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SteveG Location: United Kingdom Posts: 6695	Posted - Thu Feb 13, 2003 3:24 pm  You may recall reading these exchanges in another thread: Quote: There is an SOS review of the Samson C01 which basically quite likes it (apart from the slightly higher self-noise level). And it is, by any standards, a pretty cheap mic, and you seem to get quite a lot for the money. I'm not sure what actually causes the higher self-noise in this case - there are actually several possibilities. Almost worth getting one to find out... Me Quote: Wow, you weren't kidding about that price! I've put it on my list for budget mic's (at the bottom, until I see more reviews). At any rate, for a street price of around $70 I probably won't be too disappointed, and certainly would find some use for it. Thanks for the tip. Post78 So when I was offered one for even less than the quoted price, I decided to get one. So what can I tell you now? Well, I think that SOS have been rather kind about the noise problem... but the sound from it is actually pretty good, on a brief listen-to. But back to the noise. I wondered if it was me, or the mic pre, or whatever... it's like listening to a mic with a built-in hiss generator! Okay, I compared it with some pretty classy competition (the AKG C12 capsule was a little unfair!) but even in comparison to the JoeMeek JM47 (which is also a pretty good mic, admittedly), it was pretty bad. In fact, it's so noisy that I took it to bits to try to discover why. If we assume that the capsule itself is okay, which it probably is, then you have to look at the impedance converter, that being the most sensitive part of the circuitry, essentially hanging straight off the back of the capsule. And I must say that I am not impressed with the FET they've used. It's a 2SK105 - cooking variety. Now it just so happens that I've got some similar, but rather better FETs specced to a much lower noise figure, so I'm going to put one of them in and see what the difference is. And this time, I'm going to measure the actual self-noise values before and after, so we'll see what changing just one component in the mic for one that's actually designed to do the job does to the performance. I must admit that I'll be a bit cross if this is all that the problem is, because these FETs are not expensive, and it would only have made a few pence or cents difference to the production cost to get it right in the first place. Watch this space... _________________
SteveG Location: United Kingdom Posts: 6695	Posted - Thu Feb 13, 2003 3:28 pm  Oh, and one other trivial (or is it?) thing: It's got a blue LED on the front to indicate when the phantom power is on. And this thing nearly takes your eye out! _________________
zemlin Location: USA Posts: 1156	Posted - Thu Feb 13, 2003 3:38 pm  SteveG wrote: It's got a blue LED on the front to indicate when the phantom power is on. And this thing nearly takes your eye out! If you're going to be inside the thing with a soldering iron, I suspect you can remedy that issue as well. _________________ Karl Zemlin - www.cheap-tracks.com Host of the World Wide Cool Edit Collaboration Procedural Debate
VoodooRadio Location: USA Posts: 3971	Posted - Thu Feb 13, 2003 3:39 pm  Hey SteveG, I am curious about your progress here, so keep us posted. I'm thinking that if the FET's that your using make a marked improvement AND... they are affordable, then purchasing a "handfull" of both the mics and the FET's and doing a "modification" might be a worthwhile venture. _________________ I said Good Day! Voodoo
SteveG Location: United Kingdom Posts: 6695	Posted - Thu Feb 13, 2003 4:04 pm  Okay, a couple of things before I even get there... Yes, I think that a higher-value resistor in series with the LED might be a good thing... I'm also slightly suspicious about the phantom power in the mic itself, judging from what happened when I switched it off. This gets the scope on it... When you get the levels matched up, the other point to note (courtesy of the B&K measuring amp) is that the output is quite hot. When you get the output level identical with the reference mic, the noise floor difference between them is about 4dB A-weighted, which means that in real terms, it's actually slightly worse than this. But anyway, things aren't necessarily quite as bad as I thought, although they could still be improved, I think. _________________
SteveG Location: United Kingdom Posts: 6695	Posted - Fri Feb 14, 2003 2:18 am  Update: Changing the FET has certainly improved things, but not to the extent that I'm happy with. Fortunately, disassembling the mic to the point where the PCB is exposed is easy - one big clamping ring at the base holds the case on, and that's it. The next stage was to remove the four screws that clamp the PCB frame to the capsule mounting, which doesn't allow you to separate them, but does let the top come off, revealing the capsule in all its glory. And acoustically, they've used just about every trick in the book. They've got an equalising ring around the outside of it, and an equalising plate over the diaphragm itself. And the backplate is also partially pressure-relieved. And if you asked me whether this was a pressure or pressure-gradient mic, I couldn't honestly tell, because it seems to be a combination of both! (although realistically, it is pressure-operated) So the next stunt is to run this capsule with some different electronics, ie an AKG body, which is known to have a forgiving, quiet impedance converter and see how this compares. We may be in interesting territory with either the capsule or the electronics, and I can't tell which unless I do this slightly bizarre experiment... More later. It will be a while, not because this takes long to do, but because I have a pile of work to complete, and this gets investigation gets fitted into processing time. _________________
SteveG Location: United Kingdom Posts: 6695	Posted - Fri Feb 14, 2003 6:35 am  Oh, you will love this bit... So I stick the capsule output onto the AKG body. Nothing. Nada. I get suspicious, and put an AKG CK1 capsule on the body, and it works fine... I put the Samson capsule back onto their electronics, and it still works fine. Now, I know that this lot is obeying the laws of physics, so it must be me. Anyway, I take the capsule off again and have a good look around. More importantly, I traced out the FET input circuit... And discovered that there is no high-voltage polarising feed to the mic - there's no DC continuity at all, in fact. Just a capacitor coupled to the gate of a FET with a 510Mohm bias resistor. But it works. Ergo, there is only one possible conclusion - this is a back-electret capsule, and not a 'proper' externally polarised one at all. And so I do all the checks to see if this is the case, and it is. When I look caerfully at the backplate, it even looks like a back electret type - I'm amazed that I didn't spot this earlier! So now we have some explanations. Back-electrets are pretty good, but they never manage quite the same noise figures that externally polarised mics do. So I checked on Samson's website, and nowhere do they actually confirm the capsule type - they just say that it has a 'large 19mm diaphragm'. So miracles are not going to occur with this mic. And just to cap it all, you can't reduce the LED brightness, because they are using the LED as part of a biasing circuit! But it has a sturdy case, and works well enough. And now I know why it's the price that it is... _________________
post78 Location: USA Posts: 2887	Posted - Fri Feb 14, 2003 12:42 pm  And just like that (*snap*), it's off my list. Gracias mi amigo. So, where can I purchase the Garnett tester? I could use [t:537ea45201]on[/t:537ea45201] one of those on my work bench. _________________ Answer = 1. Probably.
SteveG Location: United Kingdom Posts: 6695	Posted - Fri Feb 14, 2003 1:56 pm  Yes, it's great, isn't it? I've now got the best-sounding Samson C01 Back Electret large 19mm diaphragm mic in the world... but I've got one more little mod to try next week when the new batch of seriously high-value resistors arrive. I have a moderately good idea about why electrets are generally noisier than 'normal' capsules, and I'm going to see if I can't actually improve on the figure some more by a slightly different approach. This is all to do with capsule loading effects, and if I can reduce these by a significant amount, things may yet get quieter. You have to bear in mind that even as it stands, the sound of this mic isn't bad - I may post a file at some stage so you can have a listen. (just in case you wondered what seriously high-value resistors are, these particular ones are 1Gohm, but I can actually get them with values up to 50Gohms as chipmounts, which is ridiculous!) _________________
SteveG Location: United Kingdom Posts: 6695	Posted - Fri Feb 14, 2003 1:58 pm  post78 wrote: And just like that (*snap*), it's off my list. Gracias mi amigo. So, where can I purchase the Garnett tester? I could use [t:1d80a3de03]on[/t:1d80a3de03] one of those on my work bench. It's only available for rent, and this is very expensive, normally! _________________
VoodooRadio Location: USA Posts: 3971	Posted - Fri Feb 14, 2003 3:50 pm  Thanks for the research SteveG! _________________ I said Good Day! Voodoo
SteveG Location: United Kingdom Posts: 6695	Posted - Fri Feb 14, 2003 3:58 pm  Just to give you some sort of an idea, I have a few pix: This is the front and the rear of the Samson back-electret capsule... the concentric ring around the outside both alters the polar response, and the onset point of the proximity effect, which is directly related to the audio path length around the microphone. The 'large 19mm diaphragm' is actually contained within the inner circle, which is rather more apparent from the rear view. And for comparison purposes, this is the rear of an AKG CK1 capsule - note the clean lines - not like the Samson! Of course, this is a 'proper' externally polarised capsule... And if you think that the pictures look a bit crappy, please bear in mind that they were all done with an Agfa flatbed scanner! _________________
ozpeter Location: Australia Posts: 3200	Posted - Fri Feb 14, 2003 5:02 pm  I think we should club together to buy you a digital camera - but then you might take it to bits to try to improve it.... :) More seriously, the pics look fine the other side of the world, and although I have no plan to buy any mic at present, your research is none the less fascinating, especially as mics are about the one thing around the house that I wouldn't dare disassemble. - Ozpeter
SteveG Location: United Kingdom Posts: 6695	Posted - Fri Feb 14, 2003 5:13 pm  It's not so bad for me - I've been repairing, modifying and building them for years. What isn't so good now is that I have to do most of it under a pretty powerful bench magnifier. But I'm getting used to that, and in some ways, it's actually making things easier. I've always found them to be fascinating - they contain elements of just about everything - acoustics, electronics, compromises and sometimes some real surprises. And when they are working fine, I don't take them to bits! One day when I have the strength, I'll tell you about SWMBO and the digital camera saga... _________________
SteveG Location: United Kingdom Posts: 6695	Posted - Tue Feb 18, 2003 5:38 pm  SteveG wrote: ...but I've got one more little mod to try next week when the new batch of seriously high-value resistors arrive. I have a moderately good idea about why electrets are generally noisier than 'normal' capsules, and I'm going to see if I can't actually improve on the figure some more by a slightly different approach. This is all to do with capsule loading effects, and if I can reduce these by a significant amount, things may yet get quieter. So now I have an impedance converter with a higher value capsule load (more voltage output from the mic) and a quieter FET. So the tradeoff between higher noise from the load resistor and the quieter FET sort-of balances out, but we have more output from the capsule (there's plenty of headroom, so no problems with this), and there is now a quieter, smoother BG, sound from the mic. I'd say that there is a relative lack of bass output compared to other similar mics. This isn't necessarily a bad thing, as it happens - it's still there, just rolled off. The noise is still a little higher than the C12, but nowhere near as bad as it was. So for an extra £2.40/$3.00, it's possibly the quietest C01 around... _________________
ozpeter Location: Australia Posts: 3200	Posted - Tue Feb 18, 2003 5:58 pm  Now I wonder whether you could soup up a couple of Sony 979's I have here? Maybe you should give up the day job?! (And no, I didn't stir the tea with them...) - Ozpeter
SteveG Location: United Kingdom Posts: 6695	Posted - Tue Feb 18, 2003 6:33 pm  Soup up a 979? They are supposed to be pretty good mics anyway! I have a couple of ECM s959C mics (this is the two-capsule version with slightly less bass extension) which go pretty well now that I've replaced the output cables. But I thought that the 979 actually had a proper connector, so you won't presumably have that problem... But once again, we're in good electret territory! _________________
ozpeter Location: Australia Posts: 3200	Posted - Tue Feb 18, 2003 6:53 pm  Quote: Soup up a 979? They are supposed to be pretty good mics anyway! If you compare them with (for instance) a Sennheiser MKH series (mono) mike they seem to come up quite noisy, but under real-life conditions I have to admit that given their low cost for a 3-capsule MS stereo mic, they aren't that bad - in fact many years back I recorded a classical piano CD with one, and it was well received. ('It ain't what you've got, it's what you do with it that counts'). Now I always carry one in my location recording bag as a backup to my Sennheiser mics and to my Sennheiser MS psu/preamp, as the 979 works on batteries. I think the current and presumably improved version is the 999. If you put its fat windshield on, from a distance people think you're using a Soundfield mic.... They have a 5 pin xlr connector, and for years I've used stereo starquad cable with similar connectors for stereo pairs - saves running out two lengths of cable. Somewhat awkward to solder the connectors to, however, as the overall cable size looks handy for running a cooker on. But it's very sturdy for hanging down from the roof of a big concert hall. - Ozpeter (in rabbiting mode)
SteveG Location: United Kingdom Posts: 6695	Posted - Tue Feb 18, 2003 7:01 pm  Quote: If you put its fat windshield on, from a distance people think you're using a Soundfield mic.... I can see what you mean about the windshield (v.similar to 959 one), but the rest of the current Soundfield mic body has quite a distinctive 'V' shape. I would quite like one of these! The cluster on the left is the Soundfield stuff, just in case this isn't clear! And obviously not to scale, just in case anybody was seriously wondering! _________________
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