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

[destroyer X]

The output enormous inductor was because a huge overshot in the 10 Khz square wave.

regards,

Carlos

[destroyer X]

recording using Panasonic electret condenser microphone cartridge...the acoustic conditions were not good, a normal room, a bedroom, a computer and not carpet or absortion material, only a small curtain...the room ressonance is 400 hertz....my home ressonance (entire home, door opened) is 240 hertz

YouTube - Dx Blame ES, Christmas day test II

regards,

Carlos

[destroyer X]

piece of aluminium, around 2 thirds of an inch side.

Heat is small there, this is for stability, thermal stability, to avoid transistor to change parameters...current there is not so big, so power there is very small.

VAS current is around 5 miliamps and rms voltage, audio swing, from colector to emitter is around 20 volts (RMS)

regards,

Carlos

[BV]

Carlos,
output Boucherot cell is in wrong place (schematic in post 100), it must be direct at output, before ouput inductor..And 15uH is very , very much. And try to remove 10n and 22pf capacitors..

[destroyer X]

2.2uf capacitive loads.

The amplifier was better into the scope this way..read the entire thread, this was mentioned earlier.

Done intentionally, on purpose, so, was pre meditated, planned this way, created this way, measured this way, consciously drawn in the wrong place, outside standards, against rules.

Receive a hug my dear.

regards,

Carlos

[Eva]

15uH will show 1 ohm at 10khz and 2 ohm at 20khz. This may result in rolled-off highs with low inductance high end tweeters, not to mention low impedance ribbons...

If this amplifier can't drive a capacitive load with 10 times less inductance, there is probably some mistake in design

The RC load should be at the other side of the inductor. Stability should be much better that way. The output stage really needs a low ohmic load above 1Mhz for proper phase margin and gain control.

[destroyer X]

I will love to reduce this enormous output inductor, i just do not know how to do it...i have enormous over shot without it, reason why it is there.

Can you help?

It is wrong, i know that, but this is the only way i had, my technicall resources are limited, i use hard work, try and error basis to overcome my limits.

It is sounding lovely, i would say unbeatable this way.... and this confirms to me what i had as suspections my whole life, the correct thing into scope and simulators does not correspond, does not match real live performance with the amplifier playing..the blameless, build the way it was, say, the original schematic, reproduce a very thin sound, nothing special.

I see it has an error, but i do not know where is the error...i want to fix, but i do not know how.

It was keept this way because sounding lovely, wonderfull!, unbeatable... smashed all i have in my home, including the digital one...but for sure i would love it facing capacitive loads and not using big inductors in the output line.

I would offer you a good glass filled with lovely hot Colacau (excelent soluble Spanish Chocolate) for that job!

Help!

Carlos

[destroyer X]

to have the overshot i will be very gratefull.

Of course i need help to fix, not suggestions about what to try, i have tried almost all possibilities into simulator and real life tweakings, so, the cause must be detected in advance.

I have the Multisim 10 files if someone really wants to help..to point errors there are thousands folks can do it, i want someone that able to offer the solution... having really good will to help, in a friendly and positive way.

regards,

Carlos

[Eva]

The 10nF capacitor impairs the current mirror above 200khz, it should not be there, it does not improve stability.

The 100 ohm pot is not the way to trim DC offset. There should not be any substantial DC offset in this amplifier without any trimming.

The 33R bypassed by 22nF on driver bases are calling for trouble, you usually want resistive input impedance at high frequencies and low impedance at low frequencies (R and L in parallel).

The 100uF in parallel with the Vbe multiplier is calling for local instability, a capacitor should not be placed there without series resistance, the output impedance of a Vbe multiplier is actually quite low due to the high local feedback.

You may find that diodes work better than the 100R and 200R on the rails.

2.2uF between the emitters of the drivers is also calling for local instability. Sometimes things don't work as expected (when you are only interested in the simple answers to complex questions).

The output stage usually needs 2 to 10 ohm of resistive load above 500Khz-1Mhz, that's the purpose of the RC at the output.

I think the the 27pf capacitor from the base of the BC546 to GND is not doing anything useful.

The 100R to 2.2R ratio of the BC546/BD139 emitter resistors is also calling for trouble (45). Emitter degeneration is used to force a lower current gain and get low phase shift up to a higher frequency in return. Theoretically a 100Mhz Ft transistor with a forced gain of 50 will roll off at 2Mhz, this is too low. Forced gains are usually 10 or less to get higher bandwidth.

Have you ever tried frequency compensation with two poles and a zero rather than a dominant pole?

[Ultima Thule]

Carlos,

if not done it is a good idea to ground the heat sink in a way to prevent oscillation when things are not in a metal case with common ground point.
But in your case I would ground the heat sink through a low value resistor say 10 Ohm as such it will be lossy to parasitic capacitances and inductances, some times a straight wire can also be bad.

Cheers Michael