I was thinking exactly about the same idea Vunce - yes more options and cheaper caps as well. Only issue I see, is if for some strange reason the upper 2SC5200 transistor fails, then the output cap C13 will see the full positive rail voltage as well.
Look forward to your thought on that Borko.
Look forward to your thought on that Borko.
Well for AC conditions 35V is enough but for your scenario - 50V.
It's dangerous for a cap that large to pop.. 😁 Never the less, as I can see, a failure of the BJT could be more from thermal reasons, than electrical, this kind of topology with ccs in the output stage is current limited.
Officially 50V, is recommended, better safe than sorry. I use 35V at my own responsibility
It's dangerous for a cap that large to pop.. 😁 Never the less, as I can see, a failure of the BJT could be more from thermal reasons, than electrical, this kind of topology with ccs in the output stage is current limited.
Officially 50V, is recommended, better safe than sorry. I use 35V at my own responsibility
4700uf 40v roe gold + elna cerafine 1000uf 35v + ero 10uf mkt for caps bank
internally 3u3 wima mks4 + elna 4700uf 50v
How does that sound?
I also cannot supply smd jfet. I assembled under 2sk170 pcb.
Would nichicon kg 8200uf + 0.1r 11w + 8200uf kg and 100nf be better for 35vdc crc feeding?
There is no 200k trimpot left for vr6 in my stock. Can I use 100k or 500k instead.
internally 3u3 wima mks4 + elna 4700uf 50v
How does that sound?
I also cannot supply smd jfet. I assembled under 2sk170 pcb.
Would nichicon kg 8200uf + 0.1r 11w + 8200uf kg and 100nf be better for 35vdc crc feeding?
There is no 200k trimpot left for vr6 in my stock. Can I use 100k or 500k instead.
Of course, one could also use bjt in larger package, something like 2SC2922..
The circuit is flexible, I guess there will be no problems with all kind of different parts, I made it with what I had at home..
Yes, 2SK170 could be used, just check pin orientation.
And yes that kind of CRC could be used for the power supply, but that should be for one channel only.
Btw, I don't understand what you wrote about cap bank, and "internal" caps, you use one or other, not both.
You need 220K trimpot, with 100K, one resistor should be changed..
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Second channel fired up smooth as silk just like the first. This board has the Irfp9240 replaced with an FQA36P15, a polycarbonate film cap replacing the the Wima MKS output bypass cap and a heatsink on T1. Otherwise, identical to the first channel. I bumped the bias on both up to 1.5A, I like the sound better at this level.
There’s a faint hum with my ear up against the speaker that was not present when a single amp board was powered. Currently the transformer secondaries are paralleled to get full power. I plan to go dual mono, so each channel will be powered by it’s own secondary and SLB psu, that should squash the faint background hum.
In the upcoming days I will transfer the SECFA ‘plank amp’ to my main system and let her cook!
Thanks for sharing this project, Borko! Its very well mannered also without any turn on/off thumps or pops.
There’s a faint hum with my ear up against the speaker that was not present when a single amp board was powered. Currently the transformer secondaries are paralleled to get full power. I plan to go dual mono, so each channel will be powered by it’s own secondary and SLB psu, that should squash the faint background hum.
In the upcoming days I will transfer the SECFA ‘plank amp’ to my main system and let her cook!
Thanks for sharing this project, Borko! Its very well mannered also without any turn on/off thumps or pops.
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Extremely unlikely, unless power transformer is very close to the boards. Ground loop perhaps. None of my power amps are inside shielded boxes.
Hi Thimios,
When I separated the secondaries and fed each an SLB psu the hum was still there, not possible!! I investigated further and found the problem, one of the RCA adapters had a faulty ground connection. Problem solved, this amplifier is dead quiet at idle now. Impossible to tell it’s on
Now I wonder if the single SLB would have been fine, probably. But, I like to use dual PSU’s with my builds anyway.
I moved the SECFA to the main system for long term break-in, it’s driving my 10F/8424 & RS225-8 FAST TL floorstanders, 8ohm and efficiency is in the low 80’s dB. The combo sounds very good!
Sweet job Borko, I believe you have a keeper in the SECFA
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Your correct, I can’t listen to music at rock concert sound levels. But, 25W with these speakers is plenty to fill the room. I do have a few amplifiers Class A, tube, and class D in this power range and know what to expect. For an example, when the bass line kicks in on ‘Hey Now’ the pictures on the wall move and the front window vibrates, I think that’s loud enough
(Also, it’s not flabby and uncontrolled bass)
hey now song - Google Search
(Also, it’s not flabby and uncontrolled bass)
hey now song - Google Search