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ballenberg · Posted: Tue Sep 05, 2017 7:52 am Post subject: Potentially dumb question

Is there such a thing as a good, pro a/d converter that is just that..not a preamp also..... Or is that not actually a thing? And of course, suggestions are most welcome!

FinMac · Posted: Tue Sep 05, 2017 8:48 am Post subject: Not a dumb question at all

Yes, there are many like that. One of the best would be the Lynx Hilo. It is a bit pricy at over 2K.

Ross Martin makes a very good one, the PCM4222, for a great price, around 400 dollars, but the wait time could be over half a year!

I love my PCM4222 as it has an SPDIF Toslink connection that connects directly to a Mac Mini Smile

There are a lot of options, but those are both good ones Smile

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Bish · Posted: Tue Sep 05, 2017 10:26 am Post subject:

I've investigated this issue a number of times over the years, and always come up with the same answer. Apart from the cheap'n'cheerful Begringer $25 units which do a fine job if you only want up to 48kHz 16-bit if I remember correctly, there is nothing that is cost effective.

If you consider a minimum requirement is a 96kHz, 24-bit DAC, and you consider that some pre-amps actually have very fine DACs built into them... then the logical conclusion is to buy a pre-amp/DAC where you can physically by-pass the pre-amps. I've done this with my old Apogee Duet (where you can actually hear the reed relays switching the pre-amp circuitry in/out)... and now with my Audient iD22... where there are separate input jacks that connect directly to the converter (by-passing the pre-amp). I think the Apollo units do this as well... and I'm sure there are plenty more in the "upscale" range.

The PCM4222 seems to address the issue... but the wait time is long, and for roughly the same money, I'd probably opt for an iD22 and by-pass the pre-amp.... and then you have spare pre-amps for when the Avalon keels over Smile

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ballenberg · Posted: Tue Sep 05, 2017 1:09 pm Post subject:

Which it occasionally does...snap, crackle, pop, time for new tubes. Smile

That sounds like a good plan to me...so, I can plug my 1/4 jacks right into the id22 and then to Windows computer, is that correct? (Like I said, I don't quite know this stuff....I'm still using and very happy with my PCI Mia card but its usability is not finite... ) Thanks!

ballenberg · Posted: Tue Sep 05, 2017 1:45 pm Post subject:

To follow up my own question..So something like Focusrite Scarlett series wouldn't do the job, enabling a Line input from say, the Avalon pre?

Bish · Posted: Tue Sep 05, 2017 5:03 pm Post subject:

There are two types of connection on the pre-amp/DACs that allow by-passing of the actual pre-amp. Withe my old Apogee Duet, you connected the mic via the usual phantom-powered XLR connection... and as the gain was reduced on the pre-amp, it literally got to a point where the pre-amps were physical by-passed with relays. I'm sure others work the same way if true by-pass is a feature. The problem with something like the Focusrite Scarlett (or similar) is that you can never actually switch the pre-amps out completely... the best you can achieve is a (sort of) null point where the pre-amp provides no actual gain, but the signal still passes through its circuitry, possibly/probably colouring the sound a little. The Audient iD22 has physical balanced TSR 1/4 send/return points where you can connect the external pre-amp (to the return), completely by-passing the internal pre-amp. I find it to be a versatile unit... it even has digital (optical) ADAT/SPDiF i/o.

From the iD22 product page:
The insert return also gives you direct access to the analogue to digital converters - providing the cleanest signal path possible, making it great for print-backs or integrating outboard line level sources.

I don't want to sound like a salesman here (or just sing the praises of what I have)... there are other units that do the same I'm sure... but I have the iD22 and the Apogee Duet... so I can only speak to what I know Smile

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ballenberg · Posted: Tue Sep 05, 2017 7:00 pm Post subject:

Thanks Bish...that's important to know...It reminds me of when I first got a phone patch and had it routed less than optimally..so that I was recording my final recording my mic partly through my preamp, and partly from my phone..yuck!!

Sounds like the other units are fine if you want those preamps, but the id22 gives the right options. Thanks!

AlanTaylor · Posted: Wed Sep 06, 2017 6:53 am Post subject:

DenaliDave · Posted: Wed Sep 06, 2017 9:31 am Post subject:

Most (and I say most) of the audio interfaces have your signal running through the preamp circuitry, even if there is no phantom power energizing the built in preamp.

This can *potentially* color your sound, The only audio interface that I could find that actually can run a signal input through a physically separate pathway (and not through the tracing on the PCB inside the unit) was the Audient line of interfaces.

With the Audient you don't use the XLR conenctions, but TRS connections for the insert/return loop that doesn't physically touch or have anything to do with the interface's preamp circuitry. That's what I run my Avalon through.

That said, I do have an original Firewire Apogee Duet, and there's been a lot of debate/discussion over whether the preamp bypass is a "true" bypass or just simply an emulated bypass.

Either way, after extensive research into the A/D converter chip itself used by Audient, it's a cousin/brother of the same Texas Instruments A/D chip used in the extremely high-end Antelope stand-alone A/D converters. The differences are minute and basically come down to power consumption.

For perspective, the Antelope Pure 2 ($2,295) uses the PCM-4222.

Besides power consumption the only other difference is the 4222 can do DSP, whereas the 4220 that the Audient uses maxes out at 192k.

Then again, most of us don't need a world clock (that's part of the Antelope Pure 2) -- and the all of the other I/O toslink stuff it offers.

So, for the price (and I've spec'ed out standalone A/D converters) you really can't get much better. You might be able to find someone who's willing to make a custom DIY type of stand alone converter if your setup requires it though.
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Bish · Posted: Wed Sep 06, 2017 10:20 am Post subject:

That's some interesting information Dave. I can confirm that the original Apogee Duet (firewire) does actually use physical switching inside the unit to bypass the pre-amps. By using the software interface, you can switch the signal path. Some years ago, I actually spoke to Apogee about this. I have no idea what the new Duet units do.

I have a Focusrite Scarlett 2i2 laying around, and I'd love to get in there with a meter and a scope to see if I can separate the pre-amps from the a/d converter. I probably won't be able to... but it may be a fun exercise. I'll strip it down and see what the circuit board looks like. Yes... I have too much time on my hands.
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dwpthe3rd · Posted: Wed Sep 06, 2017 1:40 pm Post subject:

I use a MOTU Audio Express, purchased specifically for its separate line level inputs that bypass mic pre-amps; not really for anyone expecting "plug and play" as it does come with a setup protocol and learning curve. Once dialed in it's certainly pro quality. Works with Mac and Windows. $395 at Sweetwater.
https://www.sweetwater.com/store/detail/AudioExpress
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ballenberg · Posted: Wed Sep 06, 2017 6:33 pm Post subject:

Thanks guys, good stuff to know. Looks like the Motu would work but the manual is a bear!

Let me complicate this further: I'd like to feed two computers with the audio, sometimes separately, sometimes simultaneously. Currently running two separate sound cards...With say. the id22, is there a way to feed to both computers without a second id22 ?

dwpthe3rd · Posted: Wed Sep 06, 2017 9:17 pm Post subject:

If you need to send a mono, balanced line level signal, say VO, out of one channel of the ID22 channel to 2 different computers I'd look at one of these... certainly seems cost efficient and the Whirlwind name is solid in pro audio. There are probably many others - this is just the first one that popped up.
http://www.fullcompass.com/prod/050918-Whirlwind-SPLIT6
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ballenberg · Posted: Thu Sep 07, 2017 3:28 am Post subject:

Thanks Dave...I knew it wouldn't take long for me to get lost...

So, let me back up a step...When the id22 is being used solely as an A/D device, what's the input to the computer..is it USB? So to go to two computers, that would be what I'd need into both, right? Or am I not getting this r?

Bish · Posted: Thu Sep 07, 2017 4:23 am Post subject:

Connection to the computer with the iD22 is via USB. The vast majority of interfaces use USB... you may find some old Firewire units, or some new Lightning units... but for the most part, USB is ubiquitous. If you want to share a USB device between two computers it is possible. Simple switches can be used that will cleanly switch between the two computers. However, if you want to record on both computers simultaneously then you will need to look at another solution. A USB audio interface device cannot be used by two host computers at the same time. They are not networkable devices.
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