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Aksa Lender P-mos Hybrid Aleph (ALPHA) Amplifier
Aksa Lender P-mos Hybrid Aleph (ALPHA) Amplifier
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Old 13th February 2018, 08:46 PM   #341
roger57 is offline roger57  Canada
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Quote:
Originally Posted by xrk971 View Post
GB Status Update:



Qnty 64 PCBs total
Actually - if available, I will take 2 board sets. I have left my Paypal address in a PM. Thanks!
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Old 13th February 2018, 09:13 PM   #342
xrk971 is offline xrk971  United States
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Aksa Lender P-mos Hybrid Aleph (ALPHA) Amplifier
GB Status Update

Quote:
Pinocchio - 1 pair, Sent
6L6 - 1 pair, Sent
bk856er - 1 pair, Sent
Vunce - 2 pairs, Sent
Pcgab - 1 pair, Sent
jwjarch - 1 pair, Paid
vvs07 - 2 pairs, Paid
jacques antoine - 1 pair, Paid
GnuB - 1 pair, Paid
Kokanee - 2 pairs, Paid
zman01 - 1 pair, Paid
Bvtrinh - 1 pair, Paid
MshipmanPE - 1 pair, Paid
muthumuthiah - 1 pair, Paid
Schlomoff, 1 pair, paid
markus22ch - 1 pair, Paid
manniraj - 2 pair, Paid
Juntuin - 1 pair, Paid
Aatto - 1 pair, Paid
Wayne1 - 1 pair, Paid
Soelker - 1 pair, Paid
Touchdown - 1 pair, Paid
CFT - 1 pair, Paid
*roger57 - 1 pair, Invoice sent
Dane -1 pair, Paid
Gaborbela - 1 pair, Sent
wtl - 1 pair, Paid
Emynet - 1 pair, Paid
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Old 14th February 2018, 06:27 AM   #343
xrk971 is offline xrk971  United States
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Aksa Lender P-mos Hybrid Aleph (ALPHA) Amplifier
Default ALPHA 20 with SMPS / DC-DC / Cap Mx / CRC

I pulled the linear 400VA trafo and F6 PSU out of my case and installed the SMPS and DC-step-up PSU with cap multiplier. Well it is a lot smaller, lighter, and easy to install. I have it running at +/-26.0vdc rails and bias is still 1.3amps as governed by thr 0.47R on the source resistor/sense resistor fot the Aleph CCS. I am using a small heatsink from a Class AB LM3886 amp as the heatsinks for the cap Mx (about 10w dissipation per side). These are about the right sized heatsinks. The DC step up boards get warm and are aluminum so expect to be mounted to a heatsink.

It works ands plays music and sounds great when playing music, however, when no music playing I hear some noise and hum. I am chasing a small ground loop (about 1mVrms at the output). I like to see it below 0.2mVrms.

The cap Mx board has separate star grounds for the left and right channel. I bonded the separate two grounds per CRC together at the cap Mx output. I am not sure if that is the problem. The star point on the cap Mx

Here is a photo of the setup with +/-26v rais:
Aksa Lender P-mos Hybrid Aleph (ALPHA) Amplifier-alpha-20-smps-cap-mx-psu-01-jpg

Closeup of the cap Mx:
Aksa Lender P-mos Hybrid Aleph (ALPHA) Amplifier-alpha-20-smps-cap-mx-psu-02-closeup-jpg

I have the star ground connected to a CL60 NTC between the cap Mx and the chassis ground.

When I figure out the ground loop problem, this could be a very nice adjustable voltage Class A PSU.

I am wondering if the cap Mx should be split as in dual monoblocks? I am using the same SMPS and isolated cap Mx on the MoFo and it has no groundoops and is dead quiet. The ground loops drive me crazy.
Attached Images
File Type: jpg Alpha-20-with-SMPS-Cap-Mx-PSU-01.jpg (472.2 KB, 936 views)
File Type: jpg Alpha-20-with-SMPS-Cap-Mx-PSU-02-closeup.jpg (452.4 KB, 1231 views)
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Last edited by xrk971; 14th February 2018 at 06:43 AM.
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Old 14th February 2018, 08:31 AM   #344
JPS64 is offline JPS64  Germany
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Aksa Lender P-mos Hybrid Aleph (ALPHA) Amplifier
Hi X,

can you wire the attached sketch for better understanding?

JP
Attached Files
File Type: pdf Visio-GROUNDING.pdf (12.4 KB, 103 views)
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Old 14th February 2018, 11:07 AM   #345
prasi is offline prasi  India
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OK JP's suggestIon is good.
Is the input side cap value too low on cap MX to cause this?

Also is the signal input connected when this hum is observed?
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Old 14th February 2018, 03:14 PM   #346
xrk971 is offline xrk971  United States
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Quote:
Originally Posted by JPS64 View Post
Hi X,

can you wire the attached sketch for better understanding?

JP
Hi JP,
Thanks for offering the diagram - this is really helpful. What I see is that the amp is floating relative to earth gnd, but that's ok - the MoFo was the same way. When I connect the chassis gnd (even though floating relative to earth gnd) to the star hub, the noise is substantially less but Fluke 101 mV scale shows 1.1mV. I can hear slight hum and some HF white noise. Almost like there is some noise being generated in the Cap Mx. I ran out of 1uF film caps so using 0.1uF and 2R2 for Cap Mx snubber vs recommended 1uF and 1R5. Maybe that might be source of noise?

The CRC uses a 12 gauge solid copper wire bus for the ground in "U" shape. Should CRC been kept separate gnd for each rail? But then when it reaches amp it is one (0v) GND wire.

Attached is my marked up diagram. For my CRC I have 6k8 2W bleeder resistors from each rrail to 0v and 0.1uF 100V film caps bypass at the output.

Thanks again.

X

Btw, I moved it off the bench and into the listening room and it works to power the speakers very well (apart from noise if one presses ear to the speaker cone). Neat to see such a compact lightweight PSU compared to 12lb 400VA trafo.

Aksa Lender P-mos Hybrid Aleph (ALPHA) Amplifier-alpha20-smps-cap-mx-crc-wiring-diagram-built-xrk971-jpg
Attached Images
File Type: jpg ALPHA20-SMPS-Cap-Mx-CRC-Wiring-Diagram-As-Built-xrk971.jpg (322.5 KB, 411 views)
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Old 14th February 2018, 04:03 PM   #347
prasi is offline prasi  India
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Hi xrk,
How is signal gnd connected on amp pcb. Is there a 10ohm lifter?

Try to follow Bonsai recommendation for grounding.
Spk grnd to crc gnd or cap MX ground, to see if that's the case.

If everything fails put just the proper cap MX w/o crc and also check all individual blocks to see the problem source. Eg transformer and just cap MX as per bom supplying 2 channels and all gnds connected on cap MX output . It's the way Juma desIgned if I am not mistaken.

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Last edited by prasi; 14th February 2018 at 04:23 PM.
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Old 14th February 2018, 04:34 PM   #348
xrk971 is offline xrk971  United States
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Thanks, Prasi. Ok I will try without CRC and put all grounds from Star hub. Does that include putting the signal GND from RCA to star hub and skipping negative frommRCA to PCB. No 10ohm ground lift on PCB. Only CL60 thermistor to isolate chassis and 0v.

Here is Juma’s Schematic.
Click the image to open in full size.
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Old 14th February 2018, 05:02 PM   #349
prasi is offline prasi  India
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Quote:
Originally Posted by xrk971 View Post
Thanks, Prasi. Ok I will try without CRC and put all grounds from Star hub. Does that include putting the signal GND from RCA to star hub and skipping negative frommRCA to PCB. No 10ohm ground lift on PCB. Only CL60 thermistor to isolate chassis and 0v.

Here is Juma’s Schematic.
Click the image to open in full size.
I am sure you already seen this link by former brilliant member Bonsai. here it is anyway
Ground Loops: How to Wire-up an Audio Amplifier for Zero Hum and Noise

Also I always include 10ohm resistors and anti parallel diodes on amp for input if you remember my designs, whether or not amp designer includes them in the sch. These are nothing but HBRR and HBRL lifts as promulgated by D. Joffe and repeatedly suggested by Andrew T.
See Honey Badger sch too..

I request you to try to understand the problem block by block...Its helped me a lot before... I have a stereo LM1875 with integrated PSU and a separate tone control ckt fed by the same simple CT trafo and it works with absolute zero noise.

I have built it for sprite boombox in the kitchen for its owner. Full Range Speaker Photo Gallery
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Old 14th February 2018, 08:20 PM   #350
AKSA is offline AKSA  Australia
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Hi X,

Try disconnecting the RCA ground from the chassis - if it is presently connected - as the signal ground should be attached to fb shunt cap then through a 10R ground lifter to power ground ON THE MODULE PCB.

This should do it......

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