Babbelfish J PCBs

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#401
cviller said:
Thanks Choky for helping me with this!

I tried to move all ground wires to gnd terminal on my psu board and only running one channel but I didn't see any noticeable improvements, but I discovered something else. There is a very large difference in my CCS transistors source resistor voltages. One reads 450mV whilst the other is 200mV (across a 0.47 resistor).

I did match all my transistors to within 0.01V at 1A and 20sek. Could it be my resistors or should I try with some different transistors? The gate voltages were the same in reference to ground.
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recheck resistors , mebbe you have R22 disguised as R47 😉

if they are the same-change mosfet.......and don't scratch a head about this....

regarding hum...........if rearranging gnd connections didn't solve your problem- you must play further with cap bank..........try with PSUd.....and- your Fish deserve chokes instead resistors .............
 
#404
Ripple

Hi Cviller,

the problem is the current source for the input J-Fets. You can not measure the ripple voltage here because it is a ripple current:att'n:

If you think, you have a time constant 33k x 0,22uF you are wrong. The input impedance of this CCS is very low, so you have no filtering at all.

I would recommend to use 10k + 22k and to tap this arrangement with a 100uF cap.

Ivo
 
#405
Re: Ripple

Ila said:
Hi Cviller,

the problem is the current source for the input J-Fets. You can not measure the ripple voltage here because it is a ripple current:att'n:

If you think, you have a time constant 33k x 0,22uF you are wrong. The input impedance of this CCS is very low, so you have no filtering at all.

I would recommend to use 10k + 22k and to tap this arrangement with a 100uF cap.

Ivo
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Thanks for your idea. I just did a quick sketch to make sure that I understand you correctly the 20k resistor should be 22k - too quick there.

Wouldn't this 100u give a massive turn on thumb?
 

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#409
Hi cviller,

:bawling: :bawling: :bawling: ,sorry. I do not believe that the output CCS is the reason, it must be something else.

Another tip:

- The PNP-transistors in the input CCS are false connected. You have reversed the emitter/collector. The transistors are still operating but with a very low current gain.
- Try lower feedback resistors (scale down a bit)

Good luck and let me know.

Ivo
 
#411
Ila said:
Hi cviller,
- The PNP-transistors in the input CCS are false connected. You have reversed the emitter/collector. The transistors are still operating but with a very low current gain.
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Do you have any idea how many times I have checked this - datasheet->layout->pcb??? many!
As I wrote in my hum thread - I discovered that one pnp was burned. So even though I couldn't see the error in layout - I tried to flip the pair to the other side and now I have one channel dead silent!!!!!
Thanks for all the help!
 
#412
cviller said:



Do you have any idea how many times I have checked this - datasheet->layout->pcb??? many!
As I wrote in my hum thread - I discovered that one pnp was burned. So even though I couldn't see the error in layout - I tried to flip the pair to the other side and now I have one channel dead silent!!!!!
Thanks for all the help!
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what you mean-"dead silent"
making music without hum,or not even making music?

I hope first......
 
#416
Malotron said:
Is an AlephX-Babblefish pcb a glimmer in Oly's eye...maybe? :tons:
-Mal
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not yet ;
that will wait a little ;
I hope that I'll soon receive pair of Aleph X pcbs ,gift from Demolition Man himself.............Mr. AR2 :devilr:
they will be -fer sure- excellent test bed for Babelfish JX ........ which I plan in near future .
anyway-fresh from Oly's Cousine- pcbs for bal or unbal Babelfish J (pic attached) .
I'll make final negotiation on Monday for first (little) batch production ........
 

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#419
Re: Balanced Babbelfish

GeorgeBoles said:
Hi there ZenChoky,

Which of the many schematics in this thread is the new board based upon? Would it be from Post#92?

Regards,
George.
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tonight .....please 😉

I hope I hope I hope that I'll manage tomorrow at last that Paypal account I need for small Babelfish J pcb batch........in glory of Papa 😉

I have all opportunities to make pcbs of exceptional quality......but some lousy byrocratic things (as one that Serbia is not in Paypal covering) really bothers me.....

I'll squeeze schmtc pic later tonight
 
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