Dx Blame ES .... based into the Blameless, i am trying a new amplifier

[maxlorenz]

What about installing the output in the middle of the PCB?, because there is a big track there, just where you wrote "remove this one" in yellow letters. This way we respect simetry and a certain distance between power rails, input section, output devices, and we can instal the zobel on the speaker's binding posts...just a couple of holes with a Dremel

[destroyer X]

from the output coil to the input differential transistors, and current sink.

regards,

Carlos

[tinitus]

Hi, sorry to hear the troubles

In this Dx layout I have tried to "reverse" output transistors, just to see what happened
Note that board is mounted flat on heatsink, upside down
Should fit a relatively cheap 80mm box height

Wires from supply to amp board are straight and very short

But I have had enough layout headackes even with the much simpler Dx

[wg_ski]

Originally Posted by Eva

According to the waveforms and their description in post 866, the amplifier still exhibits overshoot and slight ringing when driving a resistive load, which is the consequence of a too small phase margin. The ringing frequency is where open loop gain meets closed loop gain.

I think he may have the images reversed. The one with the overshoot is probably the resistor in parallel with the 2uf cap. The output inductor will cause that to ring, even if the waveform on the other side of the inductor is perfectly square.

If it were ringing that bad into just a resistor with a large signal input, it would sound terrible. I've heard (and built) marginally stable amps that sounded IN YOUR FACE BRIGHT and didn't ring that much into just a resistor. And the ringing frequency was a lot higher.

[destroyer X]

With ringing or without ringing it sounds lovely, almost perfect..the advantage compared with others is huge.

Of course the ringing image is the capacitor result... and this is not an usual load to power amplifiers...so, this was made to check stability, to know how much stable or how much stable it is...i have no intention to use the capacitor together my amplifiers, so, i suppose the ringing will not always be present in audio reproduction... at least, i hope so.

Waveforms, simulator results, cannot offer you a perfect idea about sonics.... my old Dx amplifier shows almost the same results watching the scope, and simulations are also not too much different, but sound quality difference is huge.... human ears, human perception, is another story.

Dx amplifier has a lot of bass when connected to real speakers, the Dx Blame ES and the ST has a lot of treble when connected to real speakers, both are electrically flat and also flat in the simulators..this shows how real things are different from theories.

This circuit is almost entirelly made by Doctor Self, the input is from Blameless and the output is also something doctor Self have used in other amplifiers.

Usually, with some very honorable exceptions, Doctor Self know much more than we know, he use to be our teacher, not the opposite.

regards,

Carlos

[destroyer X]

It looks almost the same you have started several years ago.

looks alike, certainly you have made modifications.

regards,

Carlos

[destroyer X]

this one include the minor modifications, so, it is the Dx Blame ST schematic, the stable one.

This will help you, an interim schematic while Taj is busy.

Not to complicate things...build exactly as the Dx Blame ES schematic, use the artistic view to check your construction...then, replace rail resistances by 56 ohms or 68 ohms (R17 and R22), increase Miller capacitor, from 82pf to 120 pf, or install a 47pf unit in parallel with the 82pf (C13) capacitor, remove C11 and substitute C25 by a 10pf unit, use wire jumper and short R3.

Remove output coil and zobel filter and install them in the speaker output connector, or install the shield as posted, and explained previously.

Increase your stand by bias to 4.7 to 5.5 volts and enjoy the lovely sound from this, almost perfect, audio amplifier.

regards,

Carlos

[black]

This scheme is good? and where can I find patterns amplifiers dx? with thanks

[destroyer X]

Dx amplifier thread,
Dx Precision 1
Dx HRII
Dx Trust
Dx DHR Turbo
Dx Blame ES (this thread)

All schematics, layouts, adjustment instructions and so on are in Greg Erskine home pages:

Greg's Web Site

Osciloscope paterns usually are not provided, as Dx amplifiers performs better while listening than measuring...despite they measure good too (just an accident, this does not means guarantee of good sonics)

regards,

Carlos

[black]

thanks sir carlos