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I don't understand converters

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I don't understand converters

Postby songwriter » Sat Sep 21, 2019 6:06 pm

I need to understand once and for all about converters.

I know what they do (convert analogue to digital and vice versa) and I recently posted a question about whether upgrading from RME fireface UFX would improve the overall sound quality of my studio setup. The resounding answer was no.

But today I read this in an article:

When did you first hear about the Rupert Neve Designs RMP-D8?
I heard about it maybe a year ago. My friends over at Rupert Neve sent me one to check out and I just fell in love with it. I use a bunch of different converters here like Lavrys, Pacific Microsonics, Burl, Dangerous and Forsells. I’m a big fan of mixing and matching different converters, depending on the program material. But, I instantly fell in love with RMP-D8. It’s a really good sounding unit with tons of headroom and it’s been really versatile. I’ve used it on a ton of projects.


So I am more confused now than before. This engineer mixes and matches converters?? Why? What's the difference in sound and why would it have an effect on program material?

I also understood that the converter acts as the audio interface, like the fireface UFX. Is that right? Or can you have a different converters like the ones above integrated into your normal recording setup (in my case with the UFX) to change at will?

Totally confused here!
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Re: I don't understand converters

Postby molecular » Sat Sep 21, 2019 6:29 pm

Having read your other thread I'd personally suggest the following (not in the order you asked)

1. The RME UFX has convertors built in, yes, so you can plug an analogue signal in and have the digital conversion delivered to your computer. But it also has digital inputs on ADAT, so you can buy additional convertors with an ADAT output to connect to those, thereby gaining a greater number of analogue inputs using other convertors.

2. Different convertors will affect the sound in different ways, but the differences are miniscule compared to most other factors in a studio. When you hear somebody discussing choosing different convertors according to programme material you must assume that the level of equipment and the recording/mixing environment and their own ability is so finely honed that they are focussing on incredibly subtle differences.

3. Most of us need to ask ourselves if we are at that point in our practise and our gear - and to cut a long story short the answer is always that whatever money or time we have to improve our sound needs to be spent on things like skills, room treatment, speakers, mics, better performance (if we are recording ourselves), rather than on convertors. These other things will make a bigger difference on a completely different scale. RME convertors are very very good and getting any better is something you might consider doing after absolutely everything in your practise is absolute perfection.

(edit PS - I think there are maybe some exceptions to this in workflow - because convertors and interfaces come in a fairly ramshackle collection of I/O configurations and routing capabilities and internal mixers etc. so it makes sense that you might need to "upgrade" if you want to work in a way that your interface doesn't allow, but this isn't about sound quality and the RME is pretty flexible so if you can do what you want to do then do it :) )
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Re: I don't understand converters

Postby songwriter » Sat Sep 21, 2019 6:33 pm

Thank you! :bouncy:

Appreciated
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Re: I don't understand converters

Postby Hugh Robjohns » Sat Sep 21, 2019 7:28 pm

songwriter wrote:I need to understand once and for all about converters.

Let me know when you do because then you can explain it all to me too! :-)

This engineer mixes and matches converters?? Why?


Because he can hear, or thinks he can hear, audible benefits from mixing and matching, in the same way the guitarists pick different guitars for their different characteristics when playing different material. Or perhaps he just thinks its a cool thin to do because it gives them impression he is more discriminating than others! ;-)

What's the difference in sound and why would it have an effect on program material?

First, the differences tend to be extremely subtle, requiring really top-notch monitoring Speakers and a very good listening acoustic to hear them. Also, the differences tend to be specific to different kinds of material, and its average and peak signal level.

Converters are complex devices. There is some analogue input/output circuitry, with all the associated power supply/headroom/grounding/crosstalk/slew rate/frequency response considerations. And then there's the digital clocking/jitter/grounding/crosstalk. And that's before the choise of converter chip with the different topologies, delta-sigma sample rates and bit depth, decimation/over-sampling filters, anti-alias/reconstruction filtering, dithering, and so on and so forth.

In other words there are a very large number of variables, many of which interact in complex ways, and different manufacturers choose different compromises and approaches depending on their own design preferences, costs, etc etc...

As a result, there are some small differences between different converters. They're almost always incredibly small, but they can sometimes be detected and deemed to make a difference -- like choosing different brands or gauges of strings on a guitar...

I think I've noticed subtly different characters between my Crookwood, Drawmer, Apogee, Focusrite, Audient, and RME A-Ds, and between my Crookwood, Grace Design, BenchMark, CambridgeAudio, and Apogee D-As... But i doubt i could reliabl identify them in a double-blind test, and its certainly not enough that I'd choose one over another for a specific project -- I just use whichever is most convenient at the time, and no one has ever noticed, let alone complained about my choice!

And where I have noticed a difference at 44.1k, I'm yet to do so at 96k! :-)

I also understood that the converter acts as the audio interface, like the fireface UFX. Is that right? Or can you have a different converters like the ones above integrated into your normal recording setup (in my case with the UFX) to change at will?

Most conventional interfaces include Intergrated A-D and D-A converters. However ther some digital-only interfaces, and many conventional interfaces include some digital I/O -- so these allow external,converters to be used instead of, or as well as, the internal ones (if present).
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Re: I don't understand converters

Postby songwriter » Sat Sep 21, 2019 7:35 pm

Thanks Hugh!

Would you mind explaining why you have so many converters? What made you want more than one converter unit?
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Re: I don't understand converters

Postby Hugh Robjohns » Sat Sep 21, 2019 7:59 pm

Gear lust, mostly! :lol: But the nature of my job means its important to have a wide choice of converters for comparative purposes... Or that's what I tell the accountant, anyway! ;-)

The Crookwoods are integrated into my mastering console. The Benchmark (I have two, actually) and Grace Design are used mainly as headphone amps and on-location as monitor controllers. I bought the Apogee because of its extensive I/O and dithering versatility which was very handy back in the days of recording to DAT and CDR. Audient and Focusrite converters are built into mic preamps, but accessible externally too. I use the Drawmer as a floating A-D that retains its performance when externally clocked... which few converters manage to do, and so is very useful! And i bought the CambridgeAudio DacMagic because of its switchable reconstruction filter types.

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Re: I don't understand converters

Postby songwriter » Sat Sep 21, 2019 8:18 pm

Wow! That's some setup. I share your gear lust addiction haha. What's your favourite preamp out of interest?
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Re: I don't understand converters

Postby Hugh Robjohns » Sat Sep 21, 2019 8:35 pm

Depends on the circumstances and requirements.

I guess my fave is a four-channel GML which is very simple, but sounds genuinely transparent and effortless. I love the no-frills purity of design.

The Focusrite ISA 428 is very versatile and has integral converters, with just a hint of character. The SSL VHD has dial-up character in abundance, while the Audient ASP880 is pretty clean (and also has integral conversion), and packs a lot of channels in a small space.

For passive ribbons I use an AEA TRP preamp. And then there are more preamps in my Calrec Minimix2, Yamaha dm1000, and Soundcraft LM1 consoles. I also and a couple of vintage Calrec preamps of a similar style to the classic Neve 1073 modules (but with better performance... ;-) ) that I must finish racking up...

I also have a two-channel battery-powered Sound Devices preamp with MS conversion that I often use for quick mic checking at my desk, or for extra mic inputs with my Nagra VI on location (I use the ISA with it if I need eight mic channels).

Oh yes, and the SADiE LRX location recorder has 16 more mic preamps, plus I can add another 16 using the Audient, ISA, GML and or SSL if needed.

Good grief that's a lot of preamps....
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Re: I don't understand converters

Postby songwriter » Sat Sep 21, 2019 8:38 pm

That sure is!!! I just purchased an SSL VHD pre. It's on offer this month. I'm looking forward to trying it out :)
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Re: I don't understand converters

Postby The Elf » Sat Sep 21, 2019 9:19 pm

Because he can hear, or thinks he can hear, audible benefits
I'd reduce that to 'thinks he can hear, or is financially advantaged to say he hears...' ;)

Cynical? Moi? :beamup:
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Re: I don't understand converters

Postby James Perrett » Sat Sep 21, 2019 9:27 pm

Hugh Robjohns wrote:Good grief that's a lot of preamps....

Your post got me thinking Hugh and I've totted up 92 channels of balanced mic preamps here - with a few more unbalanced mic inputs on various tape machines too.

I also counted 60 channels of A/D of varying quality and 52 channels of D/A convertors.

It is amazing how much gear accumulates over the years.
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Re: I don't understand converters

Postby Hugh Robjohns » Sat Sep 21, 2019 11:57 pm

:D it certainly is!
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Re: I don't understand converters

Postby blinddrew » Sun Sep 22, 2019 9:28 am

Briefly dropping back to Hugh's collection of converters...
Is there any technical advantage to using the balanced outputs on the dacmagic over the unbalanced ones?
Years ago a colleague suggested that there was but I can't remember what their argument was.
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Re: I don't understand converters

Postby The Elf » Sun Sep 22, 2019 9:58 am

Generally speaking, balanced gives more signal for less noise. If you have the option to use a balanced connection, use it.

Cue a clutch of 'ah, but...' responses! ;)
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Re: I don't understand converters

Postby Hugh Robjohns » Sun Sep 22, 2019 10:00 am

blinddrew wrote:Is there any technical advantage to using the balanced outputs on the dacmagic over the unbalanced ones?

The balanced outputs should allow a ground-free connection -- so freedom from ground-loops -- and much better immunity from external interference (assuming it's feeding a balanced destination, of course).

It should also provide at least a 3dB improvement in the signal-to-noise ratio compared to the unbalanced outputs. I've not run a suite of measurements on my original DACMagic converter box (but I will now I'e reminded myself that I should)... but reviews I've seen suggest the balanced outputs have something like 2dB lower distortion products than the unbalanced outputs.

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Re: I don't understand converters

Postby Hugh Robjohns » Sun Sep 22, 2019 10:09 am

The Elf wrote:Generally speaking, balanced gives more signal for less noise. If you have the option to use a balanced connection, use it.

Cue a clutch of 'ah, but...' responses! ;)

The 'ah but' is only because the noise benefit depends on the exact balanced output topology being employed... but in general you're right to say that there can be a 3dB benefit in the signal-noise ratio.

The way it works is this: assuming the balanced output is the symmetrical/inverted type, where the two legs carry coherent, same amplitude, signals but in opposite polarities, then the addition of those two signals at the balanced differential receiver produces an output which is double the amplitude of either leg individually -- meaning the output is 6dB greater.

However, the noise contribution from the output driving electronics being conveyed over each leg is not coherent, so its addition at the receiver results in a 3dB rise in the noise amplitude.

Thus, the wanted signal is 6dB greater but the noise is only 3dB larger, and so there is 3dB more signal than noise overall... as per the Elf's statement above!

As I said, though, there are caveats because this benefit is not available from all forms of balanced source configurations.

And for me, this very modest improvement in S-N ratio is generally irrelevant anyway because the noise floor of decent electronics is so low that 3dB really doesn't make any audible difference in the vast majority of applications. What really does make a big difference, however, is the avoidance of ground-loops and the minimisation of external interference -- and that's why I always use balanced connections whenever they are available!

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Re: I don't understand converters

Postby The Elf » Sun Sep 22, 2019 11:05 am

Ah, but... my version was shorter! :lol: ;)
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Re: I don't understand converters

Postby Hugh Robjohns » Sun Sep 22, 2019 11:50 am

it always is! :D
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Re: I don't understand converters

Postby Wonks » Sun Sep 22, 2019 12:14 pm

Indeed. Elf's version of John Cage's 4'33" is only 2'05".
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Re: I don't understand converters

Postby Hugh Robjohns » Sun Sep 22, 2019 12:14 pm

:lol: :clap:
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