"John Williamson" wrote in message
...
Serge Auckland wrote:

As the 405 is now quite old, if it has sibilence then it may need some
of its electrolytic caps replaced, but that's about all. Many of the NAD
amps have external pre-power links that can be removed and they make a
good pre-amp with plenty of inputs.

I fail to understand how old electrolytics could produce sibilance.

As they age, the value of electrolytics tends to drop markedly, even if
they don't fail totally open circuit, which increases the impedance more
at low frequencies than high, so the low frequencies get lost on the way
through. If they're in a feedback/ equalisation circuit, it can affect
things either way.

--
Tciao for Now!

John.

That makes a certain amount of sense, but only applies to those
electrolytics used directly in the signal path for coupling, or those used
to bypass resistors, for example, emitter loads. Those electrolytics used
for power supply smoothing will only cause an increase in hum and /or an
increase in distortion as the voltage rails sag.

S.

--
http://audiopages.googlepages.com

On Wed, 20 Feb 2008 21:18:46 +0000, John Williamson
wrote:

Serge Auckland wrote:

As the 405 is now quite old, if it has sibilence then it may need some
of its electrolytic caps replaced, but that's about all. Many of the
NAD amps have external pre-power links that can be removed and they
make a good pre-amp with plenty of inputs.

I fail to understand how old electrolytics could produce sibilance.

As they age, the value of electrolytics tends to drop markedly, even if
they don't fail totally open circuit, which increases the impedance more
at low frequencies than high, so the low frequencies get lost on the way
through. If they're in a feedback/ equalisation circuit, it can affect
things either way.

But whichever way the effect goes, it will be hitting the extreme
lows, not the highs. So whatever the result, it won't be sibilance.

d

--
Pearce Consulting
http://www.pearce.uk.com

"Don Pearce" wrote in message
...
On Wed, 20 Feb 2008 21:18:46 +0000, John Williamson
wrote:

Serge Auckland wrote:

As the 405 is now quite old, if it has sibilence then it may need some
of its electrolytic caps replaced, but that's about all. Many of the
NAD amps have external pre-power links that can be removed and they
make a good pre-amp with plenty of inputs.

I fail to understand how old electrolytics could produce sibilance.

As they age, the value of electrolytics tends to drop markedly, even if
they don't fail totally open circuit, which increases the impedance more
at low frequencies than high, so the low frequencies get lost on the way
through. If they're in a feedback/ equalisation circuit, it can affect
things either way.

But whichever way the effect goes, it will be hitting the extreme
lows, not the highs. So whatever the result, it won't be sibilance.

d

--
Pearce Consulting
http://www.pearce.uk.com


I'm assuming John means that by reducing the lows, the subjective effect is
a boost in the highs, which he translates as sibilance. I find it all rather
unlikely, but I'm prepared to admit the possibility.

S.

--
http://audiopages.googlepages.com

On Thu, 21 Feb 2008 13:29:31 -0000, "Serge Auckland"
wrote:

"Don Pearce" wrote in message
...
On Wed, 20 Feb 2008 21:18:46 +0000, John Williamson
wrote:

Serge Auckland wrote:

As the 405 is now quite old, if it has sibilence then it may need some
of its electrolytic caps replaced, but that's about all. Many of the
NAD amps have external pre-power links that can be removed and they
make a good pre-amp with plenty of inputs.

I fail to understand how old electrolytics could produce sibilance.

As they age, the value of electrolytics tends to drop markedly, even if
they don't fail totally open circuit, which increases the impedance more
at low frequencies than high, so the low frequencies get lost on the way
through. If they're in a feedback/ equalisation circuit, it can affect
things either way.

But whichever way the effect goes, it will be hitting the extreme
lows, not the highs. So whatever the result, it won't be sibilance.

d

--
Pearce Consulting
http://www.pearce.uk.com


I'm assuming John means that by reducing the lows, the subjective effect is
a boost in the highs, which he translates as sibilance. I find it all rather
unlikely, but I'm prepared to admit the possibility.

S.

I see what you are saying, but cutting lows doesn't really sound like
boosting highs - the middles are the important bits here, and if they
stay constant relative to the highs (which they will in a low cap
scenario) the result won't sound anything like sibilance.

But people's perceptions do differ, I will admit.

d

--
Pearce Consulting
http://www.pearce.uk.com

"Don Pearce" wrote in message

On Wed, 20 Feb 2008 21:18:46 +0000, John Williamson
wrote:

Serge Auckland wrote:

As the 405 is now quite old, if it has sibilence then
it may need some of its electrolytic caps replaced,
but that's about all. Many of the NAD amps have
external pre-power links that can be removed and they
make a good pre-amp with plenty of inputs.

I fail to understand how old electrolytics could
produce sibilance.

As they age, the value of electrolytics tends to drop
markedly, even if they don't fail totally open circuit,
which increases the impedance more at low frequencies
than high, so the low frequencies get lost on the way
through. If they're in a feedback/ equalisation circuit,
it can affect things either way.

But whichever way the effect goes, it will be hitting the
extreme lows, not the highs. So whatever the result, it
won't be sibilance.

IME, doing a nice job on the more extreme lows can make some overabundence
of extreme highs more tolerable.

Don Pearce wrote:
On Thu, 21 Feb 2008 13:29:31 -0000, "Serge Auckland"
wrote:

"Don Pearce" wrote in message
...
On Wed, 20 Feb 2008 21:18:46 +0000, John Williamson
wrote:

Serge Auckland wrote:

As the 405 is now quite old, if it has sibilence then it may need some
of its electrolytic caps replaced, but that's about all. Many of the
NAD amps have external pre-power links that can be removed and they
make a good pre-amp with plenty of inputs.
I fail to understand how old electrolytics could produce sibilance.

As they age, the value of electrolytics tends to drop markedly, even if
they don't fail totally open circuit, which increases the impedance more
at low frequencies than high, so the low frequencies get lost on the way
through. If they're in a feedback/ equalisation circuit, it can affect
things either way.
But whichever way the effect goes, it will be hitting the extreme
lows, not the highs. So whatever the result, it won't be sibilance.

d

--
Pearce Consulting
http://www.pearce.uk.com

I'm assuming John means that by reducing the lows, the subjective effect is
a boost in the highs, which he translates as sibilance. I find it all rather
unlikely, but I'm prepared to admit the possibility.

S.

I see what you are saying, but cutting lows doesn't really sound like
boosting highs - the middles are the important bits here, and if they
stay constant relative to the highs (which they will in a low cap
scenario) the result won't sound anything like sibilance.

But people's perceptions do differ, I will admit.

d

That *was* my thought, as the highs are boosted relative to the lows, &
if the combination of amp & speaker is already a bit shrill, turning the
gain up to get the same sound pressure could sound sibilant.

Depending on the circuit impedances, the change in capacitance in
combination with the self inductance of the electrolytic *may*
accentuate or create a resonance peak in the audio range. Unlikely, but
maybe...

--
Tciao for Now!

John.

"John Williamson" wrote in message
...
Don Pearce wrote:
On Thu, 21 Feb 2008 13:29:31 -0000, "Serge Auckland"
wrote:

"Don Pearce" wrote in message
...
On Wed, 20 Feb 2008 21:18:46 +0000, John Williamson
wrote:

Serge Auckland wrote:

As the 405 is now quite old, if it has sibilence then it may need
some
of its electrolytic caps replaced, but that's about all. Many of the
NAD amps have external pre-power links that can be removed and they
make a good pre-amp with plenty of inputs.
I fail to understand how old electrolytics could produce sibilance.

As they age, the value of electrolytics tends to drop markedly, even
if
they don't fail totally open circuit, which increases the impedance
more
at low frequencies than high, so the low frequencies get lost on the
way
through. If they're in a feedback/ equalisation circuit, it can affect
things either way.
But whichever way the effect goes, it will be hitting the extreme
lows, not the highs. So whatever the result, it won't be sibilance.

d

--
Pearce Consulting
http://www.pearce.uk.com

I'm assuming John means that by reducing the lows, the subjective effect
is a boost in the highs, which he translates as sibilance. I find it all
rather unlikely, but I'm prepared to admit the possibility.

S.

I see what you are saying, but cutting lows doesn't really sound like
boosting highs - the middles are the important bits here, and if they
stay constant relative to the highs (which they will in a low cap
scenario) the result won't sound anything like sibilance.

But people's perceptions do differ, I will admit.

d

That *was* my thought, as the highs are boosted relative to the lows, & if
the combination of amp & speaker is already a bit shrill, turning the gain
up to get the same sound pressure could sound sibilant.

Depending on the circuit impedances, the change in capacitance in
combination with the self inductance of the electrolytic *may* accentuate
or create a resonance peak in the audio range. Unlikely, but maybe...


Don't forget that as an electrolytic fails it's ESR rises significantly, and
may become non-linear. Depending on it's circuit function that might result
in an increase in HF distortion.

David.

Woody wrote:
For my two pen'uth, if you have a 405 get it fixed and use that. Quad
were always designed to be able to handle complex loads - think of the
Electrostatics for a start - and are difficult to break.

As the 405 is now quite old, if it has sibilence then it may need some
of its electrolytic caps replaced, but that's about all. Many of the NAD
amps have external pre-power links that can be removed and they make a
good pre-amp with plenty of inputs.

The circuit diagram of the 405 is in its handbook if you have it,
otherwise it should be easy to Google.


I gather they're not the most complicated to get serviced/repaired. It's
a case of time/energy and relative ease of punting via ebay.


If you want to get something else the Audiolab 8000A takes some beating
but it is very revealing and may show up the failings of the rest of
your kit.


Indeed :-) I had a 8000A for a few years and was quite happy with it,
especially the phono amp, but that was before the Dynaudio phase. ATM,
and after some fairly brief comparisons, I've settled with an old power
amp that *seems* to do the trick, and at least relieves the urge to
spend needlessly. When and if work eases off I'll give it a more
thorough assessment, but for now it's enough just to listen to some music.

Thanks for the advice; appreciated.

Rob

Rob wrote:
Woody wrote:
For my two pen'uth, if you have a 405 get it fixed and use that. Quad
were always designed to be able to handle complex loads - think of the
Electrostatics for a start - and are difficult to break.

As the 405 is now quite old, if it has sibilence then it may need some
of its electrolytic caps replaced, but that's about all. Many of the
NAD amps have external pre-power links that can be removed and they
make a good pre-amp with plenty of inputs.

The circuit diagram of the 405 is in its handbook if you have it,
otherwise it should be easy to Google.


I gather they're not the most complicated to get serviced/repaired. It's
a case of time/energy and relative ease of punting via ebay.


If you want to get something else the Audiolab 8000A takes some
beating but it is very revealing and may show up the failings of the
rest of your kit.


Indeed :-) I had a 8000A for a few years and was quite happy with it,
especially the phono amp, but that was before the Dynaudio phase. ATM,
and after some fairly brief comparisons, I've settled with an old power
amp that *seems* to do the trick, and at least relieves the urge to
spend needlessly. When and if work eases off I'll give it a more
thorough assessment, but for now it's enough just to listen to some music.

Thanks for the advice; appreciated.

Rob

Quick update - I've settled on the Behringer 500 for now, using the
Cambridge AV as a preamp. It certainly deals with the bass side very
well, but is a little harsh when pushed (which I don't do that often).
No pleasing some people :-)

I commented earlier that it seems to clip readily. In fact I only tried
it for a few days when new, and then put it in the cupboard. My comment
came from watching the LEDs, which indicated clipping. Subjectively on
listening it's not that bad, and the amp will go very loud indeed.

Rob