Focusrite 18i20 3rd Gen Issue

[BobbyP]

Any thoughts on how to fix or explain this. I am on my second unit that I bought direct from Focusrite recently. When go to record a voice track I get a very weak (one green bar) input level/signal on the Focusrite unit. I'm using a brand new Elecro-Voice RE20 mic and I have to crank the control to almost max on the interface and be 1/2" away from the mic. This was trouble shot through Focusrite and they simply replaced the unit after a lot of hit and miss suggestions. Now the same thing is happening with the replacement unit and I'm now wondering if it is another issue. I'm able to do what I need to do but it seems extreme to crank the unit and swallow the mic. Thanks ahead everyone, Cheers, Robert

 

[TalismanRich]

Its not really extreme. The RE20 only has 1.5mv/Pascal output which is lower than the SM57, but slightly higher than the SM7B. Both of those are often paired with something like a Cloudlifter or Triton FetHead. These unit provide around 20-25dB of gain so you don't need to boost the gain on your interface. It's a common enough situation that Shure recently introduced the SM7dB which incorporates a Cloudlifter circuit into the microphone. This boosts the input to be more similar to that seen with condenser microphones.

These inline preamps generally use the 48V phantom power to run the circuit.

The question that needs to be answered is if using an inline preamp gives you a better S/N ratio than just turning up the knob. There's nothing at all wrong with turning up the interface if the noise level is sufficiently low at that level. You might watch this video explaining how gain must be considered with both the noise and signal.



You can also try recording with the gain knob being up, and with it being reduced and normalizing (digitally boosting) the signal, then compare the noise of the two.

 

[TalismanRich]

Also check out this video by Julien.

 

[rob aylestone]

Because I’m lazy, when I record announcement style stuff in the office, not the studio, because that’s forty feet away, I have a short XLR dangling from input one on my old Tascam. On a scale of 1 to 10 over 8 brings in proportionally more noise, so the knob sits permanently at 7.5 and in cubase, that is a mere tickle on the waveform display and a flicker up to half scale or so. Normalise to -3dB works much better than turning the gain up. However, I’ve got some dirt cheap inline preamps and they do the job even better, and they’re really cheap and actually really good. It seems such a simple thing to do, adding pretty noise free mic gain, but the manufacturers design their preamps to cope with people singing close and loud or guitars on condenser mics, not people reading scripts at two feet, or recording ants farting! It’s not a modern thing either. In the seventies, my Ferrograph reel to reel and an SM57 let me record bird song outside my window, even with tape hiss to get over!

 

[drtechno]

Any thoughts on how to fix or explain this. I am on my second unit that I bought direct from Focusrite recently. When go to record a voice track I get a very weak (one green bar) input level/signal on the Focusrite unit. I'm using a brand new Elecro-Voice RE20 mic and I have to crank the control to almost max on the interface and be 1/2" away from the mic. This was trouble shot through Focusrite and they simply replaced the unit after a lot of hit and miss suggestions. Now the same thing is happening with the replacement unit and I'm now wondering if it is another issue. I'm able to do what I need to do but it seems extreme to crank the unit and swallow the mic. Thanks ahead everyone, Cheers, Robert

The focusrite mic pre is a medium impedance mic pre made for condenser microphones like most of these cheaper interfaces. That is why they started making booster amps that have lower input impedance. You could use a separate mic pre, but you need to get one that has an input impedance of 1500 ohms or less but some 2K preamps like those small Behringer mic preamps work good too. This microphone never has gain issues in its normal settings, but that is because mixing boards are around 1.2K to 1.5K input impedance (or lower).

 

[drtechno]

Its not really extreme. The RE20 only has 1.5mv/Pascal output which is lower than the SM57, but slightly higher than the SM7B. Both of those are often paired with something like a Cloudlifter or Triton FetHead. These unit provide around 20-25dB of gain so you don't need to boost the gain on your interface. It's a common enough situation that Shure recently introduced the SM7dB which incorporates a Cloudlifter circuit into the microphone. This boosts the input to be more similar to that seen with condenser microphones.

These inline preamps generally use the 48V phantom power to run the circuit.

The question that needs to be answered is if using an inline preamp gives you a better S/N ratio than just turning up the knob. There's nothing at all wrong with turning up the interface if the noise level is sufficiently low at that level. You might watch this video explaining how gain must be considered with both the noise and signal.



You can also try recording with the gain knob being up, and with it being reduced and normalizing (digitally boosting) the signal, then compare the noise of the two.

What is really sad about these interfaces is that they made them really only compatible with condensor mics. It doesn't need the gain just a compatible input. But the corporate world always made these interfaces wrong as the majority of recording mics are not phantom powered. They should have made interfaces DC coupled for dynamic mics and if you want to use a condensor mic that needs phantom, get a power brick. But I guess this is the way they get you to spend more money that should have been capatible in the first place.

 

[BobbyP]

Also check out this video by Julien.

Wow!! Thanks so much for the information TalismanRich and three great videos. As I was saying I can ride with the way things are but it just seems odd to have to fight for some decent wave forms. Im going to follow your advise and concider a small pre-amp but in the mean time see what I can do in post. Most of my work is for telephone systems so it's not what you would call high quality but I do try come up with a great product when I can. Thank you again, I really appreciate your input, Cheers

 

[BobbyP]

Because I’m lazy, when I record announcement style stuff in the office, not the studio, because that’s forty feet away, I have a short XLR dangling from input one on my old Tascam. On a scale of 1 to 10 over 8 brings in proportionally more noise, so the knob sits permanently at 7.5 and in cubase, that is a mere tickle on the waveform display and a flicker up to half scale or so. Normalise to -3dB works much better than turning the gain up. However, I’ve got some dirt cheap inline preamps and they do the job even better, and they’re really cheap and actually really good. It seems such a simple thing to do, adding pretty noise free mic gain, but the manufacturers design their preamps to cope with people singing close and loud or guitars on condenser mics, not people reading scripts at two feet, or recording ants farting! It’s not a modern thing either. In the seventies, my Ferrograph reel to reel and an SM57 let me record bird song outside my window, even with tape hiss to get over!

H, Ha, I completely get what you are saying. I also come from the white pencil and razor blade world. I am seriously thinking about resurrecting some old gear I have that worked very well. My Windows 7 with Sonar 7 and a MAudio Delta 44 PCI and a small mixer. Beoing modern is sucking up a bunch of time, lol. Thank you so much for your reply and valuable insight. All the best, Bobby P

 

[BobbyP]

What is really sad about these interfaces is that they made them really only compatible with condensor mics. It doesn't need the gain just a compatible input. But the corporate world always made these interfaces wrong as the majority of recording mics are not phantom powered. They should have made interfaces DC coupled for dynamic mics and if you want to use a condensor mic that needs phantom, get a power brick. But I guess this is the way they get you to spend more money that should have been capatible in the first place.

Holy moly, you really know your stuff Drtechno. I've come to discover that mics needing phantom power work well with the interface i just bought, Focusrite 18i20. I have phantom hungry mics but my new mic, Electro-Voice RE20 does not require phantom and I am a bit nervous to add phantom power to that mic for fear of damaging it. The Electro-Voice RE 20 is a very popular mic and now I'm wondering what is everyone plugging their RE 20 in to. Thank you so much for your well thought out advice. I have some thinking to do. I mean that mic is not friends with that interface so I need to take a closer look at the interface part of the chain. Cheers. Bobby P

 

[BobbyP]

H, Ha, I completely get what you are saying. I also come from the white pencil and razor blade world. I am seriously thinking about resurrecting some old gear I have that worked very well. My Windows 7 with Sonar 7 and a MAudio Delta 44 PCI and a small mixer. Being modern is sucking up a bunch of time, lol. Thank you so much for your reply and valuable insight. All the best, Bobby P

You are right about the manufactures idea compared to reality. I don't want to be that close to the mic for a hundred reasons. I mean sometimes you want to warm up a read and you want to move in here and there to punch a word so yes you are bang on Rob.

 

[drtechno]

Holy moly, you really know your stuff Drtechno. I've come to discover that mics needing phantom power work well with the interface i just bought, Focusrite 18i20. I have phantom hungry mics but my new mic, Electro-Voice RE20 does not require phantom and I am a bit nervous to add phantom power to that mic for fear of damaging it. The Electro-Voice RE 20 is a very popular mic and now I'm wondering what is everyone plugging their RE 20 in to. Thank you so much for your well thought out advice. I have some thinking to do. I mean that mic is not friends with that interface so I need to take a closer look at the interface part of the chain. Cheers. Bobby P

Well you not going to damage the RE-20. Its a transformer dynamic mic. Triton Audio Fet Head is a good one to use. I think its still crazy they did that because it makes mics not really compatible. Normally, an Re20 is around 12 o'clock on the gain knob on most mixers like other mics of the same impedance (sm58,sm57, e835).

 

[rob aylestone]

I’m beginning to think that the reason Shure added the onboard preamp is because they’ve only just woken up to what people are doing with them. When designed, the output matched the radio desks they were plugged into, at the distance people used them at. In studios who liked them people would be singing Into them, again, no problem. A few people tried to use them on booms for dialogue for TV and movies, and that didn’t work so well. I guess at some point they were sitting back patting themselves on the back for a sudden increase in sales but got surprised by the moans and groans about poor gain, when everyone had been happy. Move the voice a foot away and the complaints start. Nobody complains about the gain on an SM57, probably because they slap them on louder things. I think the interface manufacturers have assumed as drtechno suggests, that nobody uses dynamics, and those that do go on drums and guitar cabs. Dave mentioned that it’s not hard to design a decent performing preamp for low output mics, and I’m surprised nobody has simply added a button marked boost? Cost would be minimal, and people would buy them. They’re just either lazy or out of touch.

 

[BobbyP]

I’m beginning to think that the reason Shure added the onboard preamp is because they’ve only just woken up to what people are doing with them. When designed, the output matched the radio desks they were plugged into, at the distance people used them at. In studios who liked them people would be singing Into them, again, no problem. A few people tried to use them on booms for dialogue for TV and movies, and that didn’t work so well. I guess at some point they were sitting back patting themselves on the back for a sudden increase in sales but got surprised by the moans and groans about poor gain, when everyone had been happy. Move the voice a foot away and the complaints start. Nobody complains about the gain on an SM57, probably because they slap them on louder things. I think the interface manufacturers have assumed as drtechno suggests, that nobody uses dynamics, and those that do go on drums and guitar cabs. Dave mentioned that it’s not hard to design a decent performing preamp for low output mics, and I’m surprised nobody has simply added a button marked boost? Cost would be minimal, and people would buy them. They’re just either lazy or out of touch.

Well said once again. It's tough for a guy such as myself. Im a voice guy with a low, booming distinct voice that'snot very technical at all. Thanks you so much, very kind of you.

 

[BobbyP]

Ok, well it looks as though I will be getting a signal booster as suggested by my very smart Home Recording Forum colleagues. Thanks for all your input and fabulous ideas folks. Kind of bugs me as I just bought a new interface and mic but from what i understand the Re 20 will in most circumstances need a push so I am good with it all. Just happy there is a reliable place to get top notch advice from some very nice and helpful folks. Thanks again to all...

 

[drtechno]

Dave mentioned that it’s not hard to design a decent performing preamp for low output mics, and I’m surprised nobody has simply added a button marked boost? Cost would be minimal, and people would buy them. They’re just either lazy or out of touch.

For the longest time all of them used to work, because they used to use the old transistor differential mirror mic pre everyone used in a mixing board. That typically had a 1K input impedance. After, the INA217 came along that you can set it up from 200 ohms dc coupled to 2K Ac coupled with phantom. The focuswrong reverted to a single op amp design and as a result forced the input z to 3K even though the op amp they used could be set up with 2K input impedance or even 1.5K.


For all those who have a focuswrong interface with a 3K input and a tech. Would be interesting to find out if placing a 3.3K resistor parallel at the input of the preamp changed the circuit formula enough to reflect in the gain circuit so it sees an impedance closer to 3K. Another thing to try would be placing a 1K resistor in series with the signal + and the signal -. Which should increase Rin value on its gain circuit formula.

 

[jamesperrett]

Dave mentioned that it’s not hard to design a decent performing preamp for low output mics, and I’m surprised nobody has simply added a button marked boost? Cost would be minimal, and people would buy them. They’re just either lazy or out of touch.

The problem is actually the other way round. In the old days you would have a button labelled pad to allow the preamp to handle higher output mics. Even the budget Studiomaster that Dave and I are discussing in the other thread has a 20dB pad button. Nowadays manufacturers are so pushed to make things as cheap as possible that they don't seem to be able to afford a pad button so we are stuck with preamps that clip too early and bunch up all the gain in the last few degrees of the gain control.

 

[drtechno]

The problem is actually the other way round. In the old days you would have a button labelled pad to allow the preamp to handle higher output mics. Even the budget Studiomaster that Dave and I are discussing in the other thread has a 20dB pad button. Nowadays manufacturers are so pushed to make things as cheap as possible that they don't seem to be able to afford a pad button so we are stuck with preamps that clip too early and bunch up all the gain in the last few degrees of the gain control.

Well one of the problems that should be addressed is that they are using a bad signal chain topology for A to D recording. Because if you go into the instrumentation sector of electronics (where the audio ADC came from) the standard build for analog always have a signal limiter before the converter ic. Also, they try to avoid unbalanced signal paths since that adds the power supply noise to the signal.

Btw, I thought the clip lights were too sensitive or out of cal. So I changed the gain in my channels in the gain of the first op amp. Because the mic pre wasn't clipping when it said it was. Now the clip light illuminates when the signal actually clips and doesn't clip the EQ anymore because that is what I found that was clipping in mine first: the Eq. It actually takes a lot to clip the mic preamp.

 

[BobbyP]

Thank you everyone for your help. I bought the Cloudlifter and all my issues were lifted, lol. I think I took too many idiot pills today and hope some kind soul will help me. How in tarnation do I make a new post? I was able to make this post but now I am looking for a button that I would expect to say "New Post Here" so I can start a new post. 2nd question. Does this forum have members using Logic Pro 10? Thank You

 

[bouldersoundguy]

Go to the Home page, select a sub-forum, click "Post thread" button.

 

[drtechno]

The problem is actually the other way round. In the old days you would have a button labelled pad to allow the preamp to handle higher output mics. Even the budget Studiomaster that Dave and I are discussing in the other thread has a 20dB pad button. Nowadays manufacturers are so pushed to make things as cheap as possible that they don't seem to be able to afford a pad button so we are stuck with preamps that clip too early and bunch up all the gain in the last few degrees of the gain control.

over the years I notice them increasing the loss in the front end with their capacitor coupled mic preamps. But when they do this, it has a tendency to make the gain contour change with source resistance. When these circuits are prototype, they chose a source resistance greater than they should have to lower the capacitor value of the phantom blocking caps. Because if you go by the old standards of building a mic preamp, it should pass a 50 ohm source without a loss and they don't do that because the caps are not at least 100uf.