Thanks phatt, gone into the AVA in-tray.  :dbtu:



{Ya'know, I have a funny feeling looking at that broken PCB splint job and pile of 5W resistors  ... I'm not going to dig back through my job sheets, would have been more than ten years ago, but I have a funny feeling ... I don't remember no quad box, but there was a time when amps were coming in from very far afield, Brisvagas to Sinny.  What location did you pick this up, NSW somewhere?  There might be a "RR-squiggle, date" in pencil on it somewhere.}

Was.  This was my "Walden" period.   :loco

Something that is not obvious from the SatView is that it is the edge of an escarpment that drops very rapidly to Dingo Creek and the Manning River to the South, so you can see hundreds of km from the edge.  On foot this country is very hard going.  Most of the farmers work it on horses 'coz aggie and quad bikes won't do.

One thing about living in the middle of a native forest, it's the critters turf, so you just have to be accommodating when they decide to pass through ... or move in; more species of moth than you can count, half a dozen different frogs, lizards and skinks taking up residence, firefly's and glow worms, fungi that glow in the dark, birds ranging from tiny Blue Wrens, Wagtails, Flycatchers, a riot of parrots, Hawks and Eagles, every day, micro-bats to flying foxes, Boobook and Powerful owls.  Sundry snakes; even had a resident Python for quite a while, resident skinks, Horseshoe-nosed bat, bush spiders as big as your hand.  The rule is pretty simple - don't try to pick me up and I won't bite you.


http://www.canberratimes.com.au/act-news/canberra-life/gang-gang-powerful-owl-visits-20141203-11z2wx.html
(on one of my farm minds I would see one of these fellas almost every evening and fully grown they are BIG, ~2m wingspan.)


This is now;
-37.430748, 143.900123

It's a tiny block with a cozy little 1 bedroom house, but it adjoins the Creswick creek breast and redundant soccer oval, both flood prone, so I'll never be built out, and the Council kindly mows my "front lawns" for me.    Oh yeah, and lots more forest ('tho this is mostly plantation).

There's a guy just across the road that builds stock car racers and there is the occasional engine revving, so I think I might just get away with a speaker white or pink noise test out in Northcott Park provided I didn't over-do it (not that I'm into that much these days).


From SatView it looks like Missouri is a pretty quiet place too, rural, farming and forestry and not a lot else.  Everything I know about Missouri comes from the Brando film The Missouri Breaks (1976).

Interesting landforms;


Similarities to Northern New South Wales Gorge Country.  This is the Ellenborough Falls and gorge which was just down the road;

At 600-odd feet it is supposed to be the longest single drop waterfall in the Southern Hemisphere.

The general nature of the country, plateaus divided by steep gorges, Oxley Wild Rivers National Park;


The RAAF play cat-and-mouse up these gorges at close to the speed of sound, F111-E's trying to outfox a pair of FA-18's.  One time doing a farm-mind in the far back blocks of Doyles River I had a pair of FA-18's fly through the veggie patch at Mach 0.9.  You think I'm kidding?  I happened to be looking in the right direction to get a 100mS snapshot through the trees of the pilot in the cockpit going past not a hundred meters away.

But mostly it's just munching Kangas and galloping Wombats.  And Cicadas.  Lots of Cicadas in the summer.

This was my service patch, often literally "in the field".  Many service calls included home-grown dinner, music jamming (pack guitar) and stay overnight (pack O/N bag).  It could get cold enough to snow (yes, even at that latitude, because altitude), and at times people had been stranded in the Bush for up to three days (water, food, paper, lighters, big tarp).  All your tools of course, but also boxes with every spare and fitting you are even remotely likely to need.  Fuel up, and anything up to a 50-mile dirt road drive, avoiding kangas, cows, and the occasional log truck.

Always an eye on the weather; windstorms can bring trees down over back roads (pack chainsaw, "turfer" tree winch, and chains); the Wet can deliver a deluge of an inch and hour or better for hours, rapidly bringing up creeks and rivers and making roads too slippery to be passable.

As a mechanic friend put it when I asked about getting a four-wheel drive, "The difference between 2-WD  passable, 4-WD passable, and totally impassable, is five minutes around here - not worth it."  And vehicle traction is always a concern.

Awww - cute lil HAMP-STA!

{Had to house mind some of these once.  Randy little buggers.  The male would ram the end of his cage to move it closer to the female.}


Don't ya'll got no NasCar in Missouri? 

In the Bush you tend to see the odd battery catastrophe; and yeah, Lithium's are a worry.  There are lots of Utoob vids of people stomping and otherwise abusing them into reaction, but there is also CCTV of a girl on a bus in China poking at her phone when it suddenly bursts into flames and she rapidly leaps off the bus with it burning like a traffic flare.

pprune forum for all the guff on MA370.  I'm keeping a very open mind (you know I've got a bit of a history in accident investigation, eh?) and I don't have any scenario strongly in mind, but I have tried to fit what little we do know.  There have been two incidents of oxygen fires on these aircraft, and looking at the state of the cockpit controls after they put it out, the computers are flying the plane, but how can you fly the computers?


(transponder controls: centre console, bottom-right)

If I was sitting in the right hand seat and an oxygen fire started right next to me I would be up and outta there like a flash (standing on the transponder control panel on the lower right of the central console) in the panic.  If you have never seen an oxygen fire, then just think "petrol".  "Intense" doesn't cover it.  The pilot on the left might have some more time to try and reverse course, but does he put on his smoke hood?  Is it even working now?  How hot is it getting?  Pretty soon it would be abandon the cockpit or die, but the opinion has been that at that altitude, once it had burned through the hull it would have been self-extinguishing due to decompression effects.  So maybe they can go back into the cockpit, but what's left?

It has been demonstrated many times that an aircraft can still be flown with badly impaired controls, but this is the world of Fly By Wire.  How much control would you have over your computer if your keyboard and mouse had melted into a puddle?  The computers themselves are all still snug down in the avionics bay, chugging away.

I think the FDR will confirm what we know about what it did, but won't answer the question "why"?  And the CVR will only have the last 30 mins before ditching, so that's unlikely to cast any light on anything.


Was at a friends place while he was replacing his crawler battery (big) that had been on charge.  Accidentally flashed the terminals to the machine frame and the battery violently exploded while he was holding it, enveloped in a large cloud of fog (O+H=water), shattering the plastic case and sending shards several metres.  He was very very lucky that he was only hit in the face by small stuff, and it all missed his eyes.  He had an outside shower nearby so I frog marched him under it, and no great harm was done.

My travels have taken me to many "new settler" homes and properties because if my experience with off-grid systems.  On one property I came across a sorry sight, several solar panels that where all blackened internally, and some 100A/Hr house lighting batteries that had ... well ... melted.

"It's okay, I know what I'm doing".  This young fesbian lemonist was building a dwelling, and wasn't gonna ask for no advice from no man.  I can only guess that she reasoned that the batteries in a radio go positive-to-negative, so she wired the batteries like that.  So far so good.  12 volts.  Cool.  Now all I have to do is connect the solar panels the same way, positive to negative.

Well what she got in very short order was a whumping great silicon diode forward biased across a 12 volt 100A/Hr battery set - and a lot of heat everywhere in a real hurry.  In fact I suspect that it went pear-shaped so fast she couldn't safely disconnect anything, it all would have been alight with burning melting insulation very fast.   

These are some of the reasons I want to see a final backstop fuse/interrupter close to each battery terminal.   :dbtu:

Quote from: HawkI'm used to seeing them run on the outside of the schem them go to the input of an op amp

Above I compared one of these OutPut stages to "a power op-amp", which is what it essentially is, and like an op-amp it has inverting ("-", NFB) and non-inverting ("+") inputs, they just aren't normally marked as such.

This example uses an actual op-amp as its first stage;

(and runs the NFB round the bottom, just for you  )


Feedback in s.s. amps is a bit of a trick because it is both DC and AC.

(Ignoring the values) this is the outline of the majority of s.s. power amps;


Notice that the bottom leg of the feedback divider is connected to ground via a capacitor.

For DC signals this cap is effectively open circuit, so this means the amp is a voltage follower with 100% NFB, unity gain.  The DC point is set by the 10k to ground on the "+" input, so it basically "follows" ground for DC.

For AC signals where the reactance (or AC resistance), Xc, of the cap is low then the ratio of the feedback resistors sets the AC gain.

Revisiting our highly dubious circuit, the feedback components are the 22k on the half rail (generically called Rf for "feedback"), the 1k resistor (generically called Rs for "shunt" i.e. "across"), in series with the 10uF to ground.

The attenuation of Rf and Rs at AC is;

Rs / Rf+Rs

1 / (1+22) = 0.04347826 times

dB = 20 log₁₀(V1/V2)

20 * log10(0.04347826) = -27.23455689dB

This means that the power amp has a forward gain of +27.2dB between input and output.

The supply rail is +38V, but let us assume that when we take into account all the E-B drops that we actually get 35Vpk.

There are a couple of ways to work this out, but if we take the maximum peak output voltage and multiply it by the NFB network loss, we should have the peak input voltage for full output;

35 * 0.04347826 = 1.52173910

1.5Vpk or about 1V_RMS - which is exactly what I would expect.

Quote from: Hawkand possibly it would be out of phase by 180 degrees.

Close enough to earn a small prize;

(I do hope you aren't diabetic or anything)

You're right, by drafting convention in s.s. amps the NFB normally runs back down the middle, while in valve amps the OP transformer gets in the way, so it has to go around, typically under.


Both of the problems with this circuit relate to the arrangement of the input transistors.  The minor work-but-not-well, problem actually struck me first.  But as they say you never find just one roach in a kitchen, so while having a deeper look it only later struck me that there is something quite fundamentally wrong with this circuit.

Let's start at the input and inject a notional small negative-going signal and work out what will happen.

This will cause the first transistor to conduct more, to turn on, so the join of the two emitters will also go negative, also turning on the second transistor.  This in turn draws more collector current so it will also turn on the third transistor (top-center, sometime called the Voltage Amplification Stage, VAS).

This in turn will cause it to pull its collector more positive, and since this is also the bias point it will turn on the clutch of upper transistors, and turn off the lower clutch, so the output half rail will be pulled positive.

Now this positive-going signal is taken back to the base of the second transistor, but it has just had its emitter pulled negative, so this positive-going feedback signal will actually try and turn on the second transistor harder, and the VAS, and the output clutch.

In other words the feedback is not countering or rebalancing the input signal, rather it is reinforcing it - i.e. the negative feedback isn't, it's positive!  {oh Gor blimey!  :duh }


{I've already written quite a bit in other threads about the need to keep your wits about you when looking at circuits on the net.  I followed this one up and it has been up for years, and not a mention anywhere that it cannot possibly work.  But he ain't so bad; there are other sites that are riddled with such nonsense - redcircuits and runoffgroove come to mind, and a certain zombie "Blackface" FET preamp full of trimpots that just won't stay dead.}


Okay, the lesser problem.  As you know we want these output stages which are direct-coupled to the loudspeaker to have minimal DC offset, when idle the voltage on the half-rail needs to be within a hundred millivolts of zero or standing excessive current will flow through the loudspeaker.  Zero is the ideal, but for several real-world reasons we are generally happy of it's only tens of millivolts.

As you may be now guessing, the prime determinant of output offset voltage is the input arrangement, and may illuminate why the Long Tail Pair is so popular as the first stage.

Now, just pretending for a moment that this circuit doesn't have the NFB blooper and in fact has proper NFB.  What would the output DC offset be in this amp?


{hint: the base of the first transistor is tied to ground via the 10k, so applying very basic transistor knowledge, the voltage on its emitter must be...  and therefore...?}

I just grabbed this circuit at random to illustrate a couple of points about the output section;



... but on closer examination it contains a couple of real design bloopers. 

One error means this circuit would not work at all, and even if corrected the other error would mean it would then not work at all well.

No prizes for the techs, but can you spot them Hawk?


{proving once again that you can't just take any circuit on the internet at face value.}

...and fuses (or circuit breakers) too, one for each rail, say 10 amp, real close to the battery terminals.  A short circuit can light up a cable in a second.


{1AM, gig over, vehicles packed we set off home in convoy.  Only a couple of minutes up the road and the car in front suddenly pulls off the road and the driver door opens and the driver bales out before the car has even stopped.  Now he appears to be break-dancing in the middle of the road  :duh - quite impressive for a tired drummer pushing sixty.

Now he appears to be stripping, ripping his jeans down and trying to get them off over his boots.  We watch in awe.  Now there is the smoke drifting up from his jeans.   Impressive.   Pity he didn't pull this sudden outburst of creativity mid-evening when it would have wowed them at the pub.

Seems he was helping the guitarist with a 9 volt stomp battery problem before the show, and in the swaps one when into his jeans pocket.

This all went well until a coin also in the pocket shorted the fresh battery on the trip home.}

The Long Tailed Pair, a.k.a. a differential amplifier or emitter/cathode-coupled amp.


(the interlocking circles at I_E is a constant current sink, but often just a resistor)

The "long tail" comes from the shared emitter (cathode) resistor.  This is normally a high value connected to a fairly high negative voltage, and therefore approximates an infinite resistance connected to an infinite negative voltage, the result of which is (almost) constant current.

A refinement is to make this common tail an active current sink (source) so that within the limits of available voltage it really does act like and infinite resistance connected to an infinite negative voltage.




The "differential" comes from the fact that it amplifies the difference between the pair Bases (grids) and also has a differential output available at the collectors (anodes).  As such it is a very sensitive amplifier, 'tho easily driven into overload.  Ideally the diff. pair are quite deaf to any signals in common mode to both inputs.


Because the total tail current is constant, so therefore must the sum of the Collector currents be.  As one collector current rises from zero so must the opposite Collector current fall by exactly the same amount, so the Collector currents (and voltages) mirror each other.


The "Emitter/cathode coupling" comes from the signal passing from one device to the other via their shared Emitter/cathode circuit.

The LTP structure forms the basis for many op-amps (look at op-amp datasheet internal circuits).




In audio power amps the signal input is generally the non-inverting (+) input while the other is the inverting (-) input and is connected to the main output to provide overall Negative FeedBack.

Because of the high gain the LTP is sensitive to any difference between the two active devices, in particular the thermal change in the Base-Emitter voltages.  For this reason they are sometimes matched pairs, and you encounter twin transistors with six legs so they are tightly thermally coupled (apart from being inherently matched twins on a common chip).

{on the other hand Elektor made use of this "shortcoming" by using two fixed-bias LTP's at right angles  as a no-moving-parts wind speed and direction sensor, the wind cooling the upwind device more and producing a voltage proportional to the vector of the wind.}

Quote from: js1970I'm trying to get the gist with regards to what you said. I'm not sure what doesn't fit. Is it that I'm getting 40V difference at R317 ,or that if 2.67 mA are flowing through it,it should not be so hot.

Simply that your two observations are contradictory.

Your voltage measurements suggest that the resistor is dissipating one-tenth of a watt (and these numbers look pretty sensible), which is almost nothing and you should be able to hold the resistor between your fingers and feel a bit of warmth.

Yet the resistor is getting very hot.

These can't both be right.

I'm inclined to place more trust in a burnt finger than your measurements or my calculations, but there is an anomaly here, and "following the bit that doesn't fit" is always profitable when faultfinding.

I can't guess what the answer will be, but these two observation are uncomfortable bedfellows - there is something that needs to be resolved here.

"Paddock" = the log dump of a shut-down sawmill.
-31.630487, 152.297325

If I'd had any of those in my paddock I would have been somewhat distracted from my mission.

doc: Do you smoke after sex?
blond: I don't know, I've never looked.

{Of course none of the above has anything to do with the gratuitous use of young women's' bodies to sell products.  Related to almost nothing, did you know that the advertising of tobacco products has been banned here for some years, they can only be sold from plain cabinets, and now have to be sold in "plain" packaging which is actually covered in health warnings and lurid pictures of sick peoples plumbing?  Smokers are now only 20% of the population and falling.}

Actually, I'm more into goats than sheep, just more interesting generally, good sense of humour, better conversationalists...




...I should get into town more often.   

QReuCk

"Power compression", voice coil heating, &c; I'm sure JMF has more observations...

---

phatt

I have a laundry and shed full of spare 'puter everythings.  In bulk.  :lmao:


(Gerald, the extra RAM)

My mom was a teacher and writer, so there was always a tripewriter around, but somewhere back about when the first 4004 microprocessor was hitting the streets (1971?) I wrote an article for the national Ham Radio mag titled "White Stones With Gold Legs", and later did a presentation to a large Ham radio club.



These guys were wetting themselves about a device called a UART ("you-art").  This is a computer system building block that manages serial RS-232 (pre-USB) communication to the outside world, such as a user terminal (screen+keyboard) or printer.

There was a whole Ham/tech community that was fixated on a single small ordinary Leggo brick, the UART, and ignoring the box full of system bits, the RAM, ROM, CTC's, IRQ's, DMA, but mainly the central engine of the whole works, the CPU, the "microprocessor".  They were missing the whole point!  This was a paradigm shift from wired logic systems to stored programme logic systems, and a lot was going to change for techs as a result.

And while writing this stuff on a MicroBee (to cassette storage, then CP-80 dot matrix printer), I had an epifin... upif... a sudden realisation that typing was going to be an important future skill for any technician.  So I got quick.

Since then I've completed more than twenty major software projects, where "major" means more than about 10k lines of code, which can mean months of coding and testing, all keyboard work.


I once had the privilege of playing a 1930's Gibson acoustic guitar.  It didn't look like much, dull finish, but when you picked it up it almost played itself, it tempted you to do things you wouldn't dream of attempting on your own guitar, and when you fluffed it you were forgiven.


Well by far the best QWERTY keyboard I've used was on a NEC APC-III, sat nicely on the lap, and dished perfectly for speed.


I've just had a very nice weekend houseminding a lovely little dog, a heated jacuzzi, and a Yamaha upright piano.  Now my Yammy DX-7 keyboard is plastic with no "feel", but it's solid and tolerable.  I have a couple of others that are worse, "plasticy".

So feeling the hammers under my fingers, the mechanism and linkage, not only fairly tight, but not really "played in" yet (with only kiddy practice), gave a feedback that caused me to go right off for a couple of hours extemporising.  Been a looong time.   <3)


...ahem ... yeah, well anyway ... movin' right along ...

Quote from: EnzoHave the bassist consider getting an acoustic bass.

Funny you should say that, was thinking similar because I knew a guy who had an acoustic bass guitar who brought it to campfire jams.  He wasn't a very effective player, but it was certainly audible (and no risk of speaker "frapping").

Random pic to illustrate;


Big mutha, but sure beats the battery problem.


{Somebody asked me to do some designs for portable sound systems for very small forest gatherings.  It resolved to two 8" J-horns and an equipment pack with mainly car audio gear.  And of course batteries.  The idea was a sound system that didn't require the back-packing in of a noisy, smelly generator and fuel.  Interesting set of design constraints.}

Thanks g1, I was hoping it was implicit, but you're right, it should be nailed down.


In the amp circuit above the output or "half-rail" is the bit between the speaker output terminal (22uH inductor) and the 22k Negative FeedBack (NFB) resistor.


We also have two supply "rails", +38V and -38V with respect to ground.  ("rail" simply means that it is a distributor (of power or signal) and has quite a few connections; "buss" is sometimes also used in a similar context, audio mixers, power distribution).

In between we have the output "rail" connected to the output pair emitter resistors, the speaker, and the Negative FeedBack (22k above).  This output rail is also known as the "half-rail" because when the amp is working correctly it adopts a voltage half way between the supply and ground, or half way between the split supplies (+/-100mV).

This is actually a very important test because (apart from not lighting up your speakers - which is why we keep hammering "disconnect the speaker") if the half rail is right it is a strong indication that the whole output stage is working correctly - it has to be to achieve this "rebalanced" condition (the OP stage is basically a giant power op-amp that rebalances itself to the midpoint because of a lot of DC NFB - if something in this NFB loop isn't working properly then the amp is highly unlikely to "centre" or rebalance the half-rail).

On first encounter the half-rail voltage can also give you a strong indication as to where to look first.  If, say, the upper OP transistor is shorted then the half-rail will be close to the +ve supply, similarly for the lower transistor, and if it is at some other odd voltage it suggests that both OP transistor have blown open.  Like a pulse the half-rail voltage can tell you a lot about the patient with only one measurement.

In the early days of transistor amps it was fairly common to use a single supply;



...where the output would bias to half the supply voltage, hence "half (supply) rail", and needs to be DC blocked by a large output capacitor.  You still find this arrangement in smaller combo amps, particularly older ones of Asian origin.  (The output cap is more commonly between the OP stage and the speaker, with one side of the speaker grounded.)




The trend a bit later was to use a split supply;



...which eliminated the need for a specific output DC blocking cap because the "half rail" was now half way between +ve and -ve, i.e. at ground.  This is by far the most common arrangement these days, and particularly in higher powered amps.


Actually there isn't a lot to choose between the two arrangements, but Doug Self does make an interesting observation that in the latter the speaker is DC coupled to the output stage, and if the OP stage should fail you can get speaker combustion.

Some people (generally Hi-Fi buffs) don't like having a big electrolytic in series with the speaker with all those audio amps passing through (because, ya know, capacitors - they tend to have a thang about capacitors) , but you can redraw both arrangements to show that for audio frequencies it's a distinction without a difference.  In the split rail design the output currents also flow through the power supply filter caps anyway, it just isn't as obvious.

Ground
If you examine the circuit fragments above you will notice that the ground is in different places.  Which bit of the circuit is actually grounded to the chassis is really a bit arbitrary.  You may be using a metal speaker jack that has one side connected to the metal case.  With the single supply it then makes sense to call the -ve end of the supply "ground".

It is not unknown to come across 1970's Asian PNP single supply designs where the supply +ve is grounded (and the negative supply coded red - caution!).

If you are using a split rail supply design then the more logical place is the mid-point of the filter caps, but it is also possible to ground the half-rail output and let the supplies flap up and down (as one manufacturer does - to me this is the tail wagging the dog, but I'm sure they have their reasons).

Hi JLT, welcome.



The short answer is to get an commercial mains voltage inverter and battery.  The simplest, most direct, but possibly heavy and inefficient way.

2) is a reasonable idea, more power efficient, but how do you know the internals run on 12 volts?  It's pretty unlikely, more like two lots of split rails.


Now automotive audio runs off 12 volts, and there are quite a few moderately powered amps kicking around (often cunningly disguised as small graphic EQ), so why not start afresh?

Put that amp to one side for home, and consider building something that is purpose-built, for her in her situation.

I'd start hunting second hand shops, garage sales and swap meets looking for a modern-ish car radio (cass/CD/MP3?) that has "Aux" in's.  One channel of this should be enough watts for a campfire jam.

I can see this built inside a large plastic jerry can, 12-inch speaker, radio mounted near the top, batteries secured in the bottom, sundry methods of recharging, plugpack, car adapt, solar, hand-cranked gen, windmill, thermopile for the campfire...


(Needs some speaker protection)

Add a couple of ply doors to protect the speaker in transit, but open to provide a rough horn in use.

Quote from: Hawk on March 19, 2015, 09:03:03 PM
I'm referring to the O/P at the bottom of Roly's current limiting diagrams at top of page. Thanks

In this context "O/P" = output, the amplifier "half-rail".


Working backwards.

Quote from: HawkHow long has this forum been in operation? I'm tempted to print off all this info but rather than do that and save some trees I'd rather return to it electronically a month/year/decade down the road. Is there a way to bookmark this post as it will eventually descend further down the post line and be tougher to locate. Can it be saved electronically? Thanks.

If there is one thing that forums generally lack it's indexing, being able to find what you want in ways other than Google.  Proper indexing of topics has to have a human input from somebody who knows a bit about the craft, sundry wrinkles of terminology that are, or are not, conceptually linked.

The mechanics are there to be used.
Each forum, tread and post has a heading, and that heading contains the URL of the item (right click copy link location, paste, e.g. your post)
http://www.ssguitar.com/index.php?topic=3707.msg28813#msg28813

The page number contains the thread page;
http://www.ssguitar.com/index.php?topic=3707.0

The heading bar;

QuoteSolid State Guitar Amp Forum | DIY Guitar Amplifiers >
    Solid State Amplifiers >
    Amplifier Discussion >
    Marshall Valvestate 8100

Also contains URL links.

As you can see above I make free use of hotlinking content.  To me that is the whole idea of the internet.

In Cyberspace the "distance" is the retreval time.

Every single post on every forum is simply an available item, and all you have to do is point to it - from anywhere.

Any page on the net may consist almost entirely of links to external content.  In fact I ran for a short time an edited index to a forum.  I didn't want to stop people going to the forum, but a group of people wanted to present an edited version ordered by topics.

You can make up HTML pages for your personal use, or topic sub-folders in your browser bookmarks.

Quote from: HawkSo Beyond the Output Transistors we have resistors and caps between the OT's and the speaker jacks, plus some caps. Are these covered in the solid state amp book? Or can you give me a basic understanding of their importance? Thanks.

Okay, mid-right we have the power transistors driving the half-rail via a couple of very low value "emitter" resistors.

Next we have a low value resistor in series with a cap to ground.  This is the Zobel stability network.  It is to prevent parasitic HF or VHF oscillation modes in the output pair.

Then we have a small inductor and resistor in parallel.  This is to isolate the output stage from any capacitive loads (such as crossovers or piezo tweeters) that may cause instability.  The resistor is to damp the self-resonance of the inductor (and is often also the form for winding the coil).

According to Doug Self the values of these components is not critical.

Great post JM!  Thank you for that in depth consideration.  I'm educated.

Quote from: J M Faheyan accepted substitute was to dig a large hole in the ground, close it with the proverbial plywood sheet, mount the speaker pointing at the sky and suspending the microphone from a wire hung between post at a convenient altitude.

There was a time when I had a rather large paddock next to my workshop at my disposal.   

No kidding.

Quote from: EnzoThe lesson is that power is not loudness.   So when someone asks how to double his output power so he will be louder on stage, he is not headed for success.

Which I think is why I'm still so hung on horns - they are quite a magic trick.   <3)