What is Gain Structure? - Page 3

29th March 2011, 10:57 AM
Pano diyAudio Moderator Join Date: Oct 2004 Location: SW Florida	What is Gain Structure? Gain structure (AKA Gain Staging) is a concept that gets talked about a lot in pro audio, but most home audio folks have never heard of it. Understanding gain structure can help you get the cleanest signal possible out of your system and avoid some nasty things. Things like noise and clipping,... Click here to read the entire article Last edited by Variac; 1st April 2011 at 11:34 PM.

15th April 2011

AUDIODH

diyAudio Member

Quote:

My rule of thumb is to keep the signal about 6dB below clipping. That can often be impossible or impractical, but it's a goal to shoot for. You don't want to go above that level - unless you're looking to add distortion. Dropping too far below that means you'll pick up noise.

That's it in a nutshell.
Pano,
well said!
The 6 dB headroom is a very good margin to shoot for. If your a live player and/or sound man....that is a big part of your job.
In home theater/stereo systems, that is taken care of in the mastering process. Often times to the point of destroying dynamic range....can you say 6dB overall headroom!
Pano, I see we completely agree on this subject and I hope it helps all the DIY members when gain staging their system.

15th April 2011

AndrewT

diyAudio Member

Going back to the first Gain diagram.
If the X4 gain stage were switchable to bypass (X1) or to +6dB (X2) then the system as it was could be adjusted to suit virtually all sources

regards Andrew T.
Sent from my desktop computer using a keyboard

15th April 2011

AUDIODH

diyAudio Member

Quote:

Going back to the first Gain diagram.
If the X4 gain stage were switchable to bypass (X1) or to +6dB (X2) then the system as it was could be adjusted to suit virtually all sources

Hi Andrew,
that is a true statement.
In an ideal world for us tweaks, a continuously variable gain pot is optimum, preferably with an signal/clip indicator for optimum level in the associated device. However, in many systems, that just means more $ to the end user. There is a good argument for a matched system where that engineering has been done up front and isn't a concern.
I sometimes run through as many as ten devices in the signal chain through both analog and digital paths, I have to relay on indicators and my ears to optimize the gain staging.
-Dave

15th April 2011

adason

diyAudio Member

Talking about the gain strcture and the levels accross the signal chain...I miss those days where almost any device had its own VU meter, so you knew where is your signal. Reel-to-reels and cassette decks all had nice analog or digital meters, to keep the signal as far from the noise, yet safe from overload...even good pre-amps had the signal meters, not to mention power amps. Its a pitty that those nice fluorescent VU meters dissapeard, they were so much fun to watch, especially the fast ones. If you see complete systems these days, there are barely any VU meters!

15th April 2011

adason

diyAudio Member

see what I mean? nothing moving to the signal, no meters...
https://www.diyaudio.com/forums/every...-diy-rack.html

15th April 2011

AUDIODH

diyAudio Member

Adason,
yes I use to have a visual on the old McIntosh system with those beautiful blue meters and lights while listening to some Frazier Texas Bull Horn loudspeakers. That system rocked! It was in 1970 when I was young enough to truly sit and listen to really good music!
Your system looks nice. I could see you had Bryston power, and from the looks of it, Bryston preamps too! They design great stuff and the whole gain stage blog is a nonissue with quality matched gear as that you have! I'm sure you don't experience noise, clipping, etc with that system.
-Dave

15th April 2011

danielwritesbac

diyAudio Member

It would be interesting indeed to see some other examples of amplifiers that have gain strictly in proportion to output potential. The majority of examples like that may turn out to be high power models (prosound scale).

What are some of the more modest (home scale) exceptions that actually work well?

Are there more good examples of high current output buffers (purpose made for driving speakers) to compare and read up on for reference?

15th April 2011

Conrad Hoffman

diyAudio Member

Excellent article. I do have one small complaint- the term has always been and will continue to be "gain distribution".

I may be barking up the wrong tree, but at least I'm barking!

15th April 2011

Pano

diyAudio Moderator

Never heard that one, Conrad. In the pro audio I've always heard it called "gain structure."
Maybe it's regional. I'll look into it.

Daniel. Yes, if someone has some good examples from right here on diyAudio, that would be great.

16th April 2011

sandyK

diyAudio Member

Michael
What you are saying is highly desireable.
However, until STBs and DTVs etc. use a gain stage to make up for the <-20dB level used with DTV broadcasts,
( and the level of the L and R from 5.1 Surround broadcasts is even lower)
then many of us are stuck with the need for additional gain, even though it will degrade other sources.
The DTV level via SPDIF is also low, and you really need to take extreme measures to avoid further S/N degradation,
otherwise low level ambience information is severely degraded.
Alex