Start by re-flowing all the solder pads. See Q1 and Q2 for example, you can see day light through some of the holes... not good. Hard to tell from the picture, but you look to have missed a few too. Use more solder, there should be enough solder to fill the hole and make a small 'cone' both sides of the board.
Also some of the rear connector wires do not look 'finished', see the black one. Re-flow them too.
There have been worse first attempts, take your time, it will be ok.
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Agree, solder joints. The ones with heavy conductors (FETs, heavy wire) soak up a lot of heat, you need to keep the iron on them long enough to get everything hot so the solder will flow, especially if your iron is under-powered. If it's variable temperature, crank it up another 30 or 40 degrees on these joints.
if one is not having heavier gauge tip for Iron , for heavier points ( wires , mosfet pins) ,then clean the tip thoroughly and try to make contact with fatter area of the tip , thus having higher temperature of soldering , resulting from higher temperature inertia
tiny tip is going cold faster than heater can heat it .... so - with same heater power , bigger tip is clever thing to have
or 2 or 3 same Iron Stations , each having different tip
tiny tip is going cold faster than heater can heat it .... so - with same heater power , bigger tip is clever thing to have
or 2 or 3 same Iron Stations , each having different tip
Thank you everyone. Feeling a lot of love here
Happy to report after reflowing all joints ... it’s singing beautifully now !!!
I didn’t touch the good side... I guess I will when it happens ;-)
Again thank you everyone. My first ACA !!!
SWEET! Good job. Happy listening. BTW, yes, it is supposed to run pretty hot...
On my system I find if I turn ACA’s on first, and preamp maybe 30 seconds later or so, the bump is either gone or significantly diminished. I realize this makes no sense since the amps are directly connected to speakers, but there is a clear difference in behavior. But each time nothing can be heard till my preamp gets turned on, and if that’s on first and ACA’s 2nd the bump is pronounced. Maybe that’s just a quirk of my system, but worth a try.
one need to learn is that pop! in speakers significant or not
if you're switching on AC side (pre-switcher PSU) there likely not be any pop!
if you're switching ON on DC side ( post switcher PSU) , there can be pop!
so , for each particular case , it is important how big that pop! is , in terms of mm of bass cone movement ?
even sissy lowthers are completely ok with few mm of movement , and they're something as measure of fragility
if you're switching on AC side (pre-switcher PSU) there likely not be any pop!
if you're switching ON on DC side ( post switcher PSU) , there can be pop!
so , for each particular case , it is important how big that pop! is , in terms of mm of bass cone movement ?
even sissy lowthers are completely ok with few mm of movement , and they're something as measure of fragility
I switched to regulated power supply and the turn on became almost completely silent. ( the sound quality also improved quite dramatically ) So if ur desparate to stop the noise this is one fix - but personally, I don't see what the problem is ( unless you find the sound embarressingly close to the sound of a fart 
)
)
I built a pair of v1.6 from diy store, then I built a Balanced Zen line stage with a separate power supply. The BZLS power supply has two mains connectors on the back panel which are switched by the power supply. When I turn on the BZLS power supply, ALL my components turn on, no pops. Because all the other components are plugged into the BZLS, including the two power supplies for the ACA's, no hum, no ground loops. With the XLR's used on the ACA's no noise even at wide open throttle.
That's how I solved it, and it's exactly what I expect from a Nelson Pass amp and preamp, going back to Threshold days.
That's how I solved it, and it's exactly what I expect from a Nelson Pass amp and preamp, going back to Threshold days.
The power supply that comes with the kit is regulated, did you mean a linear supply? If so, can you specify which one you're using?
Request to any forum member: I purchased 2 of the amp kits a little while ago. Since then I have developed a tremor which will prevent me from putting them together myself.. I am looking to pay a forum member to assemble my 2 amps. I have tried to find someone locally (I am in Boca Raton, FL) without any success. PLease let me know if you are able to help. I had purchased all of needed supplies and will Fedex them to you and of course pay for the return. THank you, Paul Hart - please email or if you would like, call me - my number is *******. Thank you for considering my request.
Mod Edit. Paul, this is a copy of your original post. Hopefully you will get someone local who is able to help you in this
Mod Edit. Paul, this is a copy of your original post. Hopefully you will get someone local who is able to help you in this
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Cheap Amp Camp Amp
My attempt at a cheap ACA. I bought the PCBs from the diyaudio store ($15) an old Sony amp (£0.99) and used its case, speaker posts and RCA jacks, bought an old laptop SMPS (£5), managed to salvage heat sinks and capacitors (free), bought transistors and power resistors from a local shop (£15), total cost about £36.
Powered it up and it worked first time - happy days! Its a bit quiet fed from my Iphone headphone output, and feeding my KEF 104, but I'm currently bodging the trimmer pot with a couple of resistor so I'm hoping (fingers crossed?) that once I've set the bias properly the volume will come up. If not I'll be after a pre-amp or a better music source I guess. I have a couple of salvaged 24V fans that I'll add given the suboptimal heat sink arrangement...
My attempt at a cheap ACA. I bought the PCBs from the diyaudio store ($15) an old Sony amp (£0.99) and used its case, speaker posts and RCA jacks, bought an old laptop SMPS (£5), managed to salvage heat sinks and capacitors (free), bought transistors and power resistors from a local shop (£15), total cost about £36.
Powered it up and it worked first time - happy days! Its a bit quiet fed from my Iphone headphone output, and feeding my KEF 104, but I'm currently bodging the trimmer pot with a couple of resistor so I'm hoping (fingers crossed?) that once I've set the bias properly the volume will come up. If not I'll be after a pre-amp or a better music source I guess. I have a couple of salvaged 24V fans that I'll add given the suboptimal heat sink arrangement...
Attachments
As I’ve mentioned, I wish we could have a bunch of people make these amps “on the cheap”. University students must need good tunes - at least we did back in the day! And don’t have much money - at least we didn’t back in the day! So where are you?
Post photos of your TrashACA’s. And if there’s at least 10 there will be a prize for the coolest, cheapest and/or most artistic one. If you use a PCB please use a diyAudio’s as iaaeap did, but if it’s “dead bug style” (leads from components just twisted together and soldered) that fine too. No chassis required but it should be movable....
Post photos of your TrashACA’s. And if there’s at least 10 there will be a prize for the coolest, cheapest and/or most artistic one. If you use a PCB please use a diyAudio’s as iaaeap did, but if it’s “dead bug style” (leads from components just twisted together and soldered) that fine too. No chassis required but it should be movable....
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Indeed, it's fun to see old gear get turned into a Q ship by the addition of some really nice class A amplifier modules hidden inside.That's the Spirit!
The ACA responds well to a 24V supply, along with some tweaks to the input and feedback resistors. I like using 20k for R11 and 90.9k for R12. The trim pot should be adjusted to get about 12.2V for the "bias voltage" to take advantage of the higher rail voltage. Those changes will get your power output closer to 9 Watts, which will be a noticeable improvement.
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