Audio output level on Audio to SDI converter low

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Philip Francisca

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Audio output level on Audio to SDI converter low

PostFri Jun 30, 2017 3:11 am

Am using an Mini Audio to SDI converter. Did check the audio signal before connecting to the converter. However the audio level after the converter is very low. I connected to the converter through usb and adjusted the db level but still the output is very low. Any way to resolve this?
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AndrewYoole

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Re: Audio output level on Audio to SDI converter low

PostWed Apr 11, 2018 7:31 am

I'm having this exact issue.

THE SETUP

I'm setting up a monitoring link between a Voice Over booth and an edit suite. I only have one SDI line and one analog audio line between the rooms. The analog audio line carries the booth mic signal to the edit suite. The SDI line provides video and audio monitoring from the suite to the booth.

In the edit suite, I have an SDI video signal from an Ultrastudio 4K connected to a Blackmagic Audio To SDI Mini Converter. Analog audio from the suite's audio mixer Pre-Fade Aux Send goes to the Mini Converter into analog input (1). This allows me to create an independent mix for the booth, using the mixer's Aux bus. The Mini Converter SDI output connects to the main SDI line to the booth.

Logically, this setup should embed my analog audio into the SDI stream.

In the booth, the SDI line connects to a Blackmagic SDI to Audio Mini Converter. The SDI-thru out is connected to a video monitor. The analog audio output (1) is connected to a headphone amplifier.

THE PROBLEM

Audio levels in the booth are very, very low, barely audible. Far more than just a line level to digital line level discrepancy. It's totally unusable. If I connect the analog mixer Aux output directly to the headphone amp, there is plenty of level. Something is happening either in the conversion to and from SDI, or in the output from the SDI to Analog Mini Adapter. I

ADDED MYSTERY

When I first set it up it was working perfectly for about 10 minutes. Then it suddenly clicked down to the lower level and hasn't been useable since. I heard it as it happened.


So, any thoughts or suggestions?
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MadMistro

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Re: Audio output level on Audio to SDI converter low

PostThu Sep 03, 2020 8:54 pm

Hey there, work on commercials and have the exact same issue. I have close to zero embedded audio room coming from the mini converter but I have a massive amount of room out of my rolls RM424 mixer.
I've converted back to analog via SDI until I can find a better system, but even embedded direct from my software is better than through the boxes. I don't use that because I cannot control the levels and mute when we are recording sound.

Wonder where the disconnect is, I've considered getting a preamp but after testing the analog see that it would be a massive waste. There is obviously room out from the mixer any ideas out there?
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Robert de Wit

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Re: Audio output level on Audio to SDI converter low

PostFri Sep 04, 2020 3:17 pm

You are dealing with equipment made to broadcast standards. The clipping level for analog audio levels are +18dBu for EBU levels and +24dBu for SMPTE levels. The audio to SDI converter can be set to and is made for these levels.

If you are sending an average level of 0dBu you will have the required headroom of either 18dB or 24dB, however is you are using this as a distribution level to a consumer device it will sound much to low.

You will have to process and master your audio for final distribution according to current audio practices.

Robert
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McCarthy

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Re: Audio output level on Audio to SDI converter low

PostSun Jul 03, 2022 12:11 am

@Robert de Wit

I'm having the same issue. Bought this Blackmagic gear to convert VHS tapes to digital format. The audio level coming from the Audio to SDI converter is very low.

Nowhere in the product text could I find this spec.

My signals come from a prosumer JVC VHS recorder. What is the best path for "process and master your audio"?
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quentinj

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Re: Audio output level on Audio to SDI converter low

PostFri Feb 02, 2024 4:59 am

Wow, I came here too, basically I am also digitising VHS tapes - JVC prosumer deck, through a TBC, into the Analog to SDI converter and into an ultra studio recorder. Audio is very quiet. I was thinking I'd probably just fix it in post as I don't really trust analog amplification to be boosting the signal, but now I'm realising that something is probably wrong and I might need to fix it. Annoying after I've just done 14 tapes with each item separated by scene and the blackmagic device specs specifically advertise using it for VHS sources. The keen reader will find though that the blackmagic spec sheet - something we all probably read is actually a little misleading.

Specifically here is the description from the device:
"The ideal solution for converting analog component, s-video, NTSC/PAL composite to SDI video. Audio can be embedded from balanced analog or AES/EBU inputs. Now you can convert analog devices such as Betacam SP, VHS, set top boxes, gaming consoles and HDV cameras to incredible quality SD/HD-SDI video."

It is easy to skip straight to VHS, set top boxes and game consoles and completely miss the part that says 'balanced audio'.

OK, so it wants balanced audio input, which is about 6-10db louder than a line input which would account for the differences between professional line input and prosumer line input.

I find it misleading because I seriously doubt that we would get Balanced outputs on anything but professional VHS decks and certainly I'm not sure about set top boxes and gaming consoles -that part of the specs reads like this is for consumer equipment.

Anyway, from this I assume we should be able to boost the signal by 6-10db on the Mini Converter's software interface to compensate.

A quick test, this does solve the volume issue, but seems to introduce some noise reminiscent of old analogue cassette tape hiss. Perhaps that's already on the tape, introduced via not so great analog circuitry in the converter, or a problem in the player. I'm going to do some testing by routing through another analog capture device instead and bypassing the audio section of the Mini Converter. We shall see. Hopefully this helps someone else coming here though.

Marshalleq
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mpetech

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Re: Audio output level on Audio to SDI converter low

PostFri Feb 02, 2024 9:33 pm

Use a simple audio mixer to go from your VHS unbalanced audio to the balanced audio input of the converter. Put the mixer between the VHS and converter.

Something like this.
https://www.bhphotovideo.com/c/product/ ... mixer.html
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Howard Roll

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Re: Audio output level on Audio to SDI converter low

PostSun Feb 04, 2024 7:50 pm

Some analog tape hiss from an analog tape isn’t much of a surprise.

There’s no inherent level difference between balanced and unbalanced. More likely it’s that devices with balanced outs are going to be +4dbu, while unbalanced outs (especially RCA) are more likely to be -10dbv. A -10dbv signal is going to need 12-14db of gain, a mixer may help but with line level audio the preamps are much less of a concern. A mixer could be helpful to reduce the hiss/noise prior to capture through EQ and processing however.

Good Luck
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quentinj

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Re: Audio output level on Audio to SDI converter low

PostFri Feb 16, 2024 8:11 pm

So I just did some more testing, or put more accurately, some listening.

Even with boosting the db in the BM Analog converter by nearly 9.98db, then doing the rest in software via a normalise, the sound is significantly muddier than the original source when captured by just about any other video capture device. Its extremely noticeable and its not a 'in your imagination' volume issue. I had hoped getting a simple Balanced to unbalanced DI along with adding this gain would sort out any audio issues, but it is not to be.

@mpetech probably has it right to get a mixer, I was hoping to avoid this but this is now what I'm going to do also. I just hope the muddiness / loss of high frequency is not something inherent in the Blackmagic device. Turns out I was right not to trust the BM gain controls!

Before I blow more cash, has anyone seen a loss of audio quality by using the direct in Audio TRS jacks in the BM analog video to sdi converter when using proper balanced sources? As that would confirm the architecture of this device is faulty and not to bother with it any longer.

Thanks.
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quentinj

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Re: Audio output level on Audio to SDI converter low

PostSat Feb 17, 2024 4:16 am

Today I purchased a Macki pro FX6v3 to help with troubleshooting. This has made a world of difference for the audio levels, however the dullness as previously mentioned has not resolved itself. To isolate that I used a separate audio capture device and old Canopus FireWire ADVC110, on this the audio is also dull, which seems to indicate the VCR is at fault. To be absolutely sure I would have to do more testing which is hard work at the moment as I only have the use of one arm. But the previous recording with insanely higher audio fidelity was created on a lower quality VHS device coupled with a cheap pinnacle USB capture device. So from that I tend to think it would be the VCR player rather than the capture device creating the different quality outputs.

The mixer I purchased clearly has a greater degree of control with levelling up the audio so I'm very happy with that and alsoI can use it to tweak the treble a little to offset the dull audio though it is clearly not ideal.

Thankfully this probably means that none of my black magic devices have a faulty design or an overly compressed audio track, but when I get my arm back I will be doing some full tests and posting them on my website.

Phew! I was actually quite worried about this one!

Marshalleq

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