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Old 18th May 2007, 02:23 PM   #1481
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Default Klaas made his transistors share temperature


Here is the image,

regards,

Carlos
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Old 18th May 2007, 02:24 PM   #1482
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Default Klaas VBE multiplier...here is the image


Attached,

regards,

Carlos
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Old 18th May 2007, 02:34 PM   #1483
rabbitz is offline rabbitz  Australia
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Default Re: Re: Re: And how are you Rabbitz... i am still thinking on you

Quote:
Originally posted by Greg Erskine

I doooonnnn't doooo thiiiiinnnnngs faaaaasssssttttt.
I have 2 speeds.... flat out or stop.
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Old 18th May 2007, 07:01 PM   #1484
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Default How are you Rabbitz....some fingers are better and others not?


Tell me, please, how are you?

Do you have your home coordinates...those informs of global positioning.... Google earth positioning..

Please, send my your location....the place name..not the entire adress..the town and Australia position.

Do this directly Rabbitz, please.

panzertoo@yahoo.com

regards,

Carlos
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Old 18th May 2007, 07:27 PM   #1485
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Default Last january, the Dx amplifier was under testings.


Output coil was used....different values tested...including air core.

Different Current to VAS...different biasing points.

Different rail resistances

R/C filter between differential colectors

Different drivers emitter loads

Many types of input capacitors...different values too

Supression of the 2K2 input resistance was tested too.

regards,

Carlos
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Old 18th May 2007, 07:29 PM   #1486
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Default No thermal compensation was used early days


And worked fine without them.

You see in this image the heatsink temperature beeing measured...the amplifier was beeing playing normal volume for 20 minutes..... environment temperature was 29 celsius.

regards,

Carlos
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Old 18th May 2007, 07:32 PM   #1487
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Default Heatsink was huge for one channel only.


You can see the image...bigger size is something around 20 centimeters....fins are 8 centimeters..... width maybe 18 centimeters.

regards,

Carlos
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Old 18th May 2007, 07:34 PM   #1488
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Default Dx supply is working fine.


I am very proud of this supply...it resulted excelent.

Schematic is the one posted at the home page.

My prototype produces 110 watts undistorted....and could reach 160 watts during short time peaks with reasonable (tollerable, suportable...not enormous) distortion.

regards,

Carlos
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Old 18th May 2007, 09:39 PM   #1489
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Hi Andrew,

Re your post#1470 (freq of R Vibracion AM station often DXed in UK). I did not see this before I entered my post#1474.

If the filter were stand alone and separately buffered I might go along with your generalised figure, but over the years I have found that you can hear what would be deemed a sensible input filter when it is simultaneously used in direct connection to differential/input bipolars.
I feel it is likely your figures would better match a fet input stage.

You ask >>It would appear that a lower value of series resistor and possibly higher value of grounding capacitor would both help in lowering the AC impedance seen by the base of the input transistor. Is that correct? <>

I would think that correct, but sometimes there can be oscillation on a previosly stable circuit having only a small stability margin.

You ask >>has anyone tried moving C14 (the Miller comp cap) from the collector of Q1 to the base of Q2? <<

Carlos' amplifier has fewer high gain phase changing stages within the closed loop, and so I see this technique for stabilisation being worse. Carlos checked out to optimise the NFB capacitor value, and so I could imagine connecting another 22pF at the base of Q2 would mean he would need to re-check all capacitor values anyway.

Actually the method of stabilisation you enquire about is more useful for circuits containing additional phase changing devices, like a differential mirror and a Darlington VAS, or more complex output stage complementaries, because it can improve stability.

However Carlos' Dx is already quite stable, so it is better off without any of inner loop phase change that such a C.dom between Q3 collector and Q2 base will cause.

You ask >>
Does it improve the sound?
Would other stability components be required to implement this change? <<

I suggest it would degrade reproduction; and,
This connection will reduce the closed loop bandwidth, but I cannot be sure about stability. Values need to set up in a real life amplifier circuit.

Thus I must echo Carlos' suggestion that you give it a try and let us know.

Hi Nordic,
When you are quite used to the sound of your Dx amplifiers, why not try linking out the 2k2 input resistors beneath the boards and let us know if you hear anything.
Maybe there is that little bit more for you to be happy about, as long as the wisdom teeth are not playing tricks with your hearing.

Cheers ....... Graham.
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Old 18th May 2007, 09:48 PM   #1490
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Default Yes Nordic...just a link to check...make it in one channel and let the other original


Just link and listen.

You will have an increase in level....carefull not to confuse level of treble with quality of treble.

I am remembering that because i feel very difficult to "separate" those two things when they happens simultaneously...it is normal for us... humans...to perceive the one is louder as better.

Because of that, A to B comparison testings need carefull adjustments related levels.

regards,

Carlos
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