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Bass testing your favourite amps
This has been discussed many times before and bound to bring in many amps busters.
Why Do so many amps sound different in the bass area?
Okay allow me to qualify that, we are talking about quality amps, not so called multichannel wonder boxes and B grade consumer boat anchors.
I recall a post recently where it was reiterated the quality of the power supply capacitors was the key.
Oh really?
Maybe for some amps, but not for others.....switch mode amps and other new classes, and perhaps even the tried and proven class A room heaters.
Go here for a full explanation on power supply upgrades.
The job of filter capacitors is also well explained here.
http://www.tnt-audio.com/clinica/solid-state.html
They act like a water reservoir tank, you pour water in and take water out, to a point the bigger the tank the better the capacity to cope with demand.
Its also interesting to determine if the current demanded by the amplifier is constant or dynamic. As a rule, a constant load is a much tougher job for the filter capacitors because of the higher AC ripple current demanded.
However, the impact of capacitors dynamic performance is far less pronounced on an amplifier that draws a constant load, where the supply rails remain relatively stable and the design has good PSSR and CMRR.
With this in mind I recently did some comparisons with a conventional A/B amplifier, a class A SE amplifier and a 3rd class A amplifier having a true balanced output stage where the speaker output comes directly from the power transistors, not via the power supply.
The subjective appraisal for the conventional A/B amplifier provided tight punchy deep bass, however there was obvious bloom and colouration in the upper bass and midrange, it had large power reserves but lacked subtle nuances on bass instruments. (Damping greater than 1000 @ 20 hertz and output greater than 300 watts).
The class A SE amplifier exhibited an enlightened ambience in the bass and a feeling of space, individual instruments were clearly identified. There was a slight warmth in the tonality and good control of drum notes. (Damping factor 80, power output 100 watts).
The full balanced class A amplifier showed impressive dynamic contrasts, 3 dimensional ambience and tantalising excitement of micro dynamics. The bass tonality was neutral and delineation of instruments outstanding. (Damping factor 30, power output 100 watts).
Obviously I expect most will take this with a grain of salt and perhaps this belongs on another forum (although I would be preaching to the choir.) It would also appear damping factor is not the sole criteria for good bass performance.
But I think its fun to challenge your equipment and your ears occasionally.
By the way, the joke of this experiment was the reference speakers which were set up in near field operation. They are the much loved and unfortunately much bashed L100 Century.
The moral of the story is except nothing as normal, blame the operator first and your speakers last.
:eek:
Re: Bass testing your favourite amps
Quote:
Originally posted by Ian Mackenzie
I recall a post recently where it was reiterated the quality of the power supply capacitors was the key.
Oh really?
Hi all of you,
When something is said about power amplifiers, here I am!
All what will be said lies for AB amplifiers only.
From my very little experience since 25 years from now, I can say that what is important in the quality of an amplifier is the following:
The way the transformer is winded (we have several transformers able to deliver 2x300W, their power ability lies from 200Va to 1200VA; all listening test made around 25-30 watt, witch means that all transformers are powerful enough to drive the requested power).
The bridge is also important. Once we have selected the right components (transformer, capacitor, and others) changing the bridge will affect the output tonality.
Capacitors: From one brand to another, even with the best technical characteristics, you will have different tonality using one brand or another one (we finally went for several 10000MF100V capacitors instead of a big one – 47000MF63V from BC COMPONENT). One was nice but too shinny with a lack of mid bass … guess witch one?
It is well known that replacing a power supply made by a transformer, bridge and capacitors by a battery will dramatically enhance the sound quality of your amplifiers and pre amplifier.
Gain: the gain of the amplifier IS very important as we recently switched from 32 dB to 26 dB.
Signal to noise ratio: This is perhaps one of the most important number and greater it will be; more micro details will be heard, and by lowering the gain of the amplifier you will increase his signal to noise ratio.
CMRR: If you have a balanced input it is important having the better CMRR possible in conjunction with the signal to noise ration.
After that the choice of good resistors, capacitors (void all capacitors in the audio link) the way the PCB is designed will also play on the tonality of the amplifier.
Only A or AB amplifiers can play good music (other will just make noise, good enough for a football match in a stadium or for the next Olympic Games in Athens),
Distortion has no real signification,
Damping factor is just nuts,
Slew rate is not that important as the rising time (there is a house …. The animals),
This is just the beginning, for others climbing up the train just read a thread I opened month ago “Amplifiers are more significant than you may think”: http://audioheritage.csdco.com/vbull...=&threadid=347
Re: Bass testing your favourite amps
Ian,
Did you ever run across this - http://www.stereophile.com/amplificationreviews/674/
Also, what all did you see at Pass Labs?
Re: Bass testing your favourite amps
Quote:
Originally posted by PSS AUDIO
Damping factor is just nuts
Here we go again. :nutz:
I'm not quite sure how a ratio of two numbers can take on a psychological "disorder" but here's what George had to say about DF way back when - The Damping Factor Debate
It appears certain Marketing departments decided that damping factor was a "figure of merit" and we've been plagued with it as a selling point ever since.
Re: Re: Bass testing your favourite amps
We placed the same article on our website : http://www.pssaudio.com/english/art010.htm
I was perhaps misunderstood.
When I say nuts, it is between 17 and an infinite value, manufacturing an amplifier with less than 17, one must be ... very bad unless using an output transformer of poor quality!
It is not because an amplifier will "show" a DF of 100000000000000000000000 or even greater, that it will handle bass properly!
Neither if an amplifier has a DF of 20!