class d amp

[ridney]

i bought a power amp for my new 3-way speaker in a 2 channel stereo configuration and now i find it a little bit lacking on the low end bass. its pretty weak with low volumes and okay when loud, not overpowering the mids and highs but would have wanted a little bit more weight and punch on the bass. is this a typical sonic signature of class d amps? would a class a/b amp make a huge difference?

[ridney]

i guess i was not pretty clear above, about a month ago i bought a marantz nr1402 av receiver together with a B&W 684 floorstanding speaker for my HTPC which i use for movies, music and games. I have connected my htpc via a toslink optical cable to the marantz nr1402 for audio only as my gpu (afox hd 6850 low profile) is not passing audio through displayport-to-hdmi adapter. hdmi is connected directly to my hdtv.

when everything was setup i tested it with a blu-ray movie (inception) and the b&w 684 was really impressive, very good at resolving high to low mids with deep and low bass. i thought i would never have a need for a subwooder as the current set-up sounded so good to me.

so now i tried to play music through my av receiver from my htpc using mediamonkey and flac as my source. suddenly, the impressive sound from the movies was nowhere to be found, bass was very weak and highs were harsh and bright. the whole thing sounded like it was coming from a cheap desktop speaker and i just couldn't believe what i am hearing. so i contacted my dealer and asked them why it sounded so good with movies and awful with music and they replied to me that i needed a more powerful amplifier to drive my B&W 684s to get the best out of them and to make the sound more warm and recommended me a Rotel RB-1562 100w/channel Class D amplifier.

so a week after that, i bought the amp and connected it to my marantz nr1402 via Front L/R pre-outs and the B&W 684s bi-wired through the power amp. now the harsh and bright highs were gone and it sounded a little bit warm but the weak bass is still there. it really is weak that i thought i had run them out of phase but clearly it wasn't. so i thought that perhaps the dac from my marantz receiver is the cause for the weak bass and from further reading through the web, I concluded that i need a dedicated usb dac for music as it gives pretty deep and tight bass and would probably solved my problems.

after a week i bought an Audiolab M-DAC and connected it to my htpc via a usb cable which will upsample everything to 24/96. Since the M-DAC is also a digital pre-amp, i directly connected it to my rotel rb-1562 so as to bypass the marantz receiver and isolate the weak bass problem. after playing a few songs (hip-hop/club/dance type) the weak bass is still there and may have just slightly improved a bit but it's still pretty weak. i compared it with my B&W zeppelin and it soudned way way better than the B&W 684s. the zeppelin sounded fuller with really tight and fast bass and now i am starting to get frustrated as i have already spent a lot on things that haven't really improved the situation. so again, i contacted my dealer and told them that things are not improving despite having a pretty beefy power amp and having a very good dac. i also told them that my B&W zeppelin sounded way better than the B&W 684s and that I am considering trading-in the 684s for another speaker. fortunately, the dealer was kind enough to allow me to return the 684s in place for another speaker.

so a week later, they delivered me a brand new B&W 683, now a 3-way speaker (which is the same as my B&W zeppelin) compared to the 2 1/2-way B&W 684s and should probably solve my weak bass problem. i connected them bi-wired to the rotel rb-1562 and the audiolab m-dac as a pre-amp by-passing the marantz nr1402 av receiver. now that everything was setup and guess what? the bass still sounded weak but only during low volumes. if i turn it up loud enough i can hear a really nice bass from the 683s but nothing like my B&W zeppelin which was very punchy.

all i wanted was to listen to music the same way as i listen to my B&W zeppelin in my living room. as i am really new to the world of hi-fi audio and have no experience at all, i am having a hard time trying to find the weakest link in the chain in my set-up. i don't think it would be the cables as i am using a decent one and my interconnects are pretty good too. so my question to you guys would be, would the class d amp be the weakest link in the chain and is the sole reason why i am not having the bass response i am looking for?

[Nanometer]

Looks like you have discovered the world of fine tuning the audio experience. There's a lot of factors that can affect what you are talking about and I'll do my best to cover them all.

First, your source of media sampling rate should be 44.1 KHz or more. Up converting the audio will gain you nothing if you don't start out with a good recording to begin with. 44.1khz sampling rate is standard for CDs, but there is a lot of content that exceeds that by 8X. Are those 8 times better in quality? Definitely not, as it is severe diminished return. It is, however, nice to know that you are using a quality recording though.

Next, is your means of transferring an audio signal(interconnects). USB is a no no in my book if you care anything about audio. Anything else would be acceptable: RCA, Toslink, HDMI, Balanced XLR not necessarily in that order, but pretty darn close.

Power can be a huge issue when driving a lot of base through some decent speakers. Your marantz in all honesty is a piece of **** when compared to your speaker system. I firmly believe that for however much you spent on your entire speaker set, you should spend between that exact amount, to about half that amount on your stereo amp. A good amplifier is just as important if not MORE important to good sound than your speakers. A good speaker will only sound as good as a poor amp. I agree with the assessment that your marantz was possibly a little lacking, however I do not believe that is the source of your problems.

There are settings available in many receivers to send the bass signal to your tower speakers should a subwoofer not be available. Effectively it make your system sound a little more impressive. However when you turn on the music, the bass that was, is no longer. Stereo music is not encoded with a subwoofer in mind, and most serious audiophiles who are music goers will not use a subwoofer, period. . What this means is that you are forcing your tower speakers to play all the bass in the music. Bowers 684s are very nice speakers and should be able to handle some decent bass.

When you are using your amp/receiver settings, you should be using the automated process to give you a basic setup for speaker distance and a lot of important presets for proper speaker performance. I highly recommend running it.

You also want to keep in mind that there are different modes for using your speakers. Such as a mode for movies, and a mode for music. During a music listening mode you can often up your bass signal in small increments until you reach a desired level.

Generally speaking, bi amping can be more of a market gimmick then actually giving performance benefits. The only way you could benefit is if you are starving your speakers of power, and your second amplifier can provide the power needed to listen at the levels you wish to listen to. Setups will vary, but this is just a general rule of thumb.

I also recommend using google to find how people setup a standard stereo or home theater. The presets and especially equalizer settings can be very important to proper sound recreation. I personally like to use a tone generator to do frequency sweeps to discover peaks and dips in my systems range. From there I can make corrections to even the response to my liking.

Last and foremost, please read the manual to your electronic and stereo equipment. They were included because they are important! It is the first line of defense for a lot of the problems you described. I also recommend reading up on Hometheater.com for some basics of audio response and tuning.

If you have any specific questions I will be more than happy to answer to the best of my ability

[STEvil]

I prefer A or AB.

[alpha0ne]

Power can be a huge issue when driving a lot of base through some decent speakers. Your marantz in all honesty is a piece of **** when compared to your speaker system. I firmly believe that for however much you spent on your entire speaker set, you should spend between that exact amount, to about half that amount on your stereo amp. A good amplifier is just as important if not MORE important to good sound than your speakers. A good speaker will only sound as good as a poor amp. I agree with the assessment that your marantz was possibly a little lacking, however I do not believe that is the source of your problems.

Great advice Nanometer

Whilst I am a complete nub re music playback I would have considered a higher spec'd amp would have better suited your very nice B&W 683 speakers

Also USB is the very last interconnect for any type of audio, I'm surprised there is even an option to connect this way

Good luck with the quest !!!!

[Hell Hound]

Get BD class amp for best bass reproduction,AB if BD isn't available.

When considering what you are getting for your dollar in relationship to the power output, the STARDUST technology makes the Class bd amplifiers (1,100 watts for $699.99) more affordable in relationship to other typical class AB amplifiers since there is less current consumption from the charging system. In the case of Class bd amps, there is less heat generated due to the Class bd STARDUST technology. As a result, the cooler internals makes the overall performance more reliable.

Class D amplifiers work by altering the "balance" of an ultrasonic, square-wave carrier, set at equal positive and negative time duration-called 50 percent duty cycle--for no audio output. Audio output is achieved by modulating the ratio of the time the wave stays at its positive and negative states. Audio is recovered by passing the varying average value of this wave through a low-pass LC filter.

A serious drawback of this type of Class D is the large rail-to-rail square-wave "carrier" produced, leading to heating and complexity. A typical Class BD amplifier solves this problem by subtracting away this carrier in the external load. However, because the subtraction is external, it is well known to specialists of this field that it leaves an untamed, full rail-to-rail switching signal on both output leads, a nightmare RFI problem which has eluded solution during the 30 year Class BD history.

Rockford's Class bd amplifier, with its Stardust topology, suppresses the generation of this carrier wave in the modulation process itself-somewhat analogous to single side-band (SSB) radio practice. This novel solution allows all the advantages of Class BD to finally be employed-without an RFI output problem.

[EniGmA1987]

Im surprised no one has asked this in the last few posts:
How do you bi-wire two speakers using a single stereo amp?? Especially two, 3-way speakers on a single stereo amp... It just doesnt seem possible to me. Either I do not understand bi-wiring properly or you do not.

[[DANGERDAN]]

Props to Nanometer always giving great answers and helping people , i too agree with whats been said and will add on top that class A/AB amps make a difference when it comes to low level volumes in performance with accuracy and sound quality. Class D amps fail in this department because of its design difference, class D's can be very nice but it requires a lot more complex design and more expensive parts to compare to a class A/AB. Also to add on that all equipment add their own tonal ring to the signal changing it in different ways both for good and bad and that nothing is perfect especially the audio world where everyone perceives sound differently due to their organic structure of the ear drum and other contributing factors.
You have some nice speakers by the way i am quite a fan of B&W systems having listening to a few myself just recently but you must look at the fact that these are floorstanders with a 6.5" cone trying to be used as the bass driver, now there's nothing wrong with that but your not going to get shocking floor shaking bass with that and i don't think they ever intended it that way in the first place. I believe its more accuracy that it goes for and that's what i heard when i viewed them myself and because of the small driver they were not as open in a large open space than they were in a small one which leads me to my point that any great HT system needs a dedicated Sub speaker to really bring out the musical wow factor regardless if your after heavy or accurate bass. Also note that as it states a frequency response on the test sheets they are not always meaning what you think, the speaker probably starts to drop off in SPL really early which is a reason for decreased bass output.

You must as stated before make sure you don't use USB as a interconnect and make your cable runs short and not long to ensure a decent transmitted signal and use a thicker wire instead of just BI-WIRE as all that does is increase the pathways allowing more power to be transferred which is what a thicker cable will do more effortlessly anyway so don't bother confusing things. Make sure that your also not comparing songs that were not really designed for bass as not all music is, try find songs that are known for nice bass depending on what you are looking for as there are many types. If you want floor thumping kicks try rap/hip hop like eminem or other assorted artist's or if you like steady bass guitars with smooth texture response try something like jack johnson which has some good quality's that I myself like to use to test a speakers response on bass notes (refer to song "taylor").
For the very best i like to use the Titanic theme song "My heart will go on" as it has really deep sub frequency's that go into the sub 20hz range which really test the dynamic ability of a speaker which usually are left for subs to work on.


One more thing too is that from what i know audio reproduction equipment are designed to reproduce the frequency band as accurately as possibly with equal sound pressure levels across the entire band which you usually see in their test specs sheet however... from my still continuing research i always find myself equalizing my sound systems fairly the same in a pattern sense. As it stands our ears are not accurate as i have mentioned we have a heightened ability to perceive mid frequency's so its only natural that you might find you like it better by either decreasing the mids and or increasing the highs and lows and what you will find if you spend a fair bit of time messing with EQ's is that most of the time you will follow a pattern.

Last part is just opinion point of view however its not something i can prove, how do you usually EQ your systems Nano ?? do you find the same scenario as i do?.

[Nanometer]

Thanks for the accolades!

Im surprised no one has asked this in the last few posts:
How do you bi-wire two speakers using a single stereo amp?? Especially two, 3-way speakers on a single stereo amp... It just doesnt seem possible to me. Either I do not understand bi-wiring properly or you do not.

Bi wiring is literally attaching two separate wires to one amp, and then connecting them to the same speaker. It effectively halves your wire resistance, which double the power capacity of your speaker cable. It also effectively does just about nothing to improve sound, provided you use a decent and properly sized wire to begin with.

Bi-amping and tri-amping is a different subject. You basically use your audio signal and use either an "internal" y-adapter or an external cable y-adapter to drive two completely separate amplifiers. You attach the amplifier out to separate terminals on the speakers which can double your effective power. Bi-amping using a receiver is a little different because of the limitation of what the internal power supply can provide. Therefore, it is generally considered a marketing gimmick to bi-amp your speakers using a receiver, but I won't lie, I still do it regardless. One benefit is not having to work your power amplifier as hard by using two separate amplifying circuits instead of one when you use bi-amping. Bi-amping with separate external amplifiers can effectively double your power, should you want to.

Generally speaking you cannot bi-amp on a stereo amp, but you can bi-wire... if you really wanted to. Just use 10 gauge copper cable and be done with it.

[ridney]

thanks for the input guys, that's a lot of information to go through. I understand that class ab amps are better than class d but how much better is the question? would it be a noticeable difference if i upgrade to a class ab power amp? i have been reading a lot about this lately and what they say is that there's no noticeable difference between the two, so if that's the case then there's no point changing my power amp. i also prefer these class d amps as they are very efficient and consumes a lot less power than the class ab counterparts. my rotel rb-1562 100wpc class d amp consumes only 130 watts at full power while a class ab rotel rb-1552 120wpc consumes rather a huge 440 watts. that's a lot of watts right there for a mere 20 watts difference in amplification.

i was also thinking that perhaps a better solution to my problem would be to get a pre-amp to pair with the power amp as i think the digital pre-amp of my m-dac is not good enough and currently i am using my marantz av receiver as a pre-amp. now would it be a better value for money if i get a rotel rc-1580 pre-amp or just upgrade to a better receiver like a yamaha rx-a1010 and use it as a pre-amp? actually, i am not having any problems with my av receiver, in fact i like it very much as the sound is very impressive with blu-ray movies and there's no difference to sound quality if i use the marantz to drive the 683s or use the rotel amp to drive instead.

i have also fiddled with the EQ settings on my av receiver and from my recent testing, it did made some improvements to the bass response and made it seem punchy enough. i enabled tone settings and adjusted the bass and treble however i just left the EQ settings to 0. if i am using audyssey, the sound quality would be really thin and really digital like a metalic sound, previously i was using the "pure direct mode" as i don't want the av receiver to color the sound.

by the way, i'm using an IXOS 12AWG speaker cable and black rhodium rythm rca interconnets so i don't think i have a problem with my cables. and the connection between the htpc and dac is using a usb cable, although i could also connect them through coax or toslink but the designer of this dac has specifically recommended to use the usb for best results as it is aynchronous, so i guess there's no problem with using usb as interconnect.

here's a list of what i have:

HTPC: MSI 890GXM-G65, AFOX HD 6850 LP
AV Receiver: Marantz NR1402 5.1 50wpc
Stereo Amp: Rotel RB-1562 100wpc
DAC: Audiolab M-DAC
Speakers: B&W 683

[Hell Hound]

Switch to coax there should be diff for sure.

[Nanometer]

If I were you I would get a Marantz 7xxx series receiver, a Denon 3XXX series receiver, A Pioneer Elite, A Yamaha Aventage, An Onkyo 1XXX series, An Anthem 300, Integra 30 series, or anything else from a reputable company. You don't need a stand alone amp for your whole system, and if you do, many of the above listed have Preouts except for the Anthem and maybe a few others listed. The receiver you pick should have a rated power supply of at least 6 amps, which is about 550 Watts of useable power. Check the specs, or manual for it. If not able to locate, go by 120 Watts 2 channel driven or 80 Watts all channel driven.

Your options I think are: Get a decent receiver, and if for whatever reason you want a better quality amp, you can upgrade to a multi channel amp and use the preouts from your receiver. Just make sure if you want this path, that you make sure that the receiver has preouts. This the method I currently use. For your needs, I don't think its justified, but time will tell, so buy accordingly.

[Kingcarcas]

What's a good entry level AB amp go for?? I know there's a HK AVR on ebay for $400 with pre-outs for my eventual Monitor 70s but i'm wondering if it's worth it to amp since they are entry level speakers. I don't know anything about Bowers TC, but what i've generally found from "audiphile" brands is they try to be accurate and bass shy. I owned a pair of Shure headphones and sure they were great, but lacked bass, they were considered "neutral" sounding.
Generally bass is looked down upon and only casual buyer speakers try to wow you with that so i can see your BWs being bass shy on purpose. Which sucks for the basshead audophile who still wants high quality.
I guess this is why they say you should try to listen to a pair of speakers before you buy, i couldn't be more happy with the Pioneer budget line (best bass in a bookshelf i've heard) USB DACs are all the hype now, guess i'm glad i didn't jump on the bandwagon.

TC I see those speakers only have two drivers, i'm pretty sure if you want good bass without sub you need at least 3 or 4 in the speaker esp. since they are lower to the ground to transmit those sound waves.

[[DANGERDAN]]

I have heard good things about the Rotel RB1582, the Harmon Kardon 990 and then the XPA-3/2 are all my favorite choices. Each type of speaker has their own favorites so try looking for which suites the B&W as like with klipsch the XPA and Rotel are highly recommended.