Glad to hear that more SLBs made it to you, Meanie.
Just used a single SLB in my new Alpha Nirvana amp. Running a 600VA Antek 6224 trafo to make +/-28v rails at 1.7A. Works great - no noise or hum. Amp is silent.
Note that Hugh’s amp designs seem to like to have their RCA ground run to the amp board rather than the SLB star ground (which the M2X seems to like better).
I will have to tidy up the amp with some new double conductor silicone 16ga wires and cable management braided nylon covers.
So here is a passively cooled 4Ux300mm chassis 45w Class A amp using a single SLB.
Just used a single SLB in my new Alpha Nirvana amp. Running a 600VA Antek 6224 trafo to make +/-28v rails at 1.7A. Works great - no noise or hum. Amp is silent.
Note that Hugh’s amp designs seem to like to have their RCA ground run to the amp board rather than the SLB star ground (which the M2X seems to like better).
I will have to tidy up the amp with some new double conductor silicone 16ga wires and cable management braided nylon covers.
So here is a passively cooled 4Ux300mm chassis 45w Class A amp using a single SLB.
meanie,
If we take the rule of thumb that the VA rating of a transformer for a Class A amplifier should be at least 6 times the output watts, 500VA should be just enough.
If we take the rule of thumb that the VA rating of a transformer for a Class A amplifier should be at least 6 times the output watts, 500VA should be just enough.
Here are a couple SLB supplies getting ready to power up an F6. I had two Antek AS-3222 transformers on hand, and have been getting a solid +/– 26.1V into a 1.7 Amp (15 Ohm) dummy load. The actual amp will probably draw less current to manage heat, but I'm still shooting for about 1.55 Amps to tickle a set of FQH44N10 Mosfets.
Attachments
If I can get 28.5v with a 600VA, you might be able to manage 26.5v to 27v with a 500VA. So yes, I think it can work!
@TungstenAudio:
Those are impressively large flag heatsinks for a TO247 package. I have never seen something like that. Where do you get those "Dumbo Ears" heatsinks?
Those are impressively large flag heatsinks for a TO247 package. I have never seen something like that. Where do you get those "Dumbo Ears" heatsinks?
I found those heatsinks at a local surplus electronics store. I haven't seen anything else similar to them. My other option for cooling the output transistors was to bolt them onto the base plate. I chose to use that area for ventilation holes instead, as I'm trying to draw some heat from the sides down into the base.
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?
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. 🙂
@Aljordan,
If you’re going to build the Alpha20 with a single transformer, you will need at least 400VA.
If you’re going to build the Alpha20 with a single transformer, you will need at least 400VA.
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.
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.
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
Earthing system - Wikipedia
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:
PE chassis/earth/IEC/heatsink tie point:
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:
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.
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:
PE chassis/earth/IEC/heatsink tie point:
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:
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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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 😀
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 😀