Effect of Variac on Monoblocks

Effect of Variac on Monoblocks

I happened to snag a set of 63V/10,000ufd FK BG caps for my monoblock
PSUs. The rail voltage with stock Hafler xmfr is ~ 63 Volts so to
avoid exploding my $$ BGs, I'm using a Variac to reduce the AC mains
input for a rail Voltage of ~ 53 volts until I replace the Hafler
trafos with lower sec V Toroidals. [Refer to "Hafler Monoblock
Project..." thread]

The mystery is the sound, which is sort of peculiar. Hard to explain,
but what is the source? Of course there are 3 variables that have been
changed: PSU caps from Chemicons to BGs, lower rail voltage (well
within the operating range of the PA-3D driver board), and inclusion
of the Variac twixt house mains and both amps.

Should I expect some odd interaction between the Variac and existing
Hafler power xfmr? Nothing obvious comes to mind. Running stone cold,
the 1500VA, Powerstat Variac has plenty of capacity.

Not much to go on here, but thought I would throw this one out to you
guys. Thanks again...
Dave

Re: Effect of Variac on Monoblocks


"Wink" <x@x . net > wrote in message
news:2c2du3529iu69fpq2np7cmfr61405lvb68@4ax . com ...
>I happened to snag a set of 63V/10,000ufd FK BG caps for my monoblock
> PSUs. The rail voltage with stock Hafler xmfr is ~ 63 Volts so to
> avoid exploding my $$ BGs, I'm using a Variac to reduce the AC mains
> input for a rail Voltage of ~ 53 volts until I replace the Hafler
> trafos with lower sec V Toroidals. [Refer to "Hafler Monoblock
> Project..." thread]
>
> The mystery is the sound, which is sort of peculiar. Hard to explain,
> but what is the source? Of course there are 3 variables that have been
> changed: PSU caps from Chemicons to BGs, lower rail voltage (well
> within the operating range of the PA-3D driver board), and inclusion
> of the Variac twixt house mains and both amps.
>
> Should I expect some odd interaction between the Variac and existing
> Hafler power xfmr? Nothing obvious comes to mind. Running stone cold,
> the 1500VA, Powerstat Variac has plenty of capacity.
>
> Not much to go on here, but thought I would throw this one out to you
> guys. Thanks again...
> Dave


Ought to work fine.

Mark Z.

Re: Effect of Variac on Monoblocks

>The mystery is the sound, which is sort of peculiar. Hard to explain,
>but what is the source? Of course there are 3 variables that have been
>changed: PSU caps from Chemicons to BGs, lower rail voltage (well
>within the operating range of the PA-3D driver board), and inclusion
>of the Variac twixt house mains and both amps.

Just a guess, but: if you're dropped the rail voltage, you may also
have disturbed the biasing of one or more of the amplifier's stages.
The drivers or finals could now be running with a lower level of
standing current... and if this is too low, the amp might be suffering
from some amount of crossover distortion.

--
Dave Platt <dplatt@radagast.org> AE6EO
Friends of Jade Warrior home page: * w w w .radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Re: Effect of Variac on Monoblocks

In article <2c2du3529iu69fpq2np7cmfr61405lvb68@4ax . com >, Wink <x@x . net >
wrote:

> I happened to snag a set of 63V/10,000ufd FK BG caps for my monoblock
> PSUs. The rail voltage with stock Hafler xmfr is ~ 63 Volts so to
> avoid exploding my $$ BGs, I'm using a Variac to reduce the AC mains
> input for a rail Voltage of ~ 53 volts until I replace the Hafler
> trafos with lower sec V Toroidals. [Refer to "Hafler Monoblock
> Project..." thread]
>
> The mystery is the sound, which is sort of peculiar. Hard to explain,
> but what is the source? Of course there are 3 variables that have been
> changed: PSU caps from Chemicons to BGs, lower rail voltage (well
> within the operating range of the PA-3D driver board), and inclusion
> of the Variac twixt house mains and both amps.
>
> Should I expect some odd interaction between the Variac and existing
> Hafler power xfmr? Nothing obvious comes to mind. Running stone cold,
> the 1500VA, Powerstat Variac has plenty of capacity.
>
> Not much to go on here, but thought I would throw this one out to you
> guys. Thanks again...
> Dave

If this is one of those fancy amplifiers where the pull-up and pull-down
are perfectly balanced, then it probably has minimal regulation on the
bias currents. It will change sound if the average power supply voltage
is too far off. 53V minus load drooping is probably out of normal
operating range.

--
I don't read Google's spam. Reply with another service.

Re: Effect of Variac on Monoblocks

"Kevin McMurtrie" <mcmurtri@dslextreme . com > wrote in
message
news:mcmurtri-BBC54B.11432623032008@news.dslextreme . com

> If this is one of those fancy amplifiers where the
> pull-up and pull-down are perfectly balanced,

Please explain further.

Re: Effect of Variac on Monoblocks

Interesting answers guys. That pa-3d driver card is designed to
operate over a wide voltage range. It is used in the DH-500 which has
90 volt rails. I'll have to talk John Hillig at Musical Concepts about
this. The waveform is fully integrated at something like 17 V rails
and 70 ma. idle bias.

The card uses a single ended front end and I believe Cascoded current
follower output device drivers.

These blocks sound pretty good with Chemi-cons (not old stock
Sangamos) at the 63 V design rail voltage Frankly though, I bought
Clayton S-40, 50 W class A per channel, and it is verging on magical.

I have doubts about whether my blocks will ever compete. Not the
result I was seeking.
Dave




On Sun, 23 Mar 2008 12:35:17 -0500, Wink <x@x . net > wrote:

>I happened to snag a set of 63V/10,000ufd FK BG caps for my monoblock
>PSUs. The rail voltage with stock Hafler xmfr is ~ 63 Volts so to
>avoid exploding my $$ BGs, I'm using a Variac to reduce the AC mains
>input for a rail Voltage of ~ 53 volts until I replace the Hafler
>trafos with lower sec V Toroidals. [Refer to "Hafler Monoblock
>Project..." thread]
>
>The mystery is the sound, which is sort of peculiar. Hard to explain,
>but what is the source? Of course there are 3 variables that have been
>changed: PSU caps from Chemicons to BGs, lower rail voltage (well
>within the operating range of the PA-3D driver board), and inclusion
>of the Variac twixt house mains and both amps.
>
>Should I expect some odd interaction between the Variac and existing
>Hafler power xfmr? Nothing obvious comes to mind. Running stone cold,
>the 1500VA, Powerstat Variac has plenty of capacity.
>
>Not much to go on here, but thought I would throw this one out to you
>guys. Thanks again...
>Dave

Re: Effect of Variac on Monoblocks



Wink wrote:

> These blocks sound pretty good with Chemi-cons (not old stock
> Sangamos) at the 63 V design rail voltage

Your obsession with capacitor brand is quite absurd. Look elsewhere for
what's causing any apparent difference.

Graham

Re: Effect of Variac on Monoblocks

"Wink" <x@x . net > wrote in message
news:2c2du3529iu69fpq2np7cmfr61405lvb68@4ax . com

> I happened to snag a set of 63V/10,000ufd FK BG caps for
> my monoblock PSUs. The rail voltage with stock Hafler
> xmfr is ~ 63 Volts so to avoid exploding my $$ BGs, I'm
> using a Variac to reduce the AC mains input for a rail
> Voltage of ~ 53 volts until I replace the Hafler trafos
> with lower sec V Toroidals. [Refer to "Hafler Monoblock
> Project..." thread]

Running 63 volt rated caps at 63 volts will probably not cause explosions,
but it will shorten their useful life to spec, given other operating
conditions are spec. Since you probably aren't running them as warm as spec,
they will probably still live longer than spec. Furthermore, its not like
electrolytics explode if run 1 volt over spec. They can probably take 20% or
more overvoltage, with no undesireably results other than a somewhat
shortened life.

Bottom line, you could experiment for a few minutes or a few hours with
rated power line voltage being appled, and nothing bad would happen.

> The mystery is the sound, which is sort of peculiar.

And of course, being an unwashed amateur, you have no proper listening tests
to back this up. With all due respect, which ain't much, why would anybody
with a brain even comment on your random perceptions?

You probably are scrunching up your ears every time you listen to these amps
because you *know* about the *violence* that is going on inside. Come back
when you've got evidence of something more electronic and technical than the
state of your mind. :-(

> Hard to explain, but what is the source?

Your state of mental stress due to your under-rated caps, which aren't all
that under-rated?

> Of course there are 3
> variables that have been changed: PSU caps from Chemicons
> to BGs, lower rail voltage (well within the operating
> range of the PA-3D driver board), and inclusion of the
> Variac twixt house mains and both amps.

Not to mention your obvious state of guilt and self-deinal.

> Should I expect some odd interaction between the Variac
> and existing Hafler power xfmr? Nothing obvious comes to
> mind. Running stone cold, the 1500VA, Powerstat Variac
> has plenty of capacity.

Well, the Variac probably adds a little ESR, and may shift the harmonic
content of the powerline measurably. But on balance, those are the sorts of
thing that a well-designed power amp is supposed to take in stride.

> Not much to go on here, but thought I would throw this
> one out to you guys.

If the origional caps were OK, then the added/replaced caps were acts of
either futility or obsessive behavior. If they weren't OK, why didn't you
get proper caps instead of inflicting this marginally-rated crap on your
psyche?

Seriously!

As far as the bias-shift theory goes, the fact is that a well-designed power
amp can't be allowed to suddenly fall apart because the rail voltages are
20% or whatever low.

IME a lot of power amp output stages will do a credible job of amplifying
when the rail voltage is 20% of spec. Not 20% low, but 20% of. Of course the
power output will be only about 10% of spec, but what do you expect, power
from no where? ;-)

Re: Effect of Variac on Monoblocks



Arny Krueger wrote:

> Running 63 volt rated caps at 63 volts will probably not cause explosions,
> but it will shorten their useful life to spec, given other operating
> conditions are spec

NO !

What kills capacitors is HEAT. The vast majority of that heat comes from the
effect of ripple current, absolutely NOT applied voltage which merely affects
the leakage current.

A 63V rated cap is *designed* to be used at 63V. It will likely have a 'surge
rating' of around 80V but that's rarely publicised these days.


Graham

Re: Effect of Variac on Monoblocks

A glorious response. Curious in light of previous helpful and cordial
ones, free of your compulsive cruelty.

I'm not an objectivist Arny. I've tried to be, the scientist within
compels it; but amps sound different, quite different frequently.

ICs and cables: I've been a maximum skeptic for decades, using
generics and zip cord. But recent experiments have shown that these
items do indeed sound different, frequently meaningfully. It is
distressing, looking for the physics, and the yet the conclusion is
inescapable.

I'm convinced that, though objectivists do not necessarily have
inferior ears, they may have ears which are insensitive to things the
subjectivists detect. Like my wife who can distinguish colors that
look utterly the same to me.

AB, ABX testing is useless. Sometimes amp problems/ strengths take
weeks to emerge. The instantaneous nature of the AB test does not
allow enough time for the ear-brain to acquire the target. This is not
true of speakers generally because of the massive differences between
designs. Sufficient differential for near instant target acquisition.

Anyway, keep the responses coming. I need smattering of high quality,
gratuitous immaturity in my day, and yours is of the highest quality.

I'm not running 800 bucks worth of 63 V lytics at 63 Volts. Not
necessary.
Dave


On Mon, 24 Mar 2008 09:27:16 -0400, "Arny Krueger" <arnyk@hotpop . com >
wrote:

>"Wink" <x@x . net > wrote in message
>news:2c2du3529iu69fpq2np7cmfr61405lvb68@4ax . com
>
>> I happened to snag a set of 63V/10,000ufd FK BG caps for
>> my monoblock PSUs. The rail voltage with stock Hafler
>> xmfr is ~ 63 Volts so to avoid exploding my $$ BGs, I'm
>> using a Variac to reduce the AC mains input for a rail
>> Voltage of ~ 53 volts until I replace the Hafler trafos
>> with lower sec V Toroidals. [Refer to "Hafler Monoblock
>> Project..." thread]
>
>Running 63 volt rated caps at 63 volts will probably not cause explosions,
>but it will shorten their useful life to spec, given other operating
>conditions are spec. Since you probably aren't running them as warm as spec,
>they will probably still live longer than spec. Furthermore, its not like
>electrolytics explode if run 1 volt over spec. They can probably take 20% or
>more overvoltage, with no undesireably results other than a somewhat
>shortened life.
>
>Bottom line, you could experiment for a few minutes or a few hours with
>rated power line voltage being appled, and nothing bad would happen.
>
>> The mystery is the sound, which is sort of peculiar.
>
>And of course, being an unwashed amateur, you have no proper listening tests
>to back this up. With all due respect, which ain't much, why would anybody
>with a brain even comment on your random perceptions?
>
>You probably are scrunching up your ears every time you listen to these amps
>because you *know* about the *violence* that is going on inside. Come back
>when you've got evidence of something more electronic and technical than the
>state of your mind. :-(
>
>> Hard to explain, but what is the source?
>
>Your state of mental stress due to your under-rated caps, which aren't all
>that under-rated?
>
>> Of course there are 3
>> variables that have been changed: PSU caps from Chemicons
>> to BGs, lower rail voltage (well within the operating
>> range of the PA-3D driver board), and inclusion of the
>> Variac twixt house mains and both amps.
>
>Not to mention your obvious state of guilt and self-deinal.
>
>> Should I expect some odd interaction between the Variac
>> and existing Hafler power xfmr? Nothing obvious comes to
>> mind. Running stone cold, the 1500VA, Powerstat Variac
>> has plenty of capacity.
>
>Well, the Variac probably adds a little ESR, and may shift the harmonic
>content of the powerline measurably. But on balance, those are the sorts of
>thing that a well-designed power amp is supposed to take in stride.
>
>> Not much to go on here, but thought I would throw this
>> one out to you guys.
>
>If the origional caps were OK, then the added/replaced caps were acts of
>either futility or obsessive behavior. If they weren't OK, why didn't you
>get proper caps instead of inflicting this marginally-rated crap on your
>psyche?
>
>Seriously!
>
>As far as the bias-shift theory goes, the fact is that a well-designed power
>amp can't be allowed to suddenly fall apart because the rail voltages are
>20% or whatever low.
>
>IME a lot of power amp output stages will do a credible job of amplifying
>when the rail voltage is 20% of spec. Not 20% low, but 20% of. Of course the
>power output will be only about 10% of spec, but what do you expect, power
>from no where? ;-)
>
>

Re: Effect of Variac on Monoblocks



Wink wrote:

> I'm not running 800 bucks worth of 63 V lytics at 63 Volts. Not
> necessary.

What a shocking waste of money !

Transistor amps by design (large degrees of negative feedback whether local,
overall or both) and by virtue of the inherent high collector resistance of the
active devices are very little affected by signal on the power rails.

In any case, the AC voltage on the DC rails will be mostly 100/120 Hz ripple. And
fitting Black Gates will make ZERO difference to that.

At best you've simply not made your amp any WORSE by fitting BGs but it's an
insane waste of money. What on earth did you expect it to do and most of all **
WHY ** ?

Graham

Re: Effect of Variac on Monoblocks

"Eeyore" <rabbitsfriendsandrelations@hotmail . com > wrote in
message news:47E7CEAE.853CA138@hotmail . com

> Wink wrote:

>> I'm not running 800 bucks worth of 63 V lytics at 63
>> Volts. Not necessary.

Did we read this right? Is this a typo? Was there an extra zero in that
price?

> What a shocking waste of money !

Agreed.

> Transistor amps by design (large degrees of negative
> feedback whether local, overall or both) and by virtue of
> the inherent high collector resistance of the active
> devices are very little affected by signal on the power
> rails.

Agreed.

> In any case, the AC voltage on the DC rails will be
> mostly 100/120 Hz ripple. And fitting Black Gates will
> make ZERO difference to that.

Agreed.

> At best you've simply not made your amp any WORSE by
> fitting BGs but it's an insane waste of money. What on
> earth did you expect it to do and most of all ** WHY ** ?

Graham, I don't think we should waste much time on a certifiable loonie who
puts $400-800 worth of caps in a single amplifier. He's living in a
different universe from the rest of of!

Re: Effect of Variac on Monoblocks



Arny Krueger wrote:

> "Eeyore" <rabbitsfriendsandrelations@hotmail . com > wrote in
>
> > At best you've simply not made your amp any WORSE by
> > fitting BGs but it's an insane waste of money. What on
> > earth did you expect it to do and most of all ** WHY ** ?
>
> Graham, I don't think we should waste much time on a certifiable loonie who
> puts $400-800 worth of caps in a single amplifier. He's living in a
> different universe from the rest of of!

I do like to (try to) explain to the crazies that there are actually perfectly
'sound' - lol - scientific reasons for what they appear to think are mysterious
differences that they then attribute to component swaps or some kind of magick
generally.

It's a hard task but someone's got to do it !

Graham

Re: Effect of Variac on Monoblocks

"Wink" <x@x . net > wrote in message
news:uekfu3ta1h635eufi9up0rsvf12ukhr1pv@4ax . com

> A glorious response. Curious in light of previous helpful
> and cordial ones, free of your compulsive cruelty.

The kindest thing I can say to someone who is making decisions based on
questionable information...

> I'm not an objectivist Arny.

Neither am I.

> I've tried to be, the
> scientist within compels it; but amps sound different,
> quite different frequently.

It always happens for a reason, and the reason often has nothing to do with
amplifier performance. It often has to do with the circumstances of the
listening evaluation.

> ICs and cables: I've been a maximum skeptic for decades,
> using generics and zip cord. But recent experiments have
> shown that these items do indeed sound different,
> frequently meaningfully. It is distressing, looking for
> the physics, and the yet the conclusion is inescapable.

No such thing - try doing some reasonable tests.

> I'm convinced that, though objectivists do not
> necessarily have inferior ears, they may have ears which
> are insensitive to things the subjectivists detect.

Interesting how the subjectivist's ears work the same when the sighted cues
and other asymmetries are removed from the evaluation.

> Like my wife who can distinguish colors that look utterly the
> same to me.

OK, so you are a little color blind.

> AB, ABX testing is useless.

So how do you do a listening test? Any comparison of two pieces of
equipment can be called an AB test.

> Sometimes amp problems
> strengths take weeks to emerge.

If it is real, there is always a reason.

> The instantaneous nature
> of the AB test does not allow enough time for the
> ear-brain to acquire the target.

Who said that an AB test has to be instantaneous?

I've heard this straw man argument 100's of times. :-(

> This is not true of
> speakers generally because of the massive differences
> between designs. Sufficient differential for near instant
> target acquisition.

Maybe yes, maybe no.

> Anyway, keep the responses coming. I need smattering of
> high quality, gratuitous immaturity in my day, and yours
> is of the highest quality.

Actually, some of the original ABX crew is now well on their way to their
70s, and their immaturity is such that they have credibility in the audio
industry that you probably don't even know exists.

Immaturity, indeed. :-(

> I'm not running 800 bucks worth of 63 V lytics at 63
> Volts. Not necessary.

You paid $800 for the electrolytics for a power amp or two?

Freakin' unbelievable. :-(

Re: Effect of Variac on Monoblocks

Wink <x@x . net > wrote:
> A glorious response. Curious in light of previous helpful and cordial
> ones, free of your compulsive cruelty.
>
> I'm not an objectivist Arny. I've tried to be, the scientist within
> compels it; but amps sound different, quite different frequently.
>
> ICs and cables: I've been a maximum skeptic for decades, using
> generics and zip cord. But recent experiments have shown that these
> items do indeed sound different, frequently meaningfully. It is
> distressing, looking for the physics, and the yet the conclusion is
> inescapable.
>
> I'm convinced that, though objectivists do not necessarily have
> inferior ears, they may have ears which are insensitive to things the
> subjectivists detect. Like my wife who can distinguish colors that
> look utterly the same to me.

Actually there is a possible scientific explanation for this: a small
number of women can actually see far more colors than the usual 16
million or so. I forget the details, but their retinal structure is
actually different.

Jerry