Phase Linear Transistor Help!
Paul Neuhaus
transistors.
I have been unable to cross them to a replacement. Help! The transistors
, I believe were made by NEC, and are ; 2SB706A and 2SD746A.
I have been told they are "discontinued".
Any help would be GREATLY appreciated!
Thanks.
Paul Neuhaus
Email: U-...@ix.netcom.com
BOB URZ
NADA. The only thing special about these were the case style and 4 legs.
I am probably going to go with a contemporary 3 legged npn/pnp pair to
replace
the NEC's. Probably going to have to drill and tap the heat sink to make the
to-247 or so package fit.
Paul Neuhaus
I have found a source for the 2SB706A, BUT, there are only 4 in my amp
and the company that has them, (They bought it seems all the old
stock)Sayal in Ontario Canada, sells em for $7.50 each BUTthere is a
minimum $100.00 order. I just can't come around to by $100 dollars worth
of transistors to replace one bad one. I asked em if they would sell 4,
but stated it was there policy.
Paul
Cheuk-Fai Wong
US15 or CAN23/pc. plus shipping from Toronto, Ontario Canada.
According to my 1985 MJ magazine, they are rated at 180V, 10A, 200W
Paul Neuhaus wrote in message <375716...@ix.netcom.com>...
Illia Kuriakin
unreliable. They blew out too often and the factory took A YEAR
to fix them under warantee. Send your Phase Linear to the
junk dealer and get a Crown or other reputable amp. People
get Phase Linears to get the most Bang for the Buck, like
one watt per dollar, but if it dies on stage, you will wish
you paid two dollars per watt.
DUNCLIF
>So you need some of these notorious 4 legged beast too? I have been looking.
>NADA. The only thing special about these were the case style and 4 legs.
>I am probably going to go with a contemporary 3 legged npn/pnp pair to
>replace
>the NEC's. Probably going to have to drill and tap the heat sink to make the
>to-247 or so package fit.
>
Woops! Wronge case style. Disregard my post. My NEC manual is in Japanese
and I don't allways get it right. Pictures on the same page as the specs would
help.
BOB URZ
grandfather of all
modern day high power amps. They were originally built for high end home use,
but the
pro's used them because there was very little choice in them days! When the
original Phase 700 came out with 350watts/ch 8 ohms, there were no crowns, no
crests, no QSC or others to match it at the time. Yea, you could have had a
high power Crown Dc-300 at a whooping 150w/c. Give Phase its due, it was way
ahead of its time. If you treated them right and did not abuse them, They were
as good as anything else at the time. Many major tours used Phase in the early
days of high power touring sound.. If the early units had balanced XLR inputs
with proper rack mounts, an on/off switch, and fan cooling, you might still
see these units out on the road!
I own a 400II/3000 preamp and 5100 tuner I have had for 15+ years and they
have been just fine. Try to find something built like them now! Yes, today
there are many fine high power high current amps out there. Just remember who
invented the market for it.
I have toured with a national act. Anything at any given time can die a
untimely death.
I have seen power distro's blow smoke from the locals mis wiring the distro
(ever smell a burnt pile of mov's?) I have seen power amps blow smoke and
sparks like the forth of july. I have played the 2 minute drill when the
monitors went dead during a show.
Anything can die on the road. If you take care of it, it may live long enough
for a second
life on E-Bay!
BOB URZ
NSE
Mark Williams
for replacement purposes. These amps are notoriously unreliable and hard to
get parts for. Is there really no NTE or ECG cross for these? If not I
would seriously consider replacing them with something more available and
reliable.
I have done this for some amps which use the obsolete HPack packaged
transistors, and even converted them to MOSFET outputs on occasion. If you
have the schematic, it's not hard to figure out how to do this. The
advantage of MOSFETS is higher reliability, as they are free from the
failure mechanism that causes most bipolar outputs to fail: second
breakdown. This amp sure sounds like a good candidate for an upgrade. But
I'm sure you just want to get it on the air again with miniumum effort. I
will try to locate a reasonable cross that is available, tonight. Best of
luck.
BOB URZ
The circuit topology and the biasing are so different, you might as well start
from
scratch. As far as reliability goes, I replace hundreds of mosfets in car amps
every
year. More reliable? I doubt it. How common or how expensive are 180v 15 amp
power mosfets? Mosfets also have a much wider frequency response so they must be
compensated differently to prevent oscillation.
Yes, I agree on a suitable bi-polar output replacement. Minimum specs
180v breakdown and 15a or better. HFE probably 20/100.
The problem is having to drill the heat sink for the different transistor case
mount.
The NEC case style used in the original 300's have 4 legs and is different from
anything else currently around. It has been discontinued for quite a while.
I have found a few people who say they have a few of these. Will see if the
leads
pan out.
Why does everyone say these amps are so unreliable? I have had mine for 15+
years and still going strong! Abuse & stupidity are the #1 reason most of these
blow up! The one 300 I am working on is a customers. I find them no more
"unreliable" than the 2 or 3 year old major name japanese units I replace output
IC's in all the time!
If I were to vote for the most solidly built units of all time, there would be a
tie
with the early Marantz units with the "Gyro touch" tuning (22XX) series, and
the series II Phase Linear units. The stuff they build today may have good specs
and 400 buttons on the remote, but it looks like it was built in a yugo factory
inside!
(er, former bombed out yugo factory).
BOB URZ
NSE
Steven L. Bender
units, rated at 200V / 15A / 150W far as I know.
Might be almost the same if your numbers, except rated slightly higher or
lower in beta
or other aspect, which might not be relevant.
$15/per NEC 2SB705 and 2SD745 pair... or $55 for 4 pairs... or $150/12
pairs.
and $5 shipping.
--
Steven L. Bender, Designer of Vintage Audio Equipment
Amp Info Page: http://pages.prodigy.com/BUQU35D <-- Use Caps
"I think your analysis is basically correct, and the "white paper" is
excessively stained
with snake-oil and is of little use for anything other than starting fires
intended to
barbecue overzealous marketing departments." -Dave Platt
-**** Posted from RemarQ, http://www.remarq.com/?c ****-
Search and Read Usenet Discussions in your Browser
Mark Williams
> I find your remarks interesting, to say the least. Convert amps to Mosfets?
> The circuit topology and the biasing are so different, you might as well start
> from scratch.
Bob, the circuit "topology" is essentially the same. Bias has to go from the
typical 2.4V of Darlington emitter followers to about 7 volts for the mosfets I use
(the early lateral mosfets from Hitachi require less bias, but are almost obsolete
now because vertical mosfets are so much better/cheaper). If the amp uses a Vbe
multiplier for bias, it's a resistor change, period. If it's a diode string or
thermistor, you have to scratch your head but I have done this to a number of
amps. It's not a drop-in, but it's not rocket science either. A nice example of
such a conversion is posted on the net by Nelson Pass:
http://www.passlabs.com/citation.htm
> As far as reliability goes, I replace hundreds of mosfets in car amps
> every year. More reliable? I doubt it.
I understand that car amps get abused and blow outputs all the time. The type of
outputs does not matter in case of gross abuse. "In theory", if the amp is not
abused the mosfet outputs will be more reliable. Mosfets are essentially immune to
second breakdown, and they have a positive threshold voltage coefficient, so they
are immune to thermal runaway. A typical bipolar output stage is more vulnerable
because it is subject to both failure mechanisms. Mosfets are more expensive,
particularly P channel mosfets, by a factor of 1.5-2, but this is improving over
time.
Bob, I respect your experience. All of my work is with home audio amps, and I have
replaced hundreds of bipolar output transistors, but only one set of Mosfets (in a
rare Sony amp, which used Sony mosfets in an unusual topology!)
> How common or how expensive are 180v 15 amp power mosfets?
Extremely common. Cost is about double. There is tremendous R+D on Mosfets,
because they are the mainstay of switching power supplies now days. Bipolars are
not improving, but Mosfets get better/cheaper each year because they are essentially
integrated circuits and benefit from all the R+D on them.
> Mosfets also have a much wider frequency response so they must be compensated
> differently to prevent oscillation.
This is true, but an appropriate value of gate stopper resistor and the use of
ferrite beads on the gate lead will control the local oscillation tendency. A
bigger problem is that the transconductance of the output stage is much lower, by a
factor of 25. So the open loop gain of the amp is reduced by that factor. That
should require different compensation. Feedback stability must be analyzed. The
result is often that less compensation is needed (smaller Miller compensation cap on
the voltage amplifier stage).
> Yes, I agree on a suitable bi-polar output replacement. Minimum specs
> 180v breakdown and 15a or better. HFE probably 20/100.
> The problem is having to drill the heat sink for the different transistor case
> mount.
Depending on how hard it is to get at the heatsink, that could be a major effort. I
am not sure it is the same transistor die, but an identically rated NEC transistor
is the 2SA705 (not 706), which has a widely available cross (NTE93). This is also
an obsolete part though, the HPack plastic package has been largely superceded by
the TO3 BPL package for new designs.
> The NEC case style used in the original 300's have 4 legs and is different from
> anything else currently around. It has been discontinued for quite a while.
I plead ignorance. 4 legged transistors I have not seen, other than some ancient
PIC darlingtons in a TO-3 package.
I looked these parts up in my NTE reference, no cross, so I assume they are very
rare birds. The next time I am in Tokyo, I will check the Akihabara Electric Town
shops for a supply of these for my bench. They seem to have a few of everything
there; I was able to buy some of the obsolete Hitachi lateral mosfets in May there.
> Why does everyone say these amps are so unreliable? I have had mine for 15+
> years and still going strong! Abuse & stupidity are the #1 reason most of these
> blow up!
Bob, I have heard a lot of complaints about this amp, and its hard to find output
transistors, on the net. I have stayed away from Phase Linear because of their bad
rep. I suspect they will do fine if babied, but are marginal and cannot tolerate
abuse.
> The one 300 I am working on is a customers. I find them no more
> "unreliable" than the 2 or 3 year old major name japanese units I replace output
> IC's in all the time!
Agreed. I hate the hybrids, they are outrageously expensive and unreliable, not to
mention hard to find.
> If I were to vote for the most solidly built units of all time, there would be a
> tie with the early Marantz units with the "Gyro touch" tuning (22XX) series, and
> the series II Phase Linear units.
The Marantz units were very conservatively designed and rated, I too regard them
highly. These were far more reliable than the run of the mill amps of that era.
More modern gear is under terrific cost pressure; back then it was quality
pressure, trying to obliterate the US competitiion with cheap, excellent gear. Now
that the battle is won, the winners are in a cost war. Not surprising that quality
comes second.
Terry Demol
Mark Williams wrote in message <375C0262...@cup.hp.com>...
>BOB URZ wrote:
>I understand that car amps get abused and blow outputs all the time. The
type of
>outputs does not matter in case of gross abuse. "In theory", if the amp is
not
>abused the mosfet outputs will be more reliable. Mosfets are essentially
immune to
>second breakdown, and they have a positive threshold voltage coefficient,
so they
>are immune to thermal runaway. A typical bipolar output stage is more
vulnerable
>because it is subject to both failure mechanisms. Mosfets are more
expensive,
>particularly P channel mosfets, by a factor of 1.5-2, but this is improving
over
>time.
>
Sorry Mark, Mosfets have a negitive temperature coefficient at low
currents and a positive one at high currents.
I'm looking at my Harris power Mosfets book right now and every device
I see has a smaller VGS at higher temps up until very high currents.
These currents would be way outside normal operation for power amps.
>
>This is true, but an appropriate value of gate stopper resistor and the use
of
>ferrite beads on the gate lead will control the local oscillation tendency.
A
>bigger problem is that the transconductance of the output stage is much
lower, by a
>factor of 25. So the open loop gain of the amp is reduced by that factor.
That
>should require different compensation. Feedback stability must be
analyzed. The
>result is often that less compensation is needed (smaller Miller
compensation cap on
>the voltage amplifier stage).
Since the Mosfet is only a voltage driven device all the driver stage will
see
is capacitance. With bipolar especially hi current where betas are fairly
low there will be substantial current drive required.
The Mosfet topology could end up having higher open loop gain depending
on magnitude of capacitance.
Tez
Seanshine
> If I were to vote for the most solidly built units of all time, there would
>be a
>> tie with the early Marantz units with the "Gyro touch" tuning (22XX)
>series, and
>> the series II Phase Linear units.
>Mark Williams wrote
>The Marantz units were very conservatively designed and rated, I too regard
>them
>highly. These were far more reliable than the run of the mill amps of that
>era.
Gentlemen....thank you for confirming my faith in my old Marantz receiver model
2252b...bought it new and it still works...
I have a question though as to using it as part of a home theater setup.I
bought a sony sdp-e800 dd decoder....any suggestions on a good amp for the
other 3 channels(using the marantz for front left and right)? I have a Phast
plb-amp8 that i was using but the transformer went bad...
any help is greatly appreciated
Sean
Arny Krüger
BOB URZ wrote in message <37585C3B...@inetnebr.com>...
>I hate to burst your old "memories bubble", but phase linear was the
>grandfather of all modern day high power amps. They were originally
built for high end home use,
>but the pro's used them because there was very little choice in them
days! When the
>original Phase 700 came out with 350watts/ch 8 ohms, there were no
crowns, no
>crests, no QSC or others to match it at the time.
This had to do with those people having this obsession with making
reliable amps.
>Yea, you could have had a
>high power Crown Dc-300 at a whooping 150w/c. Give Phase its due, it
was way
>ahead of its time. If you treated them right and did not abuse them,
They were
>as good as anything else at the time. Many major tours used Phase in
the early
>days of high power touring sound.. If the early units had balanced
XLR inputs
>with proper rack mounts, an on/off switch, and fan cooling, you
might still
>see these units out on the road!
If dogs had wings, they could fly. You mentioned one key item for any
power amp: "output devices with sufficient SOA and bandwidth".
>I own a 400II/3000 preamp and 5100 tuner I have had for 15+ years
and they
>have been just fine. Try to find something built like them now! Yes,
today
>there are many fine high power high current amps out there. Just
remember who
>invented the market for it.
Crown, but in a strange way - with a power amp that was not a high
current amp, the original DC-300. Convinced everybody that an amp
with some current capacity would be a good idea - by negative
example. Phase Linear did their thing, and people added something to
the list - they decided they wanted something with high current AND
robustness.
Mark Williams
> >BOB URZ wrote:
>
> > If I were to vote for the most solidly built units of all time, there would
> >be a
> >> tie with the early Marantz units with the "Gyro touch" tuning (22XX)
> >series, and
> >> the series II Phase Linear units.
>
> >Mark Williams wrote
>
> >The Marantz units were very conservatively designed and rated, I too regard
> >them
> >highly. These were far more reliable than the run of the mill amps of that
> >era.
>
> Gentlemen....thank you for confirming my faith in my old Marantz receiver model
> 2252b...bought it new and it still works...
And it should keep working for a long time, it is a winner.
> I have a question though as to using it as part of a home theater setup.I
> bought a sony sdp-e800 dd decoder....any suggestions on a good amp for the
> other 3 channels(using the marantz for front left and right)?
You may want to consider more Marantz gear, their current single channel monoblocks
are well regarded today. Unfortunately there are no triple channel amps, but
plenty of quad Marantz amps were made in that brief period when quad was supposedly
the thing. That is another option. Or stack two stereo amps, just because they
are readily available. Marantz stereo 1060s are pretty common, and good amps for
their power range (a very conservative 30 wpc that is clean and sounds like more).
Good luck
Mark Williams
> Mark Williams wrote in message <375C0262...@cup.hp.com>...
> >... "In theory", if the amp is not abused the mosfet outputs will be more
> reliable. >Mosfets are essentially immune to second breakdown, and they have
> a positive >threshold voltage coefficient, so they are immune to thermal
> runaway. A typical >bipolar output stage is more vulnerable because it is
> subject to both failure >mechanisms. ....
>
> Sorry Mark, Mosfets have a negitive temperature coefficient at low
> currents and a positive one at high currents.
I simplified for the sake of clarity. You are correct; tempco varies from
negative at low currents (under 1 amp) positive at high currents, for some high
current N-channel mosfets (8 amp devices and up). This effect varies with the
device type. For the newer very high current N-channel devices, the crossover
is higher. For the devices I use the crossover is at about 1 amp. P channel
units seem to have a positive tempco at even low currents.
But it is positive at high currents, where runaway would occur. That is to say,
if the bias voltage is constant, the gate threshold will increase with
temperature (current drawn), causing a stabilization at some temperature
(current). With bipolar transistors, the negative tempco causes the current to
increase with temperature and demands a Vbias that has a negative tempco which
tracks the temperature of the output transistors.
The main point I was making is that Mosfet outputs are potentially more
reliable, since they are free of two nasty failure mechanisms:
1. second breakdown.
2. thermal runaway at high currents.
> I'm looking at my Harris power Mosfets book right now and every device
> I see has a smaller VGS at higher temps up until very high currents.
> These currents would be way outside normal operation for power amps.
Let's see, at 125 watts, 8 ohms the outputs deliver about 4 amps to the load.
While I rarely listen to music at this level, it is where failures would
occur. At this current, the mosfets I use have a positive tempco (as I said,
the crossover for devices I use is at 1 amp). At low currents, the heating
effects are non-destructive and no runaway occurs. But the data book for the
device you use should be the reference, and I understand that for very high
current devices the crossover is higher, so you should design accordingly.
> Since the Mosfet is only a voltage driven device all the driver stage will
> see is capacitance. With bipolar especially hi current where betas are fairly
> low there will be substantial current drive required.
> The Mosfet topology could end up having higher open loop gain depending
> on magnitude of capacitance.
I'll say it again, the transconductance of a power MOSFET is about 1/25 that of
a bipolar transistor, at 1 amp current and at low frequencies. It varies with
current and frequency. This is simply a device property, well known. I am not
overly fond of bipolar outputs, but they do have the advantage, clearly. It is
somewhat nullified by their rolloff of gain at high frequencies. In addition,
as you point out most bipolars have a falloff of gain at high currents (gain
droop); Mosfets don't.
Regarding current demands for driving MOSFETs, true the gates are a capacitive
load, but for the high current devices the capacitance is large (3400pF, varible
with gate voltage), and mosfets need substantial current drive to achieve fast
slew rates. For multiple paralleled output mosfets, some designers (Borbeley)
recommend 30-50 ma of current drive, on a par with bipolar drivers. I think
this is overkill, since I don't really see the need for the slew rates targeted,
with normal audio program material.
When I choose a device for the output stage, I consider many factors. I believe
the overriding concern should be reliability. I believe that second breakdown
is the major cause of failures of bipolar output transistors in normal operation
(except abuse). If you look at the actual curves of forward biased safe
operating area in data books, you see that bipolars typical 200volt, 15 amp
bipolars are very fragile at high voltage (above 100 volt) and even small
currents (50 ma.), due to second breakdown. For this reason really high
powered amps with bipolar outputs use paralleled cascode output stages, to halve
the Vce on each device. It gets them down to a safe area of operation, under
100 volts Vce, but requires 4 output transistors per leg, and these are usually
paralleled also. It makes a fairly complicated and lossy output stage, and
driver stage.
But a typical 200v, 12 amp complementary mosfet pair can easily replace such a
cascode quad, with potentially higher reliability for the reasons I mentioned.
Now there are many other considerations, and some designers will rate other
factors more heavily than I do (such as cost or long experience with bipolar
design). I can't fault that, but for my money I would almost always choose
mosfets.
Seanshine
never even thought of using an old quad amp..fantastic idea
Sean
>Mark Williams wrote
BOB URZ
what you know
now but they did not know then. Back then, you were lucky in pro sound if
you had a woofer that would handle 150 watts RMS. The ALtec 421, JBL D130
and others were good warriors in there day, but would be very obsolete
it this world now of 1kw woofers. There is a learning curve on any
product. What was the choice on high power/high voltage output
transistors 30 years ago? (and their bandwidth)
Did people think about SOA and other similar "safe" concepts back then
like they do now? NO. But they learned.
Phase linear got the market thinking on what it could or might be.
There was no pro sound market then like there was now. People were
adapting theater type system for the early touring systems. There was not
compact high power touring boxes or yamaha PMxx consoles, or racks of
heavy metal high current stable power amps.
People innovated and rolled their own. These systems would be a joke
today, but in
1970, they were state of the art (black art).
So, I stand by my statement. As far as Crown goes, yes they built a good
product.
I have seen DC-150's and 300 blow up also. They had there own quirks. Put
a 4 ohms load on a early one with out a fan and beat it and see how long
it lived! How many output devices did the crowns have? How much excess
power supply capacity was there? The Crown was built as a high end home
amp also. It was used in pro systems,
but it had some of the same weakness as the Phase because it was not
designed to be
a touring amp. Nobody knew what a touring amp was in those days? (or
should be)
Give Phase linear credit for high current power supplies, number of high
voltage output
devices per channel, watts/ch. (all relative to the times and
competition).
You would make fun of microsoft windows 1.0 also on how crude it was and
what it
should have been. You have to have a foundation to build any concept or
product on.
Phase had the balls to "go where no man has gone before".
Which brings us to were we are today. In pro sound land, we have
robustness and we
have high current 2 ohms amps. We have robust high voltage/ high current
outputs.
We have heavy rack mount style cases and custom high current toroid
transformers. We have class a -z type amplifiers (or so it seems). Today,
we still blow up amps. And many of these ultra output amps would not be
considered "high fidelity" in many circles.
We are in the early days of digital control & processing in pro sound.
Maybe in 20 years
we will laugh and say what we should have done differently in the 90's!
I would not want to go back to using 70's amps in a sound job I was
doing, but i WILL
keep my old Phase stuff at home and smile when I turn it on! When it dies
and I can no longer fix it, I will retire it to a well deserved rest.
After all, it is about 90 or so in dog years!
BOB URZ
vta...@gte.net
industrially deaf in a decade or so. Just check with your ear physician
if you don't believe me.
As someone who was in the Land of the Living 20 to 30 years ago, I am
amazed at people's expectations in car radios. In them old days, a
150-watt amplifier would do a football stadium. 20 watts was considered
a very reasonable home amplifier wattage, and 5 watts is still enough
to make the neighbors complain.
What has happened in the interval is that speaker manufacturers have come
up with power sink loudspeaker systems with tiny, tiny efficiencies and
minuscule fidelity improvements over older, more efficient designs.
BTW, the latest 1 Kilowatt car stereo is going to make a noticeable dent
on your gas mileage and it requires its own alternator that can double
as a power supply for your microwave oven.
Mark Williams
> It sure is easy to look back 20 to 30 years and toss stones at people on
> what you know now but they did not know then. .... There is a learning
> curve on any
> product.
Bob is quite correct. Parts were lousy, and few really sharp engineers were
working onaudio, it was considered too consumer-oriented and not challenging
(that is one very good
reason we lost the whole market). Bob Carver came up with a very good
design,
given the parts he had to work with then. His later ideas on stepped power
supplies and
"mag field amps" (triac phase regulated power supplies) were good steps
forward.
I am rather surprised at the light weight of the Carver amps I have repaired
with those
"mag field amps", and I understand they have a good
following among "roadies" because of it (if only they didn't buzz!).
Other people did good work as well. David Hafler and Erno Borbeley were busy
at Dynaco
developing the 400 series, which were extremely rugged due to design
overkill, including
an obsessive amount of protection circuitry, in addition to using a cascode
output with 4 or 8
(in the 416) output transistors per side. In my experience, there are a lot
more of those old
Dynacos still running today than Phase Linears, maybe overkill is not such a
bad idea.
>What was the choice on high power/high voltage output
>transistors 30 years ago? (and their bandwidth)
Pretty limited. There were a fair number of high-power NPN devices, like the
2N3773, which
were OK in quasi-complementary designs. Very few complementary high power
devices
existed until the late 60s and early 70s (the 2N3716/2N3792 pair is an early
example). These
were very slow, and really limited designers. Today we have some amazing
choices.
> Did people think about SOA and other similar "safe" concepts back then
> like they do now? NO. But they learned.
There was a good understanding that the parts failed, but not why, until the
early 70s.Second breakdown was not really well documented in the 60s; data
sheets did not give
you the nice charts they do now of forward biased safe operating area.
Linear power supply
designers and disk drive servo designers demanded that information, and that
is probably why
it is common now. I think more good transistors
were designed for disk drive servos than ever for audio, but fortunately they
were ideal
for it.
> Phase linear got the market thinking on what it could or might be....
> Give Phase linear credit for high current power supplies, number of high
> voltage output devices per channel, watts/ch. (all relative to the times
> and
> competition). ....
>
> Which brings us to were we are today. In pro sound land, we have
> robustness and we
> have high current 2 ohms amps. We have robust high voltage/ high current
> outputs.
> We have heavy rack mount style cases and custom high current toroid
> transformers. We have class a -z type amplifiers (or so it seems). Today,
> we still blow up amps. .... Maybe in 20 years
Peter Larsen
BOB URZ <so...@inetnebr.com> skrev i en
nyhedsmeddelelse:3760081C...@inetnebr.com...
: Phase linear got the market thinking on what it could or might be.
: There was no pro sound market then like there was now. People were
: adapting theater type system for the early touring systems. There was not
: compact high power touring boxes or yamaha PMxx consoles, or racks of
: heavy metal high current stable power amps.
: People innovated and rolled their own. These systems would be a joke
: today, but in
: 1970, they were state of the art (black art).
I think you underestimate the quality of the old large horn loaded systems,
of course most of the woodwork would need stiffening, but a large
high-efficiency system is highly likely to have less distortion than a small
high efficiency and/or high output system. 1970'ties loudspeaker systems
happen to tend to do very very well with quality signal sources. The main
factor contributing to the distortion of the systems of that day and age was
to the best of my knowledge mixer input overload because the input designers
hadn't really catered for dynamic microphones delivering line level output
signals.
: So, I stand by my statement. As far as Crown goes, yes they built a good
: product. I have seen DC-150's and 300 blow up also. They had there own
quirks. Put
: a 4 ohms load on a early one with out a fan
Hmm .. well, that would be unwise, looking at it from another angle the
Crowns were not that likely to blow up speakers, while Phase400's and 700's
did end up having a baaad reputation for that over here. However that may
well have been because people had not yet learned to use 16 Ohm units for PA
use! As for the sound, well: the Phase400 outplayed anything in terms of
sheer clarity of punch, but the Dynaco Stereo 400 didn't do bad either, and
it didn't blow neither itself nor the loudspeaker units up as the Phase's
could occasionally do - at least one gig over here found them quite costly.
: Which brings us to were we are today. In pro sound land, we have
: robustness and we
: have high current 2 ohms amps. We have robust high voltage/ high current
: outputs.
How about smart crossovers, mixers that don't overload their inputs, no
underdimensioned balancing transformers in the inputs, condenser microphones
that aren't as prone to clip as most brands of that day and age. Quality is
much better today, but I do not really think it is a matter of loudspeaker
and loudspeaker systems design, sometimes when I hear the modern small bass
systems I kinda feel it is in spite of loudspeaker and loudspeaker systems
design.
: We are in the early days of digital control & processing in pro sound.
: Maybe in 20 years
: we will laugh and say what we should have done differently in the 90's!
I think we will rethink the van space saving considerations .... mind you:
I am not saying they are not valid, but there aint no biig sound from any
small box, given enough power, there is a very loud and hard, but still also
small sound. Perhaps aiming for ever louder systems is not the way to go -
unless to attract traffic to alt.support.tinnitus!
: I would not want to go back to using 70's amps in a sound job I was
: doing,
Oh, the Yamaha P2200 is in fact a 70's amp. It didn't sound as good as the
Phase's, but it had the same power, a reasonable punch - tho' not ever
really open in its sound, didn't blow up, and didn't blow speakers up.
: but i WILL keep my old Phase stuff at home and smile when I turn it on!
And quite rightly so, because the Phase's are up there in the top league of
all time quality open and punchy bass suppliers. A *quality* signal source
and a pair of Klipsch's, and stuff from this day and age would find it hard
to beat.
Kind regards
Peter Larsen
Javier Perez
I collect Phase Linears and lovem but I wouldn't attach reliability to any of their
products
especially the the Series 2s possibly because of the badly regulated
voltage supply to the front end op-amps on just about all them Also, Series 2 amps
which like reject props
from the Empire Strikes Back.
Furthermore, nothing, absolutely nothing is as rock solid or reliable as a Mac.
I have pairs of 50s, 2100s and 40s which have relegated all my Phase stuff to the
bookshelves
as display items except for my kitchen stereo The macs also sound better and are quite
cheap if
you don't mind rust. Ditto for Mac preamps and tuners. Also, Mac amp failures rarely
threaten speakers
I attach a great deal of importance to this as I've already lost two pairs of speakers
to Phase Linear pyrotechnics.
See Ya
Javier
PS: Still looking for a 7000 series 2 cassette deck. Anybody got one?
BOB URZ
Peter Larsen wrote:
> Hi Bob,
>
> BOB URZ <so...@inetnebr.com> skrev i en
> nyhedsmeddelelse:3760081C...@inetnebr.com...
>
> : Phase linear got the market thinking on what it could or might be.
> There was not : compact high power touring boxes or yamaha PMxx consoles, or
> racks of
> : heavy metal high current stable power amps.
> :
> I think you underestimate the quality of the old large horn loaded systems,
> of course most of the woodwork would need stiffening, but a large
> high-efficiency system is highly likely to have less distortion than a small
> high efficiency and/or high output system. 1970'ties loudspeaker systems
> happen to tend to do very very well with quality signal sources. The main
> factor contributing to the distortion of the systems of that day and age was
> to the best of my knowledge mixer input overload because the input designers
> hadn't really catered for dynamic microphones delivering line level output
> signals.
>
>
Quality and quantity are relative terms. In our old shop we used to demo a set
of Altec A-7's with a 30 watt/ch
Yamaha receiver and blow the place apart. Yes, they were very efficient.
Extremely wide bandwidth? NO.
You usually pay for one with the other. Those boxes dropped off after 40 hz and
the 511 horns and the early
808 drivers sere lucky if they could couple 10K hz + very well. There were a lot
of high efficiency boxes
back then because they grew out of theater sound where the early amps were
lucky to have 20 to 50 watts of
power out of those early tube amps.
Touring systems are subject to many stresses that were not around in the 70's
like today. Back then, most systems were
ground stacked. Today, most systems are flown overhead. Ever seen a A-7 with
flying hardware? It is not a real practical thing to do. The Phase coherence of
those boxes was terrible also. The Psychology was lets see how many we can
stack.
Today, touring sound uses less efficient boxes that are tuned and optimized for
wider bandwidth and better response.
Some systems are processed before the power amp to optimize the end result.
Boxes are designed to array together
for more even response in the entire coverage area. Newer boxes from EAW (900's)
VDOS, and others are on the
cutting edge of this. These boxes have to be engineered like buildings for the
stresses of rigging and hanging other
boxes off the top and the bottom. This was not the case in the floor stack era.
People expect more now. The advent of midi controlled keyboards has only made
the bandwidth problem expand.
We demand that punch in the low end with out the sound of farting in a barrel.
As far as a home system goes, yes I would have one of those old systems and
probably be happy with it.
The speakers I have with the Phase are old custom built with a Trusonic 120w
(one of my favorite old woofers)
with EV mid horn and EV-T350 tweeter. Probably 25 year old but still going
strong after a recone!.
> Hmm .. well, that would be unwise, looking at it from another angle the
> Crowns were not that likely to blow up speakers, while Phase400's and 700's
> did end up having a baaad reputation for that over here.
That is one issue amp builders learned in latter models, relay protection
circuits!
I was working on a guitar amp once with 18" woofer when the outputs went to
dead short. The middle of that 18 looked like a sparkle/smoke cone from the 4th
of July!
Boy that stuff stinks! I hold Bob Carver in high esteem for being one of the
pioneers in the
industry. I still remember the Phase adds in audio magazines with the long hair
hippy look
standing next to a Phase amp. Deja Vue! If he knew the issues and had the parts
we
have today, There might still be 400's and 700's on the road!
>
>
> : Which brings us to were we are today. In pro sound land, we have
> : robustness and we
> : have high current 2 ohms amps. We have robust high voltage/ high current
> : outputs.
>
> How about smart crossovers, mixers that don't overload their inputs, no
> underdimensioned balancing transformers in the inputs, condenser microphones
> that aren't as prone to clip as most brands of that day and age. Quality is
> much better today, but I do not really think it is a matter of loudspeaker
> and loudspeaker systems design, sometimes when I hear the modern small bass
> systems I kinda feel it is in spite of loudspeaker and loudspeaker systems
> design.
> Unfortunateley, many people in the pro sound industy still do not understand
> what is really important
and why. All the smart equipment in the world won't help an ignorant mixer (A1)
who does not understand how to
use it. Many people still do not understand the proper way to gain stage a
system for best S/N and sound quality.
Some people don't understand an EQ cannot solve some acoustic problems. Some
people could not tell you what
ohms law was and why its important. My friend Randy Ferguson who mixes for
Mannheim Steamroller has practiced
this for years. Finesse and skill will beat overpower and volume every time.
Keeping a high power system down
in an arena setting can do wonders for the sound quality!
We do like our new toys, though. The JBL smart Pro gives us capabilities that
would have been cost prohibitive
just a while back, affordable now. The TEF is still usable, but is long overdue
for a techno upgrade. It sill likes
Dos and Win 3.1 machines. It doesn't like Pentium and Win 9x machines. The Shure
DFR-11 eq5 does wonders
for about $700. Maybe some day all our toys will talk to each other (NOT!).
> : I would not want to go back to using 70's amps in a sound job I was
> : doing,
>
> Oh, the Yamaha P2200 is in fact a 70's amp. It didn't sound as good as the
> Phase's, but it had the same power, a reasonable punch - tho' not ever
> really open in its sound, didn't blow up, and didn't blow speakers up.
Well, I did used to sell them. They were a good amp, but I did blow a few of
them up!
I tried a bridge one for a 70 volt line like the factory suggested. It lasted
about a day before
mass suicide.
> : but i WILL keep my old Phase stuff at home and smile when I turn it on!
>
> And quite rightly so, because the Phase's are up there in the top league of
> all time quality open and punchy bass suppliers. A *quality* signal source
> and a pair of Klipsch's, and stuff from this day and age would find it hard
> to beat.
>
> Kind regards
>
> Peter Larsen
When it comes to sound, every one has their opinion. The best thing a sound
person or tech can do
is have a open mind and keep the educational process active. May your power
always be conditioned
and your XLR's always have pin 2 hot (LOL)!
BOB URZ
NSE
schuyler
If you're replacing drivers in a BPJ transistor amp, with a direct coupling
configuration, and you can't find the original parts, then how do you find
suitable substitutes? Is there a practical way? Perhaps using a Beta/gain
test rig? I've repaired lots of stuff, but never quite figured out a proper
solution to the problem of not having factory selected devices for older
direct coupled amps... I finally found a theory book that has a very brief
section which addresses the theory behind calculating gain/bias voltages for
such amp configurations, but I'd be interested in what some experienced
techs/engineers have to say.
Schuyler
Austin, Texas
Peter Larsen
: Quality and quantity are relative terms.
Yup.
: You usually pay for one with the other. Those boxes dropped off after 40
hz
Yup.
: and the 511 horns and the early 808 drivers sere lucky if they could
couple
: 10K hz + very well.
Yup. Did you really have to mention the 511 .... I would much rather mention
the 60 degrees large JBL exponential with a ~40 driver ....
: There were a lot of high efficiency boxes back then because they grew out
of theater
: sound where the early amps were lucky to have 20 to 50 watts of power out
of those early
: tube amps.
Yup. Tell ya what, the best PA and the best band sound I have ever heard was
in a club sized venue, a pair of JBL 'front horn + reflex' (single 15" each)
and a pair of JBL humoungously large slant lenses. Why - well, they didn't
make a hell of a lot of noise on the stage, nothing clipped, and the room
was "cymbal sized", so treble performance was not the issue.
: Touring systems are subject to many stresses ... <etc.>
<snip>
All of it correct, but large high efficiency bass systems still sound
better, and if we can forgo say 10 dB SPL demand by turning down the amps on
stage, then it will still all fit in the van(s)! But of course -
alt.support.tinnitus could loose traffic .... that said, I also ought to say
that flying systems is also a good way to keep traffic out of that
newsgroup, and more acts to set stuff up in a responsible manner nowadays.
But I still can't understand what parents allow children to do - or rather
WHERE they allow children to do [whatever] - come festival time.
Kind regards
Peter Larsen
David Heller
> I hate to burst your old "memories bubble", but phase linear was the
> grandfather of all
> modern day high power amps. They were originally built for high end home use,
> but the
> pro's used them because there was very little choice in them days! When the
> original Phase 700 came out with 350watts/ch 8 ohms, there were no crowns, no
> crests, no QSC or others to match it at the time. Yea, you could have had a
> high power Crown Dc-300 at a whooping 150w/c. Give Phase its due, it was way
> ahead of its time. If you treated them right and did not abuse them, They were
> as good as anything else at the time. Many major tours used Phase in the early
> days of high power touring sound.. If the early units had balanced XLR inputs
> with proper rack mounts, an on/off switch, and fan cooling, you might still
> see these units out on the road!
>
> I own a 400II/3000 preamp and 5100 tuner I have had for 15+ years and they
> have been just fine. Try to find something built like them now! Yes, today
> there are many fine high power high current amps out there. Just remember who
> invented the market for it.
>
> I have toured with a national act. Anything at any given time can die a
> untimely death.
> I have seen power distro's blow smoke from the locals mis wiring the distro
> (ever smell a burnt pile of mov's?) I have seen power amps blow smoke and
> sparks like the forth of july. I have played the 2 minute drill when the
> monitors went dead during a show.
> Anything can die on the road. If you take care of it, it may live long enough
> for a second
> life on E-Bay!
>
> BOB URZ
> NSE
>
> Illia Kuriakin wrote:
>
> > My band had 2 Phase Linear amplifiers in the 1970's. They were
> > unreliable. They blew out too often and the factory took A YEAR
> > to fix them under warantee. Send your Phase Linear to the
> > junk dealer and get a Crown or other reputable amp. People
> > get Phase Linears to get the most Bang for the Buck, like
> > one watt per dollar, but if it dies on stage, you will wish
> > you paid two dollars per watt.
I have to agree with Illia Kuriakin about Phase Linear (Flame Linear) I have
first hand experience with these amplifiers. Back in 1984 while working at
Pacific Stereo in the Berkeley California store a customer tried using a Phase
Linear Amplifier attached to a pair of Infinity speakers !!! bad idea the Phase
Linear amplifier actually caught fire !! A quick witted salesperson ripped the
Amplifier right of the display unit and ran out the front door and threw it to
the ground. As a repair specialist for Pacific Stereo I found these amplifiers
the most difficult to work with. The only advice I can give regarding the repair
of these units is to replace ALL the output transistors and all the emitter
resistors in these beasts otherwise the repair will not last. By the way it took
almost a year for Phase Linear and Infinity to work out the problem why the
combination of certain Infinity speakers and Phase Linear amplifiers always leads
to auto-destruct of both. I believe it had to do with the very low
reactance(capacitive or inductive I can't recall) of the Infinity Speakers.