Aksa Lender P-MOS Hybrid Aleph (ALPHA) Amplifier

[danny_66]

OK Vunce, I get it now
you didn't connect the signal ground wire directly to the "IN" pad but you added a 15r in series with the signal "IN" pad on the PCB.

Use the thick one that's easy to install.

 

[Vunce]

Thanks for the info Juntuin
I was not prepared to have such a productive informative learning session from everyone today! The weather is beautiful outside today and I’m inside on a device reading and messaging......EXACTLY what I yell at my kids for

 

[Juntuin]

Thanks for the info Juntuin
I was not prepared to have such a productive informative learning session from everyone today! The weather is beautiful outside today and I’m inside on a device reading and messaging......EXACTLY what I yell at my kids for

Indeed, some intensive reading, learning and building today

Go and grab some fresh air!

Can someone confirm that will I destroy something lifting whole amp's ground? As stated, lifting signal ground didn't provide any help for me, don't know why.

 

[danny_66]

Hi Danny, just edited my post at first I tried to lift signal ground only with 10r, it did not had any effect! That's why I was so surprised when lifting speaker return also helped.

That's probably because the shunt feedback(c111,c115) is still not lifted and connected to PS ground.
For a proper signal lift the input signal and the shunt feedback need to be lifted, local PS decoupling and speaker return should not be lifted.
See the schematic of the BB.

Here it's lousy weather

Regards,
Danny

 

[Vunce]

Indeed, some intensive reading, learning and building today

Now it’s time to crank the volume and enjoy.
The ALPHA20 totally ROCKS!!!!!

 

[thimios]

By the way, ALL should look the power inlet at AV Receivers.

An example:

[URL="https://www.pioneerelectronics.com/StaticFiles/Custom%20Install/Detailed%20Product%20Information/AV%20Receivers/SC-65_Back.jpg"]https://www.pioneerelectronics.com/StaticFiles/Custom%20Install/Detailed%20Product%20Information/AV%20Receivers/SC-65_Back.jpg[/URL]

Off course, the ALPHA should have a [B]star ground[/B] [I](circuits -> case)[/I].[/QUOTE]

Please have a look at CLASS I & CLASS II electrical equipments.
Your example is a CLASS II, look at the symbol.

 

[Juntuin]

That's probably because the shunt feedback(c111,c115) is still not lifted and connected to PS ground.
For a proper signal lift the input signal and the shunt feedback need to be lifted, local PS decoupling and speaker return should not be lifted.
See the schematic of the BB.

Here it's lousy weather

Regards,
Danny

I'm master editor so just edited previous post also.

What possible negative effects I might suffer for lifting whole amp? It's quiet now atleast, and sounds very nice and powerful. It seems that proper grounding would need some serious work to be done.

Now it’s time to crank the volume and enjoy.
The ALPHA20 totally ROCKS!!!!!

You are so right my friend

 

[maty tinman]

https://www.google.com/search?q=av+receivers+earth+ground+double+insulation

-> Power and Grounding for Audio and Audio/Video Systems. A White Paper for the Real World.

[PDF] http://espsurgex.com/downloads/white-papers/PowerGround.pdf

 

[danny_66]

What possible negative effects I might suffer for lifting whole amp?

By lifting the whole amp PCB, you lifted also the speaker return where lots of current flows, those currents are now on the wrong side of the lift where the signal gnd also is.
You can remove the speaker return from the amp PCB and connect it to the star or PS smoothing caps ground.

 

[Juntuin]

By lifting the whole amp PCB, you lifted also the speaker return where lots of current flows, those currents are now on the wrong side of the lift where the signal gnd also is.
You can remove the speaker return from the amp PCB and connect it to the star or PS smoothing caps ground.

Thanks, I will do that rather sooner than later! Have to clean wirings anyway.

 

[danny_66]

Take beside the speaker return also the decoupling cap C103 gnd outside the signal gnd lift,
then you really have a signal lift

I did a simulation with speaker return inside signal ground lift and it looks very bad: distortion up with 50db and clipping starts already at 10v peak

 

[Vunce]

Would c103 gnd connect at the same location with speaker return on psu board?

 

[danny_66]

At the star or the smoothing caps, as long it is outside the signal ground lift.

 

[Vunce]

Gotcha.
Thanks Danny

 

[maty tinman]

To finnish

Marantz PM8006 inside

[URL]https://audio.com.pl/i/images/9/1/6/dz0xMjAwJmg9MTA1OQ==_src_49916-wzmacniacz-marantz-pm8006-audiocompl-fot7.jpg[/URL]

[B]Rotel A14[/B] inside

[IMG] [url]https://audio.com.pl/i/images/9/9/7/dz0xMjAwJmg9OTA4_src_49997-wzmacniacz_rotel-a14_audiocompl_fot9.jpg[/url][URL="https://audio.com.pl/testy/stereo/wzmacniacze-stereo/2914-rotel-a14"][/URL]

Does anyone know how [B]double insulation[/B] has been implemented?

 

[Juntuin]

Take beside the speaker return also the decoupling cap C103 gnd outside the signal gnd lift,
then you really have a signal lift

I did a simulation with speaker return inside signal ground lift and it looks very bad: distortion up with 50db and clipping starts already at 10v peak

Thanks for a simulation. I think I'll leave C103 as it is for now and move only speaker return to other side of the 10r lift asap. Have to rework with frame later anyway, then I'll change that cap also

 

[xrk971]

At the star or the smoothing caps, as long it is outside the signal ground lift.

Yes, C103 must be outside of the 10R ground (same as speaker return and PSU 0v) or it will inject hum into signal.

 

[Juntuin]

****..then this will take a while to accomplish. Just thought today that finally can move Alpha to drive horns rather than bass.

 

[zman01]

Progress on build

Got the ALPHA 20 boards populated - these are now waiting to go into the chassis. Excited!

 

[xrk971]

Nice work Zman! TH soldering wasn’t so bad then - how do you like it compared to all SMT?