more bass from a "class A" amp? (1 Viewer)

[Geno]

I used to run all 5 channels thru my "class a-a/b"
b&k video 5 "5 channel x 105" amp and I had split my LFE to both channels on my "class a/b" nikko "2 channel x 120" amp.

as an experiment, I am now using 2 channels on the b&k for my sub and the nikko is now running my mains.

From the few days of listening that I have had it setup this way, I have noticed that the low bass seems to come out cleaner or less restrained. I really dont know what it is but I thought it had something to do with the circuitry.

can anyone else explain this?

 

[JohnSer]

I know B&K makes a marketing point about being class A -A/B, but it is my understanading that almost all class A/B power amps use class A for the initial stages, and only class A/B on the final output stage. You are probably hearing just minor differences in the amps.

JohnS

 

[Geno]

yes the b&k only uses the a/b AFTER 25 watts, which I rarely have it that loud.

I guess Ive got myself trained to hear the sublte differences now. but now I have to get a good class a amp for my mains

darn upgraditis

anyone else have explinations?

 

[JohnSer]

I have to get a good class a amp for my mains

Pure class A are big, heavy, and expensive, but probably sound better (never had one). I am afraid, that with all the new amp classes, rail switching and digital switching, that good ole class A/B will be relegated to high-end audio, like class A is today. Once the mass market has this perfected enough, their entire product line will eventually switch over.

JohnS

 

[Geno]

lets hope that doesnt happen.

mass marketing has already pulled the wool over many peoples heads about quality, design, and clarity.
IMHO Bose, mp3's, NAFTA, THX, all have contributed to the downfall of mainstream audio.

 

[Yogi]

Class A amps have very high slew rates because they are always on for the full waveform and because of lack of switching between the complimentary stages. So they generally have well defined bass.

 

[Yogi]

Also remember MOSFET amps in general have better bass response and perhaps thats what you are hearing from the B&K.

 

[Geno]

I believe the Nikko has Mosfet amps too though

 

[Yogi]

I believe the Nikko has Mosfet amps too though

Sorry didn't know that.

 

[Michael R Price]

I don't think high slew rate has much to do with bass performance. I don't have any idea what contributes to good bass performance. My guesses would be a good power supply, high power and high damping factor.

 

[Chu Gai]

Perhaps adequate current in reserve in the way of good power supplies and substantial capacitors. The DF for low output impedance devices is pretty much irrelevant.

 

[Khoa Tran]

just look at a pass lab amp, pure class A, THEY ARE REALLY BIG!

 

[Michael R Price]

What damping factor is good enough to be irrelevant? 20, 50, 100, ?

 

[Yogi]

Taking into account real speaker cable impedances any damping factor over 100 is good. Has anyone done a level matched DBT to see if there is an audible difference between a DF of 100 and 1000? Sorry couldn't resist throwing that in.

 

[Chu Gai]

Consider the following article by D. Pierce on DF.

 

[Brad_Harper]

The class of an amplifier has nothing to do with it's bass response. Elimination of crossover distortion is the main reason for using a Class A amplifier. This comes at the expense of efficiency. That is why they are often bigger then a class A/B or class b because they need larger heat sinks. Chances are your new amp just has a better power supply (it had better if it's class A) so there is just more current available for those low frequencies.
Now as far as MOSFETs go. They also have no bearing on frequency response. MOSFETs are just a more robust transitor then a BJT (Bipolar Junction Transistor). The truth is MOSFETs actually increase distortion.

 

[Yogi]

Nice article Chu. No wonder my tube amp with a damping factor of 20 sounds as taut as my B&K amp with a DF of several hundred. I always thought that anything beyond a DF of 100 would be irrelevant but I guess it is even lower than that. Makes me feel good even though I am not into specs.

Thanks again Chu.

The truth is MOSFETs actually increase distortion.

Just like toobs

 

[Geno]

well whatever the reason, it sounds better. i might just have to upgrade that stereo amp to a good a a/b amp too

 

[Yogi]

B&K amps are pretty high current. My Ref7250 does 200@8 and 375@4. In HT mag it was measured to put out (with 2 channels driven) over 200W@8ohms and a little over 400W@4ohms. So as we can see it almost doubles its output with half the impedance. Thats a good indicator of a robust power suppply. That in itself would make a whole lot of difference in handling of bass frequencies.

 

[Chu Gai]

Yes, that article, as well as others, basically debunks the myth that the damping factor of an amp somehow controls the performance of a speaker to any signficant degree. It's contribution is orders of magnitude less than say of the dampening effect of the back emf that's generated by the voice coil. However Yogi, since damping factor and output impedance are intimately related, as your DF goes down the output impedance of your amp can rise to a significant enough degree such that it does result in a non-linear FR in conjunction with your speakers. Old news though. I seem to recall reading somewhere that the lower limit for audible interactions was somewhere around 20 or so.
My good man, you should be into specs!! After all, a pair of Aces beats a pair of Kings, and IMHO, a pair of 38D's beats a pair of 32A's.
I agree with your B&K assesment fwiw.