High Current Amplifier

[mpw]

kanwar,

smoe amps measure power output like Power Output (Stereo) : 75 Watts per channel at 1KHz into 8 Ohms

while others measure it like - Continuous o/p power at 8 ohm and 4 ohm ( stereo ) at rated THD > 80W 20 Hz to 20Khz both channels driven

In some way.. the power output also needs to be seen in view of the claimed freq response of the amp and the THD.

kindly comment in detail if possible.

regards,
mpw

 

[rishiguru]

After a long long time a truly informative thread from which we novices can learn. I understand those having science background will help, but kanwar describes in very easy language.

Triple thanks to kanwar.

 

[kanwar]

kanwar,

smoe amps measure power output like Power Output (Stereo) : 75 Watts per channel at 1KHz into 8 Ohms

while others measure it like - Continuous o/p power at 8 ohm and 4 ohm ( stereo ) at rated THD > 80W 20 Hz to 20Khz both channels driven

In some way.. the power output also needs to be seen in view of the claimed freq response of the amp and the THD.

kindly comment in detail if possible.

regards,
mpw

How the power is measured can tell you a lot about the amplifier itself.

The real way to measure the power is "Continuous Average" method across full power bandwidth, which comprises of NO NON SENSE burst modes but continuous sinewave signal sweep from 20hz to 20Khz and keeping THD under 0.1% unclipped at output loaded with resistance of defined load.

Nowadays Manufacturers use burst modes:-

European and American mass market uses EIA standard which uses 1khz sinewave for 33mS ontime + 66mS offtime repetitive burst this gives almost 1.6X more wattage rating than continuous average method.

Japanese manufacturers introduced EIAJ which uses 1khz single burst for 8mS ontime and its single pulse which gives much higher inflated rating because almost nill power supply capacitor voltage sag.


One must be clear about how the power specs are rated and what method is used to obtain these.

An amplifier rated at 100W continuous average 20-20khz is almost equal to 200W EIAJ 1khz 8mS burst testing mode rating.

Yet another way of rating is used by manufacturers of CHIP based amplifiers which says 100W at 10% THD which in reality is much less around 70-80W @ 1 %.

 

[rishiguru]

How the power is measured can tell you a lot about the amplifier itself.

I see some hi-end brands have an affinity not to disclose how the power output is calculated. Take for instance the Krell 400xi integrated.

In manual it is said,

POWER CONSUMPTION
Idle: 20 W
Max: 1,800 W

TRANSFORMER : 750 VA

OUTPUT VOLTAGE: Peak to peak 138 V

OUTPUT POWER : 8 Ohms 200 W, 4 Ohms 400 W

Weight : 14.1 kg

-----------------

Now if i compare the above specs to my yamaha dsp-z9 AV Amp manual it says:

Rated Power [20 Hz to 20 kHz, 0.015%THD, 8 ohms]: 170 watts X 2

Dynamic Power: 2-channels (Driven simultaneously):

8 ohms = 210 + 210 watts
6 ohms = 260 + 260 watts
4 ohms = 340 + 340 watts
2 ohms = 580 + 580 watts

POWER CONSUMPTION
Max: 1,300 W

Weight : 30 kg

------------------------------------

@ kanwar, my question is how can a 750 va trafo of the 400xi consume 1800 watts, when the 1200VA plus trafo of my DSP-Z9, 9.2 channel, 30 kilo AV amp consumes just 1300 watts max? It will great if you kindly elaborate.

 

[kanwar]

I see some hi-end brands have an affinity not to disclose how the power output is calculated. Take for instance the Krell 400xi integrated.

In manual it is said,

POWER CONSUMPTION
Idle: 20 W
Max: 1,800 W

TRANSFORMER : 750 VA

OUTPUT VOLTAGE: Peak to peak 138 V

OUTPUT POWER : 8 Ohms 200 W, 4 Ohms 400 W

Weight : 14.1 kg

-----------------

Now if i compare the above specs to my yamaha dsp-z9 AV Amp manual it says:

Rated Power [20 Hz to 20 kHz, 0.015%THD, 8 ohms]: 170 watts X 2

Dynamic Power: 2-channels (Driven simultaneously):

8 ohms = 210 + 210 watts
6 ohms = 260 + 260 watts
4 ohms = 340 + 340 watts
2 ohms = 580 + 580 watts

POWER CONSUMPTION
Max: 1,300 W

Weight : 30 kg

------------------------------------

@ kanwar, my question is how can a 750 va trafo of the 400xi consume 1800 watts, when the 1200VA plus trafo of my DSP-Z9, 9.2 channel, 30 kilo AV amp consumes just 1300 watts max? It will great if you kindly elaborate.

1800W max consumption of Krell could be the maximum peak power one can safely draw from the transformer, not the continuous.

But to draw that much peak, the load must be around 1 ohms which is very rare case.

 

[rishiguru]

1800W max consumption of Krell could be the maximum peak power one can safely draw from the transformer, not the continuous.

But to draw that much peak, the load must be around 1 ohms which is very rare case.

thanks kanwar.

It now seems to me that 400xi power output figures at 4 ohm load are single channel driven peak results which were taken at a certain frequency rather than both channels driven continuous outputs throughout the frequency range. THD levels was also not mentioned which puts a big question mark.

 

[moktan]

This amp is nothing but a chip based from Tripath which went bankrupt. T-amps are low on power, cheap to manufacture, easy to reproduce for mass market and have an aura of distinct sound characteristics because of its poor frequency and phase response due to pre-filter feedback[though people like it sometimes], you cannot correct for the non-linearity introduced by output filter unlike post filter feedback amps.

. So much hype has been created and marketing is done in such a way that the end user is made to believe that such chip would do a miracle, but the moment you test it in lab and later with ears, things become clear.

sir have you heard the Red Wine amp?

 

[kanwar]

sir have you heard the Red Wine amp?

Sir, I have listened to the Tripath chip which is inside Red Whine Audio amplifier along with other Tripath chips.

Euphonics introduced by Tripath chips are pleasant to such an extent that people love that against the quest for transparency.

 

[kanwar]

thanks kanwar.

It now seems to me that 400xi power output figures at 4 ohm load are single channel driven peak results which were taken at a certain frequency rather than both channels driven continuous outputs throughout the frequency range. THD levels was also not mentioned which puts a big question mark.

As per specs of 400xi, the peak to peak voltage is 138V, which translates to 48.7Vrms at no load conditions i.e. the rail voltage is around +/- 70VDC. The amplifier gives 400W@4ohms, which further states that there is considerable sag in rail voltage from no-load to loaded condition giving the loaded rail voltage around +/-57VDC. If this much is the rail sag, the ratings are taken with one channel only, not driving 2 channels continuously, owing to fact that transformer rating is just 750VA

 

[rishiguru]

As per specs of 400xi, the peak to peak voltage is 138V, which translates to 48.7Vrms at no load conditions i.e. the rail voltage is around +/- 70VDC. The amplifier gives 400W@4ohms, which further states that there is considerable sag in rail voltage from no-load to loaded condition giving the loaded rail voltage around +/-57VDC. If this much is the rail sag, the ratings are taken with one channel only, not driving 2 channels continuously, owing to fact that transformer rating is just 750VA

It is amazing that manufacturers now-a-days fool us by publishing ludicrous power output and power consumption figures to lure customers with big numbers which can never be reached under normal conditions.

Pity that Krell is also following the same.

 

[Staxxx]

Dear Kanwar
Thank you for your very informative responses. I wish I understood more!
I have often looked at this page of technical data for my amp and wondered what it translated to in simple language. If you have a moment will you try please:

Link to information on the amp: www.behold.eu - English - Products - behold Classic - Power Amplifier - BPA768 - Technical Data - Tabulated Data

By the way, if some of the information looks strange regarding the digital output, the DACs are located in the power amp....hence....

Thank you

 

[rishiguru]

@ kanwar, with all the questions pouring in, it seems you have become the ONE to penetrate all the DARK MAGIC that wanders around HiFi world and reveal the TRUTH.

My request to you will be to be with us and take the pain & time to explain, coz we need guys like you in this forum who speaks technically and are not biased.

One more question from my side: When will be the "kanwar" made home amp available in public? Remotely possible in 2013?

 

[avidyarthy]

It is amazing that manufacturers now-a-days fool us by publishing ludicrous power output and power consumption figures to lure customers with big numbers which can never be reached under normal conditions.

Pity that Krell is also following the same.

My electronic technician had opened up the Krell recently to clean out the accumulated dust in some parts of it. As per him, the circuitry is totally different to what he is used to servicing till date. Well, shall ask him to elucidate on that and put in a brief here.

By the way, what is 'this' on power??? The higher the better??! News to me, eh! Me 'thought' it is always the cleaner variety of power that 'rates' the amps and not the virtual brute energy. I possess a moderate 'load' in the TL ... to drive, and can only manage to hit 75 on the volume out the the 151 possible. Yes, did, once or twice dare to go upto 100 ... result ... very very high undistorted, non-booming and crystal clear SQ. But, for what? Was it possible to hear at such high levels ... well, NO.

Power has nothing to do with the transparency of the sound. Yes, some match (on the power ratings) is definitely necessary ... but, the criteria of higher the power, the better it is ... is a verdict of a ...

 

[mpw]

one thing the power equation must take into account is the room size and the number of speaker drivers ( ie weather BS of FS ).

More power is better for the reason of room size and for better LF grip. The LF grip again relates to the material of the driver and its mass..

The higher the power.. the better is .. is something general but one must take other variables into consideration too.

Here we are taking more of Class AB rather than Class A where even 20W class A is huge..

rgds,
mpw

 

[rishiguru]

My electronic technician had opened up the Krell recently to clean out the accumulated dust in some parts of it. As per him, the circuitry is totally different to what he is used to servicing till date. Well, shall ask him to elucidate on that and put in a brief here.

By the way, what is 'this' on power??? The higher the better??! News to me, eh! Me 'thought' it is always the cleaner variety of power that 'rates' the amps and not the virtual brute energy. I possess a moderate 'load' in the TL ... to drive, and can only manage to hit 75 on the volume out the the 151 possible. Yes, did, once or twice dare to go upto 100 ... result ... very very high undistorted, non-booming and crystal clear SQ. But, for what? Was it possible to hear at such high levels ... well, NO.

Power has nothing to do with the transparency of the sound. Yes, some match (on the power ratings) is definitely necessary ... but, the criteria of higher the power, the better it is ... is a verdict of a ...

avid you got me completely wrong, nobody here is questioning krell's sound quality. I have heard them personally and they sound great.

 

[prem]

You need power for dynamic headroom, not to play loud. There are times that on a certain music passage for a few seconds, the amp will be required to deliver huge instantaneous power. This is where high powered amps come into play. Obviously goes without saying the quality of power needs to be good. Ideally i prefer amps which are Class A at lower levels and go into AB mode when the situation demands it.

 

[avidyarthy]

You need power for dynamic headroom, not to play loud. There are times that on a certain music passage for a few seconds, the amp will be required to deliver huge instantaneous power. This is where high powered amps come into play. Obviously goes without saying the quality of power needs to be good. Ideally i prefer amps which are Class A at lower levels and go into AB mode when the situation demands it.

ABSOLUTELY ..... this is what I noticed while pairing the TLs with my other amp ... a Norge 1000. The Norge was able to play the TLs well ..... but, not with the same dynamics .... not with the same attack ... and the SQ had a slight tendency of being of a 'laid back' variety.

 

[kanwar]

Dear Kanwar
Thank you for your very informative responses. I wish I understood more!
I have often looked at this page of technical data for my amp and wondered what it translated to in simple language. If you have a moment will you try please
Thank you

The tabulated data ,first time i have seen this in home audio amplifier, otherwise such type of specs are more in pro-audio amps.

Well here is the layman format of amplifier part specs.

Max output voltage is 48VRMS @ 4ohms or 134 V Peak to Peak and 41VRMS @ 2ohms or 116 V Peak to Peak

Output power per channel : 575W continuous average @ 3.9Ohm, almost 4 ohm impedance and 840W continuous average @ 2Ohm

Single cycle 30hz burst mode max power is : 1100W Peak @ 2 Ohm

Output stage impedance from DC to 100khz: 0.71mOhm to 36mOhms

Damping factor @ 20Hz and 100Hz : 11220 tested with 8 Ohm load

Intermodulation distortion : 0.001%

THD+Noise -1dB below clipping: 0.003%

Signal to noise Ratio : 98dB

Mains Hum rejection @50hz is -130dBc and @100hz is -123dBc[which is almost negligible contamination]

DC Offset voltage at the output: +/- 200 mV max.

Input stage coupling: pure direct DC coupling, no capacitors in audio path.

Frequency Response deviation from 0dB scale from DC-20kHz is : +/- 0.025dB


I hope this helps........

 

[kanwar]

You need power for dynamic headroom, not to play loud. There are times that on a certain music passage for a few seconds, the amp will be required to deliver huge instantaneous power. This is where high powered amps come into play.

Higher the power, lesser the chances of the amplifier to hit clipping when extended low frequency music signals are being fed to loudspeakers. One more thing high power amplifiers operate at high voltage rails therefore the slewrate is very high giving very fast attack and decay times which further makes the transient response very much lively.

 

[Gerry_the_Merry]

Higher the power, lesser the chances of the amplifier to hit clipping when extended low frequency music signals are being fed to loudspeakers. One more thing high power amplifiers operate at high voltage rails therefore the slewrate is very high giving very fast attack and decay times which further makes the transient response very much lively.

Great thread. The following article seems to say in quite some detail the same thing - http://www.hificritic.com/downloads/Archive_A7.pdf