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Old 19th June 2007, 12:09 PM   #1881
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Default No need to apologize nephew Roender...be happy


Greg...those milivolts indication... 184 or something around that are my mistake...the correct voltage over those resistances are 70 milivolts or something around that.

We had double..so...i made the confusion to add both voltages...each 100 ohms resistance voltage.... and the feedback one has sligtly bigger current into the colector rail too.

Please, delete my error from the schematic...as i think that voltages referenced to the ground are more correct and more standard to provide folks.

And this one was WRONG...sorry folks...i am human...my error.

regards,

Carlos
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Dx Blame ST with a tube preamp. recorded with Xperia cell phone, https://www.youtube.com/watch?v=Qjs32J0gdj0; https://www.youtube.com/watch?v=nhrZ...vDnDhEpNv_XVxg
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Old 19th June 2007, 12:51 PM   #1882
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Carlos,

Your wish is my command, schematic updated.

usernamex,

Thanks for bringing the 184mV to our attention. If only fixing your amp was as easy as updating a schematic.

regards
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Old 19th June 2007, 12:55 PM   #1883
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Default Fine, thanks Mr Erskine.


Now that strange will be deleted and will not bother us anymore.

We will have to wait some hours, as Greg is busy and tomorrow he may delete those milivolts .

They were the voltage developed over those resistances.... the correct value is around 60 milivolts...as 600 microamperes are circulating into each transistor colector to emitter circuit.

Not a very usefull information that one..shows that you have the needed voltage drop over those resistances, prove that current are circulating from colector to emitter..also the real measurement made there allow you to conclude the current value in microamperes that are really circulating.

regards,

Carlos
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Dx Blame ST with a tube preamp. recorded with Xperia cell phone, https://www.youtube.com/watch?v=Qjs32J0gdj0; https://www.youtube.com/watch?v=nhrZ...vDnDhEpNv_XVxg
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Old 19th June 2007, 01:22 PM   #1884
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Hey Carlos, you don't have to call me Mr. It's not used between friends. I'm just trying to think when Mr is used in Australia, maybe kids addressing their teacher at school, it sort of has a connotation of someone being superior, which we know is not possible. Maybe used at very formal occasions like weddings or government meetings.

regards
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Old 19th June 2007, 02:55 PM   #1885
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Default Re: Fine, thanks Mr Erskine.

Quote:
Originally posted by destroyer X

....

They were the voltage developed over those resistances.... the correct value is around 60 milivolts...as 600 microamperes are circulating into each transistor colector to emitter circuit.

....
[/B]

Actualy, I was reading arround 600mV in that spot not 60mV ...
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Old 19th June 2007, 02:55 PM   #1886
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.... well, aprox 600mV to ground anyway ... It should be 60 on R4 and R8, not very clear from the schematic on the homepage that you should measure voltage drop on the resistor and not voltage refered to ground.
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Old 19th June 2007, 03:11 PM   #1887
kvholio is offline kvholio  Netherlands
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Same here, Greg. I only use Mr. when adressing old people, for whom i have great respect.

My DX using Greg's pcb is running stable and fine now for about two months.
Driving 4-8 ohms loudspeakers, using different pre-amps.
Using ugly high-capacitance ls-cables for bi-wiring.

I'm measuring 58 millivolts across 100r resistors (NOT referenced to ground) , looks fine.

Best regards,

Klaas
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Old 19th June 2007, 04:12 PM   #1888
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Default Yes guys.... so...you do not use Mr....no problem.


I am attaching the schematic showing voltages in red.

Those voltages were obtained after the amplifier was adjusted using 100 miliamperes and the offset was adjusted to 1.3 milivolts.

No signal at the input and speaker connected into the output...a 8 ohms speaker.

The voltage was 35 plus and 35 minus.

Those voltages are not absolutelly precise...mine units are not in my home and i have used the simulator to obtain those voltages...real life may be a little different as depends of many factors....many reasons that i will be tired to describe all them here, and now.

My prototype is beeing used now to develop another amplifier...a 330 watts unit over 2 ohms.... 250 watts over 4 ohms and 130 over 8 ohms...i am already tweaking and changing things as i want more power over 2 ohms because impedance deeps some speaker has.

Every voltage you found in your Dx amplifier circuit, with errors of 20 percent plus and 20 percent minus can be understood as normal... as this happens very often.

Off course, voltages plus 20 percent into the positive rail and less 20 percent in the negative rail, compared with the voltages provide means that you need to re-adjust your offset control.

The digital multimeter had its negative probe fixed on ground....transformer ground...the center tape.... and the positive probe was used to measure.

Exception was the VBE multiplier VBE voltage...and also the voltage from point A to C

I hope this will be help.

regards,

Carlos
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Dx Blame ST with a tube preamp. recorded with Xperia cell phone, https://www.youtube.com/watch?v=Qjs32J0gdj0; https://www.youtube.com/watch?v=nhrZ...vDnDhEpNv_XVxg
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Old 19th June 2007, 10:05 PM   #1889
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Please help

I'm having a few emails that the latest schematc is not appearing. Can a few people do a check for me.

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

Click on Amplifier Schematic in the table of contents, scroll down a bit, it should be dated GE20070619F, and no voltages near R4 amd R8.

Click on Contact in the table of contents, it should say "Page last updated: Wednesday, 20 June 2007".

regards
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Old 19th June 2007, 10:12 PM   #1890
sandyK is offline sandyK  Australia
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Default DX Amplifier

Greg
The VBE multiplier is there.
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