M-Audio Transit and REW... a success!

**jagman** · **03-15-08, 06:56 PM**

BTW, I don't want to artificially boost below 20Hz. The sub is plenty capable of output down low and I'm already worried about bottoming the subs out. My concern is getting more lower bass output than upper bass output without having to do extensive EQ. Having a lower low pass filter (e.g. 60 Hz instead of 80Hz) would probably help.

**jagman** · **03-16-08, 12:10 PM**

I tried adding 5 Ohm 113 watt resistors to the positive lead as per another thread. I know it is contraversial, but it dropped ULF output considerably (mostly below 15Hz and especially below 10Hz). It also dropped output some above Fs. I definitely believe it will protect the subs from overexcursion, but I don't know if I like the sound better. It's always about trade offs. Since they were cheap, I figured I'd give them a shot. At this point I don't know if I want to keep them in the system or not.

Anyways here are the plots. Sorry the first has extra lines in it.

75dB Target with 8dB Hard Knee House Curve:

81dB Target with 8dB Hard Knee House Curve:

Obviously with the second the gain on the amp needs to be reset. I haven't had a chance to listen yet but I'll play with it and see how it goes. The level going to the sub amp should be higher.

John and Bruce... is the second plot more at what you guys want me to do?

**brucek** · **03-16-08, 12:31 PM**

Quote:

is the second plot more at what you guys want me to do?

Yep..........

**brucek** · **03-16-08, 01:54 PM**

jagman,

one of the plots above was the only time you included a soundcard cal line. This card looks interesting to me as a future purchase (I want a laptop in the near future). How does the soundcard response look down to 10Hz and up to 20K - pretty good?

I also wondered about the dual purpose analog/digital input port that accepts both analog line-in and digital S/PDIF in, and is switched and accomplished by a 'mini-optical adapter'. When it's plugged in it allows the connection of optical S/PDIF digital input. Does this seem like it's well done? Is the adapter positive when it plugs in?

brucek

**imbeaujp** · **03-16-08, 07:48 PM**

Hello,

M-Audio seems to have great sound cards. I just bought the FastTrackPro (with midi and phantom mic input) and did some test with the unit. You can read the thread HERE.

JP

**jagman** · **03-16-08, 10:04 PM**

Bruce,

I've only used the analog line in and line out (for REW) so I cannot comment on the S/PDIF digital input. I read several reviews before purchasing it and generally speaking the reviews were positive, but also mixed. People have reported pops in their speakers during playback, but have also said those noises are typical of USB external soundcards. I heard them this morning for the first time. I can tell you it is much easier to use for REW than SoundBlaster. The driver that comes with it is outdated... you have to download the current on from their website, but other than that it's a piece of cake. I'm using my PC right now but I'll post a full bandwidth plot of the soundcard cal line when I'm on the laptop. For the money, I'd say it's pretty hard to beat.

Hope this helps,

Krister

**jagman** · **03-18-08, 04:55 PM**

Here's the plot of the soundcard:

**brucek** · **03-18-08, 05:00 PM**

Thanks Jagman, looks good....

brucek

**m-fine** · **03-18-08, 05:17 PM**

That looks sufficiently flat from 7-20K!

**edwinauer** · **03-30-08, 06:35 AM**

Hi Jagman,

Are you using the Transit with a SPL meter connected?
Im asking because it seems my Transit gives a 5V power signal (Line-in doubles as Mic-line) to the SPL meter which makes it impossible to make good measurements with it. It's a RS analog btw.

Anyone has any ideas if its a setting or other problem?

Thanks!

Edwin

**brucek** · **03-30-08, 08:51 AM**

Quote:

Im asking because it seems my Transit gives a 5V power signal (Line-in doubles as Mic-line) to the SPL meter which makes it impossible to make good measurements with it. It's a RS analog btw.

I doubt that's the problem. The RS meter would be AC coupled and as such the capacitor would block any DC from affecting the output.
Were you able to get a good soundcard cal file?

brucek

**JohnM** · **03-30-08, 11:10 AM**

The bias output on a mic input will cause the RS analog meter to be driven to its end stop. On a mic/line input there would normally be auto-sensing of the impedance of the connected source though, so shouldn't end up with that problem. Also the bias is usually on just one of the inputs, so could try the other but if the soundcard is treating the input as mic there will be too much gain anyway.

**mojogoes** · **03-30-08, 11:34 AM**

Quote....

Here's the plot of the soundcard:

--------------------------------------------------------------------------------

Well done it looks just fine.....i was going to going with this same unit but at the time couldn't Wait for someone to do what you have done........but i think this 3 in 1 unit is very good.....it sells for £60/£70 new on british ebay at the moment.

**brucek** · **03-30-08, 02:33 PM**

Quote:

The bias output on a mic input will cause the RS analog meter to be driven to its end stop. On a mic/line input there would normally be auto-sensing of the impedance of the connected source though, so shouldn't end up with that problem. Also the bias is usually on just one of the inputs, so could try the other but if the soundcard is treating the input as mic there will be too much gain anyway.

Huh, that surprises me John. I thought the RS meter would block the bias (assuming it's even present when a low impedance line level device is plugged in).

The M-Audio Transit is quite a nice USB device (I consider buying one myself).

It has a single 1/8" (3.5mm) input jack that is a triple purpose jack for (S/PDIF 1/8” mini digital Optical In or 1/8” mini Analog Mic/Line In) depending on what it senses at the port. The Optical widget switches the port to digital, but when it is unplugged, I assume the low impedance analog RS meter would then shut down the +5v bias. But if it didn't, why would it cause the meter to be driven to it's extreme? Would the coupling capacitor (that I've witnessed in schematics) not block this?.

brucek

**JohnM** · **03-30-08, 04:02 PM**

I don't have the schematics to hand but I have seen what happens to the analog meter when plugged into a PC mic input. The bias shouldn't be there when a line source is connected though.

**edwinauer** · **03-30-08, 05:14 PM**

Hi,
Well what I can see is that the moment I connect the Transit to the SPL, the SPL meter gives some, rather high, reading and continues doing that (without any real sound at that moment). I have two SPL's so I checked them both, same thing. After disconnecting the Transit ... reading is gone too.

Is this normal, or is it a problem with the Transit?

Thanks!
Edwin

**brucek** · **03-30-08, 05:26 PM**

Quote:

what I can see is that the moment I connect the Transit to the SPL, the SPL meter gives some, rather high, reading and continues doing that (without any real sound at that moment). I have two SPL's so I checked them both, same thing. After disconnecting the Transit ... reading is gone too.

Is this normal, or is it a problem with the Transit?

It would indicate consistency with our discussion that the M-Audio device continues to output the DC even when a line-level device is plugged in and that the RS meter does not block the DC bias. Kinda weird. I don't know what to think. I wish someone with this device would comment on their experience.

brucek

**JohnM** · **03-30-08, 05:44 PM**

Does the same happen on both left and right inputs?

**brucek** · **03-30-08, 05:46 PM**

I assume you used a stereo connector plug at the mic/line in jack?

This would be the same situation as at the line-out connector where you need to use a stereo 1/8" connector that breaks out to left and right channels........

The RS meter would connect to the right channel and hopefully the Transit device would see this low impedance line device and shut down the DC bias.......

brucek

**jagman** · **03-31-08, 12:10 AM**

Quote:

brucek wrote:

I assume you used a stereo connector plug at the mic/line in jack?

This would be the same situation as at the line-out connector where you need to use a stereo 1/8" connector that breaks out to left and right channels........

The RS meter would connect to the right channel and hopefully the Transit device would see this low impedance line device and shut down the DC bias.......

brucek

That's what I did with very usable results.

**edwinauer** · **03-31-08, 11:01 AM**

Quote:

brucek wrote:

I assume you used a stereo connector plug at the mic/line in jack?

This would be the same situation as at the line-out connector where you need to use a stereo 1/8" connector that breaks out to left and right channels........

The RS meter would connect to the right channel and hopefully the Transit device would see this low impedance line device and shut down the DC bias.......

brucek

Yes, i'm using a stereo 1/8" connector which splits in 2 rca type connectors. I've been trying to get a new soundcard calibration and for some reason, when the 1KHz is playing, the detected signal is alternating between left and right channel. Few seconds left channel and then a few seconds right channel, very odd. I'm going back to testing and will let you all know how the results are. I'll test both left and right channel if I come that far.

Edwin

**edwinauer** · **03-31-08, 11:28 AM**

After disconnecting and resetting everything ... im getting a good soundcard calibration again.

So i've connected the SPL and checked both channels. On both channels there is DC present and the Transit doesnt adjust itselve on any of the channels

Not sure what to try next ... any ideas?

Jagman, what type SPL did you use? I've tried 2 analog RS types, did you use a digital one?

Edwin

**brucek** · **04-01-08, 07:26 PM**

Quote:

So i've connected the SPL and checked both channels. On both channels there is DC present and the Transit doesnt adjust itselve on any of the channels Not sure what to try next ... any ideas?

Well, I contacted M-Audio and they got back to me on this issue. They indicated that the USB Transit card provides 3.3 volts DC on the line-in jack to power electret mics. There is no way to remove this DC voltage and is always present irregardless of the connected device. They indicate that this normally isn't a problem, but can be on some devices and so check with the manufacturer.

Well, that sure doesn't work for me. I was going to purchase one of these for my new laptop, but not anymore. I would normally just take the device apart and disconnect the voltage, but some units today are quite difficult to seperate without damage.

I tested the Radio Shack meter with 3 volts DC on the output (as a test) and indeed the meter pegs, so it's probably not a good idea to use this card with the Radio Shack meter.

Then again, with the problems I've read from other posters with regard to Vista and the Soundblaster Live card, I don't know if I want to go down that road either.....

Mmmm, which card to buy.......

brucek

**jagman** · **04-02-08, 12:51 AM**

I have the new(er) RS digital SPL meter. I had all sorts of problems with another soundcard on a different computer, but the M-Audio Transit has been remarkably easy and repeatable to use. Good luck getting your setup to work properly.

**edwinauer** · **04-02-08, 01:29 PM**

OK, nice. I was hoping you were using a different type SPL meter :-)
I'll check for a digital RS type. Can you post which type you have?

The soundcard itselve seems to be high quality, so I rather use a new spl meter.

Thanks,
Edwin

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