If you think you can get better sound with your design, rather than Nelson Pass's design: at least try it his way before you try it your way. Maybe your way IS better. Maybe not. Wouldn't you like to know how much better (or worse) yours is, than his? Is your design 1% better sound? 500% better? Aren't you curious?
Hey there, new to the board. I enjoyed building two amps, working well in stereo and xlr bridged but when I try parallel mono they sound really muted and barely audible?
Just realized I missed the jumper across the top of the switch as I write this, will fix that first. Any other ideas?
Just realized I missed the jumper across the top of the switch as I write this, will fix that first. Any other ideas?
capacitor differences in monos
Hey there, I bought one ACA 1.8 built for a great deal, and then built one myself, I sorted the above issue btw..
I noticed that C2 in the amp that I bough built is black and a little squat in the kit that I built C2 is brown and a little taller. Using these as xlr monos should I be concerned about this part variation, is C2 super critical and is this something that I should look into fixing so both amps match?
Thanks!
Hey there, I bought one ACA 1.8 built for a great deal, and then built one myself, I sorted the above issue btw..
I noticed that C2 in the amp that I bough built is black and a little squat in the kit that I built C2 is brown and a little taller. Using these as xlr monos should I be concerned about this part variation, is C2 super critical and is this something that I should look into fixing so both amps match?
Thanks!
C2 is not critical at all, in fact very little is component wise with the ACA except for the PSU and input FET.
Input FET?
You mean the JFET, the SK170 buffer, or Q1, the IRFP240?
Asking cause some people will be confused.
As we know an N-channel JFET as a buffer is just that, a buffer, and like any buffer does not influence sound (not that much anyway), unlike Q1, a common source device which will have a major impact.
You mean the JFET, the SK170 buffer, or Q1, the IRFP240?
Asking cause some people will be confused.
As we know an N-channel JFET as a buffer is just that, a buffer, and like any buffer does not influence sound (not that much anyway), unlike Q1, a common source device which will have a major impact.
Thank you very much Mooly. I am going to work my way through these this weekend. For the 1st step: "1/ The supply voltage of 24 volts has to be correct entering the board (or as measured on the middle lead of Q2). Be extremely careful not to short to the other leads when checking."
Do I ground the black lead?
Do I ground the black lead?
Yes, the black lead goes to ground for checking the supply voltage but we never assume anything when fault-finding... such as 'what if' the grounds aren't wired correctly (floating).
To rule that out you can measure directly between the points where the 24v enters the PCB. It would be very unlikely for there to be a problem like that but never assume anything until it is proved to be good.
To rule that out you can measure directly between the points where the 24v enters the PCB. It would be very unlikely for there to be a problem like that but never assume anything until it is proved to be good.
Ah yes, that makes sense. So I should ground at the G on the board or I could even ground at the DC input to the box to be sure?
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OK so both sides read 23.8v so it looks like we are good there. I also spotted that my power button soldering was loose so I resoldered. When I plugged in the amp for stereo I got channel A crystal clear. So that's something!
Just have to troubleshoot channel B as there was no sound. I'll go through the steps. thank you so much for your help.
Just have to troubleshoot channel B as there was no sound. I'll go through the steps. thank you so much for your help.
One channel working is good as it allows you to compare.
If the FET's are about equally hot between channels and whilst also having a DC voltage of about 12 volts on the plus end of C1 (speaker coupling cap) then that is pretty good proof all the DC conditions are OK and the problem is most likely down to input or output wiring.
If the FET's are about equally hot between channels and whilst also having a DC voltage of about 12 volts on the plus end of C1 (speaker coupling cap) then that is pretty good proof all the DC conditions are OK and the problem is most likely down to input or output wiring.
Just a guess here, but I suspect that the big cap (C1) on channel B is not soldered in correctly.
The response you got when you measured between the speaker terminals on channel A is correct, it should increase over a period of time, it is charging the big cap (C1).
If you measure 989 ohms straight away on the B channel, it is likely the cap is not connected, so no output.
85%+ of ACA failures are poor soldering...
Alan
Hi everyone. This is my first diy electronics project with solder or multimeter. I was wondering if there were any guides to adding a headphone out? I dont want to use aca+ or whammy. Ive seen external speaker out to headphone adapters for speaker amps before, but was wondering if there was another easy path. I dont want to drill an extra hole into chassis but may still. I dont plan to use as monoblocks, so it there a way to use existing xlr out as a stereo headphone out? I read that as monoblock the mono changes the sonic signature, but Id like to retain that tubiness. Thank you, -Phil
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I know this is an incredibly long thread, but I'm pretty sure several members made these as dedicated headphone amps. Maybe do a search for that topic on this thread.
Thank you both. I will search harder and be less lazy.
Ive soldered one board except for transistor C1. Can those thick little tabs be bent to hold in place? Will also search this. Just wanted to share that Ive progressed (at snail pace). Finally was getting a grrove then got stuck on C1.
Ive soldered one board except for transistor C1. Can those thick little tabs be bent to hold in place? Will also search this. Just wanted to share that Ive progressed (at snail pace). Finally was getting a grrove then got stuck on C1.
C1? Do you mean Q1, the power FET?
You can bend lead wires gently but try not to sharply bend them as that fatigues the metal . Also never bend the leads where they emerge from the package as that can damage the package. Hold the leads carefully and bend a millimeter or two away from that point.
It is usually best to mechanically fit the parts to the heatsink first and solder last so that no mechanical stresses are applied to the devices when they are bolted down.
You can bend lead wires gently but try not to sharply bend them as that fatigues the metal . Also never bend the leads where they emerge from the package as that can damage the package. Hold the leads carefully and bend a millimeter or two away from that point.
It is usually best to mechanically fit the parts to the heatsink first and solder last so that no mechanical stresses are applied to the devices when they are bolted down.
The pins of "snap-in" capacitors shouldn't be bent. Bending might cause unnecessary stress where the pins exit the capacitor body. Just hold the capacitor in place and solder the pins to the board.
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It appears I've put a bit too much torque on the transistor screws...should I replace Keratherm insulator?
keratherm will endure, due to net incorporated in a middle
check for short between mid pin and case , it must be MegaOhms
check for short between mid pin and case , it must be MegaOhms