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Old 24th November 2009, 16:34   #16
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Originally Posted by gunner fan View Post
C) Precision Power A600/4
600 watt 4-Channel Amplifier
RMS Power Rating:[list][*]4 ohms: 50 watts x 4 chan.[*]2 ohms: 80 watts x 4 chan.
if PPI is still the same company it was in the 80s take the PPI amp.
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Old 24th November 2009, 17:09   #17
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if PPI is still the same company it was in the 80s take the PPI amp.
navinji - I was born in the 80s. Anyways - PPI seems to be the same company - positioing themselves as audiophile manufactures but probably have gone down the lane of obscurity.

quick help - how does one compare various amps - looking at
1) RMS - higher the better
2) Signal-to-noise factor - higher the better?
3) THD at rated RMS - ? (dunno what it means)
4) Channel Spearation - ? (dunno what it means)
4) Fuse rating - higher better?

Also for some amps the RMS at 2 ohms is double of RMS at 4 ohms but for others it is less than double. What is the norm? Questions from a noobie
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Old 25th November 2009, 12:31   #18
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Nope I first consider sound quality. Other factors: weight (usually means well built power supply), heat sink (another area where manufacturers skimp), then I look at the comparitive watt ratings - that means how does the wattage change from their 4ohm values to their 2 ohm values that gives me an idea of the electrical stiffening in their power supply.
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Old 25th November 2009, 16:41   #19
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then I look at the comparitive watt ratings - that means how does the wattage change from their 4ohm values to their 2 ohm values that gives me an idea of the electrical stiffening in their power supply.
Navin - how does this make a difference? Please enlighten...
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Old 25th November 2009, 18:17   #20
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Nope I first consider sound quality. Other factors: weight (usually means well built power supply), heat sink (another area where manufacturers skimp), then I look at the comparitive watt ratings - that means how does the wattage change from their 4ohm values to their 2 ohm values that gives me an idea of the electrical stiffening in their power supply.
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Originally Posted by sonirohit View Post
Navin - how does this make a difference? Please enlighten...
@ Navin Ji - should the wattage be double at 2 ohm than what is at 4 ohm - example if it is 85W*4 ch @ 4 ohms, then it should be 170W*4 ch @ 2 ohms?

@ Rohit - i guess this is what you were also asking around?
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Old 25th November 2009, 21:00   #21
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Originally Posted by gunner fan View Post
@ Navin Ji - should the wattage be double at 2 ohm than what is at 4 ohm - example if it is 85W*4 ch @ 4 ohms, then it should be 170W*4 ch @ 2 ohms?

@ Rohit - i guess this is what you were also asking around?
Not necessarily. THere are Amps that put out 500W RMS @ 4ohms and 600 W RMS @ 2 ohms load too.

Another Classic example is the Alpine PDX series. They give out the same output at 4 Ohms and 2 Ohms.

Generally speaking the efficiency of the Amplifer is higer at 4 Ohm than 2 Ohms or Less. By Efficiency, we mean better thermal handling at particular voltage level. Of course you get more power too when connected at lesser impedences.

I would consider primarily 4 factors when deciding an Amp;
1. Power Rating in RMS (Higher the better)
2. SNR (Higher the better)
3. THD (lesser the better)

and ofcourse
4. the Price

Last edited by Mi10 : 25th November 2009 at 21:01. Reason: typo
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Old 25th November 2009, 21:34   #22
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Not necessarily. THere are Amps that put out 500W RMS @ 4ohms and 600 W RMS @ 2 ohms load too.

Another Classic example is the Alpine PDX series. They give out the same output at 4 Ohms and 2 Ohms.

Generally speaking the efficiency of the Amplifer is higer at 4 Ohm than 2 Ohms or Less. By Efficiency, we mean better thermal handling at particular voltage level. Of course you get more power too when connected at lesser impedences.

I would consider primarily 4 factors when deciding an Amp;
1. Power Rating in RMS (Higher the better)
2. SNR (Higher the better)
3. THD (lesser the better)

and ofcourse
4. the Price
Which one would be a better amp -
Amp 1 - 500 W @ 4ohms, 1000 W @ 2ohms
Amp 2 - 500 W @ 4ohms, 800 W @ 2ohms

does this have a bearing on the SQ? Price of-course is a big factor - else everyone would be running genesis
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Old 25th November 2009, 22:35   #23
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Not necessarily. THere are Amps that put out 500W RMS @ 4ohms and 600 W RMS @ 2 ohms load too.
that is ok, but we're asking what is the difference, why is it and what is better? navinji was referring to something on electrical stiffening in the power supply
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Originally Posted by sonirohit View Post
Which one would be a better amp -
Amp 1 - 500 W @ 4ohms, 1000 W @ 2ohms
Amp 2 - 500 W @ 4ohms, 800 W @ 2ohms

does this have a bearing on the SQ?
and if i may add, everything else SNR, THD etc is the same for both the amps
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Old 25th November 2009, 23:42   #24
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then I look at the comparitive watt ratings - that means how does the wattage change from their 4ohm values to their 2 ohm values that gives me an idea of the electrical stiffening in their power supply.
Navin - could you please elaborate a bit.

I was looking to source a 4 channel from the US and there seem to be mixed reviews about PPI and Soundstream (My understanding is that they used to be SQ equipment back in the day)
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Old 26th November 2009, 00:08   #25
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and if i may add, everything else SNR, THD etc is the same for both the amps
That's where quality of internals come into the picture, along with damping factor, channek separation.
There are lot many amps that sell under under 150$ too which delivers same power as amps above 500$ but doesnt mean the quality of sounds will be the same. The internals play roles to such an extent that the power in real world may put out more power than the rated, which means some amps are under rated and some are over rated.
What exactly one is expecting from the amps is the question one should ask.

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Originally Posted by CrackedHead View Post
Navin - could you please elaborate a bit.

I was looking to source a 4 channel from the US and there seem to be mixed reviews about PPI and Soundstream (My understanding is that they used to be SQ equipment back in the day)
Where soundstream is concerned its the new Reference line that stands out of their entire range where SQ is truly concerned.

Last edited by bblost : 26th November 2009 at 14:46. Reason: back 2 back posts, please use multi quote instead.
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Old 26th November 2009, 00:35   #26
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That's where quality of internals come into the picture, along with damping factor, channek separation.
There are lot many amps that sell under under 150$ too which delivers same power as amps above 500$ but doesnt mean the quality of sounds will be the same. The internals play roles to such an extent that the power in real world may put out more power than the rated, which means some amps are under rated and some are over rated.
What exactly one is expecting from the amps is the question one should ask.
Hmm... Couple of questions remain unanswered
1) how come some amps have ratings of x W @ 4 ohms and 2x W @ 2 ohms and some other have lesser than 2x @ 2 ohms?
2) for my personal use - i intend to use the amp to initially drive the PPi 6.5 comps and pioneer 6*9s and later run the 6*9s from the HU and use the 2 channel to drive the Infinity 100.9. i am tending to lean towards the hifonics 6408. should have enough juice for my purpose.

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Originally Posted by Invinsible View Post
Where soundstream is concerned its the new Reference line that stands out of their entire range where SQ is truly concerned.
Also the soundstream tarantula range is supposed to be good (Soundstream TRA680.4).
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Old 26th November 2009, 02:39   #27
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Hmm... Couple of questions remain unanswered
1) how come some amps have ratings of x W @ 4 ohms and 2x W @ 2 ohms and some other have lesser than 2x @ 2 ohms?
2) for my personal use - i intend to use the amp to initially drive the PPi 6.5 comps and pioneer 6*9s and later run the 6*9s from the HU and use the 2 channel to drive the Infinity 100.9. i am tending to lean towards the hifonics 6408. should have enough juice for my purpose.



Also the soundstream tarantula range is supposed to be good (Soundstream TRA680.4).
Dont get confused by Amp ratings. Its manufacurers will and wish to determine the ratings of their Amp. To draw an analogy, 75 BHP@3000 RPM doesnt necessarily mean the engine will putout 150BHP@6000 RPM.

Similarly, there is absolutley no linear coorelation between Impedences (Ohm) and Continous Power (RMS). Few brands double (2X) the Power at 2 Ohms; few putout only 1.5X the Power at 2 Ohms, Etc...

If all other factors remaining constant, what i would choose between
"Amp 1 - 500 W @ 4ohms, 1000 W @ 2ohms
Amp 2 - 500 W @ 4ohms, 800 W @ 2ohms"

depends on the load i am going to drive. Eg:If my Sub is rated at 750 W RMS, then by hooking it to AMP 1 @ 2ohms, i am exposing it to damage. I'd better off driving it from my Amp 2

The SS Ref Series have great Specs and i think thats the one which is most respected after HRU sereis of all Sound Stream Amps

IMHO, Hifonics, MB Quart, etc..are ok for Subs but not for Compos. Something like SS Ref / Alpine PDX / Clarion / RF are more sweet-sounding

Last edited by Mi10 : 26th November 2009 at 02:40. Reason: typo
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Old 26th November 2009, 13:02   #28
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@ Navin Ji - should the wattage be double at 2 ohm than what is at 4 ohm - example if it is 85W*4 ch @ 4 ohms, then it should be 170W*4 ch @ 2 ohms?
It should but if often does not. There are a number of reasons for this but the 2 most common reasons are found in the power supply.

a. the power supply runs out of steam; this where checking the weight of the amp comes in. you see no single parameter is to be noted - one needs to look at all parameters and how the could be related to each other.

b. many GOOD amps have tightly regulated power supplies. These power supplies regulate (limit) the current delivery of the transistors to either protect them or to ensure that effects of 'sagging' (drop in SNR/Damping/etc..) is limited accross all power levels the amp is speced for.

c. Some output stages are sensitive to power supply fluctuations hence require tightly regualted power supplies.

Modern car amps are almost all powered using SMPS which are almost always tightly regulated. Hence to find car amps that double power when impedance is halved is rare today.

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Originally Posted by Mi10 View Post
IMHO, Hifonics, MB Quart, etc..are ok for Subs but not for Compos. Something like SS Ref / Alpine PDX / Clarion / RF are more sweet-sounding
Quite correct. The sound of the amp depends on the topology of it's circuit diagram (schematic). I am not famililiar with class-D and SMPS powered amps (most modern car amps are one of these) so I wont comment here but in my days audiophiles argued bitterly about SRPP vs LTP and various other topologies.

Last edited by navin : 26th November 2009 at 14:39.
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