Home |
Search |
Today's Posts |
#81
Posted to rec.audio.tubes
|
|||
|
|||
Low Frequency Mains Noise
Ian Bell wrote: Methinks you talk BS. Well you certainly do IN SPADES |
#82
Posted to rec.audio.tubes
|
|||
|
|||
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
Posted to rec.audio.tubes
|
|||
|
|||
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
Posted to rec.audio.tubes
|
|||
|
|||
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
Posted to rec.audio.tubes
|
|||
|
|||
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
Posted to rec.audio.tubes
|
|||
|
|||
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
Posted to rec.audio.tubes
|
|||
|
|||
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
Posted to rec.audio.tubes
|
|||
|
|||
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
Posted to rec.audio.tubes
|
|||
|
|||
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
Posted to rec.audio.tubes
|
|||
|
|||
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
Posted to rec.audio.tubes
|
|||
|
|||
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
Posted to rec.audio.tubes
|
|||
|
|||
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
Posted to rec.audio.tubes
|
|||
|
|||
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
Posted to rec.audio.tubes
|
|||
|
|||
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
Posted to rec.audio.tubes
|
|||
|
|||
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
Posted to rec.audio.tubes
|
|||
|
|||
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
Posted to rec.audio.tubes
|
|||
|
|||
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
Posted to rec.audio.tubes
|
|||
|
|||
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
Posted to rec.audio.tubes
|
|||
|
|||
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
Posted to rec.audio.tubes
|
|||
|
|||
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
Posted to rec.audio.tubes
|
|||
|
|||
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
Posted to rec.audio.tubes
|
|||
|
|||
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
Posted to rec.audio.tubes
|
|||
|
|||
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
Posted to rec.audio.tubes
|
|||
|
|||
Low Frequency Mains Noise
Ian Bell wrote: My credibility is zero. You bet. Graham |
#105
Posted to rec.audio.tubes
|
|||
|
|||
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
Posted to rec.audio.tubes
|
|||
|
|||
Low Frequency Mains Noise
Eeyore wrote:
Ian Bell wrote: My credibility is zero. You bet. Graham Still greater than yours. Cheers Ian |
#107
Posted to rec.audio.tubes
|
|||
|
|||
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
Posted to rec.audio.tubes
|
|||
|
|||
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
Posted to rec.audio.tubes
|
|||
|
|||
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
Posted to rec.audio.tubes
|
|||
|
|||
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
Posted to rec.audio.tubes
|
|||
|
|||
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
Posted to rec.audio.tubes
|
|||
|
|||
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
Posted to rec.audio.tubes
|
|||
|
|||
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
Posted to rec.audio.tubes
|
|||
|
|||
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
Posted to rec.audio.tubes
|
|||
|
|||
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
Posted to rec.audio.tubes
|
|||
|
|||
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
Posted to rec.audio.tubes
|
|||
|
|||
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
Posted to rec.audio.tubes
|
|||
|
|||
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
Posted to rec.audio.tubes
|
|||
|
|||
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
Posted to rec.audio.tubes
|
|||
|
|||
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 | |
|
|
Similar Threads | ||||
Thread | Forum | |||
Modify Marantz 1050 amp to suppress mains noise | Tech | |||
300b DHT mains noise & speaker efficiency | Vacuum Tubes | |||
US/UK mains voltage/frequency | Pro Audio | |||
Low frequency Active Noise Cancellation | Tech |