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Building a 70s system??

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Re: Building a 70s system??

Postby Tim Gillett » Sat May 30, 2020 10:52 pm

I recorded a lot of small live acoustic performances with my old Zoom H4 with its internal XY pair. On test the noise floor of the mics/pres was above the 16 bit noise floor so I never used 24 bit. On the small 4GB card, that gave me 50% longer record time.
Once on a big cassette archive digitizing project I suggested 16 bit was more than enough but was howled down for compromising "standards". So we used 24 bits and still many captures were digitally clipped...
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Re: Building a 70s system??

Postby MOF » Sat May 30, 2020 11:41 pm

we used 24 bits and still many captures were digitally clipped...
The whole point of using 24bits is the massive headroom you can leave to prevent distortion and still not have any hiss from boosting the level in post production. You can’t have left enough headroom.
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Re: Building a 70s system??

Postby Tim Gillett » Sun May 31, 2020 12:00 am

Correct but we were dealing with a known format, cassettes. So the maximum possible level was also known. I set it up with headroom of 5 db above the level of a saturated Metal cassette. But I was overruled by someone else who thought they knew better how to set record level. That's when the clipping began.
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Re: Building a 70s system??

Postby Mike Stranks » Sun May 31, 2020 9:37 am

Tim Gillett wrote: So we used 24 bits and still many captures were digitally clipped...

But that wasn't anything to do with word-length; that was to do with not setting levels correctly. 24-bit means that you have more headroom to play with. If one (not you in this case) doesn't take advantage of that then the discussion about 16-24 becomes irrelevant.

In the situation you describe I would still have recorded at 24-bit to cater for the possibility of tweaking in post. However, I probably wouldn't have stored the final archive at 24-bit.

I am currently dealing with a continuous stream of recordings from other sources... most of which are .m4a. These are copied straight into 44.1/24-bit .wavs purely because of issues of post-processing. The final product is an .mp4 video played-out via YouTube, but I'm keen to give myself as much wriggle-room as possible through the editing/post/mixing process.

... and at that point :wave: on the topic of 24/16... :)
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Re: Building a 70s system??

Postby Tim Gillett » Sun May 31, 2020 11:52 am

Mike Stranks wrote:
Tim Gillett wrote: So we used 24 bits and still many captures were digitally clipped...

But that wasn't anything to do with word-length; that was to do with not setting levels correctly. 24-bit means that you have more headroom to play with. If one (not you in this case) doesn't take advantage of that then the discussion about 16-24 becomes irrelevant.

Quite but but did you read my explanatory post :

Tim Gillett wrote:... we were dealing with a known format, cassettes. So the maximum possible level was also known. I set it up with headroom of 5 db above the level of a saturated Metal cassette. But I was overruled by someone else who thought they knew better how to set record level. That's when the clipping began.

With an absolute peak level of -5dbFS the noise floor of the analog cassette was way above the noise floor of 16 bit. Many recordings had a dynamic range of 8 bits or less. Many recorded on machines with an internal microphone had probably less than 5 bits DR and speech could verge on inaudible.

Mike Stranks wrote:In the situation you describe I would still have recorded at 24-bit to cater for the possibility of tweaking in post. However, I probably wouldn't have stored the final archive at 24-bit.

How would recording the cassettes in 24 bit re 16 bit assist in post production?
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Re: Building a 70s system??

Postby Hugh Robjohns » Sun May 31, 2020 11:56 am

Tim Gillett wrote:So we used 24 bits and still many captures were digitally clipped...

Adding my own voice to the concenaus just for the sake of clarity, the clipping described obviously had nothing to do with the chosen wordlength, and everything to do with utter incompetence and poor supervision/project management.

I agree that 16 bit capture -- with competent input level control -- would have been adequate given the maximum dynamic range capability of the cassette format.

However, had it been my project today I would have captured in 24 bits simply because all modern interfaces do by default, and the concern about saving storage space really isn't a relevant issue for the production stage and hasn't been for decades.

After post-production of the tracks I would have saved/stored the processed files in a 16-bit format for convenience and to reduce the long-term archive capacity required.
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Re: Building a 70s system??

Postby Tim Gillett » Sun May 31, 2020 1:51 pm

Tim Gillett wrote:So we used 24 bits and still many captures were digitally clipped...

Hugh Robjohns wrote:Adding my own voice to the concenaus just for the sake of clarity, the clipping described obviously had nothing to do with the chosen wordlength, and everything to do with utter incompetence and poor supervision/project management.

Of course the clipping had nothing to do with the wordlength. But I did go on to explain how I initially set up the gain staging. These were based on my own tests and measurements of the maximum saturated output of a Metal cassette. Then to that I added a record headroom of 5db. That is why while that system remained in place, which it did for a couple of months, we had no clipping whatsoever, across two separate capture installations and many cassette transfers.

Indeed the clipping had nothing to do with wordlength but neither did it have anything to do with my work or directives. Rather in spite of them. The clipping occurred for a different reason. Obviously I cant say much here about what then ensued and why, but basically what do we expect happens when fixed record levels which are already relatively high but quite safe, are increased significantly?

Hugh Robjohns wrote:I agree that 16 bit capture -- with competent input level control -- would have been adequate given the maximum dynamic range capability of the cassette format.

Perfectly adequate I would have thought? The one exception in the back of my mind was the possibility in the archive of a dbx encoded and decoded cassette. It may still have been fine with 16 bit capture and careful record levels but we may never know for that project as AFAIK no such recording turned up in the archive of many cassettes.

Hugh Robjohns wrote:However, had it been my project today I would have captured in 24 bits simply because all modern interfaces do by default, and the concern about saving storage space really isn't a relevant issue for the production stage and hasn't been for decades.

Again this was a cassette digitisation project and a very large one at that. ISTR the ongoing storage requirements surprised the IT department.

Hugh Robjohns wrote:After post-production of the tracks I would have saved/stored the processed files in a 16-bit format for convenience and to reduce the long-term archive capacity required.

My understanding was that the 24 bit files would not just be used for the capture and then truncated down to 16 bit for posterity, but would be preserved as full 24 bit stereo wave files (24/48), along with the processed co masters.
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Re: Building a 70s system??

Postby Hugh Robjohns » Sun May 31, 2020 3:39 pm

Tim Gillett wrote:I did go on to explain how I initially set up the gain staging.

For the avoidance of doubt, I'm not suggesting that the utter incompetence and poor supervision/project management was yours in any way, Tim, or indeed of your making.

Your description of how you set the system up initially was clear and seemed well thought out. My comment refers specifically to those subsequently operating the system and/or those supervising it who (a) misaligned it and (b) apparently didnt realise and correct their error. That kind of thing is very irritating... But not uncommon.

My understanding was that the 24 bit files would not just be used for the capture and then truncated down to 16 bit for posterity, but would be preserved as full 24 bit stereo wave files (24/48), along with the processed co masters.

That seems rather pointless and wasteful of long-term data storage capacity given the known dynamic range of the cassette material, as we have agreed previously...
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Re: Building a 70s system??

Postby Synthman4 » Sun May 31, 2020 8:06 pm

mikehende wrote:So guys, I have been dancing all around this for a long time now but seems I had not considered the most basic question which is, if I put together all 70's equipment but play music from my pc or fm radio, would I still get analog sound please?
Unfortunately not mate. All PC's are digital now. Although you can buy really expensive samplers where you can capture a very good analogue type of sound but not exactly like it.
If you're trying to play old records, you can buy USB record players that allow you to capture the audio and convert them to wavs which are better quality than mp3s.
If you mean use old 70's synths and drum machines then just by a really good usb audio interface over a £1000 and plug your 70's synths into them.
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Re: Building a 70s system??

Postby Hugh Robjohns » Sun May 31, 2020 8:12 pm

Synthman4 wrote:Unfortunately not mate. All PC's are digital now.

Yes.... I much preferred the sound I got with my old Babbage analogue PC... :lol:

Sorry... Couldn't resist!
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Re: Building a 70s system??

Postby innerchord » Sun May 31, 2020 9:03 pm

Hugh Robjohns wrote:Yes.... I much preferred the sound I got with my old Babbage analogue PC... :lol:

Were you running the original Difference model or the Analytical upgrade?
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Re: Building a 70s system??

Postby zenguitar » Sun May 31, 2020 10:19 pm

Ah yes! The math co-processor was an optional extra, reminds me of the 286 ;)

Andy :beamup:
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Re: Building a 70s system??

Postby Sam Spoons » Sun May 31, 2020 11:06 pm

Bloody youngsters, I started computing with an abacus, my first computer was a ZX81 and my first 'PC' an 8086, you don't know you're born....... :D :D :D
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Re: Building a 70s system??

Postby Synthman4 » Sun May 31, 2020 11:12 pm

Hugh Robjohns wrote:
Synthman4 wrote:Unfortunately not mate. All PC's are digital now.

Yes.... I much preferred the sound I got with my old Babbage analogue PC... :lol:

Sorry... Couldn't resist!

Stop picking on me, you sod.
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Re: Building a 70s system??

Postby zenguitar » Mon Jun 01, 2020 12:26 am

Synthman4 wrote:
Hugh Robjohns wrote:
Synthman4 wrote:Unfortunately not mate. All PC's are digital now.

Yes.... I much preferred the sound I got with my old Babbage analogue PC... :lol:

Sorry... Couldn't resist!

Stop picking on me, you sod.

There is a difference between making a general joke and picking on someone.

The joke isn't an attack on you. Your comment just opened a door to work a variation an the never ending promotion on the benefits of analogue and the perceived failings of digital. Nothing was aimed at you, and as you can see, a couple of others picked up the baton and ran with the same joke.

Andy :beamup:
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