Tube Amp for Martin Logan Speakers

^Let's start with these links 1st:

"If sound quality is your goal, it will be best served by a speaker that is 8 ohms or more, all other things being equal." If you want greater **sound pressure** there is a slight argument for 4 ohms if you have a transistor amp. IOW, there is no argument in support of four ohm speakers in high end audio.

FWIW these days there is little argument for 4 ohm speakers in high end audio. This because regardless of the amplifier technology (transistor, tube or class D), the amplifier will sound better and perform better on higher impedances. Of course, if you are unconcerned about sound quality, and more interested in sound pressure, than 4 ohm speakers will be more attractive if you also own a solid state amplifier. The other argument against 4 ohms is the speaker cable- they are extremely critical for best results on 4 ohms, while at 16 ohms they are not nearly so. Making a speaker to be higher impedance, all other things being equal, is an easy way to make the speaker appear that it is smoother with greater detail, always a desirable combination.
Atmasphere (Threads | Answers | This Thread)


http://forum.audiogon.com/cgi-bin/fr.pl?
cspkr&1356668050&openusid&zzAtmasphere&4&5#Atmasphere

The point is; speaker designers have to make many considerations when designing speakers and sometimes for the greater good compromises have to be made, and rarely is it so black and white that a design choice is either good or bad. Even what might appear to be a less than ideal choice might actually have some positive attributes.

BTW, I don't agree with your assessment of George either. Like most of us here, he's shared his experience and his points and advice seem to have merit.

"Im shocked at how much tube monoblocks go for new."

Its a reasonable response I think.

Especially in the case of low power tube amps like SETs costing 5 digits. These use only a few tubes, and often claim to keep circuitry simple towards the end of good sound. Granted, high quality parts cost more and there is some intellectual value associated with design, but nothing hugely innovative going on here.

OF course, more tube power = more tubes, so understandable how cost goes up in that case.

If you buy into the concept that a couple of watts can be made better than if more, then that helps with the justification. But then it often requires very expensive and large speakers to complete the deal for TAS.

I tend to think you get a better deal with quantity, including watts, and those additional watts are not as detrimental as some purists might portray them to be on the grand scale of all the things that go into good sound, especially when modern SS amps like Class Ds are more efficient and cost effective than ever before.

03-21-14: Atmasphere:George, you are a troll. Your comments are unwarranted, without merit and uncalled for.

There is only one reason for you calling me a troll, that is you have to stick up for the Zero Transformers, because they are the only way your OTL's will drive many semi difficult speaker loads that are out there.

And I stand by my comments about them, they are a bandaid fix for amps that cannot drive difficult loads, and the owner is better off getting the right amp, or an easier load impedance speaker.

I have actually praised your OTL amps, when they are mated to the right speaker, but to put a Zero Transformer on them is just defeating the fact they are OTL in the first place.
http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1304533364&openfrom&23&4#23

Then your suggestion of putting a Zero on a tube amp that already has an output transformer is just plain stupid, instead of getting the right amp or speakers. And then to infer to putting them on a good quality solid state amp is just ****************

Cheers George

Atamsphere, here's another link:

12-28-09: Audiokinesis
Unsound, obviously I should have
made it clear which part of my
response was about things an owner
of existing speakers could do, and
which referred to something that
would have to be done during the
design stage.

In my opinion using an autoformer is
something a speaker owner would do
to make his speakers more compatible
with OTL amps.

If we're just looking at the design
stage, then yes it is easier to
smooth the impedance curve by
lowering it. But if the end goal is
compatibility with OTL amps, for
example, lowering the impedance
curve can be counter-productive.
Some of the design choices that lead
to a medium to high, and smooth,
impedance curve need to be made
before the crossover design stage.
For example, I can't expect to build
a 2.5-way system using two 8-ohm
6" woofers and end up with an
OTL-friendly design.
Audiokinesis (Threads | Answers |
This Thread

I'll try to find more as my time
permits.

Ralph, George and Mapman .... I have no dog in this fight, but I have read the several posts and would like to suggest that much of what everyone has written has merit. Let me suggest to my fellow hobbyists that you aren't really disagreeing with each other, but you are talking past each other and just getting frustrated.

I think Ralph would agree, and has said as much in other threads, that a high'ish output impedance amp might not mesh well with a low'ish sensitivity speaker that has a roller coaster impedance curve. Indeed, one could expect sonic colorations as a result of the interaction between the two components behaving in according with various electrical principles, e.g., Ohm's Law.

That may be why Ralph says that an autoformer might aleviate some aspects of the "non-optimal" (whatever that means) impedance match in such cases. George, I gather your point is that sticking an autoformer into the circuit is just a "patch" for an underlying issue that maybe shouldn't be an issue in the first place.

If that is a fair restatement of your view, I too happen to be biased (pun intended) against sticking gizmos into the circuit based on a few anecdotal experiences of my own. In the two or three cases I put "artifacts" into the signal path, I had dismal outcomes. I am not saying one would have a similar result with autoformers. Just that I am dubious based on past experiences. And even if they work, I am not sure I would want to shoe-horn an amp and speaker together if the two components weren't a good fit in the first place. But that's just me.

If we can all agree that I fairly restated the dilemna, let me suggest that perhaps one way to view OTL amps is kinda like SETs. That is there are audiophiles who swear by SET amps. But, ... they recognized as a threshold matter that a SET amp will not be a good match with a low sensitivity speaker that has a roller coaster impedance curve. That's why some have suggested matching a speaker like a Daedalus with this type of amp. I suspect that an OTL would perform beautifully being matched with a Daedalus speaker.

Hey ... to a lesser extent, I've got amp/speaker issues too. My ARC Ref 150 amp is driving Paradigm Signature 8 v3 speakers. This is **not** a match made in heaven. The S8s have wild impedance and phase angle curves. Paradigm advises that the S8s should be driven by a high-power/high current SS amp. Oooopss. I blundered. But not that much. I've found some sonic solitude by using the 4 ohm taps (as of late), which seem to have smoothed out the rocky impedance road and improved bass response. Having a 1040 joule power supply "don't" [sic] hurt either.

In short, if everyone takes a minute to re-read the other folks' posts, I think you'll wind-up agreeing with much of what has been written.

IMHO.

Btw, I'm rocking with the Best of Pat Benatar CD. Having a ball!! :) :)