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21st August 2012, 06:01 PM  #6911 
diyAudio Member
Join Date: Mar 2009

Ricardo, when you do not have access to bigger sized cables you can run some in parallel.
By the way i have the Paradise R2 now on for some days constantly and it is very hot weather. Under this conditions the heatsinks get very hot, but not extreme. PlusMinus 30V in is still safe but a little less would be better. Under my condittions running the CCSs on more current is certainly not a good idea. 
21st August 2012, 06:41 PM  #6912 
diyAudio Member

It's what I use for my amplifier interconnects
http://communications.draka.com/site...eets/hf27e.pdf
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Zion; Signature Transresistance CurrentFeedback BIGBT Amplifier; >>{{ Push }}<< or >>{{ Push }}<<. 
21st August 2012, 06:43 PM  #6913  
diyAudio Member

Quote:
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Zion; Signature Transresistance CurrentFeedback BIGBT Amplifier; >>{{ Push }}<< or >>{{ Push }}<<. 

21st August 2012, 09:13 PM  #6914  
diyAudio Member

Quote:
After some hours burning, everything is coming into place... detail is awesome but not overdone... there is harmony... voices are incredibly real... this build has real potential gentlemen.. just match the riaa caps between channels the best you can and use a preamp with double volume or a "balance" and reach paradise. I use only a 25watt amp with monitors and can hear really deep bass. This buil majors in diferentiation but in harmony...
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RC 

21st August 2012, 09:27 PM  #6915 
diyAudio Member

Just a last question.. this is so promissing I am planning to demo it to a friend that uses a goldenote tuscany (0.15mV cart)
I must eliminate input offset... can I use a 20k trimpot with two 40k resistors (one on each side) instead of the usual 100k trimpot ? I want to use vishay bulk metal trim pots and mouser only has 20k ones
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RC 
21st August 2012, 09:30 PM  #6916 
diyAudio Member
Join Date: Mar 2009

Thanks you Ricardo for this nice mini review. We will get more.
Just for learning, this is a mathematical analysis of a differential pair. I calculated my last Matrix over 30 years ago !The mathematical symmetry of the differential pair  ElectroYou 
21st August 2012, 09:33 PM  #6917 
diyAudio Member
Join Date: Mar 2009

Trimming should work the way you suggested. In the unlikely event that you get too little "leeway" you can introduce the desired asymmetry by using 30kOhm and 50kOhm on the other side or even more in the right direction.

21st August 2012, 10:12 PM  #6918 
diyAudio Member
Join Date: Mar 2009

On the other hand a 0.15mV cartridge should also have a low DC impedance. That also lowers input offset. Your DENON103 with 40 Ohm creates more offset. DC offset in the Paradise can be calculated. It is the NON cancelled base current times the DC impedance to ground. Under an ideal situation the NPN and PNP transistors at the input have the same Ube and the same Hfe. Then the input would be on zero volt. The current that flows out of the NPNs flows exactly into the PNPs ( conventional notation, in fact the current flows from minus to plus ). In reality there is a small difference in Ube, say the NPN have 0.65V and the PNP have 0.6505V, that is a mismatch of 0.0005V. This value alone does not tell us the DC offset. We also need the DC impedance of the cartridge plus the ballast resistor in parallel. The Denon DL103 plus 1kOhm ballast resistor gives 40//1000 = 38.46 Ohm. With transistors of Hfe = 500 and an idle of 20mA
we have a base current of around 40uA. How much DC offset do we get if the Ube´s are mismatched by 0.5mV ? I think Hesener did the calculation. i am too tired at the moment. We simply can work backwards by putting a 50 Ohm resistor to ground at the input ( cartridge non connected ) and measure across that resistor. We can also now measure each transistors Ube ( 4 x positive/ 4 and 4 x negative / 4 ). The transistors Ubes appear in parallel per polarity. We have taken some measures so that the Ube difference remains small. One is to use the BC327 and 337 transistors. They are very symmetrical concerning Ube. The other is the rather high emitter degeneration resistors. They lower the amount of Ube mismatch by current feedback. That works this way : the un linear Ube diode ( between base and emitter ) gets a series resistor. That series connection of Ube diode plus emitter resistor makes the whole chain more resistive. 
21st August 2012, 10:22 PM  #6919 
diyAudio Chief Moderator

What happens input voltage wise if one rail goes off due to some random failure during the preamp's lifetime?

21st August 2012, 10:27 PM  #6920 
diyAudio Member
Join Date: Mar 2009

I could go on and on. The idle current in the input transistors also flows in the emitter resistors minus the base current . Say we run each transitor on 5mA plus base current then 5ma flows in the 30 Ohm emitter resistors. That makes a resistive voltage drop of 30 x 0.005 = 150mV.

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