I know DEAD HORSE.. but if you feel like it,.. Help me with Class A/B vs Class D.

Hrmm.. So it's a situation of SOME Class D amps sound as good as A/B amps.. you just have to be in the know on amps.

Hrmm..

What about

Precision Power PPI P900.5 (p9005) 5-Channel Phantom Car Amplifier

For an example?

Have some Class D amps that are 100watt x 4 at 4 ohms that are in the same SQ as class a/b ? And what specs are you looking at to determine that the Class D amp is as good of SQ as an A/B amp?

If it were as simple as looking at specifications, like THD, and so on.. I could figure it out on an amp by amp basis.

I would suggest doing some reading on the differences between class A, class B, class A/B and class D amplifiers. You will find that these circuits have been improved over the years and some of them have been all but abandoned because they are horribly inefficient, heavy and of course, huge.

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That's what I do.. I ask questions.. and I research on my own. I didn't ask this question blindly. I have my own opinion of A, A/B, and D. I tend to ask questions without a pre-conceived notion or bias either way to try to get both sides of the coin.

My own opinion from what I've read is just what you said.. that technology has improved,.. and it is difficult to abandoned what we KNOW sounded good prior for something new. It's difficult to see amp 1 that's say class A/B at 500 total RMS watts,.. for say $450.. then amp 2 that is class D at 500 total RMS , for say $225 and think to ourselves,.. the class D must be just as good. In *general* you get what you pay for.. to some greater or lesser degree.

In this case.. it still applies I'm sure,.. but from what I've read if you can generally get a class D amp of the wattage you need for about 30-40% less cost than the A/B amp of the same wattage. Further, the sound quality you are going to get from the "D" amp is going to be every bit as good audibly anyways as long as you stay with a reputable brand.

Obviously you can't go buy a $85 dollar amp to replace a $650 A/B amp and expect the same quality. But you can buy a Class D amp that's say $200 instead of that older 'tech' A/B amp that is $325 or so.

Technology has improved drastically in the electronics industry and because of that, the downsides of class D circuits have been all but removed... especially with respect to the limits of human hearing. But of course, there are those die hards who will never like something new because their something old seemed so wonderful.

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Agreed. I work as a network engineer and system designer. So I am actually quite used to the changes in technology.. not particularly amps and speakers,.. but the trend in general is similar.

And of course, those die hards indoctrinate their progeny into believing the old is the only good and that's why you can still buy a $30,000.00 class A amp that produces 10 watts per channel. And, you can connect your $25,000.00 record player to that amplifier so they can listen to the wonderful 250-10,000 Hz frequency response of your aged vinyl... complete with all the original hissing and scratching they think they always loved so much.

I'm not joking and I'm not being sarcastic. I spent a number of years in hi-fi home audio and the money people spend on wire and antiquated technology never ceased to blow my mind. And for what? For a sound quality difference that at it's best could only ever be detected in an anechoic chamber by a $10,000.00 RTA, if even then.

In the end, I don't mean to offend... I'm just trying to save you from analysis paralysis. You're clearly not well versed in electronics or audio and that's perfectly fine. I understand that you want the best for your money but you're following the path of others who don't understand any more than you and ultimately, you'll wind up spending a shite ton of money on nothing more than you could have gotten on a reasonable budget if you continue to worry about details you don't understand.

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No offense taken. I am highly analytical by nature. At the same time I am sensible and in the end I generally find the right solution for whatever I am seeking.. especially involving electronics/tech.

The bottom line,.. is that I'm seeing due to the technology/switching change and refinement that has occurred with class "D" amps, that I can purchase a smaller, cooler, amplifier to meet my needs for less money than the A/B amp I would have otherwise purchased,.. however, I need to keep it in reputable brands and not try to go too far with the budget. IE: Say I end up going with 100watts x 2 for front stage, and 300watts x 1 for sub (or 200-300 RMS) for sub.. I will end up spending something like $175-200 (maybe less) on a quality class "D" amplifier. Instead of $300-400ish for an A/B.

To me,.. you can kill a speaker with a 1 watt amplifier that has unclean/high distortion much easier than you can kill a speaker rated at say 100watts rms putting a very clean 150watts RMS power on it. Clean power is safe power. I'm obviously not going to go beyond rated specs, but it's just a general mindset I have. Further, I tend to think having a bit of headroom in a good clean amp is the best option if possible. IE: Going with an amp rated at 125watts RMS x 2 for 100watt speakers and rated at 400watts rms for the sub and putting 300watts RMS on the sub. Keeping the gains at 70-80% or essentially less than maxed.

If I am grossly off with any of these generalizations let me know.

Thanks for the info guys.

Glad you didn't take any offense at my post, I didn't mean any but after I posted last night I began to think I may have been a bit rude.

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It's all good. Text is difficult to express "tone".. I try to assume the best intentions, and I get when people get a little annoyed. No one on here has made me mad in the least. A few have , rightly so, under-estimated my fundamental knowledge of amps/speakers and so on.. but I have given the impression that I am an absolute noob, so I expected it.

In general, I agree with your methodology but at the same time, I've helped people who drove themselves half insane from over analysing things they read online. And sadly, most of what they'd read was mythology, to say the least.

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Good to know,.. I will over-analyze it's my personality, always has been. I know it can be annoying, for that I apologize.

As for the generalizations, I agree with headroom 100%. So much so that I often run 100% headroom, lol. But what I don't agree with is the statement about gain. There are very few instances where the gain on an amp should be turned all the way up. And when there are aftermarket head units driving the amp, the gain shouldn't be set at more than ~50%.

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This is a new one for me. I planned on going with 70-80% gain based on the amps I've been looking at. Given most of them have ~20% headroom based on amp RMS ratings per channel vs. speaker ratings (individually) rms.

Example,.. Amp 1) 125watts RMS at 4ohms on 2 channels -- I install 100watt components up front,.. I dial in the gain with a DMM to the voltage of 100watts RMS at 4ohms, which will by 70-80% (or so) on the gain control.

An amplifier can produce it's full rated power with the gain in the lowest position... if the preamplifier voltage is high enough. Likewise, if the preamp voltage is very low, then the gain must be set very high. This is because gain is not a volume control, it is a signal matching pot. Higher preamp voltages mean a "lower" gain setting and vice versa.

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Believe it or not I've been reading and watching videos of online classes for certifications and such that explain much of this stuff (more than I probably need to know).. but more knowledge never hurt. Anyhow,.. I do understand the pre-out voltage is what is "amped".. So if it's low .. say 2volts the amp has to do more work, as it's amplifiying ~2volts. The pioneer AVH-P4100DVD headunit I have runs 4v pre-outs, which is fairly typical of decent aftermarket headunits. So The amp will be amplifying a 4v (maybe a touch under, as I know the pre-out voltage isn't an EXACT 4.0v) signal.

So, say my pre-outs were 6volt for whatever reason.. the gain would be set considerably lower,.. and would reach the proper voltage on the positive terminal well before a pre-out of 4v would.

I was planning on using the formulas.. which frankly are on charts now -- ie: at 4ohms on a speaker rated 100watts @ 4ohms should run 20.00volts -- So I planned on setting the Headunit to 75% volume, putting bass/treble, etc to zero.. playing a 1k solid tone.. and using my meter on the positive terminal of the amp and slowly moving the gain up till it hit this 20v mark. (Is this not a reasonable way of doing it?)

With all that said, you can sometimes reduce the gain in order to match the power rating of the speaker(s) but, not if the preamp voltage is so high that the gain is set at it's lowest position.

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I can only refer to the method I've learned so far,.. adjusting the voltage by mathematical formulas based on the true voltage coming in from the RCA pre-outs,.. and the speaker RMS rating at 4ohms (in my case). I don't anticipate my 4v pre-outs on an amp that pushes 125watts RMS per channel is going to be dialed in properly at a gain of zero on the amp. But, maybe you can shed some light on this, or link to something if you want.

Thanks for all the advice!

to make is easier for you, look at your set up, post how much wattage you need and for what application like what speakers or subs you are trying to power, and give a budget and people will chime in with what they think is a good amp for you. when i look for an amp class d or class a/b is the least of my worries.
but short answer to your question to me class a/b is older technology hence more expensive and clunkier and class d are newer and more efficient.

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I am looking to power two front component 6.5" speakers (with 3/4" tweeters) that are rated at 100watts RMS, and now, an 8" sub rated at 100watts RMS in a sealed enclosure.

I am now content on a Class D amp for size and temperature of the amp given it will be mounted in a closed compartment of the vehicle.

The only contemplation I'm making now is whether I should put in the components up front,.. PLUS put in 6.5" coaxials in the rear (behind seats about shoulder height) in the factory location, along with 8" 50-100watt sub. I don't know if putting in 4 mids/highs is necessary, OR if that would be too much for the 2 seater car.

But, again, thanks for the A/B, v. Class D affirmation. I'm most certainly going with a reputable brand Class D amp now.

Lower preamp voltages don't cause the final amplifier to work harder. They cause the gain to be higher. In simple terms, if I have an amp that produces 10 volts and I have a 1 volt preamp signal, my gain is a factor of ten. If I raise that preamp signal to 2 volts, my gain is a factor of 5. My output voltage doesn't change and the reason why it doesn't is because my amp is only capable of amplifying any signal it receives up to a 10 volt maximum.
Now if I take my 10 volt amplifier and 2 volt preamp signal and set the gain as if I had a 1 volt signal, I'll still only have 10 volts of output. But what I will introduce into the equation is distortion. Assuming you know what a sine wave looks like... the peaks of the upper and lower crests of that sine wave in my amp are 5 volts above and below reference, for a peak to peak voltage of 10. And when my gain is set correctly, there is a nice, even crest on both peaks. But when I raise my gain factor, those peaks become compressed and flatten out because I'm asking my amp to raise the amplitude of those peaks above its ceiling. That is clipping or, distortion, and it is the leading cause of death among speakers. It is also the reason why the DMM method of gain setting is not reliable.

DMMs measure RMS (or close to it) and RMS isn't where distortion occurs. Moreover, a head unit volume setting of 75% may or may not be distorted, depending on the quality of its preamp and the source it is playing. Those are two more potential entry points for distortion and again, a DMM cannot see them.

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I got it,.. honestly, understood all of it. I do know what a Sine wave looks like,.. and with my research and online classes I've learned the patterns of the wave.. How, let's just say on the headunit (I'll have the 12v from the battery (again a generalization.. I know voltages differ) -- The middle of the "rails" would be 6v,.. the bottom of the sine wave 0v (ground), and the top crest +12v. -- So take that middle of the rail in the headunit at 6volts.. and apply 6vp/sqrt(2) = 4.2 Volts, thus this would be the 4v Signal coming from the pre-out(s) (Again, I know this voltage isn't going to be this perfect theoretical 4.2v) -- It goes into the Amp which then , well, amplify's this voltage and so on.

Now, if DMM's were as easy as I make it sound to dial in a system,.. then there wouldn't be O-scopes and other equipment to adjust a system from the amp to EQ's , crossovers, et al.

That said,.. If I buy an amp with some headroom. Let's say I need 100watts RMS (as the speaker is rated (and it's a quality speaker) ).. and the amp I purchase is a quality amp that can push 150watts on that channel,.. That leaves some decent headroom (and the way I see it.. a little room for error, given I'll be dialing in with a DMM). So in this example,.. if I set this headunit AVH-P4100DVD - In-Dash Double-DIN DVD Multimedia AV Receiver with 7" Widescreen Display | Pioneer Electronics USA Which is the headunit I have installed to 75% (some say go 80-90%.. most say 75%).. volume,.. set bass/treble to 0/zero and I suppose set the Parabolic EQ flat? -- Then have the amp gain on zero to start. Put in 1khz Sine wave tone off a CD (or usb stick) that plays for 5 minutes straight.. and go to the amp positive terminal, stick the DMM on the positive terminal,.. and slowly move up the gain for this channel(s) until my DMM reads 20v on the nose,.. And I'm obviously listening at the same time,.. and no distortion is audible,.. Then perhaps I put in a clean song.. (I know music //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif ) -- and listen closely to it,.. That should be a reasonably safe way to dial in the amp given I don't have the O-scope or other such tools, no?

Then for the sub I'll repeat process, but play a 40hz sine wave .. And adjust the sub channel(s) gain for voltage for 4ohms at Subs RMS rating -- Let's just use 100watts RMS on an 8" sub for ease of math, and coincidentally it would be the same voltage rating as the front speaker(s),.. to 20.00v on the DMM,.

That's the only way I know how to do it without several hundred to several thousand dollar equipment that would obviously be foolish for me to purchase. I'd love to have a scope where I can watch the Wave in real time.. to ensure the peaks and troughs don't flatten out (clip).

I've heard people tell me that going to the "trouble" of using a DMM and doing what I just described as being a waste of time.. to set everything where it distorts then back down just slightly and you are done.

In my opinion,.. spending 10 minutes or so adjusting voltage playing a tone that's right for the speaker type (be it a mid/high/ or sub) and having a DMM on the positive terminal and taking my time adjusting the gain from zero up to voltage is not a waste of time,.. nor difficult. Why chance it? Why not dial it in the best you can with the tools and knowledge you have?

Aside from having the O-scope or other tools needed to really see what is going on,.. I am left with little choice other than to bring the car to a shop that does have these tools (which I'm willing to bet quite a few don't even have them.. and adjust by ear, or at best with a DMM.. but that's a guess) and tell them, I need my amp dialed in please.. and pay them $100 or whatever fee they would charge.

I agree with you! I understand, granted at an early stage of learning these principles, the dynamics going on and why using just voltage readings doesn't guarantee me "Safety" or even being at the right gain for my needs -- But, am I wrong in the broad generalization that purchasing a/an Quality amp with say 50% headroom (or more) over the RMS rating of the Quality speakers gives me a better chance of dialing it in using the DMM without introducing distortion and/or clipping into the equation?

You obviously know the science of this quite well, and are used to doing it the proper/best way possible -- It shows by your responses, and you being the OWNER of Audio Anarchy //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif -- However, I am trying to do things "right" the best way I can with what I have available to me. I also know just because X percent of people dial in their amp gains by ear, or at best with a DMM (some maybe not even really knowing what they are doing or why).. doesn't mean that because they do it this way that so can I, and be trouble free.

I just feel fairly confident in buying a quality amp that has SOME headroom in it,.. with quality components and proper passive crossovers, and a headunit that I linked above that from what I've read in it's specs puts out a great, clean, 4v signal (It's not the best in the world.. but it's certainly mid range I would say) -- That dialing it in with the DMM with the tones I mentioned should produce a safe environment for my setup.

If not, let me know. This is a bit odd, cause I am not overthinking this part -- I am solid and confident in purchasing the components as mentioned and using the method I explained,.. and you are informing me.. "Hey not so fast.. !" //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

You are 'somewhat' close to me.. as I am in Birmingham, AL -- but it's still a 6+ hour drive. If you were say 2 hours away, I'd say screw all this and come to your place and let you help me pick out everything and have your employees install it all. Unfortunately you are nearly 7 hours away, so best I can do is take your advice.

Thanks for all the help,