Aleph J illustrated build guide

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#9,401
Dr Greenthumb said:
I was digging through old posts old posts and found that this amp is not supposed to invert signal. On the left channel, I have to swap the + and - around, the right channel is normal. Any thoughts as to why one channel is inverted and the other isn't?
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How did you determine that one channel is inverted from the other?

Check input and output wiring.
 
#9,403
ItsAllInMyHead said:
How did you determine that one channel is inverted from the other?

Check input and output wiring.
Click to expand...
The left channel has had the +/- reversed with 4 pairs of speakers. I haven't had to do this with other amps.

My amp is set up as dual mono. I ran left signal/speaker with right amp and right signal/speaker on left amp. The speaker on the left had to have +/- returned to normal and the right speaker had to have +/- switched around.
 
#9,405
KevinHeem said:
@Dr Greenthumb
Looking back at post #9315 it looks like your inputs are reversed on one channel. Also, shouldn't input "-" be connected to ground if using a SE input?
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The photo makes it look like the inputs are switched.

As far as the -IN being grounded, my understanding is that it isn't supposed to be. I tried putting in a jumper from -IN to ground and it didn't make any difference in sound.
 
#9,407
Dr Greenthumb said:
The left channel has had the +/- reversed with 4 pairs of speakers. I haven't had to do this with other amps.

My amp is set up as dual mono. I ran left signal/speaker with right amp and right signal/speaker on left amp. The speaker on the left had to have +/- returned to normal and the right speaker had to have +/- switched around.
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I asked how you determined that one channel was out of phase. I understand what you've done to react to thinking that one channel is out of phase with the other... but how did you measure it?

Dual mono (should) make no difference to phasing. Irrelevant.

I haven't read back to all your previous posts, but it sounds like your speaker set-up / wiring is different from the norm. Running 8 speakers? My guess is some sort of surround configuration using some sort of a mic set-up / electronics to set the levels between them with multiple amps. Those types of processors get it wrong all the time, and generally... but not always... pick up a lot of room effects. Or ... are you saying that you've tried 4 different type of speakers in stereo... and just by sound alone you think one channel is out of phase? Something else?

tl;dr - unless you use a scope or other means to directly measure the input to output phasing of the specific channel in question... we really don't know what you're dealing with. If you're happy with the way it works with the wires flipped... leave it alone. No reason to pursue it any further.

Also... you really should put in that jumper. You don't have to, but ... I would. Read back into the thread for what it does and why...
 
#9,412
Hi, I did listens of the Aleph J with a variety of commercial friends speakers but they didn't fit. The best result was with a Diy 2-way closed box but 4 ohms. Elsewhere the J didn't modulate low frequencies very well. The midrange and highs are very good, but I think 8 ohm speakers are required for it.
 
#9,413
Finally got around to working on my Aleph J again after setting it aside for a year or so. The left channel is working fine, biased up properly, and plays music, however, the right channel is like a dead short on the power supply. I compared both boards. All devices are the same and in the same orientation. LEDs are mounted correctly. No shorts between the MOSFETs and the heatsinks. No solder bridges. I have nude Vishay resistors mounted in the R11 and R12 locations and it is obvious that they became very hot for the few seconds that I had power to the board. These are the only devices that look damaged. They still measure 220 ohms but obviously cooked. Any ideas what could be wrong?
 
#9,414
short between mosfets and hsink?

all components in proper value/type in proper place

all wires in proper place

having working channel - poke with diode/buzzer test every semiconductor - compare bad with good channel; if in doubt - pull part out, measure/test

besides that - pictures ...... you know the drill
 
#9,415
ItsAllInMyHead said:
@Dr Greenthumb And ... if you display the input and output on your scope simultaneously (for both channels) ... is one channel inverting phase as you've surmised...

Edited to add - You may as well do a quick gain calculation while they're hooked up, since one channel has a lower output.
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I checked input and output simultaneously first on the left and then on the right. Both in phase with input. When checking both left and right output at same time, everything lines up. Tests were done with -IN grounded.

When the right channel has 1V output, the left has 0.970V. To get the left to 1V, I barely moved volume on pre-amp - literally just tapped it.

Scoping just the inputs showed the right channel having 15mV more than the left coming from the pre-amp (Conrad Johnson PV11). Swapping the line stage tubes around created a difference of 35mV, favoring the left. I rolled a few sets of tubes this afternoon and got the difference down to 5mV.
 
#9,418
First attempt at an Aleph J. Boards complete with the exception of 7pf silver mica C5 and 200R for R30. Toshiba's from Punkydawgs and employed 50V electrolytic capacitors having read tons here and the ubiquitous raving expecting long term play. Plan to drop these into the 4U chassis with upgraded heat sinks in place of the dual mono parallel ACA boards currently residing. Last two components due in mid week along with nice input hookup solid core wire.

Early morning plein aire soldering session followed by flux cleaning. With Gratitude to you all.

AJ.jpg
 
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