Any affordable device that boosts -10dBV level to +4 studio level without introducing extra noise?

[kartoffelmann]

Wanna go from a good old stereo amplifier into a Fireface UFX+. Since RME decided to drop -10dBV support, this results in a 9 dB higher noise floor, making it a pretty suboptimal solution.

Is there any simple and straightforward way I can boost the -10 dBV signal to +4 studio level before going into the UFX+ while maintaining the (relatively) low noise floor that the UFX+ is capable of and ideally also preserving everything up to 96 kHz?

I know next to nothing about electronics, so this may be simpler than I think or harder than I think. Thoughts?

Also, would I be well-advised to use DI Box going from unbalanced to balanced? I notice a certain amount of (inaudible) low frequency noise on the input currently going in directly. Should I even use a combo DI Box that can boost the level? If so, what kind of unit would be good?

This device claims to do just what I need: https://www.radialeng.com/product/j4

But it's pretty darn expensive (for that money I could probably just get a better ADC...) and a review on Thomann says it colors the sound.

 

[Wayne A. Pflughaupt]

Is there any simple and straightforward way I can boost the -10 dBV signal to +4 studio level before going into the UFX+ while maintaining the (relatively) low noise floor that the UFX+ is capable of and ideally also preserving everything up to 96 kHz?

Probably not. There are at least a few issues here.

First is the S/N of the boosting device. Then there is the S/N of the device to be boosted. And then we have the boosting process itself.

Naturally, you want the boosting device to have good S/N properties. However translating -10 dBv to +4 dBu to a common value, Vrms, we can see the potential problem. -10dBu = 0.316 Vrms, while +4 dBu = 1.228 Vrms, which means the latter is 400% higher than the former.

Unfortunately, there is no free lunch with artificial signal boosting. You aren’t just increasing the maximum output of the source component. You’re increasing its entire operating range. This means the noise floor increases along with everything else.

It’s foolish to think that a component’s maximum signal level can be increased by 400% without exacting a penalty at the other end: an increased noise floor. So, even if the boosting device is a S/N of 200 dB, the weak link in the chain will always be the component being boosted. If you already have noise problems with your source component, boosting its output will only make the noise even worse.

A possible salvation, the Radial has adjustable output, so boosting only as much as you need instead of the full amount might work for you.

Regards,
Wayne A. Pflughaupt

 

[kartoffelmann]

Oh for sure, I didn't mean to imply that I could get rid of the noise coming from the source. I just wanted something that doesn't add additional noise to the source.

So theoretically assuming I had a source with such a low noise level that it can serve the UFX+ (if it had a native -10 dBV input), it would be nice to boost that to the correct level without introducing additional noise or lifting the noise floor beyond the amount it would be lifted through the boosting anyway.

 

[Cbdb2]

You notice an amount of inaudible low f noise? How do you notice it if its inaudable? Are you sure its not a ground loop? That would be a different problem. Is it a hum or is it white noise?

 

[Wayne A. Pflughaupt]

I just wanted something that doesn't add additional noise to the source.

Well, you won’t know until you try. Maybe you can find a vendor for the Radial with a generous return policy.

Why do you need the boost to begin with? It’s not a problem giving a +4 device a -10 input. The figures aren’t fixed anyway. Program source signal strength from -10 can actually peak all the way up to +4.

Regards,
Wayne A. Pflughaupt

 

[kartoffelmann]

I notice it via FFT. Seems like it's actually one spike around 50 Hz that worries me, sounding indeed like a hum, but still not really audible at normal level. Is that a ground loop?

 

[kartoffelmann]

Well, you won’t know until you try. Maybe you can find a vendor for the Radial with a generous return policy.

Why do you need the boost to begin with? It’s not a problem giving a +4 device a -10 input. The figures aren’t fixed anyway. Program source signal strength from -10 can actually peak all the way up to +4.

Regards,
Wayne A. Pflughaupt

Well because it raises the noise floor. It's okay in the audible range but the ultrasonic stuff has a pretty high noise level with the UFX+ and I wanted to counteract that. In my particular use case (but others may and will likely come) I'm recording vinyl records. Those almost never peaked on my FF800 in -10dBV mode, only a few extremely loud electro 45 RPM records did that in rare cases.

The Radial was really just an example. I would rather buy myself a FF800 to use as ADC than to buy such an expensive signal amplifier. Was hoping there'd be some cheap option.

 

[levimax]

A transformer can step up the voltage without additional noise and they eliminate ground loops (hum) as well take a look .. I think the DB-2PX might work for you https://www.jensen-transformers.com/industry_type/recording/

 

[Wayne A. Pflughaupt]

Well because it raises the noise floor.

How do you figure that it raises the noise floor? Is this something you actually observed?

I’ve never had any problem with additional noise using pro gear in my HT system.

Regards,
Wayne A. Pflughaupt

 

[A800]

Amplifying without extra noise?
Very interesting...

 

[Wayne A. Pflughaupt]

Amplifying without extra noise?
Very interesting...

If you are referring to my post, there is no amplifying. Where to you get that? The signal in the pro device is used "as is" from the consumer component.

If you weren't referring to my post, then ignore this.

Regards,
Wayne A. Pflughaupt

 

[A800]

If you are referring to my post, there is no amplifying. Where to you get that? The signal in the pro device is used "as is" from the consumer component.

If you weren't referring to my post, then ignore this.

Regards,
Wayne A. Pflughaupt

No, I was referring to the thread title.
All good.

 

[kartoffelmann]

How do you figure that it raises the noise floor? Is this something you actually observed?

I’ve never had any problem with additional noise using pro gear in my HT system.

Regards,
Wayne A. Pflughaupt

Yup. The old Fireface 800 had a switch for -10 dBV, the UFX+ doesn't. So you have to add 9dB of digital gain, raising the noise floor by 9dB, resulting in a worse performance than the old Fireface.

Amplifying without extra noise?
Very interesting...

Be gentle, I'm a noob.

A transformer can step up the voltage without additional noise and they eliminate ground loops (hum) as well take a look .. I think the DB-2PX might work for you https://www.jensen-transformers.com/industry_type/recording/

Thanks for the tip. Can you elaborate on what such a transformer does? Since it's a passive box, how can the signal end up being higher in the UFX+? Or maybe I am having a fundamental lack of understanding here? What is the difference between amplification and transformation? Does this mean the signal ends up higher voltage (higher level in the UFX+) but less .. uhm.. amperage? If so, what is the significance of that and is there any downside? Please don't laugh, haha.

 

[levimax]

Yes a step up transformer increases voltage and reduces amperage. It depends on application if this is an issue or not but for most line level tasks it works great. The disadvantages are some limitations in frequency response and some small increase in distortion and cost. As I mentioned before an additional huge advantages is "complete galvanic isolation" which means it will eliminate any hum caused by ground loops.

 

[kartoffelmann]

Yes a step up transformer increases voltage and reduces amperage. It depends on application if this is an issue or not but for most line level tasks it works great. The disadvantages are some limitations in frequency response and some small increase in distortion and cost. As I mentioned before an additional huge advantages is "complete galvanic isolation" which means it will eliminate any hum caused by ground loops.

That sounds fantastic and is just what I need. Thank you very much!

However now I'm slightly confused because on the Jensen site it says that the difference between +4 and -10 is actually 12 dB, but RME's manual only says to give 9 dB of gain to a -10 signal to reach +4. Is RME using a non-standard implementation or are these considerations for headroom? I did notice on an old Steinberg MR816 interface that I was getting a clipped signal from the same input the RME did not clip at. It would be a shame to go through all this pain to raise the level only the end up with a clipped signal.

 

[RayDunzl]

Since it's a passive box, how can the signal end up being higher

Simplistically:

Transformers "transform" alternating (not DC) voltage and current.

A step-up transformer increases output voltage and decreases output current, relative to the input voltage and current.

A step-down transformer decreases output voltage, but increases current , relative to the input voltage and current.

(hmm... didn't see the reply embedded in a quote above)

 

[kartoffelmann]

Hmmm now I found this:
https://www.jensen-transformers.com/product/pc-2xr/

The FAQs say this:

Can I use the PC-2XR in reverse?

Although other manufacturers offer products based on this idea (Rane “Balance Buddy” or Ebtech “Line Level Shifter” for example), we don’t recommend it. Any transformer has an impedance ratio that is the square of its turns ratio. In the case of the PC-2XR, the turns ratio would be 1:4 which leads to an impedance ratio of 1:16. This means that the input impedance of the “pro” balanced input we drive will be reflected back to the “consumer” output at one-sixteenth of that value. If we assume a typical input impedance of 10 kΩ for the balanced input then the load seen by the consumer source would be about 625 Ω. Since the source impedance of a consumer output is commonly 1 kΩ or more, the reflected loading losses are high. Under the conditions above, the actual gain increase at the balanced input will be only a disappointing 2.7dB. Not only is this much less than the ideal 12 dB, but the load reflected to the consumer output may cause headroom loss, increased distortion, and poor low frequency response. In most situations, a 1:1 transformer can be used because the “pro” equipment can easily provide the required gain. In this case, you should use the model PI-2RX at the balanced input.

Does this mean that what I am trying to do is impossible or am I misreading this?

 

[A800]

I would just use the Behringer MIC2200(V2).
https://www.bhphotovideo.com/lit_files/84914.pdf
Very good sound.
Variable low cut, parametric EQ, phase...
It has a tube also.

 

[kartoffelmann]

@A800 Thanks, but I don't know about that. Behringer isn't exactly known for extreme quality, and a tube doesn't make me think of a neutral voltage increase either. Correct me if I'm wrong tho.

 

[kartoffelmann]

Actually, thinking about it, the SMMDB unit of Jensen Transformers says that it produces Mic Level. The Mic inputs of the UFX+ actually have 2 dB more dynamic range in the tech specs so if I could use those without gain, that might be even better than the Line inputs. But is Mic Level a normed thing? What is the likelihood that I will end up having to use gain again?