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Old 22nd December 2007, 06:04 PM   #41
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Default Re: No Monsieur Gaetan. not to remove them

Quote:
Originally posted by destroyer X
Remove them ONLY and IF you find problems.

I have listened reports, from other friends, that those diodes detect Radio Frequency... also i had problems once, and recently i had problems even into the simulator.

It is difficult to me to explain things in English.... keep them in place IF you face some problems.... remove them, as the first suspect, if you have unstabilities.

I had....but..they are very protective to the 10 ohms resistance... and when that resistance burns the problems are very big...so... diodes are nice thing... they are needed...they are a nice solution...they are a clever solution..but they have shown problems.

regards,

Carlos

Hello Carlos

OK, I understand.

If somebody want to keep that diode protection to protect the 10 ohm resistor, how about placing a 10 Pf cap across those diodes if they detect radio frequency ?

Bye

Gaetan
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Old 22nd December 2007, 09:56 PM   #42
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Default May work Gaetan, good idea...also ferrite beads my help


Have to try... the next time i face that i will try your capacitor.

I am not very sure if will work..because capacitor where you have radio frequency detected... sometimes the capacitor can increase the detection, including it's own capacitance to the diode inter electrode natural capacitance.... this is something to try

thank you.

regards,

Carlos
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Old 23rd December 2007, 12:09 AM   #43
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Default Re: May work Gaetan, good idea...also ferrite beads my help

Quote:
Originally posted by destroyer X

Have to try... the next time i face that i will try your capacitor.

I am not very sure if will work..because capacitor where you have radio frequency detected... sometimes the capacitor can increase the detection, including it's own capacitance to the diode inter electrode natural capacitance.... this is something to try

thank you.

regards,

Carlos
Hello Carlos

Yes it may happen, the cap radio signal may need to be sent to ground. Or maby small inductor in serial with the diodes.

Bye

Gaetan
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Old 23rd December 2007, 06:13 AM   #44
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Default Yes.... into my imagination may work, but also can produce opposite effect


Dear Gaetan, mon ami, mon frère... pour vous.

radio frequency normally enters when find tune circuits... arrangements of capacitances, resistances and inductances presented into parts and boards.... it is a matter of luck sometimes... see the sketch.

The input parts, if their arrangement produces an inductor in parallel with a capacitor, there's a tune circuit... a ressonant pair... depending the capacitor value and he inductor value you will tune some frequency.

This tuning will depend of the circuit "Q"... something alike gain..also the slope of the bandwidth captured by the tuned circuit... this bandwidth (frequencies that can enter) can be explained by the sketch, showing two types of reception.... low Q and big bandwidth and high Q and small bandwidth...and this can appear combined too in many forms.

The diode uses to rectify the radio wave.... so.... separates the carrier from the modulation...that modulation is what can enters the circuit..something we cannot listen sometimes when modulated into frequency... when modulated in amplitude you perceive more easy the signal into the audio... the noises.

The diode, has a capacitance and inductance and resistance... all components have... normally not so big capacitance and not so big inductance and not so big resistance..but they can be understood by all those things together.... so.... may tune some frequency... if very small can be tuning cell phones or higher frequencies than that.... depends how close you are to the cell phones antennas... i have one 55 meters from my place.

And we have a lot of signals around to be picked... radio telephones... wire less telephone....electronic baby sitter... broadcasting stations... Radio Amateur... police car radios and some properties are protected by electrically powered fences that uses frequency generators too (oscilators)... and the fence is the aerial sending high power signal, as magnetic waves, into the surrounded air... and travells for miles away.

Inserting caps... inserting inductors..well.... we can make things even worst...but also we can tune another frequency that has not transmitters around...and this can work... deviating from the source of interference frequency.

We use capacitors to the ground into the input...but... depending the value...if smaller than 100 picofarads, can be more a problem than a solution..because associated with the board inductance into the input parts can produce the a tuned circuit, exactly into the broadcasting band..... 22, 27, 33, 39, 47 picofarads into the input represents "guarantee of problems"

Why?

Because the inductances values presented into the input parts and copper lines, together those values of capacitance we can install.. and also the capacitances presented into the parts to ground... and inter capacitance between parts, probable will reach frequencies that are used..so... frequencies that have signals around.. and they can enter the circuit.... facing a fast input transistor (differential) than the ship is made...a ship filled till the top with problems... those things are correlated into a formula... where enters frequency, capacitance and greek letter "P"...that is 3,14 .... because of that i dislike when people put radio frequency units (able to work into frequencies higher than 90 Megahertz).

Sound turns "arrested"... strange... without brigth...compressed...treble goes harshing... too much metalic... have some "squeak" sounds into the high frequency peaks... this can kill the amplifier sound!

Radio Frequency Interferences (RFI) do not recognizes borders, frontiers... it can be generated in other country, and even this way, enter your amplifier.

regards,

Carlos
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Old 23rd December 2007, 06:34 AM   #45
Nordic is offline Nordic  South Africa
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It looks just like an earth disconnect network actualy, those use 100nf monolithic ceramic cap to catch RF and pull it to ground.
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Old 23rd December 2007, 06:37 AM   #46
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Default Correct dear Nordic...big capacitors will force to tune a very low frequency..so...


circuit will NOT pick radio frequency.

But also...if too much big...will be a filter of treble to ground.

The same happens with the input electrolitic condenser or input capacitor...it also filters the treble too, depending the value and the base resistance.... the input capacitor and the base resistance are in series to the ground...so... a filter!... the passive RC filter.

Because of that, people use to put the smaller possible capacitor into the input..not to have losses of high frequencies there.

regards,

Carlos
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Old 23rd December 2007, 06:56 AM   #47
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Default Imagine that crazy sittuation... of course very exagerated


Treble goes to ground without enter the differential.... no treble into your audio.

Gonna have nice bass.... but trebles...ahahahahah.

regards,

Carlos
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Old 23rd December 2007, 02:16 PM   #48
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Still much work to do, especialy since Carlos published at least one updated schematic in the time it took to get this far... also still needs the output resistor, and need to accommodate the cap on the input which increased 1000 times in value since the first publication.

Click the image to open in full size.

Click the image to open in full size.
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Old 23rd December 2007, 03:56 PM   #49
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Default Sorry dear Nordic.... i am always trying, doing, searching..sorry for that


When young, mother use to say i had a flea inside my pants.

Now a days, very fat, i do not move to much..but brain is always working, i use to wake up during nigth to take notes of things i conclude over nigth... when left neuronium is sleeping the rigth one is waken up...the third and last one is always thinking how to put the other two ones to figth...as he wants to the the only one.

I am sorry to say.... if Precision.... three transistors are needed dear Nordic..three pairs.... was error..... could create problems..there are dangerous speakers and some amplifiers "destroyers" too.

For Sakis, the Greek warrior, the amplifier has to accept shorts into output ( 2 ohms or less) having square wave into the input, overdriven..he is professional in public adress and he needs something huge...those folks can kill the HRII in flash using two transistors into the output....and worst... Sakis, if construct, will make it bigger, better and will put higher supply voltage too.

I would like to ask you dear nephew Nordic.

It is time to make some modifications..boards not ready..this one has only two output..so..will not be fine.... and also because of that, we have some time to do some tweaks.

I want to make this amplifier not only mine design and your board... i would like to have more from you on it.

Please tell me if you dislike some circuit, some subcircuit, some value, some current, some heat...if you prefer the output with coil...tell me what you would do with this schematic go make it more nice to you... and i will try to do it.... and fast!

If possible...of course... but i think you have possible ideas.

What is Pi?... is the Greek letter, the "P" letter ..... 3,14

regards,

Carlos
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Old 23rd December 2007, 04:05 PM   #50
Nordic is offline Nordic  South Africa
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Its the Precision I

BUt it can play on words PI like in math, or PI like Private Investigator...

What are those small caps from base to base on output for, they are a bitch to cater on PCB for....
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