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Old 19th April 2007, 08:54 AM   #921
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Default I do not know Markus..i am really ignorant about thermal track one


I have to read something about.

I cannot answer you that....i am sorry for that.

regards,

Carlos
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Old 19th April 2007, 08:57 AM   #922
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Default An European friend is starting to construct Dx amplifier to his close friends.


But those friends are "purists"..they do not use tone controls.... they hate those things....but...the amplifier must be adjusted to their listening room...if too much "muting" room.... absorbing high frequencies, you can compensate producing some treble boost..adjusted to your friend's taste.

Here is the idea.

Dx amplifier can be adjusted too.

regards,

Carlos
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Old 19th April 2007, 09:31 AM   #923
Nordic is offline Nordic  South Africa
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Hey Carlos, see that WWW button below your posts, click on user cp button at top right of page and put the address of the dx amp page in the URL field, to make that button link to the page....

Thanks I got your mail...
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Old 19th April 2007, 09:51 AM   #924
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Hi Nordic,

You must be a mind reader. I just emailed Carlos about linking his WWW button, even sent him the URL.

regards
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Old 19th April 2007, 10:52 AM   #925
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Default South of our planet say hello to you.

Practice, laboratory, local Electronic Teacher.

She works near the main University here.

Image is decent...but forum is rigid about those things.... full body, decent and dressed image can be found in my mail adress..just ask.

Do you like transistors?

Mikeks is trying to track her for more than a year long...ahahahah

Her name is Leila

panzertoo@yahoo.com

regards,

Carlos
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Old 19th April 2007, 03:35 PM   #926
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Default VBE multiplier board is optional and external to the main amplifier board.

There are three methods to adjust bias... some of them adjust and keep control of the bias.

The first one, the simplest one..use resistances, one fixed and another adjustable connected in series.

The second one, a little bit better, use three diodes and a small trimpot to adjustament.

The third, the most traditional one, to hard job and smaller heatsinks is the VBE multiplier.


Only the first one is supplied inside the board...there are holes to
trimpot and the resistance.

Using diodes, or VBE multiplier, you will have to travell wires, from the external board to the main board...

The diodes board and VBE multiplier board must be attached into the heatsink to receive heat.

regards,

Carlos
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Old 19th April 2007, 05:01 PM   #927
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Default Dx amplifier will be more safe using fuses.

Despite fuses can be a problem, they can help you to avoid fire if something goes short in the circuit...this is not impossible.

Fuses shows some resistance, and they use to create some sonic problems...but you can run a very thin wire from extreme to extreme, producing a guaranteed fuse of low resistance and low power in parallel with the main fuse.

Use 5 to 6 amperes fuses for the rails when working with 4 ohms....and 2.5 to 3 amperes fuses to the rails when working with 8 ohms speakers.

If your speaker has different impedance...or strange impedances, beeing very complex..prefer to use 5 to 6 amperes fuses.

The output must fuses too....as you can have big DC voltage there is something wrong happens..and this can happens in advance...while you wait the rail fuses to burn... this is a second guarantee.... alike plan B.

If you decide to use two supplies, one to each channel, use, at least, 4700uf each rail......if your supply is to be used for both channels, increase to 10000uf minimum rail capacitance.

Better to use twice of this as a guarantee that you will not have hum when some square wave continuous tone, full power, is reproduced.

2 Dx amplifiers will need less than 400 watts of power to the transformer primary circuit...so..using 120 volts, use 3.5 amps fuse...beeing 220 AC volts your mains voltage, reduce the fuse to 1.5A, or 1.75A or even 2 amperes.

regards,

Carlos
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Old 19th April 2007, 06:42 PM   #928
kvholio is offline kvholio  Netherlands
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I knew the b&w's weren't the easiest loudspeakers to drive and have a fairly low efficiency, but i didn't know it was that bad.
I will try using fast fuses between ps-caps and amplifier of 5A first, and see if these will hold.
Well, lesson learned i guess

My previous experiences with the amplifier showed it was very unwilling to go into violent oscillation, even using small values for miller-cap and feedback-cap.
I have tested into heavy clipping-levels ( the sine-wave looked more like a square-wave on the scope).

A picture of one of the woofers, 18 cm kevlar-drivers with a BIG magnet.
Also you can see some corrosion on the cast frame , they're 29 years old.
Click the image to open in full size.

At least i've learned that the many good people in this thread will provide excellent support when needed

Best regards,

Klaas
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Old 19th April 2007, 08:20 PM   #929
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Default Yes....Graham is around...and others are sniffing, ready to jump in to help us

So....no worries to make mistakes...we are protected...they will come to help us...to correct things and to adjust things.

Fuse is something that we know if they are good or bad after some burns...some accident and explosion...he is a very strange protector....he burns to tell you that you are ...... well....that is it.

You can guarantee that your fuse will behave fine related resistance it will show when new and that one appear with time.

Solder a very thing piece of wire...dismounting cables and having the thin wire that is use for shield..... sold this one into the fuse from extreme to extreme...or...sold it into the fuse socket...or...sold it between socket terminals...this will be a guarantee of low resistance...if current appear...too much current that will make the fuse blow...as it has bigger resistance than that wire, it will burn first...and that small wire...that cannot hold more than 300 miliamps will melt after the fuse...so..protection will be there..working fine...and audio will cross rails without resistances in series that may affect the power output.

Good speaker...and opened in its back...more back pressure, and better to use inverted or omnidirectional.

Observe the part that seems to be a long neck...between the diafragm and the coil....watch if you have wavings there...if positive...use varnish to make that part more resistant.

regards,

Carlos
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Old 19th April 2007, 08:49 PM   #930
Nordic is offline Nordic  South Africa
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why not just parallel a 300ma slowblow fuse then?
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