TCJ - Evolve simply and good amps idea

[padamiecki]

Dear Friends!

I would like to share with a few amplifiers ideas (some of the are playing already!).
The ideas were born after reading 2004 blogs by John Broskie in TCJ.
Very similar ideas could be found on the sites of Evolve Power Amplifiers.
The pdf file consists of 3 projects with the results of simulations.

First two have 75mV 1 kHz sine wave at the input. The transistors are 2n2955/3055. Those are only ideas.

Third has at the input 1V 1kHz sine wave. The transistors are IRF540/9540. This amp I have built in two versions:
• First – power supply voltage only +-13V, signal directly from a source, potentiometer, connected to the 10kOhm resistors (in the middle). NFB resistors 12kOhm. In power supply ordinary parts. Sound: GREAT from the start. Detailed and not grainy. quick, deep, low bass, wide stage, wooden saxophones, vocals not sharp. It works stable from 11-2004. Rest current only 200 mA per hexfet.
• Second: - As a preamplifier connected via a paper in oil capacitor, I have used E88CC supplied from only +43VDC power supply (!). 180 Ohm at the cathode, 4.7 kOhm at the anode. The capacitor at the solid state side was terminated to a ground via the 380 kOhm resistor. Power supply +-23V, super fast diodes, battery of paralleled good, fast capacitors. Rest current 350 mA per hexfet.
Now some notes about the sound: VERY good bass, detailed mids and highs, deep stage, but a little too bright sound. Saxophones are a little metallic, not like in tube amps when you could hear the wood.
In a comparison with a tubes it sounds metallic and bright. I am used to tubes and for the first hearing I was disappointed, and thought that it sounded like kick in the balls (Carlos will be happy reading this). But after some time amplifier started to sounded more smooth and culture. Now I like it especially that is better of any solid state amplifier that I have ever heard.

I am curious of your impressions after building of those simply circuits!!!

[Dozuki]

I too have seen the circuit that you mention on the Evolve site. I even considered building a version. Nice to know that you did it successfully!

I would love to see the schematic of the Second version with FETS including the tube stage.

-Doug

[destroyer X]

And of course i like the things you do...of course.

And i will hear them...also of course.

Carlos

[destroyer X]

Yes i did it!

Carlos

[destroyer X]

I am doing already that.

Carlos

[destroyer X]

Those more simple designs, more close with the wire with gain.....are normally very good.

regards,

Carlos

[destroyer X]

But transformer are heavy when fall down into our fingers.....hummm this is not too much stimulating to me.

regards,

Carlos

[padamiecki]

Originally posted by destroyer X
But transformer are heavy when fall down into our fingers.....hummm this is not too much stimulating to me.

regards,

Carlos

Hi Carlos,
low power transistors = low offset,
in practice I had to regulate the offset paralleling one of the nfb resistors with another resistor (rather high value ~1MOhm).

[padamiecki]

Originally posted by Dozuki
I too have seen the circuit that you mention on the Evolve site. I even considered building a version. Nice to know that you did it successfully!

I would love to see the schematic of the Second version with FETS including the tube stage.

-Doug

Hi Doung,
the tube section is not a realy sophisticated circuit:
common cathode circuit
with a res 180 Ohm as cathode res,
and 4.7 kOhm res at anode.
The signal is leaded by paper in oil capacitor to the current amp.
the input signal is connected to a e88cc's grid via a 470 kOhm Alps potentiometer.

Luke, use the force, and imagine this

Now I do not have chance to send this circuit at the Forum, I will do it later.

[darkfenriz]

CzeϾ
When you re-write schematics but change ground with output symbols (so that supply is no longer floating and output is emitter follower) all starts to look quite ordinary. Only the input signal is kind of 'bootstraped'.
what feedback circuit do you use?