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What is the compromise in implementing the ZEROs

Easy, you can hear/do this for yourself. On any amp that has no problem driving whatever speaker without the Zero’s. Then put the Zero’s in and you will then hear the compromises they make.
But they do allow amps that are not driving the speaker well, to be able to do so, but I’d rather change the amp for the right one for those speakers, as these Zero’s are not cheap, for what to me is a band-aid fix.

Cheers George

Hey Ralph. Here's my chance to zero in now that you've chimed in. My experience has been that there's no free lunch. What is the compromise in implementing the ZEROs? It seems you would lose extension one way or another, no?

Because the ZERO does not have to block DC, and also because you need an amplifier that already has a low output impedance, the result is a very low turns ratio with low distributed capacitance. Translated that means it has a very wide bandwidth- wider than our amps (which is quite a bit different from the usual output transformer which is often the limiting factor in tube amplifier frequency response); about 2Hz to 2MHz!!

So, 'no', you don't loose any bandwidth at all. What you loose is a bit of voltage gain as the transformer steps down the voltage.

How it seems to work is if the ZERO creates sonic compromise, you probably don't need it.

I have never seen it as a band-aid as George puts it; prior to the ZERO we actually made a similar product called the Z-Music autoformer, which did pretty much the same thing (ours also allowed for one ohm operation, allowing Steven Stone in a TAS review 25 years ago to have a set of our MA-1s drive a set of Apogee Full Range loudspeakers with very convincing results to my ears).

The simple fact is that four ohms is not good for **any** amplifier made regardless of the technology, and this is easy to see in the amplifier's specifications. Distortion is always higher, and the distortion is of a type that is easily heard as brightness and hardness. This is why Steve McCormick sent a letter to Paul Speltz (who makes the ZERO) stating that his amps sound better driving 4 ohms through the ZERO rather than directly. The amp has lower distortion and you can hear it right away.

That's not a band-aid so much as its a fix for a problem; the problem being speakers that cause amps to make increased audible distortion.

This being high end audio and all, distortion **bad**, music **good**!

Hypex. Ncore vs. anything in a blind test. Chose your power supply but the most accurate is Hypex Ncore. Most dynamic too. Damping factor for transients.

The simple fact is that four ohms is not good for **any** amplifier made regardless of the technology, and this is easy to see in the amplifier's specifications. Distortion is always higher, and the distortion is of a type that is easily heard as brightness and hardness. This is why Steve McCormick sent a letter to Paul Speltz (who makes the ZERO) stating that his amps sound better driving 4 ohms through the ZERO rather than directly. The amp has lower distortion and you can hear it right away.

George; I have nothing but respect for your technological expertise. All I have is my empirical experience. My ARC Ref150se sounds lifeless and dull with one set of speaker cables mated to my DeVore O/93's unless I use the 12 ohm taps and yet with another set of speaker cables (lower gauge, completely different design) my DeVores sound hard and bright unless I use the 4 ohm taps and with the 4 ohm taps the sound is magical. Can you unequivocally state that using the 4 ohm taps on any tube amp, including my ARC Ref150se, ipso facto results in brightness and hardness? ARC in it's owners manual states that the consumer should try 4, 8. and 12 and judge for oneself. I have to wonder, why would such a reputable amp manufacturer even offer the option if it were such a compromise? And what might account for my experience described above other than accusing me of having bad ears?

@fsonicsmith, I think you are addressing me, not George since the quote is mine.

The DeVore is not a four ohm speaker; as far as their website is concerned, they don't make any. But it works best on your four-ohm taps. That is quite a bit different from the speaker actually being four ohms. It simply means that combination works best for you- and as you noticed, the speaker cable is a bit critical in the overall scheme of things.

Can you unequivocally state that using the 4 ohm taps on any tube amp, including my ARC Ref150se, ipso facto results in brightness and hardness?

Not- at all, and if you got the impression I said that, I didn't. What I did say is that the use of four ohm speakers results in higher distortion from any amp- and that the distortion is such that is perceived as brightness and hardness. There is a distinction here- you are not using a 4 ohm speaker.

Using the four ohm tap gives you the lowest output impedance available from the amp and for some reason that works. FWIW, usually you loose some bandwidth using the 4 ohm tap; IME its usually in the bottom octave.