Topic: Edirol R-44 - 4 Channel Recorder (Part Tres)

[DSatz]

bugg100, since losing my microscopic vision in an unfortunate encounter with red kryptonite, I've had a hard time reading the R-44's meters accurately. This leads me to under-record channels 3 and 4 just to be on the safe side, and yeah, sometimes they come out lower in level than I'd like. Fortunately those aren't the main channels.

Channels 1 and 2 are nearly always going through my Grace V3 and into the R-44 via S/P-DIF, so I can use the V3's meters and level controls; no problem there.

--best regards

[bugg100]

But geez, David I can check levels on my buddies V-3 from across the room....

But yeah, 24 bit headroom takes care of being well enough for me as well.

Joe

[kirk97132]

I've found that after running the R-44 for almost a year now, you get a real good feel for setting your levels.  The metering does leave a little to be desired. In my old age with eyesight not a sharp as it was i tend to err on the side of caution.  And while not a real technical term, the attack time of the meters seems good and the accuracy solid enough to allow em a level of comfort in pushing the levels up a tad.  For me and what I record I look to see the meters hitting between the 20 and 12 marks on the scale.  it then seems that I never have peaks that clip.  Like a lot of you I do run a pre in front of my mics .  And as a rule I always start with the the outer(clicky) [analog] sensitivity knob rotated completely counterclockwise and only add gain with that knob if I cannot add enough with the inner(smooth) [digital] level knob.  The most common situation where I find myself have to add gain with the outer(clicky) [analog] sensitivity knob is when I take a straight rca line level signal from a mixer.  Kirk

[danlynch]

I'm extremely pleased that "clicky" and "smooth" have taken off as the new popular monikers. 

That being said, I have yet to run my mics with the Mini-Me in front with this unit.  Its certainly something that I will eventually do.  At this point, I'm just becoming more comfortable with the R-44 and carrying the extra equipment in the field has been a disincentive.   Plus I have to rationalize/justify having spent an extra $100-150 on the Oade mod unit by convincing myself I don't need the pre.  This leads to the question, do I really need the mini-me with an Oade mod version of the R-44?

[edtyre]

I have an Oade mod version and it sounds pretty good without
a pre, stills sounds better with my V3 in front.

Also on the gain... Doug told me (and its in the team thread)
keep the small knob (smooth) all the way to the right before adding any gain
with the outer (clicky) knob.

[bugg100]

I really have a hard time with the logic of Oade's advice unless he totally rebuilt the circuit with his mod.....

On a stock box, far left on the inner(smooth) knob would be +12dB boost of the incoming signal from the analog section.

That would be the analog section you paid money for him "MOD".  Is the analog pre that bad that it needs that much  "normalization"?

[skotdee]

Also on the gain... Doug told me (and its in the team thread)
keep the small knob (smooth) all the way to the right before adding any gain
with the outer (clicky) knob.

Interesting. Thats in direct contrast to how others here, and the manual, suggest adjusting gain. So it would be better to have all digital gain, and no analog? Does anyone know the difference, or why Doug would advise this method?

[edtyre]

Here's his exact quote

from Doug Oade:

"Use as little gain as possible from the outer knob, this is the one that adjust the dB setting in the LCD display.  Increase the gain with the outer knob only if you cannot get enough gain with the inner knob set to maximum"

I don't know what Doug mods, but i have one of his units and it's been fantastic so far.
I'll admit to running digi in most of the time with my main pair, but every time i have run
either soundboard or a second pair of mics, i have followed his recommendation for gain
settings and it's worked fine for me.

[bugg100]

Well, what works is good. But the 2 knob issue is confusing at best to new owners so our needs are best served as community to not add to this.

Could Doug be confused about this in reference to the above quote?

[cybergaloot]

I think some people have problems envisioning what is inner and outer with the knobs because they are picturing the knobs from looking down at the unit from above, not from looking at the knobs from the end (like a target). From what I read of Doug Oade's comments, it seems to me like he is looking from the top.

[bugg100]

"Use as little gain as possible from the outer knob, this is the one that adjust the dB setting in the LCD display."

Seems to be without question as the smooth knob does nothing on the lcd....

[Ozpeter]

The smooth knob is clearly digital gain, as I've said before - at its zero point you get digital silence.  If you add (or subtract) digital gain during recording, you are irrevocably altering the bits after AD conversion for no useful purpose - unless you have no means or intent to do postproduction.  If Mr Oade's strange advice is intended to encourage people to use low gain on the mic preamp, then you can still do that if you want, but don't then add digital gain during recording to compensate - you can do it later in your DAW when you know precisely how much digital gain to apply.  During the recording, you're taking a guess and you might end up with digital clipping, or you might add not enough digital gain during recording and need to add more later, which strikes me as undesirable at least in theory.

Furthermore, recording at different preamp (clicky knob) levels has implications for the noise floor at each level.  See the earlier thread about this for details.  The Oade mods may change the noise floor figure for each setting compared to stock units however.

[skotdee]

I emailed Doug earlier today and asked him to elaborate a little on this matter, here's his reply:

Hi Scott, my understanding is that gain adjustment is a PGA and not  digital manipulation of the signal data post conversion, that would be exactly the same as boosting levels with a DAW. The reason to use as little front end gain as possible is to both reduce the odds of overload and reduce the amount of hiss. Think of the front end gain adjustment as an input trim control on a sound recording console. The key point is the analog signal does not pass thru the rotary controls, they are digitally controlled but of an analog signal path. I know this for a fact for the front end as I traced out that circuit and know how it works. This is well done as it avoids any digital level changes in the critical preamp section.  I am very impressed with the R44, Edirol did a very good job with it, gain control is just one example of their superior engineering.  I looked at the block diagram and now understand why everyone is so confused, that diagram seems in error. I have never seen a limiter, for example, placed after signal level adjustment. One typically uses a limiter before a circuit that can overload, not after. However, Edirol does not release service manuals and I have not traced out that part of the circuit. I do suggest you do a  few test and let your ears deice what works best for you.
I hope this helps...Doug

[Gutbucket]

^^^
skotdee just posted a similar angle while I was typing this:

The smooth knob is clearly digital gain, as I've said before - at its zero point you get digital silence.

Maybe, probably, but your conclusion is not necessarily correct.  Just look at the R-09.  '0' input level mutes the input, yet no one would argue that the R-09's input adjustment isn't controlling the analog input stage.  The R-09 has a digital adjustment of analog input gain.  So does the R-44, except there are two input range controls and it is uncertain how the gain stages work which those pots control.  Both knobs adjust digital control signals, which can be programed to mute the input or set it at various gain ratios.  Those digital control signals can be used to adjust either analog or digital gain changes and that's where the mystery lies.

I agree that both the wording of the manual and the simplified circuit diagram in the appendix seem to indicate that the 'smooth' knob on the R-44 is doing a digital gain adjustment after the ADC.  Yet also I've been told by circuit savvy people poking around inside this machine (who seemed quite impressed with Edirol's engineering, FWIW) that the R-44 uses a PGA or programmable gain amplifier and that the simplified diagram might be somewhat misleading.  I assume the R-09 uses a PGA design too.  I'm not certain what all the implications of using a PGA are other than eliminating sending audio signal though the gain potentiometers by instead adjusting a control signal to the PGA, eliminating the problems of noisy pot wiper scratch, pot linearity and matching, and analog circuit routing issues. I'd think such a design would make for easy/clean/inexpensive push button or rotary user controls and simplifies the analog circuit by keeping it all in the chip and on the board. But I don't know enough about that stuff to really say.

The short and long of it is that I'm back to accepting that I have no idea what is really going on inside this thing.  I've reverted to a practical view informed by usage alone.  In the real world I've run the R-44 with the smooth knob at both 12:00 and at full clockwise and have made good sounding, undistorted, noise-free recordings both ways. Yet I can also create the condition where I can cause the input stage to clip (channel number blinks) before the meters indicate full scale if the center knobs are not at 12:00.  Because of that I've tended to set the center knobs at 12:00 and adjust the clicky knobs for sufficient gain.  That makes the metering accurate at least which is vitally important, and I haven't noticed a significant difference in noise.  Regardless, I try to keep my eye open for blinking.  I was mildly shocked to find that the R-44 doesn't have an obvious flashing red clip light like the R-09 when I first received it.

[Gutbucket]

I'm going to experiment a bit to try and illuminate myself, but one thought occurred to me to detect where in the circuit the smooth level control is actually working.

We know the limiter is after the analog input stage.  IF the limiter is after the ADC but before the level control (smooth knob) as indicated in the block diagram, then we should be able to set the device so that we can hear the squashing effect of the limiter, then adjust the smooth knob and see how that change modifies the effect of the limiter. 

If the signal level changes but the limiter squash is the same, then the smooth level control is after the limiter.  If adjusting the smooth level control causes the limiter to engage more or less strongly, then it is before the limiter.

The test won't tell us if the limiter is really before or after the ADC though, so I'm not sure that really helps.  If we know the limiter is digitally implemented then it does.