So this is a "perfect" amp? But innovative?

[The golden mean]

Got a news mail and got a deja vu feeling of having read some similar articles in the past where some "revolutionary" products are said to be "the one and only". Perhapes it has to be this way if we want journalists to tell us (preach) that there are some real expencive products that are going to change our lives if we have got the money and that the new era of perfect fidelity has now reached us? BTW I built a pair of mono blocks without emitter resistors som 25 years ago. I might be a bit cynical but can´t help to ask myself if my not perfect amps are fooling me to enjoy music?

A quote from Jonathan Valin: " I’m told by those who know that the elimination of emitter resistors is a genuine innovation in solid-state design"


But here´s the article:

Technical Brain TBP-Zero EX Amp & TBC-Zero EX Preamp (TAS 213) | AVguide.

[lineup]

In solid-state audio, it is emitter resistors that prevent the injection of this energy from the amplifier into the speakers. In order to protect an amplifier from thermal runaway, emitter resistors restrain the flow of current by using negative feedback, while compensating for the differences in operating current between power transistors. Since the early years of transistor amplifiers, their use has amounted to a necessary evil.

The most important technological innovation in Technical Brain circuits is the elimination of these emitter resistors and the development of a bias-current control-circuit without time delay (patented in Japan) that has made their elimination possible.

It is not much to give attention to.
Emitter resistors are everywhere. Not only in output stage.
They are the easy way to control current flow.
To remove emitter resistors you need to complicate and this can potentially disturb the amplifier more than emitter resistors does.

[karmik]

Also, it's just a marketing move. I'm a complete neophyte but i've been reading audio magazines since i was 17 (and i'm 27 now) and i've long learned to just ignore any qualitative claim made in them that is not supported by hard data (measurements etc.).

[janneman]

Not only that, but in another thread here recently it was found that the removal of these Re's has been used decades ago.

jan didden

[dadod]

Sinclair amps from 1972 Z30 and Z50. No output BJTs emitter resistors.

[digits]

For me and the other non-engineers, the emiter resistor acts like a sort of valve which makes the output transistors all work equaly hard (within the variation of the resistors)???

Would the average class AB be toast if one were to remove these, do we just put these in because of habbit? What dictates the values?

[jaycee]

They also help with thermal stability. If you take them out, the amp will often be thermally unstable and run away. Sinclair things were, after all, famous for blowing up

[Bigun]

Originally Posted by lineup

It is not much to give attention to.
Emitter resistors are everywhere. Not only in output stage.
They are the easy way to control current flow.
To remove emitter resistors you need to complicate and this can potentially disturb the amplifier more than emitter resistors does.

Agreed.

There are already more than enough great sounding amps for DIY, we don't really need any more that offer diminishing returns for the effort and expense.

[dadod]

Originally Posted by jaycee

They also help with thermal stability. If you take them out, the amp will often be thermally unstable and run away. Sinclair things were, after all, famous for blowing up

I've got one running for 40 years (almost) with no problem. It is DIY with 2n3055 and no thermal compensation as per original schematic. The sound is still quite good.
dado

[jaycee]

Originally Posted by dadod

I've got one running for 40 years (almost) with no problem. It is DIY with 2n3055 and no thermal compensation as per original schematic. The sound is still quite good.
dado

At 40 years old they are probably the old "hometaxial" 2N3055 devices. These could be used without emitter resistors as the emitter already had some considerable resistance. If you tried it with a modern "epitaxial" 2N3055, it would runaway and blow up.