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Class ABDH



 
 
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  #1  
Old March 16th 18, 06:01 AM posted to alt.comp.hardware.pc-homebuilt
Flasherly[_2_]
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Posts: 2,048
Default Class ABDH

Don't make 'em to last. Supposed studio-grade ART amp, two models,
which I'm glad I didn't buy the more powerful of the two. It has a
characteristic output heat difference: one channel's output
transformers are hotter than the other. I noticed the heat
discrepancy from day one, when I first plugged the unit in. Very
basic sensory perceptions being not much more than a casual note, or
why else would not I have returned or at least replaced it with
another new unit. A perfectly respectable note from a repair or
technician's standpoint, to point out sequential serial production
models, any amp manufacturer may occasionally run into, which
subsequently are prone to failure.

Five years usage and the unit was never turned off, at least until the
condition osculated and a heat-sensor disabled the channel with higher
temperatures. Averages out to nickel, dime a day, or put another
couple on the jukebox, unless compared to another of my Class A/B amps
that has seen 10-times the usage of the ART.

And so I've a Class D replacement slated, hopefully, which will fill a
pro-grade bill, the caveat being for as little money as possible, or
to cost close enough to my outlay on the ART unit.

Class D being amps which can more or less respectably produce three
times the power, over a former class of exclusive Class A/B amps,
being Class D is now presented among serious technological
advancements and offerings.

And no doubt a wide one for characteristics between design intents.
Three times the power, which I'll have, equates to the common
assessment of a speaker at least twice more capable of handling that
amount. Which I have: a speaker cabinet rated for 600 watts. A
provision otherwise incredibly enough obtainable through the amp's
firmware display for setting the amp in bridged mode. 600 watts for
playing a bass guitar (from a DI impedance box) is not especially
incredible. I have a 6-string guitar that's much bigger and uses huge
strings. Other than being a guitar in all other respects, it's
nevertheless called a bass guitar.

I'll first have to turn on the new Class D amp. That will occur when
I take possession, which will serve a purpose of effectively never
turning it off. It idles at 18-watts, much as does a 52"
ceiling-mounted fan left on at the lowest blade rotational speed. Even
though the amp is equipped with a fan, it's Class D, and I don't
expect the fan to run at idle wattage or slightly higher.

Plugging in a bass guitar will be icing on the cake if it works as
intended: twenty-four hour, low-wattage duty for longevity;- a
relative occasional assessment for high-power usage. It's also an amp
with an old name, going back further, older than the abovementioned
amp, 10-times older than the failed ART amp.

In fact the manufacturer of the Class D would hold public
demonstrations to the strength of their amps by taking current from
the output leads to weld together metal. I've some doubts, having
used 100-watt vacuum tube amps for bass guitar, which accordingly are
humbled among higher-wattage bass-designed amps.

As I said, I'm out of it with today's Class A/B amps and the
accompanying heat to an A/B's duty cycle. The Class D will be
delivered and installed later today. The ART, being somewhat
beautifully designed both inside and out, I suspect I'll lean up
alongside a garbage can a little while for the contemporary sense of
nostalgia it brings.
  #2  
Old March 16th 18, 07:34 AM posted to alt.comp.hardware.pc-homebuilt
Flasherly[_2_]
external usenet poster
 
Posts: 2,048
Default Class ABDH & I

On Fri, 16 Mar 2018 02:01:13 -0400, Flasherly
wrote:

As I said, I'm out of it with today's Class A/B amps...

-
The Harman Drive Core amplifier chip is a completely in-house design
done through Crown engineering. The only thing we used TI for was
their expertise in IC Chip manufacturing. There are several patents on
the chip design, although the basic topology is a Class D output
stage. The Drive Core technology is used in several places, including
the Lexicon DD-8, and several Crown amplifiers. There are 2 chips, one
is a complete amp on a chip that includes an output stage that is
capable of delivering 75 - 150 watts into 8ohms (depending on power
supply and application requirements) and is table to 2 ohms, and the
only thing that is really needed is a power supply and an input stage.
The first use of the technology was in the Lexus LFA supercar. The
requirements were high output, small size, high efficiency (greater
then 90%), and great sound. Moving the input and output stages onto a
single IC allowed much tiger tolerances of the clock and triangle wave
form generator that is the heart of all digital amp designs, and often
the cause of the "Class D" sound some people don't like. There is also
a version that is everything without the high output stage (the input,
waveform generator, feedback circuit, etc...) that can me used to
drive higher output stages either Class D or our patented Class I,
where more then 150 watts is needed.

Thanks for the interest,
Todd Packer
Harman Luxury Audio Group
Field Application Engineer
  #3  
Old March 16th 18, 08:26 AM posted to alt.comp.hardware.pc-homebuilt
Paul[_26_]
external usenet poster
 
Posts: 766
Default Class ABDH

Flasherly wrote:
Don't make 'em to last. Supposed studio-grade ART amp, two models,
which I'm glad I didn't buy the more powerful of the two. It has a
characteristic output heat difference: one channel's output
transformers are hotter than the other. I noticed the heat
discrepancy from day one, when I first plugged the unit in. Very
basic sensory perceptions being not much more than a casual note, or
why else would not I have returned or at least replaced it with
another new unit. A perfectly respectable note from a repair or
technician's standpoint, to point out sequential serial production
models, any amp manufacturer may occasionally run into, which
subsequently are prone to failure.

Five years usage and the unit was never turned off, at least until the
condition osculated and a heat-sensor disabled the channel with higher
temperatures. Averages out to nickel, dime a day, or put another
couple on the jukebox, unless compared to another of my Class A/B amps
that has seen 10-times the usage of the ART.

And so I've a Class D replacement slated, hopefully, which will fill a
pro-grade bill, the caveat being for as little money as possible, or
to cost close enough to my outlay on the ART unit.

Class D being amps which can more or less respectably produce three
times the power, over a former class of exclusive Class A/B amps,
being Class D is now presented among serious technological
advancements and offerings.

And no doubt a wide one for characteristics between design intents.
Three times the power, which I'll have, equates to the common
assessment of a speaker at least twice more capable of handling that
amount. Which I have: a speaker cabinet rated for 600 watts. A
provision otherwise incredibly enough obtainable through the amp's
firmware display for setting the amp in bridged mode. 600 watts for
playing a bass guitar (from a DI impedance box) is not especially
incredible. I have a 6-string guitar that's much bigger and uses huge
strings. Other than being a guitar in all other respects, it's
nevertheless called a bass guitar.

I'll first have to turn on the new Class D amp. That will occur when
I take possession, which will serve a purpose of effectively never
turning it off. It idles at 18-watts, much as does a 52"
ceiling-mounted fan left on at the lowest blade rotational speed. Even
though the amp is equipped with a fan, it's Class D, and I don't
expect the fan to run at idle wattage or slightly higher.

Plugging in a bass guitar will be icing on the cake if it works as
intended: twenty-four hour, low-wattage duty for longevity;- a
relative occasional assessment for high-power usage. It's also an amp
with an old name, going back further, older than the abovementioned
amp, 10-times older than the failed ART amp.

In fact the manufacturer of the Class D would hold public
demonstrations to the strength of their amps by taking current from
the output leads to weld together metal. I've some doubts, having
used 100-watt vacuum tube amps for bass guitar, which accordingly are
humbled among higher-wattage bass-designed amps.

As I said, I'm out of it with today's Class A/B amps and the
accompanying heat to an A/B's duty cycle. The Class D will be
delivered and installed later today. The ART, being somewhat
beautifully designed both inside and out, I suspect I'll lean up
alongside a garbage can a little while for the contemporary sense of
nostalgia it brings.


On basic power transformers (not output transformers),
a power transformer can overheat with no load whatsoever.
I have such a transformer here, which I had just put into a
home amplifier design, which overheated. Just plugging
in the transformer with no load, it was overheating.

This is caused by eddy current flow.

The laminations in a regular power transformer (AC 110V to some lower
AC output inside the equipment), those laminations are steel with a
lacquer coating. The laminations are then sandwiched together.

The purpose of the lacquer, is to prevent induced current flow
from one lamination plate into the next.

Now, as a transformer ages, or if a transformer is placed in a
moist atmosphere, the steel in the laminations can rust and
punch through the insulating coat. And when eddy currents flow
from one lamination to another. This represents energy loss
and consequent heating.

A second failure mode for power transformers, is a short in
some winding. Say there are multiple output windings, and an unused
winding (a low power one) is shorted out for some reason.
The transformer can overheat, with no apparent secondary side
usage.

*******

On output transformers, you don't want DC across them, as
first of all, DC saturates the transformer core and
prevents good passage of AC output. Transformers on output
may be used on vacuum tube units, for impedance conversion
purposes. A solid state design might not need them.

*******

You might have contacted after-sales support, technical
support, or warranty support when you received the
defective amplifier and asked them if the situation
was "normal" as far as they were concerned. There's
plenty of junk on the market operating at high
temperatures, such as the computer speaker 7.1 amplifiers
situated inside the sub housing, with no decent cooling for
any of the components. The air temperature inside the sub
is warm enough, to "cook" the glue used to provide
protection against vibrational failure. And the glue
happens to conduct, once it's been cooked and breaks
down chemically. The conductive glue then shorts out
the power used to run the amp and makes the amp unreliable.
All because cooling design was neglected.

Paul
  #4  
Old March 16th 18, 03:07 PM posted to alt.comp.hardware.pc-homebuilt
Flasherly[_2_]
external usenet poster
 
Posts: 2,048
Default Class ABDH

On Fri, 16 Mar 2018 04:26:50 -0400, Paul
wrote:

On basic power transformers (not output transformers),
a power transformer can overheat with no load whatsoever.
I have such a transformer here, which I had just put into a
home amplifier design, which overheated. Just plugging
in the transformer with no load, it was overheating.

This is caused by eddy current flow.

The laminations in a regular power transformer (AC 110V to some lower
AC output inside the equipment), those laminations are steel with a
lacquer coating. The laminations are then sandwiched together.

The purpose of the lacquer, is to prevent induced current flow
from one lamination plate into the next.

Now, as a transformer ages, or if a transformer is placed in a
moist atmosphere, the steel in the laminations can rust and
punch through the insulating coat. And when eddy currents flow
from one lamination to another. This represents energy loss
and consequent heating.

A second failure mode for power transformers, is a short in
some winding. Say there are multiple output windings, and an unused
winding (a low power one) is shorted out for some reason.
The transformer can overheat, with no apparent secondary side
usage.

*******

On output transformers, you don't want DC across them, as
first of all, DC saturates the transformer core and
prevents good passage of AC output. Transformers on output
may be used on vacuum tube units, for impedance conversion
purposes. A solid state design might not need them.

*******

You might have contacted after-sales support, technical
support, or warranty support when you received the
defective amplifier and asked them if the situation
was "normal" as far as they were concerned. There's
plenty of junk on the market operating at high
temperatures, such as the computer speaker 7.1 amplifiers
situated inside the sub housing, with no decent cooling for
any of the components. The air temperature inside the sub
is warm enough, to "cook" the glue used to provide
protection against vibrational failure. And the glue
happens to conduct, once it's been cooked and breaks
down chemically. The conductive glue then shorts out
the power used to run the amp and makes the amp unreliable.
All because cooling design was neglected.

Paul


The temperature discrepancies occur on the left side of the amp, and
may be easily felt from both hands placed on the heatsink fins. Facing
from the front the left side is always hotter, somewhat to the rear
side. There are four transistors directly mounted to the side
panel-heatsink assembly. Might correspond to the higher "left
channel" bias current.* And, yep, I lose the left channel, the orange
"clip" light faults to an on condition, shuts down. It works. I
even pulled the top case panel, but it still overheats at a left
hinksink near uncomfortably hot to touch. Eventually in a matter of
time, and this part of the year isn't anywhere near summertime hot
yet. One side note: I put a vacuum tube buffer preamp between a
mixer and input channels about a month ago:
- J61 classic tube design, optimization line.
Size: 95x100x32mm/3.7x4x1.3 inch
Power: DC12V 1A
Frequency Response: 20HZ (-0.2DB) ~ 20KHZ (-0.2DB)
SNR: 100DB Input Sensitivity: 300 ~ 2000MV
Output: 3000MV THD: 1000MV 0.1%

Should be immaterial. As I said the amp has been slightly, to now
definitely hotter from day one, from first unpacking the unit.
Yeppers...should'a but didn't contact tech;- highly, very, reviewed.
And then, sigh, who'd have expected. And only two years out of
warranty. So much for art and ART (Applied Research and Technology)
as defined in Rochester, New York. Now I know.

btw- side-by-sdie & its replacement
https://www.amazon.com/ART-SLA2-200W.../dp/B0009GWNOG


Ah, yes,...this is It...the good life, pictures, the beauty,
everything imaginable and hard-core...

* "These biasing current was found to be 47mA in the left channel and
32mA in the right channel. The input side to the darlington consists
of a complimentary pair made up of 2SC3421/2SA1358 devices (10W,
Vceo=120V, 1A, ft=120 MHz)."


http://gnu.295.ca/peak/audio/sla-1.html
1.3 SLA-1 Innards

The SLA-1 is based upon two large printed circuit boards to the left
and right of the centrally mounted toroidal transformer, a front panel
PCB and a small board behind the transformer used for the IEC
connector/fan regulator/ground lift switch.

The power supply and most of the weight is due to a centrally mounted
toroidal power supply with a center tapped 76V output (i.e. 38-0-38)
and a secondary 13V RMS output consisting of two green wires. This is
used to power fan section that gets a 1/2 way rectified DC 7808 8V
regulated DC. I can detect a faint hum coming from the transformer.
The full wave rectifier bridge (unmarked) is heatsinked to the left
channel...updating this to soft recovery types may be more difficult
unless one uses higher rated parts and no heat sinking. The main power
supply uses 4700 uF 63V (Metacon) units for the positive and negative
supply (mounted on left channel output board). These provide +/-50V
rails. For 100W output into 8 ohms, the outputs need to generate a 40V
peak. The input, volume section and pre-driver section are powered off
+/-15V derived from zener diodes off the +/-50V main DC supply.

The remaining 20 electrolytics (for each channel)are made by Tocon
(whom I have not heard of) consist of about 4 x 220uF units, 1 x 100uF
unit and a ton of 10uF 50V units. There are some green film units
(about four of them) are used in various parts of the amplifier with
values of 0.1uF and 0.001uF.

The 1/4 watt resistors are 5% units. Larger 1 watt units are found for
the 10 ohm stabilization network, 2 x 1 kohm unit, 2 x 470 ohm units,
a 100 ohm, and 2 x 47 ohm units, unit.



1.3.1 Input Stage

The quad op-amp Matsu****a AN6554 uses two of the units for left and
right channel in differential to single ended gain configuration
providing 3.52 dB gain (1.5x) for single ended inputs. The 14 pin
package uses pins 8,9 and 10 for the left channel and pins 5,6 and 7
for the right channel. A 22K and 33k feedback resistor set the gain
for this stage. A second pair of these is needed for handling the
balanced inputs. Two input DC blocking caps and and output cap
complete the circuit. The phono plugs TRS (tip ring sleeve) provide
IN+, IN- and ground connections for differential inputs. Single ended
Phono plugs will short IN- to the sleeve/ground and provide single
input via the TIP portion of the plug. Both the XLR and Phone plug
inputs provide for balanced inputs. It should be possible to flip the
phase of the amplifier by feeding a input to the "RING/IN-" input and
grounding the "TIP/IN+" to ground/sleeve.

1.3.2 Volume Control Section

The outputs from the input stage go to a 9 pin header and connect to
the front panel PCB. A third op-amp (of the four in the AN6554)
provides a Unity Gain buffer from the volume control before going to
amplifier section. The fourth op-amp is provide for phase inversion in
bridge mode.

1.3.3 Amplifer Section

The output stage is a complimentary Darlington configuration with
about 10% local feedback. The output side of the Darlington are two
pairs of 60 Mhz output transistors: 2SC2837 (NPN) and 2SA1186(PNP)
complimentary bipolar transistors are used for each channel and
arranged in common emitter configuration . These biasing current was
found to be 47mA in the left channel and 32mA in the right channel.
The input side to the darlington consists of a complimentary pair made
up of 2SC3421/2SA1358 devices (10W, Vceo=120V, 1A, ft=120 MHz).

This is driven by 1/2 of the 4558 opamp. Feedback components set the
gain to about 25 dB (18.3x). Signals coming in are both high and low
pass filtered. The output stage contains a classic zobel network to
stabilize the amplifier. There is no DC servo control so large caps
are needed to provide for high pass filter that limits the
amplification of subsonic signals.

A generic 812H relay provides a delayed connection to the speakers and
instantaneous disconnect to them during power on and power off ,
respectively. This means that there is not turn on transient or turn
off transient. The same relay disconnects the output in the event of
overheating and shorted outputs.A second sourced UPC1237HA chip is
used to sense when to open the relay breaker and protect the chip. One
is used per channel. Two small signal transistors (Q19 and Q20) are
50V/150mA 2SC945 NPN devices (ft=300Mhz) and 2SA1015 PNP devices(ft=80
Mhz) make up a current sense circuit to feed into pin 1 of the
protection IC. These general purpose transistors are also used near
the bottom of the left channel board and in the front panel board. My
guess is that they provide for compare functions for the green signal
LED, red clip LED and the overload LED.
  #5  
Old March 17th 18, 06:41 AM posted to alt.comp.hardware.pc-homebuilt
Flasherly[_2_]
external usenet poster
 
Posts: 2,048
Default Class ABDH & I

On Fri, 16 Mar 2018 03:34:23 -0400, Flasherly
wrote:

Todd Packer
Harman Luxury Audio Group
Field Application Engineer


Installed the Crown Class D.

Huge difference in engineering between Crown and ART. The ART is
engineered along its case as a massive heatsink with a 2-speed,
dinky-butted piece-of-junk fan for a decorative engineering
afterthought.

Dunno about promercial amps, QVS or Crown's approach similarly in a
Class A/B application models, but my new D Class series shows a wider
regard for Crown's approach to heat: Crown doesn't mess around, and
the outside casing is all about airflow and accountable
heat-dissipation.

Not that it necessarily need be, I'd imagine, being a Class D is
inherently cool. It's nonetheless still equipped with one big,
honkin' fan for cooling contingencies. That's cool for business
terminology, but what's cooler is the fan never need be run within
modest operational characteristics.

There's even firmware logic for a LCD to display sensors to the output
stage's operating heat. Also nifty, although I'd trade the whole LCD
shebang for a 50-year warranty in a minute.

Provisionally and traditionally from promerical grade. Whereas these
new Crown designs are also making headway into the A/V prosummer
circuit. Especially for those whom can't directly state to an
high-end Class A amp ownership, exactly why they really can, or
cannot, tell a difference between their Class D and a $5000 Class A
amplifier.

Or it may be just simpler with split encoded signals provided by
Hollywood entertainment, for those who like that sort of thing, to use
such as the amp's firmware, also provided, for bandpassing from a
low-shelf notch to appropriate dedicated speakers. Some might then
call it OK for mere low-frequency Class D operation. (Certainly less
bother with transients or Mid/Side, a likes to stereo signal encoding,
marginally absent in a lower frequency range.)

I can't go there. I know how the ART and I know now how the Crown
sounds. And that's good enough for me. After a few hours of music
listening, my soul may have been soothed. I somehow feel lighter now,
so much less dissatisfied with the ART, being it's out of sight,
stacked up next to the garbage can.
 




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