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Old 7th October 2017, 02:09 PM   #4051
slav is offline slav
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I have powered one channel of Paradise , fair amount of output fluctuation +/-80mV with 10k on the input , covered input stage , input sits at 0mV , pin 6 ~1.3V .
I'm not sure if Calvins are pulling as much current as required , I have 16mA going through R6&R11 , power supplies push 150mA per rail , all voltages within the range , where to look , shall I increase Calvins current ?
Many thanks
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Old 8th October 2017, 07:11 AM   #4052
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These buffers are driving me crazy , fired up the other one and all LEDs apart from the bank under heatsink are not lightning , high and random voltage between in and out of the buffer , very high current through the buffer .
I swapped all transistors and now I have ~50mA through 2R2 , LEDs lightning up , not adjustable in-out ~30mV .
Both Paradise boards behave in the same way depending which Calvin connected , drawing either 19mA or 50mA respectively .
Do I need to play with R5 and R6 to set the current ?
Anyone?
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Old 8th October 2017, 09:25 AM   #4053
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I replaced R6 and R11 on high current board and it pulls now ~30mA with 25mA going through 2SA1381 but trimpot adjustment takes me only down to 30mV .
I havent matched PF5102 , would it be that , do I need to match j107 as well?

Last edited by slav; 8th October 2017 at 09:33 AM.
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Old 8th October 2017, 12:43 PM   #4054
sq225917 is offline sq225917  United Kingdom
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Kamis, Q97 and Q98, it really doesn't matter. Match them if you like, you won't hear or measure a difference.

Q99 c 8 mA, matched against other channel.

Input bias really needs to be trimmed with loading resistor and cartridge attached. It doesn't drift once set.
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Old 8th October 2017, 12:54 PM   #4055
sq225917 is offline sq225917  United Kingdom
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R 5 and R7 surely?


Slav, the input transistors and their cascodes need matching. It's easier to set the Calvins up separately, with the 100k R15 fitted. Once you have them dialled remove R15 and fit to the Paradise.

IDSS 8-8.5mA for the input transistor. Match them for


You'll not get steady output from the Paradise until you have about 100 hours on the main boards and they are thermally stable, ie cased up. The large lytics take a long time to form and settle with no leakage.
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Old 8th October 2017, 01:24 PM   #4056
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I increased R6&R11 as they define how much current is flowing through the whole circuit , R5&R7 define how current splits between jfets and bipolar ,
I shall fiddle bit more later
Any helpful circuit to match input transistors and cascodes , Atlas DCA55 is bit useless in this case?
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Old 8th October 2017, 01:32 PM   #4057
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What should I aim for when adjusting Calvins , total current of 30mA with 4-5mA through cascode?
What baffles me no adjustment below 30mV
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Old 8th October 2017, 03:32 PM   #4058
slav is offline slav
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Quote:
Originally Posted by sq225917 View Post
It's easier to set the Calvins up separately, with the 100k R15 fitted. Once you have them dialled remove R15 and fit to the Paradise.
.
Do you mean disconnect in/out from the board and plug R15/100k?
I've tried to lower R5 and R7 , went down to 2R2 same as R6 R11 on the working/adjustable buffer and overal current is 25.5mA with 4.5mA going to jfets , don't seem to be right .
I have ordered some matched PF5102 , question remains what's best way to match 2SA1381 and J107?
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Old 17th October 2017, 08:51 PM   #4059
slav is offline slav
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Just a quick question regarding transistor matching for Calvin buffer ,
should they be matched for Idss @Vgs=0V and have similar threshold voltage - Vth ?
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Old 19th October 2017, 06:48 AM   #4060
slav is offline slav
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Common people , there must be at least couple hundred working Calvin boards,any input/advise on transistor matching?
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