Beautiful build there, Jwjarch!
How are you holding the toroid mounting bolts? I hope it’s not a metal bracket.
Because if it is, you might have a “shorted turn” on your trafo and that’s causing the buzz. Basically if the brackets are metal and the floor is metal and the bolt is metal, you have completed a wire loop that is a short through your transformer core. So it’s basically driving a very small length (1 turn) of a shorted loop.
But if one of the mounting brackets is non conducting or you have insulating bushings on the bolt so it doesn’t touch the bracket, or if the bracket is only on one side, then you are fine.
I have very dirty mains in my area too. My AC resembles a series bread loafs in shape vs smooth sine waves. I got a Furman AVR power conditioner consisting of a large multi tap toroidal transformer and that seems to have helped.
How are you holding the toroid mounting bolts? I hope it’s not a metal bracket.
Because if it is, you might have a “shorted turn” on your trafo and that’s causing the buzz. Basically if the brackets are metal and the floor is metal and the bolt is metal, you have completed a wire loop that is a short through your transformer core. So it’s basically driving a very small length (1 turn) of a shorted loop.
But if one of the mounting brackets is non conducting or you have insulating bushings on the bolt so it doesn’t touch the bracket, or if the bracket is only on one side, then you are fine.
I have very dirty mains in my area too. My AC resembles a series bread loafs in shape vs smooth sine waves. I got a Furman AVR power conditioner consisting of a large multi tap toroidal transformer and that seems to have helped.
Thanks X! Feels good to have a chassis with a solid PSU that I can swap various class A amps into.
The toroids are mounted on L-brackets, so no risk of a shorted turn there. I should have mentioned I also have solar panels on our house which are probably adding even more garbage to the my mains. I’ll let you know how the DIY power conditioner build pans out.
The toroids are mounted on L-brackets, so no risk of a shorted turn there. I should have mentioned I also have solar panels on our house which are probably adding even more garbage to the my mains. I’ll let you know how the DIY power conditioner build pans out.
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Hi X. Trying to get an idea of how many watts the SLB’s are dissipating in my build. My Kil-A-Watt says the amp is running at 235 Watts. Based on my calcs for ZM’s J2 boards I’m at 1.65A Iq and 44.4watts per device, times 4 is 177.6 watts. So that leaves 57.4 Watts to the SLB’s, or 14.35 watts per rail. Does that seem about right? Maybe there’s a little loss on my soft start board as well.
Hi Jwjarch,
1.65A x 2 is 3.3A per channel x 4v drop max is circa 13.2w for both rails so that’s about half of your value. What is your voltage drop across the SLb transistor ? The soft start has almost zero loss as RDson is circa 20mOhm.
Measure the drop across the two 0.1ohm resistors on the SLB. That will tell you what the true current is within 5% tolerance of the resistors.
1.65A x 2 is 3.3A per channel x 4v drop max is circa 13.2w for both rails so that’s about half of your value. What is your voltage drop across the SLb transistor ? The soft start has almost zero loss as RDson is circa 20mOhm.
Measure the drop across the two 0.1ohm resistors on the SLB. That will tell you what the true current is within 5% tolerance of the resistors.
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Yes, an Antek 4222 would make about 31vdc no-load. About 3v drop from SLB and another 3v to 4v sag from Class A operation gives 31v - 3v - 3v(to 4v) = circa 25(to 24)v. So about perfect per the design voltage for the F5. Yes, just buy from my store. Postage to NZ or OZ is about the highest it gets - circa $24 I think.
There are a few factors that determine your final voltage. First, what is your mains voltage? I have around 124vac on my mains. That's pretty high. So my dual mono SLB's with Antek 4222's end up at 26.9v with max drop-out dialed on the pots. Another consideration is a single transformer vs. dual mono. In your case, awc, a single transformer would drop down a bit more still with Class A current draw. In general, Antek's tend to drop a little more voltage than the same VA rating in say a Toroidy transformer.
All things considered, like X said, you're good with the 4222 but you may end up a with a little more than 24v. Not necessarily a bad thing unless you're cutting it close on heat sink area. What are you planning to use for a chassis?
All things considered, like X said, you're good with the 4222 but you may end up a with a little more than 24v. Not necessarily a bad thing unless you're cutting it close on heat sink area. What are you planning to use for a chassis?
I am gathering the parts for my SLB build. The 1uf Wima caps listed on the BOM are not in stock anywhere in the US that I can find.
Is this Wima PET cap an appropriate substitute?
https://www.mouser.com/ProductDetail/WIMA/MKS2C041001F00JSSD?qs=ISKKXg98%2B1lQgUuGZjf9mQ==
Is this Wima PET cap an appropriate substitute?
https://www.mouser.com/ProductDetail/WIMA/MKS2C041001F00JSSD?qs=ISKKXg98%2B1lQgUuGZjf9mQ==
You can substitute parts as long they closely mimic the specs of the BOM components, especially the CDE 15000uF capacitor ripple current. The physical size should be matched for fitment on the pcb, go taller not wider if you must. It’s a difficult time to fulfill complete parts list with so many out of stock components, it’s a challenge 
Yes, it's a pain but I've managed to get the parts to build two single-rail SLBs with just two orders so I guess I should consider myself lucky.
Anyway, just trying to short-circuit a lot of reading (the thread has become rather long) so some hopefully quick questions if I may:
One disappontment on the parts though, I was convinced I had a suitable toroidal transformer with two 0-30V secondary windings - dug it out of the cupboard only to find it has a 30V-0V-30V secondary!
Anyway, just trying to short-circuit a lot of reading (the thread has become rather long) so some hopefully quick questions if I may:
- I need an output from the SLB of about 39V; I believe the SLB will drop about 4V so a 30VAC transformer should be about right ((30 x 1.414) - 4V = 38.4V)
- Can anyone remond me what the preset on the SLB adjusts?
One disappontment on the parts though, I was convinced I had a suitable toroidal transformer with two 0-30V secondary windings - dug it out of the cupboard only to find it has a 30V-0V-30V secondary!
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Hi NB,
Pretty good estimate I’d say. The SLB will drop 3-4v more than a traditional CRC filter. The trimpot adjusts the voltage drop across the capmx pass transistor. Not much adjustment here, less than 1v. More drop = more ripple reduction = more heat from the pass transistor, but again it’s a very small adjustment. The trimpot on the SLB is not to adjust voltage like a regulated PSU, the SLB is not regulated.
What amp are you planning to pair the SLB with??
Cheers!
Pretty good estimate I’d say. The SLB will drop 3-4v more than a traditional CRC filter. The trimpot adjusts the voltage drop across the capmx pass transistor. Not much adjustment here, less than 1v. More drop = more ripple reduction = more heat from the pass transistor, but again it’s a very small adjustment. The trimpot on the SLB is not to adjust voltage like a regulated PSU, the SLB is not regulated.
What amp are you planning to pair the SLB with??
Cheers!
Thanks Vunce. I plan to use the SLBs in a variation on Ben Mah's '25W Single Ended Hammond 193V Choke Loaded 2SK180 L'Amp'.
It'll be used to drive the full-range speaker in a Pass SLOB and I'll be bandwidth limiting it to roll-off the bottom end without the need for a crossover - all being well of course. Ben Mah very kindly simuated it for me
https://www.diyaudio.com/forums/pas...-choke-loaded-2sk180-lamp-33.html#post6673284
It'll be used to drive the full-range speaker in a Pass SLOB and I'll be bandwidth limiting it to roll-off the bottom end without the need for a crossover - all being well of course. Ben Mah very kindly simuated it for me
https://www.diyaudio.com/forums/pas...-choke-loaded-2sk180-lamp-33.html#post6673284