PDA

View Full Version : Digital vs Analog Amps? Which is better?


Mpire
12-30-2003, 12:24 PM
Which is better? A digital amp or the traditional analog amps?

Case in point:

JL Audio 300/4

http://www.jlaudio.com/amps/3004.html

vs

JL Audio e4300

http://www.jlaudio.com/amps/e4300.html

Is it just that the power output on the digital amps is not as high as the regular ones?

Please comment on wich would you use. And what about digital amps for sub use?

Mpire

Steve D
12-30-2003, 02:44 PM
Digital class D amps are only good for sub woofer amplification since they generate high distortion and noise at the higher frequencies.

Steve D

Kaz
12-30-2003, 02:59 PM
First, there is no such thing as a 'digital' amp. It's just a term used in marketing because it's an easy way to describe the way the output transistors run.

Without getting too technical, all things being equal, a Class A/AB amp will likely sound a bit better in high frequencies. But a Class D (or H or T or whatever) will be smaller, weigh less, and run cooler for a given power output. The reason why Class D is popular for sub use, in addition to the reasons above, is that the noise and distortion associated with the technology is inaudible at subwoofer frequencies, so it becomes a non-issue.

mkh
12-30-2003, 06:48 PM
If your "better" means sound quality, then Class A all the way! No substitute. The only drawback is heat. But sounds so much better.

/\/\
01-01-2004, 01:32 AM
Use a Class D for subs and A/B for mids/tweets.

What are your system specs?

/\/\

HW
01-01-2004, 04:31 AM
from a quick description of "digital amps" from my co-worker, it sounds like "digital amps" use pulse width modulation (pwm) to represent amplitudes. the resulting pwm signal is then filtered (my guess/assumption) using passive filters to remove the high frequency components created by the square waves of the pwm. reason why the "digital amps" run cooler (my guess) is that the transistors are only either "on" or "off" and not something in between like analog amps. not sure but i would think that if the digital signal processor used in the "digital amp" is fast enough and the final stage transistors switch fast enough, the "digital amps" would/should sound pretty comparable to the analog amps. but since a fast switching final stage (power) transistors maybe too expensive or not available yet, class D mid/highs amps may not be that doable. :dunno: a class D sub amp seems to use the same tech as those power inverters that allow you to run 120V AC electronic devices from the car lighter plug. the frequency range is similar that of subs as well. hmmm.... maybe time for me to pull out my dsp evaluation board to build myself a class D subamp. :p now where's the nerdy geek emoticon. :eeps:

Kaz
01-01-2004, 07:38 PM
Just don't confuse the fact that it's possible (and common) for class A/AB amps to have a PWM switching power supply with standard output stages.

I'm sure it's possible to get a class D amp to sound pretty good, but since you're doing a rather crude A/D conversion of sorts, it seems better to just try and avoid it altogether. From what I understand, it seems like an easier proposition to work on efficiency from the power supply end where it is what's being modulated in order to keep waste to a minimum. Bob Carver's Tracking Downconverter is an example. BTW I misspoke earlier when I mentioned Class H. Class G and H actually are AB output architectures that use different power rails to maximize efficiency.

Mpire
01-02-2004, 06:33 AM
ok...

Here is my setup...

I have an 01 M coupe, and I am trying to cram two amps in the area where the changer goes...

I have settled on the 300/4 amp from JL audio, and the digital e1200 is small enough to fit in the left over room I am guessing.

So... I was thinking, if going with one digital, why not two...

The e4300 and the e1200, but maybe I should just get the single e1200.

http://www.jlaudio.com/amps/e1200.html

I am just trying to power the JL 6w0 sub that I bought to install in the existing sub enclosure.

What would you do in my situation?

Mpire

mppaz
01-02-2004, 09:14 AM
ok...

Here is my setup...

I have an 01 M coupe, and I am trying to cram two amps in the area where the changer goes...

I have settled on the 300/4 amp from JL audio, and the digital e1200 is small enough to fit in the left over room I am guessing.

So... I was thinking, if going with one digital, why not two...

The e4300 and the e1200, but maybe I should just get the single e1200.

http://www.jlaudio.com/amps/e1200.html

I am just trying to power the JL 6w0 sub that I bought to install in the existing sub enclosure.

What would you do in my situation?

Mpire

I guess I am confused. The e1200 is not a *digital* amp.

There are a couple of key technologies that JL owns the rights to:

Absolute Symmetry AB Circuitry is name for a type a linear output stage that constructs a complimentary output stage out of non complimentary devices. Class AB is the most common type of linear output stage due to its blend of performance and efficiency. To understand this, consider that the amplifier is processing a sine wave whose average value is 0 (no DC). It therefore has a positive peak and negative peak amplitude. In a class B system there are two amplifying devices in series with the series connection going to the load (speaker) and two supply rails. One for the positive and one for the negative. One transistor amplifies the positive portion of the sine wave the other transistor amplifies the negative portion of the sine wave. To correct for the distortion that would occur at the crossover point (near the zero cross) the two transistors are biased on slightly all the time. This is similar to the class A concept and hence the name Class AB.

R.I.P.S. is just a power supply technology that they use that provides regulation for variation in the input supply (the car battery). As discussed above you need two supplies for the Class AB system and it is nice if one of them is negative. Additionally the 12 volt supply from the car battery would put a severe limitation on the output power of a car audio amplifier so some type of power supply processing is required. High performance car audio amplifiers solve this problem by employing a switching power supply. In this type of design the DC from your car battery is converted to a type of AC voltage by switching it on and off at a controlled rate. This Pulse DC waveform is then suitable to be processed by a transformer such that its voltage can be stepped up and its polarity reversed as required by the amplifier design requirements. Most technologies use Pulse Width Modulation (PWM) techniques whereby the average value is controlled by modulating the time the voltage is presented to the transformer within a constant period. Use of R.I.P.S. does not imply that the amplifier is *digital* even though this technology is a form of Class D amplification. R.I.P.S. adjusts the supply rails to provide the required output power independent of the input voltage and output load impedance.

Patented Class D Circuitry: This is the so called *digital amp* technology. Essentially it is a switching power supply configured as a power amplifier. While the topology used is different from what is deployed in the power supply section it is fundamentally the same concept. A common embodiment has an upper and a lower transistor similar to the series connected Class B system. This is then followed by a low pass filter. The difference being that the transistors are either full on or full off and are switched at a rate that is much higher than the highest frequency in the audible range. The benefits are that one can construct a very compact efficient amplifier. The down side is that the sound quality is really not up to par with the Class AB configuration. With today’s technology these types of amplifiers are best suited for subwoofer applications where tons of power are needed but the frequency range of interest is well within the performance capabilities of the switching amplifier. The patent that they hold is aimed at the feedback and control of the switching amplifier. Switching amplifiers are inherently non-linear and present a difficult challenge to control in what needs to be a linear fashion for audio amplification.

A common configuration for multi channel amps is to use Class AB amplifiers for the main channels of the amp and a Class D section for the subwoofer channel. This yields the most compact multi channel amp and could by called *digital* by the manufacturer but the *digital* part is just for the subwoofer. The digital moniker is really a misnomer as you should now be aware. In a power amplifier it really just refers to a Class D of Class D variant topology.

Kaz
01-02-2004, 09:16 AM
The info on that page says the e1200 is a classAB amp (though not 100% conventional). I don't see where it's 'digital' in any way. The e series just seems to be a bit less beefy.

Mpire
01-02-2004, 09:35 AM
The info on that page says the e1200 is a classAB amp (though not 100% conventional). I don't see where it's 'digital' in any way. The e series just seems to be a bit less beefy.

Ok, so answer me a few questions then, please yes or no because I am just getting confused.


Should I get a e4300 for my front and rear speakers? Factory head unit, etc.

Should I go with the 300/4 instead?

Should I go with the e1200 to run the single JL 6w0?

I just want to order this stuff. I am no audiophile, but I want the best quality I can get that will fit in the given space.

Mpire

Kaz
01-02-2004, 09:39 AM
Ok, so answer me a few questions then, please yes or no because I am just getting confused.


Should I get a e4300 for my front and rear speakers? Factory head unit, etc.

Should I go with the 300/4 instead?

Should I go with the e1200 to run the single JL 6w0?

I just want to order this stuff. I am no audiophile, but I want the best quality I can get that will fit in the given space.

Mpire

For your purposes, you're probably not going to notice any sound quality differences between the 'slash' and 'e' series JL amps (what's everybody's obscession over JL amps anyways? They're not traditionally an amp manufacturer...). Get whichever fits your budget and size constraints.

Mpire
01-02-2004, 09:43 AM
Thanks for the advice. I think I will go with the 300/4 and the e1200 for the sub.

Speakers are leftover ADS 345is components and I have to buy new ones for the rear of the car. I am using stock head and wiring.

Anyone here want to buy an ADS P850.2 and some 234is speakers?

The amp is huge. Speakers are too small now for the back of my car.

Oh, and 2 A10s subs. Never even taken out of the box. Have MDF boards to mount them infinite baffle under the rear deck of an E36 coupe that go with them if you want.

Mpire

EdCT
01-02-2004, 09:43 AM
If your "better" means sound quality, then Class A all the way! No substitute. The only drawback is heat. But sounds so much better.

Many amps marketed as class A aren't really class A at all.

They'll say they're class A at low volume, but they're really class A/B amps taking on certain class A characteristics at low volume levels.

Beware of marketing hype.

Incidentally, IMO, it matters not whether an amp is class A or Class A/B, what matters is the sound. I've got all kinds of power amps in my recording studio, everything from old Fender Tube Amps (mostly A/B, except my Champ which is single-ended Class A) to high end monitoring SS devices.

They all sound great - in differing ways.

IMO, as a professional musician, no car stereo is worth big money. After you've spent time in a treated room with GREAT gear, you'll never be satisfied with what comes from a car stereo. It's just a terrible environment for music.

Ed

Kaz
01-02-2004, 09:48 AM
Thanks for the advice. I think I will go with the 300/4 and the e1200 for the sub.

Speakers are leftover ADS 345is components and I have to buy new ones for the rear of the car. I am using stock head and wiring.

Anyone here want to buy an ADS P850.2? Its huge.

Mpire

Man, I wish I knew you had a 850.2 for sale 2 months ago. I may have bought it over the p840 I got off eBay.

Mpire
01-02-2004, 09:48 AM
Too bad you cant fit any ADS amps in the car.

Poor me.

the P450 is 13x11.

The 300/4 is 13.4x9.25

Mpire
01-02-2004, 09:50 AM
P850.2 is 13x16. It wont fit in the coupe.

Mpire

HW
01-02-2004, 10:27 AM
Patented Class D Circuitry: This is the so called *digital amp* technology. Essentially it is a switching power supply configured as a power amplifier. While the topology used is different from what is deployed in the power supply section it is fundamentally the same concept. A common embodiment has an upper and a lower transistor similar to the series connected Class B system. This is then followed by a low pass filter. The difference being that the transistors are either full on or full off and are switched at a rate that is much higher than the highest frequency in the audible range. The benefits are that one can construct a very compact efficient amplifier. The down side is that the sound quality is really not up to par with the Class AB configuration. With today***8217;s technology these types of amplifiers are best suited for subwoofer applications where tons of power are needed but the frequency range of interest is well within the performance capabilities of the switching amplifier. The patent that they hold is aimed at the feedback and control of the switching amplifier. Switching amplifiers are inherently non-linear and present a difficult challenge to control in what needs to be a linear fashion for audio amplification.


wow, thanks for the info. got any links for the diy'er on "digital amps". who's making these audio quality FETs suitable for these "digital amps" :D i assume that the frequency response of these FETs have to be much higher than those used in analog amps. the feedback circuitry for linearity, i'm guessing that this is done at the amp outputs after the lowpass filter. the processor makes pwm width adjustments by comparing the input and output. :dunno: i guess what's stopping people from making equivalent quality amps for higher frequencies are switching rates of available end stage transistors. i'm sure there is enough dsp power out there to handle the processing needed for high quality audio.

mkh
01-05-2004, 10:37 PM
Many amps marketed as class A aren't really class A at all.

They'll say they're class A at low volume, but they're really class A/B amps taking on certain class A characteristics at low volume levels.

Beware of marketing hype.

Incidentally, IMO, it matters not whether an amp is class A or Class A/B, what matters is the sound. I've got all kinds of power amps in my recording studio, everything from old Fender Tube Amps (mostly A/B, except my Champ which is single-ended Class A) to high end monitoring SS devices.

They all sound great - in differing ways.

IMO, as a professional musician, no car stereo is worth big money. After you've spent time in a treated room with GREAT gear, you'll never be satisfied with what comes from a car stereo. It's just a terrible environment for music.

Ed
I agree. A lot of amps are giving out misleading and worthless specs and sound like crap. But for the higher end ones, they are pretty honest. The amp I have can actually run in pure class A or AB at a flip of a switch. And the sound is night and day between the two.

I also agree with you regarding car stereo in general. That's why I just stick with the standard H/K system in my 330i and don't even bother to upgrade. No matter what you do, it's still so far away from a decent home system. Let's hope the upcoming DVD-A systems can get a little closer.