For clarity about the optional gate resistors, R12 and R13, you must either install a resistor, or bridge the pads inside that footprint with solder. Otherwise the MOSFET gates are not connected to the JFETs . Special thanks to @wg45 
I think they are different enough offerings that there will be demand for both. The OG ACA is a simpler construction and has that single ended sound. Plus the MinMax kit will cost more, and we all know that DIY'ers love a good deal.
Different animals.
OG ACA a single ended beast, high bias current, lots of heat, benefits from a very clean PSU, struggles with 4 ohm speakers.
ACA Mini, a push - pull , low bias current, not so much heat, rare Harris MOSFETs, similar sound to F5, drives 4 ohm speakers sort of ok.
ACA MinMax - same topology as ACA Mini with increased bias and PSU voltage, more heat, hence needing bigger sinks, similar sound to F5, will drive 4 ohm speakers quite well.
the published schematic has the jfet drain and source pins reversed, are using them like that?
No, that's not the intention, schematic updated! Thank you for pointing that out (I believe someone did previously as well). All PCB versions have them the right way around.
Does anyone think there will be any value gained using a 3U chassis over the standard ACA chassis? I have both and am debating if the larger chassis is worth trying, or stick with the predrilled ACA. I may try using onboard 36V SMPS from Meanwell versus external. Anyone think that the SMPS PSU in the chassis is just going to be too noisy and I should buy an external brick? Maybe I should build a separate PSU box. 🤔
I'm getting ready to populate boards now so starting to ponder next steps and layout. I appreciate any input. I'm still pretty new at this. Thank you!
I'm getting ready to populate boards now so starting to ponder next steps and layout. I appreciate any input. I'm still pretty new at this. Thank you!
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Given that the ACA MinMax bears a striking resemblance to the F5m (!), it could be worthwhile to check out the F5m and F5m kit threads regarding different power output and chassis considerations.
@TungstenAudio
That's precisely where I have been the past few weeks poking around which sparked the thought about 3U. I went with the 4U for F5m, so now I have this 3U Mini chassis unused. I have two MEAN WELL LRS-50-36 and was pondering using one for each channel. I'll ponder the ideas a little more before choosing a path. Thank you!
That's precisely where I have been the past few weeks poking around which sparked the thought about 3U. I went with the 4U for F5m, so now I have this 3U Mini chassis unused. I have two MEAN WELL LRS-50-36 and was pondering using one for each channel. I'll ponder the ideas a little more before choosing a path. Thank you!
This is very interesting.
What about a small integrated (?)
I have these small ACP+ mono pcbs, and I got this small amp box.
Could somebody please measure the width of the pcb (hoping it is 60 mm or less...)
Also, what kind of power output into 4 or 8 ohm (?)
/PerJ (From Norway)
What about a small integrated (?)
I have these small ACP+ mono pcbs, and I got this small amp box.
Could somebody please measure the width of the pcb (hoping it is 60 mm or less...)
Also, what kind of power output into 4 or 8 ohm (?)
/PerJ (From Norway)
That chassis looks absolutely gorgeous although I personally would have kept HS black to maximize thermal performance. Good luck with the integrated build!
The MinMax PCBs are 60mm x 127mm. A bit more length is needed because one of the FETs extends beyond the board area, about 135mm total.
Nobody has done a direct measurement of output power yet, and it will depend on the bias current. Nelson Pass estimated "a bit more than 10 watt/ch into 8 ohms" when using a 36V PSU and 1A bias.
Me too. The chassis is actually a delivery from Aliexpress that went very wrong. Somewhere out there is someone with a black 3U power amp chassis + a couple of other black boxes...
Got a refound and bought the correct chassis from modubox instead.
I got to keep this chassis and up until now I didnt know what to do with it...
Got a refound and bought the correct chassis from modubox instead.
I got to keep this chassis and up until now I didnt know what to do with it...
Nelson, thanks !
They should (barely) fit then.
Will there be a kit with the pcbs and the components only (?)
Since I already have this chassis I dont need another one...
They should (barely) fit then.
Will there be a kit with the pcbs and the components only (?)
Since I already have this chassis I dont need another one...
This seems like a good time to expand on what's happening behind the scenes.
I've put together a "pioneer" batch of kits and sent them in to the diyAudio store warehouse. We expect this small initial batch to sell out quickly, but it is an important step because it limits the liability of any mistakes and subsequent corrections that may need to be made. I know this can be frustrating for eager builders, but it is necessary for those of us who rely on community feedback to build products. To set expectations, there will very likely be a period of time after the initial batch where the kits are out of stock. In that time I will be making a much larger production batch and waiting to hear from the pioneers about any problems that should be addressed before sending them to the warehouse. The kits will be much more available after the initial setup.
The store intends to sell these as complete kits. They provide the chassis and 36V PSU, while I supply the PCBs, components, wiring, connectors, switches, and a few other bits.
@perj Since you have a non-standard chassis the connectors and switches are probably not going to work, so I'm guessing you just want the PCBs and components? DM me and we'll work something out
I've put together a "pioneer" batch of kits and sent them in to the diyAudio store warehouse. We expect this small initial batch to sell out quickly, but it is an important step because it limits the liability of any mistakes and subsequent corrections that may need to be made. I know this can be frustrating for eager builders, but it is necessary for those of us who rely on community feedback to build products. To set expectations, there will very likely be a period of time after the initial batch where the kits are out of stock. In that time I will be making a much larger production batch and waiting to hear from the pioneers about any problems that should be addressed before sending them to the warehouse. The kits will be much more available after the initial setup.
The store intends to sell these as complete kits. They provide the chassis and 36V PSU, while I supply the PCBs, components, wiring, connectors, switches, and a few other bits.
@perj Since you have a non-standard chassis the connectors and switches are probably not going to work, so I'm guessing you just want the PCBs and components? DM me and we'll work something out
Hoping to be a pioneer on this one and participate a little more deeply around here.
Could you DM me to start the conversation (?) Something about moderation rules for members with few messages etc. Sorry about that.
And yes, I need just the pcbs and the components...
/PerJ
Ok, well that settles it. Knowing what Mr. Brock shared above, I'll do my best to try to be true to what the pioneer kit will use and go with ACA chassis and the external 36V Mean Well PSU from store. That's the info I needed to help me move past all this wishy washy pondering 😉 I was doing.
Thank you!
Thank you!