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Thoughts on this little oddity, anyone ...?
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Arfa Daily
Nov 7, 2011, 9:11:02 PM11/7/11
to
Had an Allen & Heath PA20-CP 2 x 500 watt powered mixer in today. Has two
completely separate and identical power amps, one of which was running very
hot very quickly. No schematics, but problem was quickly traced to an open
circuit resistor, by comparison ohms checks between the two amps. In order
to replace the resistor, it was necessary to remove the offending ("B")
power amp to get to the board underside. The power rails and ribbon from the
mixer desk section were on removable connectors, but the 4 pole speakon
connector was bolted to the rear panel and the wires were soldered directly
to the board. When I came to unsolder these wires from the socket, I noticed
that the "B" channel one was wired the opposite way round to the "A" channel
one. I noted this down to check on later.
When the amp was tested ok, I bolted it back in, and reconnected the speakon
socket the same as it was when I unsoldered it. The wires lay exactly where
they originally were, and looked absolutely factory-original, even down to
the one which went to the uppermost connector tag, having a rubber sleeve on
it, exactly the same as on the "A" channel. Except the two channels were
definitely wired arse-about-face to one another. On both channels' speakons,
the "1-" and "2-" pins were linked, as were "1+" and "2+". But on channel
"A" the ground wire was connected to the "+" pair, and on the "B" channel,
the ground was on the "-" pair.
I fired it up again, and put a sine wave in, then hooked up two channels of
my 'scope, one to the "A" output and one to the "B", both with the same
polarity, and was surprised to find that the two signals were completely
anti-phase, which meant that with the reversed connections to the speakon
sockets, they would be back in phase again to the outside world.
I then went back to the power amps' front ends near where the ribbon
connector was, and found the same thing. At the same point on each amp, the
signals were in opposite phase to one another. I then spotted three little 3
pin header blocks, with one pin pair on each designated "B", and the other
pair "A" and a little 1 or maybe an I next to the "A" in a sort of 'to the
power of' position. On the B amp, these three jumpers were set to "B", and
on the A amp they were set to "A", so clearly, these jumpers reverse the
phase of the signal coming in from the desk section. The two amps then
process the signals in antiphase to one another right to the final output,
where the 'correct' phase relationship is again restored, by wiring the
speakon connector 'wrongly'.
I have puzzled over this, and can think of no good reason for doing it that
way. I did wonder at one point if it was anything to do with being able to
make the amps bridgeable, but I downloaded a copy of the user manual, and
there is a dire warning paragraph towards the end, specifically saying that
under no circumstances should any attempt be made to operate the amps in
bridge. It also warns against making any connections between the two amps or
any speakers connected to them, although in actual fact, the 'ground' side
of each output is truly ground, and is common to both amps, the whole (dual)
power supply, and all metalwork.
What am I missing here ? Not of any real consequence, as the unit is mended
and back in its original condition, but for academic interest, it would be
good to understand the designer's thinking.
Arfa
completely separate and identical power amps, one of which was running very
hot very quickly. No schematics, but problem was quickly traced to an open
circuit resistor, by comparison ohms checks between the two amps. In order
to replace the resistor, it was necessary to remove the offending ("B")
power amp to get to the board underside. The power rails and ribbon from the
mixer desk section were on removable connectors, but the 4 pole speakon
connector was bolted to the rear panel and the wires were soldered directly
to the board. When I came to unsolder these wires from the socket, I noticed
that the "B" channel one was wired the opposite way round to the "A" channel
one. I noted this down to check on later.
When the amp was tested ok, I bolted it back in, and reconnected the speakon
socket the same as it was when I unsoldered it. The wires lay exactly where
they originally were, and looked absolutely factory-original, even down to
the one which went to the uppermost connector tag, having a rubber sleeve on
it, exactly the same as on the "A" channel. Except the two channels were
definitely wired arse-about-face to one another. On both channels' speakons,
the "1-" and "2-" pins were linked, as were "1+" and "2+". But on channel
"A" the ground wire was connected to the "+" pair, and on the "B" channel,
the ground was on the "-" pair.
I fired it up again, and put a sine wave in, then hooked up two channels of
my 'scope, one to the "A" output and one to the "B", both with the same
polarity, and was surprised to find that the two signals were completely
anti-phase, which meant that with the reversed connections to the speakon
sockets, they would be back in phase again to the outside world.
I then went back to the power amps' front ends near where the ribbon
connector was, and found the same thing. At the same point on each amp, the
signals were in opposite phase to one another. I then spotted three little 3
pin header blocks, with one pin pair on each designated "B", and the other
pair "A" and a little 1 or maybe an I next to the "A" in a sort of 'to the
power of' position. On the B amp, these three jumpers were set to "B", and
on the A amp they were set to "A", so clearly, these jumpers reverse the
phase of the signal coming in from the desk section. The two amps then
process the signals in antiphase to one another right to the final output,
where the 'correct' phase relationship is again restored, by wiring the
speakon connector 'wrongly'.
I have puzzled over this, and can think of no good reason for doing it that
way. I did wonder at one point if it was anything to do with being able to
make the amps bridgeable, but I downloaded a copy of the user manual, and
there is a dire warning paragraph towards the end, specifically saying that
under no circumstances should any attempt be made to operate the amps in
bridge. It also warns against making any connections between the two amps or
any speakers connected to them, although in actual fact, the 'ground' side
of each output is truly ground, and is common to both amps, the whole (dual)
power supply, and all metalwork.
What am I missing here ? Not of any real consequence, as the unit is mended
and back in its original condition, but for academic interest, it would be
good to understand the designer's thinking.
Arfa
Michael A. Terrell
Nov 7, 2011, 11:13:27 PM11/7/11
to
Arfa Daily wrote:
>
> Had an Allen ? Heath PA20-CP 2 x 500 watt powered mixer in today. Has two
requirements for both the + and - rails. That also lowers the current
in the system ground, reducing crosstalk & possible ground loops. This
is done in some RF circuits, as well.
--
You can't have a sense of humor, if you have no sense.
Cydrome Leader
Nov 7, 2011, 11:18:07 PM11/7/11
to
N_Cook
Nov 8, 2011, 3:21:05 AM11/8/11
to
Arfa Daily <arfa....@ntlworld.com> wrote in message
news:Xc0uq.25576$gy7...@newsfe28.ams2...
Antiphase amps discussed here a year or so ago re Yamaha Stagepas and/or
another amp not A&H, I forget the make. I think ther concensus view was to
balance up power draw on ps + and - rails for deep near impulse audio output
news:Xc0uq.25576$gy7...@newsfe28.ams2...
another amp not A&H, I forget the make. I think ther concensus view was to
balance up power draw on ps + and - rails for deep near impulse audio output
Phil Allison
Nov 8, 2011, 5:18:51 AM11/8/11
to
"Arfa Daily"
>
> What am I missing here ? Not of any real consequence, as the unit is
> mended and back in its original condition, but for academic interest, it
> would be good to understand the designer's thinking.
** The idea is sometimes known as the "OOPS" system - for Out Of Phase
> What am I missing here ? Not of any real consequence, as the unit is
> mended and back in its original condition, but for academic interest, it
> would be good to understand the designer's thinking.
Stereo.
It balances the load on the common PSU at any point in time, reducing
voltage drop and electro cap ripple voltage.
Bob Carver used the idea in his famous M400a " Carver Cube" amp, et alia.
http://www.oaktreevintage.com/web_photos/Stereo_Amps_Pre/Carver_M-400A_Stereo_Amp_web.jpg
http://www.doebbe.com/hifi/pics/Carver_M400_ret_3s.jpg
Fancy A&H picking up on it .....
... Phil
N_Cook
Nov 8, 2011, 5:49:24 AM11/8/11
to
Yamaha EMX5016 mixer amp and Stagepas range and Lab Gruppen amps use
antiphase/ out of phase arangement
antiphase/ out of phase arangement
Mark Zacharias
Nov 8, 2011, 6:55:56 AM11/8/11
to
demonstrate through a common grounded speaker switcher...
Mark Z.
N_Cook
Nov 8, 2011, 8:09:38 AM11/8/11
to
Mark Zacharias <mark_za...@labolgcbs.net> wrote in message
news:4eb918cc$0$28491$a826...@newsreader.readnews.com...
Someone last week asked my advice on bridging high power amps. My advise was
don't - bridge inputs if you must, thinking that any fault tends to lead to
spectacular failure all round, I'd forgotton about this ,antiphase, reason
for not bridging
news:4eb918cc$0$28491$a826...@newsreader.readnews.com...
don't - bridge inputs if you must, thinking that any fault tends to lead to
spectacular failure all round, I'd forgotton about this ,antiphase, reason
for not bridging
Baron
Nov 8, 2011, 5:02:32 PM11/8/11
to
Hi Arfa,
Arfa Daily Inscribed thus:
I'll bet that your first suspicion is right and the amps have or are
being used in bridge configuration in some other gear.
--
Best Regards:
Baron.
Arfa Daily Inscribed thus:
being used in bridge configuration in some other gear.
--
Best Regards:
Baron.
Dave Platt
Nov 8, 2011, 5:35:20 PM11/8/11
to
In article <j9c8ni$qfq$1...@dont-email.me>, Baron <ba...@linuxmaniac.net> wrote:
>> What am I missing here ? Not of any real consequence, as the unit is
>> mended and back in its original condition, but for academic interest,
>> it would be good to understand the designer's thinking.
>>
>> Arfa
>
>I'll bet that your first suspicion is right and the amps have or are
>being used in bridge configuration in some other gear.
There's another possibility, which I saw mentioned a few years ago.
>> What am I missing here ? Not of any real consequence, as the unit is
>> mended and back in its original condition, but for academic interest,
>> it would be good to understand the designer's thinking.
>>
>> Arfa
>
>I'll bet that your first suspicion is right and the amps have or are
>being used in bridge configuration in some other gear.
By configuring the amp so that the two channels are operating in
opposition to one another, you may increase the amp's ability to
handle short periods of very high output (brief peaks) slightly.
The reasoning is this: most of the time, high-amplitude signals are
going to be in phase between the two channels. If the two channels
are operating with the same polarity, they're both going to be drawing
on the same power-supply rail during these peaks (i.e. both will be +
or both will - at any given moment). This sudden load will tend to
draw down the power-supply bypass cap for that rail, and/or will
result in a large amount of current flowing through one side of the
power supply rectifier chain. The other rail's supply capacitor won't
have any load on it at that moment, and its rectifier won't be
carrying much if any current.
On the other hand, if you invert the audio signal coming into one
channel, and then wire up the output of that channel to the speakers
"backwards", you end up with a situation in which the two channels are
usually drawing power from _opposite_ power-supply rails. This will
decrease the worst-case sag in the rail voltages, and also tend to
reduce and even out the current flow in the rectifiers (and reduce
voltage drop and heating slightly).
As a result, an amp which was designed with a "not-so-stiff" power
supply system, may be able to deliver a slightly higher amount of peak
power before it begins to clip and distort.
--
Dave Platt <dpl...@radagast.org> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!
Baron
Nov 8, 2011, 5:51:13 PM11/8/11
to
Dave Platt Inscribed thus:
Interesting analysis ! Though I thought Arfa said "Dual" power
supplies. Unless he meant dual rails from a common transformer.
--
Best Regards:
Baron.
supplies. Unless he meant dual rails from a common transformer.
--
Best Regards:
Baron.
Phil Allison
Nov 8, 2011, 6:20:37 PM11/8/11
to
"Arfa Daily"
>
> I fired it up again, and put a sine wave in, then hooked up two channels
> of my 'scope, one to the "A" output and one to the "B", both with the same
> polarity, and was surprised to find that the two signals were completely
> anti-phase,
there is significant phase shift is important. A scope triggering off the
incoming wave will it not reveal this in single channel mode - so AF used
both channels.
A much better way is to use the External Synch input on your scope and link
it to a fixed output on your bench audio oscillator ( create on if you have
to). This way, you see instantly if the signal's phase has reversed or has
a large phase shift.
Also, triggering will be rock steady with nearly any kind of distorted,
noisy or contaminated signal on the scope screen.
Try it out for a day or two - you will never go back.
... Phil
Arfa Daily
Nov 8, 2011, 8:58:22 PM11/8/11
to
"Michael A. Terrell" <mike.t...@earthlink.net> wrote in message
news:GaCdnTdypPvqMSXT...@earthlink.com...
Arfa
Arfa Daily
Nov 8, 2011, 9:03:22 PM11/8/11
to
"Cydrome Leader" <pres...@MUNGEpanix.com> wrote in message
news:j9aahv$k3m$1...@reader1.panix.com...
though there was enough filter caps on the board for it to be otherwise two
independant supplies. Certainly, two sets of + / - / gnd cables came out of
the psu for the two amps, but I must admit that I did not look at its design
closely enough to see if there was two sets of secondary windings, and two
rectifiers. The ground was certainly common to both amps, and one leg of the
output on each amp was that same ground.
Arfa
Arfa Daily
Nov 8, 2011, 9:05:17 PM11/8/11
to
"Phil Allison" <phi...@tpg.com.au> wrote in message
news:9hse0i...@mid.individual.net...
Arfa
Arfa Daily
Nov 8, 2011, 9:06:20 PM11/8/11
to
"Mark Zacharias" <mark_za...@labolgcbs.net> wrote in message
news:4eb918cc$0$28491$a826...@newsreader.readnews.com...
Arfa
Arfa Daily
Nov 8, 2011, 9:09:38 PM11/8/11
to
"Dave Platt" <dpl...@radagast.org> wrote in message
news:8enoo8-...@radagast.org...
sense when you stand back and think about it
Arfa
Arfa Daily
Nov 8, 2011, 9:18:27 PM11/8/11
to
news:9htrqe...@mid.individual.net...
Interesting. Are you squaring up the generator's sine output, to give a good
sharp transition for syncing the scope ? I was looking at the phase
reversals on this particular unit, by using 2 of the channels on the scope,
and using internal auto trigger derived from CH 1. The sync circuitry on
this Hitachi scope is very good, and will produce a perfectly stable trigger
point from virtually any waveform, no matter how complex or scruffy, but I
can see where it would be useful to be able to have a fixed known trigger
point, and from there, be able to look at relative phasing between amps, and
phase shift within an amp, using a single scope channel.
Arfa
sharp transition for syncing the scope ? I was looking at the phase
reversals on this particular unit, by using 2 of the channels on the scope,
and using internal auto trigger derived from CH 1. The sync circuitry on
this Hitachi scope is very good, and will produce a perfectly stable trigger
point from virtually any waveform, no matter how complex or scruffy, but I
can see where it would be useful to be able to have a fixed known trigger
point, and from there, be able to look at relative phasing between amps, and
phase shift within an amp, using a single scope channel.
Arfa
Mark Zacharias
Nov 8, 2011, 9:48:15 PM11/8/11
to
"N_Cook" <div...@tcp.co.uk> wrote in message
news:j9b9kd$su9$1...@dont-email.me...
Such amps are naturally adaptable for bridging.
Mark Z.
news:j9b9kd$su9$1...@dont-email.me...
Mark Z.
Phil Allison
Nov 8, 2011, 10:14:43 PM11/8/11
to
"Arfa Daily"
> "Phil Allison"
>> "Arfa Daily"
>>
>>>
>>> I fired it up again, and put a sine wave in, then hooked up two channels
>>> of my 'scope, one to the "A" output and one to the "B", both with the
>>> same polarity, and was surprised to find that the two signals were
>>> completely anti-phase,
>>
>>
>> ** When servicing audio, knowing the polarity of the test signal and if
>> there is significant phase shift is important. A scope triggering off the
>> incoming wave will it not reveal this in single channel mode - so AF used
>> both channels.
>>
>> A much better way is to use the External Synch input on your scope and
>> link it to a fixed output on your bench audio oscillator ( create on if
>> you have to). This way, you see instantly if the signal's phase has
>> reversed or has a large phase shift.
>>
>> Also, triggering will be rock steady with nearly any kind of distorted,
>> noisy or contaminated signal on the scope screen.
>>
>> Try it out for a day or two - you will never go back.
>>
>
>>
>>>
>>> I fired it up again, and put a sine wave in, then hooked up two channels
>>> of my 'scope, one to the "A" output and one to the "B", both with the
>>> same polarity, and was surprised to find that the two signals were
>>> completely anti-phase,
>>
>>
>> ** When servicing audio, knowing the polarity of the test signal and if
>> there is significant phase shift is important. A scope triggering off the
>> incoming wave will it not reveal this in single channel mode - so AF used
>> both channels.
>>
>> A much better way is to use the External Synch input on your scope and
>> link it to a fixed output on your bench audio oscillator ( create on if
>> you have to). This way, you see instantly if the signal's phase has
>> reversed or has a large phase shift.
>>
>> Also, triggering will be rock steady with nearly any kind of distorted,
>> noisy or contaminated signal on the scope screen.
>>
>> Try it out for a day or two - you will never go back.
>>
>
> Interesting. Are you squaring up the generator's sine output, to give a
> good sharp transition for syncing the scope ?
** FFS - that processing is inside any decent scope.
> good sharp transition for syncing the scope ?
Supply it with 0.5volt rms sine wave and you are away.
> The sync circuitry on this Hitachi scope is very good, and will produce a
> perfectly stable trigger point from virtually any waveform, no matter how
> complex or scruffy,
> can see where it would be useful to be able to have a fixed known trigger
> point, and from there, be able to look at relative phasing between amps,
> and phase shift within an amp, using a single scope channel.
If you ever deal with tape recorders or tape echos, there is a big
difference with a play back signal.
... Phil
Phil Allison
Nov 8, 2011, 10:19:29 PM11/8/11
to
"Arfa Daily"
"Dave Platt"
>>
>> As a result, an amp which was designed with a "not-so-stiff" power
>> supply system, may be able to deliver a slightly higher amount of peak
>> power before it begins to clip and distort.
>> As a result, an amp which was designed with a "not-so-stiff" power
>> supply system, may be able to deliver a slightly higher amount of peak
>> power before it begins to clip and distort.
>> Dave Platt
>
> Thanks Dave. This seems to be what everyone is thinking, and makes a lot
> of sense when you stand back and think about it
** Dave is wrong.
>
> Thanks Dave. This seems to be what everyone is thinking, and makes a lot
> of sense when you stand back and think about it
The only time the OOPS idea increases power is when the test frequency is
low, less than 120Hz.
This is why Bob Carver did it - to reduce by half LF ripple on the PS
voltage at frequencies between 20Hz and 120 Hz to meet his published power
specs.
... Phil
Cydrome Leader
Nov 8, 2011, 11:26:32 PM11/8/11
to
to try to balance out the + and - rails when the audio peaks. I've never
actually seen this before though.
That reminds me- does anybody unnderstood what Carver's "power steering"
was supposed to be or mean in their amps?
Phil Allison
Nov 9, 2011, 12:20:50 AM11/9/11
to
"Cydrome Leader"
> That reminds me- does anybody unnderstood what Carver's "power steering"
> was supposed to be or mean in their amps?
various clever dodges he used to save weight and cost.
His " Magnetic Field " amps were nothing of the kind. They simply employed
a triac based voltage regulator in the AC supply to improve the regulation
factor of a ridiculously small iron transformer.
In his M400 and PM-2 designs, these puny transformers would emit cracking
noises and *smoke* if you ever bench tested them at rated power for more
than 60 seconds. No thermal shut down was fitted to save the trannies
either.
From the blurbs on "Power Steering" it applies to 5.1 channel amps and
allows one audio channel to dominate the load on PSU at any given time.
Likely a simple boost inhibit circuit that allows the use of a puny AC
transformer again.
... Phil
Mark Zacharias
Nov 9, 2011, 7:29:17 AM11/9/11
to
"Cydrome Leader" <pres...@MUNGEpanix.com> wrote in message
news:j9cvdo$9a4$1...@reader1.panix.com...
are switched in on demand. (during musical peaks).
Has several advantages including being able to get away with a smaller power
transformer and smaller heat sinks. Reduces power dissipation at idle and at
low power.
It's said that such amps can sound nasty - not sure I've ever noticed that.
Mark Z.
Cydrome Leader
Nov 9, 2011, 12:47:04 PM11/9/11
to
Phil Allison <phi...@tpg.com.au> wrote:
>
> "Cydrome Leader"
>
>> That reminds me- does anybody unnderstood what Carver's "power steering"
>> was supposed to be or mean in their amps?
>
>
> ** Bob Carver was an expert at coming up with high falutin' names for
> various clever dodges he used to save weight and cost.
>
> His " Magnetic Field " amps were nothing of the kind. They simply employed
> a triac based voltage regulator in the AC supply to improve the regulation
> factor of a ridiculously small iron transformer.
Hmm, was anybody in the 70s not obsessed with triac pre-regulation in all
>
> "Cydrome Leader"
>
>> That reminds me- does anybody unnderstood what Carver's "power steering"
>> was supposed to be or mean in their amps?
>
>
> ** Bob Carver was an expert at coming up with high falutin' names for
> various clever dodges he used to save weight and cost.
>
> His " Magnetic Field " amps were nothing of the kind. They simply employed
> a triac based voltage regulator in the AC supply to improve the regulation
> factor of a ridiculously small iron transformer.
sorts of power supplies?
> In his M400 and PM-2 designs, these puny transformers would emit cracking
> noises and *smoke* if you ever bench tested them at rated power for more
> than 60 seconds. No thermal shut down was fitted to save the trannies
> either.
> From the blurbs on "Power Steering" it applies to 5.1 channel amps and
> allows one audio channel to dominate the load on PSU at any given time.
> Likely a simple boost inhibit circuit that allows the use of a puny AC
> transformer again.
power supply seemed way small for the alleged rated power across all
channels. The manual said something about this power steering crap, but
the block schematic didn't show anything indicating it was anything other
than "you can overload a channel a little bit before it burns out or the
fuse blows." It seems ok as far as amps in the early surround sound era
were. My DVD+sound setup is straight from 1998 and is this complex mess of
stuff running into a technics decoder and from there there are 5 RCA
cables running to each channel on the carver amp. There's some goofy fiber
link between the DVD player and the technics thing. Prior to this, I had a
stack of multiple stereos running everything. For a crappy action movie
where everything explodes, balance doesn't really matter.
I'm not even sure how you'd do this these days if you didn't get one of
this does everything consumer amps.
Gareth Magennis
Nov 9, 2011, 1:13:24 PM11/9/11
to
>> That reminds me- does anybody unnderstood what Carver's "power steering"
>> was supposed to be or mean in their amps?
>>
>
>
> Probably refers to "rail-switching" where higher voltage power supply
> rails are switched in on demand. (during musical peaks).
>
> Has several advantages including being able to get away with a smaller
> power transformer and smaller heat sinks. Reduces power dissipation at
> idle and at low power.
>
> It's said that such amps can sound nasty - not sure I've ever noticed
> that.
>
> Mark Z.
The Carver PM1.5 had both the triac and inadequate transformer, and rail
>> was supposed to be or mean in their amps?
>>
>
>
> Probably refers to "rail-switching" where higher voltage power supply
> rails are switched in on demand. (during musical peaks).
>
> Has several advantages including being able to get away with a smaller
> power transformer and smaller heat sinks. Reduces power dissipation at
> idle and at low power.
>
> It's said that such amps can sound nasty - not sure I've ever noticed
> that.
>
> Mark Z.
switching. High rail was + and - 125v IIRC.
Gareth.
Gareth Magennis
Nov 9, 2011, 1:35:55 PM11/9/11
to
"Gareth Magennis" <sound....@btconnect.com> wrote in message
news:6pzuq.19921$na5....@newsfe08.ams2...
by Mr Allison, and it is slightly less? 117?
Gareth.
Klay_Anderson
Nov 9, 2011, 2:07:01 PM11/9/11
to
According to the manual:
"CONSTANT POWER SWITCH Set the rear panel slide switch to match the impedance of the speakers used. Use the combined impedance value if you are connecting speakers in series or parallel. Choose the nearest match if the value is not exactly 4 or 8 ohms. Note that no damage will be done if the switch is left in the wrong position. However, you may not benefit from the full capability of the amplifier.
Constant power explained The typical amplifier is optimised to produce full power into 4 ohms and therefore considerably less into 8 ohms. The PA Series features a unique facility that ensures you get full power output into either 4 or 8 ohm speakers. It does this by reconfiguring the power supply for optimum current (4 ohms), or voltage (8 ohms)."
Perhaps this is why. They also have the ability through switches to delegate signal to the individual amps for mains and monitors.
"CONSTANT POWER SWITCH Set the rear panel slide switch to match the impedance of the speakers used. Use the combined impedance value if you are connecting speakers in series or parallel. Choose the nearest match if the value is not exactly 4 or 8 ohms. Note that no damage will be done if the switch is left in the wrong position. However, you may not benefit from the full capability of the amplifier.
Constant power explained The typical amplifier is optimised to produce full power into 4 ohms and therefore considerably less into 8 ohms. The PA Series features a unique facility that ensures you get full power output into either 4 or 8 ohm speakers. It does this by reconfiguring the power supply for optimum current (4 ohms), or voltage (8 ohms)."
Perhaps this is why. They also have the ability through switches to delegate signal to the individual amps for mains and monitors.
Phil Allison
Nov 9, 2011, 5:19:57 PM11/9/11
to
"Cydrome Leader"
>> ** Bob Carver was an expert at coming up with high falutin' names for
>> various clever dodges he used to save weight and cost.
>>
>> His " Magnetic Field " amps were nothing of the kind. They simply
>> employed
>> a triac based voltage regulator in the AC supply to improve the
>> regulation
>> factor of a ridiculously small iron transformer.
>
> Hmm, was anybody in the 70s not obsessed with triac pre-regulation in all
> sorts of power supplies?
Carver amps were the virtually the only ones to use the idea and the first
( M400) came out in the early 1980s.
( Yamaha made a version and sold about 5. )
... Phil
Phil Allison
Nov 9, 2011, 5:29:17 PM11/9/11
to
"Gareth Magennis"
>
> The Carver PM1.5 had both the triac and inadequate transformer, and rail
> switching. High rail was + and - 125v IIRC.
The regulated DC rails were +/- 23, +/- 55 +/- 80 and +/- 125.
... Phil
Mark Zacharias
Nov 10, 2011, 5:26:12 AM11/10/11
to
>"Klay_Anderson" <kl...@klay.com> wrote in message
>news:14356237.137.1320865621980.JavaMail.geo-discussion-forums@prnv30...
>delegate signal to >the .individual amps for mains and monitors.
Huh? I would suggest Mr. Carver was doing what he was best known for; taking
an unneeded or ordinary function, obfuscating or renaming it, and making it
a "feature".
More likely, although I have not checked the schematic, that the "impedance
switch" is like those of modern surround receivers: changing the transformer
output voltage downward for "4-ohm" operation, and higher for "8-ohm"
operation.
Like the rail-switching, this reduces quiescent power dissipation and heat
losses, but also limits full power capability.
Example:
I ran into an older McIntosh MA-6100 the other day. I didn't remember it had
a "4-ohm - 8-ohm" switch. So I tested it.
In the "4-ohm" position, it was a 50-watt per channel amp.
In the "8-ohm" position, it got about 90 watts at clipping.
Mark Z.
>news:14356237.137.1320865621980.JavaMail.geo-discussion-forums@prnv30...
>According to the manual:
>"CONSTANT POWER SWITCH Set the rear panel slide switch to match the
>impedance of >the speakers used. Use the combined impedance value if you
>are connecting speakers in >series or parallel. Choose the nearest match if
>the value is not exactly 4 or 8 ohms. Note that >no damage will be done if
>the switch is left in the wrong position. However, you may not >benefit
>from the full capability of the amplifier.
>ô °€ Constant power explained The typical amplifier is optimised to produce
>"CONSTANT POWER SWITCH Set the rear panel slide switch to match the
>impedance of >the speakers used. Use the combined impedance value if you
>are connecting speakers in >series or parallel. Choose the nearest match if
>the value is not exactly 4 or 8 ohms. Note that >no damage will be done if
>the switch is left in the wrong position. However, you may not >benefit
>from the full capability of the amplifier.
>full power into 4 >ohms and therefore considerably less into 8 ohms. The PA
>Series features a unique facility >that ensures you get full power output
>into either 4 or 8 ohm speakers. It does this by >reconfiguring the power
>supply for optimum current (4 ohms), or voltage (8 ohms)."
>.Perhaps this is why. They also have the ability through switches to
>Series features a unique facility >that ensures you get full power output
>into either 4 or 8 ohm speakers. It does this by >reconfiguring the power
>supply for optimum current (4 ohms), or voltage (8 ohms)."
>delegate signal to >the .individual amps for mains and monitors.
Huh? I would suggest Mr. Carver was doing what he was best known for; taking
an unneeded or ordinary function, obfuscating or renaming it, and making it
a "feature".
More likely, although I have not checked the schematic, that the "impedance
switch" is like those of modern surround receivers: changing the transformer
output voltage downward for "4-ohm" operation, and higher for "8-ohm"
operation.
Like the rail-switching, this reduces quiescent power dissipation and heat
losses, but also limits full power capability.
Example:
I ran into an older McIntosh MA-6100 the other day. I didn't remember it had
a "4-ohm - 8-ohm" switch. So I tested it.
In the "4-ohm" position, it was a 50-watt per channel amp.
In the "8-ohm" position, it got about 90 watts at clipping.
Mark Z.
Phil Allison
Nov 10, 2011, 5:31:57 AM11/10/11
to
"Mark Zacharias"
>
>>"CONSTANT POWER SWITCH Set the rear panel slide switch to match the
>>impedance of >the speakers used. Use the combined impedance value if you
>>are connecting speakers in >series or parallel. Choose the nearest match
>>if the value is not exactly 4 or 8 ohms. Note that >no damage will be done
>>if the switch is left in the wrong position. However, you may not >benefit
>>from the full capability of the amplifier.
>> Constant power explained The typical amplifier is optimised to
>>"CONSTANT POWER SWITCH Set the rear panel slide switch to match the
>>impedance of >the speakers used. Use the combined impedance value if you
>>are connecting speakers in >series or parallel. Choose the nearest match
>>if the value is not exactly 4 or 8 ohms. Note that >no damage will be done
>>if the switch is left in the wrong position. However, you may not >benefit
>>from the full capability of the amplifier.
>>produce full power into 4 >ohms and therefore considerably less into 8
>>ohms. The PA Series features a unique facility >that ensures you get full
>>power output into either 4 or 8 ohm speakers. It does this by
>> >reconfiguring the power supply for optimum current (4 ohms), or voltage
>>(8 ohms)."
>
>>.Perhaps this is why. They also have the ability through switches to
>>delegate signal to >the .individual amps for mains and monitors.
>
>
> Huh? I would suggest Mr. Carver was doing what he was best known for;
> taking an unneeded or ordinary function, obfuscating or renaming it, and
> making it a "feature".
** The paragraph is from Allan and Heath.
>>ohms. The PA Series features a unique facility >that ensures you get full
>>power output into either 4 or 8 ohm speakers. It does this by
>> >reconfiguring the power supply for optimum current (4 ohms), or voltage
>>(8 ohms)."
>
>>.Perhaps this is why. They also have the ability through switches to
>>delegate signal to >the .individual amps for mains and monitors.
>
>
> Huh? I would suggest Mr. Carver was doing what he was best known for;
> taking an unneeded or ordinary function, obfuscating or renaming it, and
> making it a "feature".
.... Phil
Arfa Daily
Nov 10, 2011, 9:04:37 PM11/10/11
to
news:9hu9hc...@mid.individual.net...
that the trigger point was still adjustable on external and could be set
anywhere on the trigger signal and if so, I'm not sure that I see how it
helps to trigger the scope externally from the same sine wave as it would
use internally on auto trigger. I can see how it would be helpful to have a
fixed trigger point, virtually at the beginning of a cycle, by squaring up
the generator's output, and then feeding that to the external trigger input.
Arfa
>
> "Arfa Daily"
>> "Phil Allison"
>>> "Arfa Daily"
>>>
>>>>
>>>> I fired it up again, and put a sine wave in, then hooked up two
>>>> channels of my 'scope, one to the "A" output and one to the "B", both
>>>> with the same polarity, and was surprised to find that the two signals
>>>> were completely anti-phase,
>>>
>>>
>>> ** When servicing audio, knowing the polarity of the test signal and if
>>> there is significant phase shift is important. A scope triggering off
>>> the incoming wave will it not reveal this in single channel mode - so AF
>>> used both channels.
>>>
>>> A much better way is to use the External Synch input on your scope and
>>> link it to a fixed output on your bench audio oscillator ( create on if
>>> you have to). This way, you see instantly if the signal's phase has
>>> reversed or has a large phase shift.
>>>
>>> Also, triggering will be rock steady with nearly any kind of distorted,
>>> noisy or contaminated signal on the scope screen.
>>>
>>> Try it out for a day or two - you will never go back.
>>>
>
>>
>> Interesting. Are you squaring up the generator's sine output, to give a
>> good sharp transition for syncing the scope ?
>
> ** FFS - that processing is inside any decent scope.
>
> Supply it with 0.5volt rms sine wave and you are away.
I'll have to look at that on my scope, but off the top of my head, I thought
> "Arfa Daily"
>> "Phil Allison"
>>> "Arfa Daily"
>>>
>>>>
>>>> I fired it up again, and put a sine wave in, then hooked up two
>>>> channels of my 'scope, one to the "A" output and one to the "B", both
>>>> with the same polarity, and was surprised to find that the two signals
>>>> were completely anti-phase,
>>>
>>>
>>> ** When servicing audio, knowing the polarity of the test signal and if
>>> there is significant phase shift is important. A scope triggering off
>>> the incoming wave will it not reveal this in single channel mode - so AF
>>> used both channels.
>>>
>>> A much better way is to use the External Synch input on your scope and
>>> link it to a fixed output on your bench audio oscillator ( create on if
>>> you have to). This way, you see instantly if the signal's phase has
>>> reversed or has a large phase shift.
>>>
>>> Also, triggering will be rock steady with nearly any kind of distorted,
>>> noisy or contaminated signal on the scope screen.
>>>
>>> Try it out for a day or two - you will never go back.
>>>
>
>>
>> Interesting. Are you squaring up the generator's sine output, to give a
>> good sharp transition for syncing the scope ?
>
> ** FFS - that processing is inside any decent scope.
>
> Supply it with 0.5volt rms sine wave and you are away.
that the trigger point was still adjustable on external and could be set
anywhere on the trigger signal and if so, I'm not sure that I see how it
helps to trigger the scope externally from the same sine wave as it would
use internally on auto trigger. I can see how it would be helpful to have a
fixed trigger point, virtually at the beginning of a cycle, by squaring up
the generator's output, and then feeding that to the external trigger input.
Arfa
Phil Allison
Nov 10, 2011, 10:34:59 PM11/10/11
to
"Arfa Daily"
>>
>>>> ** When servicing audio, knowing the polarity of the test signal and if
>>>> there is significant phase shift is important. A scope triggering off
>>>> the incoming wave will it not reveal this in single channel mode - so
>>>> AF used both channels.
>>>>
>>>> A much better way is to use the External Synch input on your scope and
>>>> link it to a fixed output on your bench audio oscillator ( create on if
>>>> you have to). This way, you see instantly if the signal's phase has
>>>> reversed or has a large phase shift.
>>>>
>>>> Also, triggering will be rock steady with nearly any kind of distorted,
>>>> noisy or contaminated signal on the scope screen.
>>>>
>>>> Try it out for a day or two - you will never go back.
>>>>
>>
>>>
>>> Interesting. Are you squaring up the generator's sine output, to give a
>>> good sharp transition for syncing the scope ?
>>
>> ** FFS - that processing is inside any decent scope.
>>
>> Supply it with 0.5volt rms sine wave and you are away.
>
>
> I'll have to look at that on my scope, but off the top of my head, I
> thought that the trigger point was still adjustable on external and could
> be set anywhere on the trigger signal and if so, I'm not sure that I see
> how it helps to trigger the scope externally from the same sine wave as it
> would use internally on auto trigger.
** But it is NOT the same sine wave !!!!!!!!!!!!
>>>> ** When servicing audio, knowing the polarity of the test signal and if
>>>> there is significant phase shift is important. A scope triggering off
>>>> the incoming wave will it not reveal this in single channel mode - so
>>>> AF used both channels.
>>>>
>>>> A much better way is to use the External Synch input on your scope and
>>>> link it to a fixed output on your bench audio oscillator ( create on if
>>>> you have to). This way, you see instantly if the signal's phase has
>>>> reversed or has a large phase shift.
>>>>
>>>> Also, triggering will be rock steady with nearly any kind of distorted,
>>>> noisy or contaminated signal on the scope screen.
>>>>
>>>> Try it out for a day or two - you will never go back.
>>>>
>>
>>>
>>> Interesting. Are you squaring up the generator's sine output, to give a
>>> good sharp transition for syncing the scope ?
>>
>> ** FFS - that processing is inside any decent scope.
>>
>> Supply it with 0.5volt rms sine wave and you are away.
>
>
> I'll have to look at that on my scope, but off the top of my head, I
> thought that the trigger point was still adjustable on external and could
> be set anywhere on the trigger signal and if so, I'm not sure that I see
> how it helps to trigger the scope externally from the same sine wave as it
> would use internally on auto trigger.
Various audio devices invert, phase shift, phase modulate and even time
shift sine waves !!!
> I can see how it would be helpful to have a fixed trigger point, virtually
> at the beginning of a cycle,
the same wave on the scope starts at a zero.
I have mine so the first half cycle is positive when there is no phase
shift.
With external synch, the scope is always triggered and the level on the
screen does not matter.
FFS - TRY IT !!!!!!!!!!!
... Phil
Cydrome Leader
Nov 10, 2011, 11:33:42 PM11/10/11
to
Phil Allison <phi...@tpg.com.au> wrote:
>
> "Cydrome Leader"
>
>>> ** Bob Carver was an expert at coming up with high falutin' names for
>>> various clever dodges he used to save weight and cost.
>>>
>>> His " Magnetic Field " amps were nothing of the kind. They simply
>>> employed
>>> a triac based voltage regulator in the AC supply to improve the
>>> regulation
>>> factor of a ridiculously small iron transformer.
>>
>> Hmm, was anybody in the 70s not obsessed with triac pre-regulation in all
>> sorts of power supplies?
>
>
> ** What drugs are you on ?
Want some?
>
> "Cydrome Leader"
>
>>> ** Bob Carver was an expert at coming up with high falutin' names for
>>> various clever dodges he used to save weight and cost.
>>>
>>> His " Magnetic Field " amps were nothing of the kind. They simply
>>> employed
>>> a triac based voltage regulator in the AC supply to improve the
>>> regulation
>>> factor of a ridiculously small iron transformer.
>>
>> Hmm, was anybody in the 70s not obsessed with triac pre-regulation in all
>> sorts of power supplies?
>
>
> ** What drugs are you on ?
As I said, all sorts of old power supplies were made with SCRs and
preregulators before the transformer.
The smaller HP/Agilent bench power supplies are still made this way. I
guess you get a smaller heatsink and a little more efficiency.
Phil Allison
Nov 10, 2011, 11:39:50 PM11/10/11
to
"Cydrome Leader"
>>> Hmm, was anybody in the 70s not obsessed with triac pre-regulation in
>>> all
>>> sorts of power supplies?
>>
>>
>> ** What drugs are you on ?
>
> Want some?
>
> As I said, all sorts of old power supplies were made with SCRs and
> preregulators before the transformer.
You PITA fuckwit troll.
... Phil
Cydrome Leader
Nov 11, 2011, 3:29:27 PM11/11/11
to
supplies" is not a subset of audio amplifiers. When did this occur to you?
Arfa Daily
Nov 11, 2011, 8:30:49 PM11/11/11
to
news:9i3jf5...@mid.individual.net...
Yeah, ok. I tried it today, and I see what you're saying now. Once you've
set the trigger point on the sine sample from the generator that you're
driving the external trigger input from, then that's it fixed for all
subsequent measurements and you should be able to see any phase shifts or
inversions. When I said about squaring up the sample, I was thinking that by
doing this, not only do you phase lock the scope to the original wave, you
also have an always-known point that the triggering is locked to. If you did
the squaring with a decent comparator, that trigger point could be fixed
within a few degrees of the zero crossing for all cases, eliminating the
need to twiddle the trigger level, and pick some arbitrary point anywhere on
the rising or falling slopes of the sine.
Arfa
set the trigger point on the sine sample from the generator that you're
driving the external trigger input from, then that's it fixed for all
subsequent measurements and you should be able to see any phase shifts or
inversions. When I said about squaring up the sample, I was thinking that by
doing this, not only do you phase lock the scope to the original wave, you
also have an always-known point that the triggering is locked to. If you did
the squaring with a decent comparator, that trigger point could be fixed
within a few degrees of the zero crossing for all cases, eliminating the
need to twiddle the trigger level, and pick some arbitrary point anywhere on
the rising or falling slopes of the sine.
Arfa
William Sommerwerck
Nov 12, 2011, 10:38:42 AM11/12/11
to
The most likely reason is that it reduces the peak current drawn from each
side of the power supply.
side of the power supply.
William Sommerwerck
Nov 12, 2011, 10:41:13 AM11/12/11
to
> That reminds me - does anybody understand what Carver's
desciptions that bore little or no relationship to how the circuit actually
worked.
> "power steering" was supposed to be or mean in their amps?
Whatever Bob meant it to mean. Bob was notorious for coming up with
desciptions that bore little or no relationship to how the circuit actually
worked.
William Sommerwerck
Nov 12, 2011, 10:43:22 AM11/12/11
to
> His "Magnetic Field" amps were nothing of the kind. They simply employed
> a triac-based voltage regulator in the AC supply to improve the regulation
> factor of a ridiculously small iron transformer.
There /is/ such a thing as a magnetic amplifier, but this wasn't it. Other
claims made for this product were similarly untrue. One normally gullible
reviewer was so pissed-off that he told people how angry he was with Carver.
William Sommerwerck
Nov 12, 2011, 10:44:55 AM11/12/11
to
> I'm not even sure how you'd do this these days if you didn't get
> one of these does-everything consumer amps.
You simply buy separate mono and/or stereo amps.
William Sommerwerck
Nov 12, 2011, 10:50:13 AM11/12/11
to
"Klay_Anderson" <kl...@klay.com> wrote in message
news:14356237.137.1320865621980.JavaMail.geo-discussion-forums@prnv30...
news:14356237.137.1320865621980.JavaMail.geo-discussion-forums@prnv30...
According to the manual:
"CONSTANT POWER SWITCH Set the rear panel slide switch to match the
impedance of the speakers used. Use the combined impedance value if you are
connecting speakers in series or parallel. Choose the nearest match if the
value is not exactly 4 or 8 ohms. Note that no damage will be done if the
switch is left in the wrong position. However, you may not benefit from the
full capability of the amplifier.
?? Constant power explained The typical amplifier is optimised to produce
"CONSTANT POWER SWITCH Set the rear panel slide switch to match the
impedance of the speakers used. Use the combined impedance value if you are
connecting speakers in series or parallel. Choose the nearest match if the
value is not exactly 4 or 8 ohms. Note that no damage will be done if the
switch is left in the wrong position. However, you may not benefit from the
full capability of the amplifier.
full power into 4 ohms and therefore considerably less into 8 ohms. The PA
Series features a unique facility that ensures you get full power output
into either 4 or 8 ohm speakers. It does this by reconfiguring the power
supply for optimum current (4 ohms), or voltage (8 ohms)."
This was hardly unique to Carver. I remember a Sony amp that used such a
Series features a unique facility that ensures you get full power output
into either 4 or 8 ohm speakers. It does this by reconfiguring the power
supply for optimum current (4 ohms), or voltage (8 ohms)."
system, and there were undoubtedly dozens of others.
Bruce Esquibel
Nov 13, 2011, 6:50:18 AM11/13/11
to
William Sommerwerck <grizzle...@comcast.net> wrote:
> Whatever Bob meant it to mean. Bob was notorious for coming up with
> desciptions that bore little or no relationship to how the circuit actually
> worked.
Yeah but that was his worst fault in my opinion.
> Whatever Bob meant it to mean. Bob was notorious for coming up with
> desciptions that bore little or no relationship to how the circuit actually
> worked.
At least the products he designed/built was reasonably priced and worked.
Some of it like the Sonic Hologram Generator built into a couple of the
preamps did work pretty close to his verbal description, if you could get it
setup properly. Once I got a copy of the "test record", everything fell into
place and I enjoyed that "effect" for years.
Some of the other stuff like the "Auto Correlator" was nothing more than an
adjustable noise gate and was a fairly useless waste of a button and knob.
Same with the TX11 tuner, unless you wanted to drop the 10K (at the time)
for the Day-Sequerra, that was a very good tuner for urban areas like
Chicago.
I probably owned at least one of everything Carver made up through the cd
player (digital time lens?) and never felt ripped off. The only things that
never survived my abuse was a pair of the cubes, but I still have a pair of
the 1.5t's and except for one that has a cold start problem, they both still
work just fine.
You guys are making him out like he was selling Tice Clocks.
That type of wordy hype was fairly common in the 80's, besides Carver there
was DAK Industries, sort of a Sharper Image of the time (which was another
one with long verbal descriptions), Hey! Drew Kaplan here, driving in to
work today I thought to myself, wouldn't it be great to have a electric
shaver that you could plug into your car lighter....
Then 8 or 9 paragraphs on how this razor was designed, developed and how
it's going to end world hunger and spread peace across the world.
Say what you want about Bob Carver but there was the satisfaction of being
the few peices of audio hardware with the "Made in USA" label on them.
-bruce
b...@ripco.com
William Sommerwerck
Nov 13, 2011, 10:11:19 AM11/13/11
to
> Some of it like the Sonic Hologram Generator built into a couple of the
> preamps did work pretty close to his verbal description, if you could get
it
> set up properly. Once I got a copy of the "test record", everything fell
> preamps did work pretty close to his verbal description, if you could get
it
into
> place and I enjoyed that "effect" for years.
The SHG actually worked wonderfully with simply miked recordings. I no
> place and I enjoyed that "effect" for years.
longer use mine, but it made my own recordings sound more like what I'd
actually heard at the mic. That's saying something.
However... When I suggested that the device didn't /really/ work the way he
thought it did, and that he had possibly stumbled onto something
significant, Bob dismissed my suggestion. "No, it works the way it's
supposed to." It was like talking to John Atkinson.
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