# What ever happened to the old school quality amps, no more today.



## wagonmaster (Jun 27, 2015)

Back in the heyday of car audio you would look at the specs on an amp. Most amps would double the output into a 2ohm load. 
25w at 4 ohm would be 50w at 2 ohm. 
What happened? In the search for an amp for my bike. I have visited a number of sites. I have yet to find any that doubles the output. I am not just talking about smaller motorcycle amps either. 
Grant it I know the variable of frequency to Ohms. 
Are the manufacturers just not caring anymore, putting profit over quality. Looks like I will be keeping my Old School PPIs. M, AM, and Art series. and work on getting more.

Tim


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## Viggen (May 2, 2011)

Those amps back in the day were A/B vs the class D that most companies produce today. Most do not have the room for multiple huge amplifiers. Like the old Adcom GFA 5475 that I had, yes it was rated at 75x4 and was claimed to double power as the ohms drop in half. But compare that 3ft long amp to say alpines PDX F6 which does 150 X 4 in probably 1/3 or 1/4th the area... Plus the increase in efficiency 

The class D platform some manufacturers state the same output from 1-4 ohms.... 

Those old cheater amps were also used so a car could enter the sub 100w class and have several times more power with the amps all running .25 or so ohms....

Especially in a motorcycle with its weak electrical system the new class D amps I would think would be a perfect fit. 80-90% efficiency, small chassis and light is what you want

the pheonix gold elite amps I used would pretty much double power.


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## seafish (Aug 1, 2012)

Probably NOT what you want to hear, but look into the amps offered by a company called Biketronix. There are several reviews here on diyma that you can search for. They are a powerful, cmpact and capable amp.


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## Niebur3 (Jul 11, 2008)

Sinfoni Tempo line doubles.....here are the Grave specs:

GRAVE | TEMPO SERIES
Specifications:
Power supply: 9-15Vcc
Standby current: <1.2A
Input sensivity: 0.4-8V
Input impedance: 48KΩ
Output power 4Ω @ 12/13.8V: 165/165Wx2
Output power 2Ω @ 12/13.8V: 295/315Wx2
Output power mono 4Ω @ 12/13.8V: 590/635Wx1
Output power mono 2Ω @ 12/13.8V: 775/925Wx1
Frequency response: ±1dB 10Hz-30KHz
Signal/Noise ratio: <90dB
Dimensions (WxHxD): 434x40x187mm
Weight: 3.8Kg

Arc Audio SE also doubles.....
ARC 2300se
2 Channels @ 4 ohms	330 Watts
2 Channels @ 2 ohms	660 Watts
1 Channel @ 4 ohms (bridged)	1300 Watts
1 Channel @ 2 ohms (bridged)	1300 Watts
Frequency Response	4Hz - 100kHz
Crossover Range	30Hz - 500Hz
Crossover Range X10	300Hz - 5500kHz
Bass Boost	0 - 15dB @ 20Hz - 80Hz
S/N Ratio	90 dB (RCA In)
Input Sensitivity (Low)	.3V - 4V
Input Sensitivity (Bal)	.4V - 8V
Max current draw	222A @ 1800 Watts 20% THD
Idle Current	1.14 Amp
Fuse	3 x 40 Amp
Dimensions	19.5"(L) x 8.0" (W) x 2.5"(H)

Just to name a couple.


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## strohw (Jan 27, 2016)

That's because they aren't doubling their power. They're rating the 4ohm stereo load low. Take a look at any of the old school dyno videos for any old school amp you have in mind. PPI also used regulated power supplies in the amps you listed rated at 12v input. Amps make just as much power as they did back then.


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## SkizeR (Apr 19, 2011)

strohw said:


> That's because they're aren't doubling their power. They're rating the 4ohm stereo load low. Take a look at any of the old school dyno videos for any old school amp you have in mind. PPI also used regulated power supplies in the amps you listed rated at 12v input. Amps make just as much power as they did back then.


beat me to it


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## Onyx1136 (Mar 15, 2009)

A lot of those older amps didn't double their power at 2 ohms, either. Just because the spec sheet said it, doesn't mean the amp actually did it. Companies would put whatever power rating they wanted on a spec sheet to sell product. The CEA2006 specification process was specifically developed because of the games that manufacturers were playing with power rating specs. I'm not defending the CEA specs or their methodology, just explaining how and why they came about.


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## teldzc1 (Oct 9, 2009)

Back in the day people ran passive crossovers and multiple speakers on amp channels. Now most high end builds use dsp and each speaker gets their own channel. Max power and low distortion into 4 ohms is more desirable for anything besides sub amps.


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## t3sn4f2 (Jan 3, 2007)

I don't understand how car audio amps can double in power into 2 ohms yet home audio amps begin to fall off below 4 ohms. And they, unlike car audio, play into full-range passive components with huge impedance dips and phase swings. No matter the price, take these Mark Levingson $50,000 powerhouses. 










Mark Levinson No.53 Reference monoblock power amplifier Measurements | Stereophile.com

"Figs. 4, 5, and 6 show how the THD+N percentage in the No.53's output varied with power into 8, 4, and 2 ohms, respectively. Below 10W into each load, the measurement is dominated by noise, indicated by the upward slope of the traces with decreasing power. The actual distortion starts to rise above the noise at a few tens of watts but is extremely low in level: at or below 0.005% into the higher impedances. Defining "clipping" as the power at which the amplifier was producing 1% of THD+N, the No.53 readily exceeds its specified output power, *clipping at 686W into 8 ohms (28.4dBW), 1080W into 4 ohms (27.3dBW), and 1500W into 2 ohms (25.8dBW)*. (Note that I don't hold the wall voltage constant for these tests.)"


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## ca90ss (Jul 2, 2005)

t3sn4f2 said:


> I don't understand how car audio amps can double in power into 2 ohms


They don't. Some come close and some claim they do but they don't.


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## Lunchietey (Oct 30, 2014)

ca90ss said:


> They don't. Some come close and some claim they do but they don't.



Exactly this, some of the 'doubled output' was also measured at a different frequency range(or just 1khz) and a different level of THD%. 95% of the time it was just to make you THINK the power supply was more robust etc. Many amp manufacturers(including big names) would each have their own 'special' way of measuring their amps. Rockford Fosgate was a prime example with their 'powercube' spec sheets and own 'burst' style measurement.

Also don't use maximum output as a testament to voltage regulation. A given amp may absolutely double its output at a halved impedance UNTIL you reach the current limit of the amp. Doubling maximum power only matters at MAXIMUM power, having say 50w @ 4ohms and 75w at 2 ohms is barely a DB in difference anyway(compared to if it was [email protected]) and not an indication of sound quality at all. That same amp running a db down may be capable of exactly doubling output with a halving of impedance.

Maximum power with a given impedance is also unrelated to frequency response of the amp, noise, THD%(and where and how that THD raises itself), slew rate(how fast an amp can swing voltage-kind of like punch?) etc. All of these combined are what actually makes a good amp.

As long as an amp is fairly well regulated within its power limitations then it won't have any real adverse effects on frequency response as impedance changes over frequency for a given speaker(remember that some/most speakers have significant peaks and dips in impedance). 

Most of the above doesn't apply in pure SPL as more power is always better, but if the amp is rated 'optimistically' it doesn't help. An increase in power output of say 75% instead of perfectly doubling may make a slight frequency response change where impedance drops , probably only 1db though.


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