I've updated the wiring diagram to include the XLR connector and rear switch for paralleling inputs.
Can anyone comment if it makes a difference that I'm showing the XLR ground connection straight to the DC jack ground, as compared to connecting to the RCA grounds, for example? They're all electrically connected together, and to the chassis.
Can anyone comment if it makes a difference that I'm showing the XLR ground connection straight to the DC jack ground, as compared to connecting to the RCA grounds, for example? They're all electrically connected together, and to the chassis.
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I really need a project like this right now. So many other projects in queue getting lost in the details. I need something straight forward I can just put together. I've been watching the store for weeks, waiting for this to become available. Or at least an ACA chassis, as I seen N Brock had some boards available. I was about to order an ACA chassis from Modushop. But now I see there is a Minmax page on the Diyaudiostore. Will the kit be listed soon? I don't want to order a chassis from Modushop and the kits become available while I'm waiting for a package from Italy.
Also, a little confused about the switch in the BOM. Why a DT switch? Wouldn't that only switch one channel on depending on the switch position? And that switch shows no rating for DC operation. Is that ok?
Also, a little confused about the switch in the BOM. Why a DT switch? Wouldn't that only switch one channel on depending on the switch position? And that switch shows no rating for DC operation. Is that ok?
I highly recommend the MiniMax if you're ok with doing all the wiring, which I find to be more challenging than stuffing the boards. It's good experience though.
I also highly recommend the ACA Redux as it also sounds great and no wiring! You can go from opening the box to playing music in 2-3 hours if you are diligent and practiced. I like the independent units for left and right as well.
Can't go wrong with either option, other than ACA Redux is available now on N. Brock's sales page, and ACA MiniMax appears to still be working initial rollout phase at diyaudio store.
Maybe just go with both. That's been my motto 😉
Sidenote: I found chassis shipping from Modushop to be pretty quick from Italy to Seattle. Typically under two weeks from order to arrival if it's in stock.
I also highly recommend the ACA Redux as it also sounds great and no wiring! You can go from opening the box to playing music in 2-3 hours if you are diligent and practiced. I like the independent units for left and right as well.
Can't go wrong with either option, other than ACA Redux is available now on N. Brock's sales page, and ACA MiniMax appears to still be working initial rollout phase at diyaudio store.
Maybe just go with both. That's been my motto 😉
Sidenote: I found chassis shipping from Modushop to be pretty quick from Italy to Seattle. Typically under two weeks from order to arrival if it's in stock.
Yes, but I don't know when exactly. The warehouse has 15 of my kits and is waiting for the ACA chassis to arrive. Perhaps two weeks, but since I have no control over that, I can make no guarantees.
It is dual throw because that's how the circuit was designed. It functions the same as the ACA mini, and I know there is some discussion in that thread if you'd like to dig into it more than the explanation I can give here. The switch shuts down the bias by bringing the JFET gates to ground rather than interrupting the DC input to the whole amp. If it were singe throw and the switch only disconnected that node from V+, the C4 capacitor would keep the amp on for a while as it slowly drained through R2, R3 and the LED (R0 + R4). Both channels can be connected to the same switch since they share power and ground rails. If I recall correctly, this was done to allow the supply capacitors to stay charged up as a way of limiting stress on the switch mode power supply.
As for the DC rating, thank you for asking! My recollection was that it was DC rated, but clearly it isn't, so maybe I've confused it with another option I looked at. Very little current goes through the switch, and I've been using it for a few months without issue, but I will be searching for a replacement with the appropriate DC rating to include in future kits.
Ha! I think the Minimax page was made invisible, as I cannot find it. Probably unintentional as it is not yet available.
Here's a preview listing https://reduxkits.com/products/aca-minmax
The complete kits won't be available on my site because I'm not providing the chassis or power supply, it's just on there for info.
The complete kits won't be available on my site because I'm not providing the chassis or power supply, it's just on there for info.
The gate resistors are needed when the MOSFETs have high gate capacitance, which in theory could stress the JFETs if you run square waves through the amp, or in extreme cases cause ringing / oscillation. I'd say they're pretty unlikely to be necessary for any typical build of this design.
The "downside" of using them is they can impose a limit on the high frequency bandwidth of the amplifier (by limiting the current into the gate), but this limit is well into the ultrasonic range in this instance and this is far from the only component that determines bandwidth. Have a look at the F5 and F5m which share a similar topology to the ACA Mini / MinMax. The F5 uses 47 ohm gate resistors while the F5m and ACA mini omit them, all reach well over 100 kHz at the output.
If you are of the "less is more" persuasion, leave them out. If you like the idea of a little extra JFET insurance, add them in.
The "downside" of using them is they can impose a limit on the high frequency bandwidth of the amplifier (by limiting the current into the gate), but this limit is well into the ultrasonic range in this instance and this is far from the only component that determines bandwidth. Have a look at the F5 and F5m which share a similar topology to the ACA Mini / MinMax. The F5 uses 47 ohm gate resistors while the F5m and ACA mini omit them, all reach well over 100 kHz at the output.
If you are of the "less is more" persuasion, leave them out. If you like the idea of a little extra JFET insurance, add them in.