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Author Topic: Newbie Question Regarding External A/D  (Read 3206 times)

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Offline cottle

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Newbie Question Regarding External A/D
« on: May 03, 2009, 12:00:35 AM »
So I'm in the process of piecing together my first rig.  I've scored some used AKG 460's, a Denecke PS-2 and AD-20, and my t-bar, stand and shockmounts are on order from B&H.  I bought the AD-20 more to use as an inexpensive preamp than for its ADC, but I can't have one without the other in that unit.  The deck that I was looking at most closely is the Marantz PDM-661.  I've also looked at some of the lower price-point models like the R09 and the iRiver, among others. 

I realize that if I get the Oade-mod 661, I probably won't need the PS-2 or AD-20.  The 661 provides phantom power, and it's my understanding that Doug's modification beefs up the internal preamps enough to be able to run mic-in w/ the AKG's.  Am I correct so far?

So lets say my setup is Mics>PS-2>AD-20>Deck, and we'll assume the deck (any of the models listed above, and then some) is capable of 24/96 recording.  The AD-20 is technically capable of producing a 20-bit output, but from what I hear it's actual capability is only 16.  If I've got the 16-bit/44.1 output from the Denecke going into a deck than can do 24/96, will I run into problems if I try to set the deck to record at say 24/48 (or above)?  I'd like to be able to archive and seed everything I tape (assuming I'm satisfied enough with the end product), so I'd prefer to be able to record FLAC quality shows.  Will the change in sampling rate cause any issues?  Would I be better off to run mic-in if I'm using the modded 661?  I'm thinking (and I know absolutely nothing on these topics, that's why I'm here) that whatever the output of the Denecke is won't matter, since the deck is still gonna process the sound at whatever levels I set it at, and the internal ADC will resample everything anways.  Does it make a difference if I run digi in to the recorder, or if I go analog in and let the internal ADC do the work?  Is that even possible, to go from a digi out to an analog in, w/ no conversion in between?
Sorry for all the questions, I did some searches first, and didn't see what I was looking for.  Any input is much appreciated!

Thanks.



Offline cottle

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Re: Newbie Question Regarding External A/D
« Reply #1 on: May 03, 2009, 10:23:16 PM »
Thanks for the feedback.  That pretty much confirms what I suspected, which is that I won't need the PS-2 or AD-20 if I'm using the modded 661.  I might be better off using the recorder's internal A/D, since it can do up to 24/96, then I can always resample it down after the fact, to transfer to CD. 

Offline rsimms3

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Re: Newbie Question Regarding External A/D
« Reply #2 on: May 04, 2009, 08:38:42 AM »
Of the decks you mentioned, only the iRiver h120 can take an optical signal.  Also, the AD20 can only output a 16/44.1 signal.  Your other option is a JB3.  I am not familiar with any other deck that takes an optical signal.  If there are others, I am sure someone will mention them. 
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Offline cottle

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Re: Newbie Question Regarding External A/D
« Reply #3 on: May 04, 2009, 11:42:44 AM »
Thanks Simms. 
So, if I want to record at anything higher than 16/44.1, I should just remove the AD-20 from the equation, right?  I guess if I do that, I'll need to find another cheap pre-amp alternative, unless I go with the modded 661. 

When you say that the 661 can't take an optical signal...what about the other digi output?

I also have the miniplug to coax digi out...so I could use that into the 661's digi in (coax), right? 


Offline rsimms3

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Re: Newbie Question Regarding External A/D
« Reply #4 on: May 04, 2009, 11:52:39 AM »
Yes, I forgot about the coaxial digital output on the AD20.  I never used the coaxial output and haven't used my AD20 in ages.  Yeah, any recorder that takes coaxial should work with the AD20, but you are still limited to 16/44.1.  I am not familar with the 661, but if it has coax in then it should work.  A modded 661 would probably be the way to go too.  Also, the AD20 has an automatic minimum 12 or 15db gain even when set to 0.  This is how it was built.  For some things, this is no problem, but for louder shows, it could be an issue.
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Offline cottle

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Re: Newbie Question Regarding External A/D
« Reply #5 on: May 04, 2009, 12:39:08 PM »
Thanks again. I guess I just jumped the gun when I bought the PS-2 and AD-20, but the price was right, and I figured it was probaby the cheapest phantom power/preamp solution I would find.  I guess all that's left at this point is to get the deck and run some tests to see what works and what doesn't.


Offline rsimms3

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Re: Newbie Question Regarding External A/D
« Reply #6 on: May 04, 2009, 01:18:45 PM »
Thanks again. I guess I just jumped the gun when I bought the PS-2 and AD-20, but the price was right, and I figured it was probaby the cheapest phantom power/preamp solution I would find.  I guess all that's left at this point is to get the deck and run some tests to see what works and what doesn't.



I went with the same combo when I started taping with large mics.  It's a good combo and a lot of people start out with it because of the dual digital formats it outputs.  I have since moved on to a Busman modded UA-5 which I like a lot.  It seems like the popular thing now is a SD7xx or High End Preamp (V3, etc.) > SD7xx.
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Offline cottle

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Re: Newbie Question Regarding External A/D
« Reply #7 on: May 04, 2009, 03:56:29 PM »
Yeah, if I had money for a V3 or SD722, I'd totally go that route.  I'm trying to get into this on somewhat of a budget, and I'm figuring out that's easier said than done.  I figure if I can keep it simple now, there will always be room to upgrade in the future, one component at a time. 

Offline rsimms3

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Re: Newbie Question Regarding External A/D
« Reply #8 on: May 04, 2009, 04:41:38 PM »
Yeah, if I had money for a V3 or SD722, I'd totally go that route.  I'm trying to get into this on somewhat of a budget, and I'm figuring out that's easier said than done.  I figure if I can keep it simple now, there will always be room to upgrade in the future, one component at a time. 

Definately a good starter rig with potential to various recorders having both digital outputs.  I would go with a SD702, but also lack the funds.
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Offline ghellquist

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Re: Newbie Question Regarding External A/D
« Reply #9 on: May 04, 2009, 06:51:42 PM »
It is worth to remember that the most important part is everything that comes before the mic preamp. All the things there will influence the sound quality more than anything after. (Now, we are not talking cassettes here).

The performers, the songs, the PA, the room, the mics choosen, the position in the room, the height above floor, each of these things is more important than the preamp and digital stuff. Once captured by the mic though, it will from a quality point of view only go downhill.

I am not saying it does not make a difference, but you pay dearly for very small improvements.

// Gunnar

Offline DSatz

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Re: Newbie Question Regarding External A/D
« Reply #10 on: May 04, 2009, 10:59:16 PM »
There is some incorrect information in this thread. The AD-20 in fact puts out a 20-bit bitstream, and within the dynamic range available, has a 20-bit converter. When used as a 16-bit A/D on the other hand it has inadequate dither; the defense given on the Denecke Web site for this is transparent gibberish. As I recall the actual dynamic range of the unit was somewhere around 18 bits, definitely greater than 16, but this would depend on the gain settings of course. I will be glad to measure mine again the first chance I get.

--best regards
music > microphones > a recorder of some sort

Offline Kyle

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Re: Newbie Question Regarding External A/D
« Reply #11 on: May 05, 2009, 01:35:24 AM »
Of the decks you mentioned, only the iRiver h120 can take an optical signal.  Also, the AD20 can only output a 16/44.1 signal.  Your other option is a JB3.  I am not familiar with any other deck that takes an optical signal.  If there are others, I am sure someone will mention them. 
 

The Sony PCM-D50 has an optical in.


Ok, here is what I am wondering.

If the AD20 outputs a 20bit, 44.1kHz signal and you set the receiving deck to record at 24/44.1, would the deck pad the AD20 output word with 4 extra 0's? I know if I send a 24/44.1 or 24/48 signal to my Fostex CR200 CD recorder, it locks on to the 44.1 or 48kHz sample rate and just truncates the extra 8 bits. If someone has the gear to try it out please do so. If one were to use the Marantz PMD-661 with the AD20 and it will take the 20/44.1 signal the results could be very nice.

I wonder if the same concept would work the the Apogee AD1000. It outputs a 20bit signal if you do not use the UV22 mode, correct? It would be great to be able to capture said signal. The AD1K's sound so nice - I wonder how it would sound at the full 20bit output? I have never heard it that way (minus the UV22 processing). Makes me wish I still had mine around....


edit: providing that http://taperssection.com/index.php/topic,120916.0.html is not an issue...
« Last Edit: May 05, 2009, 02:27:41 PM by Kyle »
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Offline Scuzzi

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Re: Newbie Question Regarding External A/D
« Reply #12 on: May 05, 2009, 09:57:25 PM »
Kyle,

I just tried the exact scenario you were describing with my AD-1000 and MTII.  The MTII accepts the output from the AD-1000 with the AD-1000 set to 20bit and the MTII set to 24bit *or* 16bit.  The AD-1000 manual says specifically that it sends a 20bit word length with that setting, so I'm not sure what exactly is happening nor do I now how to check a wav file to determine what bit depth it's at.  Any idea what's going on here?

Offline Kyle

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Re: Newbie Question Regarding External A/D
« Reply #13 on: May 05, 2009, 10:24:58 PM »
Kyle,

I just tried the exact scenario you were describing with my AD-1000 and MTII.  The MTII accepts the output from the AD-1000 with the AD-1000 set to 20bit and the MTII set to 24bit *or* 16bit.  The AD-1000 manual says specifically that it sends a 20bit word length with that setting, so I'm not sure what exactly is happening nor do I now how to check a wav file to determine what bit depth it's at.  Any idea what's going on here?


Great news! Good to know that it works. Are you going to run the AD1K in the field at 20bit? I am very curious as to how it sounds. With the MTII set to 24bit it should capture the full output of the AD1K. May have to hit the bay and find me a new (old) one....  :hmmm:
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Offline Scuzzi

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Re: Newbie Question Regarding External A/D
« Reply #14 on: May 05, 2009, 11:09:20 PM »


Great news! Good to know that it works. Are you going to run the AD1K in the field at 20bit? I am very curious as to how it sounds. With the MTII set to 24bit it should capture the full output of the AD1K. May have to hit the bay and find me a new (old) one....  :hmmm:

Well that's the question.  Would it really be worth it to do that when I'm still looking to get down to 16bit eventually?  I think the answer is likely no, just stick with the UV16 output.  I am however a complete novice in these matters.  What do you guys think?


Offline ghellquist

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Re: Newbie Question Regarding External A/D
« Reply #15 on: May 06, 2009, 03:08:28 AM »
No need to worry. The 20 bit AD actually outputs a 24 bit signal already padded with zeros.

As to if you should run 24bit or 16 bits -- my suggestion is to run 24 bits. You get a few extra bits of signal that you might want to use in post to raise signal levels. Keep them and you have the option, throw them away and they are gone forever.

The whole point of 24bits is a bit inflated. No AD for audio use (hear me, none) really works out at 24 bits. It is a lot of marketing BS calling it 24 bits. The limiting factor is generally the analog circuits that add enough noise to effectively make it about 18 bits, perhaps up to 20 or 21 for the really expensive stuff. I even remember testing a unit (Edirol R1) claiming 24 bits that really only had about 15 bits due to high noise levels.

Boiled down to the bottom line, better go with the more honest statement of 20 bits.

// Gunnar

Offline Scuzzi

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Re: Newbie Question Regarding External A/D
« Reply #16 on: May 06, 2009, 07:17:43 PM »
No need to worry. The 20 bit AD actually outputs a 24 bit signal already padded with zeros.

As to if you should run 24bit or 16 bits -- my suggestion is to run 24 bits. You get a few extra bits of signal that you might want to use in post to raise signal levels. Keep them and you have the option, throw them away and they are gone forever.

My question is will I be losing some kind of quality by dithering down to 16bit in Audacity as compared to using the built-in UV22 dithering on the AD-1000.  Is it really the same process or not at all?

Offline ghellquist

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Re: Newbie Question Regarding External A/D
« Reply #17 on: May 07, 2009, 06:15:35 AM »
My question is will I be losing some kind of quality by dithering down to 16bit in Audacity as compared to using the built-in UV22 dithering on the AD-1000.  Is it really the same process or not at all?

You might see gains or losses. I believe that UV22 is considered a good dithering algorithm, what Audacity uses I am not sure of. In post you do have a lot of choices though, I believe r8brain (found for free from voxengo, alas only windows) is a respected choice.

You would definitely gain a lot more than any loss if going more than 16 bits allows you to adjust gain upwards in post. Going 16 bits, you get what you have including all safety margin on volume. Using the extra bits allows you to continue having a safety margin when recording, raising volumes afterwards and still not increase the noise floor level.

Still, a lot of these things are totally swamped by the decisions you make on location on choice of mics and positioning of them. I would not spend too much thought on them, or as the Nike slogan used to say, just do it.

// Gunnar

 

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