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Old 2nd January 2013, 04:20 PM   #1631
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I can get ahold of some 2SC1819 for VAS position. With an Ic of 100mA, is that enough for that position?

Regards,
Mart.
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Old 2nd January 2013, 05:26 PM   #1632
BMW850 is offline BMW850  Netherlands
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It is always difficult to describe how the amplifier now sounds, but I will try.
The sound is now quite open the bas is very very deep and tight.
The amp sounds now NOT more laid back, and there is much more emotion in music what I find very important.
The Dx Blame MKIII-Hx can play so hard without that it irritates but dangerous for the tweeters.
This was a huge difference than before.

The last modifications will be and my 2 big 2 x 42V 2000VA torroids with or without the Mundorf 47000uf / 80VDC, MLytic® HC
And the switch from 180pf to 100pf.
Can someone tell me what the sound of the amplifier will be, if I solder the 100pf silver mica?

All the best wishes for 2013
Regards,
Rudy
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Old 2nd January 2013, 07:14 PM   #1633
JMFahey is online now JMFahey  Argentina
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Pão doce Bauducco?
*Esse* é o "componente segredo"?

Parabéns e Feliz Ano Novo

PS: nem vou falar da beleza da namorada para não causar ciúmes, he he.
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Old 3rd January 2013, 12:28 AM   #1634
evette is offline evette  Canada
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More than enough. Evette
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Old 3rd January 2013, 12:31 AM   #1635
bonfis is offline bonfis  United States
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Quote:
Originally Posted by BMW850 View Post
It is always difficult to describe how the amplifier now sounds, but I will try.
The sound is now quite open the bas is very very deep and tight.
The amp sounds now NOT more laid back, and there is much more emotion in music what I find very important.
The Dx Blame MKIII-Hx can play so hard without that it irritates but dangerous for the tweeters.
This was a huge difference than before.

The last modifications will be and my 2 big 2 x 42V 2000VA torroids with or without the Mundorf 47000uf / 80VDC, MLytic® HC
And the switch from 180pf to 100pf.
Can someone tell me what the sound of the amplifier will be, if I solder the 100pf silver mica?

All the best wishes for 2013
Regards,
Rudy
Hi Rudy-
My opinion is that no one can answer your question because no one has your ears or your brain except you. I encourage you to make this change and evaluate the results for yourself. From a technical standpoint the slew rate of your amp should increase with the change in Cdom. Whether this will be audible to you is unknown. So you need to make the change if you want to know.

Happy New Year and regards,
Steve
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Old 3rd January 2013, 12:55 AM   #1636
bonfis is offline bonfis  United States
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Originally Posted by canonnica View Post
I just ordered some 2SA968B & 2SC2238B from Littlediode (UK). I don't know what to expect as if they're genuine, but I'll give them a try.

These will take the spots held by MJE15030&31 at the CCS, VAS & driver positions.

Mart.
Hi Martin-
I recently installed the 2SD669A in the VAS position and the 2SB649A in the CCS. These are used in several Randy Slone designs and I had several on hand. I also like the fact that the collector-base capacitance is lower (14pf) than many of the other candidates. I did not change the drivers. Output clipping is now symmetrical until about 4 Khz where some negative side rail sticking appears. The "dent" was previously eliminated by removing the BS cap.

Steve
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Old 3rd January 2013, 09:28 PM   #1637
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Because no audio is sent through the CCS, is it important to pair the CCS transistor with the VAS transistor? Or any mix can be done?
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Old 4th January 2013, 11:18 AM   #1638
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Default I do not think so....one works as a fixed resistor, the CCS does not operate ...

dinamically...almost all transistors manufactured in this world, that is able to face the voltage we have there in our circuit (from colector to emitter) and that is able to face the current we have there (from colector to emitter) will fit the task as a CCS driver transistor..have to respect only if NPN or PNP.

But the VAS transistor is the most important transistor we have in our amplifier, it is responsible by the generation of all swing of voltage that gonna appear in the output, this one operates dinamically and is not making pair with anyone..it stand alone just feeded by the first VAS stage.

I do not think you should use pairs...this will not change anything...but if you want this way..also will not harm the circuit.

CCS represents a fixed resistor... a kind of fixed resistor that does not suffer the consequences of load variations.... the current is stable...so...it is a clever resistor let's say this way..but does not operate dinamically in high frequencies alike audio...it works in very low frequency, almost zero, just controling the current...it is more a power source than an amplifier.

The VAS goes dinamically, beeing the most important transistor in the circuit...it also senses the output variation of impedance...this stage is the most important, and the amplifier performance also depends, a lot, on this circuit...this transistor can increase or decrease the power amplifier performance.... transconductance happens there too, as in the differential pair you have swing of current, no voltage swing...you cannot see waveform in the differential pair load using scope...but the VAS "generates" all the voltage swing that gonna be transfered to the output that will only increase current following the voltage generated.

Several years ago i have used these transistors (2SD669A and 2SB649A).... a very high gain transistor but die like a bird....they die easy..fell down almost dead when sick...poor bird close eyes and fell down..when reach the floor it is already dead..... this transistor die so easy as a bird... i have lost all six 6 pairs i had...this seems, at least to me, they are not that reliable...or strong...or resistant.

For they are good transistor...no doubts about that.... my experience with them was not so good as they have not survived.. but when working, produced nice sonics, had excelent gain and very low noise..high frequency response was excelent.

regards,

Carlos
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Last edited by destroyer X; 4th January 2013 at 11:29 AM.
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Old 4th January 2013, 11:58 AM   #1639
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Thanks Carlos for that detailed explanation
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Old 4th January 2013, 12:21 PM   #1640
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Default You are welcome...you know we like one each other

regards,

Carlos
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