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.
Date: Wed, 28 Jul 2004 21:40:05 -0400
Subject: Fw: V3 gain question
The other day I asked Jamie Krapohl of Grace Design & Lunatec some
regarding the gain and trim on the V3. The objective of my questions
achieving the cleanest sound and a lot of my focus was on whether the
acted as an attenuator or additive. I was pleased to learn that the
stage is additive and that he was happy to have me share his reply. I
it informative and useful.
----- Original Message -----
From: "Jamie Krapohl" <firstname.lastname@example.org
Sent: Tuesday, July 27, 2004 1:03 PM
> Hi Eric-
> Thanks for your email and the questions you have regarding your
> 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
> 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
> the following formula: 20*log (gain). In this case 20*log(2)=6dB.
> 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
> stepped gain switch. This stage provides +10dB to +60dB of gain in
> steps. The [second] stage is the 'TRIM' control. This is a bit
> as to whether or not this is simply an attenuator or a second gain
> The answer is that it is indeed a second gain stage. The TRIM
> 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
> 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
> 100. Gain settings of +60dB or +70dB correspond to gain factors of
> 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
> 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
> gain is not enough. Using the TRIM control in this application to
> provide additional gain is obvious. These scenarios are few unless
> do a lot of low-level source recording or have low output mics (or
> The next use of the TRIM control is in instances when you want to
> 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
> 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
> in applications where you are not strictly requiring over +60dB of
> (or the forthcoming situation) I'd recommend using the lowest TRIM
> necessary. When adding gain in the second stage you are also
> any undesirable noise from the first gain stage. This is obviously
> minimal with the V3, but none the less, good practice.
> The final setup in which the TRIM control is utilized in an
> where you wish to ride the gain while recording. There are many
> scenarios in which this could be used. Here are a couple of
> 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
> positioned in different settings. For vocals, you may wish to keep
> 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
> setting and increasing the TRIM to get the appropriate record level.
> say you get to +5dB on the TRIM, you might want to step up the main
> +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