Aleph J illustrated build guide

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#666
invert or not , that's just matter of absolute phase of entire system

plenty of that written and accessible on web ; easy to change as flipping speaker cables is simple ...... or in preamp ....... super easy if balanced one is in question , just exchanging place of +/- phases
 
#667
Seavan said:
Can you help me with what input I should ground for RCA? Is it IN- that goes to ground and IN+ is an actual input? Thank you!
Click to expand...

I am not the expert, but I used IN+ from the RCA middle connector, and the shield to ground. Along those lines, I grounded the IN- for use with the RCA connector. I use a switch on the back panel. I send all three (IN+, IN-, and ground) to the XLR plug. I connected the IN+ and ground to the RCA plug, and the switch grounds the IN- when the switch points at the RCA jack.
 
#668
Bones13 said:
I am not the expert, but I used IN+ from the RCA middle connector, and the shield to ground. Along those lines, I grounded the IN- for use with the RCA connector. I use a switch on the back panel. I send all three (IN+, IN-, and ground) to the XLR plug. I connected the IN+ and ground to the RCA plug, and the switch grounds the IN- when the switch points at the RCA jack.
Click to expand...

I was thinking about something like this with using an XLR shorting plug if I can find one.
 
#672
So, I finally powered up one channel. I was able to set 0 out. However, the voltage on the output resistor at 68k R27 was 580mV. I had to rotate R27 almost to the end to read 350mV.

Also, I read about 20mV more on the other resistor, so, it's like 5% difference.

Is it all normal?

BTW, I am using 5U chassis and it does not seem to get too hot at 400mV.
 
#673
if you can't set intended Iq ( voltage across one source resistor - either R18 or R19 ) , increase value of resistor connected in series with R27 trimpot ; do not use R27B

then - if you can't set 0 output offset , and offset is positive - either increase R7 or use just R7- trimpot (without R7)

all that referring to sch in #179 ........ I can't find better one here :rofl:

whatever - be more specific , mentioning voltages and positions ; it always helps to keep things clear
 
#674
Zen Mod, thank you for clarification. I can set voltages. My concern is that 1) With R27 at 68k I get about 600mV, and to set 350mV I need to set R27 almost at its end position. 2) that voltage on R18/R19 differs by about 20mV (400mV, 420mV). I am just not sure if this is normal at all, but from your response it seems that it should be normal. BTW, I am using 6L6 kit of parts.

What is sch #179?
 
#675
sch from post #179

if you can't set low enough Iq (voltage across R18 or R19 ) - decrease value of resistor (R27A) connected directly in series with R27 trimpot

difference in voltage across two neighbor source resitors is OK if is in 5%
 
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#676
Remember that R27 actually set the AC current gain of the Aleph CCS. That it also effects bias is just a lucky happenstance.

If your heatsinks are up to it, (and with a 5U you should have little issue...) just set the 'bias' as high as you can until you A) can no longer zero the DC offset or B) have 65C at pin 2 of any Mosfet and 55C heatsinks.
 
#677
Jim, I don't see how R27 affects AC gain. The way I read the various articles, AC gain is set by the ratios of R15 to R24 and R16//R17 to R20//R21//R22//R23 (meaning the parallel values of the grouped resistors.) Usually we adjust only R15 to vary AC gain.
 
#680
regarding IRFP240 : you need to ask a guy from whom you bought them , for meaning of stickers

I presume/resume that , whoever was that , he sent you them clearly grouped by matching

that's only thing important - matching ....... class of Ugs is irrelevant

upper ones need to be matched together

lower ones need to be matched together

no need to match them up to down
 
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