Reply
 
Thread Tools Display Modes
  #81   Report Post  
Posted to rec.audio.tubes
Eeyore Eeyore is offline
external usenet poster
 
Posts: 8,474
Default Low Frequency Mains Noise



Ian Bell wrote:

Methinks you talk BS.


Well you certainly do IN SPADES

  #82   Report Post  
Posted to rec.audio.tubes
Eeyore Eeyore is offline
external usenet poster
 
Posts: 8,474
Default Low Frequency Mains Noise



Ian Bell wrote:

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.


What ****ing use is that ?

  #83   Report Post  
Posted to rec.audio.tubes
Phil Allison Phil Allison is offline
external usenet poster
 
Posts: 1,444
Default Ian Bell makes MORE dumb errors

"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.



** What a pile of sub human garbage you are - Bell.

Be a shame to make you into dog food cos dogs deserve better.


I quoted the manufacturers spec.



** Go on - prove that.

Post a link to it.

YOU LYING CRIMINAL **** !!!



Clearly it is conservative.



** More 100% ********



....... Phil



  #84   Report Post  
Posted to rec.audio.tubes
Phil Allison Phil Allison is offline
external usenet poster
 
Posts: 1,444
Default Eeysore =Congenital LIAR

"Eeysore = 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.



** More STUPID lies from a mentally defective, pommy ****.

Yawnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn .





....... Phil



  #85   Report Post  
Posted to rec.audio.tubes
Eeyore Eeyore is offline
external usenet poster
 
Posts: 8,474
Default Low Frequency Mains Noise



Iain Churches 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?

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!


They didn't even have wax cylinders back then.

Recreating the sound is trivial. As is recording it in true high fidelity too
now these days.

Graham



  #86   Report Post  
Posted to rec.audio.tubes
Eeyore Eeyore is offline
external usenet poster
 
Posts: 8,474
Default Low Frequency Mains Noise



Iain Churches wrote:

"Arny Krueger" 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 plentiful.


Correct


But astonishingly expensive which was Arny's point ! Arny (and me) 2 : others
ZERO.

Graham

  #87   Report Post  
Posted to rec.audio.tubes
Eeyore Eeyore is offline
external usenet poster
 
Posts: 8,474
Default Low Frequency Mains Noise



Iain Churches 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.

Graham


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


More audiophool nonsense inverse snobbery.


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


But not as good as a modern U87i

Graham

  #88   Report Post  
Posted to rec.audio.tubes
Eeyore Eeyore is offline
external usenet poster
 
Posts: 8,474
Default Eeysore =Congenital LIAR



Phil Allison wrote:

"Eeysore = 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.


** More STUPID lies from a mentally defective, pommy ****.


Name major serious manufacturers still using them in any quantity.
They're too bloody noisy for today's standards.

Graham

  #89   Report Post  
Posted to rec.audio.tubes
Patrick Turner Patrick Turner is offline
external usenet poster
 
Posts: 3,964
Default Low Frequency Mains Noise



Ian Bell wrote:

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.


OK, but its the amp noise we are concerned with.

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.


In my MC phono amp with j-fet input cascode plus µ-follower gain stage,
the LF gain at 20Hz is about 10,000x, or 80dB.
So 40uV of low bass signal becomes 400mV at the preamp output.
There is virtually no loss with the passive RIAA filter between the
cascode stage and following stage.
A signal of 0.4mV at 1kHz becomes 400mV at the output, and 4mV at 20kHz
also becomes 400mV at the output.

The RIAA filter has the effect of lowering the broadband noise of the
input stage as well as the noise from the vinyl.

Now when the amp is used with vinyl and turned up to good loud levels,
the noise of an unmodulated groove in the vinyl swamps the very low
amount of amplifier noise. If the arm is lifted off the record, there is
almost slence, and if the volume is turned up another 20dB to max, the
noise is a high pitched hiss with LF noise buried in there somewhere.
The j-fet gate is terminated at the input with the low impedance of the
MC cart bypassed with 470 ohms and 0.1uF in my case. ( You may wonder
why I have 0.1uF there, but it reduces the high distortion of high level
HF signals coming from the vinyl. The wanted HF content is unaffected. )

Now if you do the same test with an MM cart of 4mv 1kHz signal instead
of the 0.4mV with my MC, and with a 12AX7 input stage the noise of the
amp is barely below the noise of the unmodulated groove, but generally
quite low enough. If you lift the arm, and listen for noise, its low,
but present, and partly due to the 47k loading and higher cart
impedance. If the gain is turned up 20dB, the sound is a lower pitched
hiss with far more LF content because the tube input has much more
flicker noise than a j-fet. The overlall performance of the j-fet input
results in an unweighted SNR reduction of 20dB at least over what a good
12AX7 might ever do. Perhaps the j-fet performance is at least as good
as the tube with a step up tranny for MC, but i have never used a step
up tranny, so I cannot explain exact figures.
Denon invented the MC way back in 1949, and the DL103R cart is still
available and still well regarded, and I have one. Radio stations
preferred the MC because of better noise figures and possibly lower THD
and I sure found it better than MM Shure V15.

Broadband noise in phono amps is converted to noise with bandwidth of
very low F to 50Hz, the pole where the RIAA cuts off.
So the bandwidth is reduced by a factor of 50/20kHz = 1/400, and the
noise voltage becomes reduced by factor of the square root of the
bandwidth reduction, or 1/20 of the broadband noise. Noise below 100Hz
is less noticeable to the ear, so the noise we get with vinyl can be
weighted so in fact the noise with vinyl is rather good so all my pals
with record players say.

Vinyl isn't so good when the signal drops low on very quiet musical
passages, and then any hum if present or clicks and pops become real
irritating. But all the folks I know clean their records, and mostly
enjoy vinyl for jazz and the issue of noise doesn't exist and the sound
is usually better than cd versions of the same music from the same
master tapes.

Many commercially made integrated amps and preamps using solid state or
tubes I have had to work on have far worse noise performance than the
amps I have built. Often the response for each channel is very
different, and well away from the RIAA curve. Typical mass produced
crud! Hum levels are high, and if you examined the phono stage output
with a CRO, there you will see the trace flapping up and down to the LF
content from a poor amount of B+ filtering and complete absense of any
regulation.

I tried to measure the equivalent input noise of my MC amp with 2SK369
input. Seemed to me it was 0.14uV with gate to 0V.
It doesn't get much worse even with an unbypassed source resistance of
50ohms for MC.

The 2SK369 is a widely available j-fet with a slightly lower Pdd rating
than the identical 2SK147.
using them with Id = 5mAdc and Ed = 10Vdc gives gm = 40mA/V, and j-fet
input noise resistance is supposed to be proportional to 0.7/gm. With
triodes input noise resistance is proportional to 2.5/gm.

So its much more difficult to get a triode amp with high gain to have as
low an SNR as one with a humble tiny little j-fet at its input. In fact
the invention of the j-fet made tiny audio amps possible for use with
tiny microphones, and many have been used since in 1,001 spying
operations. Not all j-fets have high gm. Some have gm little better than
a 6AU6 or 6DJ8. But the 2SK369 has 10 times the gm, and as the formulas
above imply, EINR is 30 times lower than many tubes, and noise is at
least 1/sq.rt30 lower. The j-fets don't have as much LF noise as the
tubes. Mosfets on the other hand are not so good despite their much
highr gm. Lots of "popcorn noise".
Nobody uses a mosfet for a phono amp or mic amp input device.

Presumably, a transformer coupled microphone feeding a j-fet inputted
mic amp would give rather superb noise figures.



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.


Indeed it WILL make LF jitter much lower.

Consider 4k feeding 4,700uF, ( 10 x 470uF in parallel after a resevoir
cap.

The -3dB pole is at 159,000/4,700/4,000 = 0.0085Hz. If there was 5Vrms
of ripple at 100Hz at the resevoir C there'd be 0.423 mV at the 4,700uF.
If there was 5V of 1Hz ripple at the resevoir C, there would be 42.3mV
at the 4,700uF.

Now try having 4 sections of RC with 1k and 470uF. 1 section of 100Hz
ripple reduction factor will be 0.0034, and with 4 sections the ripple
reduction factor = 0.0034 x 0.0034 x 0.0034 x 0.0034 = 1.33 x 10 to the
-10.
You *will not* be able to measure 100Hz ripple. At 1Hz, the ripple
reduction factor of 1k and 470uF = 0.34, which isn't so hot, and after 4
filter sections is approximately 0.34 x 0.34 x 0.34 x 0.34 = 0.0134. So
with 5V at 1Hz at Cres, it becomes 0.0668V at the 4th filter cap.

The point of what I make is that with the same total amount of R, and
less capacitance, filtration of all F of concern is much better
because of the sectioning, but there is a limit of course to the
effectiveness of sectioning, for effective sectioning the ZC at the
wanted F should be ideally 1/10 of the preceding R in the R&C section.

Try doing the math with 4 sections using 100uF instead of 470uF. At 1Hz
ZC = 1,590 ohms, and 1Hz attenuation is barely 0.8,
and so after 4 sections attenuation is only maybe 0.5 times, so 5V of
1Hz at Cres is 2.5V after 4 sections.
So using 1k and 100uF just doesn't work. To be as good as the 470uF,
you'd need far more sections and a lot more R, and the voltage drop
across the extra R would be huge.

So try 3 sections of 1k2 plus 2x470uF, ie, 1k2 plus 940uF per section.
Each section has 1Hz attenuation = 0.141. # sections gives attenuation
of approximately 0.141 cubed, or 0.0028. So 5V at 1Hz at Cres becomes
14mV at C3.

In practice, you should find this to be plenty. The pole of each section
is 0.141 Hz, so after 3 sections the pole has moved down to around
0.07Hz, and by 1Hz, the rate of attenuation is 3rd order, so that
switching transients conveyed by mains F which contain many F will
severely flattened out. But DC is DC, and slow moving levels will still
get past you filter and the ONLY way to deal with them is with
regulation of some kind.



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.


Always have series R after the Cres and the regulator, or else the shunt
reg or series reg may be attempting the impossible.
Ideally, the Pd in the reg should equal the Pd in the preceding feeding
resistance when the wanted Idc flows.
So if Idc increases, Pd in the pass device becomes lower, and it
survives the heating.

Active regs using SS devices have to be designed with care to prevent
them fusing if shorts from input or output occur to 0V. You should be
able to short the in and out to 0V repeatedly with a bar and not damage
the reg.

Patrick Turner.

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

  #90   Report Post  
Posted to rec.audio.tubes
Patrick Turner Patrick Turner is offline
external usenet poster
 
Posts: 3,964
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.


** Another completely irrelevant reply.

Yawnnnnnnnnnnnnnn ...


But at least you are awake.

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.


Didn't you cite the effect of turning a heater here?

Don't let the details bother you.


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.


Not necessarily so. But cable length and its inductance and the COLD
resistance of the heater all work to make *some* change in mains voltage
amplitude. Depends on variables.

To best avoid the effects of the variables, regulation should be
employed, OK?

I for one live in a world where most gear I use can cope with mains
being between 235Vrms and 255Vrms because of its in-built regulation in
the case of PC PSU, CD player, TV set, all my oscilliscopes, and other
test gear, etc, and in a phono amp originally built in 1993. No reg in
power amps.

I dont have a B+ regulator in the same phono amp now which has excellent
LF stabiity in the output signal, see the PSU schematic 3/4 dowm the
page at http://www.turneraudio.com.au/preamp...ated-2006.html
There is a reg for the heater supply though, mainly because its so easy
and reliable to do at low V, and have low hum from heaters anywhere.
The B+ Vdc rails are *allowed to wander* up and own where they want.
Triode preamps can sustain wide variations of Vdc applied, and one with
a nominal B+ = 280Vdc will work with 350Vdc or 200Vdc.


While playing a record, I can turn off the phono amp and then back on
again and hear nothing.



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.


Er, what exact point are you making?

My point is that Vdc changes at the resevoir cap in a PS will change the
same % as the changes in Vac of the mains. But the rate of the change
will be different for Vdc at the end of a few sections of RC filtering
after the Cres because of the time constant involved.
Suddenly turning on a cold heater element won't cause a huge sudden Vdc
blip if the filtering has a long time constant. If the Vdc sags 1% or
10% because of a heater being turned on, then the rate of Vdc drop is
slow, and the idle Vdc electrode voltages at tubes and bias voltages
across coupling caps then all change but they can adjust slowly, and
there are no audible artifacts produced as a result because of the
enormous dynamic range of the tubes. Very slow signals are attenuated by
the RC couplings. And the point I make about my house is that a heater
used here does not cause a huge Vac change, and thus does not cause a
large Vdc change. My preamp without a B+ reg will work fine where mains
voltages are less well regulated than here.
In other houses with longer leads, perhaps much worse mains regulation
exists, ie, the output resistance of the wall plate outlets is much
higher than I have.

In 14 years of commercial operation I have never had any person tell me
that he has an audible fault which I found was as a direct result of LF
mains jitter and variations. I've repaired plenty of failed regs though,
and to make sure rates of B+ level change is harmlessly slow, I have
often removed ****y little 16uF caps and installed 470uF modern types.

Patrick Turner.



.... Phil



  #91   Report Post  
Posted to rec.audio.tubes
Patrick Turner Patrick Turner is offline
external usenet poster
 
Posts: 3,964
Default Ian Bell makes MORE dumb errors



Ian Bell wrote:

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


My 3 working oscillosopes have ac mode poles at about 3Hz. Having a pole
at 20Hz for ac mode would be substandard indeed.

Patrick Turner.
  #92   Report Post  
Posted to rec.audio.tubes
Patrick Turner Patrick Turner is offline
external usenet poster
 
Posts: 3,964
Default Low Frequency Mains Noise



Ian Bell wrote:

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


Ha ha, ha ha ha.....

Patrick Turner.
  #93   Report Post  
Posted to rec.audio.tubes
Peter Wieck Peter Wieck is offline
external usenet poster
 
Posts: 2,418
Default Low Frequency Mains Noise

On Oct 31, 6:01*am, Ian Bell wrote:
On several preamp PSUs I have built in that last couple of years I have
noticed the same thing. A very low frequency low level variation in the
output voltage. My latest PSU uses a series of five 100uF caps with 1K
resistors in between and it still exhibits this problem. The 'noise'
seems to be below 1Hz in frequency, fairly random and peaks typically
between +- 10mV with occasional excursions to +20 to 30mV.

Because the noise is so small, about the only place you can see it is on
the smoothed output with a scope set to ac input. I suspect this noise
is mains borne but I don't know how to see such small low frequency
signals on the mains itself. Any ideas what it is, how to look at it on
the mains and how to get rid of it?

Cheers

Ian


Mpfffffff....

Unregulated supply - that variation you are observing could be as
simply as your neighbor's refrigerator four houses down kicking in -
with a marginal starting cap on the compressor motor. Or, the hot-tub
motor & heater kicking in next door and surging to 40A or so. Or the
heat-pump on the roof. You get the picture.

See if it goes away if fed from a clean, regulated AC supply.

Peter Wieck
Melrose Park, PA
  #94   Report Post  
Posted to rec.audio.tubes
Arny Krueger Arny Krueger is offline
external usenet poster
 
Posts: 17,262
Default Low Frequency Mains Noise

"Iain Churches" wrote in message
.fi
"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.


Errr, not in the US.

There are at least a thousand or more TV and radio stations in the US that
have never had a Neumann, and never will.

It would probably be amazing to a Europeanista-white supremacist such as
your sweet self Iain; what creative, intelligent people can get done with
Shure, Electrovoice, Audix, and pacific rim branded microphones.

Even many of the major network affiliates in major US cities don't have any
Neumann mics, none at all.

I'm y kind of surprised that I see Neumanns on-the-air in major North
American productions as often as I do. For example, The standard vocalist
mic for American Idol (a show you no doubt despise) has been a Neumann KMS
105, if memory serves.

The KMS 105 is fine mic, I may buy one some day.

Despite your anti-religious bigotry Iain, spending money on ca. $500 mics
isn't against *my* religion. We've got a half-dozen Countryman E6s in
service, but I bet you don't even know what they are without looking them
up.

KMS 105s aren't that much more costly than E6s, but they are a vastly
different mic. Sort of retro at this point.

Nothing against Neumann at all, it is just that a lot more fruit drops
closer to the tree, and the Neumann trees are thousands of miles away from
the USA, in this case. Not a lot of AKGs in service around here, either.



  #95   Report Post  
Posted to rec.audio.tubes
Arny Krueger Arny Krueger is offline
external usenet poster
 
Posts: 17,262
Default Low Frequency Mains Noise

"Eeyore" wrote in
message
Iain Churches wrote:

"Arny Krueger" 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 plentiful.


Correct


But astonishingly expensive which was Arny's point ! Arny
(and me) 2 : others ZERO.


Actually, mics like the KMS 105 aren't that expensive. I could have bought 3
for not much more than I paid for my 6 Countryman E6s. Thing is, the 105s
would have been retro, while the E6s were strategic.




  #96   Report Post  
Posted to rec.audio.tubes
Arny Krueger Arny Krueger is offline
external usenet poster
 
Posts: 17,262
Default Low Frequency Mains Noise

"Ian Bell" wrote in message

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.


OK, so that leaves you short on proof. I seriously doubt that the BC6
outperformed the BC7, so point and match still belong to me.


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. (!!!!!!!!!!!!!!!!!!).


********.


Fact and presents as cited. It's clear that you didn't look at the factual
evidence I cited.

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


I measure it. The SNR of a typical cheap modern SS console is about 90 dB
below either 0 or +4. They can generally do +12 up to +18 or more before
clipping. That puts their SNR below clipping 100 dB, and that is being
conservative by 10 dB or more.

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.


Ian, you're still a day late and many dollars short of even a hand to play
in this game. Y

Ian, you can post a link to a PDF that compares to the document I provided
at your earliest convenience, or just apologize, bow out, and quit your
ludicrous whining, like a man.

Ohhh, I did say "like a man". I can safely predict that it won't happen.


  #97   Report Post  
Posted to rec.audio.tubes
Arny Krueger Arny Krueger is offline
external usenet poster
 
Posts: 17,262
Default Low Frequency Mains Noise

"Ian Bell" wrote in message

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'm sure that you haven't posted a link to a BC6 manual, yes I am.

Please quit whining and put up or shut up.


  #98   Report Post  
Posted to rec.audio.tubes
Arny Krueger Arny Krueger is offline
external usenet poster
 
Posts: 17,262
Default Low Frequency Mains Noise

"Iain Churches" wrote in message
. fi
"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!


So Iain why are you bothering with such *modern* entities as tubes. I have
it on good authority that there were no tubes in audio 300 years ago!

LOL!


  #99   Report Post  
Posted to rec.audio.tubes
Arny Krueger Arny Krueger is offline
external usenet poster
 
Posts: 17,262
Default Low Frequency Mains Noise

"Phil Allison" wrote in message

"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 ???


Earth in 2007-2008.

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) "



** Totally irrelevant.


????????????????????

Modern pro-audio gear is CHOCK full of them.


Yes, but most modern gear is low end and/or based on legacy designs.

You LYING piece of ****.


Ignoring the performance of SOTA equipment that is on the market and
generally available is deceptive.

On balance, why one *needs* 120 dB power supply rejection when $0.25 and
0.50 cent regulator chips produce DC power with just a few millivolts of
noise on it, makes this discussion kinda moot.


  #100   Report Post  
Posted to rec.audio.tubes
Ian Bell[_2_] Ian Bell[_2_] is offline
external usenet poster
 
Posts: 861
Default Low Frequency Mains Noise

Arny Krueger wrote:
"Ian Bell" wrote in message

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'm sure that you haven't posted a link to a BC6 manual, yes I am.

Please quit whining and put up or shut up.




Too late Arny. You have now twice demonstrated you have no idea of the
relationship between gain and noise and the second time you even managed
to confuse S/N with dynamic range. To cap it all you cannot even tell
the difference between a tube console and a transistor one when the
evidence is right in front of your eyes.

You credibility is zero.

Cheers

Ian


  #101   Report Post  
Posted to rec.audio.tubes
Iain Churches[_2_] Iain Churches[_2_] is offline
external usenet poster
 
Posts: 1,719
Default Low Frequency Mains Noise


"Eeyore" wrote in message
...


Iain Churches wrote:

"Arny Krueger" 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 plentiful.


Correct


But astonishingly expensive which was Arny's point ! Arny (and me) 2 :
others
ZERO.


Good mics have always been expensive, just like any tools of
high quality. Arny is living proof that one cannot make good
recordings with toyshop mics.


Cheers
Iain




  #102   Report Post  
Posted to rec.audio.tubes
Arny Krueger Arny Krueger is offline
external usenet poster
 
Posts: 17,262
Default Low Frequency Mains Noise

"Iain Churches" wrote in message
.fi
"Eeyore" wrote
in message ...


Iain Churches wrote:

"Arny Krueger" 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 plentiful.

Correct


But astonishingly expensive which was Arny's point !
Arny (and me) 2 : others
ZERO.


Good mics have always been expensive, just like any tools
of high quality.


Neumann mics are not merely "good mics". In the minds of almost everybody,
but a few who have never tasted the slings and arrows of normal life,
Neumann mics are as a rule excellent mics, or better.

You get an idea about who is speaking when you hear them saying arrogant
things like this. Basically, we're listening to someone who only understands
life at the absolute highest levels, someone who thinks that their routine
bodily functions produce no odor. They've had a very sheltered life and have
spent most of their time being waited on, hand and foot.

Take their advice at your risk, because they have no sense of perspective on
the real world.



  #103   Report Post  
Posted to rec.audio.tubes
Arny Krueger Arny Krueger is offline
external usenet poster
 
Posts: 17,262
Default Low Frequency Mains Noise

"Ian Bell" wrote in message

Arny Krueger wrote:
"Ian Bell" wrote in message

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'm sure that you haven't posted a link to a BC6 manual,
yes I am. Please quit whining and put up or shut up.


no link to BC6 manual provided after second request

That's all we need to know, Ian. You can neither put up nor shut up. Please
post again when you want to at least pretend to be a man. :-(


  #104   Report Post  
Posted to rec.audio.tubes
Eeyore Eeyore is offline
external usenet poster
 
Posts: 8,474
Default Low Frequency Mains Noise



Ian Bell wrote:

My credibility is zero.


You bet.

Graham

  #105   Report Post  
Posted to rec.audio.tubes
Ian Bell[_2_] Ian Bell[_2_] is offline
external usenet poster
 
Posts: 861
Default Low Frequency Mains Noise

Arny Krueger wrote:
"Ian Bell" wrote in message

Arny Krueger wrote:
"Ian Bell" wrote in message

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'm sure that you haven't posted a link to a BC6 manual,
yes I am. Please quit whining and put up or shut up.


no link to BC6 manual provided after second request

That's all we need to know, Ian. You can neither put up nor shut up. Please
post again when you want to at least pretend to be a man. :-(



There is no link to a BC6 manual - it is not available on the net.
You'll have to put your money where your mouth is and buy one Mr. Zero
Credibility.

Cheers

Ian


  #106   Report Post  
Posted to rec.audio.tubes
Ian Bell[_2_] Ian Bell[_2_] is offline
external usenet poster
 
Posts: 861
Default Low Frequency Mains Noise

Eeyore wrote:

Ian Bell wrote:

My credibility is zero.


You bet.

Graham


Still greater than yours.

Cheers

Ian
  #107   Report Post  
Posted to rec.audio.tubes
Iain Churches[_2_] Iain Churches[_2_] is offline
external usenet poster
 
Posts: 1,719
Default Low Frequency Mains Noise


"Eeyore" wrote in message
...


Iain Churches wrote:

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!


They didn't even have wax cylinders back then.


LOL :-) You totally miss the point.

I am interested to create and then faithfully record a
performance as Thomas Arne or Gabrielli might have
heard it.

Recreating the sound is trivial.


So you area expert in baroque instruments too?

As is recording it in true high fidelity too
now these days.


Sounds likes something a karaoke amp maker
might say:-)

Cheers
Iain




  #108   Report Post  
Posted to rec.audio.tubes
Iain Churches[_2_] Iain Churches[_2_] is offline
external usenet poster
 
Posts: 1,719
Default Low Frequency Mains Noise


"Ian Bell" wrote in message
...

Too late Arny. (snip)
Your credibility is zero.


In this fast-changing world, it is a comfort to know
that some things never change:-)



  #109   Report Post  
Posted to rec.audio.tubes
Iain Churches[_2_] Iain Churches[_2_] is offline
external usenet poster
 
Posts: 1,719
Default Low Frequency Mains Noise


"Eeyore" wrote in message
...


Iain Churches 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.

Graham


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


More audiophool nonsense inverse snobbery.


Not at all. People judge the recording by what they hear.
They can only fnd out the mics used by reading the (very)
small print on the CD,

If one could get the result with a cheap mic then Neumann
would be out of business.

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


But not as good as a modern U87i


Try a "new lamps for old" policy and see how far you
get :-) I doubt even 2 for 1 would get you any takers.


Cheers
Iain



  #110   Report Post  
Posted to rec.audio.tubes
Ian Bell[_2_] Ian Bell[_2_] is offline
external usenet poster
 
Posts: 861
Default Low Frequency Mains Noise

flipper wrote:
On Sun, 02 Nov 2008 11:30:36 +0000, Ian Bell
wrote:

flipper wrote:
On Sat, 01 Nov 2008 10:21:18 +0000, Ian Bell
wrote:

flipper wrote:
On Fri, 31 Oct 2008 11:01:16 +0000, Ian Bell
wrote:

On several preamp PSUs I have built in that last couple of years I have
noticed the same thing. A very low frequency low level variation in the
output voltage. My latest PSU uses a series of five 100uF caps with 1K
resistors in between and it still exhibits this problem. The 'noise'
seems to be below 1Hz in frequency, fairly random and peaks typically
between +- 10mV with occasional excursions to +20 to 30mV.

Because the noise is so small, about the only place you can see it is on
the smoothed output with a scope set to ac input. I suspect this noise
is mains borne but I don't know how to see such small low frequency
signals on the mains itself. Any ideas what it is, how to look at it on
the mains and how to get rid of it?
From what you describe it sounds like mains noise, as you suspected,
and with the thousands upon thousands of things running, coming on and
off, or whatever, throughout the grid lord only knows what causes each
'blip'. AC mains are neither 'clean' nor stable, at least not to the
degree you're talking about.

Indeed. However, I would have expected the transformer to attenuate
noise in the 1Hz region
You have a couple of dubious assumptions here with the first being
it's a 'separate' signal. It's more likely riding on the AC with the
AC acting as, essentially, a carrier.

Yes, of course, it's amplitude modulation caused by the varying overall
load - no wonder it gets through the transformer.

The second is that the AC 'noise' has the same frequency component as
your filtered measurement.

I don't think I was assuming that, only that it contained a component at
the frequency I meausured.


That goes without saying but the point I was getting at was your
mystification on how such a 'low frequency' could get through the
transformer. It riding on the AC carrier is one way but the noise
doesn't have to be 'low frequency' to give you a 'low frequency'
looking result after filtering. Like, for example, a transient surge
or a (relatively speaking) HF noise burst can cause a 'blip' that,
after filtering, will look like a 'LF' blip because that's the filter
response.


Agreed. It should have been obvious but for some reason it just did not
occur to me.


Of course, I'm just speculating but it doesn't really matter what the
cause is because you have no control over it. I mean, even if you
could track it down to surges from a local water pumping station it's
not like they're going to redesign the things, or rearrange the power
grid, for your preamp.


Indeed. However, at first I was not certain if it was mains borne. It
might have been noise generated by the electrolytics themselves for all
I knew.

plus the five stage RC filter I am using is over
120dB down at 50Hz so even a decade or so lower I would have expected
its attenuation to be significant.
I'm sure it is 'significant', which gives you an idea of just how bad
it is on the AC mains itself. It isn't a 10mV blip out there.

Which means I could probably see it on the mains side - where's that
scope probe?


Maybe. But you don't really know what to look for nor, since you say
it's random, 'when' to look.


Indeed. I have now built a new smoothing section with a 470uF reservoir
followed by five RC stages of 1K and 470uf each and the LF noise is now
below the broadband noise.

Cheers

Ian

With it out of band and low I'm not sure what you're trying to fix but
the common choices are to filter till it's below whatever tolerance
you decide upon or regulate.

I wreaks havoc with distortion measurements at 100Hz when you are
expecting a result below 0.1%.
Sounds like maybe a measurement problem because out of band signals
shouldn't be in the measurement.

Cheers

Ian



  #111   Report Post  
Posted to rec.audio.tubes
John Byrns John Byrns is offline
external usenet poster
 
Posts: 1,441
Default Low Frequency Mains Noise

In article ,
"Arny Krueger" wrote:

"Iain Churches" wrote in message
.fi

Neumann mics were and still are ubiquitous in broadcast
and professional studio applications.


Errr, not in the US.


Oh come on Arnie, I spent the first half of the 1960s working in broadcasting,
in the US, and we used Neumann capacitor and RCA ribbon mics exclusively in the
studios. A few RCA moving coil types were used for voice type remotes, while
Neumann capacitor mics were used on musical remotes.

--
Regards,

John Byrns

Surf my web pages at, http://fmamradios.com/
  #112   Report Post  
Posted to rec.audio.tubes
John Byrns John Byrns is offline
external usenet poster
 
Posts: 1,441
Default Low Frequency Mains Noise

In article ,
Ian Bell wrote:

Arny Krueger wrote:

no link to BC6 manual provided after second request

That's all we need to know, Ian. You can neither put up nor shut up. Please
post again when you want to at least pretend to be a man. :-(



There is no link to a BC6 manual - it is not available on the net.
You'll have to put your money where your mouth is and buy one Mr. Zero
Credibility.


Or he could simply look it up in an RCA catalog of the era, although it was my
observation that the specs. for much of this type of equipment was grossly
understated. The specs seem to have been written around FCC technical
requirements of the time, e.g. 50 Hz to 15 kHz frequency response, and 60 dB
signal to noise ratio, as well as typical broadcast industry operating practices
like 18 dBm output levels. While the specs. provided some margin relative to
requirements, the actual operating performance was generally considerably better
than spec., also allowing for aging and etc.

--
Regards,

John Byrns

Surf my web pages at, http://fmamradios.com/
  #113   Report Post  
Posted to rec.audio.tubes
Arny Krueger Arny Krueger is offline
external usenet poster
 
Posts: 17,262
Default Low Frequency Mains Noise

"John Byrns" wrote in message

In article
, "Arny
Krueger" wrote:

"Iain Churches" wrote in message
.fi

Neumann mics were and still are ubiquitous in broadcast
and professional studio applications.


Errr, not in the US.


Oh come on Arnie, I spent the first half of the 1960s
working in broadcasting, in the US, and we used Neumann
capacitor and RCA ribbon mics exclusively in the studios.


Interesting how John how you worked in enough different stations during 5
years to be able to characterize what was ubiquitous in *all* radio and TV
stations in the U.S..

A few RCA moving coil types were used for voice type remotes,


Voice remotes were pretty common. Of course RCAs are not Neumann, but thanks
for sharing.

while Neumann capacitor mics were used on musical remotes.


That tips your hand John, because only a tiny minority of broadcast stations
have ever even done musical remotes. Most of them were done by stations in
cities with a symphony orchestra of note. I'm guessing you worked in Boston
or New York.


  #114   Report Post  
Posted to rec.audio.tubes
John Byrns John Byrns is offline
external usenet poster
 
Posts: 1,441
Default Low Frequency Mains Noise

In article ,
Patrick Turner wrote:

Denon invented the MC way back in 1949, and the DL103R cart is still
available and still well regarded, and I have one. Radio stations
preferred the MC because of better noise figures and possibly lower THD
and I sure found it better than MM Shure V15.


Are you sure the MC cartridge wasn't around before 1949? I built my first MC
cartridge as a teenager in the mid 1950s.

--
Regards,

John Byrns

Surf my web pages at, http://fmamradios.com/
  #115   Report Post  
Posted to rec.audio.tubes
John Byrns John Byrns is offline
external usenet poster
 
Posts: 1,441
Default Low Frequency Mains Noise

In article ,
"Arny Krueger" wrote:

"John Byrns" wrote in message

In article
, "Arny
Krueger" wrote:

"Iain Churches" wrote in message
.fi

Neumann mics were and still are ubiquitous in broadcast
and professional studio applications.


Errr, not in the US.


Oh come on Arnie, I spent the first half of the 1960s
working in broadcasting, in the US, and we used Neumann
capacitor and RCA ribbon mics exclusively in the studios.


Interesting how John how you worked in enough different stations during 5
years to be able to characterize what was ubiquitous in *all* radio and TV
stations in the U.S..


Sorry, I didn't mean to imply that they were "ubiquitous", I was simply trying
to point out that they were used in broadcasting in the US, the place I worked
being an example.

A few RCA moving coil types were used for voice type remotes,


Voice remotes were pretty common. Of course RCAs are not Neumann, but thanks
for sharing.

while Neumann capacitor mics were used on musical remotes.


That tips your hand John, because only a tiny minority of broadcast stations
have ever even done musical remotes. Most of them were done by stations in
cities with a symphony orchestra of note. I'm guessing you worked in Boston
or New York.


I was born in Boston if that counts, however that is not where I worked with the
Neumann mics. Don't forget that there are probably hundreds of University towns
with symphony orchestras, and many smaller towns have local "pops" type
orchestras. Also there is a whole spectrum of music beyond symphony orchestras
that you are ignoring. I remember some great stereo remotes a smaller AM-FM
combo station in town did with visiting California jazz bands in the late
1950's, prior to the advent of the stereo disc.

--
Regards,

John Byrns

Surf my web pages at, http://fmamradios.com/


  #116   Report Post  
Posted to rec.audio.tubes
Phil Allison Phil Allison is offline
external usenet poster
 
Posts: 1,444
Default Op-amp PSRR figure = fake


"Arny Krueger"
"Phil Allison"

PSRRs are typically in the 120dB region.

** Really?


On what planet is that ???


Earth in 2007-2008.



** Completely false that is it a *** TYPICAL *** figure !!!!!!!!


Modern pro-audio gear is CHOCK full of them.


Yes, but most modern gear is low end and/or based on legacy designs.



** Irrelevant, ridiculous DRIVEL



Ignoring the performance of SOTA equipment that is on the market and
generally available is deceptive.


** Got even the faintest idea what the word ** TYPICAL ** means ??

Need a dictionary ????


On balance, why one *needs* 120 dB power supply rejection when $0.25 and
0.50 cent regulator chips produce DC power with just a few millivolts of
noise on it, makes this discussion kinda moot.



** The figures quoted in op-amp spec tabes for PSRRs are VERY
MISLEADING - as they quote only the DC test result. You have to find a
maker HONEST enough to publish a graph of PSRR over the full frequency
range, like Natsemi do for their LF351 - which is near identical to TI's
TL071.

http://cache.national.com/ds/LF/LF351.pdf

Notice how the table figure for PSRR falls at * 20 dB per decade * from
about 10 Hz up !!!!!!!!!!!

The range near 10 kHz is important for audio circuits and you can see the
*ACTUAL* PSRR is a mere *40 dB* for the negative supply rail.

Perfectly possible for negative supply rail regulator noise to inject itself
into the op-amp at a noticeable level.

Smart audio designers use local R/C filtering on the DC rails to eliminate
the problem.

Obviously not congenital, masturbating dopes like Graham Stevenson who
cannot even read a data sheet.



...... Phil




  #117   Report Post  
Posted to rec.audio.tubes
Patrick Turner Patrick Turner is offline
external usenet poster
 
Posts: 3,964
Default Low Frequency Mains Noise



Ian Bell wrote:


snip,


plus the five stage RC filter I am using is over
120dB down at 50Hz so even a decade or so lower I would have expected
its attenuation to be significant.
I'm sure it is 'significant', which gives you an idea of just how bad
it is on the AC mains itself. It isn't a 10mV blip out there.

Which means I could probably see it on the mains side - where's that
scope probe?


Maybe. But you don't really know what to look for nor, since you say
it's random, 'when' to look.


Indeed. I have now built a new smoothing section with a 470uF reservoir
followed by five RC stages of 1K and 470uf each and the LF noise is now
below the broadband noise.


With the pole at 0.34Hz for each section, final -3dB with 5 sections is
about 0.07Hz and attenuation at 3Hz = 75dB approx.

If the Vdc tries to rise 10% in 10 seconds, then your filter won't stop
it. If one wave takes 40 seconds its 0.025Hz,
and such LF should not affect your amp.


Patrick Turner.
  #118   Report Post  
Posted to rec.audio.tubes
Patrick Turner Patrick Turner is offline
external usenet poster
 
Posts: 3,964
Default Low Frequency Mains Noise



John Byrns wrote:

In article ,
Patrick Turner wrote:

Denon invented the MC way back in 1949, and the DL103R cart is still
available and still well regarded, and I have one. Radio stations
preferred the MC because of better noise figures and possibly lower THD
and I sure found it better than MM Shure V15.


Are you sure the MC cartridge wasn't around before 1949? I built my first MC
cartridge as a teenager in the mid 1950s.


I am 99% sure that Denon invented the MC. Maybe a google search will
proove me wrong though.
It sure wasn't Shure.

Patrick Turner.

--
Regards,

John Byrns

Surf my web pages at, http://fmamradios.com/

  #119   Report Post  
Posted to rec.audio.tubes
Iain Churches[_2_] Iain Churches[_2_] is offline
external usenet poster
 
Posts: 1,719
Default Low Frequency Mains Noise


"John Byrns" wrote in message
...
In article ,
"Arny Krueger" wrote:

"Iain Churches" wrote in message
.fi

Neumann mics were and still are ubiquitous in broadcast
and professional studio applications.


Errr, not in the US.


Oh come on Arnie, I spent the first half of the 1960s working in
broadcasting,
in the US, and we used Neumann capacitor and RCA ribbon mics exclusively
in the
studios. A few RCA moving coil types were used for voice type remotes,
while
Neumann capacitor mics were used on musical remotes.

--


Hi John. I have worked on many transatlantic
projects with material recieved from and sent to
the US. The session sheets invariably list large
numbers of Neumann mics.

Due to their cost, they are probably not found often in the
mic cupboard of project studios, but they do seem to be
the microphone of choice in professional recording and
broadcasting the world over.

Iain

PS. What do you mean by the term "musical remote" ??
An IR controller/musical box hybrid comes to mind:-)
Is it what we in the Anglo Saxon world call a "location
recording" ?








  #120   Report Post  
Posted to rec.audio.tubes
Arny Krueger Arny Krueger is offline
external usenet poster
 
Posts: 17,262
Default Low Frequency Mains Noise

"Iain Churches" wrote in message
.fi

Hi John. I have worked on many transatlantic
projects with material received from and sent to
the US. The session sheets invariably list large
numbers of Neumann mics.


So Iain, how many of those projects took place in the 1950s?


How many took place in the 1950s and involved radio or TV stations?








Reply
Thread Tools
Display Modes

Posting Rules

Smilies are On
[IMG] code is On
HTML code is Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Modify Marantz 1050 amp to suppress mains noise Toby Newman Tech 23 January 31st 08 06:59 AM
300b DHT mains noise & speaker efficiency Stoat Vacuum Tubes 6 July 1st 05 05:03 AM
US/UK mains voltage/frequency [email protected] Pro Audio 16 April 7th 05 08:56 AM
Low frequency Active Noise Cancellation Audiophil Tech 16 March 17th 04 09:46 PM


All times are GMT +1. The time now is 10:51 AM.

Powered by: vBulletin
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 AudioBanter.com.
The comments are property of their posters.
 

About Us

"It's about Audio and hi-fi"