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Old 29th March 2011, 10:57 AM  
Pano is offline Pano  United States
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Location: Milliways
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Default 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,...

Last edited by Variac; 1st April 2011 at 11:34 PM.
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9th September 2012
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noddy55
diyAudio Member
Hi,

Mr.Stephan Großklaß (sgrossklass) and Mr.Michael Mardis (Pano),

Thank you very-very much for both of your contributions. Topics about "Gain Structure" and "Noise in Amplifiers", really are invaluable and encouraging articles for a novice at diyaudio. Specially, for those who are seeking for a good and reliable source of information to build better audio projects, and amplifiers or even just to improve the skills.

After reading your articles, I am now a lot more in a better position to design, execute and share my audio amplifier project, at diyaudio.
Also, i found the answers to lot of my questions which were floating inside the no gravity space region of my mind since my teenage or even my childhood.

We are keen and interested to wait for your future articles on Audio amplifiers, high current buffers, noise, speakers, crossover designs, filters, equalization techniques, op-amps, surround sound techniques and other such related articles mostly contributing towards the better sound quality or achieving a perfect diy audio systems. We would also like to see circuits in action (if possible and applicable) along with the theory part.

Thanks a lot to both of you.
10th September 2012
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Pano
diyAudio Moderator
You are very welcome.
8th December 2012
stevensoosai2527
diyAudio Member
Great article. Thank you.
8th December 2012
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nigelwright7557
diyAudio Member
Having earlier stages turned down with the amplifier on full will often cause a poor gain structure. Any noise/hum will be accentuated.
http://www.murtonpikesystems.co.uk PCBCAD50 pcb design software.
22nd December 2012
Telstar
diyAudio Member
Great article
I'm already of the opinion that a preamp is not needed with an all-digital setup with 2V+ line output.
I have a low gain amp (the F3) and more traditional ones, and I find about 10x gain to be all needed for home reproduction.

Now the issue is where to attenuate. Doing it at the power amp imput is NOT the ideal solution, the best option would be to adjust the gain of the amp itself (like Ayre and ASR do).
The ideal gain structure would be
2-2,5V from digital source -> input buffer -> adjustable VAS from like 0,1x to 20x (to provide for less efficient speakers) -> unity current gain.

The main difficulty to DIY this is from remote controlling the "volume" and from lack of published schematics.
If we loose a bit of signal purity (and SNR), a buffer type preamp with a pot in the middle can work almost as well and there are cheap and easy schematics availalbe, but it is still a waste of 3 stages and a pair of cables that all degrade the signal.
"The total harmonic distortion is not a measure of the degree of distastefulness to the listener and it is recommended that its use should be discontinued." D. Masa, 1938
22nd December 2012
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Pano
diyAudio Moderator
Glad you liked the article.

Yes, an adjustable VAS in the power amp might be the ideal approach, sonically. But as you point out, maybe not so practical or easy to find. For me, finding an amp that has a little more gain than I need, then attenuating it some at the input, is the most practical solution. With modern 2V sources it's gotten much easier.
22nd December 2012
Telstar
diyAudio Member
If the gain would be controllable with a single variable resistor (read linear pot), it would be much easier to diy... I want to do some research, with the many talented people roaming around, something may come out.

Things gets a lot more difficult with active multiamplified systems, where one needs to match amp and speaker gain, plus a desire to remotely control all the system at once (after level-matched). In a 2 way I was able to level-match with ears adjusting the pot of an integrated amp i have.

I'm mostly rumbling out loud.
Were you aware of a translation of your article on the italian webzine ReMusic?

Maximizing SNR is a very sensible topic for me, I'm reading the link posted here about an article on noise.
"The total harmonic distortion is not a measure of the degree of distastefulness to the listener and it is recommended that its use should be discontinued." D. Masa, 1938
22nd December 2012
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Pano
diyAudio Moderator
Quote:
Were you aware of a translation of your article on the italian webzine ReMusic?
Yes, they have permission from me and diyAudio. It's also in Chinese.

Let us know what you come up with for variable gain.
3rd February 2013
Dante Marone
diyAudio Member
This is an issue I'm about to have to deal with because I'm going tri-amp, and since I can't afford those tube-crossovers that Marchand(?) make I'm going to have to use DBX or Behringer pro model. Something like the ART CLEANBoxPro Stereo Balanced/Unbalanced Converter to adjust the unbalanced lower consumer level output of my preamp to better match the input, but my power amps are consumer w/o gain controls. Suggestions?
3rd February 2013
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SY
diyAudio Moderator
Replace the output amps of the Behringer with balanced RC filters (Jan Didden wrote a very clear article on how to do that). Pano prefers using output transformers to do the same job. Either way, the performance of the Behringer is improved and the levels are more suitable for consumer gear. As a bonus, you can take an spdif output directly from your digital source, run it into the Behringer's spdif/AES-EBU input, and bypass the ADCs completely.
"The way to deal with superstition is not to be polite to it, but to tackle it with all arms, and so rout it, cripple it, and make it forever infamous and ridiculous."- H. L. Mencken

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