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The SLB (Smooth Like Butter) Active Rect/CRC/Cap Mx Class A Power Supply GB
The SLB (Smooth Like Butter) Active Rect/CRC/Cap Mx Class A Power Supply GB
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Old 30th November 2019, 12:59 AM   #631
aljordan is offline aljordan  United States
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I built two SLB DRs. I could use them as a dual mono supply with AS2222 transformers in an upcoming Alpha 20, or I could use one each in the Alpha 20 and an existing Aleph J with AS3222 transformers. What would you do?
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Old 30th November 2019, 01:14 AM   #632
xrk971 is online now xrk971  United States
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The SLB (Smooth Like Butter) Active Rect/CRC/Cap Mx Class A Power Supply GB
A single SLB works fine in Alpha 20 as Vunce has demonstrated. You could build both Alpha and Aleph J, if that’s what you want to do. However, having built the Aleph J already, I can tell you that the Alpha 20 sounds better to my ears. Save the other SLB for an Alpha Nirvana.
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Old 30th November 2019, 01:19 AM   #633
Vunce is offline Vunce  United States
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The SLB (Smooth Like Butter) Active Rect/CRC/Cap Mx Class A Power Supply GB
@Aljordan,

If you’re going to build the Alpha20 with a single transformer, you will need at least 400VA.
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Old 30th November 2019, 01:26 AM   #634
aljordan is offline aljordan  United States
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Quote:
Originally Posted by Vunce View Post
@Aljordan,

If you’re going to build the Alpha20 with a single transformer, you will need at least 400VA.
Thanks for the heads-up.
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Old 6th December 2019, 02:39 PM   #635
aljordan is offline aljordan  United States
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Hello and please forgive my ignorance.

In a number of build pictures with the SLB and various Alpha amps, I see people are running ground lines to the chassis heat syncs. What is the purpose of doing this?

In particular, Vunce's wiring of the Alpha Nirvana here, it looks like he has a double twisted ground wire from the SLB board to the chassis bottom, a double twisted wire from the IEC plug to the chassis floor (hard to tell in the picture), then a ground line from each audio board to the heat syncs. I can't tell where those heat sync ground lines go from there, but it looks like they may be also connecting to the chassis ground on the floor of the amp. Why are the audio board grounds not connecting back to the power supply star ground lugs?

What is the second double twisted ground line going to the chassis rail for?

When I built my M2 and Aleph J with standard CRC power supplies. I had a ground from the IEC plug to the chassis, a ground from the power supply to the chassis lifted by a CL60, and the audio board grounds ran back to the power supply ground plane. I am confused by these additional grounds tied to different points of the chassis.

Thanks for anything you can do to aid my understanding.
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Old 6th December 2019, 03:11 PM   #636
Shawnstium is offline Shawnstium  United States
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Those green wires are PE, protective earth, "ground" for the chassis and are different from the RETURN (aka ground in the US) of the DC power and audio signals. I think it's awesome to see DIYer using that type of PE wiring. It is common practice for high wattage power supplies to have PE connection to each panel.

Earthing system - Wikipedia
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Old 6th December 2019, 03:18 PM   #637
xrk971 is online now xrk971  United States
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The SLB (Smooth Like Butter) Active Rect/CRC/Cap Mx Class A Power Supply GB
Hi Aljordan,

The main idea is to have all things like chassis and heat sinks (parts of chassis) to go to IEC earth/mains ground. This is not only for safety in case something goes and conducts live to ground, it is all safely shunted to earth/mains ground. But also for reducing RFI pickup, tying chassis and heatsinks to ground makes for a quieter amp. The heatsinks if not grounded can act as a capacitor with the MOSFETs and add noise or oscillation. So we to them to a convenient earth ground point on the chassis. A double twisted wire to reduce impedance.

Here is photo of my Alpha Nirvana and SLB:
Click the image to open in full size.

PE chassis/earth/IEC/heatsink tie point:
Click the image to open in full size.
More info here:
Alpha Nirvana 39w 8ohm Class A Amp

Regarding 0v analog and power ground, this is lifted from the “PE” protective earth or (dirty) earth/chassis ground by an NTC (CL60 or 8D-20) and bypassed with a 22nF film cap. This is provided on the SLB between the clean 0v analog and power ground and the “PE” power and protective earth ground connection which goes to the earth/mains/chassis ground point.

You want to control where all your ground points touch or connect. Using a star topology helps prevent hum/buzz.

Here is the connection diagram for mine:
Click the image to open in full size.

On some amps (like M2X) I found that having the RCA jack ground go to the SLB star hub was quieter. Similarly, having speaker return go to the SLB star hub was quoted on M2X as well. But on Alpha Nirvana, which has a 10ohm ground lift for the input audio, and a few other ground nodes, it seems RCA ground should go to the amp itself.
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Last edited by xrk971; 6th December 2019 at 03:24 PM.
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Old 6th December 2019, 03:28 PM   #638
aljordan is offline aljordan  United States
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Thanks X and Shawnstium!
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Old 6th December 2019, 03:59 PM   #639
Vunce is offline Vunce  United States
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The SLB (Smooth Like Butter) Active Rect/CRC/Cap Mx Class A Power Supply GB
Hi Aljordan,
The heatsinks in my Proto build are resting on wood and therefore have no continuity to ground, that is the reason I ran a wire from the ground lug to each heatsink. When using a proper metal chassis, all panels and heat sinks will be grounded so there would be no need for the individual direct wires.
Hope that helps clear up where some wires go in my spaghetti mess
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Old 6th December 2019, 04:50 PM   #640
jhofland is offline jhofland  United States
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Vunce,
How could a person of Italian descent call spaghetti a mess (smiley)?
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