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Patrick Turner Patrick Turner is offline
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Default Low Frequency Mains Noise



Phil Allison wrote:

"Patrick Turner"


When I measure the "240Vac" here is usually is stable enough to get a
nearly constant reading on a DMM,


** Must be a basic 3.5 digit one ( 2000 count) with only 1 volt resolution
when reading 240 volts AC.

Any DMM with a larger count allows changes of 0.1 volts to be seen -
then the last digit is never steady.


Indeed, I'll get 240.XX Vac maybe even 24X.XX if the voltage is just
either side of 240.0Vac.

That's less than 1% Vac change.

But it slowly varies between 235Vac on cold winter nights of heavy
loadings to 255Vac when load is light.


** What drivel.


Not so, this is without changing local loads here in my shed.

Rarely does the mains ever bounce rapidly between 235Vac and 255Vac.

One has to be careful when setting bias in fixed bias amps when mains
Vac is low. When it rises to 255V sometimes, the B+ rails goes high and
the Ia of the output tubes rises alarmingly in fixed bias triode amps
and also in multigrid output tubes if the screen voltage is not
regulated, and rises also with mains rise.

It will instantly drop by 7 or 8 volts if you switch a ( 2.4 kW) electric
heater on AND jumps up by 6 volts when the ( 2kW) jug turns itself off
when it has boiled.


Not necessarily so.

But the combined efforts of hundreds of people in my suburb all boiling
jugs and turning heaters on and off contributes to making the mains
jitter up and down in levels we see, and not by the amount you state
unless the mains wiring is over a long distance.

A heater of 2.4kW draws 10 amps ac, and if the wire has only 1 ohm
resistance from street wires to the jug, a 10Vac drop would occur.
But my house supply wires are rated for much more than 40 amps, and the
shed power supply is an extension off the 40amp stove & laundry circuit
and has a sub board in the shed with 6 metres of wire rated at 20A to
the outlets. I doubt resistance is much more than 0.1 ohms.


When I look at the rectified Vdc, it shows the expected variations of
+/- 30mV.


** Complete ********.


No.

Any unregulated DC supply FOLLOWS all variations in the AC voltage by the
same percentage.


Agreed.

You misunderstand me. I have been trying to say this 3 times now.

But the typical B+ rail variations I see is in the form of low F noise
below 5Hz and down to Dc and ranging
+/- 30mV peak. Occasionally, the peaks are larger when someone turns
something on or off that draws severe current, or when 10 people
nearby all happen to turn heaters on/off within a very short time.

Some places will be much worse than mine.


Regulated DC supplies REGULATE against supply voltage and load current
variations, not just load current.


Indeed they should, unless the input Vdc falls below the level required
across the pass device to maintain regulation or if the current output
is limited, and the output tries to exceed the limit. Thus regulators
have to work with a voltage x current range and power is dissipated in
the pass element, or shunt element if its a shunt reg. Both cost time
and effort to make and you pay for the power.

Not greenhouse friendly either. But then many people use far more energy
in their warm cosy houses in winter while I type to you huddled over a
750W heater, or use 9kW air conditioning to prevent being sweaty and
smelly in summer.

But I digress...

LC filters have resonances and can make rail noise at LF *worse*, but
don't do as well as RC filters at real low F. Humungous values of C is
the simplest solution to B+ rail changes at F above 0.3Hz. But those
pesky noise voltages below 0.3Hz will persist. But such noise is easily
filtered by regulating the the B+ for the critical stages only, so the
power consumption and cost of building the reg for say 20mA is very
easy.

Perhaps there are ways and means of making a two stage CLCLC filter so
that the Fo of each LC section is different, and the first one acts to
make a series impedance which critically loads the Q of the second LC
section so the final response is without peaks around either Fo of each
LC section. Perhaps adding a series L between the center C and 0V of the
CLCLC so that its tuned to 100Hz will make a trap for the 100Hz, and
keep the size and weight of all chokes to small while C is high because
its cheaper than L.

There used to be an only passive filter calculator at some pomme
university but the guy who wrote the program which couldn't be
downloaded died and I have not seen any other program. I'm not much good
at calculating passive CLR filters with 6 or more elements.

Once established, the CLC type of filter wastes very little power.

Patrick Turner.

..... Phil

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Default Low Frequency Mains Noise

"Ian Bell" wrote in message

Arny Krueger wrote:
"Ian Bell" wrote in message

Eeyore wrote:
Ian Bell wrote:

Since there are untold preamp designs with unregulated
supplies
Bad preamps you mean ?

Graham


You tell me. I have the schematics for many broadcast
consoles and professional music mixers from the 50s that
use unregulated supplies.


Standards for audio were a lot lower in the 50s, if you
didn't ever notice when you listened to a lot of
recordings from that time. There are some exceptional
recordings that still sound good, but in general, it was
not a good time for quality sound reproduction.


I would not say they were a lot lower.


I lived back then, trust me, the standards were in general far lower. Good
sound of sorts did exist, but it was pretty rare.

Things perked up a lot in the 60s and 70s.

The flat bandwidth
extended only from 50Hz to 15KHz


....and that was a joke. Most audio reproduction systems of the day were in
trouble at 100 Hz, let alone 50. Today we can take response down to 20 Hz
seriously.

Note that speakers of that time in general were not capable of much acoustic
output by modern standards.

Other than a few very expensive microphones, the mics were about as bad as
the speakers.

but elsewhere the specs
were close to today's. An RCA broadcast console achieved
a 68dB S/N ratio with a -60dBm input signal which implies
an equivalent input noise of -128dBm - and that would not
be achievable with the LF noise I am seeing right now.


I suspect that you're looking at a transformer-coupled mic input, which says
nothing about the dynamic range of the console's output.

Furthermore, a transformer-coupled mic input can be made with wonderful
specs, since the transformer in essence covers up a lot of the sins of the
active components. But, the transformers of the day weren't all that
wonderful, either.

Maybe they had better conditioned mains supplies for
studios or maybe there was just less crap on the mains in
those days.


As a rule, audio people's standards were a ton lower in those days.

For example, I remember the regional 45 of The Righteous Brothers "You've
lost that loving feeling". It was hissy, boomy, dull sounding, and had some
pretty massive low frequency transients.

Listening to original oldies from the 50s, whether classical or pop can be a
lot of fun, but you don't do it for the high fidelity. Even the so-called
SOTA recordings, RCA Red Seal for example, had a great many clearly audible
flaws. I love the playing by the artists of the day, though. Toscanini is
one of my favorites, but listening to him conducting is about the music, not
the sound quality.


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Ian Bell wrote:

Patrick Turner wrote:

Ian Bell wrote:
Phil Allison wrote:
"Ian Bell"

Indeed. However, I would have expected the transformer to attenuate noise
in the 1Hz region

** Complete insanity.

Ordinary power transformers attenuate nothing coming it unless it is over 5
kHz.
** Complete fallacy.

Transformers by definition have a zero at zero Hz. They have a pole at
some frequency determined by the transformer inductance and the source
and load impedance. From that pole down to zero Hz their response falls
by at least 20dB/decade.


But you missed the reason why someone said "Complete insanity".

Transformers convey *all* the variations of mains amplitude, and its
these amplitude variations which are seen on the rectified signal at the
resovoir cap of the dc supply.

Hence there are *very* low frenquencies seen at the this resovoir
capacitor.

Try studying the way AM detectors work in radio sets using a diode and
RC network.


I realise that now. I am really disappointed that some members of this
group have to take such an arrogant stance in explaining things. All
that was necessary was to point out, as flipper did, that it is low
frequency amplitude modulation of the ac mains I am seeing. Asinine
remarks like 'try studying the way am detectors work' are singularly
unhelpful.

And apologies in advance for the rant.


There are others than yourself who read the news group. Some wouldn't
dare post here. Our questions and answers are informative to all readers
and not just for you.

Turning up here to ask questions when some of us have had to answer for
ourselves through diligent observations and reading books et all is
prone to getting a scorching from some of us.

I don't set out to flame anyone, but to only to inform, and there *is* a
big simularity between the principles in audio detection from AM waves
and mains borne noise voltages.

Hope you have had a nice sunday.

I rode 106km this morning on a bicycle, and pondered the greatness of
nature, recovered awhile, then went out to play chess and won more games
than I lost against a fat fellow who studies games with several computer
programs 7 days a week. I just play, and never study chess openings or
games. My rating if I had one would be only 1200. I keep telling this
fat fellow he should climb aboard a bicycle again like he used to and
pedal his way back to better physical and mental health, and I get away
with it because I am jovial about it. And when i lose a game I chuckle,
and see the folly of my games.

Occasionally I get a draw with the guy here who regularly is local club
champion and rated at about 2,000. If I ever see him with a screwdriver
in his hand, I snatch it away, and tell him to leave it alone because
he's likely to cause a major damage bill. Horses for courses. This guy
really hates to loose, which is one reason why he wins so often. But
he's a born natural at chess. Has the Chess gene.
Hopeless with tools, and understanding relationships, and doesn't follow
stories at the movies so I explain them like he explains a complex chess
game to me. I'll never be good at chess, and he'll never become a
cyclist. I value all my friends whose strengths and weaknesses are
different to my own and whose attitude allows some sharing of experience
of thought without being overrun by competitive sparing.

The fat guy who delves so deeply into openings and forcing a PC with a
chess rating of well over 2,000 into drawing a game doesn't realise the
human player with little more than crude intuitiveness can outwit a man
who tries to copy a computer.

This man had a really bad mental breakdown within the last 10 years.
Chess is good therapy for him.

Being perpetually logical, aware, and able to concentrate isn't easy for
all, and I sure could have been better at all 3.

I have a life at the keyboard here which augments what happens when I am
away from a damn keyboard.

I feel glad to be alive, don't you?

Patrick Turner.

Cheers

Ian

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Ian Bell wrote:

Patrick Turner wrote:

Ian Bell wrote:
Patrick Turner wrote:


snip,

What is the maximum voltage gain at say 1kHz?


24dB


Gee, that's only about 15x no?

What is the noise at the amp output with maximum gain and with input
grid directly shunted to 0V close to the input?


Not possible to measure accurately at the moment as the LF blips whack
the meter needle all over the place one you try to see noise below 1mV.
That said, looking at it on a scope you can see the broadband noise
underneath the LF blips and I would estimate the noise at the output
with the input shorted as about 50uV rms.


If you have 50uV of noise at the output and gain is 15x, and input is
grounded, then you could have a total of 2uV grid input noise if the
input tube is a real good one. 2uV gets amplified to make about 30uV at
the output, and some of that is LF noise. where does the rest of the
noise come from? By observation you should be able to see where the
noise is being generated and how, and find ways of stopping it without
much complexity and cost. In my MC phono amp without any GNFB with RIAA
correction, but using a passive RIAA, the LF gain at 20Hz is MUCH
greater than your 24dB yet the LF noise at the output is minimal, and
the result using 1 fet in cascode with 1 triode, then 2 triode
µ-follower gain stage produces an outcome equal or better than most
other phono amps I have tried including SS with opamps.



What happens if you temporally connect a spare 1,000uF or more to be in
parallel to the last 100uF cap in the filter line up, ie, the filter cap
giving the B+ supply to stage 1 of the mic amp?


Not tried that yet, I have a spare 470uF or two so I'll try that.

Noise should fall a lot with the extra C added where it'll do the most
good.

Think big, use enormous C values if you cannot bring yourself to make
what might be a very simple shunt regulator in your preamp.


Yes and no. I was using just a couple of RC stages using 470uF but then
I realised the five RC stage of 100Uf each would perform better. I
suppose I could go bananas and replace all the 100uF caps with 470uF ones.


The cost now of generic 470uF caps rated at 350Vdc is not huge, and far
cheaper than the 100uF caps were in real terms back in say 1960 when a
100uF cap was seen as a frivolous extravagance by bean conters in charge
of design teams at major manufacturers. Keen diyers will *NEVER* try to
emulate the pausity of design by accountants amoung yesterday's people.

Beware using simple zener diode based shunt regs close to mic input
stages though. The LF noise of the zener will find its way into signal
paths.


Agreed. I have been looking at the Maida regulator as a means of
eliminating the LF noise *prior* to the normal RC string.


Using a regulator right after the resevoir C is OK and you can then make
RC filters after that to all stages without risk of LF motorboating.
And such LF oscillations may not be obvious at first. A PS and amp can
be right on the brink of oscillation at LW and the slightest noise
will become amplified by a the peak in the response if there is one
below 1Hz.

Zeners placed across the second cap in an CRCRCRC filter can reduce LF
content and any noise the zeners generate is less than the noise which
is shunted, and following RC stages filter the noise of all types.
Zeners have higher noise at lowish currents. So if you have a +375V B+
rail and held by 5 x 5watt x 75Vdc rated zeners, heatsink the zeners
with a wrap around strip of Al aor Cu and bolt to a chassis or sink and
allow the pda to be a safe 0.75Watts each, which means you'd have Izener
= 10mA at least. And and in a preamp, the simplest shunt reg that isn't
a simple zener string is to have the string feed a base of an npn bjt
with emitter to 0V and a current limiting R between collector and B+
rail being shunt regged. This shunt eg has much lower output resistance
than a plain zener string, and a much "sharper" threshold of turn on, as
the current in the zeners gets amplified by the bjt. The bjt needs a
high Vce rating, and such bjts have low hfe and a darlington pair is the
best solution, and with a limiting series base resistance and filter cap
at the base to 0V to filter out the zener noise. Such a shunt reg works
only at LF and simply keeps the Vdc stable while your large value
electros do the job on higher F. Shunt regs are good for low current
preamp supplies and screen voltage supplies in power amps and have the
advantage that in the case where the output becomes shorted or over
currented, then the regulator doesn't have any current and survives
while it is the low cost series R in RC section that cops the heat and
fails.

I have used such shunt regs in power amps with choke input supplies, so
that the shunt reg shunts enough anode supply dc current right after
turn on to stop the B+ soaring. As the input stages and output stages
turn on the "bleeder" current of the shunt reg reduces to a low level
enough to reg the B+ to stage 1. So thus the high current in a
permanently connected bleeder resistance is avoided.

Patrick Turner.



Cheers

Ian

Patrick Turner.

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Ian Bell wrote:

Arny Krueger wrote:
"Ian Bell" wrote in message

Eeyore wrote:
Ian Bell wrote:

Since there are untold preamp designs with unregulated
supplies
Bad preamps you mean ?

Graham


You tell me. I have the schematics for many broadcast
consoles and professional music mixers from the 50s that
use unregulated supplies.


Standards for audio were a lot lower in the 50s, if you didn't ever notice
when you listened to a lot of recordings from that time. There are some
exceptional recordings that still sound good, but in general, it was not a
good time for quality sound reproduction.



I would not say they were a lot lower. The flat bandwidth extended only
from 50Hz to 15KHz but elsewhere the specs were close to today's. An RCA
broadcast console achieved a 68dB S/N ratio with a -60dBm input signal
which implies an equivalent input noise of -128dBm - and that would not
be achievable with the LF noise I am seeing right now. Maybe they had
better conditioned mains supplies for studios or maybe there was just
less crap on the mains in those days.


"Mains conditioning" for audio studios in the 1950s is not something I
have ever seen described in any tech journal. There were however mains
regulators based around saturable reactors.

Much audio gear was made to work OK without excessive filtering, and
when being fed by fairly irregular mobile mains power supplies.
BBC vans were full of gear that would try to minimise power losses and
use only battery power. Not much damn noise with batteries.

The BBC could afford batteries. The dc to tubes was at lowish voltages
and anode loads were chokes.

And mains noise has always been bad.

Much quality gear in 1950 had B+ regulation. Countless designs of tubes
oscilloscopes had a regulator using a 6080 and a pentode.

Much domestic audio gear was atrocious because design was by
accountants. The item was not built up to a quality, but down to a
price.

Cash strapped dudes who wanted perfect audio in 1950 were not able to
have the quality they yearned for because they were forced to feed the
large families of the time. No Pill. My father's generation knew the
Depression of the 1930s, and WW2, and having a few extra mV of noise at
an amp output was the least of their concerns.

Many used alcohol to overcome all problems, including those of poor
audio, hence the drink cabinets supplied in deluxe radio-grams of 1950.
Manufacturers knew the best way for punters to accept their terrible
creations was to encourage boozing and smoking. Radio and audio
manufacturers had cousins in the drinks and smokes supply businesses.

Blokes rooted the missus between drinks and smokes and arguments over
money, thus creating today's baby boomers.

Domestic survival each night in 1950 was a challenge. Bliss was a
rarity.

Patrick Turner.



Cheers

Ian



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Ian Bell wrote:

I realise that now. I am really disappointed that some members of this
group have to take such an arrogant stance in explaining things. All
that was necessary was to point out, as flipper did, that it is low
frequency amplitude modulation of the ac mains I am seeing.


How bloody obvious does it have to be ?

Graham

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Ian Bell wrote:

Eeyore wrote:
Ian Bell wrote:

Since there are untold preamp designs with unregulated
supplies


Bad preamps you mean ?


You tell me. I have the schematics for many broadcast consoles and
professional music mixers from the 50s that use unregulated supplies.


'Professional' has moved on a bit in 50+ years. I doubt they'd match
decent cheap domestic kit now. This is one thing that freaks me out about
you tubeophiles, you want to recreate the sound of half a century ago.

Graham

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Arny Krueger wrote:
"Ian Bell" wrote in message

Arny Krueger wrote:
"Ian Bell" wrote in message

Eeyore wrote:
Ian Bell wrote:

Since there are untold preamp designs with unregulated
supplies
Bad preamps you mean ?

Graham

You tell me. I have the schematics for many broadcast
consoles and professional music mixers from the 50s that
use unregulated supplies.
Standards for audio were a lot lower in the 50s, if you
didn't ever notice when you listened to a lot of
recordings from that time. There are some exceptional
recordings that still sound good, but in general, it was
not a good time for quality sound reproduction.


I would not say they were a lot lower.


I lived back then, trust me, the standards were in general far lower. Good
sound of sorts did exist, but it was pretty rare.


I lived back then too. I don't trust you.


Things perked up a lot in the 60s and 70s.

The flat bandwidth
extended only from 50Hz to 15KHz


...and that was a joke. Most audio reproduction systems of the day were in
trouble at 100 Hz, let alone 50. Today we can take response down to 20 Hz
seriously.


Home audio reproduction had trouble, yes, but not pro audio.

Note that speakers of that time in general were not capable of much acoustic
output by modern standards.

Other than a few very expensive microphones, the mics were about as bad as
the speakers.


Rubbish. Neumann mics were pentiful.

but elsewhere the specs
were close to today's. An RCA broadcast console achieved
a 68dB S/N ratio with a -60dBm input signal which implies
an equivalent input noise of -128dBm - and that would not
be achievable with the LF noise I am seeing right now.


I suspect that you're looking at a transformer-coupled mic input, which says
nothing about the dynamic range of the console's output.


It is a transformer coupled mic input - that's the only way to achieve a
decent noise figure with tubes. The spec quoted from mic input to
console output so it says everything about its dynamic range.

Furthermore, a transformer-coupled mic input can be made with wonderful
specs, since the transformer in essence covers up a lot of the sins of the
active components. But, the transformers of the day weren't all that
wonderful, either.


I expect they were the weakest link in the console and they do help the
overall noise figure but that is good design not a sin.

Maybe they had better conditioned mains supplies for
studios or maybe there was just less crap on the mains in
those days.


As a rule, audio people's standards were a ton lower in those days.

For example, I remember the regional 45 of The Righteous Brothers "You've
lost that loving feeling". It was hissy, boomy, dull sounding, and had some
pretty massive low frequency transients.


Quite possibly, but it is a long chain from the original 3 track
recording to the old 45 vinyl you played.
Cheers

Ian
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Phil Allison wrote:

"Eeysore the Congenital LIAR "
Ian Bell wrote:

Yes, that's my other problem. The simple CC cascade pair with NFB I am
using has a very poor PSRR.


Not a problem with solid state you see.

PSRRs are typically in the 120dB region.


** Really?

On what planet is that ???

TL071 = 86 dB typ

NE5532 = 100 dB typ.


Both 30+ years old designs.

http://www.national.com/pf/LM/LM4562.html

" PSRR and CMRR exceed 120dB (typ) "

Graham

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Patrick Turner wrote:

Ian Bell wrote:
Patrick Turner wrote:
Ian Bell wrote:
Phil Allison wrote:
"Ian Bell"

Indeed. However, I would have expected the transformer to attenuate noise
in the 1Hz region
** Complete insanity.

Ordinary power transformers attenuate nothing coming it unless it is over 5
kHz.
** Complete fallacy.

Transformers by definition have a zero at zero Hz. They have a pole at
some frequency determined by the transformer inductance and the source
and load impedance. From that pole down to zero Hz their response falls
by at least 20dB/decade.
But you missed the reason why someone said "Complete insanity".

Transformers convey *all* the variations of mains amplitude, and its
these amplitude variations which are seen on the rectified signal at the
resovoir cap of the dc supply.

Hence there are *very* low frenquencies seen at the this resovoir
capacitor.

Try studying the way AM detectors work in radio sets using a diode and
RC network.

I realise that now. I am really disappointed that some members of this
group have to take such an arrogant stance in explaining things. All
that was necessary was to point out, as flipper did, that it is low
frequency amplitude modulation of the ac mains I am seeing. Asinine
remarks like 'try studying the way am detectors work' are singularly
unhelpful.

And apologies in advance for the rant.


There are others than yourself who read the news group. Some wouldn't
dare post here. Our questions and answers are informative to all readers
and not just for you.

Turning up here to ask questions when some of us have had to answer for
ourselves through diligent observations and reading books et all is
prone to getting a scorching from some of us.

I don't set out to flame anyone, but to only to inform, and there *is* a
big simularity between the principles in audio detection from AM waves
and mains borne noise voltages.


I really don't have a problem with your posts Patrick - that's why I
apologised in advance. It is not what people say, it is the way they say
it. Manners cost nothing.

Hope you have had a nice sunday.


Yes I have. It was my 58th birthday yesterday.

I rode 106km this morning on a bicycle, and pondered the greatness of
nature, recovered awhile, then went out to play chess and won more games
than I lost against a fat fellow who studies games with several computer
programs 7 days a week. I just play, and never study chess openings or
games. My rating if I had one would be only 1200. I keep telling this
fat fellow he should climb aboard a bicycle again like he used to and
pedal his way back to better physical and mental health, and I get away
with it because I am jovial about it. And when i lose a game I chuckle,
and see the folly of my games.

Occasionally I get a draw with the guy here who regularly is local club
champion and rated at about 2,000. If I ever see him with a screwdriver
in his hand, I snatch it away, and tell him to leave it alone because
he's likely to cause a major damage bill. Horses for courses. This guy
really hates to loose, which is one reason why he wins so often. But
he's a born natural at chess. Has the Chess gene.
Hopeless with tools, and understanding relationships, and doesn't follow
stories at the movies so I explain them like he explains a complex chess
game to me. I'll never be good at chess, and he'll never become a
cyclist. I value all my friends whose strengths and weaknesses are
different to my own and whose attitude allows some sharing of experience
of thought without being overrun by competitive sparing.

The fat guy who delves so deeply into openings and forcing a PC with a
chess rating of well over 2,000 into drawing a game doesn't realise the
human player with little more than crude intuitiveness can outwit a man
who tries to copy a computer.

This man had a really bad mental breakdown within the last 10 years.
Chess is good therapy for him.

Being perpetually logical, aware, and able to concentrate isn't easy for
all, and I sure could have been better at all 3.

I have a life at the keyboard here which augments what happens when I am
away from a damn keyboard.

I feel glad to be alive, don't you?


Very much so.

Cheers

Ian

Patrick Turner.
Cheers

Ian



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Ian Bell wrote:

Eeyore wrote:
Ian Bell wrote:

Yes, that's my other problem. The simple CC cascade pair with NFB I am
using has a very poor PSRR.


Not a problem with solid state you see.

PSRRs are typically in the 120dB region.


Only if you use op amps.


Well who wouldn't ?


The dc coupled triple typical of the Neve class
A preamps is just as bad as its tubed version.


Except they did at least have regulated power supplies !

Graham

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Default Low Frequency Mains Noise



Ian Bell wrote:

Arny Krueger wrote:

Standards for audio were a lot lower in the 50s, if you didn't ever notice
when you listened to a lot of recordings from that time. There are some
exceptional recordings that still sound good, but in general, it was not a
good time for quality sound reproduction.


I would not say they were a lot lower. The flat bandwidth extended only
from 50Hz to 15KHz


i.e. totally crap.


but elsewhere the specs were close to today's.


********.


An RCA
broadcast console achieved a 68dB S/N ratio with a -60dBm input signal
which implies an equivalent input noise of -128dBm


Cite ? A weighted by any chance ?

Graham

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Patrick Turner wrote:

Ian Bell wrote:
Patrick Turner wrote:
Ian Bell wrote:
Patrick Turner wrote:


snip,

What is the maximum voltage gain at say 1kHz?

24dB


Gee, that's only about 15x no?


Correct but there is (will be) a 10:1 mic transformer at the input so
the overall gain is 10 times greater.

What is the noise at the amp output with maximum gain and with input
grid directly shunted to 0V close to the input?

Not possible to measure accurately at the moment as the LF blips whack
the meter needle all over the place one you try to see noise below 1mV.
That said, looking at it on a scope you can see the broadband noise
underneath the LF blips and I would estimate the noise at the output
with the input shorted as about 50uV rms.


If you have 50uV of noise at the output and gain is 15x, and input is
grounded, then you could have a total of 2uV grid input noise if the
input tube is a real good one.


Agreed and that is about -114dBV at the transformer secondary. At the
primary it is 20dB lower.

2uV gets amplified to make about 30uV at
the output, and some of that is LF noise. where does the rest of the
noise come from? By observation you should be able to see where the
noise is being generated and how, and find ways of stopping it without
much complexity and cost. In my MC phono amp without any GNFB with RIAA
correction, but using a passive RIAA, the LF gain at 20Hz is MUCH
greater than your 24dB yet the LF noise at the output is minimal,


I would be interested to know what the measured broadband noise is at
its output.

and
the result using 1 fet in cascode with 1 triode, then 2 triode
µ-follower gain stage produces an outcome equal or better than most
other phono amps I have tried including SS with opamps.


What happens if you temporally connect a spare 1,000uF or more to be in
parallel to the last 100uF cap in the filter line up, ie, the filter cap
giving the B+ supply to stage 1 of the mic amp?

Not tried that yet, I have a spare 470uF or two so I'll try that.

Noise should fall a lot with the extra C added where it'll do the most
good.

Think big, use enormous C values if you cannot bring yourself to make
what might be a very simple shunt regulator in your preamp.

Yes and no. I was using just a couple of RC stages using 470uF but then
I realised the five RC stage of 100Uf each would perform better. I
suppose I could go bananas and replace all the 100uF caps with 470uF ones.


The cost now of generic 470uF caps rated at 350Vdc is not huge, and far
cheaper than the 100uF caps were in real terms back in say 1960 when a
100uF cap was seen as a frivolous extravagance by bean conters in charge
of design teams at major manufacturers.



Agreed. You advised me of this about a year ago and I picked up a bunch
of 470uF 450 electrolytics as a result.

Keen diyers will *NEVER* try to
emulate the pausity of design by accountants among yesterday's people.


I think there is more to it than that. It is well known that a string of
five RC networks is better than a single RC network of five times the
capacitance and resistance. Employing that technique AND using much
larger caps should bring about a significant improvement.

Beware using simple zener diode based shunt regs close to mic input
stages though. The LF noise of the zener will find its way into signal
paths.

Agreed. I have been looking at the Maida regulator as a means of
eliminating the LF noise *prior* to the normal RC string.


Using a regulator right after the resevoir C is OK and you can then make
RC filters after that to all stages without risk of LF motorboating.


That's the plan.

And such LF oscillations may not be obvious at first. A PS and amp can
be right on the brink of oscillation at LW and the slightest noise
will become amplified by a the peak in the response if there is one
below 1Hz.

Zeners placed across the second cap in an CRCRCRC filter can reduce LF
content and any noise the zeners generate is less than the noise which
is shunted, and following RC stages filter the noise of all types.
Zeners have higher noise at lowish currents. So if you have a +375V B+
rail and held by 5 x 5watt x 75Vdc rated zeners, heatsink the zeners
with a wrap around strip of Al aor Cu and bolt to a chassis or sink and
allow the pda to be a safe 0.75Watts each, which means you'd have Izener
= 10mA at least. And and in a preamp, the simplest shunt reg that isn't
a simple zener string is to have the string feed a base of an npn bjt
with emitter to 0V and a current limiting R between collector and B+
rail being shunt regged. This shunt eg has much lower output resistance
than a plain zener string, and a much "sharper" threshold of turn on, as
the current in the zeners gets amplified by the bjt. The bjt needs a
high Vce rating, and such bjts have low hfe and a darlington pair is the
best solution, and with a limiting series base resistance and filter cap
at the base to 0V to filter out the zener noise. Such a shunt reg works
only at LF and simply keeps the Vdc stable while your large value
electros do the job on higher F. Shunt regs are good for low current
preamp supplies and screen voltage supplies in power amps and have the
advantage that in the case where the output becomes shorted or over
currented, then the regulator doesn't have any current and survives
while it is the low cost series R in RC section that cops the heat and
fails.

I have used such shunt regs in power amps with choke input supplies, so
that the shunt reg shunts enough anode supply dc current right after
turn on to stop the B+ soaring. As the input stages and output stages
turn on the "bleeder" current of the shunt reg reduces to a low level
enough to reg the B+ to stage 1. So thus the high current in a
permanently connected bleeder resistance is avoided.

Patrick Turner.


Cheers

Ian
Patrick Turner.


Cheers

IAn
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Eeyore wrote:

Ian Bell wrote:

I realise that now. I am really disappointed that some members of this
group have to take such an arrogant stance in explaining things. All
that was necessary was to point out, as flipper did, that it is low
frequency amplitude modulation of the ac mains I am seeing.


How bloody obvious does it have to be ?

Graham


If it were obvious I would not have asked. As I said before, it is not
what people say, it is the way they say it.

Cheers

Ian
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Eeyore wrote:

Ian Bell wrote:

Eeyore wrote:
Ian Bell wrote:

Since there are untold preamp designs with unregulated
supplies
Bad preamps you mean ?

You tell me. I have the schematics for many broadcast consoles and
professional music mixers from the 50s that use unregulated supplies.


'Professional' has moved on a bit in 50+ years.


Has it really?

I doubt they'd match
decent cheap domestic kit now. This is one thing that freaks me out about
you tubeophiles,


Nothing to do with tubeophiles. Neumann tube mics are still much revered
by pros (as are many other tube mics), as are tube mic pres (just look
at the popularity of the EMI REDD 47)

you want to recreate the sound of half a century ago.


Quite possibly. Is there something fundamentally wrong with that?

Graham


Cheers

Ian


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Eeyore wrote:

Ian Bell wrote:

Eeyore wrote:
Ian Bell wrote:

Yes, that's my other problem. The simple CC cascade pair with NFB I am
using has a very poor PSRR.
Not a problem with solid state you see.

PSRRs are typically in the 120dB region.

Only if you use op amps.


Well who wouldn't ?


Lots of people.


The dc coupled triple typical of the Neve class
A preamps is just as bad as its tubed version.


Except they did at least have regulated power supplies !


Yes, but PSRR is important for other reasons too.

Graham


Cheers

IAn
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Eeyore wrote:

Ian Bell wrote:

Arny Krueger wrote:
Standards for audio were a lot lower in the 50s, if you didn't ever notice
when you listened to a lot of recordings from that time. There are some
exceptional recordings that still sound good, but in general, it was not a
good time for quality sound reproduction.

I would not say they were a lot lower. The flat bandwidth extended only
from 50Hz to 15KHz


i.e. totally crap.


No, just different. I guess you never listend to AM radio either.


but elsewhere the specs were close to today's.


********.


Is that a technical term?


An RCA
broadcast console achieved a 68dB S/N ratio with a -60dBm input signal
which implies an equivalent input noise of -128dBm


Cite ?


RCA BC series broadcast consoles.

A weighted by any chance ?

Not specified. However it is not that hard to achieve 2uV broadband
noise at the mic input tube grid which is -114dBV with the tubes of the
day. With a 10:1 transformer that's and EIN of around -124dBV or -126dBm
if you prefer. As good as the Neve mic pres of the 70s.


Graham


Cheers

Ian
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Ian Bell wrote:

Arny Krueger wrote:

Other than a few very expensive microphones, the mics were about as bad as
the speakers.


Rubbish. Neumann mics were pentiful.


And VERY expensive which is what Arny said. Even 32 yrs ago I sold my U87 for
£400. They're about £1600 now new IIRC.

Graham

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Ian Bell wrote:

Eeyore wrote:
Ian Bell wrote:
Eeyore wrote:
Ian Bell wrote:

Since there are untold preamp designs with unregulated
supplies
Bad preamps you mean ?
You tell me. I have the schematics for many broadcast consoles and
professional music mixers from the 50s that use unregulated supplies.


'Professional' has moved on a bit in 50+ years.


Has it really?


Beyond belief ! You're likely to find more Cat5 patch leads in a modern studio
than good old fashioned GPO / bantam patch leads.

Plus tape recorders (if present) usually sit around gathering dust. I know a
studio that has FIVE Studer 24 track A800s and they're almost never used. They
also have one of these.
http://www.ams-neve.com/Products/Mus...88RS/88RS.aspx

I doubt you'd find much of this in the 50s !
http://www.ams-neve.com/Home/Home.aspx

This was state of the art in the 60s !
http://vintageking.com/Shop-Used-Cat...I-Console-used

Graham

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Ian Bell wrote:

Eeyore wrote:
Ian Bell wrote:
Arny Krueger wrote:


Standards for audio were a lot lower in the 50s, if you didn't ever notice
when you listened to a lot of recordings from that time. There are some
exceptional recordings that still sound good, but in general, it was not a
good time for quality sound reproduction.
I would not say they were a lot lower. The flat bandwidth extended only
from 50Hz to 15KHz


i.e. totally crap.


No, just different.


No, CRAP.

Graham



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Ian Bell wrote:

Eeyore wrote:
Ian Bell wrote:

An RCA
broadcast console achieved a 68dB S/N ratio with a -60dBm input signal
which implies an equivalent input noise of -128dBm


Cite ?


RCA BC series broadcast consoles.

A weighted by any chance ?

Not specified.


There's your answer then.

Graham

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"Ian Bell" wrote in message

Arny Krueger wrote:
"Ian Bell" wrote in message

Arny Krueger wrote:
"Ian Bell" wrote in message

Eeyore wrote:
Ian Bell wrote:


Since there are untold preamp designs with
unregulated supplies
Bad preamps you mean ?


Well, pretty poor. Regulated power supplies were always possible, but they
were generally rare, even in professional gear. The only pro gear from the
50s with regulated power supplies that comes quickly to mind were Ampex tape
recorders, where controlling parameters like bias despite variations in
power line voltage was almost mandatory.

Broadcast equipment such as exciters also had regulated power supplies, for
similar reasons.

You tell me. I have the schematics for many broadcast
consoles and professional music mixers from the 50s
that use unregulated supplies.


Agreed.

Standards for audio were a lot lower in the 50s, if you
didn't ever notice when you listened to a lot of
recordings from that time. There are some exceptional
recordings that still sound good, but in general, it
was not a good time for quality sound reproduction.


I would not say they were a lot lower.


I lived back then, trust me, the standards were in
general far lower. Good sound of sorts did exist, but it
was pretty rare.


I lived back then too. I don't trust you.


One difference between us being that you have made 1950s technology into
your life, while I've been pretty incorrigible about keeping up with the
years of valuable developments in technology since then. ;-)

Things perked up a lot in the 60s and 70s.


Ian has no comment about this, I wonder why?


The flat bandwidth
extended only from 50Hz to 15KHz


...and that was a joke. Most audio reproduction systems
of the day were in trouble at 100 Hz, let alone 50.
Today we can take response down to 20 Hz seriously.


Home audio reproduction had trouble, yes, but not pro
audio.


They both ate from the same rather sparsely-set table. Magnetic tape
recording was in its infancy as was loudspeaker design.

I need not travel down memory lane to remember how things were. I have
friends who have set up legacy audio systems using ca. 1950s higher end
components. Mac preamp and amps, high end EV and JBL drivers, and
professionally designed and built (tube) electronic crossovers, etc. On the
one hand it sounds surprisingly good, on the other it is completely
substandard compared to modern equipment of a similar nature.

Ian has no comment about this, I wonder why?

Note that speakers of that time in general were not
capable of much acoustic output by modern standards.


Ian has no comment about this, I wonder why?

Other than a few very expensive microphones, the mics
were about as bad as the speakers.


Rubbish. Neumann mics were plentiful.


Hello? Is there any intelligent life in there? Neumann mics are and were
premium-priced and therefore only a tiny fraction of what is and was in
actual use.

but elsewhere the specs
were close to today's. An RCA broadcast console achieved
a 68dB S/N ratio with a -60dBm input signal which
implies an equivalent input noise of -128dBm - and that
would not be achievable with the LF noise I am seeing
right now.


I suspect that you're looking at a transformer-coupled
mic input, which says nothing about the dynamic range of
the console's output.


It is a transformer coupled mic input - that's the only
way to achieve a decent noise figure with tubes.


Point being that the electronics of the day were generally noisy and had
relatively high amounts of distortion.

The spec quoted from mic input to console output so it says
everything about its dynamic range.


I was thinking of the -123 dBm input noise, but I should take rest of the
spec at its word - the console's SNR was 68 dB. Even a cheap modern
console's SNR is more like 90 dB, or about 22 dB better. That's a huge
difference!

BTW I'm presuming that the tube's SNR was referred to 0 dBM or +4 because
that is what I am referencing for the modern console.

Furthermore, a transformer-coupled mic input can be made
with wonderful specs, since the transformer in essence
covers up a lot of the sins of the active components. But, the
transformers of the day weren't all that
wonderful, either.


I expect they were the weakest link in the console and
they do help the overall noise figure but that is good
design not a sin.


Going transformerless has a big performance and cost advantage.

Maybe they had better conditioned mains supplies for
studios or maybe there was just less crap on the mains
in those days.


As a rule, audio people's standards were a ton lower in
those days. For example, I remember the regional 45 of The
Righteous Brothers "You've lost that loving feeling". It
was hissy, boomy, dull sounding, and had some pretty
massive low frequency transients.


Quite possibly, but it is a long chain from the original
3 track recording to the old 45 vinyl you played.


It was the sort of thing that was not rare in those days, but just wouldn't
happen today.

Listening to original oldies from the 50s, whether classical or pop can
be a
lot of fun, but you don't do it for the high fidelity. Even the
so-called
SOTA recordings, RCA Red Seal for example, had a great many clearly
audible
flaws. I love the playing by the artists of the day, though. Toscanini
is
one of my favorites, but listening to him conducting is about the music,
not
the sound quality.


Ian has no comment about this and even trash-canned it, I wonder why?

Methinks the truth hurts. :-(


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"Eeyore" wrote in
message
Ian Bell wrote:

Arny Krueger wrote:

Standards for audio were a lot lower in the 50s, if you
didn't ever notice when you listened to a lot of
recordings from that time. There are some exceptional
recordings that still sound good, but in general, it
was not a good time for quality sound reproduction.


I would not say they were a lot lower. The flat
bandwidth extended only from 50Hz to 15KHz


i.e. totally crap.


but elsewhere the specs were close to today's.


********.


An RCA
broadcast console achieved a 68dB S/N ratio with a
-60dBm input signal which implies an equivalent input
noise of -128dBm


Cite ? A weighted by any chance ?


Here you go, Graham. As usual the tubies can't deliver what a few searches
with google turned up almost immediately:

http://sujan.hallikainen.org/Broadca.../index.php/RCA

Click on the manual for the RCA BC 7A. However, being stereo, this was not
a product of the 50s but rather one of the late 1960s.

The actual spec on page 4 of the PDF is 68 dB below +18 dbm. IOW, only 50
dB below 0 dB. As bad as that is, I would suspect 50-15 KHz (- 3 dB)
weighting. The corresponding spec for a modern console would be about
twice that, IOW over 100 dB. (!!!!!!!!!!!!!!!!!!).

Moving on to component chassic specs, such as those on page 15 (Figure 11)
we see the sad truth - noise level was -47 dBm, with THD speced at 1% over
a restricted frequency range. A modern component would have noise about -90
dBm, with THD no worse than 0.02%.

As usual, we're getting a humongous load of BS dropped on us. :-(


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"Eeysore the Congenital LIAR "


Not a problem with solid state you see.

PSRRs are typically in the 120dB region.


** Really?

On what planet is that ???

TL071 = 86 dB typ

NE5532 = 100 dB typ.


Both 30+ years old designs.



** Totally irrelevant.

Modern pro-audio gear is CHOCK full of them.

You LYING piece of ****.




..... Phil



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Eeyore wrote:

Ian Bell wrote:

Arny Krueger wrote:
Other than a few very expensive microphones, the mics were about as bad as
the speakers.

Rubbish. Neumann mics were pentiful.


And VERY expensive which is what Arny said. Even 32 yrs ago I sold my U87 for
£400. They're about £1600 now new IIRC.

Graham


So what? We are talking professional users here.

Cheers

Ian


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Eeyore wrote:

Ian Bell wrote:

Eeyore wrote:
Ian Bell wrote:
Eeyore wrote:
Ian Bell wrote:

Since there are untold preamp designs with unregulated
supplies
Bad preamps you mean ?
You tell me. I have the schematics for many broadcast consoles and
professional music mixers from the 50s that use unregulated supplies.
'Professional' has moved on a bit in 50+ years.

Has it really?


Beyond belief ! You're likely to find more Cat5 patch leads in a modern studio
than good old fashioned GPO / bantam patch leads.

Plus tape recorders (if present) usually sit around gathering dust. I know a
studio that has FIVE Studer 24 track A800s and they're almost never used. They
also have one of these.
http://www.ams-neve.com/Products/Mus...88RS/88RS.aspx

I doubt you'd find much of this in the 50s !
http://www.ams-neve.com/Home/Home.aspx

This was state of the art in the 60s !
http://vintageking.com/Shop-Used-Cat...I-Console-used

Graham


No ,that's no 'moved on' it is simply different.

Cheers

Ian
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Eeyore wrote:

Ian Bell wrote:

Eeyore wrote:
Ian Bell wrote:
Arny Krueger wrote:
Standards for audio were a lot lower in the 50s, if you didn't ever notice
when you listened to a lot of recordings from that time. There are some
exceptional recordings that still sound good, but in general, it was not a
good time for quality sound reproduction.
I would not say they were a lot lower. The flat bandwidth extended only
from 50Hz to 15KHz
i.e. totally crap.

No, just different.


No, CRAP.

Graham


YAWN

Cheers

Ian
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"Patrick Turner"

When I measure the "240Vac" here is usually is stable enough to get a
nearly constant reading on a DMM,


** Must be a basic 3.5 digit one ( 2000 count) with only 1 volt
resolution
when reading 240 volts AC.

Any DMM with a larger count allows changes of 0.1 volts to be seen -
then the last digit is never steady.


Indeed, I'll get 240.XX Vac maybe even 24X.XX if the voltage is just
either side of 240.0Vac.

That's less than 1% Vac change.



** Another completely irrelevant reply.

Yawnnnnnnnnnnnnnn ...


But it slowly varies between 235Vac on cold winter nights of heavy
loadings to 255Vac when load is light.


** What drivel.


Not so, this is without changing local loads here in my shed.



** Another irrelevant reply.


Rarely does the mains ever bounce rapidly between 235Vac and 255Vac.



** More irrelevance - since I never claimed it did.


It will instantly drop by 7 or 8 volts if you switch a ( 2.4 kW) electric
heater on AND jumps up by 6 volts when the ( 2kW) jug turns itself
off
when it has boiled.


Not necessarily so.



** Now that IS a blatant lie.

Anyone can try it and see what happens to the AC voltage on the same
circuit.



When I look at the rectified Vdc, it shows the expected variations of
+/- 30mV.


** Complete ********.


No.


** Another BLATANT lie.


Any unregulated DC supply FOLLOWS all variations in the AC voltage by
the
same percentage.


Agreed.



** Then stop posting ****ING STUPID **** that says otherwise.

You misunderstand me.



** NO - you completely misunderstand the point.



..... Phil












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Arny Krueger wrote:
"Ian Bell" wrote in message

Arny Krueger wrote:
"Ian Bell" wrote in message

Arny Krueger wrote:
"Ian Bell" wrote in message

Eeyore wrote:
Ian Bell wrote:


Since there are untold preamp designs with
unregulated supplies
Bad preamps you mean ?


Well, pretty poor. Regulated power supplies were always possible, but they
were generally rare, even in professional gear. The only pro gear from the
50s with regulated power supplies that comes quickly to mind were Ampex tape
recorders, where controlling parameters like bias despite variations in
power line voltage was almost mandatory.

Broadcast equipment such as exciters also had regulated power supplies, for
similar reasons.

You tell me. I have the schematics for many broadcast
consoles and professional music mixers from the 50s
that use unregulated supplies.


Agreed.

Standards for audio were a lot lower in the 50s, if you
didn't ever notice when you listened to a lot of
recordings from that time. There are some exceptional
recordings that still sound good, but in general, it
was not a good time for quality sound reproduction.


I would not say they were a lot lower.


I lived back then, trust me, the standards were in
general far lower. Good sound of sorts did exist, but it
was pretty rare.


I lived back then too. I don't trust you.


One difference between us being that you have made 1950s technology into
your life, while I've been pretty incorrigible about keeping up with the
years of valuable developments in technology since then. ;-)


Not true. I use a 24bit standalone DAW for most of my recording work
plus other digital outboard gear. The fact is, I think 50s designs have
a place too.

Things perked up a lot in the 60s and 70s.


Ian has no comment about this, I wonder why?


There's nothing to say. I was in the pro audio scene in the 70s. It was
great. The big change was multi-tracking and noise reduction. But then
Studer brought out the J4 in the 50s, all tubes and sounding great even
by today's standards.

The flat bandwidth
extended only from 50Hz to 15KHz


...and that was a joke. Most audio reproduction systems
of the day were in trouble at 100 Hz, let alone 50.
Today we can take response down to 20 Hz seriously.


Home audio reproduction had trouble, yes, but not pro
audio.


They both ate from the same rather sparsely-set table. Magnetic tape
recording was in its infancy as was loudspeaker design.

I need not travel down memory lane to remember how things were. I have
friends who have set up legacy audio systems using ca. 1950s higher end
components. Mac preamp and amps, high end EV and JBL drivers, and
professionally designed and built (tube) electronic crossovers, etc. On the
one hand it sounds surprisingly good, on the other it is completely
substandard compared to modern equipment of a similar nature.

Ian has no comment about this, I wonder why?


Do I have to comment on everything?

Note that speakers of that time in general were not
capable of much acoustic output by modern standards.


Ian has no comment about this, I wonder why?


It's rubbish. Today's speakers if anything are less efficient.

Other than a few very expensive microphones, the mics
were about as bad as the speakers.


Rubbish. Neumann mics were plentiful.


Hello? Is there any intelligent life in there? Neumann mics are and were
premium-priced and therefore only a tiny fraction of what is and was in
actual use.


All pro mics were premium priced and pros bought them.

but elsewhere the specs
were close to today's. An RCA broadcast console achieved
a 68dB S/N ratio with a -60dBm input signal which
implies an equivalent input noise of -128dBm - and that
would not be achievable with the LF noise I am seeing
right now.


I suspect that you're looking at a transformer-coupled
mic input, which says nothing about the dynamic range of
the console's output.


It is a transformer coupled mic input - that's the only
way to achieve a decent noise figure with tubes.


Point being that the electronics of the day were generally noisy and had
relatively high amounts of distortion.


No, the point being that a NF of 6dB was achievable even then. No matter
what future developments bring they cannot possible reduce the noise by
more than 6dB.

The spec quoted from mic input to console output so it says
everything about its dynamic range.



I was thinking of the -123 dBm input noise, but I should take rest of the
spec at its word - the console's SNR was 68 dB. Even a cheap modern
console's SNR is more like 90 dB, or about 22 dB better. That's a huge
difference!


Rubbish. You clearly do not understand noise calculations. ANY console
with 60dB gain and a 200R source cannot possibly have a 20KHz bandwidth
output noise below -74dBm.


BTW I'm presuming that the tube's SNR was referred to 0 dBM or +4 because
that is what I am referencing for the modern console.

Furthermore, a transformer-coupled mic input can be made
with wonderful specs, since the transformer in essence
covers up a lot of the sins of the active components. But, the
transformers of the day weren't all that
wonderful, either.


I expect they were the weakest link in the console and
they do help the overall noise figure but that is good
design not a sin.


Going transformerless has a big performance and cost advantage.


Not if you are using tubes.

Maybe they had better conditioned mains supplies for
studios or maybe there was just less crap on the mains
in those days.
As a rule, audio people's standards were a ton lower in
those days. For example, I remember the regional 45 of The
Righteous Brothers "You've lost that loving feeling". It
was hissy, boomy, dull sounding, and had some pretty
massive low frequency transients.


Quite possibly, but it is a long chain from the original
3 track recording to the old 45 vinyl you played.


It was the sort of thing that was not rare in those days, but just wouldn't
happen today.


There is still no shortage of crappy recordings today.

Listening to original oldies from the 50s, whether classical or pop can
be a
lot of fun, but you don't do it for the high fidelity. Even the
so-called
SOTA recordings, RCA Red Seal for example, had a great many clearly
audible
flaws. I love the playing by the artists of the day, though. Toscanini
is
one of my favorites, but listening to him conducting is about the music,
not
the sound quality.


Ian has no comment about this and even trash-canned it, I wonder why?

Methinks the truth hurts. :-(

#


Methinks you talk BS.

Cheers

Ian
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Arny Krueger wrote:
"Eeyore" wrote in
message
Ian Bell wrote:

Arny Krueger wrote:
Standards for audio were a lot lower in the 50s, if you
didn't ever notice when you listened to a lot of
recordings from that time. There are some exceptional
recordings that still sound good, but in general, it
was not a good time for quality sound reproduction.
I would not say they were a lot lower. The flat
bandwidth extended only from 50Hz to 15KHz

i.e. totally crap.


but elsewhere the specs were close to today's.

********.


An RCA
broadcast console achieved a 68dB S/N ratio with a
-60dBm input signal which implies an equivalent input
noise of -128dBm


Cite ? A weighted by any chance ?


Here you go, Graham. As usual the tubies can't deliver what a few searches
with google turned up almost immediately:

http://sujan.hallikainen.org/Broadca.../index.php/RCA

Click on the manual for the RCA BC 7A. However, being stereo, this was not
a product of the 50s but rather one of the late 1960s.


If you check the my other posts you will see I cited the BC 6 series not
the one you chose and it was mono not stereo.

The actual spec on page 4 of the PDF is 68 dB below +18 dbm. IOW, only 50
dB below 0 dB. As bad as that is, I would suspect 50-15 KHz (- 3 dB)
weighting. The corresponding spec for a modern console would be about
twice that, IOW over 100 dB. (!!!!!!!!!!!!!!!!!!).


********. Work out the actual output noise of a 'modern' console with
68dB and show me how you get it to be -100dBm


Moving on to component chassic specs, such as those on page 15 (Figure 11)
we see the sad truth - noise level was -47 dBm, with THD speced at 1% over
a restricted frequency range. A modern component would have noise about -90
dBm, with THD no worse than 0.02%.

As usual, we're getting a humongous load of BS dropped on us. :-(


As usual you pick an example that suits your argument.

Cheers

Ian



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Arny Krueger wrote:

snip


Here you go, Graham. As usual the tubies can't deliver what a few searches
with google turned up almost immediately:

http://sujan.hallikainen.org/Broadca.../index.php/RCA

Click on the manual for the RCA BC 7A. However, being stereo, this was not
a product of the 50s but rather one of the late 1960s.

The actual spec on page 4 of the PDF is 68 dB below +18 dbm. IOW, only 50
dB below 0 dB. As bad as that is, I would suspect 50-15 KHz (- 3 dB)
weighting. The corresponding spec for a modern console would be about
twice that, IOW over 100 dB. (!!!!!!!!!!!!!!!!!!).

Moving on to component chassic specs, such as those on page 15 (Figure 11)
we see the sad truth - noise level was -47 dBm, with THD speced at 1% over
a restricted frequency range. A modern component would have noise about -90
dBm, with THD no worse than 0.02%.

As usual, we're getting a humongous load of BS dropped on us. :-(



Are you totally sure about that Arny???? I just checked out the
reference you cited above , the RCA BC-7A, that is the right one isn't
it? Because it is a TRANSISTOR console you idiot, - on Page 2 it says -
6 plug in transistorized amplifiers.

No we know it is YOU who talks BS.

Cheers

Ian

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"Ian Bell"

Lastly, the scope is a Rapid Electronics 7020A 20MHz dual channel (which
is a re-branded Pintek) and its -3dB point is quoted as 20Hz.



** Shame how that is just NOT so.

The 7020A has its -3dB point at ** 3.4 Hz ** when in "AC" input coupling
mode.

As is common practice with most scopes, a 47nF 400 volt film cap is placed
in series with the 1 Mohm input to each vertical amplifier :- f -3dB = 1
/ ( 2.pi.C.R)

Here is the schematic for the whole scope.

http://www.rapidonline.com/netalogue/specs/85-2200.pdf




....... Phil


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Phil Allison wrote:
"Ian Bell"
Lastly, the scope is a Rapid Electronics 7020A 20MHz dual channel (which
is a re-branded Pintek) and its -3dB point is quoted as 20Hz.



** Shame how that is just NOT so.

The 7020A has its -3dB point at ** 3.4 Hz ** when in "AC" input coupling
mode.

As is common practice with most scopes, a 47nF 400 volt film cap is placed
in series with the 1 Mohm input to each vertical amplifier :- f -3dB = 1
/ ( 2.pi.C.R)

Here is the schematic for the whole scope.

http://www.rapidonline.com/netalogue/specs/85-2200.pdf




Pity your comprehension skills are so poor. I quoted the manufacturers
spec. Clearly it is conservative. Thanks for the circuit.

Cheers

Ian
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"tubegarden" wrote in message
...
On Oct 31, 3:55 pm, Eeyore
wrote:

Junk.

Grow up and use solid state.

Graham



Hi RATs!


Eyesore poses proudly as a knowledgeable and clever adult.




"Things are seldom what they seem,
Skim milk masquerades as cream;
Highlows pass as patent leathers;
Jackdaws strut in peacock's feathers.

Very true,
So they do.

Black sheep dwell in every fold;
All that glitters is not gold;
Storks turn out to be but logs;
Bulls are but inflated frogs.

So they be,
Frequently"

This extract from the comic opera
"HMS Pinafore" by Gilbert and Sullivan
seems somehow appropriate. Don't you
agree, Al? :-)))

Regards
Iain





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"Ian Bell" wrote in message
...
Eeyore wrote:

Ian Bell wrote:

Eeyore wrote:
Ian Bell wrote:

Since there are untold preamp designs with unregulated
supplies
Bad preamps you mean ?
You tell me. I have the schematics for many broadcast consoles and
professional music mixers from the 50s that use unregulated supplies.


'Professional' has moved on a bit in 50+ years.


Has it really?

I doubt they'd match
decent cheap domestic kit now. This is one thing that freaks me out about
you tubeophiles,


Nothing to do with tubeophiles. Neumann tube mics are still much revered
by pros (as are many other tube mics), as are tube mic pres (just look at
the popularity of the EMI REDD 47)

you want to recreate the sound of half a century ago.


Quite possibly. Is there something fundamentally wrong with that?

Nothing at all. As a classical recording engineer with a special
interest in baroque music, I want to recreate the sound of 300
years ago!

Cheers
Iain




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"Arny Krueger" wrote in message
news
"Ian Bell" wrote in message


Arny Krueger wrote:
Other than a few very expensive microphones, the mics
were about as bad as the speakers.


Rubbish. Neumann mics were plentiful.


Correct

Hello? Is there any intelligent life in there? Neumann mics are and were
premium-priced and therefore only a tiny fraction of what is and was in
actual use.


Neumann mics were and still are ubiquitous in broadcast and professional
studio applications. The fact that the Baptist handcart recordist cannot
afford them has no bearing on the matter.

Iain



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"Eeyore" wrote in message
...


Ian Bell wrote:

Arny Krueger wrote:

Other than a few very expensive microphones, the mics were about as bad
as
the speakers.


Rubbish. Neumann mics were pentiful.


And VERY expensive which is what Arny said. Even 32 yrs ago I sold my U87
for
£400. They're about £1600 now new IIRC.

Graham



The *really* valuable Neumanns are the original U47, 49 and 50
some of which were supplied with a Telefunken badge for turnkey
installations.

They still sound wonderful. No-one parts with those.

Iain



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Phil Allison wrote:

"Eeysore the Congenital LIAR "

Not a problem with solid state you see.

PSRRs are typically in the 120dB region.

** Really?

On what planet is that ???

TL071 = 86 dB typ

NE5532 = 100 dB typ.


Both 30+ years old designs.


** Totally irrelevant.


Extremely relevant. TLs are rarely seen these days.

Graham

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Ian Bell wrote:

Eeyore wrote:
Ian Bell wrote:
Arny Krueger wrote:


Other than a few very expensive microphones, the mics were about as bad as
the speakers.
Rubbish. Neumann mics were pentiful.


And VERY expensive which is what Arny said. Even 32 yrs ago I sold my U87 for
£400. They're about £1600 now new IIRC.


So what? We are talking professional users here.


And £400 for a secondhand but fairly pristine mic was a small fortune in 1976.

So, only VERY EXPENSIVE mics from that era were any good. RE-20s weren't cheap
either. You are totally talking out of your rectum.

Graham

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Ian Bell wrote:

Eeyore wrote:
Ian Bell wrote:
Eeyore wrote:
Ian Bell wrote:
Eeyore wrote:
Ian Bell wrote:

Since there are untold preamp designs with unregulated
supplies
Bad preamps you mean ?
You tell me. I have the schematics for many broadcast consoles and
professional music mixers from the 50s that use unregulated supplies.
'Professional' has moved on a bit in 50+ years.
Has it really?


Beyond belief ! You're likely to find more Cat5 patch leads in a modern studio
than good old fashioned GPO / bantam patch leads.

Plus tape recorders (if present) usually sit around gathering dust. I know a
studio that has FIVE Studer 24 track A800s and they're almost never used. They
also have one of these.
http://www.ams-neve.com/Products/Mus...88RS/88RS.aspx

I doubt you'd find much of this in the 50s !
http://www.ams-neve.com/Home/Home.aspx

This was state of the art in the 60s !
http://vintageking.com/Shop-Used-Cat...I-Console-used



No ,that's no 'moved on' it is simply different.


MORON !

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