Hi.

A quick general question: Does replacing electrolytic capacitors with poly
caps give better tone? (in a tube amp).

What caps would you change if you wanted better tone but didn't want to go
bankrupt with cost? (preamp caps etc?)

What do you think?


-Antti

Hi,

I can't hear the difference with classical music, let alone a guitar
head. IMO, the difference acoustically will be moot.

Physically, OTOH, poly's will kick butt on the 'lytics because:

1) they are less temprature sensitive
2) they take AC currents without damage
3) they tend to be self-healing on overload
4) the low-leakage of poly's will save tubes in the future and make for
more stable bias
5) they age better than 'lytics

--
Gregg
*It's probably useful, even if it can't be SPICE'd*
http://geek.scorpiorising.ca

Polar 'lytics generally produce harmonic and IM distortion,
depending on bias and signal voltage. Bipolar 'lytics are much
better in this respect, and polyprop foil and film are nearly
perfect. Other polys (-ester, -carbonate, -etc), and metalised
films of same materials, range between bipolar 'lytics and polyprop.

Quality of construction is possibly a more important consideration.
Distortion can arise from manufacturing defects, or where caps have
been produced for a purpose where distortion is not an issue.

Only polar 'lytics show distortion that is likely to be above the
noise level of a guitar amp, and even that is likely to be
negligible. Alternatives are physically much larger, of course.
But most types are more reliable than 'lytics.

cheers, Ian

"Antti" wrote in message
...
Hi.

A quick general question: Does replacing electrolytic capacitors
with poly
caps give better tone? (in a tube amp).

What caps would you change if you wanted better tone but didn't
want to go
bankrupt with cost? (preamp caps etc?)

What do you think?


-Antti

What caps would you change if you wanted better tone but didn't want to go
bankrupt with cost?

Hi RATs!

Retail caps are priced by the uF.

Start with the little caps, and work your way up

Happy Ears!

Al


Alan J. Marcy
Phoenix, AZ

PWC/mystic/Earhead

Also consider bypassing electrolytics with good (low esr) polyprops
of 100th value (traditionally). Efficacy will depend on quality of
the 'lytics, which is generally better than it used to be. Would be
cheap to experiment with just one of perhaps 1uF across each 'lytic
in turn to see if you hear a difference.

cheers, Ian

"TubeGarden" wrote in message
...
What caps would you change if you wanted better tone but didn't
want to go
bankrupt with cost?

Hi RATs!

Retail caps are priced by the uF.

Start with the little caps, and work your way up

Happy Ears!

Al


Alan J. Marcy
Phoenix, AZ

PWC/mystic/Earhead

Gregg wrote:

Hi,

I can't hear the difference with classical music, let alone a guitar
head. IMO, the difference acoustically will be moot.

Indeed this is the case, especially with class A PP amps,
which have inherent common mode rejection of PS noise,
but only while they work in class A.



Physically, OTOH, poly's will kick butt on the 'lytics because:

1) they are less temprature sensitive

True, but who is gonna allow the elcaps to go to 105C?


2) they take AC currents without damage

Operating well within ratings, elcaps are fine,
and millions of SMPS where the mains is just rectified
and then the DC is chopped, means the elcaps are FAR better
than they used to be 40 years ago, where they got a poor reputation.
Its far cheaper and more effective to use a large value elcap.
try 470 uF poly cap, its HUGE, and impractical, so values are
limited to less than 100 uF in tube amp PS, and still the cap is huge,
and a very high value inductor has to be used.


3) they tend to be self-healing on overload

Yes, they are good there, arcs tend to heal.
but the higher the V rating, the bigger the cap.


4) the low-leakage of poly's will save tubes in the future and make for
more stable bias

The same could be said of elcaps.
Todays have leakage quite low enough.
Especially in low current bias circuits where they will last
an enormously long time, if set up to run with 1/2 to 2/3 of their
wkg DV.


5) they age better than 'lytics

Maybe they do, but todays elcaps seem to last heck of a time.
Active detectors of over currents in cathode circuits which switch off the
amp,
or the B+ will prevent excess PS current draw in a fault.
Operating elcaps above their ripple current ability does strain the hell
out of elcaps,
and is what is mainly the reason
for their over heating and death, since higher than normal DC causes
higher than normal AC, or ripple current, beyond their rating.
So design for 100% overload of B+ current, and add active over current
protection, and the elcaps will last, and the costs will be far lower than
the same uF used in poly caps.



I have had many old radios from 1950 with all the electros still working
OK.

Replacing them is dirt cheap, and effective, and poly caps
or paper in oil makes precious little difference to the sound, if anything.

In SE designs, low ripple of perhaps 5 mV at the input to the OPT
is what should be aimed for, along with a super low impedance
B+ supply, even at 10 Hz, and one which is non resonant above 7 Hz.
So if you have only 100 uF cap to anchor the OPT B+, then its impedance
at 10 Hz is 160 ohms, and the preceeding choke needs to be 5H,
to get Fo = 7 Hz.
The 100 Hz ripple reduction factor of 5H + 100 uF is only 16/3140, or .025,

so if the C1 in a CLC PS is 100 uF, and DC = 0.2 amps,
initial ripple at C1 = 4.4 rms, and at C2 = 110 mV, which is 10 times
higher
than what I think is needed for an SE hi-fi amp.
So the use of 470 uF elcaps, even in series, say 2 x 350v rated with a 500
v supply
and the SAME sized choke, and silicon rectifiers will give a final
filter of 235 uF, 5H, 235 uF, and giving ripple voltage of 4 mV at the C2.
To be sure about bypassing really high RF, use a 0.47 uF polypropylene
at 630v rating across C1 and C2.
The Fo of the LC2 filter after C1 will be 5 Hz.

Most SMPS elcaps are rated to work OK as real capacitors at least to
100 kHz, and then the ESR and series L starts to increase, but
at 100 kHz, 0.47 uF has become 3.3 ohms, with declining Z
at 6 dB/octave above this F.

But most tube amps work fine without the additional poly cap
for RF bypassing, because the stray Cshunt of the OPT bypasses any RF,
and the leakage inductance and stray C act as a filter to prevent
RF transmission through the OPT.

For caps apart from the PS, use whatever turns you on,
and I hear ppl say Auricaps, or teflon types, or paper in oils are OK,
but paper + foil in beeswax appeals as well, but the jury can't come to a
verdict
on what sounds the best.

Maybe its all good sounding, just different goodness.

Figures for ripple quoted are for 50 Hz mains, full wave rectifiers.

Patrick Turner.


--
Gregg
*It's probably useful, even if it can't be SPICE'd*
http://geek.scorpiorising.ca

Hi RATs!

Guitarzan!

Set up your amp to allow switching between caps.

Figure out how to make sure the amp is in standby when you switch

Nothing beats excess

Happy Ears!
Al


Alan J. Marcy
Phoenix, AZ

PWC/mystic/Earhead

Patrick Turner wrote:

[...]


3) they tend to be self-healing on overload


Yes, they are good there, arcs tend to heal.
[...]

In all fairness, elcaps have a self-healing characteristic also. In
fact, it's more of a "true" self-healing than mylar, which is merely
"self clearing." The dielectric is aluminum (aluminium) oxide, when it's
punched through the capacitor draws current, forming oxygen gas by
electrolysis, which repairs the oxide layer.

Cheers,
Fred
--
+--------------------------------------------+
| Music: http://www3.telus.net/dogstarmusic/ |
| Projects, Vacuum Tubes & other stuff: |
| http://www.dogstar.dantimax.dk |
+--------------------------------------------+

"Fred Nachbaur" wrote in message
news:CIjbb.10$0a6.7@edtnps84...


Patrick Turner wrote:

[...]


3) they tend to be self-healing on overload


Yes, they are good there, arcs tend to heal.
[...]

In all fairness, elcaps have a self-healing characteristic also. In
fact, it's more of a "true" self-healing than mylar, which is merely
"self clearing." The dielectric is aluminum (aluminium) oxide, when it's
punched through the capacitor draws current, forming oxygen gas by
electrolysis, which repairs the oxide layer.


PEDANTIC BUT UNSURE MODE Isn't it sumething other than oxide, like
dioxide, carbonate, sulfide, something weird? Is oxigen even involved? And
yes, I've skipped all of my Chem classes.../PEDANTIC
-dim
Cheers,
Fred
--
+--------------------------------------------+
| Music: http://www3.telus.net/dogstarmusic/ |
| Projects, Vacuum Tubes & other stuff: |
| http://www.dogstar.dantimax.dk |
+--------------------------------------------+

"Shiva" wrote in message
...

"Fred Nachbaur" wrote in message
news:CIjbb.10$0a6.7@edtnps84...


Patrick Turner wrote:

[...]


3) they tend to be self-healing on overload


Yes, they are good there, arcs tend to heal.
[...]

In all fairness, elcaps have a self-healing characteristic also. In
fact, it's more of a "true" self-healing than mylar, which is merely
"self clearing." The dielectric is aluminum (aluminium) oxide, when it's
punched through the capacitor draws current, forming oxygen gas by
electrolysis, which repairs the oxide layer.


PEDANTIC BUT UNSURE MODE Isn't it sumething other than oxide, like
dioxide, carbonate, sulfide, something weird? Is oxigen even involved?
And
yes, I've skipped all of my Chem classes.../PEDANTIC
-dim

The electrolysis experiments I did as a kid, produced oxygen and hydrogen. I
had a great time filling big plastic bottles with this stuf and igniting it
around school.....

Karsten

Cheers,
Fred
--
+--------------------------------------------+
| Music: http://www3.telus.net/dogstarmusic/ |
| Projects, Vacuum Tubes & other stuff: |
| http://www.dogstar.dantimax.dk |
+--------------------------------------------+

"Shiva" schreef in bericht
...

"Fred Nachbaur" wrote in message
news:CIjbb.10$0a6.7@edtnps84...


Patrick Turner wrote:

[...]


3) they tend to be self-healing on overload


Yes, they are good there, arcs tend to heal.
[...]

In all fairness, elcaps have a self-healing characteristic also. In
fact, it's more of a "true" self-healing than mylar, which is merely
"self clearing." The dielectric is aluminum (aluminium) oxide, when it's
punched through the capacitor draws current, forming oxygen gas by
electrolysis, which repairs the oxide layer.


PEDANTIC BUT UNSURE MODE Isn't it sumething other than oxide, like
dioxide, carbonate, sulfide, something weird? Is oxigen even involved?
And
yes, I've skipped all of my Chem classes.../PEDANTIC
-dim

Sorry Shiva,

It is aluminium oxide (di-aluminium tri-oxide (Al2O3) in fact or everyday
normal aluminium oxide). The aluminiumoxide is under normal conditions
always as a coating on aluminium metal in a gas sealing layer, this keeps
oxygen out and preventing the metal from burning in the air (with a very,
very bright flame) or reacting with water.
The metal is so reactive with oxygen that any scratch of the surface, is
immediatly covered with brand new aluminium oxide. This prevents the metal
form further oxidizing. The oxide will easily react with strong acids or
basic agents in which the product of this reaction is solvable (is this
proper English?)

For example: DON'T put some aluminium foil in a caustic soda solution, the
aluminiumoxide will react with the caustic soda and leaving the under laying
metal bare, this wil react with the water in the solution to form aluminium
oxide and hydrogen, again the aluminium oxide will react with the caustic
soda, leaving the metal bare, causing it to react with water, and so on.
(don't try this at home folks, it is a vivid reaction).

Only a few aluminium compounds are not solvable in water, the others are
solvable in water or will decompose in water.
Before the making of an elcap, the stripes of aluminium are etched to
obtaine a large surface. This is done in a water based proces. In this
proces (due to the water enviroment) the surface is covered with aluminium
oxide.
So the insulator is aluminium oxide. Maybe, and just maybe, some parts of
the electrolyte can be formed in the oxide layer during the forming proces
of the (almost ready) elcap.

With regards,
Simon

yes, I didn't skip my chem classes :-)

Cheers,
Fred
--
+--------------------------------------------+
| Music: http://www3.telus.net/dogstarmusic/ |
| Projects, Vacuum Tubes & other stuff: |
| http://www.dogstar.dantimax.dk |
+--------------------------------------------+

"All Ears" schreef in bericht
k...

"Shiva" wrote in message
...

"Fred Nachbaur" wrote in message
news:CIjbb.10$0a6.7@edtnps84...


Patrick Turner wrote:

[...]


3) they tend to be self-healing on overload


Yes, they are good there, arcs tend to heal.
[...]

In all fairness, elcaps have a self-healing characteristic also. In
fact, it's more of a "true" self-healing than mylar, which is merely
"self clearing." The dielectric is aluminum (aluminium) oxide, when
it's
punched through the capacitor draws current, forming oxygen gas by
electrolysis, which repairs the oxide layer.


PEDANTIC BUT UNSURE MODE Isn't it sumething other than oxide, like
dioxide, carbonate, sulfide, something weird? Is oxigen even involved?
And
yes, I've skipped all of my Chem classes.../PEDANTIC
-dim

The electrolysis experiments I did as a kid, produced oxygen and hydrogen.
I
had a great time filling big plastic bottles with this stuf and igniting
it
around school.....

Karsten


Yes, I did that to. Only with small plastic bags (I wasn't that patient to
fill something larger).

With regards,

Simon

Cheers,
Fred
--
+--------------------------------------------+
| Music: http://www3.telus.net/dogstarmusic/ |
| Projects, Vacuum Tubes & other stuff: |
| http://www.dogstar.dantimax.dk |
+--------------------------------------------+

Fred Nachbaur wrote:

Patrick Turner wrote:

[...]


3) they tend to be self-healing on overload


Yes, they are good there, arcs tend to heal.
[...]

In all fairness, elcaps have a self-healing characteristic also. In
fact, it's more of a "true" self-healing than mylar, which is merely
"self clearing." The dielectric is aluminum (aluminium) oxide, when it's
punched through the capacitor draws current, forming oxygen gas by
electrolysis, which repairs the oxide layer.

Yes sometimes if used at over the rated voltage, the elcap will
short, click, click, and then a hard short,
and then its stuffed.
But if caught before the hard short, and correct voltage applied,
maybe its OK again.
But I cannot remember when I got a dud, ie, an elcap which
went short while being operated properly.
They don't like being connected reverse polarity,
but ppl know that. But again they recover after that and usually go OK,
when polarity is right.

Patrick Turner.



Cheers,
Fred
--
+--------------------------------------------+
| Music: http://www3.telus.net/dogstarmusic/ |
| Projects, Vacuum Tubes & other stuff: |
| http://www.dogstar.dantimax.dk |
+--------------------------------------------+

Simon wrote:

"Shiva" schreef in bericht
...

"Fred Nachbaur" wrote in message
news:CIjbb.10$0a6.7@edtnps84...


Patrick Turner wrote:

[...]


3) they tend to be self-healing on overload


Yes, they are good there, arcs tend to heal.
[...]

In all fairness, elcaps have a self-healing characteristic also. In
fact, it's more of a "true" self-healing than mylar, which is merely
"self clearing." The dielectric is aluminum (aluminium) oxide, when it's
punched through the capacitor draws current, forming oxygen gas by
electrolysis, which repairs the oxide layer.


PEDANTIC BUT UNSURE MODE Isn't it sumething other than oxide, like
dioxide, carbonate, sulfide, something weird? Is oxigen even involved?
And
yes, I've skipped all of my Chem classes.../PEDANTIC
-dim

Sorry Shiva,

It is aluminium oxide (di-aluminium tri-oxide (Al2O3) in fact or everyday
normal aluminium oxide). The aluminiumoxide is under normal conditions
always as a coating on aluminium metal in a gas sealing layer, this keeps
oxygen out and preventing the metal from burning in the air (with a very,
very bright flame) or reacting with water.
The metal is so reactive with oxygen that any scratch of the surface, is
immediatly covered with brand new aluminium oxide. This prevents the metal
form further oxidizing. The oxide will easily react with strong acids or
basic agents in which the product of this reaction is solvable (is this
proper English?)

The beauty of Al oxide is that you can polish Al up to a fine finish, and it
looks
nice and shiny, and metallic, but the very thin layer of oxide which
immeditately forms
protects further tarnishing for a long time, unles the atmosphere is damp,
and other pollutants like salt air are a factor.

There is more info about anodizing at

http://www.engineeringtalk.com/news/mig/mig101.html



For example: DON'T put some aluminium foil in a caustic soda solution, the
aluminiumoxide will react with the caustic soda and leaving the under laying
metal bare, this wil react with the water in the solution to form aluminium
oxide and hydrogen, again the aluminium oxide will react with the caustic
soda, leaving the metal bare, causing it to react with water, and so on.
(don't try this at home folks, it is a vivid reaction).

?? but they use custic soda in the anodizing process?


Only a few aluminium compounds are not solvable in water, the others are
solvable in water or will decompose in water.

After anodizing, Al is extremely well protected against water,
and the surface is hardened, and proofed against ppl with acid
sweat, and resistant to most solvents for cleaning.

a poor man's anodizing can be done by polishing the Al, then
dunking in caustic soda NaOH, and it turns grey, but this surface is fragile,
and needs to be air dried and sealed with polyurethane.
I have never bothered doing this.

The anodizer I know shot peens the article with fine glass beads,
then he cleans the article to be anodized, then rinses in H2O,
then places it in the H2SO4 bath for anodizing, and its not something
I have been tempted to try at home.


Before the making of an elcap, the stripes of aluminium are etched to
obtaine a large surface. This is done in a water based proces. In this
proces (due to the water enviroment) the surface is covered with aluminium
oxide.
So the insulator is aluminium oxide. Maybe, and just maybe, some parts of
the electrolyte can be formed in the oxide layer during the forming proces
of the (almost ready) elcap.

With regards,
Simon

The elcaps are like a battery....

Patrick Turner.



yes, I didn't skip my chem classes :-)

Cheers,
Fred
--
+--------------------------------------------+
| Music: http://www3.telus.net/dogstarmusic/ |
| Projects, Vacuum Tubes & other stuff: |
| http://www.dogstar.dantimax.dk |
+--------------------------------------------+

Patrick Turner wrote:
Yes sometimes if used at over the rated voltage, the elcap will
short, click, click, and then a hard short,
and then its stuffed.

Hehe, made a mistake once, two 470/63 got some over 100 volts.

While listening, the amp first started to sizzle like some meat
in a frying pan. When it got to me that there's something wrong,
the whole room was a stink... Phew...

Later I found a small puddle of goo below one of the caps.
Yuk! My, these things where hot. Luckily, only one cap
burst open.

That smell will make me be more careful next time... :-)

Did I say Yuk?

--
Olav Wölfelschneider

"Simon" wrote in message
...

"Shiva" schreef in bericht
...

"Fred Nachbaur" wrote in message
news:CIjbb.10$0a6.7@edtnps84...


Patrick Turner wrote:

[...]


3) they tend to be self-healing on overload


Yes, they are good there, arcs tend to heal.
[...]

In all fairness, elcaps have a self-healing characteristic also. In
fact, it's more of a "true" self-healing than mylar, which is merely
"self clearing." The dielectric is aluminum (aluminium) oxide, when
it's
punched through the capacitor draws current, forming oxygen gas by
electrolysis, which repairs the oxide layer.


PEDANTIC BUT UNSURE MODE Isn't it sumething other than oxide, like
dioxide, carbonate, sulfide, something weird? Is oxigen even involved?
And
yes, I've skipped all of my Chem classes.../PEDANTIC
-dim

Sorry Shiva,

It is aluminium oxide (di-aluminium tri-oxide (Al2O3) in fact or everyday
normal aluminium oxide). The aluminiumoxide is under normal conditions
always as a coating on aluminium metal in a gas sealing layer, this keeps
oxygen out and preventing the metal from burning in the air (with a very,
very bright flame) or reacting with water.

The metal is so reactive with oxygen that any scratch of the surface, is
immediatly covered with brand new aluminium oxide. This prevents the metal
form further oxidizing. The oxide will easily react with strong acids or
basic agents in which the product of this reaction is solvable (is this
proper English?)

Hi Simon -
Thought it was something a bit different, like anodizing, and that's how the
'lytics were formed - I know that the anodized layer is a pretty good
dielectric, but perhaps it's some form of oxide too (i always thought that
there were a bunch of different ways for stuff to react with oxigen, like
carbon monoxide & carbon di-oxide), so perjaps it's not too OT for me to ask
a couple of things:
1. I know aluminum is self-sealing to an extent, but doesn't what you say
imply that the oxide film can't possibly be more than a molecule thick? One
the outer layer of molecules reacts with oxigen, shouldn't the process
*stop*? (BTW, as another non-native speaker, I think the word you're looking
for is "soluable", as in "able to disolve", OTOH "dissolve& form a solution"
would imply "solvable", but that's generally used in the context of "This
problem is solvable". You get th gist.)
2. I know the whhitish flaky stuff on aluminum is commonly called "aluminum
oxide", but is it? Or is it more along the lines of aluminum salts? (forgive
me if that's a really dumb question - last appology).
3. what is used as an electrolyte in 'lytics? It seems that it has to be
al things to all people - it has to have great wetting. to get into the
scribed areas n the foil, really low R (faster cap /less heat), shouldn't
leave a bunch of reactive gasses around, should be thermaly stable, and
shouldn't react with the (Al2O3?) when the voltage's off the cap... Seems
like a tall order - i wonder what they use? Perhaps I should have payed
attention in chem. Are you sure the dielectric is actually Al2O3, and not
something more stable? (been around too many aluminum boats...)

For example: DON'T put some aluminium foil in a caustic soda solution, the
aluminiumoxide will react with the caustic soda and leaving the under
laying
metal bare, this wil react with the water in the solution to form
aluminium
oxide and hydrogen, again the aluminium oxide will react with the caustic
soda, leaving the metal bare, causing it to react with water, and so on.
(don't try this at home folks, it is a vivid reaction).


Hey, we've got Crystal Drano here - I use it to clean & strip anodizing off
aluminum. The first time i tried it was on a small heatsink in a plastic
cup. Luckily, i left the cup in the sink - instant meltdown...



a water based proces. In this
proces (due to the water enviroment) the surface is covered with aluminium
oxide.
So the insulator is aluminium oxide. Maybe, and just maybe, some parts of
the electrolyte can be formed in the oxide layer during the forming proces
of the (almost ready) elcap.

With regards,
Simon

yes, I didn't skip my chem classes :-)


Simon, where you the one who built tat homebrew amp which had, what I
thought was, cast end pieces, and ( i think it was you...) hunted for an
english word to describe the material, which you said was like dense
partical board? /runon If it was you, it's not your knowledge of english
which failed you - we simply don't have this stuff around here. An
architect friend of mine showed me some samples - both from german
companies. Neat stuff - i've got the datasheets on it somwhere... thhe
only problem (at least with this stuff) is it's lack of tortional strength -
if you bend or twist it, it breaks like particle board.
-dim

"All Ears" wrote in message
k...

"Shiva" wrote in message
...

"Fred Nachbaur" wrote in message
news:CIjbb.10$0a6.7@edtnps84...


Patrick Turner wrote:

[...]


3) they tend to be self-healing on overload


Yes, they are good there, arcs tend to heal.
[...]

In all fairness, elcaps have a self-healing characteristic also. In
fact, it's more of a "true" self-healing than mylar, which is merely
"self clearing." The dielectric is aluminum (aluminium) oxide, when
it's
punched through the capacitor draws current, forming oxygen gas by
electrolysis, which repairs the oxide layer.


PEDANTIC BUT UNSURE MODE Isn't it sumething other than oxide, like
dioxide, carbonate, sulfide, something weird? Is oxigen even involved?
And
yes, I've skipped all of my Chem classes.../PEDANTIC
-dim

The electrolysis experiments I did as a kid, produced oxygen and hydrogen.
I
had a great time filling big plastic bottles with this stuf and igniting
it
around school.....

Karsten


Oh, childhood memories... I remember sneaking onto construction sites with,
essentially, large garbage bags, and filling them up with acetylene /map /
whatever & oxygen from the welding tanks. A few kiddy helium balloons & a
chunk of model fuse...

Cheers,
Fred
--
+--------------------------------------------+
| Music: http://www3.telus.net/dogstarmusic/ |
| Projects, Vacuum Tubes & other stuff: |
| http://www.dogstar.dantimax.dk |
+--------------------------------------------+

"Shiva" schreef in bericht
...

"Simon" wrote in message
...

"Shiva" schreef in bericht
...

"Fred Nachbaur" wrote in message
news:CIjbb.10$0a6.7@edtnps84...


Patrick Turner wrote:

[...]


3) they tend to be self-healing on overload


Yes, they are good there, arcs tend to heal.
[...]

In all fairness, elcaps have a self-healing characteristic also. In
fact, it's more of a "true" self-healing than mylar, which is merely
"self clearing." The dielectric is aluminum (aluminium) oxide, when
it's
punched through the capacitor draws current, forming oxygen gas by
electrolysis, which repairs the oxide layer.


PEDANTIC BUT UNSURE MODE Isn't it sumething other than oxide, like
dioxide, carbonate, sulfide, something weird? Is oxigen even
involved?
And
yes, I've skipped all of my Chem classes.../PEDANTIC
-dim

Sorry Shiva,

It is aluminium oxide (di-aluminium tri-oxide (Al2O3) in fact or
everyday
normal aluminium oxide). The aluminiumoxide is under normal conditions
always as a coating on aluminium metal in a gas sealing layer, this
keeps
oxygen out and preventing the metal from burning in the air (with a
very,
very bright flame) or reacting with water.

The metal is so reactive with oxygen that any scratch of the surface, is
immediatly covered with brand new aluminium oxide. This prevents the
metal
form further oxidizing. The oxide will easily react with strong acids or
basic agents in which the product of this reaction is solvable (is this
proper English?)

Hi Simon -
Thought it was something a bit different, like anodizing, and that's how
the
'lytics were formed - I know that the anodized layer is a pretty good
dielectric, but perhaps it's some form of oxide too (i always thought that
there were a bunch of different ways for stuff to react with oxigen, like
carbon monoxide & carbon di-oxide), so perjaps it's not too OT for me to
ask
a couple of things:
1. I know aluminum is self-sealing to an extent, but doesn't what you say
imply that the oxide film can't possibly be more than a molecule thick?
One
the outer layer of molecules reacts with oxigen, shouldn't the process
*stop*? (BTW, as another non-native speaker, I think the word you're
looking
for is "soluable", as in "able to disolve", OTOH "dissolve& form a
solution"
would imply "solvable", but that's generally used in the context of "This
problem is solvable". You get th gist.)

Owh lot's of questions, it is ten years ago since I'd my last chem classes,
but I'll give it a shot.
Yes, you're right. Theoretical should one layer be enough, although
technically there are no alumiumoxide molecules. It is a salt and consist of
positivly Aluminium ions and negativ charged oxygen atoms.
It al depends of the water enviroment, if the water is acid the aluminium
oxide (Al2O3) reacts:
6H+ + Al2O3 = 2 Al3+ + 3 H2O
in this enviroment the Al2O3 will solute like a sugar lump.
because of the disappearence of the protective Al2O3 the metal will react
with water
2 Al + 3 H2O = Al2O3 + 3 H2
so this will go on until all the H+ (acid) is used.

if the water is pH neutral Al2O3 will not solute.

if the water is basic (OH- ) the following will take place
Al2O3 + 6 OH- = 2 (AlO3)3- + 3 H2O (The (AlO3)3- is soluable in
this enviroment)
because of the disappearence of the protective Al2O3 the metal will react
with water
2 Al + 3 H2O = Al2O3 + 3 H2
so this will go on until all the (OH- ) (basic) is used.

2. I know the whhitish flaky stuff on aluminum is commonly called
"aluminum
oxide", but is it? Or is it more along the lines of aluminum salts?
(forgive
me if that's a really dumb question - last appology).

Hey lot's of salts are whitish crystaline flakes ;-) and Al2O3 is a salt. So
good question. It could be Al2O3 but also something else (depending of the
enviroment) like Al(OH)3 (Aluminium hydroxide)

3. what is used as an electrolyte in 'lytics? It seems that it has to be
al things to all people - it has to have great wetting. to get into the
scribed areas n the foil, really low R (faster cap /less heat), shouldn't
leave a bunch of reactive gasses around, should be thermaly stable, and
shouldn't react with the (Al2O3?) when the voltage's off the cap... Seems
like a tall order - i wonder what they use? Perhaps I should have payed
attention in chem. Are you sure the dielectric is actually Al2O3, and not
something more stable? (been around too many aluminum boats...)

Ah, the electrolyt, a precious secret in the making of the elcap. In the use
of a elcap there should be no chemical reaction. It is a capacitor like this

aluminium | aluminium oxide | electrolytic fluid | aluminium oxide
|aluminium
--------| |-----------------------------------------|
|------------

because of the very thin layer of the non conductin aluminium oxide and the
enormouse surface of the foil (it is etched to get an even greater surface)
it can hold a hugh charge

The used electrolyt should be pH neutral and be a good conductor. I know
that in some elcaps picric acid or boric acid is used in combination with
other substances.
I heard that a good Elcap should have some leak current, this keeps the
layer Al2O3 on a certain thickness. If an elcap is not used for a long time
the Al2O3 slowly get's thinner.

BTW
Aluminium is also used as a kind of sacrifice for protecting Iron boats.
Salty water is a good electrolyte and aluminium is a very non precious
metal. So a combinations of Iron, salty water and aluminium will act as a
sort of battery. This wil protect the iron from rusting.


For example: DON'T put some aluminium foil in a caustic soda solution,
the
aluminiumoxide will react with the caustic soda and leaving the under
laying
metal bare, this wil react with the water in the solution to form
aluminium
oxide and hydrogen, again the aluminium oxide will react with the
caustic
soda, leaving the metal bare, causing it to react with water, and so on.
(don't try this at home folks, it is a vivid reaction).


Hey, we've got Crystal Drano here - I use it to clean & strip anodizing
off
aluminum. The first time i tried it was on a small heatsink in a plastic
cup. Luckily, i left the cup in the sink - instant meltdown...

LOL


a water based proces. In this
proces (due to the water enviroment) the surface is covered with
aluminium
oxide.
So the insulator is aluminium oxide. Maybe, and just maybe, some parts
of
the electrolyte can be formed in the oxide layer during the forming
proces
of the (almost ready) elcap.

With regards,
Simon

yes, I didn't skip my chem classes :-)


Simon, where you the one who built tat homebrew amp which had, what I
thought was, cast end pieces, and ( i think it was you...) hunted for an
english word to describe the material, which you said was like dense
partical board? /runon If it was you, it's not your knowledge of english
which failed you - we simply don't have this stuff around here. An
architect friend of mine showed me some samples - both from german
companies. Neat stuff - i've got the datasheets on it somwhere... thhe
only problem (at least with this stuff) is it's lack of tortional
strength -
if you bend or twist it, it breaks like particle board.
-dim

No that wasn't me, but I remember the post.
At the moment I'm working on a homebrew tube tester, but I've got so little
time to work on it (I got a brand new son, he is 11 weeks old at the moment
and needs all the attention)

Regards,

Simon

"Patrick Turner" schreef in bericht
...


Simon wrote:

"Shiva" schreef in bericht
...

"Fred Nachbaur" wrote in message
news:CIjbb.10$0a6.7@edtnps84...


Patrick Turner wrote:

[...]


3) they tend to be self-healing on overload


Yes, they are good there, arcs tend to heal.
[...]

In all fairness, elcaps have a self-healing characteristic also. In
fact, it's more of a "true" self-healing than mylar, which is merely
"self clearing." The dielectric is aluminum (aluminium) oxide, when
it's
punched through the capacitor draws current, forming oxygen gas by
electrolysis, which repairs the oxide layer.


PEDANTIC BUT UNSURE MODE Isn't it sumething other than oxide, like
dioxide, carbonate, sulfide, something weird? Is oxigen even
involved?
And
yes, I've skipped all of my Chem classes.../PEDANTIC
-dim

Sorry Shiva,

It is aluminium oxide (di-aluminium tri-oxide (Al2O3) in fact or
everyday
normal aluminium oxide). The aluminiumoxide is under normal conditions
always as a coating on aluminium metal in a gas sealing layer, this
keeps
oxygen out and preventing the metal from burning in the air (with a
very,
very bright flame) or reacting with water.
The metal is so reactive with oxygen that any scratch of the surface, is
immediatly covered with brand new aluminium oxide. This prevents the
metal
form further oxidizing. The oxide will easily react with strong acids or
basic agents in which the product of this reaction is solvable (is this
proper English?)

The beauty of Al oxide is that you can polish Al up to a fine finish, and
it
looks
nice and shiny, and metallic, but the very thin layer of oxide which
immeditately forms
protects further tarnishing for a long time, unles the atmosphere is damp,
and other pollutants like salt air are a factor.

There is more info about anodizing at

http://www.engineeringtalk.com/news/mig/mig101.html



For example: DON'T put some aluminium foil in a caustic soda solution,
the
aluminiumoxide will react with the caustic soda and leaving the under
laying
metal bare, this wil react with the water in the solution to form
aluminium
oxide and hydrogen, again the aluminium oxide will react with the
caustic
soda, leaving the metal bare, causing it to react with water, and so on.
(don't try this at home folks, it is a vivid reaction).

?? but they use custic soda in the anodizing process?

My guess is that is not a very concentrated solution, and that the caustic
soda is used as an electrolyte.



Only a few aluminium compounds are not solvable in water, the others are
solvable in water or will decompose in water.

After anodizing, Al is extremely well protected against water,
and the surface is hardened, and proofed against ppl with acid
sweat, and resistant to most solvents for cleaning.

a poor man's anodizing can be done by polishing the Al, then
dunking in caustic soda NaOH, and it turns grey, but this surface is
fragile,
and needs to be air dried and sealed with polyurethane.
I have never bothered doing this.

The anodizer I know shot peens the article with fine glass beads,
then he cleans the article to be anodized, then rinses in H2O,
then places it in the H2SO4 bath for anodizing, and its not something
I have been tempted to try at home.

I'm planning to use an aluminium frame for a next amp and I must say the
idea of anodizing the frame has crossed my mind.
But then again painting is much easier, I guess.

With regards,

Simon


Before the making of an elcap, the stripes of aluminium are etched to
obtaine a large surface. This is done in a water based proces. In this
proces (due to the water enviroment) the surface is covered with
aluminium
oxide.
So the insulator is aluminium oxide. Maybe, and just maybe, some parts
of
the electrolyte can be formed in the oxide layer during the forming
proces
of the (almost ready) elcap.

With regards,
Simon

The elcaps are like a battery....

Patrick Turner.



yes, I didn't skip my chem classes :-)

Cheers,
Fred
--
+--------------------------------------------+
| Music: http://www3.telus.net/dogstarmusic/ |
| Projects, Vacuum Tubes & other stuff: |
| http://www.dogstar.dantimax.dk |
+--------------------------------------------+

I'm planning to use an aluminium frame for a next amp and I must
say the
idea of anodizing the frame has crossed my mind.
But then again painting is much easier, I guess.

Be careful to use the right paint. Very few stick for long. That's
why anodising was used so much in the first place.

cheers, Ian

"Ian Iveson" wrote in message
news
I'm planning to use an aluminium frame for a next amp and I must
say the
idea of anodizing the frame has crossed my mind.
But then again painting is much easier, I guess.

Be careful to use the right paint. Very few stick for long. That's
why anodising was used so much in the first place.

cheers, Ian


Hi Ian -
Around a year back there was a post by a RAT who worked for Alcoa about
aluminum treatment methods & products. Have it saved *somwhere*... worth
looking up.
What works for me is simply washing the stuff with laquer thinner to get
rid of the oils, dipping it in a drano bath, then lots of hot water, and
using an etching primer. I've also backed on wrinkle-black on aluminum, and
it was durable. Motorcycle stores also used to have a product called "case
paint", which, when backed on, was amazingly hard * durable*. For smallish
parts, baking is easily done in a kitchen oven...
Any good auto-paint store will have a one-step better "kit", cleaner,
converter, primer. Messy & time-consuming, but you can expect the paint
(any type) to stay on.
-dim

"Simon" wrote in message
...
snip

Owh lot's of questions, it is ten years ago since I'd my last chem
classes,
but I'll give it a shot.
Yes, you're right. Theoretical should one layer be enough, although
technically there are no alumiumoxide molecules. It is a salt and consist
of
positivly Aluminium ions and negativ charged oxygen atoms.
It al depends of the water enviroment, if the water is acid the aluminium
oxide (Al2O3) reacts:
6H+ + Al2O3 = 2 Al3+ + 3 H2O
in this enviroment the Al2O3 will solute like a sugar lump.
because of the disappearence of the protective Al2O3 the metal will react
with water
2 Al + 3 H2O = Al2O3 + 3 H2
so this will go on until all the H+ (acid) is used.

if the water is pH neutral Al2O3 will not solute.

if the water is basic (OH- ) the following will take place
Al2O3 + 6 OH- = 2 (AlO3)3- + 3 H2O (The (AlO3)3- is soluable in
this enviroment)
because of the disappearence of the protective Al2O3 the metal will react
with water
2 Al + 3 H2O = Al2O3 + 3 H2
so this will go on until all the (OH- ) (basic) is used.

2. I know the whhitish flaky stuff on aluminum is commonly called
"aluminum
oxide", but is it? Or is it more along the lines of aluminum salts?
(forgive
me if that's a really dumb question - last appology).

Hey lot's of salts are whitish crystaline flakes ;-) and Al2O3 is a salt.
So
good question. It could be Al2O3 but also something else (depending of the
enviroment) like Al(OH)3 (Aluminium hydroxide)

3. what is used as an electrolyte in 'lytics? It seems that it has to
be
al things to all people - it has to have great wetting. to get into the
scribed areas n the foil, really low R (faster cap /less heat),
shouldn't
leave a bunch of reactive gasses around, should be thermaly stable, and
shouldn't react with the (Al2O3?) when the voltage's off the cap...
Seems
like a tall order - i wonder what they use? Perhaps I should have payed
attention in chem. Are you sure the dielectric is actually Al2O3, and
not
something more stable? (been around too many aluminum boats...)

Ah, the electrolyt, a precious secret in the making of the elcap. In the
use
of a elcap there should be no chemical reaction. It is a capacitor like
this

aluminium | aluminium oxide | electrolytic fluid | aluminium oxide
|aluminium
--------| |-----------------------------------------|
|------------

because of the very thin layer of the non conductin aluminium oxide and
the
enormouse surface of the foil (it is etched to get an even greater
surface)
it can hold a hugh charge

The used electrolyt should be pH neutral and be a good conductor. I know
that in some elcaps picric acid or boric acid is used in combination with
other substances.
I heard that a good Elcap should have some leak current, this keeps the
layer Al2O3 on a certain thickness. If an elcap is not used for a long
time
the Al2O3 slowly get's thinner.

BTW
Aluminium is also used as a kind of sacrifice for protecting Iron boats.
Salty water is a good electrolyte and aluminium is a very non precious
metal. So a combinations of Iron, salty water and aluminium will act as a
sort of battery. This wil protect the iron from rusting.


Hi Simon -
Thanks for the explanations, and sorry 'bout not replying earlyer - i get
sidetracked easily. Oh, wwith the boat thing? I'm sure aluminum works, and
may be used on some steel boats, but zink is the usual sacrificial
electrode - basically, 'cos you can also use it on aluminum boats, and - i
don't know - it just is... You'll find it on every outboard motor, too...
I had the misfortune of doing the hull of a 40ft aluminum lobster boat -
never again...
-dim

For example: DON'T put some aluminium foil in a caustic soda solution,
the
aluminiumoxide will react with the caustic soda and leaving the under
laying
metal bare, this wil react with the water in the solution to form
aluminium
oxide and hydrogen, again the aluminium oxide will react with the
caustic
soda, leaving the metal bare, causing it to react with water, and so
on.
(don't try this at home folks, it is a vivid reaction).


Hey, we've got Crystal Drano here - I use it to clean & strip anodizing
off
aluminum. The first time i tried it was on a small heatsink in a
plastic
cup. Luckily, i left the cup in the sink - instant meltdown...

LOL


a water based proces. In this
proces (due to the water enviroment) the surface is covered with
aluminium
oxide.
So the insulator is aluminium oxide. Maybe, and just maybe, some parts
of
the electrolyte can be formed in the oxide layer during the forming
proces
of the (almost ready) elcap.

With regards,
Simon

yes, I didn't skip my chem classes :-)


Simon, where you the one who built tat homebrew amp which had, what I
thought was, cast end pieces, and ( i think it was you...) hunted for an
english word to describe the material, which you said was like dense
partical board? /runon If it was you, it's not your knowledge of
english
which failed you - we simply don't have this stuff around here. An
architect friend of mine showed me some samples - both from german
companies. Neat stuff - i've got the datasheets on it somwhere... thhe
only problem (at least with this stuff) is it's lack of tortional
strength -
if you bend or twist it, it breaks like particle board.
-dim

No that wasn't me, but I remember the post.
At the moment I'm working on a homebrew tube tester, but I've got so
little
time to work on it (I got a brand new son, he is 11 weeks old at the
moment
and needs all the attention)

Regards,

Simon

"Shiva" wrote

Around a year back there was a post by a RAT who worked for Alcoa
about
aluminum treatment methods & products. Have it saved
*somwhere*... worth
looking up.
What works for me is simply washing the stuff with laquer
thinner to get
rid of the oils, dipping it in a drano bath, then lots of hot
water, and
using an etching primer. I've also backed on wrinkle-black on
aluminum, and
it was durable. Motorcycle stores also used to have a product
called "case
paint", which, when backed on, was amazingly hard * durable*. For
smallish
parts, baking is easily done in a kitchen oven...
Any good auto-paint store will have a one-step better "kit",
cleaner,
converter, primer. Messy & time-consuming, but you can expect the
paint
(any type) to stay on.
-dim

Right. Any kind of top coat will do if it sticks to the primer.
The problem is getting the primer to stick to the Al, which in this
context is usually soft alloy, which is a worst-case scenario
because it is easiest to dink and hardest to stick to. As you point
out, thorough cleaning and use of *etch primer* for the first coat
is one solution.

Etch primer is definitely not easy to find here in local shops.
Perhaps wash with phosphoric acid? Perhaps if Al-bodied cars catch
on? "Is this good for Al?" gets a blank stare everywhere.

They do sell several branded general-purpose paints whose primers
say they are suitable for "metals" but tend to be a little
unspecific. One such is called "Plasti-Kote". I suspect this is a
US brand-name. Perhaps from the south... A zillion hardware shops
have it as their staple product.

Plasti-Kote appears to stick to Al. However, it takes months to
harden properly on metal. Baking speeds up the process but if too
hot there is a risk of crazing and/or dribbling and weird surface
effects that give a two-tone look in patches. If not hot enough it
makes no difference. No temperature advice is given.
Experimentation is costly and time-consuming.

Once the trauma of the painting and baking processes is over, the
paint scuffs off Al very easily. It is very thin even after five
top coats. Where two surfaces meet, such as a lid or a frame (as in
OP's question), it is virtually impossible to keep the paint intact.

I will experiment with "Hammerite" next, which I believe is silicon
based, and much harder. It is now available in smooth (rather than
hammered or crackle) finish.

All this trouble arose because I wanted green cases. It may have
been easier in the end to go to the anodiser, even though he is 20
miles away and a grumpy old bugger who uses green once in a blue
moon.

The "case paint" for bikes comes off after a while, too, unless used
with etch primer. Also, the alloy is stiff and cast, not like our
typical sheet.

Perhaps there is a cyano-acrylate alternative?

Finally, given the local alternatives of powder-coating or
anodising, I would go with the anodising any day, even though I
would have wait for the blue moon.

cheers, Ian

When painting aluminum try POR15, AP-120 Metal prep. and finish off with POR
15 engine enamel. Even when using a brush, it will look like it is sprayed
on.

Karsten

"Ian Iveson" wrote in message
...
"Shiva" wrote

Around a year back there was a post by a RAT who worked for Alcoa
about
aluminum treatment methods & products. Have it saved
*somwhere*... worth
looking up.
What works for me is simply washing the stuff with laquer
thinner to get
rid of the oils, dipping it in a drano bath, then lots of hot
water, and
using an etching primer. I've also backed on wrinkle-black on
aluminum, and
it was durable. Motorcycle stores also used to have a product
called "case
paint", which, when backed on, was amazingly hard * durable*. For
smallish
parts, baking is easily done in a kitchen oven...
Any good auto-paint store will have a one-step better "kit",
cleaner,
converter, primer. Messy & time-consuming, but you can expect the
paint
(any type) to stay on.
-dim

Right. Any kind of top coat will do if it sticks to the primer.
The problem is getting the primer to stick to the Al, which in this
context is usually soft alloy, which is a worst-case scenario
because it is easiest to dink and hardest to stick to. As you point
out, thorough cleaning and use of *etch primer* for the first coat
is one solution.

Etch primer is definitely not easy to find here in local shops.
Perhaps wash with phosphoric acid? Perhaps if Al-bodied cars catch
on? "Is this good for Al?" gets a blank stare everywhere.

They do sell several branded general-purpose paints whose primers
say they are suitable for "metals" but tend to be a little
unspecific. One such is called "Plasti-Kote". I suspect this is a
US brand-name. Perhaps from the south... A zillion hardware shops
have it as their staple product.

Plasti-Kote appears to stick to Al. However, it takes months to
harden properly on metal. Baking speeds up the process but if too
hot there is a risk of crazing and/or dribbling and weird surface
effects that give a two-tone look in patches. If not hot enough it
makes no difference. No temperature advice is given.
Experimentation is costly and time-consuming.

Once the trauma of the painting and baking processes is over, the
paint scuffs off Al very easily. It is very thin even after five
top coats. Where two surfaces meet, such as a lid or a frame (as in
OP's question), it is virtually impossible to keep the paint intact.

I will experiment with "Hammerite" next, which I believe is silicon
based, and much harder. It is now available in smooth (rather than
hammered or crackle) finish.

All this trouble arose because I wanted green cases. It may have
been easier in the end to go to the anodiser, even though he is 20
miles away and a grumpy old bugger who uses green once in a blue
moon.

The "case paint" for bikes comes off after a while, too, unless used
with etch primer. Also, the alloy is stiff and cast, not like our
typical sheet.

Perhaps there is a cyano-acrylate alternative?

Finally, given the local alternatives of powder-coating or
anodising, I would go with the anodising any day, even though I
would have wait for the blue moon.

cheers, Ian

black beauties rule dude...they are the best


On Sun, 21 Sep 2003 23:35:10 +1000, Patrick Turner
wrote:



Gregg wrote:

Hi,

I can't hear the difference with classical music, let alone a guitar
head. IMO, the difference acoustically will be moot.

Indeed this is the case, especially with class A PP amps,
which have inherent common mode rejection of PS noise,
but only while they work in class A.



Physically, OTOH, poly's will kick butt on the 'lytics because:

1) they are less temprature sensitive

True, but who is gonna allow the elcaps to go to 105C?


2) they take AC currents without damage

Operating well within ratings, elcaps are fine,
and millions of SMPS where the mains is just rectified
and then the DC is chopped, means the elcaps are FAR better
than they used to be 40 years ago, where they got a poor reputation.
Its far cheaper and more effective to use a large value elcap.
try 470 uF poly cap, its HUGE, and impractical, so values are
limited to less than 100 uF in tube amp PS, and still the cap is huge,
and a very high value inductor has to be used.


3) they tend to be self-healing on overload

Yes, they are good there, arcs tend to heal.
but the higher the V rating, the bigger the cap.


4) the low-leakage of poly's will save tubes in the future and make for
more stable bias

The same could be said of elcaps.
Todays have leakage quite low enough.
Especially in low current bias circuits where they will last
an enormously long time, if set up to run with 1/2 to 2/3 of their
wkg DV.


5) they age better than 'lytics

Maybe they do, but todays elcaps seem to last heck of a time.
Active detectors of over currents in cathode circuits which switch off the
amp,
or the B+ will prevent excess PS current draw in a fault.
Operating elcaps above their ripple current ability does strain the hell
out of elcaps,
and is what is mainly the reason
for their over heating and death, since higher than normal DC causes
higher than normal AC, or ripple current, beyond their rating.
So design for 100% overload of B+ current, and add active over current
protection, and the elcaps will last, and the costs will be far lower than
the same uF used in poly caps.



I have had many old radios from 1950 with all the electros still working
OK.

Replacing them is dirt cheap, and effective, and poly caps
or paper in oil makes precious little difference to the sound, if anything.

In SE designs, low ripple of perhaps 5 mV at the input to the OPT
is what should be aimed for, along with a super low impedance
B+ supply, even at 10 Hz, and one which is non resonant above 7 Hz.
So if you have only 100 uF cap to anchor the OPT B+, then its impedance
at 10 Hz is 160 ohms, and the preceeding choke needs to be 5H,
to get Fo = 7 Hz.
The 100 Hz ripple reduction factor of 5H + 100 uF is only 16/3140, or .025,

so if the C1 in a CLC PS is 100 uF, and DC = 0.2 amps,
initial ripple at C1 = 4.4 rms, and at C2 = 110 mV, which is 10 times
higher
than what I think is needed for an SE hi-fi amp.
So the use of 470 uF elcaps, even in series, say 2 x 350v rated with a 500
v supply
and the SAME sized choke, and silicon rectifiers will give a final
filter of 235 uF, 5H, 235 uF, and giving ripple voltage of 4 mV at the C2.
To be sure about bypassing really high RF, use a 0.47 uF polypropylene
at 630v rating across C1 and C2.
The Fo of the LC2 filter after C1 will be 5 Hz.

Most SMPS elcaps are rated to work OK as real capacitors at least to
100 kHz, and then the ESR and series L starts to increase, but
at 100 kHz, 0.47 uF has become 3.3 ohms, with declining Z
at 6 dB/octave above this F.

But most tube amps work fine without the additional poly cap
for RF bypassing, because the stray Cshunt of the OPT bypasses any RF,
and the leakage inductance and stray C act as a filter to prevent
RF transmission through the OPT.

For caps apart from the PS, use whatever turns you on,
and I hear ppl say Auricaps, or teflon types, or paper in oils are OK,
but paper + foil in beeswax appeals as well, but the jury can't come to a
verdict
on what sounds the best.

Maybe its all good sounding, just different goodness.

Figures for ripple quoted are for 50 Hz mains, full wave rectifiers.

Patrick Turner.


--
Gregg
*It's probably useful, even if it can't be SPICE'd*
http://geek.scorpiorising.ca

503-810-1223

I've replaced all the electrolytics in my amp with polyprops, including all
power supply and all cathode bypasses. Downside - they're huge and cost money.
Upside - they sound better, and the difference is enough to make it well
worthwhile for me.

=== Andy Evans ===
Visit our Website:- http://www.artsandmedia.com
Audio, music and health pages and interesting links.