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Old 11th September 2012, 06:48 PM   #1041
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Default Cascode on BA-2 Front End

Is there any schematics diagram for cascoding the BA-2 front end?
Can we use as e reference the cascode section from F5 V3 schematics and implemented to work on BA-2?
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Old 11th September 2012, 07:08 PM   #1042
flg is offline flg  United States
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I don't remember any "official" schemo but up to 30-32V -V, NP has given the fearless amplifier builder the go-ahead. The top side (TAIL) of the diff pair uses a resistor to loose unecessary voltage...
Beyond that, 8-10V on the JFETs is a good number in my experience. BJT's are said to perform better as cascodes. You still need to bias the second stage appropriately...
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Old 12th September 2012, 12:24 AM   #1043
JimM is offline JimM  United States
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Nikosgar I will refer you the schematic I did and the amp I built see the following post in this thread. Post 279,416,417,420,449,453,454. See if this will get you started.
JimM
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Old 12th September 2012, 07:34 PM   #1044
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Quote:
Originally Posted by flg View Post
I don't remember any "official" schemo but up to 30-32V -V, NP has given the fearless amplifier builder the go-ahead. The top side (TAIL) of the diff pair uses a resistor to loose unecessary voltage...
Beyond that, 8-10V on the JFETs is a good number in my experience. BJT's are said to perform better as cascodes. You still need to bias the second stage appropriately...
Dear flg
I have already 30 V rails and want to go up to 50 V in order to have more power.

Thanks
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Old 12th September 2012, 07:53 PM   #1045
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JimM sold a few boards to me which I used in BA2 running about 55v.
I would see if he can help you out. they work fine.
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Old 12th September 2012, 08:25 PM   #1046
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Quote:
Originally Posted by JimM View Post
Nikosgar I will refer you the schematic I did and the amp I built see the following post in this thread. Post 279,416,417,420,449,453,454. See if this will get you started.
JimM
Dear JimM,
Thanks for pointing to the right direction.
I have seen your schematics and implementation (excellent & inspiring).
Questions
I have notice on your final schematic layout that for R203-R204 you are using different values (200 K & 150 K) why? (in your first schematics you had both on 200K).
According to the BA-2 manual those two are equal and are changing the gain (47.5K around 15db (initial setting by NP) - 100K /20db-150K /23db)
Can you post your PCB layout
Thanks for all the help and support
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Old 12th September 2012, 08:39 PM   #1047
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JimM sold a few boards to me which I used in BA2 running about 55v.
I would see if he can help you out. they work fine.
please !!!!! do !!!!!! that would be wonderful !!!!!! if you can
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Old 13th September 2012, 04:43 AM   #1048
JimM is offline JimM  United States
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nikosgar I think the final value I ended up with in R203 and R204 was 97.7k in both places, the 200k and 150k was wrong, it should have been one or the other in both places. I choose the 97.7k value to match the output of my benchmark DAC. If you will send me a P.M. with email address I will respond, and yes I do have som boards left.
JimM
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Old 13th September 2012, 07:40 PM   #1049
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nikosgar I think the final value I ended up with in R203 and R204 was 97.7k in both places, the 200k and 150k was wrong, it should have been one or the other in both places. I choose the 97.7k value to match the output of my benchmark DAC. If you will send me a P.M. with email address I will respond, and yes I do have som boards left.
JimM
Dear JimM
You got mail
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Old 26th February 2013, 11:58 PM   #1050
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Default Joes Ba2 please help

OK I am a green horn when it comes to building amps, I can read schematics but I need to know when mr pass says standard relating to capacitors or resistors as far as voltage wattage etc. is concerned what is standard? I can see in the schematics it calls for a 1000 uf cap but what is the voltage also the resistors the big ones say 3 watts the others must be the standard thing lol, I have the ba2 boards, I need to be pointed to a decent case and power supply, some links would help, I would like to thank anyone who helps me out ahead of time.
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