Topic: Comments on Lunatec V3 gain from Grace Design Engineers

[BC]

Hey now-

I saw this on the laptop-tapers listserv, thought it might be useful reading for y'all.

I originally posted this on the pre's and processors section but thought it would make good archival info.

Take care,
Ben





Message: 3         
   Date: Wed, 28 Jul 2004 21:40:05 -0400
   From: ev
Subject: Fw: V3 gain question

The other day I asked Jamie Krapohl of Grace Design & Lunatec some
questions
regarding the gain and trim on the V3.  The objective of my questions
was
achieving the cleanest sound and a lot of my focus was on whether the
trim
acted as an attenuator or additive.  I was pleased to learn that the
trim
stage is additive and that he was happy to have me share his reply.  I
found
it informative and useful.
peace, further...
e

----- Original Message -----
From: "Jamie Krapohl" <jamie@gracedesign.com>
Sent: Tuesday, July 27, 2004 1:03 PM


> Hi Eric-
>
> Thanks for your email and the questions you have regarding your
Lunatec
V3.
>
> To begin with, a little background on 'gain'.  Gain, which is often
> measured in decibels (dB) is determined using the ratio of (output
> level)/(input level).  This ratio is absolute.  For example say the
> input signal has a level of 1(some unit here) and the output has a
level
> of 2(the same unit here).  The gain of this system is = (2)/(1) = 2.
> This is the actual gain factor, to get this value in dB you need to
use
> the following formula: 20*log (gain).  In this case 20*log(2)=6dB. 
The
> amplifier is providing 6dB of gain.
>
> With this knowledge, let's look at the V3.  Your preamp has two
> independent gain stages.  The first is controlled using the 10
position
> stepped gain switch.  This stage provides +10dB to +60dB of gain in
5dB
> steps.  The [second] stage is the 'TRIM' control.  This is a bit
confusing
> as to whether or not this is simply an attenuator or a second gain
stage.
> The answer is that it is indeed a second gain stage.  The TRIM
control
> allows between 0dB to +10dB of additional gain.  At any setting, the
> total gain of the V3 is equal to the channel's stepped gain setting
and
> TRIM control setting summed together.  Example: Gain +40dB, TRIM 0dB
->
> total gain +40dB or similarly Gain +35dB and TRIM +5dB -> total gain
> +40dB.  To refer back to our gain discussion earlier, +40dB of gain
> means the amplifier is multiplying the input signal by a gain factor
of
> 100.  Gain settings of +60dB or +70dB correspond to gain factors of
1000
> and 3100 respectively.  This gives you a little insight in to how
> important the preamp is in your signal chain!
>
> Now let me address your specific V3 performance questions.  The V3
> was designed to sound great regardless of gain settings.  With this
said,
there
> are a few things to consider.
>
> First, being continuously variable, the TRIM control offers several
> important features.  The most basic is for situations in which +60dB
of
> gain is not enough.  Using the TRIM control in this application to
> provide additional gain is obvious.  These scenarios are few unless
you
> do a lot of low-level source recording or have low output mics (or
both!).
>
> The next use of the TRIM control is in instances when you want to
dial
> in a specific gain that is not a multiple of 5dB.  For example if
> you wanted +43dB of gain to get the proper record level, you should
set
> the main gain setting to +40dB and the TRIM to +3dB.  You could
> obviously set the main gain to +35dB and the TRIM to +8dB.  This is
> 'less desirable' than the previous method.  When using second stage
gain
> in applications where you are not strictly requiring over +60dB of
gain
> (or the forthcoming situation) I'd recommend using the lowest TRIM
level
> necessary.  When adding gain in the second stage you are also
amplifying
> any undesirable noise from the first gain stage.  This is obviously
very
> minimal with the V3, but none the less, good practice.
>
> The final setup in which the TRIM control is utilized in an
application
> where you wish to ride the gain while recording.  There are many
> scenarios in which this could be used.  Here are a couple of
examples:
> When tracking vocals and the engineer wishes to smooth out the
> dynamics or when doing live recording and the band comes out 10dB SPL
> higher then the sound check!  Depending on the scenario, the TRIM may
be
> positioned in different settings.  For vocals, you may wish to keep
it
> at +5dB.  This gives you a range of +/-5dB for 'riding'.  In a live
> recording setup, you may wish to start at zero, with a nominal main
gain
> setting and increasing the TRIM to get the appropriate record level. 
If
> say you get to +5dB on the TRIM, you might want to step up the main
gain
> +5dB and back the TRIM down in between songs...
>
> I hope that this helps.  Thanks again for your email.  Please let me
> know if we can be of any further assistance.
>
> --
> Jamie Krapohl
> Assistant Design Engineer
> Grace Design & Lunatec LLC
> www.gracedesign.com