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Old 25th February 2013, 05:49 AM   #1391
kroyin is offline kroyin  India
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Quote:
Originally Posted by Zen Mod View Post
both main boards need to be connected to PSU

daughter board will have power delivered by Divine Force itself

Divine indeed ..I was thinking about connecting as per pic2 (in+ in- holes on o/p boards to daughter boards) while it should be connected as as per pic 1

1 more JX for dummies question pls, two leads of RG, where does each end go (I was thinking spk terminal & star ground .. i know I'm a hazard )
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Old 11th March 2013, 03:56 PM   #1392
kroyin is offline kroyin  India
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Well I'm stuck ...

Build 1 channel. Driver board populated as per this

http://www.diyaudio.com/forums/attac...ect-ajxsch.jpg

All parts in the alternate current source left out. Rp & the t)rimmer left out of the bjt current source. Rs is 10k,Rg(across spk terminals & chassis gnd) 110 ohm(10r5watt+100r 3w

All Voltages spot on as per papa's J schematic.

Issue is 100mV(not 500mV) across all source resistors on both o/p boards & DC across both Rg is 20V.

Any thing that comes to mind (Rg it seems plays a big role, no Rg gives few mV across src resistors)
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Old 11th March 2013, 04:06 PM   #1393
Zen Mod is offline Zen Mod  Serbia
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put back Rp and trimmer and try to increase current through LTP ; reason for excessive offset ref. gnd is that you're not having enouigh voltage at drain resistors of LTP , resulting in not enough Ugs voltage for lower mosfets

if that not help enough .....put trimmers instead of these squared resistors ( written - on output boards )

if original ones are 390R , put 1k trimpots and fiddle with them

lower mosfets are not opened enough , so that's why you're having +20V offset

why I'm seeing all the time that anti-trimpot hysteria , especially from ppl not understanding either their role , or function of entire circuit ?

you guys are building knock-offs of NP's amps , and you're dicing fact that his amps are having trimpots in needed places ; even most "critical" ones

and he's not loosing sleep regarding that ........ in fact contrary to that
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Old 11th March 2013, 04:14 PM   #1394
kroyin is offline kroyin  India
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Thanks ZM, the trimmer & Rp was there,but took them off along with Q3 as part of debugging .
Ill put them back in & try the rest.

Thanks once again
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Old 13th March 2013, 03:02 PM   #1395
kroyin is offline kroyin  India
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Success ...whew..
Could get the original BJT based CCS to work but EUVL's alternate worked.

Relative DC is 35mV (between terminals) ,absolute DC 0.8V(terminal and ground) after 30mins.

One crib Q7 and Q8 on -ve half are way off (470 mV vs 650mV across src resistors)

Will put Q3 back in & rematch those 2 if required

Thanks to all and ZM specially.
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Old 13th March 2013, 03:27 PM   #1396
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Old 18th March 2013, 06:01 PM   #1397
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Played the channel today. For.Unbalanced the -ve input had to be grounded via a capacitor else the DC offset is in volts.

Running single channel with 16V rails (500va 13v secondary) all 8 0.47 resistors @540mV (+-15mV).

Very early days & STD disclaimer that my chain & preferences are diiferent from yours but couldn't help compare with F5T ... highs & mid JX better (marginally)
But F5T pulls ahead in bass by quite a bit (could be due to capacitance 120000uF for F5T 80000uF for AJX)
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Old 18th March 2013, 07:52 PM   #1398
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most probably difference in bass is due to nature of spks you're using

none of Alephs ( X or not ) is not really comparable with unusual beast , as 5T is

on easier driven spks difference will be smaller , but then you don't need beast for driving them

so - sort of backwards using old saying - don't use force , use a bigger hammer

F5T is a hammer
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Old 19th March 2013, 03:52 PM   #1399
kroyin is offline kroyin  India
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ZM...somehow the key lies in gain.
With AJ & F5 my gain is 10x, while with JX it is 6x.
I'm using unbalanced (-ve input grounded with 1uF cap) and no changes in any values w.r.t to original AJ schematic (other than using Jfet current source & not bjt)

How do I fix that pls....
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Old 19th March 2013, 06:13 PM   #1400
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just increase feedback resistors
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