recording bass direct - low signal level

[tranceFusion]

I got a PCI Emu 0404 for the holidays and I am trying to record bass direct into it.

My first try was with a passive jazz into a Sadowsky Pre/DI Pedal. I was assuming that this thing was going to boost the signal, but it was still quite low (-30dB below the what the software seems to indicate as a target level). I unplugged the bass from the DI and plugged it directly into the card, and surprisingly the level did not change what-so-ever.

I thought maybe there was a problem with the DI so I tried my 55-02 (active bass). The level was even lower. (-42dB below the target

I thought maybe it was something to do with the card, but when I plugged in a condenser mic, I had to turn the mic preamp nearly all the way down to keep it from distorting and stay out of the red..

Any help making sense of this would be appreciated. Thanks

[fretlessrock]

What inputs are you using? I don't know about the emu card but it sounds like you are using the wrong input for the bass, or the interface turns the preamp off when you plug an unbalanced connector into it. I like using a traditional DI (high-z unbalanced input to a lo-z mic level XLR output) and using the DI output to drive a mic pre. It is the most foolproof way to match impedance and level.

[anderbass]

Originally Posted by tranceFusion

I had to turn the mic preamp nearly all the way down to keep it from distorting and stay out of the red..

Any help making sense of this would be appreciated. Thanks

I dont use computers to record, but does your sound card (or external mic preamp ?) have a "line or instrement level input" or setting you could give a quick try with your amps DI signal?

[Nick Kay]

+1 to the other two - it sounds like you're plugging into a line input, expecting it to be an instrument input. Try taking the XLR out from the Sadowsky unit and plugging that into one of the microphone inputs.

[tranceFusion]

The PCI card does not contain any preamps, as far as I know, though here are the specs, if anyone can make sense of them: http://www.emu.com/products/product....Specifications

I'll admit I am rather new to this stuff but I though the point of a bass preamp was to give you a boosted signal. If not, what is the point then?

You are telling me I should plug my bass preamp into my mic preamp? I figured only the microphone would need to go into the mic preamp.. seems a bit counter-intuitive to me.

[Nick Kay]

The Sadowsky unit has more in common with the onboard preamp of an active bass than, say, a rackmount Sansamp or a Joe Meek. It outputs a hot instrument-level signal, not a line-level signal. Power amps, audio interfaces without preamps, line mixers and the like all expect a line-level signal. The Sadowsky pre is more for shaping tone, buffering long cable runs, and driving an output to the mixer.

As for the bass > mic preamp issue, it's just a matter of bringing it up to line level. You can use a mic preamp, a channel strip on a mixing board, the preamp on an amp head, or an outboard instrument preamp, as long as it outputs line-level and you can match the impedance between the input and what you're plugging into it. As a general rule, microphones and line level = low impedance, instruments = high impedance.

So, without getting into the technicalities of circuit design, what makes a mic preamp different from an instrument preamp is the inputs. A mic preamp's input is optimized for a low-impedance, balanced signal. An instrument preamp's input is optimized for a high-impedance, unbalanced signal. A DI, like the XLR section on the Sadowsky you have, takes a high-impedance, unbalanced signal (your bass' output) and converts it to a low-impedance, balanced one, suitable for input on a mic preamp.

[Charling]

Originally Posted by Nick Kay

The Sadowsky unit has more in common with the onboard preamp of an active bass than, say, a rackmount Sansamp or a Joe Meek. It outputs a hot instrument-level signal, not a line-level signal. Power amps, audio interfaces without preamps, line mixers and the like all expect a line-level signal. The Sadowsky pre is more for shaping tone, buffering long cable runs, and driving an output to the mixer.

As for the bass > mic preamp issue, it's just a matter of bringing it up to line level. You can use a mic preamp, a channel strip on a mixing board, the preamp on an amp head, or an outboard instrument preamp, as long as it outputs line-level and you can match the impedance between the input and what you're plugging into it. As a general rule, microphones and line level = low impedance, instruments = high impedance.

So, without getting into the technicalities of circuit design, what makes a mic preamp different from an instrument preamp is the inputs. A mic preamp's input is optimized for a low-impedance, balanced signal. An instrument preamp's input is optimized for a high-impedance, unbalanced signal. A DI, like the XLR section on the Sadowsky you have, takes a high-impedance, unbalanced signal (your bass' output) and converts it to a low-impedance, balanced one, suitable for input on a mic preamp.

The definitive answer, you need no more than this.

Your interface is expecting line level and you are giving it instrument or mic level signals!

[Stumpy]

On my non Digidesign sound card (pci - M-audio 1010LT) I have a mixer connected to do the mic pre's and signal boosting.

When in the studio we use an Avalon to the HD3 Protools rig.

Hope this helps a bit.

[tranceFusion]

Originally Posted by Nick Kay

The Sadowsky unit has more in common with the onboard preamp of an active bass than, say, a rackmount Sansamp or a Joe Meek. It outputs a hot instrument-level signal, not a line-level signal. Power amps, audio interfaces without preamps, line mixers and the like all expect a line-level signal. The Sadowsky pre is more for shaping tone, buffering long cable runs, and driving an output to the mixer.

As for the bass > mic preamp issue, it's just a matter of bringing it up to line level. You can use a mic preamp, a channel strip on a mixing board, the preamp on an amp head, or an outboard instrument preamp, as long as it outputs line-level and you can match the impedance between the input and what you're plugging into it. As a general rule, microphones and line level = low impedance, instruments = high impedance.

So, without getting into the technicalities of circuit design, what makes a mic preamp different from an instrument preamp is the inputs. A mic preamp's input is optimized for a low-impedance, balanced signal. An instrument preamp's input is optimized for a high-impedance, unbalanced signal. A DI, like the XLR section on the Sadowsky you have, takes a high-impedance, unbalanced signal (your bass' output) and converts it to a low-impedance, balanced one, suitable for input on a mic preamp.

You are the man!!! Thanks so much for the detailed explanation.

I have a few more questions now though

1) Will routing my bass throug a mic preamp affect the tone? Is this ideal compared to some other method of boosting the signal?

2) My mic preamp is able to take an instrument (unbalanced) signal. Assuming I am happy with the tone of the instrument, is there any reason why I should plug it into the sadowsky di pedal rather than just using the mic preamp?

3) Since I was using an unbalanced output from the sadowsky DI pedal, will the signal strength be higher if I were to use the balanced XLR output and with a TRS cable adapter and plug that into the card from the sadowsky pedal? (basically, is the balanced output going to be higher than the unbalanced?)

4) I am currently using a TS (guitar) cable to go from the mic preamp to the interface (which can take TS or TRS). Should I get a TRS cable to use for this purpose? I guess I am losing the balanced output.. does that matter if the signal strength seems more than sufficient?

Thanks so much for the help - I really appreciate it.

[Nick Kay]

1) Generally speaking, mic preamps are the most transparent way to go from mic or instrument level up to line level. There's a few exceptions, of course (tube preamps and Joe Meeks come to mind), but generally speaking, it'll be much more of the natural bass tone than you'd get through an instrument preamp or the like.

2) As I said, the Sadowsky Preamp/DI acts a lot like the onboard preamp of an active bass. It allows additional tone shaping before it hits the converters, as well as some tonal flavours that you might not get very easily on a EQ plugin. Whether or not you want that in the signal chain is up to you. Personally, I'd go without, but I'm also the type to DI guitars and reamp them later, and use triggered or sampled drums for just about everything. Experiment! See what you like.

3) Using a balanced output into an unbalanced input will often lose you about 6dB of signal, but I don't know how your interface will react in the situation you describe - I'm not much of an E-MU guy, except for their line of software synthesizers. Give it a shot, it won't hurt anything, but don't expect much more than 6dB of difference. I'll tell you right now that it won't make up that 30dB gap you were describing in the original post, though.

4) Depending on how your interface handles unbalanced inputs, you might gain some signal strength, but it'll be a negligible difference. Probably less than 6dB, if anything at all. The main difference between balanced and unbalanced lines is the noise floor. In a balanced system, there are two copies of the signal going through the cable. One copy is shifted 180 degrees out of phase (ie: if they were summed together, they would completely cancel eachother out). Any noise that gets picked up by one copy of the signal is also picked up fairly well by the other copy. On a balanced input, the two signals are shifted back into phase, and now any noise they picked up is 180 degrees out of phase - so it cancels out almost completely. This is great on stages where the cable runs may be upwards of 50 feet, but in a home studio, you won't notice the difference on one channel. However, mixing 4 tracks or more together, the noise of an unbalanced system starts to add up. Seeing as the price difference between TS and TRS cables is negligible, I think it's a worthy investment.

Please excuse me if my language is less than comprehensible - it's been a long night and I have more than my fair share of rotten sugarcane juice in me. Let me know if you have any other questions - like most of the guys on Talkbass, I can talk gear all day.

[tranceFusion]

I have to thank you again Nick for very clear consise answers.

I have determined that the Sadowsky pedal is actually able to provide a hot signal to the sound card, but I have to use an XLR to TRS cable to make use of the XLR output. This output is apparently much stronger of a signal than the 1/4" out (which now that you have explained to my about instrument vs line level, seems pretty obvious).

I think I have one last major hurdle here and that is monitoring. The analog output on the sound card says it is -10db unbalanced. The signal is extremely weak. It is barely audible through my studio monitor earphones and I have to jack to volume up to 10 on my self-powered (internally amped) computer speakers to get to a reasonable listening volume.

I picked up a cheapy Behringer XENYX mixer to go between the output from the card and my headphones/computer speakers, so I could have the mic preamps to boost the output. It works, but I feel like maybe this isn't the right tool for the job. What do most people do about this? Do most people use the digital outputs (i don't even know what to hook them to)? Or am I on the right track?

[Nick Kay]

You've got it right, mate. A mixer is exactly the right tool for interfacing your gear together. I mean, it gets the go-to when you need to bring mic level up to line level. Why not when you need to bump -10dBv up to +4dBU? Glad to see everything's working out for you!