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lt cdr data 28th February 2006 01:37 PM

tuning an amplifiers sound....
how do you change the sound in an amplifier, ie make it bassy, rythmic, or bright and sparkly sounding, ie what adjustable areas within reason can you tweak to change the way the amp sounds?

I am not talking about posh capacitor substitutions, but parameters.


Eva 28th February 2006 01:49 PM

Get a graphic equalizer :)

anatech 28th February 2006 01:56 PM

Hi Eva,
I didn't expect that from you! LOL You do have a sense of humour! ;)

lt cdr data,
Many things will affect the sound. Feedback ratio is a big one, but everything interacts to a degree. I wish there was a magic formula, but there isn't.


lumanauw 28th February 2006 02:13 PM


or bright and sparkly sounding,
This one is quite easy to experiment with. Introduce "slight" TIM. How? Remove the RE degeneration in differential pair. BUT you will have to adjust the stability caps (eg : miller cap)

lt cdr data 28th February 2006 02:28 PM

that' s exactly the sort of thing I am curious about, keep them coming!!

anatech 28th February 2006 02:31 PM

Hi lt cdr data,
Build some simple amps and play. That would be the best way to know what's going on, or get a feel for it.


beppe61 28th February 2006 02:33 PM


Originally posted by anatech
Many things will affect the sound. Feedback ratio is a big one,

Hello Chris,

which are the more evident differences in the sound between a very high feedback amp and a very low feedback amp ?
When you say feedback ratio do you mean close loop gain divided by open loop gain?
Which feedback ratio do you think is the optimum?



jcx 28th February 2006 02:40 PM

maybe you should think about what double blind testing does say (everyone jumps on what it can't tell you - proving the negative proposition that no one can hear x)

DBT testing shows that frequency response matching to within 0.1 dB is required to reduce the ability of a large number of listeners to discriminate with statistically significant reliability

some indicate that differences of 0.1 dB over more than 1 octave are sufficient clue to discriminate between systems

So >0.1 dB frequency response differences can be discriminated and contribute to "voicing", some amp reviews have commented on a particular designer’s "signature" x dB lift/rolloff/"presence peak", ect. shaping of amplifier response

Eva 28th February 2006 02:53 PM

It's not a joke. An equalizer is the right tool in order to obtain these effects. By moving a few sliders you can instantly make the music dark or brigth, punchy or bassy, forward or recessed, thin or thick, articulate or muddy...

You wont't be able to distinguish whatever little modification you do to an amplifier in a blind test, but you will easily distinguish equalisation.

I did live audio mixing for several years (vocals, guitars, wind), so I had to use equalization and compresion extensively. Some people may seem puzzled at what I say, but it's because they have never done serious listening while mixing and equalising. On the other hand, when you are in a venue mixing for a few hundred people you are forced to do *serious* listening and to create effects in order to make the mix "listenable" :D

anatech 28th February 2006 02:53 PM

Hi beppe,
Varying the feedback ratio changes many things at once. The ratio you choose depends on the open loop gain and how much closed loop gain you want. There are too many factors to come up with a simple statement.

I have found that as you increase the feedback, at some point the music loses it's "dynamics". This may or may no be the case with some amps. I haven't played with everything (hardly any compared to how many designs there are). There are designers that are far more experienced than I am who could better comment here.

The very best thing you could do is play with a design you are experienced with and vary tail currents, feedback and so many other things. Then once you have the amp stabilized again, have a listen.


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