Digital power v ...non-digital power

[figuredbass]

I think one of the reasons the LMII is getting the huge amount of raves on this site is that it is the exact opposite design of the iAmp and 502... it uses a warm, fat sounding class A/B power amp with a newer generation switching power supply... so you get a reasonably 'traditional' sounding SS amp in a VERY lightweight box with a small form factor. Pretty cool!

+1 I'm tending to believe this is true. Though Class D continues to improve, it still seems that a lot of people generally prefer the "sound" of A/B power amps over class D. I would like to know if there is anything at all with class D designs that has not yet reached the performance of A/B designs in an audible way, especially with the lighter amps. My feeling is there has to be SOMETHING, or I would think Class D would have virtually rendered class A/B obsolete by now?

 

[fdeck]

+1 I'm tending to believe this is true. Though Class D continues to improve, it still seems that a lot of people generally prefer the "sound" of A/B power amps over class D. I would like to know if there is anything at all with class D designs that has not yet reached the performance of A/B designs in an audible way, especially with the lighter amps. My feeling is there has to be SOMETHING, or I would think Class D would have virtually rendered class A/B obsolete by now?

One thing is that Class-AB is still cheaper, otherwise the bargain gear would all be Class-D. There is still a broad swath of the market that is more interested in watts-per-dollar than in watts-per-pound.

But also, nothing in music gear ever goes obsolete. The new stuff just gets added to the variety of available products.

 

[Jerrold Tiers]

Class-D is more expensive, in general, until you get to high powers, where the tendency is for it to cost less than "amplitude analog" amps. That is because "amplitude analog" amps need a lot of output devices, compared to class-D.

It is also a bit more trouble to apply "interesting" feedback schemes to Class-D, some of the sound modifying schemes used on other amps are not so easy to do with class-D for various reasons.

And, often clipping is not as 'forgiving" with class-D. Many class-D sound pretty bad if clipped.

 

[seanm]

My feeling is there has to be SOMETHING, or I would think Class D would have virtually rendered class A/B obsolete by now?

I don't think class D will take over in the short term. First, class A/B is well understood and easy to design. Class D is more complicated.

And in the guitar world, it is class A or nothing. You will not convince the average guitar player otherwise.

 

[seamonkey]

Class-d is booming. It's especially showing up in battery powered applications due to it's high efficiency. It's also easier to build-in because there's less concern with heat. It does cost more and is more complex, but engineering is getting better and better at it.

 

[seamonkey]

I don't think class D will take over in the short term. First, class A/B is well understood and easy to design. Class D is more complicated.

And in the guitar world, it is class A or nothing. You will not convince the average guitar player otherwise.

Agreed - not in the short term.

But as far as PA and Keyboard, and well acoustic instruments and acoustic guitars - I don't know - class-d could get really popular.

 

[Passinwind]

And in the guitar world, it is class A or nothing. You will not convince the average guitar player otherwise.

The average guitar player doesn't even realize that their favorite amps are mostly Class A/B, not really Class A though.

 

[A9X]

The average guitar player doesn't even realize that their favorite amps are mostly Class A/B, not really Class A though.

I was gonna say. Anything above 5W, except for a few rare boutique units, are definitely AB.

 

[A9X]

I would love to believe a Class D power amp can sound as good as a Class A/B one. I know it's possible for them to sound acceptably close regarding frequency response and distortion.

I would like to know whether or not a class D amp's damping factor can be as high as that of a good A/B amp, especially in these light-weight designs. Although this has probably been beaten to death before on TB (as I dodge the thrown vegetables and lead sled power transformers...), a clear answer to this would be helpful.

I have modules from Tripath, 41Hz (several), UcD and LC Audio. None have an output Z that isn't mitigated by the connectors and cable used, ie not significant.

As per sound quality, in a far more rigorous test than bass guitar on stage at 100+dB, ie driving my STAX electret cans, the UcD modules are exceptional, and better than any AB module I have or have heard.

Jerrold makes a comment earlier about feedback tonal variations that are possible to implement in AB are difficult in D. That's true, but I have seen a solution, though am not convinced of it's performance yet. Info relayed by a trusted engineer mate, but no direct personal experience as of today.

If you are comparing different solid state amps, and they sound different, there are two primary causes to consider:

1. Differences in gain, meaning that one amp is playing louder when you test it, regardless of which amp has the higher power rating.

2. Differences in frequency response, e.g., due to preamp voicing.

One approach would be to measure the preamp voicing of the the three amps, perhaps using my free real-time analyzer program.

This is correct. Like is not being compared to like here, and all sorts of assumptions are being made because of it.

 

[warwickhunt]

This is correct. Like is not being compared to like here, and all sorts of assumptions are being made because of it.

I totally agree and I am aware that I am talking about a bassist (or bassists) standing in front of a cab(s) with nothing but their ears (possibly trouser legs) to 'test' my comment about the potential differences on SPL/thump from a selection of amps with varying means of generating that tone... However, ultimately that is all that matters to me, 'what I can hear or feel'. It isn't scientific and I can't measure it, my question is generated purely from a users point of view standing in front of his rig.

Purely for our own savage amusement (isn't that what this is all about, entertainment) and rightly or wrongly, myself and several other bassists with approx 70 years experience between us, ranging from Bluegrass through to Rock, are intending running a selection of amps and cabs into each other (inc' the suggestion of the pre of one amp into the power of a second) to see if we can identify what 'we' like and if there are any perceptible anomalies. This will be conducted with absolute disregard for scientific fact (I'm not thumbing my nose at any of the respected knowledgeable personages on this or any other forum) purely to see if we can identify any audible similarities/differences.

By all means I'd appreciate comments with regard to what we intend doing but there is little point shooting us down for ignoring science. We are simply going to put into practice what has been suggested and commented upon in this thread. We aren't going to drag in any piece of equipment that happens to be lying around or belonging to our friends, this will all be equipment that is owned by us and in regular use. Sorry no insult intended but this is hardly Tom Bowlus territory! The equipment will be:

1 x Thunderfunk head
1 x Tech Blackcat head
1 x Ashdown Superfly
1 x H&K Bassbase 250
1 x SWR 750x head
1 x Genz Benz 750
1 x Acoustic Image
1 x Tech Neo 6x10
1 x SWR Goliath 4x10
1 x SWR Son of Bertha 1x15
2 x Schroeder 21012
1 x JPJ self-build 1x12
1 x Tech 21 SABBDI
1 x EBS Microbass II
1 x BBE Acoutimax

 

[A9X]

I totally agree and I am aware that I am talking about a bassist (or bassists) standing in front of a cab(s) with nothing but their ears (possibly trouser legs) to 'test' my comment about the potential differences on SPL/thump from a selection of amps with varying means of generating that tone... However, ultimately that is all that matters to me, 'what I can hear or feel'. It isn't scientific and I can't measure it, my question is generated purely from a users point of view standing in front of his rig.

I have no issue with anyone trying an amp and saying, "it sounded like......to me". What I don't like so much is saying this amp sounded this way because of this or that technology involved in it's design, with no possible way of seperating out what may actually be the cause of said differences.

Purely for our own savage amusement (isn't that what this is all about, entertainment) and rightly or wrongly, myself and several other bassists with approx 70 years experience between us, ranging from Bluegrass through to Rock, are intending running a selection of amps and cabs into each other (inc' the suggestion of the pre of one amp into the power of a second) to see if we can identify what 'we' like and if there are any perceptible anomalies. This will be conducted with absolute disregard for scientific fact (I'm not thumbing my nose at any of the respected knowledgeable personages on this or any other forum) purely to see if we can identify any audible similarities/differences.

Sounds like a lot of fun.

 

[warwickhunt]

I have no issue with anyone trying an amp and saying, "it sounded like......to me". What I don't like so much is saying this amp sounded this way because of this or that technology involved in it's design, with no possible way of seperating out what may actually be the cause of said differences.

Agreed, we have no intention of making spurious claims about why something is doing... something. It will simply be a matter of reporting what we hear.

Sounds like a lot of fun. The only thing I'd like to suggest is have someone normalise all the gains, as the unit that's only slightly, and probably imperceptably so will be the one deemed 'better'. I learnt long ago that human ears couldn't be trusted for value measurements, ie can't reliably determine 'louder' for instance, especially wehn my measuring apparatus said otherwise. Subjective opinions on tonal quality etc are prefernces.

I see where you are coming from, a slight adjustment one way or the other of input gain on a valve pre amped model could make a big difference! Unfortunately we don't have the facility to accurately 'normalise' the gains. I think 3 pairs of ears and if need be a couple of blindfolds may be employed but that's about it as far as apparatus is concerned. Point duly noted though, thanks.

 

[A9X]

I see where you are coming from, a slight adjustment one way or the other of input gain on a valve pre amped model could make a big difference! Unfortunately we don't have the facility to accurately 'normalise' the gains. I think 3 pairs of ears and if need be a couple of blindfolds may be employed but that's about it as far as apparatus is concerned. Point duly noted though, thanks.

You must have been typing as I realised there were multiple cabs involved too, which would make it impossible to do. Hence my edited post above.

 

[spiritbass]

Technical discussions aside, I had a real-world experience a few weeks ago. I was playing with a drummer and Hammond B-3 player with my Series III Clarus. I had to turn the Clarus ALL the way up to hang in there. This amplifier is in the general power range of the Thunderfunk 420. I've been bringing the 420 ever since (the Clarus found another home). Both were driving my trusty Tri-112L. There is just no comparison in the real world output between these two particular designs. On paper sure. And yes, a watt is a watt. I too used to own an iAMP 800, but it moved to Texas. I'm sticking with good old class AB and a traditional linear power supply for now, anyway. My ears are not closed on this debate, though. I'd would love to hear the much-touted LM-II, but I'm not in a rush to 'change horses' or drive to St. Louis to test drive the Markbass. Now, back to the debate...

Ken

 

[KJung]

Technical discussions aside, I had a real-world experience a few weeks ago. I was playing with a drummer and Hammond B-3 player with my Series III Clarus. I had to turn the Clarus ALL the way up to hang in there. This amplifier is in the general power range of the Thunderfunk 420. I've been bringing the 420 ever since (the Clarus found another home). Both were driving my trusty Tri-112L. There is just no comparison in the real world between these two particular designs. On paper sure. And yes, a watt is a watt. I too used to own an iAMP 800, but it moved to Texas. I'm sticking with good old class AB and a traditional linear power supply for now, anyway. My ears are not closed on this debate, though. I'd would love to hear the much-touted LM-II, but I'm not in a rush to change horses or drive to St. Louis to do so. Now, back to the debate...

Ken

Per some of the really good posts above (A9X, etc), I don't think you can accurately apportion the 'cause' of the differences you are hearing between the TF and Clarus to one specific component.

I found my TF to blow away my Focus on the gig.. just as loud, more punchy, etc. However, many have commented that the seeming lack of punch of the Focus/Clarus has to do with the voicing and gain of the preamp. Many have commented that the Focus SA (the power section only) with a preamp designed for bass guitar, just KILLS.

In my A/Bing of my TF and LMII (both about the same wattage), I (and others) find the LMII, if anything, fuller and louder than the TF, although very close. So, one is class A/B with a traditional power supply, and one is class A/B with a switching supply.... which is 'better'?

So, again, one of the things I've learned on this site over the last couple years, is that it's almost impossible to attribute tone to one specific design feature of the amp. I find my 550 watt Thunderfunk much fuller, punchier and just as loud as my 1200 watt Walter Woods. So... class D / switching sucks... right I find my 7 pound Markbass SD800 to outperform my 40 pound Glock HeartRock in almost every way... so, heavy toriodal power supplies suck

Just like with a bass guitar... it's all about how the pieces are put together IMO and IME.

 

[Handyman]

I have modules from Tripath, 41Hz (several), UcD and LC Audio. None have an output Z that isn't mitigated by the connectors and cable used, ie not significant.

As per sound quality, in a far more rigorous test than bass guitar on stage at 100+dB, ie driving my STAX electret cans, the UcD modules are exceptional, and better than any AB module I have or have heard.

Technically, the Tripath products aren't class D amplifiers. Class D amps use a fairly simple PWM scheme to drive the output FETs, where the Tripath products use a more sophisticated spread spectrum approach which results in much better high frequency response.

I know a guy that built up an audio amplifier for himself out of some of the higher power Class-T Tripath modules, and the thing had a frequency response that was flat out too 200kHz. No, 200kHz was not a typo. The thing was also over 85% efficient too. The small size of the heat sinks on the output FETs was downright remarkable.

Anyway, I guess my point is that modern mixed signal amplifiers are pretty amazing beasts, if they're done right.

 

[spiritbass]

Ken - I have to agree with you that for electric bass, the preamp on the AI amps is the weak point. I didn't try running a different preamp into the power section of the AI because I had absolutely no intention of buying a separate pre to run it with. It was a fine little utility amp for myself and my son for a while. My little example was not about tone, it was about being heard. The Clarus was barely keeping up, whereas the Thunderfunk was basically loafing. I also am in agreement with yours and other's statements about satisfactory output depends on the engineering choices. And yes, I am intrigued by the LM-II. A big part of my restraint from checking it out at this point is that my GAS funds are going toward a couple of cool custom basses. The 420 slung over my 51-year old shoulder in its rackbag is hefty, but I don't have to carry it too far!

Peace,
Ken

 

[KJung]

Ken - I have to agree with you that for electric bass, the preamp on the AI amps is the weak point. I didn't try running a different preamp into the power section of the AI because I had absolutely no intention of buying a separate pre to run it with. It was a fine little utility amp for myself and my son for a while. My little example was not about tone, it was about being heard. The Clarus was barely keeping up, whereas the Thunderfunk was basically loafing. I also am in agreement with yours and other's statements about satisfactory output depends on the engineering choices. And yes, I am intrigued by the LM-II. A big part of my restraint from checking it out at this point is that my GAS funds are going toward a couple of cool custom basses. The 420 slung over my 51-year old shoulder in its rackbag is hefty, but I don't have to carry it too far!

Peace,
Ken

+1.. fun stuff for me to think through. I'm with you. A lot of AI users who play DB use some sort of additional small pre (like the Demeter stomp box) in front of the amp, and it sounds nice that way. For me, like you, I want one piece that sounds good (to me) without anything other than an instrument cable, a power cable, and maybe 5 to 10 seconds of minor knob twisting!

Both the Thunderfunk and the Markbass line of amps delivers that to me at this point!

 

[alexclaber]

I'd like to highlight to the European (and anywhere else with proper electricity) bassists that our higher voltage mains can supply well over 50% more power from the wall which reduces the need for large energy buffers in the power supply. This means that any difference in performance that there may be between lightweight and lead sled power amps in the US may be imperceptible over here.

So, again, one of the things I've learned on this site over the last couple years, is that it's almost impossible to attribute tone to one specific design feature of the amp. I find my 550 watt Thunderfunk much fuller, punchier and just as loud as my 1200 watt Walter Woods. So... class D / switching sucks... right I find my 7 pound Markbass SD800 to outperform my 40 pound Glock HeartRock in almost every way... so, heavy toriodal power supplies suck

Just like with a bass guitar... it's all about how the pieces are put together IMO and IME.

Exactly!

Alex

 

[A9X]

Technically, the Tripath products aren't class D amplifiers. Class D amps use a fairly simple PWM scheme to drive the output FETs, where the Tripath products use a more sophisticated spread spectrum approach which results in much better high frequency response.

I know a guy that built up an audio amplifier for himself out of some of the higher power Class-T Tripath modules, and the thing had a frequency response that was flat out too 200kHz. No, 200kHz was not a typo. The thing was also over 85% efficient too. The small size of the heat sinks on the output FETs was downright remarkable.

Anyway, I guess my point is that modern mixed signal amplifiers are pretty amazing beasts, if they're done right.

You're absolutely correct, and I know PWM is analog, but for as long s I can recall, class D has always been loosely applied to anything that used some sort of switching scheme a la PWM.

The Hypex modules in particular are excellent, but not quite to the state of superb tube or class A for reproductive audio. At least not what I have here. Pity as the heatsinks alone on my class A amps cost more than a UCD400, but I have one of those for sub 100Hz duties.