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Old 30th June 2009, 05:10 PM   #1781
Malka07 is offline Malka07  England
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Hi Diomedian,

Yes i am using an 18vdc wallwart. I basically just ran a wire from the negative rail to the chassis. The increase in sound quality improved by a big margin articulation became much clearer, as did instruments and there positions, also bass lines are much easier to follow. So would definetely recommend grounding the chassis. Well thats my experience with it anyway. Also lowering the 1k resistors to 330ohm help further clear things up and bass seems much tighter.

Alon
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Old 30th June 2009, 06:07 PM   #1782
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Quote:
Originally posted by Malka07

Does anyone know how low i can take these resistors without introducing oscillation? I have read somewhere that 220ohm should be ok. Can anyone clarify this for me please?
It took me quite a while, but I finally found Papa's recommendation - back on page 31, our friend ABO shorted the output resistor and reduced the input to 100R. Papa noted that he didn't recommend shorting the output but would "recommend exploring lower values, such as 221 ohms."

Thanks for the pointer, Malka07!

-j
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Old 30th June 2009, 07:13 PM   #1783
Malka07 is offline Malka07  England
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Thanks Diomedian,

I knew i had seen that before but couldnt remember the exact value and where in this huge thread it was!!!

Thanks for finding that for me.

Has anyone else noticed benifits from using 220ohm resistors for input and ouput?
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Old 30th June 2009, 10:04 PM   #1784
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Quote:
Originally posted by Malka07
So would definetely recommend grounding the chassis. Well thats my experience with it anyway.
Grounding the chassis is important.

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Old 30th June 2009, 11:27 PM   #1785
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Nelson,

While you are on the topic, what is the best method to ground the chassis?

Thanks,
Keith Lockwood

Sam with the showing scalp flat top, particular about the point it made.

F.Z.

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Old 30th June 2009, 11:56 PM   #1786
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Malko,

I would turn your whole pcb around 180* so the connection wires are much shorter - the pot can easily be connected to the front plate with a simple "shaft extender"
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Old 1st July 2009, 12:14 AM   #1787
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Just what I needed. Thanks_ Audiojoy!
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Old 1st July 2009, 10:08 AM   #1788
Malka07 is offline Malka07  England
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Quote:
Originally posted by jameshillj
Malko,

I would turn your whole pcb around 180* so the connection wires are much shorter - the pot can easily be connected to the front plate with a simple "shaft extender"
Thanks James,

I had not thought of that....and just when i thought i was almost finished with my b1!!! Seems like there is always something to change.
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Old 2nd July 2009, 08:55 PM   #1789
Bengali is offline Bengali  United States
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Default B1 DC on output

Hi,

I just built the B1 using Pass pcb.

When I turn on the B1, I see 2VDC on the output, this is
after the 10uF coupling cap After few seconds, it will
drop down to 0V. Is this normal? In this case, I would
get big turn on thump?

I'm using LM1084 VR set and output measures 18.5VDC for
psu.

I'm using 1000uF 100V x2 since that's what I have on hand
for filter caps.

Is JFET JBOZ (single fet from NP) sound quality same as B1?
If I build JBOZ, it's pretty much the same SQ but with more gain?

thanks!

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Old 2nd July 2009, 09:28 PM   #1790
Jaac is offline Jaac  Netherlands
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What is your load on the output ?
if you have couple of meg and no real load then it is normal i had that issue too. Try putting some load after the cap like your amp or first some 20k resistors.

Be brave and good luck
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