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Old 4th June 2007, 04:59 PM   #1711
inex is offline inex  Netherlands
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I am a bit bussy so i didnt had time to work on my DX amp.
when i got some more time i going to try those things sugested.

Also i going to have 2 more Amps ready soon.

Things done
The amplifier case is almost ready.
made 2 new amp pcb.

Things to do
Make 2 DX amp's
Design powersuply pcb
Design speaker protection
Get proper zobel resistance and cap

About the powersuply.

My amp is going to use one transformer so the two amps are going to share the ground.
So i dont know if i can leave out that resistor or not.

will post some ideas about the powersuply pcb later.


About the cost of the amp

transistors 10 euro
resistors and capacitors another 10 euro

then the powersuply
bridge 2 euro
2 t-network capacitors 80 euro
a transformer 50 euro

So thats 150 euro.
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Old 4th June 2007, 05:58 PM   #1712
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Default Oh!... Epoxi ideas came from "meu compadre" Jacco Vermeullen


thank you Jacco...nice words meu compadre.... pronouce is cumpadre!... that "U" is the key of the pronunciation... use the sound of boom...that double "o" sound in the place of the "u"

Compadre is the relationship created when someone goes to the church for the Baptims of some recently borned children...the one that takes to himself the responsability to take care of our children if you die....this is compadre...a very nice position that we deserve to our best friends, the ones we trust deeply.... a very pretty thing, alike the "best man" during marriage... i hope the best man do not have to take care of anything if the main husband die...hehe.

We call "padrinho"... for marriage and for children baptism.... padrinho is the Australian "best man".... and compadre is the best man dedicated to baptism.

regards, Jacco..... call me compadre means you like me.

Carlos

.................................................. .................................................. ...........

Line up.

Sorry, i am having some problem related memory..... i will visit your thread.... i am unsubscribed to tbe biggest majority of threads, only taking care of this one i have opened... so...reading daily i have not problems related memory... small time memory.

I know you deserve attention and i am not the one that had made you happy, maybe i am not able to be so nice that way.

Dx amplifier, for a while is a non profitable amplifier, opened to all people around the world...maybe, it is possible, that will turn a business of kits to brazil.... i am still thinking about...i have not idea of the cost, but all i have selected are old and cheap transistors, common parts, ceramic capacitors, nothing sophisticaded, made to be simple and cheap...i hope it will be cheap enougth.

I will be there... your headphone, the class A headphone thread

Bill of material.... i use parts list, is in the home page Lineup... honor us with your presence there, please,

http://users.tpg.com.au/users/gerskine/dxamp/

regards,

Carlos

.................................................. .................................................. .......

I Richie00boy

am observing your presence Richie00boy....you are welcome, always beeing kind and honoring us with your presence and support.

regards,

Carlos
.................................................. .................................................. ........

Inex

It is all rigth.... i was kidding and trying to atract your attention.... go slow and be happy.

Follow the intructions of Graham and Pavel.... they are very good into designs.

I tried both ways and i had no problem...but, their advise are good to avoid more problems.

regards,

Carlos
.................................................. .................................................. .....
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Old 5th June 2007, 05:51 PM   #1713
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Default I have tried into simulator, and if you have a good supply


a huge supply can help you to produce 200 Watts with the Dx amplifier.....you do not have to change voltage, or to tweak internally the amplifier currents.

Using the same circuit, with the difference that will be the inclusion of more three output pairs.... resulting four output pairs...each transistor using it's own emitter resistance (0.22) you will be able to hold strange speakers...those ones have very low impedance into some frequency.

Also connecting speakers in parallel, ...you will have 200 watts(197) to be divided into 4 speakers,...each one of them will receive 50 watts (8 ohms impedance speaker).

This means:

50 watts into 8 ohms
100 watts into 4 ohms
200 watts into 2 ohms

1 ohms is not fine yet... but i will try to increase the amplifier current to see if will be possible to not loose too much power using this ultra low load.

I have not tested.... i have doubts about the sonic qualities using many output pairs...... if i can remember..quality reduces.... but, as i did not make it, than i cannot say that as guarantee.

regards,

Carlos
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Old 5th June 2007, 09:09 PM   #1714
inex is offline inex  Netherlands
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Default Hi i have shorted the 10 Ohm resistor

But without the resistor there is still Oscilation.

I have been reading Graham Maynard his post about grounding again.

"Those who do not have sufficient experience with grounding requirements might end up facing problems" (sounds like me).

If the grounding is incorect, can it cause a dirty ground with HF signals that enter the output of the amplifier trough the zobel and cause oscilation's?

I didnt hear Distortions without the Zobel conected. (music was distorted then cut the zobel wire and the music was clean).

I am going to try some other ground wiring options later.
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Old 5th June 2007, 09:19 PM   #1715
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Default So...you are telling us that with zobel out you had better result?


This reinforces the idea that Graham had.

And makes me feel that was a message to you dear Inex.

A good idea is to try a better grounding.... this thread had all those informs detailed, by Klaas and by Graham... star grounding.

Klaas said that he is ready to help if needed, as he can speak your language.

Graham already sent you mail message, or, at least, forum message offering some help.

Of course i can help you, but facing all those strange things that is happening, i think the better is to send me those boards... register the value, explain to Holand mail what has inside, the reason why you are sending to brasil...because not informing those details, the package will return to your adress as "non regular export gods"

Then i will fix and return to your adress.... my belief is that an error still creating problems...or, at least fake transistors that have high gain under high current load.... a good transistor to Radio frequency that had the number replaced by audio transistor number.

Removing the feedback capacitor and oscilation start..this do not make any sense to me...also zobel remotion.

I have to say that those things are very strange to me.... also, i have to say that sometimes i think that you are kidding with me.... a very strange things that produces short circuits into my brain, as you are having the opposite results expected.

If you want my adress go to my mail:

panzertoo@yahoo.com

regards,

Carlos
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Old 6th June 2007, 07:17 AM   #1716
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Hi Inex,

That is now three aspects of your amplifier which function oppositely to what is expected.
I will go through my 'STAR' list line by line. If anyone has any other observations please don't be shy in discussing.

INPUT: The cable screen must go directly to the PCB without touching the chassis at any other point; ie. the input socket must be INSULATED from chassis.
INPUT FILTERING is on the PCB, none other should be added elsewhere.
NFB SENSING is on the PCB.
OUTPUT ZOBEL. The resistor must not be inductive. The C should not be sub-miniature and must exceed the rail to rail voltage rating. These components should be directly between the output stage node and the PCB ground; ie; not at the output sockets and NOT at the end of long wires.
LOUDSPEAKER wires must be kept away from the PCB, all input wires and power wires, and go to INSULATED output sockets/terminals.
POWER RAIL CAPACITORS should be connected directly to the PCB. If the PSU is not integral, then one pair of high value capacitors should be very close to the PCB and be separately connected directly to it.
POWER RAIL SUPPLIES. Must be connected directly to the PCB; the ground must NOT be connected via the chassis.
CHASSIS . There should be only one thick wire connection between the PCB and chassis at a convenient point.
SAFETY EARTH. This should go to the PCB ground, NOT the chassis.
OUTPUT NODE. This should be a single PCB wiring point between the output devices. The NFB sensing, the Zobel and the wire going to the loudspeaker terminals should all be connected together at this single low resistance conduction point.

As far as I am aware Greg's PCB covers all of these aspects, including the option for separating signal and power earths.

Inex, can I suggest you link out the 10 ohm ground resistor until you get on top of the oscillation problem.

Cheers ......... Graham.
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Old 6th June 2007, 07:29 AM   #1717
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Hi Carlos,

Way back in this thread I suggested listening without the series input resistor, and I know you did check it out Carlos.

It is possible that a value of 2k2 can actually allow NFB loop induced oscillation because the input base is not adequately controlled when its other limbs are not operating at low impedance either.

NFB on the emitter, and a C.dom on the collector can cause probs when the base impedance is too high. Reproduction can be affected even though the circuit might be quite stable.

I suggested 470 ohms. You have mentioned 180 ohms since then, though anyone looking at the circuit diagram without checking the parts list could still end up using 2k2.

I do not know what value of input resistor Inex is using.


Cheers .......... Graham.
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Old 6th June 2007, 08:41 AM   #1718
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Default The input resistance was reduced, also changed into the schematic, into the part list

changed into the 3D board image too.

Also i have published and i have made coments that the option to 180 ohms was because we already have another 180 ohms resistance.....because of that selected this value, not only to have a resistance into the input, covering holes because board was already made but also not to supress something started with the amplifier.

A short into the resistance point is better, but a small value as 180 ohms will not bother too.

Having same value of resistances...or, in other words, having an amplifier with not too much different values of resistances will make it more simple and more cheap...following the idea that started the whole thing.

So, dear Graham, i imagine that you forgot, or, at least had not readed, this was published and in a very clear way.....

In this image you can see that Inex is using another value.

Also under Inex board, were he had soldered the Miller capacitor and the feedback one, is not empty, as he perceived the amplifier better without them..... this continues very strange to me, and the opposite i have found in my home.

Soon the guilty will appear....there's a guilty part for sure, and the damned will appear sooner or latter.

I will be here to know the guilty one.

regards,

Carlos
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Old 6th June 2007, 08:42 AM   #1719
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Default The board image was published dear Graham.


I suspect you are not having too much time to read the thread.

here is Inex board once more.

regards,

Carlos
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Old 6th June 2007, 08:43 AM   #1720
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Default Here is the Inex board, the bottom view.


You can see that he have cleaned to produce the image...some transistors are not in place.

regards,

Carlos
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