Unable to get good signal to noise ratio - what's the issue?

[RockDiedin2005]

Hi everyone, brand new member here.

I'm trying to get decent vocal recordings out of the humble gear I have: a Shure SV100 > Steinberg CI1 audio interface / preamp > PC running Ableton Live.

The problem is that I can't get a usable signal-to-noise ratio, despite both the mic and the interface having published specs that ought to be workable.

Here's a shot of the noise floor's EQ profile with the mic on, 10 feet from the PC mounted on a sturdy floor stand,and the interface's gain set to just 40%:

https://i.imgur.com/2kNJqCB.jpg

I'll also post what it looks like with the preamp gain set to 75%, because at 40%, I need to basically shout into the mic to get any good levels.. 75% is where I can get good levels comfortably (but the noise is completely audible):

https://i.imgur.com/Sd5HOcZ.jpg


Is that normal?

Let me note the troubleshooting I've already gone through:

- testing different gain levels (anything lower and my voice barely registers)
- turning off electronics, heat, wifi (only turning off a nearby floor lamp made a difference)
- mic placement, angle, and coverage (placing a sound-absorbing blanket between it and the PC, even covering it on all sides with towels, etc did not improve things)

It's clear that there's a 60hz buzz with all multiple harmonics as tonal noise, but there's also some kind of broadband noise that you can see repeating every 1500hz in the EQ profile above - what is that? And as for the 60hz buzz, let me emphasize that all my gear (that is, the PC) is connected solely to one wall outlet, so this is definitely not a ground loop issue.

I appreciate any responses. Here's hoping someone can make my day!

 

[ecc83]

Welcome RD!
Hmm? That mic is about 6dB more sensitive than a 57/58 and the C11 has a good name for its preamps (even if it is a rip! No MIDI) and plenty here use 57's to good effect. My son actually likes one on acoustic guitar via an A&H ZED10.

What is the noise level like from the headphone socket monitoring direct, i.e. NOT thru' the PC?

If that is clean then you have a USB noise issue, usually caused by having Windows gain far too high. With my ZED 10 (if I used the USB side. I don't) I have W7 gain down at 5% or less.
This of course means that you need the preamp gains cranked, probably to or near max (the Z10 is nearly maxed out).

The graphs are a bit "dim". Can you attach an MP3 test? Best Q, 320k, mono is fine.

Dave.

 

[Bobbsy]

Looking at your graphs, the first thing I note is that you have your biggest noise spike at 60 Hz and then the rest of the noise isn't just a standard noise floor--instead it's a whole series of little spikes. This would lead me to guess that the source of your noise is mains related--which is bad news because the exact issue can be hard to diagnose--anything from something in your computer power supply to earthing problems on your mains supply.

 

[ecc83]

Not that it should make a bit of diff' but...The C 11 comes with Cubase, might be worth a try?

Dave.

 

[bouldersoundguy]

Are you using a known working XLR-XLR cable? Hopefully you're not using an XLR-1/4" cable.

 

[RockDiedin2005]

Thanks everyone for the suggestions!

ecc83 - I tried turning the level of the interface down in Audio > Recording Devices > Steinberg > Properties > Level. Unfortunately, it didn't affect the buzz either way. Is there another way to change the device gain in Windows?

> What is the noise level like from the headphone socket monitoring direct, i.e. NOT thru' the PC?

Could you explain a bit more what you mean here? I can only plug in headphones either to the interface (which is connected to the PC), or the PC (but then I won't be able to hear the sounds being routed through the interface, including the mic).

> Not that it should make a bit of diff' but...The C 11 comes with Cubase, might be worth a try?

Mine came with Sequel LE and Wavelab LE, not Cubase.
I do have Pro Tools Essential lying around somewhere, but I'd be shocked if it's the DAW introducing any noise, to be honest.

Bobbsy - Even with the PC unplugged and running off battery (there's no other equipment connected to the wall), the buzz is there. In fact, when I disconnected the power supply, the buzz actually went UP, believe it or not.

bouldersoundguy - Yes, the mic came with an XLR-1/4 cable, but I'm using a real XLR cable.

Here are two more shots of the noise. This is with preamp gain at just 33%, which is the minimum to even get a signal. I then applied gain in the DAW just to make it easier to see.

 

[ecc83]

"bouldersoundguy - Yes, the mic came with an XLR-1/4 cable, but I'm using a real XLR cable."

Aha! It is entirely possible that the mic is internally wired as unbalanced. The logical way to use a mic on a TS jack lead is wire the XLR end pin 3 to pin one but I have found that very often this is done inside the mic, a moments work with a meter on the XLR pins will prove this.

As for the headphone test. There is I am sure a "direct monitoring" facility on the AI? This shunts the A to D converter directly to the D to A converter, so called "zero latency monitoring". Thus the computer has no influence on the signal.

Pretty sure it is the mic now, they are quite cheap, under £30 here.

Dave.

 

[RockDiedin2005]

Update - I went back and tried using the XLR>TRS cable included with the mic, and it does not suffer the 60hz+harmonics buzz.

I also found that the XLR cable would not pick up as much hum if I did two things: picked the cable up off the floor, and touched the metal connector "shield" around the end that plugs into the mic. This solidified it as a problem with the cable. Not shielded? It was the cheapest XLR I could find, so I'm not surprised. But I wonder if what you, ecc83, said has to do with it:

"Aha! It is entirely possible that the mic is internally wired as unbalanced. The logical way to use a mic on a TS jack lead is wire the XLR end pin 3 to pin one but I have found that very often this is done inside the mic, a moments work with a meter on the XLR pins will prove this. "

Would this mean I should stick with the XLR-TRS, or try a better-quality XLR? Either way I am going to return the XLR as defective.. it should not be picking up so much noise like that.. it was advertised as "low-noise" and "shielded".

 

[gecko zzed]

Would this mean I should stick with the XLR-TRS, or try a better-quality XLR? Either way I am going to return the XLR as defective.. it should not be picking up so much noise like that.. it was advertised as "low-noise" and "shielded".

It really means get a better quality mike.

You are not likely to get your money back on the XLR to XLR because they will test and find, in all likelihood, that there is nothing wrong with it. As Dave said, the problem most likely resides within the mike itself.

 

[bouldersoundguy]

Time for a meter.

 

[ecc83]

Time for a meter.

Yeah, I KNOW I keep banging on about this and about people getting some electrical smarts but getting a $10.00 digital multimeter really does save both the noob and the rest of us SO much time!

I am slightly bemused by the OP's reference to a "TRS" plug on the supplied lead? If indeed it is such then the whole setup should be balanced but of course the AI's combi input jack will be the line input and that will have nothing like enough gain and also be noisy.

It is not at all beyond the bounds of possibility that the mics ARE wired unbalanced but are shipped (from the far east!) with XLR-TRS leads!

Any chance of a smudge of the jack plug Scoop? (and the aforementioned MP3?)

Dave.

 

[ecc83]

I found a .pdf manual for the V100 series mics on the Shure site and they show a line drawing of two leads.

One is definitely a TS "mono" jack plug (UK usage!) to XLR3 and the other XLR3-XLR3. Now that would imply that the mic IS wired balanced.................But I wouldn't BET on it!

Dave.

 

[gecko zzed]

Any chance of a smudge of the jack plug Scoop? (and the aforementioned MP3?)

Blimey, what does that mean? I'm glad I'm not the OP; I wouldn't have a clue.

 

[ecc83]

Blimey, what does that mean? I'm glad I'm not the OP; I wouldn't have a clue.

"Smudge"? Sweeney slang for a photo and all reporter/photographers were called Scoop in the Rado-land of Dick Barton!

Sorry!
Dave.

 

[mjbphotos]

It really means get a better quality mike.

From the Shure site;
Ideal for spoken-word presentations, karaoke performances, multimedia, and instrument use, the SV100 includes a durable cable with ¼" (6.3 mm) plug for use with home or portable recording/karaoke systems.
It's a $30 mic ...

 

[RockDiedin2005]

It really means get a better quality mike.

You are not likely to get your money back on the XLR to XLR because they will test and find, in all likelihood, that there is nothing wrong with it. As Dave said, the problem most likely resides within the mike itself.

As I said, I tested another cable which did not suffer the same 60 hertz + harmonics noise, and the level of noise changes depending on where the cable is and whether or not I touch it. That proved it's the cable's fault. Of course I will get my money back.

Time for a meter.

Yeah, I KNOW I keep banging on about this and about people getting some electrical smarts but getting a $10.00 digital multimeter really does save both the noob and the rest of us SO much time!

I am slightly bemused by the OP's reference to a "TRS" plug on the supplied lead? If indeed it is such then the whole setup should be balanced but of course the AI's combi input jack will be the line input and that will have nothing like enough gain and also be noisy.

It is not at all beyond the bounds of possibility that the mics ARE wired unbalanced but are shipped (from the far east!) with XLR-TRS leads!

Any chance of a smudge of the jack plug Scoop? (and the aforementioned MP3?)

Dave.

- What uses does a digital multimeter have? If it's really so useful then sure, I will pick one up. Any particular one you'd recommend?

Let me clarify further about the mic: it has a XLRM connection and came packaged with a XLRF-1/4" TS cable. The plug goes into the AI's combo jack, which is set to Mono, no phantom, no hi-Z.

From the Shure site;
Ideal for spoken-word presentations, karaoke performances, multimedia, and instrument use, the SV100 includes a durable cable with ¼" (6.3 mm) plug for use with home or portable recording/karaoke systems.
It's a $30 mic ...

Yes, it's cheap.. Cheap =/= Bad. If it's to be used for spoken word, the sort of loud hum I described earlier would be considered intolerable for that application. I already determined that the noise is NOT coming from the mic - see my earlier post.

Edit: here's a photo of the jack as requested.



Edit 2: Yes, I see now that it's a TS jack, not TRS...

So if this mic was designed to be used with unbalanced cables, what should I use for the best possible signal?

 

[VomitHatSteve]

From the Shure site;
Ideal for spoken-word presentations, karaoke performances, multimedia, and instrument use, the SV100 includes a durable cable with ¼" (6.3 mm) plug for use with home or portable recording/karaoke systems.
It's a $30 mic ...

Yeah, sounds like the problem is a cheap mic.

"Aha! It is entirely possible that the mic is internally wired as unbalanced. The logical way to use a mic on a TS jack lead is wire the XLR end pin 3 to pin one but I have found that very often this is done inside the mic, a moments work with a meter on the XLR pins will prove this. "

Would this mean I should stick with the XLR-TRS, or try a better-quality XLR? Either way I am going to return the XLR as defective.. it should not be picking up so much noise like that.. it was advertised as "low-noise" and "shielded".

I don't remember the exact wiring and physics of it, but I believe a "balanced" connection means you have two wires in the cable carrying the same signal in such a way that electromagnetic interference in one wire is cancelled out by the same interference in the other. This means that both the source (the mic) and the receiver (the interface) need to be wired to accept a balanced signal. A cheap mic might just leave one of the wires disconnected on the mic side. It's not carrying the signal; it doesn't cancel interference from radio stations/electronics; you get noise.

Is the original cable (the XLR to TRS) actually tip-ring-sleeve, or is it just tip-sleeve. If the latter, then they definitely didn't intend for you to have a balanced signal.

 

[RockDiedin2005]

Yeah, sounds like the problem is a cheap mic.



I don't remember the exact wiring and physics of it, but I believe a "balanced" connection means you have two wires in the cable carrying the same signal in such a way that electromagnetic interference in one wire is cancelled out by the same interference in the other. This means that both the source (the mic) and the receiver (the interface) need to be wired to accept a balanced signal. A cheap mic might just leave one of the wires disconnected on the mic side. It's not carrying the signal; it doesn't cancel interference from radio stations/electronics; you get noise.

Is the original cable (the XLR to TRS) actually tip-ring-sleeve, or is it just tip-sleeve. If the latter, then they definitely didn't intend for you to have a balanced signal.

I edited my above post just before yours, after finding that the original cable is just tip-sleeve. Since that's the case, what does that mean exactly? I wouldn't expect balanced cables to sound worse (noisier) than unbalanced, but they won't sound any better, correct? How much of a difference would it make to get a mic built for balanced connections?

For comparison, here's the noise level when using the XLR-TS cable under the same conditions as the shoddy XLR shown above: (Clearly, this shows the mic doesn't introduce an unacceptable level of noise. No 60hz+multiples buzz.)

 

[Bobbsy]

In an ideal situation, (short run, correct wiring, no electrical noise around, etc.) there should be no audible difference between a balanced and unbalanced circuit.

However, in a less than ideal situation an unbalanced circuit will pick up problems much more quickly than a balanced equivalent. The situation is even more risky with an unbalanced microphone since anything on the cable (audio signal AND noise) is going to be amplified by 50dB or so in your mic pre amp. Add in the fact that it's very easy to have "funnies" in the cable. There's not a single correct way to wire such an adaptor cable--it depends a bit on what you're feeding it into.

Finally, to be blunt, the only gear you're going to own that's going to need such a conversion is going to be very cheap and nasty...and prone to problems. Even the most basic mic and usb interface combo is going to be balanced throughout.

So, yeah, the theory is that an unbalanced circuit wouldn't sound worse is sort of true. The practice, however, is full of pitfalls and I fear you've fallen into one.

Finally, in answer to your question about multimeters, the main use in our context is simply to check that the proper pins are connected at both ends of a cable (and, sometimes more important, that some pins are NOT connected to each other). As you get more confident and do a little reading, you can also check things like the presence and voltage of phantom power, a rough look at levels on sources, that sort of thing. I can't recommend a brand other than to say just go to Radio Shack or hop onto eBay and buy something cheap. I have an expensive one I use at home for repairs, construction projects, etc. but for the basic stuff, the one I bought 12 years ago in Maplins UK for five pounds still works fine.

 

[ecc83]

"Is the original cable (the XLR to TRS) actually tip-ring-sleeve, or is it just tip-sleeve. If the latter, then they definitely didn't intend for you to have a balanced signal. "

This is the crazy, illinformed thing about some cheap mics. They supply a TS lead and the female XLR tother end is wired as unbalanced, i.e. pin one and pin three strapped and pin two "hot" and tip.

That is fine (sort of) for some jobs but they then confound the felony by wiring the mic's XLR male the same way! They do not need to do this! The cable does the "unbalancing" the mic could be left as standard. If you had a meter. pins 2 and 3 would read low Ohms, maybe 100 or more but most importantly they would NOT read anything to pin one, i.e. infinity.

I have bought quite a few cheap mics for use in a garden for the birds (wrapped in clingfilm they last about 3-6 months) and most have been wired in this unbalanced way.

Dave.