So after some time with my 3 deep BA-3 running, I am starting to get all the parts needed to rebuild it in pimp-my-amp fashion. It will be 3 deep too, using store standard IRFPs (not Harris). 6 deep with self-matched Harris’es saved for future possible not so likely project.
I have been contemplating starting a dedicated thread, and ZM encouraged me to, so here we are.
A bit of info on the first version, now being revisited. It was my first build, and I ended up having to troubleshoot some stuff and disassembling a few boards and so on. Result was a few pads gone bad, so for longevity they have to be replaced anyways.
1: The case is a 5U 400 from a broken down F5T. It was mistreated, so a new back panel, bottom panel, UMS mounting plate and a new sink had to be ordered. This was good, since when replacing the sink I found that a crooked mounting hole had made one of the fets de facto break through the Kheraterm. A wonder I avoided a short...
Lesson: never buy a broken F5T! Build a new one, or something else.
2: FE: I used Fairchild MOSFETs and LS JFETs. Never happy with what I have, I wanted to use Nelson’s specced parts. Toshiba FE MOSFETs have arrived from Japans underground through Prakit. Matched 10.14-16mA Toshiba JFETs arrived from Punkydawgs. But by some magic misfortune, there was only one pair in the bags. Punky does not know what happened, neither do I. And now he is out of 10mA’s... I got a full refund without discussion, so thank’s to Punky for that. But my goal was 10mA matched Toshibas, so it is still a real bummer. The LS’es bias too low, and I wanna avoid adjusting source resistors, something that in any case might not prove to bias them to spec.
So if anyone have a spare 10mA pair of J74/K170s just lying around gathering dust, you are welcome to chime in (hoping hoping).
3: I use 32v rails at the moment. My transformer is a noisy Noratel 600va. I had some hum, but managed to almost completely remove it. But the rail voltage also limits my max bias. So I am going universal FW dual mono PSU inspired by ZM. 2x300va 18v secondaries Toroidy audio grades have arrived. Less power, but more versatile, and higher bias. Easy.
4: Attached is a pic of some of the PSU parts. I am going P2P. Absent from pics is snubber network and decouplers. It will be a tight fit, and this is with 4 caps not even included in the pic. Inductors are 10mH @ 5A Hammonds. I have some options here, building vertically, mounting trannies on the front plate, and so on. All insight and pointers are appreciated. Pic shows 94.000uf before inductors and 200.000uF after the inductors, per channel to run at approx 2A5 bias per channel. I have to scale up from approx 300kuF to 400kUf per channel, putting the extra capacitance after the inductors, provided enough space. Having more capacitance after the chokes is a deliberate choice, something about steep charging currents and all.
5: Layout-wise I think I need to put the bias boards on the back plate along with the FE. I also might mount the FE and bias boards horizontally, in PL fashion, but need a 3D printer or metal work expertise for that, we’ll see.
6: Soft start circuitry is not yet decided. I have 2x store soft starts, but might go thermistor. Insight appreciated, pushing the limits here both wrt the stores bords and CL-60s. Fuses will be on back plaate, one per channel. Disregard the terminal block for now. It is an alternative since I have long AC wires specced per tranny, but soldering would be nice and in both Papa’s and Choky’s spirit.
This will be done in slowish fashion, I do have a working amp.
Hope is to have a ripple free, close to Nelson-spec amp, with a hand built XL oversized PSU with full control over grounding scheme. We will see.
I hope this thread can be an arena for discussion, and learning, for me and perhaps also fellow builders.
I prolly forgot a bunch of things, but hence this thread.
Attached is a most of the PSU section and my JFET pair absent it’s wife and husband.
Thanks to everyone who got me this far, looking forward to the continuation.
Regards,
Andy
I have been contemplating starting a dedicated thread, and ZM encouraged me to, so here we are.
A bit of info on the first version, now being revisited. It was my first build, and I ended up having to troubleshoot some stuff and disassembling a few boards and so on. Result was a few pads gone bad, so for longevity they have to be replaced anyways.
1: The case is a 5U 400 from a broken down F5T. It was mistreated, so a new back panel, bottom panel, UMS mounting plate and a new sink had to be ordered. This was good, since when replacing the sink I found that a crooked mounting hole had made one of the fets de facto break through the Kheraterm. A wonder I avoided a short...
Lesson: never buy a broken F5T! Build a new one, or something else.
2: FE: I used Fairchild MOSFETs and LS JFETs. Never happy with what I have, I wanted to use Nelson’s specced parts. Toshiba FE MOSFETs have arrived from Japans underground through Prakit. Matched 10.14-16mA Toshiba JFETs arrived from Punkydawgs. But by some magic misfortune, there was only one pair in the bags. Punky does not know what happened, neither do I. And now he is out of 10mA’s... I got a full refund without discussion, so thank’s to Punky for that. But my goal was 10mA matched Toshibas, so it is still a real bummer. The LS’es bias too low, and I wanna avoid adjusting source resistors, something that in any case might not prove to bias them to spec.
So if anyone have a spare 10mA pair of J74/K170s just lying around gathering dust, you are welcome to chime in (hoping hoping).
3: I use 32v rails at the moment. My transformer is a noisy Noratel 600va. I had some hum, but managed to almost completely remove it. But the rail voltage also limits my max bias. So I am going universal FW dual mono PSU inspired by ZM. 2x300va 18v secondaries Toroidy audio grades have arrived. Less power, but more versatile, and higher bias. Easy.
4: Attached is a pic of some of the PSU parts. I am going P2P. Absent from pics is snubber network and decouplers. It will be a tight fit, and this is with 4 caps not even included in the pic. Inductors are 10mH @ 5A Hammonds. I have some options here, building vertically, mounting trannies on the front plate, and so on. All insight and pointers are appreciated. Pic shows 94.000uf before inductors and 200.000uF after the inductors, per channel to run at approx 2A5 bias per channel. I have to scale up from approx 300kuF to 400kUf per channel, putting the extra capacitance after the inductors, provided enough space. Having more capacitance after the chokes is a deliberate choice, something about steep charging currents and all.
5: Layout-wise I think I need to put the bias boards on the back plate along with the FE. I also might mount the FE and bias boards horizontally, in PL fashion, but need a 3D printer or metal work expertise for that, we’ll see.
6: Soft start circuitry is not yet decided. I have 2x store soft starts, but might go thermistor. Insight appreciated, pushing the limits here both wrt the stores bords and CL-60s. Fuses will be on back plaate, one per channel. Disregard the terminal block for now. It is an alternative since I have long AC wires specced per tranny, but soldering would be nice and in both Papa’s and Choky’s spirit.
This will be done in slowish fashion, I do have a working amp.
Hope is to have a ripple free, close to Nelson-spec amp, with a hand built XL oversized PSU with full control over grounding scheme. We will see.
I hope this thread can be an arena for discussion, and learning, for me and perhaps also fellow builders.
I prolly forgot a bunch of things, but hence this thread.
Attached is a most of the PSU section and my JFET pair absent it’s wife and husband.
Thanks to everyone who got me this far, looking forward to the continuation.
Regards,
Andy
Attachments
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Re: Softstart
Andy, have you taken Marks Softstart ( PCB: low voltage On-Off switch drives AC mains relay \ includes soft start .. H9KPXG ) into consideration? It’s as always an extremely clever design (as far as I can see, anyway, which as you know isn’t that far), giving you a soft start/soft unstart, and furthermore a kind of standby as well as access to all those nifty highend-low power switches…
I went for the stores ss, against the cl60 because the cl60 gets hot and still eats a tiny amount of current (or is it voltage)?
Andy, have you taken Marks Softstart ( PCB: low voltage On-Off switch drives AC mains relay \ includes soft start .. H9KPXG ) into consideration? It’s as always an extremely clever design (as far as I can see, anyway, which as you know isn’t that far), giving you a soft start/soft unstart, and furthermore a kind of standby as well as access to all those nifty highend-low power switches…
I went for the stores ss, against the cl60 because the cl60 gets hot and still eats a tiny amount of current (or is it voltage)?
Hi, Gary! Thanks for noticing. Forgot to mention the new transformers are 18v secondaries. 0R160 DCR of the Hammonds will take it down to under 25, and if more is nescessary I’ll use some R to reduce voltage a bit. But I modelled it and it should be OK.
Andy,
I would definitely consider a softstart board for this build and not just do the usual CL-60 thermistor setup. You are dealing with 0.8 FARADS of capacitance at the end of the day!
You have many choices. I am partial to Neurochrome's ISS (but I purchased several of his boards before, and they are excellently designed with superb documentation and BOM lists as well as pre-populated full links on Mouser). You also have your choices from XRK's "Soft as a Feather Pillow" that he sells on Etsy and also MJ's softstart as linked above. You could even use 1 softstart board per 300VA toroid/CLC combo.
You have already invested quite a bit on the PS filter capacitors/chokes, this is definitely one way to go. Have you considered capacitance multiplier supplies such as XRK's Smooth Like Butter? I would use one per channel and the SLB should handle 2.5A. It includes ground loop lifting circuitry and is more compact overall.
But like I said, you already have a lot invested in your build and there is nothing wrong with a CLC supply. 0.8F of capacitance in total? I'm sure your ripple will be low with the inductor thrown in there
. And capacitance multiplier supplies like the SLB require higher voltage secondaries from the transformer and I see you already have 18V secondaries on the Toroidy. Choices...choices!
Best,
Anand.
I would definitely consider a softstart board for this build and not just do the usual CL-60 thermistor setup. You are dealing with 0.8 FARADS of capacitance at the end of the day!
You have many choices. I am partial to Neurochrome's ISS (but I purchased several of his boards before, and they are excellently designed with superb documentation and BOM lists as well as pre-populated full links on Mouser). You also have your choices from XRK's "Soft as a Feather Pillow" that he sells on Etsy and also MJ's softstart as linked above. You could even use 1 softstart board per 300VA toroid/CLC combo.
You have already invested quite a bit on the PS filter capacitors/chokes, this is definitely one way to go. Have you considered capacitance multiplier supplies such as XRK's Smooth Like Butter? I would use one per channel and the SLB should handle 2.5A. It includes ground loop lifting circuitry and is more compact overall.
But like I said, you already have a lot invested in your build and there is nothing wrong with a CLC supply. 0.8F of capacitance in total? I'm sure your ripple will be low with the inductor thrown in there
. And capacitance multiplier supplies like the SLB require higher voltage secondaries from the transformer and I see you already have 18V secondaries on the Toroidy. Choices...choices!Best,
Anand.
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me preparing Popcorns
You mean corn to roast on my burning amp? You bring popcorn to parties or funerals? You should to both, never know how my projects turn out. Thanks for all the help so far!
Son of Zardoz
Andy,
I would definitely consider a softstart board for this build and not just do the usual CL-60 thermistor setup. You are dealing with 0.8 FARADS of capacitance at the end of the day!
You have many choices. I am partial to Neurochrome's ISS (but I purchased several of his boards before, and they are excellently designed with superb documentation and BOM lists as well as pre-populated full links on Mouser). You also have your choices from XRK's "Soft as a Feather Pillow" that he sells on Etsy and also MJ's softstart as linked above. You could even use 1 softstart board per 300VA toroid/CLC combo.
You have already invested quite a bit on the PS filter capacitors/chokes, this is definitely one way to go. Have you considered capacitance multiplier supplies such as XRK's Smooth Like Butter? I would use one per channel and the SLB should handle 2.5A. It includes ground loop lifting circuitry and is more compact overall.
But like I said, you already have a lot invested in your build and there is nothing wrong with a CLC supply. 0.8F of capacitance in total? I'm sure your ripple will be low with the inductor thrown in there
Best,
Anand.
Thank you for that, Anand!
I will check out the links and info as soon as I have time. Btw, my two store softstart boards might so the trick - for starters that is. If I use «only» 300 of my 400k per side, I figure one such board per channel might do the trick. But can’t be entirely sure. Russelc uses 276k on one of them, and he’s not complaining. Still, might not be the best of choices, but good enough?
Will stick with this PSU for now btw, expensive stuff :S
Thanks, David!
I have seen that circuit. Smart, all in one, smart as everything from Mark. U know if PCBs are available still? Will check out.
Regards,
Andy
If you mean the store slo start board, yes I used it on my BA3 build. It wasn't my idea, I just followed 6l6's build guide to the letter. He used them, so did I. I used the same rail voltages as well. I just straight up copied the build guide.
The amp has performed flawlessly since first fired up and has worked great for several years. I absolutely have had no issues surrounding the softstart.
As he said, its a pretty stiff power supply with 1000VA xfmr.
Russellc
As far as I know, they’re not that easy to get. Easier to have them made [emoji6] (jlcpcb / pcbway etc., Mark provided us everything we need, even the link to a pcb-maker price-comparison…)
But the more daring aspect is that then you‘ll be subject to some of his, uhm, special treatment [emoji16]… (sorry Mark, couldn‘t resist…)
If you mean the store slo start board, yes I used it on my BA3 build. It wasn't my idea, I just followed 6l6's build guide to the letter. He used them, so did I. I used the same rail voltages as well. I just straight up copied the build guide.
The amp has performed flawlessly since first fired up and has worked great for several years. I absolutely have had no issues surrounding the softstart.
As he said, its a pretty stiff power supply with 1000VA xfmr.
Russellc
Thanks for chiming in!
Yup, and if one of the stores softstarts can handle your 1000va doughnut and 264kuF, I figure my 300va and 300-400kuF will work too.
What do you think, will I be able to get this PSU up and running? =)
To you and David: Will check out Marks circuit. I do agree standby and the other functions are tempting. On the other hand, simpler is better most of the time :S Maybe get it running first?
Andy
Will check it out. All that functionality and cheap too, tempting...
But, Dennes, wrt softstart, limited to that specific funtionality, I know you are a fan of them. Like Nelson. One of my eternal tasks is self-enlightenment. Why choose them, in your opinion, and is there a thermistor you would find suitable for my project? Each channel will boast 300va, 94kuF-10mH-200kuF-(10uF decoupler - irrelevant). 230v mains.
And how is that VFET coming along?
Regards,
Andy
But, Dennes, wrt softstart, limited to that specific funtionality, I know you are a fan of them. Like Nelson. One of my eternal tasks is self-enlightenment. Why choose them, in your opinion, and is there a thermistor you would find suitable for my project? Each channel will boast 300va, 94kuF-10mH-200kuF-(10uF decoupler - irrelevant). 230v mains.
And how is that VFET coming along?
Regards,
Andy
Don‘t overestimate the word „stand-by“… it’s just that ss-board standing by, waiting for your finger to push the button…
Having it running first certainly is a good path to follow, except that you‘ll be dis-/ assembling that beast a few more times. (Well and I actually wrecked my WLS this way)
Re: SS being able to handle the inrush current—as I have understood, there’s the relays which switch from softstart to full throttle, and more importantly, the resistors or in Mark’s jig the thermistors that handle the current-spike, these must be able to sustain the peak.
Then, on the store’s board, there’s some capacitor which regulate the timing, how Mark’s handles it I don‘t remember.
I am pretty sure all of the mentioned jigs are easily able to handle the inrush current of your PSU…
Or you could get even more simple and just use CL-60 set up now, use Mark's boards after its up and running. Stand by and so forth would be nice additions.
The power supply will be easy to get going. As long as Trans,Caps,rectifiers etc are not defective and no cold solder joints or miss-wires what's to go wrong?
Russellc
He also has another board, (maybe it is incorporated into this one?) that had a relay for the power switch...it allowed you to use all sorts of cool on off switches that otherwise wouldn't have sufficient amperage rating. This circuit did the switching, the "on-off" switch just set it off as I understand? Nice.
Russellc
I read about that board, Russel. Seems really nice. I am kinda thinking keeping it as simple *** possible just for now, and perhaps employing the fancy stuff later. I saw one of Marka circuits, prolly the one you are referring to, also had 12v remote switch on functionality. Really nice.
Did you once make an external PSU?
That would save all the space worries, and perhaps reduce risk of inductors magnetically coupling with tranny and circuitry and so on... then I could put the 100kuFs in the amp case. Have been contemplating it, but dunno if it is worth the extra cost and work at this point.
Would need some umbilicals and dc entries and outputs, and also a careful gnd routing scheme.
Pointers appreciated.
Cheers,
Andy
Did you once make an external PSU?
That would save all the space worries, and perhaps reduce risk of inductors magnetically coupling with tranny and circuitry and so on... then I could put the 100kuFs in the amp case. Have been contemplating it, but dunno if it is worth the extra cost and work at this point.
Would need some umbilicals and dc entries and outputs, and also a careful gnd routing scheme.
Pointers appreciated.
Cheers,
Andy