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Redesign of Carver's D-500 Amplifier under Phase Linear Corp

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Anonymous
December 25, 2004 9:56:15 AM

Archived from groups: rec.audio.tech (More info?)

I have owned my venerable Phase Linear D-500 amplifier since 1978. It was
the last amplifier that Bob Carver designed before he left the Phase Linear
Corporation to start his new business.

Over the years, I have done several maintenance items on this amplifier,
mostly related to re-capping. The majority of problems were due to
capacitors drying out on the board that controls the amplifier's functions.
I've replaced these over the years.

Just recently, the transistor that controls the latch circuit which powers
the main relay for switchings mains power to the large power transformer had
developed an intermittent breakdown where the amp would occasionally turn
itself on with no one pressing the front panel button. Since I didn't have
an MPSA42 on hand, I replaced with a 2N3440, with just as good as new
results.

Integrating this amp into my racks a number of years ago brought about a
problem: hum. The amp threw a lot of magnetic energy into everything made of
metal that was nearby. Especially with direct condution from the D-500
chassis to the rails of the rack.

I decided to redo my rack configuration this month in an attempt to fix the
problem by isolating low level systems from power systems. While I was at
it, I did a little bit of needed maintenance on several pieces of gear.

While inside the D-500, it occured to me what an awful job of engineering
went on as far as wiring and grounding topology was concerned. These guys
wired the amp in the most wasteful, noise-attracting way possible!

I found several wiring no-nos and gradually worked on fixing them. Before I
get to details, I should point out that this amp always showed a bit of
instability in the form of ultrasonic oscillation, when driven to clipping,
since it was bought new. (I love to put all my amps into dummy loads and put
a scope and signal generator on them to measure the real power output.)

Getting back to details now, I ended up cutting out about 60% of the wiring
lengths where B+/- voltages were running around the chassis. They had the
DC, AC and low level audio wiring bundled together. No wonder I would hear a
buzz when a light dimmer was turned part way on in the house. Every wire
went into one harness.

Even more unbelievable was the fact that the ground for the driver board and
audio inputs was taken off the negative terminal of the left and right
speaker outputs! No wonder I was measuring crosstalk garbage in the undriven
channel when the driven (other) channel was driven to clipping.

I proceeded to correct these deficiencies, observing the "star topology" of
grounding methods. I moved the driver board ground to the power supply
ground, at the junction of the two big capacitors. I unbundled all the leads
carrying AC, DC and audio and shortened the DC power leads by directly
routing them to the capacitors from the output stage. I shortened the ground
leads in the same manner.

The next thing I did was add a second 25 amp bridge rectifier to the power
supply. I ran separate parallel wiring from that to the Low/Hi Z relay and
parallel wiring to the +/- capacitor terminals.

At an earlier time, I had replaced the original electrolytic capacitors with
much larger 45,000uF capacitors. Recent research made me aware that the ESR
of electrolytics is not so good above 1000hz, so I added 4.4uf of poly
capacitors across each power supply rail, to improve the ESR at higher
frequencies.

I shortened the audio wiring from the rear apron, routing it directly to the
front panel, instead of letting it run parallel to 110 vac wiring in a
bundle. To cure a slight left channel hum, I ended up placing/gluing a strip
of copper clad PCB on the left edge of the driver PCB, right over the 5"
trace of unshielded audio input, grounding that strip to audio ground. That
quieted the left channel hum.

Over the course of these modifications, wiring was shortened, leads carrying
diverse signal types were segregated, and grounding was corrected so that
all systems share a star topology.

The result? The crosstalk between left and right channels is gone.
The amp doesn't oscillate when driven to clipping anymore.
The power supply is stiffer and doesn't sag under load.

Subjective impression? The noise is gone. Music emerges from a blanket of
silence. There seems to be a greater clarity and detail and the soundstage
is wide and deep. Transient response is crisp. The amp sounds better today
than it did when it was new.

In fact, now that I isolated the amp from the rest of the equipment by
insulating it from the rack rails electrically, the pervasive hum that
plagued me is gone to inaudible on my ultra-efficient speakers.

I'm sure there are other things I could further do to make subtle
measureable improvements, but the changes made so far have resulted in
pretty radical improvements. I'm quite surprised that Phase Linear would
design such marvelous circuit topology, but completely screw up the wiring
topology. But having corrected that, the true sheen of this amplifier is
realized.



--
Take care,

Mark & Mary Ann Weiss

VIDEO PRODUCTION . FILM SCANNING . DVD MASTERING . AUDIO RESTORATION

Business sites at:
www.dv-clips.com
www.mwcomms.com
www.adventuresinanimemusic.com
-

More about : redesign carver 500 amplifier phase linear corp

Anonymous
December 25, 2004 10:59:51 AM

Archived from groups: rec.audio.tech (More info?)

> I'm sure there are other things I could further do to make subtle
> measureable improvements, but the changes made so far have resulted in
> pretty radical improvements. I'm quite surprised that Phase Linear would
> design such marvelous circuit topology, but completely screw up the wiring
> topology. But having corrected that, the true sheen of this amplifier is
> realized.

The three most important factors affecting audio quality in electronics are
layout, layout and layout. The best topology, choice of transistors, ICs or
tubes don't matter if the layout stinks.
Anonymous
December 25, 2004 12:21:55 PM

Archived from groups: rec.audio.tech (More info?)

"Mark & Mary Ann Weiss" <mweissX294@earthlink.net> wrote in
news:ja8zd.988$qf5.529@newsread3.news.atl.earthlink.net:

> I have owned my venerable Phase Linear D-500 amplifier since 1978. It
> was the last amplifier that Bob Carver designed before he left the Phase
> Linear Corporation to start his new business.
>
> Over the years, I have done several maintenance items on this amplifier,
> mostly related to re-capping. The majority of problems were due to
> capacitors drying out on the board that controls the amplifier's
> functions. I've replaced these over the years.
>
> Just recently, the transistor that controls the latch circuit which
> powers the main relay for switchings mains power to the large power
> transformer had developed an intermittent breakdown where the amp would
> occasionally turn itself on with no one pressing the front panel button.
> Since I didn't have an MPSA42 on hand, I replaced with a 2N3440, with
> just as good as new results.
>
> Integrating this amp into my racks a number of years ago brought about a
> problem: hum. The amp threw a lot of magnetic energy into everything
> made of metal that was nearby. Especially with direct condution from the
> D-500 chassis to the rails of the rack.
>
> I decided to redo my rack configuration this month in an attempt to fix
> the problem by isolating low level systems from power systems. While I
> was at it, I did a little bit of needed maintenance on several pieces of
> gear.
>
> While inside the D-500, it occured to me what an awful job of
> engineering went on as far as wiring and grounding topology was
> concerned. These guys wired the amp in the most wasteful,
> noise-attracting way possible!
>
> I found several wiring no-nos and gradually worked on fixing them.
> Before I get to details, I should point out that this amp always showed
> a bit of instability in the form of ultrasonic oscillation, when driven
> to clipping, since it was bought new. (I love to put all my amps into
> dummy loads and put a scope and signal generator on them to measure the
> real power output.)
>
> Getting back to details now, I ended up cutting out about 60% of the
> wiring lengths where B+/- voltages were running around the chassis. They
> had the DC, AC and low level audio wiring bundled together. No wonder I
> would hear a buzz when a light dimmer was turned part way on in the
> house. Every wire went into one harness.
>
> Even more unbelievable was the fact that the ground for the driver board
> and audio inputs was taken off the negative terminal of the left and
> right speaker outputs! No wonder I was measuring crosstalk garbage in
> the undriven channel when the driven (other) channel was driven to
> clipping.
>
> I proceeded to correct these deficiencies, observing the "star topology"
> of grounding methods. I moved the driver board ground to the power
> supply ground, at the junction of the two big capacitors. I unbundled
> all the leads carrying AC, DC and audio and shortened the DC power leads
> by directly routing them to the capacitors from the output stage. I
> shortened the ground leads in the same manner.
>
> The next thing I did was add a second 25 amp bridge rectifier to the
> power supply. I ran separate parallel wiring from that to the Low/Hi Z
> relay and parallel wiring to the +/- capacitor terminals.
>
> At an earlier time, I had replaced the original electrolytic capacitors
> with much larger 45,000uF capacitors. Recent research made me aware that
> the ESR of electrolytics is not so good above 1000hz, so I added 4.4uf
> of poly capacitors across each power supply rail, to improve the ESR at
> higher frequencies.
>
> I shortened the audio wiring from the rear apron, routing it directly to
> the front panel, instead of letting it run parallel to 110 vac wiring in
> a bundle. To cure a slight left channel hum, I ended up placing/gluing a
> strip of copper clad PCB on the left edge of the driver PCB, right over
> the 5" trace of unshielded audio input, grounding that strip to audio
> ground. That quieted the left channel hum.
>
> Over the course of these modifications, wiring was shortened, leads
> carrying diverse signal types were segregated, and grounding was
> corrected so that all systems share a star topology.
>
> The result? The crosstalk between left and right channels is gone.
> The amp doesn't oscillate when driven to clipping anymore.
> The power supply is stiffer and doesn't sag under load.
>
> Subjective impression? The noise is gone. Music emerges from a blanket
> of silence. There seems to be a greater clarity and detail and the
> soundstage is wide and deep. Transient response is crisp. The amp sounds
> better today than it did when it was new.
>
> In fact, now that I isolated the amp from the rest of the equipment by
> insulating it from the rack rails electrically, the pervasive hum that
> plagued me is gone to inaudible on my ultra-efficient speakers.
>
> I'm sure there are other things I could further do to make subtle
> measureable improvements, but the changes made so far have resulted in
> pretty radical improvements. I'm quite surprised that Phase Linear would
> design such marvelous circuit topology, but completely screw up the
> wiring topology. But having corrected that, the true sheen of this
> amplifier is realized.
>
>
>
> --
> Take care,
>
> Mark & Mary Ann Weiss
>

Good job on the amp!

I recently re-worked the 2 MC2500 amps that I have. There was one
"mistake" they made with those amps and that was to run the 120VAC line
for the fans too close to the inputs. Re-dressing the leads lowered the
hum/buzz to inaudible. Noise floor is now a respectable 100db down or
more. I could have worked at lowering it more, but there is no point.
Inaudible is inaudible after all.

r


--
Nothing beats the bandwidth of a station wagon filled with DLT tapes.
Anonymous
December 25, 2004 7:07:46 PM

Archived from groups: rec.audio.tech (More info?)

Karl Uppiano wrote:

> > I'm sure there are other things I could further do to make subtle
> > measureable improvements, but the changes made so far have resulted
in
> > pretty radical improvements. I'm quite surprised that Phase Linear
would
> > design such marvelous circuit topology, but completely screw up the
wiring
> > topology.

As a rule, it costs little or nothing to do the wiring layout *right*.

> The three most important factors affecting audio quality in
electronics are
> layout, layout and layout.

OK, hyperbole.

> The best topology, choice of transistors, ICs or tubes don't matter
if the layout stinks.

Conversely, the layout doesn't matter if there's something
significantly wrong with the other choices.
December 25, 2004 9:52:21 PM

Archived from groups: rec.audio.tech (More info?)

On Sat, 25 Dec 2004 07:59:51 GMT, "Karl Uppiano"
<karl.uppiano@verizon.net> wrote:

>
>> I'm sure there are other things I could further do to make subtle
>> measureable improvements, but the changes made so far have resulted in
>> pretty radical improvements. I'm quite surprised that Phase Linear would
>> design such marvelous circuit topology, but completely screw up the wiring
>> topology. But having corrected that, the true sheen of this amplifier is
>> realized.
>
>The three most important factors affecting audio quality in electronics are
>layout, layout and layout. The best topology, choice of transistors, ICs or
>tubes don't matter if the layout stinks.

Well that's a bit one-eyed. Layout is certainly important to a GOOD
design, and you certainly got that point across, but it's ALL got to
be good to get a good result, including topology, devices, and ... let
me see .. oh yes ... the design!

Tony (remove the "_" to reply by email)
Anonymous
December 25, 2004 9:52:22 PM

Archived from groups: rec.audio.tech (More info?)

"Tony" <tony_roe@tpg.com.au> wrote in message
news:gcaqs09d19f9nlatb879eiqucpl2glk03k@4ax.com...
> On Sat, 25 Dec 2004 07:59:51 GMT, "Karl Uppiano"
> <karl.uppiano@verizon.net> wrote:
>
>>
>>> I'm sure there are other things I could further do to make subtle
>>> measureable improvements, but the changes made so far have resulted in
>>> pretty radical improvements. I'm quite surprised that Phase Linear would
>>> design such marvelous circuit topology, but completely screw up the
>>> wiring
>>> topology. But having corrected that, the true sheen of this amplifier is
>>> realized.
>>
>>The three most important factors affecting audio quality in electronics
>>are
>>layout, layout and layout. The best topology, choice of transistors, ICs
>>or
>>tubes don't matter if the layout stinks.
>
> Well that's a bit one-eyed. Layout is certainly important to a GOOD
> design, and you certainly got that point across, but it's ALL got to
> be good to get a good result, including topology, devices, and ... let
> me see .. oh yes ... the design!

You'll get no argument from me. It was hyperbolic. But layout gets short
shrift all to often from vendors that should know better. My post was a
parody of the real-estate "location, location, location" mantra. Obviously,
a tar paper lean-to won't be a good investment, regardless of the location.
December 26, 2004 12:03:31 PM

Archived from groups: rec.audio.tech (More info?)

On Sat, 25 Dec 2004 09:36:53 GMT, "Karl Uppiano"
<karl.uppiano@verizon.net> wrote:

>
>"Tony" <tony_roe@tpg.com.au> wrote in message
>news:gcaqs09d19f9nlatb879eiqucpl2glk03k@4ax.com...
>> On Sat, 25 Dec 2004 07:59:51 GMT, "Karl Uppiano"
>> <karl.uppiano@verizon.net> wrote:
>>
>>>
>>>> I'm sure there are other things I could further do to make subtle
>>>> measureable improvements, but the changes made so far have resulted in
>>>> pretty radical improvements. I'm quite surprised that Phase Linear would
>>>> design such marvelous circuit topology, but completely screw up the
>>>> wiring
>>>> topology. But having corrected that, the true sheen of this amplifier is
>>>> realized.
>>>
>>>The three most important factors affecting audio quality in electronics
>>>are
>>>layout, layout and layout. The best topology, choice of transistors, ICs
>>>or
>>>tubes don't matter if the layout stinks.
>>
>> Well that's a bit one-eyed. Layout is certainly important to a GOOD
>> design, and you certainly got that point across, but it's ALL got to
>> be good to get a good result, including topology, devices, and ... let
>> me see .. oh yes ... the design!
>
>You'll get no argument from me. It was hyperbolic. But layout gets short
>shrift all to often from vendors that should know better. My post was a
>parody of the real-estate "location, location, location" mantra. Obviously,
>a tar paper lean-to won't be a good investment, regardless of the location.

Sorry - I was a bit slow on the uptake there. But a tar paper lean-to?
that's another matter, probably a great investment, and won't cost
much to knock down.

Tony (remove the "_" to reply by email)
Anonymous
December 26, 2004 9:40:05 PM

Archived from groups: rec.audio.tech (More info?)

On Sat, 25 Dec 2004 06:56:15 GMT, "Mark & Mary Ann Weiss"
<mweissX294@earthlink.net> wrote:

>I have owned my venerable Phase Linear D-500 amplifier since 1978 <snip>

And nothing's burned up?? Amazing!

>the last amplifier that Bob Carver designed before he left the Phase Linear
>Corporation to start his new business. <snip>

You mean "fired."

>Over the years, I have done several maintenance items on this amplifier,
>mostly related to re-capping. The majority of problems were due to
>capacitors drying out on the board that controls the amplifier's functions.
>I've replaced these over the years. <snip>

"Flames In-Yer-Ear" amps were famous for Carver's idiotic unmatched
outputs. The 700B was known for torching many clubs and other venues
by having the overheated outputs go to Vcc and set the woofer of
whatever it was driving on fire, and so was the D-500.

Boat anchors to which Bob the Slob should have been tied to long ago
before being dumped in the bay.

dB
Anonymous
December 27, 2004 12:12:12 PM

Archived from groups: rec.audio.tech (More info?)

> Good job on the amp!
>
> I recently re-worked the 2 MC2500 amps that I have. There was one
> "mistake" they made with those amps and that was to run the 120VAC line
> for the fans too close to the inputs. Re-dressing the leads lowered the
> hum/buzz to inaudible. Noise floor is now a respectable 100db down or
> more. I could have worked at lowering it more, but there is no point.
> Inaudible is inaudible after all.
>
> r


I was on a mission to eliminate hum, being the speaker systems in use have a
105dB @1W sensitivity rating. Even the smallest hum becomes room-filling on
these speakers.
As I got into the D-500, I discovered a lot of things the just irritated me
and that I could not leave be. So I ended up spending two nights rewiring
it.
The problem with this amplifier is the power transformer--it's humungous and
radiates 60 cycle magnetic fields that a dynamic microphone can pick up from
5' away. Isolating it from the rack was the final solution. I modified the
rack handle mounting, changing from the 1/4 20 pan head screws to flat head
recessed screws, after using a countersinking bit to create the recess in
the back of the flange and part of the 1/8" thick front panel. Then I
applied a 1/16" rubber adhesive strip to the back side and used insulated
washers on the 10-32 screws that secure it to the rails.
For twenty years (1984 was the year I expanded my studio and moved the
equipment to racks) I endured that hum and now to be finally free of it is a
wonderful thing. Hum and hiss are down around 10dBa now, about 30dB down
from where they were.

While I was in the mood, I also reworked the passive network filters that
cross from midrange drivers to tweeters. I replaced the 1st-order network
with a 2nd-order network, providing a much steeper rolloff below 4kc. The
goal here was to protect the tweeters from excessive excursions down around
1kc, since the D-500 can push significant power levels into the speakers in
the circuit with drive levels of many hundreds of watts possible at the
tweeters.

I'm very pleased with the results, and starting to find that my direct to
disc vinyl recordings sound more spacious and have better imaging that the
CD versions of the same performances that I possess. I can't wait to hear my
first 24/96 digital recording of a local symphony orchestra. I expect that
such resolution should provide the spaciousness and imaging that my 16-bit
CDs seem to lack.


--
Take care,

Mark & Mary Ann Weiss

VIDEO PRODUCTION • FILM SCANNING • DVD MASTERING • AUDIO RESTORATION

Business sites at:
www.dv-clips.com
www.mwcomms.com
www.adventuresinanimemusic.com
-
Anonymous
December 27, 2004 12:18:38 PM

Archived from groups: rec.audio.tech (More info?)

> >I have owned my venerable Phase Linear D-500 amplifier since 1978 <snip>
>
> And nothing's burned up?? Amazing!

I look inside that amp, and it scares me, every time. And that is coming
from a guy who regularly pokes his head inside 50kW FM broadcast
transmitters as part of my day job! I keep hoping that nothing ever goes
wrong in there, as the consequences could be very unpleasant.


> >the last amplifier that Bob Carver designed before he left the Phase
Linear
> >Corporation to start his new business. <snip>
>
> You mean "fired."

I hadn't heard that. If that be the case, it had to be a personality clash,
not a performance issue. Bob is a very intelligent and creative engineer.
His products are nothing short of stunning, albeit he shortcuts on the
quality of components, such as switches.


> >Over the years, I have done several maintenance items on this amplifier,
> >mostly related to re-capping. The majority of problems were due to
> >capacitors drying out on the board that controls the amplifier's
functions.
> >I've replaced these over the years. <snip>
>
> "Flames In-Yer-Ear" amps were famous for Carver's idiotic unmatched
> outputs. The 700B was known for torching many clubs and other venues
> by having the overheated outputs go to Vcc and set the woofer of
> whatever it was driving on fire, and so was the D-500.

I've had woofers catch on fire, but not from amp failure--but from
overdriving them. I remember a repair ticket for a non-warranty repair that
Electro-Voice did on an 18B low frequency driver saying, "voice coil burnt
BLACK". :-)
In practice, the D-500 has run cool and the worst that has happened was the
LOW Z setting would be tripped. The protection circuitry is far too
sensitive.


> Boat anchors to which Bob the Slob should have been tied to long ago
> before being dumped in the bay.
>
> dB

I think that's a bit harsh. He may not be such a great businessman, and
perhaps you've had a bad experience with one of his amps, but overall, I
think the man's a genius.


--
Take care,

Mark & Mary Ann Weiss

VIDEO PRODUCTION . FILM SCANNING . DVD MASTERING . AUDIO RESTORATION

Business sites at:
www.dv-clips.com
www.mwcomms.com
www.adventuresinanimemusic.com
-
Anonymous
December 27, 2004 3:40:53 PM

Archived from groups: rec.audio.tech (More info?)

"Mark & Mary Ann Weiss" <mweissX294@earthlink.net> wrote in
news:MlQzd.3874$qf5.2637@newsread3.news.atl.earthlink.net:

>
>
> I was on a mission to eliminate hum, being the speaker systems in use
> have a 105dB @1W sensitivity rating. Even the smallest hum becomes
> room-filling on these speakers.
> As I got into the D-500, I discovered a lot of things the just irritated
> me and that I could not leave be. So I ended up spending two nights
> rewiring it.
> Mark & Mary Ann Weiss
>

500 watts into a a speaker with 105 db @1watt sensitivity? That is a bit
much even for me! (:>) Doesn't that comes to about 132db at 512 watts?

You are fortunate that the transformer mechanical hum issue was able to be
addressed with mounting changes. Many times the transformer itself hums
and there is no recourse but to replace the transformer or the amp.

r




--
Nothing beats the bandwidth of a station wagon filled with DLT tapes.
Anonymous
December 27, 2004 5:16:22 PM

Archived from groups: rec.audio.tech (More info?)

DeserTBoB wrote:
>
> "Flames In-Yer-Ear" amps were famous for Carver's idiotic unmatched
> outputs. The 700B was known for torching many clubs and other venues
> by having the overheated outputs go to Vcc and set the woofer of
> whatever it was driving on fire, and so was the D-500.
>
> Boat anchors to which Bob the Slob should have been tied to long ago
> before being dumped in the bay.

It sounds to me like these clubs of legend were driving an amp hard
without properly ventilating them, so any fires or problems resulting
from failure due to overheating would seem to be more the fault of the
club rather than the amplifier or its designer. The owner's manual does
have a mention of 'adequate ventilation.'

I speak from experience. I worked for a touring sound company that used
Phase Linear 200's, 400's and 700's exclusively into the 90's. Yes, we
had amps fail but rarely in the manner of the 'Flame Linear' legend,
more due to thin sheet metal chassis coming apart because they weren't
designed for touring use or stagehands pushing transistor covers onto
transistors between the fins of heat sinks and causing shorts or bad
power blowing fuses. With about 35 Phase Linear amps we'd have maybe
four channel failures a year due to causes not related to operator
error, and we worked 'em hard. We had many more problems related to
band engineers who associated distortion with loudness and stagehands
who think they're airline baggage handlers. Amps these days are loaded
with protection circuits the PL's didn't have and designers have much
better simulation tools available, Carver did an excellent job given the
era he did it in.

We'd modified them to some extent, putting in B+/B- fuses on the front
panel for each channel, unbolting the transformer from the chassis and
bolting it to the rack, installing a support for the supply filter caps,
adding 1/4" connectors in place of the RCA's, putting fans and vents in
the racks. They were reliable workhorses that gave us few problems.
Considering their peers (other big amps available in the late 70's) if
you were smarter than the amp (a lot to ask, I know) they were great.
Anonymous
December 28, 2004 12:58:55 AM

Archived from groups: rec.audio.tech (More info?)

Unless there are still patents applicable to this amp, perhaps someone
should do a kit for DIY duplication-what's Carver going to do, it's a
1978 design. Or even a good DIY article.

Personally I like to build tube amps, but a good Class B solid state
design available (besides Randy Slone's Doug Self clone) to DIYers
would be good for the guy wanting it for 'pro' sound, MI, or maybe a
ham wanting to build a plate modulated AM rig-or maybe even a not for
profit broadcaster wanting to convert, say, a Harris BC-1 to solid
state mod.
Anonymous
December 28, 2004 4:36:40 AM

Archived from groups: rec.audio.tech (More info?)

>
> It sounds to me like these clubs of legend were driving an amp hard
> without properly ventilating them, so any fires or problems resulting
> from failure due to overheating would seem to be more the fault of the
> club rather than the amplifier or its designer. The owner's manual does
> have a mention of 'adequate ventilation.'

With Series Two came cooler running temp. The old 700b was a hot box, in
comparison.
I've never had the fan come on during 8-ohm use. Only during <3-ohm use
(three 8-ohm woofers in parallel, per channel.)


> I speak from experience. I worked for a touring sound company that used
> Phase Linear 200's, 400's and 700's exclusively into the 90's. Yes, we
> had amps fail but rarely in the manner of the 'Flame Linear' legend,
> more due to thin sheet metal chassis coming apart because they weren't
> designed for touring use or stagehands pushing transistor covers onto
> transistors between the fins of heat sinks and causing shorts or bad
> power blowing fuses. With about 35 Phase Linear amps we'd have maybe
> four channel failures a year due to causes not related to operator
> error, and we worked 'em hard. We had many more problems related to
> band engineers who associated distortion with loudness and stagehands
> who think they're airline baggage handlers. Amps these days are loaded
> with protection circuits the PL's didn't have and designers have much
> better simulation tools available, Carver did an excellent job given the
> era he did it in.

The tricky part is that the D-500 is DC coupled from input to output (and
has zero measurable offset in the output--quite an achievement!) Use of
infrasonic filtering is strongly recommended. I used my D-500 to drive
midrange and high frequency bands nowadays.
To avoid clipping, a loudspeaker management system is a good idea, one with
a limiter and dynamic EQ.
The amp still sounds phenomenally-good today, and even better than in 1978,
because of improvements I've made to the wiring and power supplies.



> We'd modified them to some extent, putting in B+/B- fuses on the front
> panel for each channel, unbolting the transformer from the chassis and
> bolting it to the rack, installing a support for the supply filter caps,
> adding 1/4" connectors in place of the RCA's, putting fans and vents in
> the racks. They were reliable workhorses that gave us few problems.
> Considering their peers (other big amps available in the late 70's) if
> you were smarter than the amp (a lot to ask, I know) they were great.

Another great modification is to get rid of that limiter/clipper circuit in
the driver stage. Instant doubling of useable unclipped power into 8-ohms.
But beware your speakers. Unless it can stand being plugged directly into a
120 vac wall outlet, it's not a good idea to connect it to this amplifier.
:-)
The advent of 4" voice coils and ferrofluid coolants do wonders for midrange
and tweeter drivers, which are capable of amazing SPL levels when coupled
with the D-500.


--
Take care,

Mark & Mary Ann Weiss

VIDEO PRODUCTION . FILM SCANNING . DVD MASTERING . AUDIO RESTORATION

Business sites at:
www.dv-clips.com
www.mwcomms.com
www.adventuresinanimemusic.com
-
Anonymous
December 28, 2004 1:07:24 PM

Archived from groups: rec.audio.tech (More info?)

Mark & Mary Ann Weiss wrote:

> And yes, I wanted unclipped reproduction at levels exceeding 130dB.

To solve what problem?

> dual woofer array. I once did a pink noise test with 2 v RMS reading at the
> speaker connection terminals using an HP 400E RMS voltmeter and took SPL
> readings of 112dB at 4'.

I hope you used ear protection.


Kind regards

Peter Larsen

--
*******************************************
* My site is at: http://www.muyiovatki.dk *
*******************************************
Anonymous
December 29, 2004 1:48:07 AM

Archived from groups: rec.audio.tech (More info?)

> > And yes, I wanted unclipped reproduction at levels exceeding 130dB.
>
> To solve what problem?

Realistic reproduction of anything that I choose to play, whether it be
fireworks, or a loud rock concert, or the cannon shots in Telarc's "1812"
Overture.
Not many people are acutely aware of the fact that not only can you feel
bass frequencies, but you can also feel midrange frequencies, if they are
loud enough. Listening with earplugs is quite a different experience, with
sound coming into the ear via bone conduction.
It's a personal fettish with me, hence, a friend coined a title "Bass Pig"
for me in 1989, because of the fourteen 18" woofers in the system.


> > dual woofer array. I once did a pink noise test with 2 v RMS reading at
the
> > speaker connection terminals using an HP 400E RMS voltmeter and took SPL
> > readings of 112dB at 4'.
>
> I hope you used ear protection.
>
>
> Kind regards
>
> Peter Larsen

Certainly, when testing in the sensitive portion of the hearing range. The
concern becomes more complicated for frequencies below 20 hertz, as ear
protection alone is not enough. But the sensitivity testing was what I
consider low level and short duration. Certainly, great care is taken when
choosing programming and when testing, especially in the frequency ranges
prone to causing ear damage, as the SPLs achievable can instantly do
permanent hearing damage.


--
Take care,

Mark & Mary Ann Weiss

VIDEO PRODUCTION . FILM SCANNING . DVD MASTERING . AUDIO RESTORATION

Business sites at:
www.dv-clips.com
www.mwcomms.com
www.adventuresinanimemusic.com
-
Anonymous
December 29, 2004 10:48:08 PM

Archived from groups: rec.audio.tech (More info?)

Mark & Mary Ann Weiss wrote:

> I await my chance to record a local symphony orchestra with my MOTU
896 in
> beautiful 24/96 digital, with a -114dB noise floor. That should be
> interesting.

I take it that you haven't looked very carefully at the dynamic range
of live recordings. No matter what modern technology you use to record
, the dynamic range of the recording is not so much limited by the
recording technology, as things like the background noise level of the
room, and the spurious human noises made by large numbers of humans
playing musical instruments and listening to the same.
Anonymous
December 30, 2004 2:28:07 AM

Archived from groups: rec.audio.tech (More info?)

"Mark & Mary Ann Weiss" <mweissX294@earthlink.net> wrote in
news:HolAd.5912$qf5.333@newsread3.news.atl.earthlink.net:

>
>> > And yes, I wanted unclipped reproduction at levels exceeding 130dB.
>>
>> To solve what problem?
>
> Realistic reproduction of anything that I choose to play, whether it be
> fireworks, or a loud rock concert, or the cannon shots in Telarc's
> "1812" Overture.
> Not many people are acutely aware of the fact that not only can you feel
> bass frequencies, but you can also feel midrange frequencies, if they
> are loud enough. Listening with earplugs is quite a different
> experience, with sound coming into the ear via bone conduction.
> It's a personal fettish with me, hence, a friend coined a title "Bass
> Pig" for me in 1989, because of the fourteen 18" woofers in the system.
>
>
>> > dual woofer array. I once did a pink noise test with 2 v RMS reading
>> > at
> the
>> > speaker connection terminals using an HP 400E RMS voltmeter and took
>> > SPL readings of 112dB at 4'.
>>
>> I hope you used ear protection.
>>
>>
>> Kind regards
>>
>> Peter Larsen
>
> Certainly, when testing in the sensitive portion of the hearing range.
> The concern becomes more complicated for frequencies below 20 hertz, as
> ear protection alone is not enough. But the sensitivity testing was what
> I consider low level and short duration. Certainly, great care is taken
> when choosing programming and when testing, especially in the frequency
> ranges prone to causing ear damage, as the SPLs achievable can instantly
> do permanent hearing damage.
>
>
> --
> Take care,
>
> Mark & Mary Ann Weiss
>


And I thought I was pretty hard core with 500+ watts per channel into 87
db 1w/m sensitivity. I am still in the junior leagues apparantly.

My stuff gets loud enought to cause my ears to intermodulate. Had that
happen once at a concert featuring the Atlanta Symphony and Chorus.

r


--
Nothing beats the bandwidth of a station wagon filled with DLT tapes.
Anonymous
December 30, 2004 5:00:12 AM

Archived from groups: rec.audio.tech (More info?)

> And I thought I was pretty hard core with 500+ watts per channel into 87
> db 1w/m sensitivity. I am still in the junior leagues apparantly.
>
> My stuff gets loud enought to cause my ears to intermodulate. Had that
> happen once at a concert featuring the Atlanta Symphony and Chorus.
>
> r
>

Everyone has their tastes. Mine grew from pipe organs and living next to
neighbors who were a rock band. Also a help was a wealthy family friend who
had a penchant for very loud and clean sound reproduction. He owns a JBL
Paragon and a bunch of Cerwin-Vega speakers. I was never impressed with the
bass though. 'Couldn't find it in any commercially-made speakers, so I made
my own. Over the course of 20 years, I built ten different speaker setups,
in persuit of the ellusive "loud & accurate" sound. Horn-loaded systems
littered my basement for the first 15 years, stacks of Community horns and
drivers, hand-built folded horns of all sizes... never liked the sound. So I
ended up converting to all planar drivers and adding more of them and
carefully-selecting them. Thanks to a very patient owner of a sound
equipment shop in the state, I was able to try and exchange a variety of
drivers, enabling me to make A/B/C comparisons of tweeters, midrange drivers
and woofers. I separated the hype from the performance and picked what did
the job for my purposes. By 1984, I had assembled, what has remained my
'ultimate' sound system. And when digital music came along, it sounded even
more dynamic. Right now, my ultimate listening experience comes directly off
my musical instruments--bypassing the recording studios and the compression
to 16-bit digital CDs. A bunch of Kurzweil sampler/synthesizers, direct into
the sound system... no compression, no rolloff on the bass, no lost impact.
Ooooh, what an experience. :-)
I await my chance to record a local symphony orchestra with my MOTU 896 in
beautiful 24/96 digital, with a -114dB noise floor. That should be
interesting.


--
Take care,

Mark & Mary Ann Weiss

VIDEO PRODUCTION • FILM SCANNING • DVD MASTERING • AUDIO RESTORATION

Business sites at:
www.dv-clips.com
www.mwcomms.com
www.adventuresinanimemusic.com
-
Anonymous
December 31, 2004 5:55:16 AM

Archived from groups: rec.audio.tech (More info?)

"Arny Krueger" <arnyk@comcast.net> wrote in message
news:1104378488.343028.4960@f14g2000cwb.googlegroups.com...
>
> Mark & Mary Ann Weiss wrote:
>
> > I await my chance to record a local symphony orchestra with my MOTU
> 896 in
> > beautiful 24/96 digital, with a -114dB noise floor. That should be
> > interesting.
>
> I take it that you haven't looked very carefully at the dynamic range
> of live recordings. No matter what modern technology you use to record
> , the dynamic range of the recording is not so much limited by the
> recording technology, as things like the background noise level of the
> room, and the spurious human noises made by large numbers of humans
> playing musical instruments and listening to the same.
>


Some venues are pretty quiet, and in between the crowd coughs, rustles and
other noises, I can hear the hiss of the mixing equipment used in a lot of
recordings. Worse than that, there has been an increasing trend toward using
dynamic compression on digital recordings, ruining the impact of the
original performance.
I recently did a 5.1 channel DVD of a cultural event, and despite the HVAC
rumble, I had a palpable sense of "being there" because nothing came between
me and the sounds of the event.


--
Take care,

Mark & Mary Ann Weiss

VIDEO PRODUCTION . FILM SCANNING . DVD MASTERING . AUDIO RESTORATION

Business sites at:
www.dv-clips.com
www.mwcomms.com
www.adventuresinanimemusic.com
-
Anonymous
December 31, 2004 10:39:54 PM

Archived from groups: rec.audio.tech (More info?)

"Mark & Mary Ann Weiss" <mweissX294@earthlink.net> wrote in news:MiJAd.2353
$JC2.81@newsread2.news.atl.earthlink.net:


> I await my chance to record a local symphony orchestra with my MOTU 896 in
> beautiful 24/96 digital, with a -114dB noise floor. That should be
> interesting.
>
>
> --
> Take care,
>
> Mark & Mary Ann Weiss
>


I would love to have a recording like that. When are you going to make the
recording?


r
Anonymous
January 1, 2005 9:09:38 AM

Archived from groups: rec.audio.tech (More info?)

> > I await my chance to record a local symphony orchestra with my MOTU 896
in
> > beautiful 24/96 digital, with a -114dB noise floor. That should be
> > interesting.
> >
> >
> > --
> > Take care,
> >
> > Mark & Mary Ann Weiss
> >
>
>
> I would love to have a recording like that. When are you going to make
the
> recording?
>
>
> r

I'm still waiting for approval from the orchestra chair. Could be sometime
this spring, if things go as I would like. The staff likes the idea of a
promotional video with 5.1 ch surround sound, but as with any professional
orchestra, there are legal issues that have to be sorted out carefully
first.
Maybe I'll try to get into recording some pipe organs in the meantime,
although there are few cathedrals around here with a real pipe organ, let
alone one with 32' pedal stops.


--
Take care,

Mark & Mary Ann Weiss

VIDEO PRODUCTION • FILM SCANNING • DVD MASTERING • AUDIO RESTORATION

Business sites at:
www.dv-clips.com
www.mwcomms.com
www.adventuresinanimemusic.com
-
Anonymous
January 20, 2005 3:25:34 AM

Archived from groups: rec.audio.tech (More info?)

Mark & Mary Ann Weiss wrote:

> I'm still waiting for approval from the orchestra chair.

Fewer people have to agree on a permission if you aim for chamber music
and the actual dynamic range may be larger than the one of a full
orchestra.

> Mark & Mary Ann Weiss


Kind regards

Peter Larsen


--
*******************************************
* My site is at: http://www.muyiovatki.dk *
*******************************************
Anonymous
January 20, 2005 8:28:41 AM

Archived from groups: rec.audio.tech (More info?)

Peter Larsen <SPAMSHIELD_plarsen@mail.tele.dk> wrote in
news:41EEEC6E.6ADCA143@mail.tele.dk:

> Mark & Mary Ann Weiss wrote:
>
>> I'm still waiting for approval from the orchestra chair.
>
> Fewer people have to agree on a permission if you aim for chamber music
> and the actual dynamic range may be larger than the one of a full
> orchestra.
>

That certainly does depend on program material. A Symphony could have a huge
dynamic range that would make a string quartet sound quite anemic. A few
pieces by Chabrier come to mind. There are many more of course.

r


--
Nothing beats the bandwidth of a station wagon filled with DLT tapes.
Anonymous
January 20, 2005 4:21:47 PM

Archived from groups: rec.audio.tech (More info?)

R wrote:

>> Fewer people have to agree on a permission if you aim
>> for chamber music and the actual dynamic range may be
>> larger than the one of a full orchestra.

> That certainly does depend on program material. A Symphony
> could have a huge dynamic range that would make a string
> quartet sound quite anemic.

First the general point: a chamber music event is able to contain near
silence, a symphone orchestra event is not, there are more clothes
rustling and people moving in chairs and more people on stage - and
usually also in the hall - breathing. The peak SPL - as seen from the
mic position - of a chamber music event is the peak SPL of a violin,
flute or concert grand, all of which can be quite loud, alternatively in
case of omni mics the peak SPL generated by the applause.

> A few pieces by Chabrier come to mind.

Or Takemitsu, or ... or ....

> There are many more of course.

On your second reading of my post you may notice the use of the wording
"could" rather than "will", this to allow for the exceptions.

Dynamic range per se is not about total loudness, it is about the
difference between audience holding their breath in expectative silence
after the sign from the concert master and the FFF. It takes unamplified
avantgarde jazzical to really beat chamber music in that regard.

> r


Kind regards

Peter Larsen


--
*******************************************
* My site is at: http://www.muyiovatki.dk *
*******************************************
Anonymous
March 11, 2005 12:25:04 PM

Archived from groups: rec.audio.tech (More info?)

> > I'm still waiting for approval from the orchestra chair.
>
> Fewer people have to agree on a permission if you aim for chamber music
> and the actual dynamic range may be larger than the one of a full
> orchestra.



While that's true, the circumstances are that I have a business relationship
in place with a particular symphony orchestra, and since I know of no
chamber music groups in the area, I'm working on the lead that I have.

Given the fact that the regional and local symphonies are starving, it would
seem in their best interest to get a promotional produced piece for
themselves.


--
Best Regards,

Mark A. Weiss, P.E.
www.mwcomms.com
-
!