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Author Topic: Lunatec V3 -- trim  (Read 2777 times)

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Offline 1Cylinder

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Lunatec V3 -- trim
« on: November 26, 2011, 07:22:35 AM »
I'm not too keen on the knobs on the front of the V3 that you use to adjust the trim. My hands are pretty small and I still have a tough time getting my fingers in there to turn the trim pots. I really liked the knobs on the V2 as they were larger, and much easier to access. I haven't done a side by side with the two preamps - I wonder if Grace used the smaller, round knobs for the V3 because there wasn't enough room for those used on the V2? 


Offline justink

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Re: Lunatec V3 -- trim
« Reply #1 on: November 26, 2011, 08:19:06 AM »
I'm not too keen on the knobs on the front of the V3 that you use to adjust the trim. My hands are pretty small and I still have a tough time getting my fingers in there to turn the trim pots. I really liked the knobs on the V2 as they were larger, and much easier to access. I haven't done a side by side with the two preamps - I wonder if Grace used the smaller, round knobs for the V3 because there wasn't enough room for those used on the V2?

the preamps are the same.  the V3 is just a V2 + A/D converter. 

the trim knobs aren't that bad for me.  i keep them at 12 o'clock and rarely move them at all.
Mics:
DPA 4028 (wide cards)
DPA 4023 (cards)
Earthworks TC25 (omnis) 

Pres and a/d's:
Oade ACM Grace Lunatec V3 (FOR SALE - Make Offer)
bm2p+ Edirol UA-5 (FOR SALE - Make Offer)

Recorders:
Oade CM Edirol R-44
Sony PCM‑M10

Offline it-goes-to-eleven

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Re: Lunatec V3 -- trim
« Reply #2 on: November 26, 2011, 09:28:57 AM »
the preamps are the same.  the V3 is just a V2 + A/D converter. 

Incorrect.

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Offline audBall

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Re: Lunatec V3 -- trim
« Reply #3 on: November 26, 2011, 09:29:38 AM »
Keep in mind that the V3's "trim" knobs are, in fact, a secondary gain stage.  The V2's trim knobs act as attenuators to the primary gain stage.

I think I got that right.   

-edited for clarity
« Last Edit: December 07, 2011, 11:42:27 AM by audBall »

Offline justink

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Re: Lunatec V3 -- trim
« Reply #4 on: November 26, 2011, 09:36:57 AM »
the preamps are the same.  the V3 is just a V2 + A/D converter. 

Incorrect.

no?
Mics:
DPA 4028 (wide cards)
DPA 4023 (cards)
Earthworks TC25 (omnis) 

Pres and a/d's:
Oade ACM Grace Lunatec V3 (FOR SALE - Make Offer)
bm2p+ Edirol UA-5 (FOR SALE - Make Offer)

Recorders:
Oade CM Edirol R-44
Sony PCM‑M10

Offline justink

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Re: Lunatec V3 -- trim
« Reply #5 on: November 26, 2011, 09:40:37 AM »
http://taperssection.com/index.php?topic=90060.0

This is how Mike Grace describes the differences between the V2 and V3.

"I guess the word "identical" may be a bit strong here.  When we first
started development of the V3 the mic preamp circuit was "identical"
to the V2 with one exception:  Most of the components in the V3 are
surface mount rather than through hole.  This was necessary to
accommodate the additional converter circuitry.  Components that are
not changed to surface mount include the gain control switch,
metalized film coupling capacitors, conductive plastic trim
potentiometers, HPF filter switches and XLR connectors.
  As we began evaluating prototypes it became clear that the V2 style
trim control would not work in the V3 for practical reasons.  (with
the trim attenuator one could be clipping the preamplifier badly and
it would not be visible on the meters)  However, when the trim on
the V3 is set to 0 the circuit "topology" of the V3 is identical to
the V2 with it's trim set to 0.   ....so... If you looked at a
schematic representation of the both preamplifiers with their
respective trim controls set at 0 the two circuits would be
identical. (with the possible exception of the INA163, which shares
the same architecture as the INA103 but may have subtle differences
in its internal circuit topology.  Burr-Brown does not publish
detailed schematics of these devices.)
   It is instructive that Doug has heard a distinct difference
between the V2 and V3 because it points out how important the very
small details in circuit design can be.  How can two preamplifiers
that have the same circuitry sound different?  Here are a few
possible factors that I can think of:

Surface mount resistors have no leads.  They are soldered directly to
the pcb.  Through hole resistor leads have inductance and stray
capacitance which surface mount parts don't have.

Use of surface mount parts permits a "tighter" pcb layout with
shorter traces.  Again, less inductance and stray capacitance.
This translates to better transient response and a better ability for
the circuit to resolve complex harmonic structures and high
frequency wave forms.
Use of surface mount devices also lets us use a more contiguous ultra
low inductance ground plane on the bottom side of the pcb.
The circuit ground is THE foundation of any audio circuit and the
more solid it is the more performance potential the circuit will
have, especially in the upper registers.

I guess I have billed the V3's preamp as "identical" to the V2 for a
couple of reasons.  One is to try to explain that we did not
compromise the preamplifier circuitry so that we could add an AD
converter in the same box.  The other is that I did not want all of
our V2 customers to think that they were sitting on obsolete
equipment when, IMHO, it is still a state of the art preamplifier.
As a manufacturer it is very tricky to introduce a product that
replaces an existing one.  Especially if you don't necessarily want
to participate in a "throw away" society where "out with the old and
in with the new" is what sustains our economy.

Sorry if this is a jumbled bunch of rambling.
-Michael"
Mics:
DPA 4028 (wide cards)
DPA 4023 (cards)
Earthworks TC25 (omnis) 

Pres and a/d's:
Oade ACM Grace Lunatec V3 (FOR SALE - Make Offer)
bm2p+ Edirol UA-5 (FOR SALE - Make Offer)

Recorders:
Oade CM Edirol R-44
Sony PCM‑M10

Offline 1Cylinder

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Re: Lunatec V3 -- trim
« Reply #6 on: November 26, 2011, 12:16:25 PM »

"Keep in mind that the V3's "trim" knobs are, in fact, a secondary gain stage.  The V2's trim knobs act as attenuators to the primary gain stage. I think I got that right."

>>>> Not sure if that's correct, but I believe that setting the trim knob on the V3 all the way to the left = no increase the gain.

Offline audBall

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Re: Lunatec V3 -- trim
« Reply #7 on: November 26, 2011, 07:53:31 PM »
I had to double-check.  Here's what the manuals say:

V2:  The trim control provides 10dB of continuously variable output attenuation. In the fully clockwise position the trim is at unity (no attenuation).

V3:  The trim control provides 10dB of continuously variable gain trim. In the fully counter-clockwise position the trim is at unity. In the fully clockwise position the trim control adds 10dB of additional gain.

Offline 1Cylinder

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Re: Lunatec V3 -- trim
« Reply #8 on: November 26, 2011, 08:29:31 PM »
Thanks audBall.

Offline it-goes-to-eleven

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Re: Lunatec V3 -- trim
« Reply #9 on: November 27, 2011, 08:55:37 AM »
http://taperssection.com/index.php?topic=90060.0

This is how Mike Grace describes the differences between the V2 and V3.

That's the blurbage I was thinking of.  Thanks for re-posting it.

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Offline Todd R

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Re: Lunatec V3 -- trim
« Reply #10 on: December 07, 2011, 11:17:45 AM »
I had to double-check.  Here's what the manuals say:

V2:  The trim control provides 10dB of continuously variable output attenuation. In the fully clockwise position the trim is at unity (no attenuation).

V3:  The trim control provides 10dB of continuously variable gain trim. In the fully counter-clockwise position the trim is at unity. In the fully clockwise position the trim control adds 10dB of additional gain.

The trim control on the V3 definitely adds gain, it isn't an attenuator.  But that doesn't mean the trim on the V3 adds an additional gain stage.  I haven't tried to trace the circuit so I don't know, but Mike Grace's comments leads me to believe the trim doesn't add a gain stage, and I wouldn't think that would be the design choice you'd like to make.

Keep in mind that op amps and instrumentation amps like those used in the V2/V3 have one pin that is a gain set pin:  the amount of resistance on that pin of the op amp sets the gain level of the amp.  The trim could could be (and I'm guessing is) part of the resistance circuit that is setting the gain, but it still would be the same gain stage -- you're just getting more gain out of that single gain stage.

Mics: Microtech Gefell m20/m21 (nbob/pfa actives), Line Audio CM3, Church CA-11 cards
Preamp:  none <sniff>
Recorders:  Sound Devices MixPre-6, Sony PCM-M10, Zoom H4nPro

Offline audBall

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Re: Lunatec V3 -- trim
« Reply #11 on: December 07, 2011, 11:46:41 AM »
Thanks for clarifying that Todd.  I thought I read about the "secondary gain" somewhere on here a long time ago, but your explanation makes better sense. 

Offline ethan

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Re: Lunatec V3 -- trim
« Reply #12 on: December 07, 2011, 11:51:47 AM »
http://taperssection.com/index.php?topic=90060.0

This is how Mike Grace describes the differences between the V2 and V3.

...

Sorry if this is a jumbled bunch of rambling.
-Michael"

:lol: well that settle that...wow
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