Thanks asuslover, I actually stumbled on that just a minute before checking back here. It looks like the author prefers a zobel tuned lower (approx. 150 kHz) than the recommended (approx 590 kHz). The tuning on this particular implementation (approx 600 kHz) seems to be close to the datasheet recommendations, increasing to 100 nf roughly halves frequency (338 kHz), but still leaves me at twice the frequency they use in your link. I take that as safe, thanks again!
Just finished another example of this amp today. We've been in the market for a new amp/preamp (conveniently for me you say) because we just took over a small allotment summer house this year. Naturally, a summer house must have music, so i've been planning and plotting, and finally managed to put the lid on the last part of that puzzle. This open source LM3886 was perfect for the small house (30 sq m), and will drive Alpair 10.3s in small bookshelves (Scottmooses design). At the moment i am listening to it at home on pensils with 10ps. Very nice sounding amp i must say. I usually rely on a DIY F6, but I will have no trouble living with this for the next while as it burns in (or my ears do).
IT is driven by a Kuartlotron preamp, and i can warmly recommend the combination. There is plenty of gain in the LM3886 to make me not miss gain in the preamp. In fact, i haven't gotten past halfways on the volume control. With the F6, i quickly start missing the gain on my BA-3 preamp, but for the gain of the OS LM3886 it is spot on.
I put the amp in a mini dissipante from modushop, tight but very nice chassis, and the heatsinks haven't yet gotten warm from the listening i've done so far. Transformer is 160 VA 2x18V from RS that i got cheap off a guy. Bridge rectifiers into a homemade PSU board (basically just a place to solder the caps to) made so i could use some surplus 15.000 uF caps. I had originally planned to go dual mono, but that turned out to be impossible given the space.
Last photo shows the little mini chassis on top of the 4U deluxe which holds the F6. Next to it, the kuartlotron in one of the bigger galaxy chassis.
Anyways, just wanted to share and recommend this design to anyone on the fence - for not a lot you can make a very nice little amp. Hats off and thanks for sharing the design.
IT is driven by a Kuartlotron preamp, and i can warmly recommend the combination. There is plenty of gain in the LM3886 to make me not miss gain in the preamp. In fact, i haven't gotten past halfways on the volume control. With the F6, i quickly start missing the gain on my BA-3 preamp, but for the gain of the OS LM3886 it is spot on.
I put the amp in a mini dissipante from modushop, tight but very nice chassis, and the heatsinks haven't yet gotten warm from the listening i've done so far. Transformer is 160 VA 2x18V from RS that i got cheap off a guy. Bridge rectifiers into a homemade PSU board (basically just a place to solder the caps to) made so i could use some surplus 15.000 uF caps. I had originally planned to go dual mono, but that turned out to be impossible given the space.
Last photo shows the little mini chassis on top of the 4U deluxe which holds the F6. Next to it, the kuartlotron in one of the bigger galaxy chassis.
Anyways, just wanted to share and recommend this design to anyone on the fence - for not a lot you can make a very nice little amp. Hats off and thanks for sharing the design.
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Have fun building
Hello. Is it possible to get a pdf or sprint file for this amp and psu.
I will be etching my own pcb, I suppose this is a dual side pcb, is there any specific connection i should follow while doing my own pcbs.
I was intending on getting them done from JLCpcb, but shipping period and charges have increased a lot due to current pandemic. So will etch pcbs.
If you could guide about connection between layers, how to stitch them.
You're not going to have fun etching at home. But here are the top and bottom in pdf.
Some points of attention:
- I didn't include all the vias in the print. You will have to see where you want some (and you absolutely need some right at the top near the lone smd resistor). The pictures from post 58 will guide you for that.
- Depending on your process, you might have to mirror the bottom (it's as seen from the top in the pdf).
- The board dimensions are 60*50mm. So you can check if you print it out at the right size.
- If I were to do it, I would probably edit the pictures to remove the top ground planes (right at the middle and at the right of the board).
- As usual, the worst parts to deal with will be the electrolytic caps.
- Eagle puts pads even at the side to which the components aren't connected (they're tht pads). You might want to etch or scrap these out to get more clearance in a pcb without mask.
Some points of attention:
- I didn't include all the vias in the print. You will have to see where you want some (and you absolutely need some right at the top near the lone smd resistor). The pictures from post 58 will guide you for that.
- Depending on your process, you might have to mirror the bottom (it's as seen from the top in the pdf).
- The board dimensions are 60*50mm. So you can check if you print it out at the right size.
- If I were to do it, I would probably edit the pictures to remove the top ground planes (right at the middle and at the right of the board).
- As usual, the worst parts to deal with will be the electrolytic caps.
- Eagle puts pads even at the side to which the components aren't connected (they're tht pads). You might want to etch or scrap these out to get more clearance in a pcb without mask.