Duelling vibratos?

I hate that I’m too much of a newbie in DAP, and that I’m sure I’m overlooking where my issue is already addressed, but since I lack the jargon, I have to start somewhere.

I’ve digitized a 1985 recording on cassette of a choral concert. One of the ensembles is an all-women’s chorus.
To do this, (the digitizing, I mean) I’m using the Behringer Uphoria UM2 between my old Denon tape deck (RCA outputs) and my Macbook Air 2020, which only has USB-C inputs.

I’m getting what sounds like the beats & distortion you might get from several dominating loud voices and their “duelling vibratos.” I’m trying to figure out how to diminish that effect, and I don’t know what tools or effects to try.

When I play back the section, I can see on the playback meter that it’s “in the yellow,” and between -12dB and -6.
(I don’t really understand the difference between what the dB mean on the playback/recording meters, vs. the vertical scale next to the waveform window, which ranges from -1 to 1 dB).

Should I play around with Audacity’s equalizer settings? Compression? Or should I re-record the track with a higher gain setting from the USB interface, and lower the recording levels in Audacity?

I’ve attached a short audio clip.

Was the original recording mono?
The audio in your clip is identical in both left and right channels = “mono”.

The original tape is, I think, stereo. I thought the UM2 line-in would automatically turn it into mono, and that I would have to reconvert it. Evidently I chose the wrong method.
But, are you suspecting that there is some out-of-phase-ness going on between the 2 channels, that is causing the beating?

Do you hear that “beating” when you listen to the tape? In other words, is it just the Audacity recording that has the problem and not the original? If so, then it may be due to the conversion from stereo to mono.

What sort of leads are you using to connect the Denon tape deck to the UM2?

In a nutshell, yes, I still hear some beating in the original recording. Although I have to say, when I listened to the tape directly, using headphones (1/4" jack), the sound quality seemed overall louder, and the stereo effect was more evident.
Also it was at a higher volume level, which there did not seem to be a volume control for! But I’m not really concerned about that, as that is not the same output I use for connecting to the UM2.

I don’t know what brand the leads are, but at the tape deck end, there are the 2 white & red RCA plugs, and at the UM2 line-in end, it’s a 1/8" plug with a 1/4" adapter.

I’m starting to wonder if I should get a 1/4" to 1/4" cable, to plug into the jack on the front of the tape deck. The sound had more “presence”, but maybe that’s “merely” the fact that it’s a stereo signal.

That explains why you are only getting a mono recording.

You either need two leads, RCA plug one end, 1/4" MONO jack on the other,
a STEREO lead with 2 RCA plugs one end and TWO 1/4" MONO jacks on the other.

Well, I guess I should have bought a different USB interface, then, because there’s only 1 line-in on the front of the UM2.
The 2 RCA plugs in the back of it are labelled “Outputs”
Maybe I’m not correctly describing what I have. It’s a y-shaped cable: the forked parts lead to red & white RCA respectively, with [effectively, I assume] a 1/4" on the other end.

(how come stereo headphones can yield left & right channels from one 1/4" plug? Can’t the cable construction yield the same result, but with the signal(s) going the opposite direction?)

The big socket on the left is a “combo” connector. It can be used with either a 3 pin XLR plug or a 1/4" Jack plug.
Both the combo socket and the normal 1/4" jack sockets are mono. You need to use both for stereo.

Stereo jack plugs have three connections: Tip, ring, sleeve.
The sleeve is a common “earth” connection, the tip is the left “hot” signal connection and the ring is the “hot” right signal connection.

Ok, I’m clearly an idiot. I know about the combo connector–it’s an input, yes?

There are 2 normal 1/4 jack sockets on that side of the UM2. The one immediately to the right of the combo is labelled ‘instrument’. The other is for headphone monitoring, thus only output, right?

Are you saying I should be able to use the 1/4" jack labelled 'instrument? Even so, that would mean I’d have to buy 2 more cords. I’ve never seen one that had a Left RCA plug only, and ending with the 1/4". (Likewise with Right RCA only).

Is that what you’re saying??? argh

In any case, it seems you’re leading me in the direction that, once I have the proper stereo signal loaded on Audacity, I’ll be able to better address the shrillness/beating issue, which (as I said) I could still hear on the original tape?

Umm, btw, should I have exported the selected audio as a 32-bit float wav file, since that’s what it says about the whole track, in the Track Control Panel? :mrgreen: :blush: Just noticed the default was 16-bit PCM, and I didn’t bother changing that before I posted.


Yes. The “Instrument” jack socket is an input and the “headphone” socket is an output.
The Instrument input is mono (1 channel)
The headphone output is stereo.

When you need to record 2 channels (stereo), use the combo socket AND the instrument jack socket. The combo socket will be the left channel, the instrument jack will be the right channel.

Yes. Either two cables (cords) that have RCA at one end and 1/4" jack at the other, or a stereo cable that has two RCA plugs at one end and two 1/4" jacks at the other.
For example one of these: https://cpc.farnell.com/pulse/pls00251/lead-audio-2x-jack-to-2x-phono/dp/AV14463?st=rca%20to%201/4
or TWO of these: https://cpc.farnell.com/pro-signal/psg03269/6-35mm-mono-plug-to-phono-plug/dp/AV18857

Probably not.
I don’t think you can do anything about the vibrato because it’s burnt into the original, but with the correct leads you should be able to record in stereo rather than just mono.

32-bit float is ideal for audio production, but not necessary for the final product. The general rule is: Work in 32-bit float, export as 16-bit.

32-bit float is incredibly precise, and supports signals greater than 0 dB, which is great when you are editing and processing the audio, but it’s over the top for just listening to music. CD audio is 16-bit.

:bulb: :bulb: :bulb: This I did not know. :blush:

Which I think you tried to tell me in another thread, but I was not getting it. :blush: :unamused:

And as it happens, the more I listen to it, the more I remember from having been there for the live concert, that that was really kinda’ how the group sounded anyway…
Thanks for your unfailing patience!!

update: got recommended cables, sound MUCH better! Thank you!

Super :smiley:
Thanks for the update.

Is it typical for the two channels to be so clearly imbalanced, though? (disregard what the input settings are, my Macbook was not hooked up at the time of the screenshot; this was the AUP opened later)
Screen Shot 2021-02-08 at 10.49.08 AM.png
I made sure the dials were in the same position, but maybe that doesn’t necessarily mean the 2 channels’ signals will be the same levels (?)

The UM2 has separate controls (on the top) to set the levels for the two inputs. Adjust them so that the two channels are reasonably balanced. I would expect that the “Instrument” input may need to be set a bit higher than the “Line” input.

After recording you can tweak the left / right balance if necessary, using the track’s “Pan” slider (see: https://manual.audacityteam.org/man/audio_tracks.html#pan). You won’t see the waveforms change, just adjust it (if necessary) so that it sounds right. When you are happy with it, use “Tracks menu > Mix > Mix and Render” to “apply” the pan change to the audio.