I agree that the On/Off lettering on the silkscreen is backwards relative to function. It is as if it is labeling the switch as an "on-off" switch rather than giving guidance as to the power state. I am sure this is the reason that Pass recently stated in post #968: "To avoid confusion, the switch is "off" when the toggle is to the left (as seen front the front)."
The good news is that In use, as long as power is supplied to the board, the adjacent LED will indicate whether it is on or off. That is easy enough to remember...
I must have missed (or forgotten) that post!
I should also add that this was an awesome little project! SUPER fun and I used it to procrastinate doing a work project. It's making music right now and sounds fantastic (as everyone has said). It replaced a p-channel V-FET lottery amp and I'm not immediately missing anything!
Thanks Nelson and everyone at DIY audio for making this kit available (and for such a steal)!!
Northpaw...you can listen once it's switched on. You won't stress anything.
I should also add that this was an awesome little project! SUPER fun and I used it to procrastinate doing a work project. It's making music right now and sounds fantastic (as everyone has said). It replaced a p-channel V-FET lottery amp and I'm not immediately missing anything!
Thanks Nelson and everyone at DIY audio for making this kit available (and for such a steal)!!
Northpaw...you can listen once it's switched on. You won't stress anything.
Here it is nude making some music. Matches my bread-boarded preamp. I'll probably knock up a case some day, but for now this is a great little setup. Matches my clutter 🙂
Thanks for the advice about warm up. So just like other solid state amps.
I only have a couple of hours listening to this thing. And that is through a pair of Advent OLAs, not exactly efficient. But this little amp doesn't care, it is playing beautifully. What strikes me is not what is there, but what is not. There is just music. The music seems so pure that it feels enshrouded in a quiet majesty and dignity. It lifts my heart. Thank you, Mr. Pass.
I only have a couple of hours listening to this thing. And that is through a pair of Advent OLAs, not exactly efficient. But this little amp doesn't care, it is playing beautifully. What strikes me is not what is there, but what is not. There is just music. The music seems so pure that it feels enshrouded in a quiet majesty and dignity. It lifts my heart. Thank you, Mr. Pass.
I don't know if Digikey stocks these, or this vendor's international shipping rates/policies, but this item was posted earlier in the thread and are what I'm going to try: https://www.parts-express.com/Lil-Piggies-Binding-Posts-to-Lead-Wire-Adapter-Set-Red-and-B-091-1262
Taking some inspiration from Mark and his words of encouragement, I went ahead and instigated a board layout of my own .
I like how Mark Johnson tries to give us confidence to go the extra mile in this hobby; by getting boards made using gerbers, or indeed getting one of the very talented layout designers available to us on the forum to set out a PCB.
So I approached @prasi if he would be interested in a little project for me and he kindly obliged and at a very reasonable cost.
Here is what we(he!) came up with . I have sent the files to JLCPCB and am having a small run made, in black! Once I have them and have made one up and tested I shall offer the rest for sale, at a price only to cover my costs. I am not wanting to make money on this.
I have some Harris devices and the input Toshiba's are on their way from punkydawgs.
Thanks to NP and MJ and of course Prasi for getting me this far with my ACA Mini.
Attachments
Thanks James. They look like a good binding post option. Parts Express shipping to Oz is pretty expensive from memory but there is a local reseller that stocks some of their stuff. I’m looking for a jumper though which is a bit different. I think I’ve found a jumper. Digikey part S9337-ND looks like it’ll work as long as the ACA Mini board has 2.54mm (0.1”) jumper pin spacing..
Thanks! Been playing w/ some preamp designs. This one is a choke loaded C3g w/ LED bias. Super simple and sounds great. Dave Slagle autoformer volume control in front of it.
*edit to add photo
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Triode connected. 140V B+ and -2V bias (yellow LED). Around 10ma or so. Played with a bunch of operating points, and honestly more current didn't really lower the distortion too much. It's around .02% all 2nd. I've had these tubes for like 20+ years and finally got around to playing with them! Crazy how simple it is to slap something like this together. Was doing the same thing w/ 2sk79s as well (same setup). Was going to post a thread for that eventually. Very similar sound between them. Difference being that the 2sk79s had negative phase 2nd where these tubes have positive phase.
You should be able to adjust that with load-line or if not, run the signal inverted through them...
Thanks! I was going to ask. When using transformers (which I also was testing), it was as simple as flipping the phase on the output so that it was negative. I didn't know if I needed to change anything else. I didn't notice any load lines that resulted in negative phase, but with the tubes I didn't try many options. I'll have to experiment more. The 2sk79s were negative phase in all voltages and operating points I tried (probably 10-12 different permutations).
Grazie nicoch68. They look better than the jumpers I found.
Little hiccup. My bias will not stabilize. The difference between having the A/C on and not (but still cooler than not in the room) is .27v and .38v at the test point. I set it to .30v at what I thought was a good median temp (after hours of warmup). Will this thing run away, or will the heatsinks just get hot? They were at 60°C at .38v. Should I up R8 and R9 to 1 ohm?
I should note...that is w/ the amp being on all day. Just happened to check it and was shocked to see how high it had drifted.
I should note...that is w/ the amp being on all day. Just happened to check it and was shocked to see how high it had drifted.