Spikes Around 37 kHz and 40.5 kHz

[The Computer Audiophile]

Hi Guys - I just purchased and downloaded an album from Bandcamp at 24/96. Looking at it in Adobe Audition I see the same spikes at about 37 kHz and 40.5 kHz on every track. Anyone know what this is?

 

Here's a screenshot.

 

[jtwrace]

Interesting.  Worth trying the AIFF?  

[The Computer Audiophile]

downloading now.

[The Computer Audiophile]

AIFF has same spikes.

 

[jtwrace]

The good news is that is way past our hearing band.  If you email Brooklyn Duo they will respond...they might not know either though.  ?

[The Computer Audiophile]

5 minutes ago, jtwrace said:

The good news is that is way past our hearing band.  If you email Brooklyn Duo they will respond...they might not know either though.  ?

I'll give it a shot. 

[kumakuma]

13 minutes ago, The Computer Audiophile said:

AIFF has same spikes.

 

 

Finally a use for MQA!

 

@Lee Scoggins

[The Computer Audiophile]

1 minute ago, kumakuma said:

 

Finally a use for MQA!

 

@Lee Scoggins

Ha!

[mansr]

8 hours ago, The Computer Audiophile said:

Hi Guys - I just purchased and downloaded an album from Bandcamp at 24/96. Looking at it in Adobe Audition I see the same spikes at aobut 37 kHz and 40.5 kHz on every track. Anyone know what this is?

 

Here's a screenshot.

 

Probably switching noise from an SMPS used in the recording setup.

[The Computer Audiophile]

I’ve been exchanging emails with the Brooklyn Duo about this. I mentioned @mansr‘s comment about a possible SMPS issue and received the following response. 

 

“Ah! Likely my M-149 Neumann tube mic, which has a power supply, although the polar mode selector is on the mic itself. Interesting! I wonder if that's a defect or is in all those mics?”

 

Anyone know if this could be the case?

 

@JR_Audio may know?

[mansr]

2 minutes ago, The Computer Audiophile said:

I’ve been exchanging emails with the Brooklyn Duo about this. I mentioned @mansr‘s comment about a possible SMPS issue and received the following response. 

 

“Ah! Likely my M-149 Neumann tube mic, which has a power supply, although the polar mode selector is on the mic itself. Interesting! I wonder if that's a defect or is in all those mics?”

 

Anyone know if this could be the case?

It's possible. It could also be the ADC or mic preamp (if separate from the ADC). It might even be from an unrelated SMPS that's accidentally sitting close to the mic preamp. Maybe it isn't even an SMPS but some other electronics emitting that noise.

 

Whatever the source, those tones are not going to audible in any way, so there's really nothing to worry about. If it were my recording setup, I'd probably try to get rid of it just because, but I don't see any reason to feel cheated with your purchase.

[jtwrace]

@The Computer Audiophile did you show them this thread?

[The Computer Audiophile]

6 minutes ago, jtwrace said:

@The Computer Audiophile did you show them this thread?

Not yet 

[JR_Audio]

This could have 4 different reasons: Microphone, Mic Pre-Amp, Tape Head or Venue Noise

 

This could be the SMPS noise of the polarization voltage that could go into the signal for 2 reasons: Either the signal transformer / path is not fully balanced, so that the SMPS noise is not canceled out, that would otherwise be the case with balanced signal path (if the in-phase path has for example 1k1 and the off-phase path 1k0 input resistance), or what I have had with older Neumann Tube of FET mics is, that the filtering electrolyte got a cold solder point.

 

It is always good to watch the signal of the recording setup with tools like SpectraFoo for abnormalities. I have sent back some mics, that have not been fully balanced, as also some mic preamps, that have not been fully balanced.

 

PS: Some tape machines do have also those spices due to the AC bias of / in tape head, but I don’t think this is the case in the above example, that looks like a tape free recording.

 

Another reason could be a noise in the recording venue: I had a life recording in a church and have had a 40.5 kHz spike in my setup and finally found out, that this was an “anti-bird” noise, that was send out with some piezo tweeters in the church, to prevent birds coming in / flying into the church. In another case, I have had an ultra frequency smoke detector at around 36 kHz.

 

As I said above, it is always good to check the signal that is to be recorded.

 

I hope this helps.
Juergen

[The Computer Audiophile]

Thanks Juergen. 

[mansr]

4 hours ago, JR_Audio said:

Another reason could be a noise in the recording venue

On many (not all that) old recordings there's a spike just below 16 kHz corresponding to the horizontal sweep frequency of a CRT. Now that LCD screens have taken over, that's thankfully a thing of the past.

[semente]

On 10/16/2018 at 11:39 AM, mansr said:

On many (not all that) old recordings there's a spike just below 16 kHz corresponding to the horizontal sweep frequency of a CRT. Now that LCD screens have taken over, that's thankfully a thing of the past.

So that's what it is.

[tmtomh]

On 10/16/2018 at 6:39 AM, mansr said:

On many (not all that) old recordings there's a spike just below 16 kHz corresponding to the horizontal sweep frequency of a CRT. Now that LCD screens have taken over, that's thankfully a thing of the past.

 

6 hours ago, semente said:

So that's what it is.

 

Yes, and once you know it, you can load up waveforms of lots of old-ish recordings and that line at 15.7-something kHz from a CRT flyback transformer is everywhere. It's on a lot of '80s electronic music-oriented records in particular, because a good number of synths like the Fairlight were used with a CRT.