OTL amplifiers

Hi!
The Zero Autoformers have another great advantage: they won't alow that amps blow out your speakers. I believe that was one of the idea's when constructing the Zero's.
I agree that results with them vary, but do try them... I'd rather invest in them (because of their universality-they work even with solid state amps!) then in speaker cables of that price. But that's just my five cents...
Cheers!

The alternative 2X setting I refer to use the white and black leads attached to the speaker binding posts and the blue and yellow leads attached to the amplifer posts. This configuration brought back the "magic" OTL sound, but resulted in a small loss on the bass side of things. If I only had one pair of ZEROs or did not have bi-wire capability I would have easily, and happily settled for this setup and accepted the loss of bass output for the improvements gained elsewhere.

Not entirely content to leave it at that however, I contacted Paul Speltz and he suggested I try a second pair in standard 2X mode on the woofers and like I said before, the results were phenomenal. The best of both worlds and then some.

I don't know why Paul doesn't promote this setup more at his website. I don't know if my results would be achieved on other speaker models, but on N.E.A.R. 50Me II loudspeakers the gains were absolutely awesome.

One method I never tried, but would be curious to hear the results of, would be to bi-wire using just one pair of ZEROs.

On the N.E.A.R.s I would use the configuration described above on the high frequencies and another alternative 2X such as brown/green or gray/green on the low frequencies. If anyone tries this, you might as well try the reverse as well, brown/green or gray/green on the highs and white/black on the lows, to see if there are any gains.

Refer to Group 2 Configurations at the ZeroImpedance.com website to see a diagram of the alternative configuration options I refer to.

I know that this bi-wire with one pair of ZEROs is an option, but for safety, please check with Paul Speltz before trying.

Dfrigovt, since much of what has been posted here is way outside the scope of what you originally requested (especially from me) and is probably very confusing, let me answer your question more directly as pertains to Atma-Sphere M-60 Mk. II.2 amps.

Advantages: high-resolution, effortless sound; extended in both directions, rich (but not syrupy) and dimensional

Disadvantages: speaker choices are more limited, unless you use a large OTL or a corrective device like the ZERO autoformer, and possibly heat (hasn't been a problem for me though)

Since there are plenty of excellent speakers out there that work well with OTL's, I don't see OTL's as being problematic in any appreciable way.

BTW, do you have a particular speaker that you would like to pair with an OTL?

Henry to answer your question, this might be a possibility if there is not a built in circuit or shut off in the event of catastrophic overload, a voltage surge from the outputs. Most OTL amps have some sort of protection circuit in the event this manisfests itself for any reason.

I see you have asked this question on another thread and no one has answered. Maybe you should talk to a dealer. I believe Jtinn is a dealer for Tenor and he should be able to answer your question. This was one of the problems with the Futterman's, it didn't have protection between amp and speaker not to mention its inherent instability when matched to the wrong load. Most of today's OTL's have addressed this problem and do have some type of protection.

Said simply in general

--OTL-s give out full power only at specific optimal load. If load drops they loose the power so the bass is weak weak weak. If impedance goes up the output peak power increases to the point that it might damage speaker. Problems with DC at the output are also added in some OTL designes.

--OTL-s are tube abusers where tubes work under its peak values and deadly deadly hot(low plate voltage and high POSITIVE gride voltage) so there is the reason of OTLs to be so hot and expect to change tubes(input tubes and power tubes together) more often than you change oil in your car. Wanna try NOS and see how it "shines"? Tubes might age differently and if OTL loosing balance it can also damage speaker so there we have a large reliability issues.

--There is a solution for OTL amps that relatively recently was in effect to implement the current transformation using solid state inverterting amps that allow tubes to work as a main amplification devices and so efficiently transofrm voltage to current to drive today's speakers. The input stages are also implemented with differential cascade using transistors since input tubes also require reverse
connection for OTL-s. Such OTL consists of differential input SS circuit, Amplification circuit(tubes PP or SE or SEPP in normal common-cathode connection) and output SS inverter. The only problem with SS inverters and drivers that someone would say that he/she's listening to SS instead of tubes. Well, these meanings are only stereotypes and in reality we're listening to the product that was designed for a specific characteristics objectively and music subjectively. The design I studied from the following page:

Hybrid OTL 150W/ch amp

Please note that japanese readers will benefit much more from that page than non-japanese since description of design is only written in japanese(figured from .jp domain he..he..).

I don't know how truthfull are the characteristics of such design as well as I don't know how this amp sounds when implemented, but my objective review just only based on schematics and characteristics makes me to conclude that this product realy should be reliable and great sounding after implementation. Moreover it runs "colder" than many of SS amplifiers and has a larger design room for larger power but certainly with sacrifice of reliability.

--Zero tube autoformer does nearly the same as SS inverter but with much greater loss, larger neg. feedback and distortions. Sorry but tubes arn't flexible enough to be as a dynamic load.

--Last thing pure tube OTLs are great with headphones.