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Post by johneppstein on Nov 15, 2017 11:21:40 GMT -6
Notice how he turned on psu without the mike attached and hot swapped it: doubt the cap likes that ? Also, wouldn’t you want to let the tube warm up and blow off some electrons to have a better sense of what the mike really sounds like ? That would definitely be a problem with an original U47 but today we have solid state regulation and the power supplies we use have zener regulation on the plate supply and a 6v regulator on the filament. The modern power supplies that we use and Bryce would be using are fully regulated so the filament is up to temperature within a minute and the regulator holds it within + and - 2%. The last U47 I restored took 50 minutes before the filament and plate supply came up to 105V. With regulation you can hot swap the microphones as the supplies voltage don't vary under different loads (mike connected/no mike connected). Cheers, Dave How does the modern power supply affect the sound of the mic? If I'm not mistaken, either Klaus or Dave Bock said on another forum that power supply mods, swaps, or upgrades will affect the sound of vintage mics like the Neumann U47s
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Post by Ward on Nov 15, 2017 11:59:12 GMT -6
Exception to that! Some of my old tube mics have tube powered or regulated power supplies and they do indeed 'ramp up'. Sure, a tube regulated supply will ramp, a ramp can be put in but many do not. A non-regulated will have a degree of ramp. There re arguments for and against. Some tubes and capsules seem to wear better when ramped up and down. Others brown out from such. Likewise the 'shock' isn't good for some capsules and tubes with a PSU that doesn't have any ramp to it. But as always... YMMV
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Post by aamicrophones on Nov 15, 2017 16:56:15 GMT -6
That would definitely be a problem with an original U47 but today we have solid state regulation and the power supplies we use have zener regulation on the plate supply and a 6v regulator on the filament. The modern power supplies that we use and Bryce would be using are fully regulated so the filament is up to temperature within a minute and the regulator holds it within + and - 2%. The last U47 I restored took 50 minutes before the filament and plate supply came up to 105V. With regulation you can hot swap the microphones as the supplies voltage don't vary under different loads (mike connected/no mike connected). Cheers, Dave The regulated power supplies will provide more consistentcy between microphones, it is not unusual for a vintage tube supply to vary plus or minus 10%. The U47 schematic calls for 105v but the last U47 I serviced has a voltage up at 117v after warm up and I had increase the resistor values slightly in the supply to bring it down to 105v. This is not a tube guitar amplifier or power amp or even a tube compressor. Its just a single tube which with a maximum current draw of about 3ma. The U47 circuit is unique to itself with the filament supply and tube plate supply sharing the same supply voltage and path to ground. The U47 actually draws around 42ma give or take the tolerances. 40ma is need to supply the filament current. In the Warm 47 it will have a separate 6v dc filament supply like our microphone circuits and the plate supply will be upwards of 125v. The U47 circuit was designed to ramp up extremely slowly to protect the filament. Today we run the 6v filaments from a solid state regulator which is separate from the plate (audio) supply. So, power supply upgrades, swaps and mods could affect the U47 depending on where the voltage sits after the large wire wound resistor in the U47 heats up. How does the modern power supply affect the sound of the mic? If I'm not mistaken, either Klaus or Dave Bock said on another forum that power supply mods, swaps, or upgrades will affect the sound of vintage mics like the Neumann U47s
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Post by aamicrophones on Nov 15, 2017 17:07:03 GMT -6
The filament in a tube will ramp up naturally. When the voltage is put across a filament it has a high resistance as current starts to flow, the resistance of the "tungsten" filament starts to decrease as it warms up.
No current can flow through the tube until the filament heats up the cathode enough for it to emit electrons that can now flow from the negative cathode to the postive plate. The signal grid is like a tap that control how much current flows through the tube.
Cheers, Dave aamicrophones.com
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Post by EmRR on Nov 15, 2017 17:16:23 GMT -6
All the really antique crap ran on batteries: instant on. Yet considered superior in many camps.
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Post by jakeharris on Nov 15, 2017 22:33:55 GMT -6
Take any crappy China PSU, and measure the B+ pin when you switch it on. It will take upto 10 seconds for the supply to get in the region of 120V, steadily ramping up. No instant on. Then switch it off, and see how it takes 5-10mins for it to reach zero.
Plus when you hot plug you're hoping the ground connects first. What if the heater or B+ line connects first, and you're holding the mic in your hand? You don't have to go very far either: there's people on this forum who've already been zapped by mics.
I just don't see the point of dicking around with lethal current, or pointlessly shocking tubes and circuits. It's lazy...
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WARM WA-47
Nov 15, 2017 23:54:16 GMT -6
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Post by kcatthedog on Nov 15, 2017 23:54:16 GMT -6
Maybe me being a little paranoid but when I built my mk-u47,friends here really cautioned me around the voltages and it was tricky getting continuity for the cap and I had some bad tubes. All that said, once it was dailed in,I treated my 47 very carefully and it worked flawlessly. I was just very surprised to see him power psu and hot swap
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Post by johneppstein on Nov 16, 2017 0:57:18 GMT -6
The filament in a tube will ramp up naturally. When the voltage is put across a filament it has a high resistance as current starts to flow, the resistance of the "tungsten" filament starts to decrease as it warms up. No current can flow through the tube until the filament heats up the cathode enough for it to emit electrons that can now flow from the negative cathode to the postive plate. The signal grid is like a tap that control how much current flows through the tube. Cheers, Dave aamicrophones.com Yes, I know all that, I spent decades as an amp tech. However you still haven't answered my question. I'm assuming you know who Klaus and David are?
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Post by aamicrophones on Nov 16, 2017 2:59:46 GMT -6
The filament in a tube will ramp up naturally. When the voltage is put across a filament it has a high resistance as current starts to flow, the resistance of the "tungsten" filament starts to decrease as it warms up. No current can flow through the tube until the filament heats up the cathode enough for it to emit electrons that can now flow from the negative cathode to the postive plate. The signal grid is like a tap that control how much current flows through the tube. Cheers, Dave aamicrophones.com Yes, I know all that, I spent decades as an amp tech. However you still haven't answered my question. I'm assuming you know who Klaus and David are? Hi John, sorry there was a birthday party starting up around me as I was writing that and I got distracted!!! I also got the facts reversed, the filament resistance starts low and increase as it heats up. The 5654W for example draws 200ma at 6.3v and would have a resistance of 31.5 ohms fully lit but when its cold it measures 5.3 ohms. This still creates a ramp up affect. I know who Klaus and Dave are. I think they are referring to new supplies that have a high current filament supply with a separate low current plate supply. If your U47 supply fails you can't just re-wire it to the new more common low plate current power supplies. 1) Neumann series the filament supply of the U47 with the plate supply and it will draw 4 times more current than the plate current alone. 2) The filter capacitors must also be larger because the total current draw will be much higher than a plate current only supply. For, example our power supply can be set for 105 volts to run a U47 but all the resistors have to be lower in value and the capacitor values increased to supply the extra current required for the filament. Also, I believe Klaus and Dave might be referring to the unregulated power supply dropping its voltage with extreme current draws. Because the filtering in the U47 supply is a network of resistors and capacitors then the voltage drop across these resistors will increase as the current draw from the tube increases. So, as you push the level through the tube the plate supply can drop slightly reducing the output level but I think this effect would be ultra subtle in a single tube circuit with only a 10ma draw? The power supply was designed to deliver 50ma and I don't think varying just the plate supply a few milliamps would not change the supply voltage significantly to be audible? Its also a trade-off, the U47 supply voltage will vary with any variation in the A/C voltage supply from the wall plug. A regulated supply can hold the voltage consistent and is less suseptible to A/C input variations. So, the regulated supply will provide a more consistent sound in studios suceptible to brown-outs. I believe the un-regulated to regulated power supply considerations has less consequence in a low current single plate circuit than other components in the microphone build. For, example to get the low frequency response to match you must use a .5ufd coupling capacitor so there is an early LF roll-off and a slight resonance created by the .5ufd and the inductance of the BV8. Paying strict attention to the response of each capsule is also very important. The capsule needs to measure between 78pf and 83pf according to the schematic. The other consideration is that the back-plate voltage and the rear diaphragm voltage are exactly the same in cardiod. If there is 60v on the rear diaphragm then there should be 60v on the backplate. If the rear diaphragm polarization voltage is lower than the back-plate then the pattern will be wider Cardiod. If the rear diaphragm polarization voltage is higher than the back-plate voltage then the pattern will be a tighter cardiod. The U47 has passive polarization so that the rear diaphragm connection is left hanging in Cardiod and is not energized. In our CM48T tube microphone we combine the Fig8/Cardiod of the U48 and the OMNI/Cardiod of the U47 and keep the passive polarization method of both the U48 and U47. However, I also love the extra feature that our 9 pattern supplies provide just like the WA47 does but its imperative that the rear diaphragm and back-plate are at the same potential for true cardiod. Cheers, Dave
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Post by jakeharris on Nov 16, 2017 4:40:53 GMT -6
However, I also love the extra feature that our 9 pattern supplies provide just like the WA47 does but its imperative that the rear diaphragm and back-plate are at the same potential for true cardiod. Even when the rear and backplate voltages are perfectly matched, it sounds different to front only true-cardioid. I've tried this by connecting a rear diaphragm directly to the backplate, for exactly the same voltage on both. Still didn't fully cancel out the rear. Only way to get true-cardioid is by leaving the rear out of circuit. M49's have an internal switch just for this purpose.
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Post by cowboycoalminer on Nov 16, 2017 8:53:37 GMT -6
That would definitely be a problem with an original U47 but today we have solid state regulation and the power supplies we use have zener regulation on the plate supply and a 6v regulator on the filament. The modern power supplies that we use and Bryce would be using are fully regulated so the filament is up to temperature within a minute and the regulator holds it within + and - 2%. The last U47 I restored took 50 minutes before the filament and plate supply came up to 105V. With regulation you can hot swap the microphones as the supplies voltage don't vary under different loads (mike connected/no mike connected). Cheers, Dave How does the modern power supply affect the sound of the mic? If I'm not mistaken, either Klaus or Dave Bock said on another forum that power supply mods, swaps, or upgrades will affect the sound of vintage mics like the Neumann U47s I can't speak to this in a 47 but I had a wonderful 67 with both the original and a modern supply. There was a slight difference but to me it was negligible. I always used the modern because it seemed to bring out more of the top. And on a 67, squeezing out as much highs as possible is a good thing.
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Post by aamicrophones on Nov 16, 2017 15:02:20 GMT -6
However, I also love the extra feature that our 9 pattern supplies provide just like the WA47 does but its imperative that the rear diaphragm and back-plate are at the same potential for true cardiod. Even when the rear and backplate voltages are perfectly matched, it sounds different to front only true-cardioid. I've tried this by connecting a rear diaphragm directly to the backplate, for exactly the same voltage on both. Still didn't fully cancel out the rear. Only way to get true-cardioid is by leaving the rear out of circuit. M49's have an internal switch just for this purpose. Hi Jake, thanks for your reply. Yes, that is why we use the passive polarization method in our CM48T which leaves the back diaphragm disconnected but gives you the U47 and U48 options with OMNI & FIG8. You are right even a regulated power supply takes nearly 10 seconds for the power supply voltage to stabilize but this is a lot better than the 50 plus minutes it takes a U47 power suppy to normalize. As, I previously stated, the filament has to warm up first so no plate current will flow until the filament gets the cathode up to temperature. The filament starts as a low resistance and then ramps up as it starts to light up. You certainly can get zapped if you hold onto the body of the microphone and the metal of the XLR when you hot swap it. However, it won't kill you as it can't deliver enough current through you high resistance skin but it can catch your attention. Proper protocol is to plug the microphone in first and then turn on the supply. However, when I am working on microphones in the shop its too time consuming to power off the supply 50 times a day. I have learned to plug the XLR in while holding the rubber strain relief. I am working on a design like the M49 for my new CM49LE which will feature a switched passive Cardiod option as well as the standard 9 pattern option. Cheers, Dave
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Post by EmRR on Nov 16, 2017 22:57:50 GMT -6
In a U-47 clone, the capsule and tube are pretty well isolated from hot-swapping voltages given the scale of resistances that must be passed through. The capsule likewise draws no current. The Chinese mic supplies I've checked out are incapable of much current at all, thus the 'ramp', and they aren't regulated outside of a zener string maintaining a max voltage, so long as current doesn't go up. Disconnect the pattern control total load of 1M5ish and current changes; that's a weak supply! Agree with Dave, that lack of current capability leaves one with a device that will get your attention in a zap, very doubtful an actual hazard. Dave actually went further into this in another thread.
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Post by Vincent R. on Nov 22, 2017 16:56:40 GMT -6
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Post by Vincent R. on Nov 25, 2017 22:22:15 GMT -6
Spoken audio, but hey it's a sample.
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Post by c0rtland on Nov 26, 2017 0:48:27 GMT -6
"It's a very big microphone, therefore it gives a big sound."
Genius.
I wonder what will be next? I'm gonna guess a 1073.
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Post by kcatthedog on Nov 26, 2017 4:53:51 GMT -6
I’ve been saving my pennies and am not holding my breath:)
Well seems the delivery was unscripted and informal but that comment was in the context of characterizing the sound quality but in the context of the triple layer mesh, which essentially acts like a combo eq and delay,the transformer and tube ?
I had the feeling Bryce was thinking about people who might not know why and how a tube mike sounds different ?
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Post by c0rtland on Nov 26, 2017 5:25:00 GMT -6
I’ve been saving my pennies and am not holding my breath:) Well seems the delivery was unscripted and informal but that comment was in the context of characterizing the sound quality but in the context of the triple layer mesh, which essentially acts like a combo eq and delay,the transformer and tube ? I had the feeling Bryce was thinking about people who might not know why and how a tube mike sounds different ? I know, slightly unfair. In context of talking about the grill it seems valid. I just couldn't help myself.
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Post by kcatthedog on Nov 26, 2017 5:58:16 GMT -6
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Post by Deleted on Nov 26, 2017 6:49:57 GMT -6
ok, Warm 47 or AA 47 - nice problem to ponder (warm is £100 more expensive over here).
Also wonder what the new release will be - Fairchild? STa?
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ericn
Temp
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WARM WA-47
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Post by ericn on Nov 26, 2017 10:50:27 GMT -6
Spoken audio, but hey it's a sample. I'm so afraid to even click on these clips by my old employer, always afraid I'm just going to want to 🤢 barf!
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ericn
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Post by ericn on Nov 26, 2017 10:52:05 GMT -6
ok, Warm 47 or AA 47 - nice problem to ponder (warm is £100 more expensive over here). Also wonder what the new release will be - Fairchild? STa? I like Warm, but for the service Dave is willing to give it's a no Brainer!
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Post by plinker on Dec 20, 2017 9:31:25 GMT -6
I want to know how they are keeping the noise at 11 dBA?? What's the secret?
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Post by wiz on Dec 23, 2017 1:08:42 GMT -6
A friend just sent me a sample of him singing into it, cardoid, a couple of inches back.
It sounded really good.. absolutely no sibilance... as to whether it is equal to a 47 dunno... but hearing it... and for the price its at, seems like really good value...
cheers
Wiz
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Post by Johnkenn on Dec 23, 2017 13:49:41 GMT -6
The filament in a tube will ramp up naturally. When the voltage is put across a filament it has a high resistance as current starts to flow, the resistance of the "tungsten" filament starts to decrease as it warms up. No current can flow through the tube until the filament heats up the cathode enough for it to emit electrons that can now flow from the negative cathode to the postive plate. The signal grid is like a tap that control how much current flows through the tube. Cheers, Dave aamicrophones.com Yes, I know all that, I spent decades as an amp tech. However you still haven't answered my question. I'm assuming you know who Klaus and David are? I'm assuming you know who Dave is?
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