Incredible quality amplifier by Graham, prepare your ears for it

[destroyer X]

So, image very adequated.

Carlos

[destroyer X]

And P3A designer is not so close as Hugh and Graham.

So.....hehe

Carlos

[destroyer X]

And both are good amplifiers, but nothing exceptional on them...just a very good amplifiers, near to pop out of the bubble of nice amplifiers.... near to go to special amplifiers, and not incredible amplifiers.

I am already reasonable old and Neurothical!... and i have not more patience with common amplifiers, as i made thousands of crabs!.... the only way i have to compensate the enormous tension and frustration with that long search of heaven!... a very frustrated search when i go to alive music to compare!, than i turn very agressive...better to be agressive with parts and boards than point all that agressivity to humans..this way guys!...shot the boards!

I think will not receive a shot...let's see.....if receive a shot i will show you the result!

regards,

Carlos

[destroyer X]

I printed an studied hard the Blameless and all theories, and i run to construct happy to find, finally, a good amplifier.

The most terrible crab i had in my home.

Here is the picture of my feelings, that result in an agressive behavior related the circuit.... i Shot! the board....BOOOOOOOM!

Will believe in someone that publish something with 1 percent distortion...may sound good.

Carlos

[Greg Erskine]

Geez Carlos, I'm having trouble keeping up.

Originally the thread was about Graham's "Diamond" amp. That's the one I think I did the schematic for.

Then, I think you were talking about Graham's "Crab" amp, an early version on the Diamond but no good. You're pulling that apart?

Next was Rod's P3A that was good but not special, so you're pulling that apart. I am right? And...the Leach amp sounded about the same as the P3A, so do you still have the Leach amp? I'd like more of your feelings of the Leach amp as I have been tempted with this one.

Then, Douglas Self's Blameless "or should it be crab" amp. I guess you didn't like that one much. Arh, just got it, it has zero distortion, and you didn't like it so you want an amp with 1% distortion.

Thanks for the feedback on the schematic, now I have to learn how to design PCBs, then build the amp. Don't hold your breath.

[destroyer X]

In my point of view.

It was produced to receive low impedance, already amplified signals from portable wonderfull modern CD players and things alike that, that have low impedance and 775 milivolts minimum over 8 ohms output.

You see, that Graham do not like Miller capacitors, he do not want capacitance inside the audio chain.

So, you see circuit very strange, without not too much capacitance in series with feedback line...only 22pf...also he is avoiding, in many schematics, to install the conventional 100 to 390 capacitor to ground....he is using, unless in the majority of his schematics, values lower than that...this is from Radio frequency only, to send Radio frequency to ground...but this is for the ones live near Radio Amateurs or Big Broadcasting stations...something that will work in one home and will not work in other thousand of homes.

You see that he do not make any economy in electrolitic condensers.... because the use to non stabilized power supplies, some of them with small filtering inside...those capacitors guaranteed a stabilized voltage to amplifier input, without any ripple over it....also in the feedback network you will see that enormous condenser is there, ...to guarantee half cicle reproduction...this is the reason...the other one, is that Graham simulator, when you click in condensers...appear Milifarads in the place of Microfarads...so.....more fast to use, to go 1 Milifarad.... a thousand microfarads (he may be laughing now)

Graham do not like this coil used in output.... he always cut it out!.... but my simulator, without coil, normaly do not works...present errors...damn simulators!.... Graham amplifier is working!

The extra transistor is the real class A unit...over it all 400 miliamps and the one is heat as a hell...... the others, the normal output, common position of output when you observe, the complemetary units, are adjusted to 100 miliamps only.... so, this hi current, class A reference amplifier.... clean the whole thing!...how?... ask the King!...i do not know.

I suggest you to construct....yeah, i suggest that...but take a close look and evaluate for heating of the 2R2 resistor.....if it is hot (very hot..near melt) this is a result of oscilation flowing inside and going to ground...... if this happens to you, put immediatelly the Miller cap.... oscilation will finish immediatelly...but do not put amplifier into wave form monitor...because...hehe.... sinusoidal at 80 kilohertz will be reproduced as an wonderfull triangle!

There is something missed in the bias control...as you can advance it too much related the current...join base to emitter when start to adjust....dangerous to put enormous current and burn output...of course use series protective resistors.

The other one, more an more carefull, as this one is the potentiometer to adjust the extra transistor VBE...you can kill it easy.... put the Bias transistor with base to emitter and them go first measuring base to emitter, i am talking about the extra transistor, put voltage there around 630 milivolts to start...check current now, in series with negative supply...beeing reasonable, let if be... fron 200 to 500 miliamps.....now, measuring over the 0.1 ohms, or even 0.22 ohms emitter resistors, try to obtain
22 milivolts over those resistors...check if both sides are equal in current.

In the reality i use another adjustment.... a wrong adjustment... i made all circuit work with 400 miliamperes.... and i increase the current in the class A main extra transistor...this way.... the extra is working with 100 miliamperes...the opposite related Graham idea...but worked very fine...i will try the correct adjust latter.

But you can see, the amplifier reproduce wonderfull sound, with big power ( i did not measured...but may be 35 RMS in my case), and not listenable distortion, very clear and flat...remembering JLH basic designs with much more power and deep bass reproduction......better than JLH?...yes, it is.

Graham, please, take the chalk and go to the black board....oh!..now a days no more black, and nor more green..now is white with magnetic ink!.... modern things.... remember JLH guys!

regards,

Carlos

[Graham Maynard]

Hi Greg,

That certainly looks more conventional, however;-
I have found that taking the power rails to the pcb and then back out to the power drivers, gives more stable reproduction than when taking power straight to the output devices and from there to the pcb.
This is why I drew the circuit with that seemingly unusual configuration.

My mirror transistors are BC547C.
The NPN bias sensing transistor is another 2SC3421bolted to the heatsink, though could be anything similar.
2SC5200 NPN outputs are my intended choice. I was showing exactly what was running in real life (not just a simulated suggestion), and there is no reason why a wide range of transistors should not work very satisfactorily.
My Zobel resistor is 4x 10 ohm, and none of my resistors are inductive wirewound.
Unless constructors use larger output devices like Carlos with his single output pair, I would not recommend driving unknown 4 ohm loudspeakers flat out unless plastic TO-3 sized transistors are run in parallel.
I have smaller unindicated 'C's in parallel with the larger value ones shown, though I cannot say at the moment whether they actually make any audible difference in reproduction; would depend on electrolytic capacitor quality, which might deteriorate with time.
I always use star earthing because I found that common mode injection or rf interference pick-up or even circuit instability has been caused by just a few inches of wire linking a signal ground and a psu/Zobel earthing point.


I wonder ? Should I add the natural filtering of an input tube.

Just seen your latest posts here Carlos, will read later, wondered why I hadn't heard from you !


Cheers .......... Graham.

[destroyer X]

You understand very well my meaning.

When i made P3A i had already constructed the Leach Amplifier... the Super Leach amplifier, the one more complicated...not satisfied with the bass...it was there...but my cassetes that was very near the woffer did not shake (1 meter, not erased guys!)

I could make them shake with a 35 watts amplifier,a Sony model that have a circuit very alike AKSA 55.

P3A was something histerical.... very harshing in my idea..but do not remember very well...was dismouted alike thousands...i cannot keep them all here...no space enought...and too much money to keep them all here...so, parts are travelling from amplifier to amplifier..... with same parts and different sounds always.

A friend was called to say something about Leach...i was not happy with bass, told him nothing....he listened and told me not a good bass, and that a brazilian copy of Leach, the Cygnus are better, and that he had one in his home...... so, we put them together in AB comparison..... the Cygnus home made and the Leach also home made....really..... Cygnus, the copy, referenced in the leach amplifier sounded better.

I have it dismounted, when Rasmussen told that the guilty was the feedback line electrolic condenser, that i had to increase it...i was thinking to re-construct and do not did it yet....but maybe, the electrolitic condenser modifications will fix the whole thing...and a lot of good guys apreciate the Leach amplifier, so, it may be good..... do it and tell me what you think, please.

I will give to myself a brake...to listen the Diamond...the first published, by me, of the Graham schematics, and the last in his productive mind (more dozen may be already created since that one)...i am just listening and having pleasure with it....will discover defects too...... have to hear and hear..... stop and continue....when you continue you realise new things...as long hearing, the brain make the needed adjustments...if not, how can a human beeing listen to a small portable radio with a 1 inch speaker without be boered.....brain adjustment i think.

regards,

Carlos

[destroyer X]

A simplified schematic...one model use TIP41 and TIP42 as drivers... a very low frequency unit.... i think 3 db roll of may be around 3 Megahertz of something around this limit.

It is beeing used to Public Adress now a days...and also may units are inside enormous trucks, the Electrical trios, with people dancing over the truck's ceiling and all instruments there....a refrigerated inside,with double power generators and many PA units, surrounded with hundred of enormous speakers, exponential baffles, use to make our carnival parties, and some out of date carnival parties too...travelling whole country, during the year.

And there is Cygnus...pumping air like a hell...producing pressure in my abdomen... and hitting "down countries too".... your arm hairs start to move...and you cannot avoid to protect years...as 20 or 30 kilowatts are not uncommon.

here is the Cygnus schematic...the smaller one of the series...i think this one is 440 watts over 4 ohms...if i can remember...the model 400 was 200, this one 440 and have another near to ! kilowatt each channel...only more transistors and bigger supply.

regards,

Carlos

[destroyer X]

They were made based on Leach.

Many model where made, with fans helping the heatsinks.

PA400
PA-800
PA-1800

Those i can remember...the same circuit... some transistors changed because of bigger voltage, bigger swing, and supply was changed also, heatsink size of course increasing in the proportion the sound was increased.

Also they used a TL071 or TL081 in the input, to increase the level to the power amplifier...but in general, all schematic the same.

Good amplifier...very good amplifier.

regards,

Carlos