Can tube amps give true high end bass?

There are several problems that most transistor designs face in order to play bass.

The first is, perhaps a bit counter-intuitively, that they are direct-coupled. Direct coupled amplifiers have response to DC, but when you think about it, the power supplies don't. *They* have response to some very low frequency, perhaps 1/10 cycle/second, but unless run by batteries, not full on DC. Especially at power, the result is that the amplifier can modulate the power supply rails. This results in weakened bass.

A frequency pole in the amplifier (coupling cap for example) that sets the amplifier -3db point *above* the power supply pole will alleviate that problem.

The second issue is negative feedback. Most transistor amplifiers are not very linear without it and so employ a fair amount to work. At low frequencies negative feedback in addition to reducing distortion also seem to compress dynamic impact.

The result: big transistor amps that cannot play bass. Sure, they have 'punch' as the feedback has left them unable to create low frequency definition. So what you will hear in a tube amp that is built right is: Impact, bass definition, and a subtle thing that is always the first to go when things go wrong: bass ambience.

Enjoy!

Damping factor does not play much of a role in the sound of a speaker, previous posts notwithstanding! In fact damping factor is really a spec that gets touted a lot, but would seem to be mythological in its effects.

Damping factor is a means of expressing the output impedance of an amplifier. It is true that as the output impedance of the amp gets closer to the load impedance, that distortion rises, but the idea that the amp 'looses control' of the speaker is a myth, really a sort of chicken and egg thing.

In a conventional speaker, the voice coil requires a certain amount of power in order to displace the speaker. Any amp, regardless of its 'damping factor' that can make the power can displace the cone the same amount. At any and *ALL* cone positions that are possible, the cone will be in that position *because of the power from the amplifier directing it to that position*.

Note also that all bass waveforms (where 'damping factor' is touted as an issue) are real-world mathematical functions, and therefore continuous in nature. The are no worries about 'stopping' and 'starting'- unless you listen to some very weird, amusical stuff that no-body has made up yet :)

Most speakers if heavily damped will in fact not be able to reproduce the bass waveform. This is one of the reasons that high damping factor amplifiers tend to be bass shy, while at the same time having a sort of 'punch' but being otherwise bereft of bass definition and tone. Problematic, as amplifiers with a high output impedance can on some speakers fail to cut power in the frequency band where the speaker/cabinet system develops resonance.

How is this solved? It turns out that there are 2 paradigms of design, test and measurement in competition in the world of audio today. *IF* you mix equipment from one paradigm with that of the other, you will have a mismatch- it will not work right. see:

http://www.atma-sphere.com/papers/paradigm_paper2.html

for a more in-depth explanation of the differences in these paradigms.

BTW there are tube amps with full power to 1Hz and able to reproduce 20Hz square waves with no measurable tilt. This bandwidth has nothing to do with power or output impedance FWIW.

Audiobb, I play heavy metal too and I also have a few friends in the heavy metal world and I opened for Therion when they toured here a couple of years ago. The start and stop of a Kick drum is *way* too slow for any sort of stop and start that might actually be a 'damping factor' phemon! If you look at a bass drum waveform, you will see that even in a fast double bass passage, the waveform dies out as the kicker pedal is damping the waveform. Speakers are a whole lot faster than that: even a 15" has bandwidth to 500-800Hz. The bass drum (actually a typical area where 'damping factor' is brought up) is a red herring.

Jmaldonado's comment about bass extension is non-sensical, although I have to guess that it is only based on his experience. So I will share an experience of our own:

Some years back we used the Snell Model B for our main system. The speaker is full range, and was easily driven by our smaller M-60, although it was only 89 db. We went through 4 sets of woofers before Snell replaced the woofers with a re-engineered set that was more durable. We were not damaging the voice coils- the spider part of the suspension was failing, due to the excursions we were putting the speaker through (we like to play stuff with impressive bass tracks, as with 1 Hz full power in our amps, the bass we get is a strong point in our products). Snell told us that they had the same problem with mastering houses that were doing lots of dance tracks with heavy bass (we were playing that sort of material too)- see http://www.atma-sphere.com/awards/bya/index.html
for some of the discography.

So tube amps can put as much excursion on a speaker cone as a transistor amp, FWIW. In our case, in repeated demos with transistor amps, I have yet to see one that has proper bass extension. So while I accept that transistor amps can play bass, I do not accept that they can do it any better than a proper tube amp.

Audiobb, This is an interesting speaker- it seems like it has a dual woofer system, but apparently the second woofer is on a different circuit.

So that would seem to make all the circuits 8 ohms. I would check with Silverline on this to be sure.

Asking an amp manufacturer like me what amp they would use seems to me a loaded question- of course I recommend my own gear :). Alan's speakers have always worked well with our stuff. He invited us to show with him at CES one year (in fact on another year we did have equipment in his room) but some nasty events that some 'goners may remember intervened.

My feeling is that whatever amp you get, I would be careful about crossing everything over. My own experience with electronic crossovers is that you spend a lot of time getting things to blend- often never quite getting there. Using the same type of amp on each part of the system helps, but you can still run into difficulties. At any rate, it sounds ambitious- good luck with it!

Thanks!