Thanks, you definitely got me on the case of tracking down shorts. I had gotten a little lazy with putting things back together as I had don it a few times before, I had a disconnected ground and a flipped output, and before that I shorted a speaker terminal to the chassis, none of which I'd ever done before. I guess the moral of the story is never rush and always check your work. All good and running now, these things are indestructible and the boards are of such high quality that the hold up to a lot of experimentation with part swapping.
I have the ACA with a ton of mods (new output transistors and resistors to protect the jfet's) on dual 36v meanwells (the ones for the Sony Vfet). Some awesome folks have come up with a lot of great ideas for modding this amp!
yeah, I was putting it back together while watching the Celtics game with my son...so made a few mistakes in wiring that I don't usually make. It was good practice to heck continuity and for shorts, thanks again for sending me in that direction!Didn't turn the page 😳
So all good then
My beloved Musical Fidelity A1 finally gave up. I had it repaired mulitiple times. I loved the amp but it was very unreliable. But I thought of using the heat sink for an amp camp amp. It sounds great and the memory of MF A1 lives on 👍First I planned to build it in the MF A1 case but it wasn't enough space. I plan to use the rest of then case for a nice preamp.
why do you specifically want a photo?
I currently dont have one but can certainly oblige next time I'm rigged up testing.
In the meantime..
Siglent 1104X-E scope and 1032X F-Gen. 1Khz sine @ ~1W, 8 ohm load (wire wound). Gen (@50ohm) direct to amp RCA input via BNC coax, amp out direct to load via BNC coax then 1x scope probe across load. The same test setup on my F5 (P3 50% by Z) mirrored Nelson's published F5 H2 & H3 distortion plot nicely. Coupla days ago I posted those results on the F5 thread.. was with my ol' scope
.. ZenMod
I realise a lot of people dont take much away from these types of measurements, but when new to building amps like I am its probably the best reassurance a person can get to prove they've done things correct.
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Hello World! My first post to diyAudio. I'm mid-build on an ACA, my first amp 🙂, and truly enjoying it. Because the complete kits were sold out, I bought the ACA chassis, PS, and boards, was gifted most of the board components, but still trying to source the hardware and a few of the back panel components.
I have a few questions, (please pardon the noob and have mercy if I'm breaking some rules I'm not aware of):
1) Am I correct that the screws for the MOSFETS are M3x12mm?
2) For the DC power jack, is it a 2.1 mm x 5.5 or a 2.5 mm x 5.5 mm? I'm using the Meanwell 24v PS from diyaudio store. I've found a few candidates that look like what's used in the kit but can't determine the inner diameter.
3) For the Keratherm, it looks like one piece, ~32x23, just fits the footprint of two of the IRFP240 if cut in half. Is it Ok cut it in half? All the pics in the (awesome) ACA build guide show oversize keratherm and being a total beginner I have no idea if the oversize Keratherm is key to its thermal performance. Since I plan to build more amps, I'm trying to maximize what I can get out of the 10 piece pack.
Thank you!
I have a few questions, (please pardon the noob and have mercy if I'm breaking some rules I'm not aware of):
1) Am I correct that the screws for the MOSFETS are M3x12mm?
2) For the DC power jack, is it a 2.1 mm x 5.5 or a 2.5 mm x 5.5 mm? I'm using the Meanwell 24v PS from diyaudio store. I've found a few candidates that look like what's used in the kit but can't determine the inner diameter.
3) For the Keratherm, it looks like one piece, ~32x23, just fits the footprint of two of the IRFP240 if cut in half. Is it Ok cut it in half? All the pics in the (awesome) ACA build guide show oversize keratherm and being a total beginner I have no idea if the oversize Keratherm is key to its thermal performance. Since I plan to build more amps, I'm trying to maximize what I can get out of the 10 piece pack.
Thank you!
Since you plan to build more amplifiers, "investments" like these will probably help both present-day-you and also future-you
(Amazon link 1)
(Amazon link 2)
(Amazon link 3)
_
(Amazon link 1)
(Amazon link 2)
(Amazon link 3)
_
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well I played about with this new scope till 2am this morning, then up @ 7am and at it again till now.. 3:30pm.
Think I sorted the problem. My vertical resolution was out plus the sample size was too big. How do these look now?
Have also uploaded the test setup
Screen shots #40 & #42 are only the sig gen into the scope; 2.83Vrms @ 1Khz sine
Screen shots #33 & #30 are the ACA; 1kHz sine, 1W @ 8 ohm
Lastly shot #45 is the ACA in bridged mono; 1kHz sine, 1W @ 8 ohm
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@Mark Johnson thank for the pointers. That Oria flexi shaft is pretty cool looking.
I had put my calipers on the Meanwell plug but wasn't able to determine if the hole for the pin was designed for 2.1 or 2.5 mm, hence the question for someone who might have one of the plugs spec'd in the kit. This evening I was able to buy one of each. It appears that either size will work, as in they both measure 24v when the PS is pluged in (and not shorted, hahaha)
Any thoughts from anyone on cutting one of the standard pieces of Keratherm in half to fit the footprint of the IRFP240?
I had put my calipers on the Meanwell plug but wasn't able to determine if the hole for the pin was designed for 2.1 or 2.5 mm, hence the question for someone who might have one of the plugs spec'd in the kit. This evening I was able to buy one of each. It appears that either size will work, as in they both measure 24v when the PS is pluged in (and not shorted, hahaha)
Any thoughts from anyone on cutting one of the standard pieces of Keratherm in half to fit the footprint of the IRFP240?
You'll be fine cutting the Keratherm in half, as long as it completely covers the base of the transistor.
is there a correction to the ACA rear panel wiring compared to what's stated in the V1.8 D-10 build manual off the diy store?
I'm trying go mono RCA bridged. I followed the rear panel guide.. switch up, speaker to left and right negatives, RCA into left channel but I'm only getting 7W into 8 ohm.. and only one channel is getting warm?!? I quadrupally checked everything but cant see whats not matching the schematic
The amp work fine in stereo, 7+W per side.
photo's below of my ACA rear panel and relevant manual pages
I'm trying go mono RCA bridged. I followed the rear panel guide.. switch up, speaker to left and right negatives, RCA into left channel but I'm only getting 7W into 8 ohm.. and only one channel is getting warm?!? I quadrupally checked everything but cant see whats not matching the schematic
The amp work fine in stereo, 7+W per side.
photo's below of my ACA rear panel and relevant manual pages
Attachments
is there a correction to the ACA rear panel wiring compared to what's stated in the V1.8 D-10 build manual off the diy store?
I'm trying go mono RCA bridged. I followed the rear panel guide.. switch up, speaker to left and right negatives, RCA into left channel but I'm only getting 7W into 8 ohm.. and only one channel is getting warm?!? I quadrupally checked everything but cant see whats not matching the schematic
The amp work fine in stereo, 7+W per side.
photo's below of my ACA rear panel and relevant manual pages
There is something wrong with your statement?
If one channel is 'cold' it cannot be working. Double check the stereo mode.
Then if your scope has a ground / earth connection, be careful not to accidentally short one output (via the earth connection from the scope to ACA) when testing in bridged mode.
nothing wrong with the statement Al, probably just long winded - sorry mate. Yes I'm aware the ACA's reverses polarity so careful probing.
When the mode switch is up, the rear pins dont make sense.. to me. I've never bridged an amp before, inputs should be common, shouldn't they?