Who will survive? One last table til I die.

I think I'm going to hit myself in the head with a hammer...

"OTL
Let’s look at the Transcendent T8 as an example. It uses 8, EL509 tubes in push-pull. Each 509 has a plate impedance of about 150 ohms. 150 ÷8 = 18.75 ohms. This is unacceptable. Negative feedback is employed to achieve proper performance. The amplifier uses 33 dB of negative feedback which reduces the output impedance to 0.4 ohm thereby achieving outstanding woofer control and the ability to drive 4 ohm speakers. This specification was verified by Stereophile when they reviewed the amplifier."

Direct quote from the link in my previous post.

Now here is a quote from Raul:

"... The output impedance in the tubes amplifiers, usually, goes from 0.5 to 3 OHms ( high one ) and the output impedance in the SS goes from 0.02 to 0.5 OHms ( very low one..."

Consequently, given the range that Raul has given, there is a tube amp with output impedance in the range of SS. If the Transcendent amp is an uncontrollable equalizer so is a ss amp.
Others can see that Raul conitnues to move the goal post.

Pardon me while I continue to bang my head...

As I stated above before you make major changes in your system to obtain full spectrum frequency balance you should study what a real frequency curve of a real speaker operating into a real room (not an anechoic chamber)looks like. Moreover you need to examine what empahasis the human ear puts on the frequency spectrum.

Raul, I would refer you to the David Berning website, in the White Papers section, where amplifier transfer characteristics are discussed.

You may know that the "load line" of a given amplification device in an amplifier defines how it responds to the loads presented to it by the speaker(load) and how well it will control it directly and without feedback.

In my Berning amplifier, the load line is about 1.8 ohms, and it operates with no feedback, and is globally DC stabilized(something you seemed to think could only be in SS amps, and not be achieved with tube circuits, but is a feature of the David Berning ZOTL circuit). However, by using the much larger "effective turns ratio" that is provided by the unique ZOTL impedance conversion circuit, much more effective control of the speaker load by the triode is possible, than would ever be possible using any output transformer or traditional OTL ciruits. In fact, with the load line that is in my amplifier, according to the David Berning "White Paper",

"In an audio application, the tube behaves as if it is driving a 4k ohm speaker (the impedance conversion ratio goes as the square of the turns ratio), and the speaker acts and sounds as if it is being driven by a 0.6 ohm triode."

And this, with the use of ZERO FEEDBACK. The natural load line of the triode is sufficient to produce this, when using the ZOTL impedance converter design. So that all the linear transfer characteristics of the triode are preserved, and full control of the load is realized, while exceeding the capability(and eliminating any of the drawbacks) of any output transformers.

So, as you can see, the use of this design allows both a low output impedance AND zero feedback, and at the same time eliminates all the saturation problems and parasitic capacitances of typical output transformers in audio applications, and still allows the use of a single triode(no parallel tubes like traditional OTL) to control the speaker accurately and in conditions of shifting speaker impedances(within reason), based on its inherent transfer characteristics(load line)in conjunction with the Berning ZOTL impedance converter.

While David does give credence to your concerns about shifting impedances causing frequency response problems in certain amplifiers, it is shown that this amplifier circuit is not adversely affected by the things that you mention, and the load lines in the ZOTL circuit are very close to what would be expected from some MOSFET transistor amplifiers(without feedback). However, the sonic attributes of the triodes are preserved, and gives what might be called "the best of both worlds", as the control and speed are very much like solid state, and the transparency, tone, and harmonic qualities are all tube.

So, here we have a tube amp with a single output triode(per channel), no audio output transformers, no feedback, an effective output impedance of about 0.6 ohms, DC coupled and global DC stabilization, bandwith from 2Hz - 500kHz, high-speed switching power supply, RF-frequency tube heating, noise less than -100db, choke loading, DC powered, auto-biasing, brownout protection, and can even be turned on without any speaker attached without damage(just like a SS amp can), and weighs 5 pounds.

And best of all, it sounds like real music when you use it with a good speaker. It doesn't sound like most tube amps, and it doesn't sound like most SS amps. It sounds like the best of both.

Now, by anybody's numbers, a 1:13 ratio(damping factor 13) of output impedance to speaker impedance is going to be well within 1db(and probably within 0.5db) in frequency response variation over the audio range as long as a nominal 8 ohm speaker is used. Now, if you want to drive Apogee Scintilla's <1 ohm load with it, I'll agree that I cannot do it with this amp effectively. For the speakers that are intended for this amp, it will control them admirably and exhibit a quite flat response, and be musical.

Whew! I'm tired, and had about enough of this.

Regards,
Twl

Suttlaw,
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For an incredible line of tubed pre-amps, check out Supratek (suptratek.biz) from Australia. The Cortese model is just phenomenal and an incredible Value in the $ 5,000.00 range.
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Raul has found a ghost writer.
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Raul, why is it that you do not list your system or respond to people when they ask you what equipment you are using ?
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TWL: I have in hand the Stereophile review on a Berning EA-2101 amplifier. Here are the output impedance at the 8 Ohms tap: 3 Ohms at 20 Hz and 1 kHz and 4 Ohms at 20 kHz. At the 4 Ohms tap ( 3.55 Ohms ): 1.5 Ohms and 2.1 Ohms , respectively.

Now, with a constant 8 Ohms impedance the deviation response is at 1 db in the high frecuencies and with 4 Ohms 1.5 db. This is with a constant load impedance, it is for sure that with a real speaker impedance the errors will be higher and dramatic changes to our ears.
So, your post don't help to " cure " the uncontrolled equalizer effect.

TWL, as you know no body can change ( till to now ) the physics laws. I agree, like you, that the Berning design is a good one, but is not enough on that subject, it is still short on it.

Regards and enjoy the music.
Raul.

Dear gregadd: *** " Others can see that Raul conitnues to move the goal post. " ****

Wich's your point ?. What are you trying to say?. That example don't tell the whole history because that amp needs 33 db of global negative feedback that introduce very bad effects and for other way we can't see the Stereophile diagram response on that subject. BTW this amp is in the high level of the " permited " output impedance.

Gregadd be serious and mature. Don't try to deffend what it can't be deffended. Don't try that this serious subject fall in a witch hunting or a words game.

Your link put everything and everyone in the right " place ". What do you want? , you don't have a point till to now. Remember that this is not a contest. Come on Gregadd use your experience intelligence and don't try to find a point where does not exist one.

Regards and enjoy the music.
Raul.