly) *Technical* statements, and constant obsession with some cool Lab equipment which is mouthwatering but designed to test "something else", way beyond our scope.
To boot it was used to apparently back some wild assertions but no actual measurements, tables or graphs were shown, just "hey, I am right because I own $4000/12000 equipment you donīt own nor can buy"

Just *one* example out of many technical errors and assumptions:

The plates will pull towards each other at full voltage and "press" the dielectric material to a smaller thickness" thus larger capacitance...

This clearly describes a *mechanical* process.

Depending on the material ....Capacitance vs Voltage Gradient across the dielectric....some cases are more dramatic than others...this is the effect that occurs

when a cap re-forms

after discharge....

Cap reforming is a *chemical* or at most **electro-chemical** effect.
Confusing both as the same shows a clear lack of understanding.

But ... but ... the credentials? ....

I havenīt seen them but thatīs not the point, I go by the raw statement itself, if somebody says "2+2=5" I couldnīt care less if heīs also a Mathematics Nobel Prize, heīs still wrong.

Or .... heīs Winston Smith after an little brainwashing.

[Enzo]

Captain Picard never broke...

[nosaj]

Captain Picard never broke...

Broke what, wind?

nosaj

[Enzo]

"There are FOUR lights."

Under torture and brainwashing, Picard never said there were five lights instead of four. Like the fingers in Orwell's 1984.