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Old 9th January 2013, 02:11 PM   #1
KFIR72 is offline KFIR72  Sri Lanka
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Default Tri-amp help

Dear all

As a silent member since 2005 I have read many articles of this site, also my knowledge height was not even enough to start a thread at that time .Also when I had a problem I read old articles of many members . And I didn't have any special question to ask more than what others asked. I thank all the people who wrote in DIY AUDIO, Itís now a huge audio knowledge base in the net!

This time I really need your help, advice and recommendations to improve few things in my tri- amp system. Iíll ask one by one as all the things are connected together.

First thing I would like to ask.

I have two pioneer A400 class AB amplifiers as high and mid amplifiers of my tri amp project. To do some Improvement of the sound Iím thinking to build two pure class A amplifiers SC20W (silicon chip 20W) project, for the replacement of pioneer A400. Theoretically this class A amplifier has very low distortion. As I didnít listen to any class A amplifier up to now, Practically if I build SC 20W amplifier, can I hear any audible improvement more than pioneer A400? Can the human ears feel the difference between these amplifiers ? Did any body compare these two amplifiers? Please help.






Specifications of pioneer A400

DIN Continuous power output (both channels driven at 1 kHz)
85W + 85W into 4 Ohms. 1% THD
60W + 60W into 8 Ohms. 1% THD

Continuous power output (both channels driven at 20 Hz to 20kHz)
70W + 70W 4 Ohms, 0.05% THD
50W + 50W 8 Ohms, 0.03% THD

Dynamic power output (on EIA dynamic test signal)
135W/100W/70W into 2 Ohms /4 Ohms /8 Ohms

Total Harmonic Distortion
0.03% at 20Hz-20kHz , 50 W, 8 Ohms
0.05% at 20Hz-20kHz , 70 W, 4 Ohms

Frequency Response
5Hz-100 kHz + 0/- 3 dB (CD, Tuner, Aux, Tape)
20Hz-20 kHz +/- 0.3 dB (Phono MM)
20Hz-20 kHz +/- 0.5 dB (Phono MC)

Signal-to-Noise ratio (IHF short circuit, A network)
108 dB (CD, Tuner, Aux, Tape)
87 dB / 69 dB (Phono MM, 2.5 mV input, Phono MC, 0.2 mV input)

Signal-to-Noise ratio (DIN, continuous power/50 mW)
88 dB / 65 dB (CD, Tuner, Aux, Tape)
74 dB / 63 dB (Phono MM)

Input sensitivity/impedance
CD, Tuner, Aux, Tape: 150mV/ 50 kOhms
Phono (MM): 2.5mV/ 50 kOhms
Phono (MC): 0.2mV/ 100 kOhms

Power supply: 240V AC, 50/60 Hz
Power consumption: 520 Watts

Specifications of silicon chip 20w class a

Output power: 20W into 8 Ohms (pure class-A)

Frequency response: 0dB down at 20Hz; ~0.2dB down at 20kHz
Ė3dB @ 1.5Hz and 190kHz

Input sensitivity: 625mV RMS (for full power into 8 Ohms)

Input impedance: ~10k Ohms

Rated harmonic distortion: <0.002% from 20Hz to 20kHz, typically

0.0006%

Signal-to-noise ratio: Ė115dB unweighted, Ė118dB A-weighted (with
respect to 20W into 8 Ohms, 22Hz to 22kHz

Damping factor: 180 at 1kHz

Stability: unconditional
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Old 9th January 2013, 07:26 PM   #2
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well the question is tricky and cannot be answered if first some things are more clearly defined .

you cannot put next to each other a Pioneer A 400 and any other linear amplifier since the A400 is an integrated amplifier ...

Integrated amplifier of any make quality or cost will consume a quite serious amount of quality of sound in pots switches and generally "" functions "" that are required to have an integrated amplifier ...tone control for example ...even if there is a bypass switch those hardly ever manage to add some quality in the signal unless done with relays or any other innovative method.

The test could be quite better if you could actually isolate the main amplifier of the A400 and run tests between the two which still the A400 will be handicapped since wiring and supply is not made only for the main amplifier and inside the amp distribution of signal , power , and ground

As a very big generalization i could say that class A things like simple music like a violin a voice and a piano and perform the best on that while in house music ( the most mild you can imagine ) a faster amplifier not to busy with high bias will perform better to my opinion ..

So yes it will depend in a way to the music you listen and finally the test between the two amps the way you put it it will not be objective .... with this practice you will not have a proper evaluation ...

yet again one that makes a triamp is actually not a ""purist" in a triamp system which i presume is active there is a gozzilion of op amps in the signal path together with their wiring/ pcb/ power/ decoupling/ signal /ground and power distribution in addition ( in your case ) of a few more op amps inside the A 400 together with selector switches relays and all the rest mentioned above ... so do you still have """quality requests''''?

the basis to my understanding is to evaluate a system made more simple cause i sense that you are confusing your approach ( which is a fine tuning/ level setting/ mix matching of the 3 amps and their driven units ) with high quality of sound ....

set up a couple of normal 2 way near field monitors use low power hook up a nice source and your favorite music listen to it for a week or more learn your ways and details about this system then just replace the amp ...this will give you a more objective result

Kind regards
sakis
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Old 10th January 2013, 01:26 AM   #3
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Presumably, you will be using the class A amplifier only for the tweeters - at least that would be practical approach since the power level requirements will be suitably lower in most musical programme. Otherwise 20W is probably a limiting consideration for your system.

I don't think you need particularly high quality (ultra-low distortion) to enjoy excellent hi-fi stereo sound. Most of the benefit available will be just in the tri-amping and this depends more on good crossover design and construction. Focus your efforts there and DIY some basic, good amplifier design (since you need 6) such as P3a as a workhorse, just as this guy did for his own system
BiAmp (Bi-Amplification - Not Quite Magic, But Close) - Part 2
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Old 10th January 2013, 04:26 AM   #4
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Class A amps will show advantage if u hear the music at low levels.

Gajanan Phadte
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Old 10th January 2013, 10:43 AM   #5
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Default Dump the Pioneers

Hi, my advise is sell the pioneers off, good 20 years ago but not now. Use the money to get into some decent Class d amp. Using the venrable 2024 for the tweeters, my suggestion would be to use the Taxas TPA3116D2 for your mis and base, fantacstic sounding amp.
in my system I use a DBX 3 way active crossover (could be better, but OK at present)
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Old 10th January 2013, 10:54 AM   #6
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Most equiment have diffrent sonoc signatures ... Just listen I find it best to give each piece a long audition rather than a quick A/B Test. Then choose wich you like best . After all it is what you listen to ....
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Old 10th January 2013, 10:56 AM   #7
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class A versus class D ...marvelous quality conquest !!!
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Old 10th January 2013, 11:14 AM   #8
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Ask your self this .. is your system high quality or is it that you like the sound??????..
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Old 10th January 2013, 11:30 AM   #9
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The pioneer a400 were very good amps 20 years ago (award winning) and will still hold up very well with the best of today at their price range. All that is needed is some maintenance and upgrading of the capacitors. They are much better than class D amps and have none of their shortcomings except for power consumption.

Class A amps have an advantage at lower power which can easily be heard.
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Old 14th January 2013, 03:33 PM   #10
KFIR72 is offline KFIR72  Sri Lanka
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Dear all

Thank you for your valuable time and answers.

After few days in my repair bench ……….


First I started homemodder‘s practical point .Replaced all the electrolytic capacitors and some resistors that had changed their values. The result was excellent, now I can hear a crispy sharp sound from them as I heard them many years ago. Thank you again homemodder!!

(I have test A400s without the crossover, before and after upgrading).

With this result I think I don’t need to go for the class A amp now.


Dear Sakis and Ian Finch you are right, after A-400’s upgrade, I realized that there is a problem with my cross over tuning also, and I was confused there.

I have made Randy Slone’s 3way crossover project in his book , but I think I’m in the wrong frequency’s now. Please see the schematic of the same cross over that I found in the net.

3-Way Active Crossover with Linearity Phase eng



As a solution I’m going to borrow a professional crossover from my friend. After that I think I can get the picture how to divide the frequency’s according to my speakers as I do not have any data of those.

If you have better DIY crossover project than this,or any Idea, please help.

Thank you

Last edited by KFIR72; 14th January 2013 at 03:41 PM.
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