Surprise, surprise - the power transformer does work for this board! The secondaries measure 18-0-18, despite being marked as 2 x 14v. Probably not enough current draw to pull it down. 18v is a little high, but luckily the regulators are not working hard at all.
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Seeing how the board has 2 stages of voltage regulation, I bet you could get away with 10-0-10 to 25-0-25 with zero reduction in performance. Looking at the datasheet, this is well within the limits of performance for the first stage.
The dual voltage regulation eliminates the need for “better” power supply capacitors or any kind of snubbing on the retifying dioes. Smart implimentation for a low current design and cost effective.
I wish the PS board on the Acurus was a bipolar design, but it’s single-ended with +12v & +5v regulators. I just pulled the diodes and took the secondaries to the Beeny board. I’ll need another regulated supply for the Arduino, but maybe I can tap off one of those 18v lines and knock it down with RC stages. Do I need to worry about that supply line being low impedance if it’s only powering the logic & motor circuits?
These are pretty easy and have a clean output. You could also use any 5v phone charger just tap at the AC inlet rather than post transformer.
I like that idea. If I didn’t already have transformers on the way, those would make things simple.
I contacted Mr Beeny a few days ago and shared the measurements in this thread with him. He emailed back today to ask if he could use some of the information and also mention this forum in an upcoming video. Of course I said YES!
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In stock now, but selling fast. I managed to get an order in.
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You guys are a bad influence ..
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Are you using sockets to make swapping op amps easier?
Haven’t started, waiting for Tom to finish his build. I am just sitting on the board.
i’ll go with whatever is easiest - don’t have much expreience with buidling amps/preamps. Though I like the idea of being able to switch op-amps. But as per Michael, there isn’t much benfit of rolling opamps.
I am interested in your build too and any mods, updates you do.
I hope to finish it up this month, but I’m slow to finish projects these days. I’m taking my time, trying not to rush things and doing a half-assed job.
I do have some of the LME op-amps coming, but Digikey is really slow these days. I’m anxious to see if the square waves are…more square. I think it sounds just fine with the 5532s. From what I’ve seen on the QuantAsylum, going with an external regulated supply isn’t improving THD or noise. I finally got the 15-0-15v transformers, but didn’t realize they were PC board mounts. I have some ideas about how to get around that with limited height in the Acurus chassis, but it may not be pretty.
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Have you seen where they are piggy backing the op amps?
no, link? this is for the preamp or some other thing?
No link. Been a long time ago and I’m clueless where, or how deep, it was buried in a thread/article/whatever it was.
In the case of this preamp, I don’t think there’s any reason to stack the op amps. The design has more than enough gain already and the transistors in the outputs don’t seem to have any issues supplying enough current to drive reasonable loads. It’ll even drive my 600 ohm headphones.
As far as other designs, post #4 by magic explains it better than I can, but I did not watch the 1 hour video.
Can’t find the bc557ctf at mouser or digikey. This is only to populate the board, no fuses, tranny, etc. I’ll add those later. Look ok?
https://www.mouser.com/Tools/SavedCart/Share?AccessID=053820e813
I see the bc557btf at Mouser - that’s what I ordered.
Whoops - it pulled up the 547 when I searched. Let’s try this instead -
https://www.mouser.com/ProductDetail/onsemi/BC557BTF?qs=kvVQGybKvwC8U%252BOirdZT8A%3D%3D
Not finding the difference between the bc557ctf vs bc557btf. Is this one of the things where the letter is just a packaging designation?
20k or 50k pot?
I just exchanged a few emails with Michael. He’s had some health issues lately and I really just wanted to make sure he was still upright and moving about. He told me the follow-up video about the preamp design will be out as soon as they get the OK to sell worldwide.
He also said they are now working on a power amp design. He didn’t give many details and it sounds like it’s in the early stages. He was adamant they would not hide any flaws discovered along the way and price would not be a consideration to achieve their targeted goals. I am, of course, quite curious to see what they come up with. I’m hoping it’s a scalable design, with enough drive capability to feed multiple output devices.
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