There was no other reason than availability. Even though 1F is listed in the BOM, the same 3.3F cap was shipped in the most recent iteration of the kit because a source was located.
This is what i got from diyaudio store:
When I asked Nelson about the change from 3.3F on the 10/2021 BOM to 1F on the 8/2022 BOM, he said either would be fine.
I decided to stay with the 3.3F Kyocera caps that were included in the first batch of ACA Minis in order to keep the cost down.
These were significantly less expensive than the 1F Cornell Dublier caps listed in the 8/2022 BOM.
good luck to diy experimentation to verify this. enjoy the music and tests. i initially used 3.3 2,7super cap in my initial build and other premium parts ordered
Just a thought - for those of us who are taking a DIY approach to buying the components - it would be useful to have some sort of change log to refer to, so that a complete kit of (correct) parts can be purchased in one go. Having to buy the odd new resistor or trimmer afterwards is relatively expensive.
Consider building an inventory of the most common components like resistors, caps, semiconductors, etc., buying in bulk. Most suppliers offer discounts for larger quantities of 10, 20 and so on of the same part. Once the DIY bug bites you you are very likely to build more projects, plus parts for repairs and stuff ups and these will come handy.
Once you've got that inventory established just replenish it as you go.
Then you'll only need to buy specific parts that are not very common, like 2sk170, when you need them.
Recycle!
Extract parts from old, broken, obsolete pieces of electronics, mostly nearly indestructible components like power resistors, switches, LEDs, film caps, heatsinks and so on. It's very easy and rewarding, you learn to unsolder, inspect and measure and will save you quite a bit in the long run.
Of course here I'm making the general assumption that you are new to this hobby, and I could be quite wrong.
The suggestions were offered only with good intentions in mind.
Cheers
Once you've got that inventory established just replenish it as you go.
Then you'll only need to buy specific parts that are not very common, like 2sk170, when you need them.
Recycle!
Extract parts from old, broken, obsolete pieces of electronics, mostly nearly indestructible components like power resistors, switches, LEDs, film caps, heatsinks and so on. It's very easy and rewarding, you learn to unsolder, inspect and measure and will save you quite a bit in the long run.
Of course here I'm making the general assumption that you are new to this hobby, and I could be quite wrong.
The suggestions were offered only with good intentions in mind.
Cheers
Far from new to the hobby; I built a JLH 10 watt class A amp in the early 70s along with many other audio projects, and renewed my interest during the recent lockdowns - two valve amps, ACA, B1K driving class D amp, Whammy and full range loudspeakers. I was spoilt in the early years with access to most parts during my time in the colour TV industry. I don't have the spare funds nor space to hold an inventory as you suggested, also knowing that majority of it will go unused in my advancing years - well, except for the odd valve or two.
Kit just arrived; horray!
Simple question: Do I need to insulate the transistors from the heatsinks? I have some kerafilm left over from my M2X. Or is it ok to just use some (non-insulating) thermal paste?
Simple question: Do I need to insulate the transistors from the heatsinks? I have some kerafilm left over from my M2X. Or is it ok to just use some (non-insulating) thermal paste?
Finally added papa Nelson's ACA mini to my hifi audio amplifiers collection. The ACA-mini class A push pull design runs with SL 24V 48W (energy efficient).
My next project is to have a good wooden case for the ACA-mini and start building the ACP+ preamp. Cheers everyone. Enjoy music and the hobby.
My next project is to have a good wooden case for the ACA-mini and start building the ACP+ preamp. Cheers everyone. Enjoy music and the hobby.
Attachments
@hbadger - As others have said... you don't need to.
I'd go a bit stronger and say... don't use Keratherm.
Why? Laziness... See below and the PCB layout in the article.
I'd go a bit stronger and say... don't use Keratherm.
Why? Laziness... See below and the PCB layout in the article.
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you have the choice of using Keratherm or thermal paste in the ACA mini build. I pick thermal adhesives as to the thermal conductivity (Watts/mk) spec. This will be another lengthy technical discussion but you need to balance cost, consider thermal properties and actual use, thermal performance etc
^ Leaving thermal conductivity out of the equation for the moment.
Keratherm would electrically isolate the transistors from the sinks... As long as people are aware of the recommended work to do in addition... okay... but why would one do that? You are correct that there is a choice, but ...
Keratherm would electrically isolate the transistors from the sinks... As long as people are aware of the recommended work to do in addition... okay... but why would one do that? You are correct that there is a choice, but ...
@hbadger - sometimes we get off on side conversations...
So, if it's unclear. Don't use Keratherm. I posted the reasons why, and people are welcome to disagree.
I am not sure if you bought the essentials and/or the completion kit... but if you look at the completion kit contents which includes everything else you need to build your ACA Mini... there's no Keratherm. There's not even any thermal paste. No Mica and goop... no little nylon washers... nada... zip... in that category of parts to electrically isolate the sinks or add extra thermal conductivity. If you isolate the back metal pad (and the center leg) of the part from the heatsinks, you alter the electrical connection used with the layout of the board. You change the circuit. That's okay ... if you know how to get around that... which I copied Nelson's recommended steps... My simpleton opinion is why would you do that? Maybe there is a good reason... but I don't know one.
So, what I'd do... is just attach those buggers to the sinks per the original concept of the designer himself and ride off happily into the sunset. If you happen to have some goop around... sure... smudge a teeny bit on there. Can't hurt.
Others (per the norm) are likely to disagree with my opinion, and I welcome it. I simply wanted to provide better clarity around my (fairly strong) opinion.
Most importantly, congratulations and good luck with the kit. Enjoy the tunes! It's absolutely fabulous.
So, if it's unclear. Don't use Keratherm. I posted the reasons why, and people are welcome to disagree.
I am not sure if you bought the essentials and/or the completion kit... but if you look at the completion kit contents which includes everything else you need to build your ACA Mini... there's no Keratherm. There's not even any thermal paste. No Mica and goop... no little nylon washers... nada... zip... in that category of parts to electrically isolate the sinks or add extra thermal conductivity. If you isolate the back metal pad (and the center leg) of the part from the heatsinks, you alter the electrical connection used with the layout of the board. You change the circuit. That's okay ... if you know how to get around that... which I copied Nelson's recommended steps... My simpleton opinion is why would you do that? Maybe there is a good reason... but I don't know one.
So, what I'd do... is just attach those buggers to the sinks per the original concept of the designer himself and ride off happily into the sunset. If you happen to have some goop around... sure... smudge a teeny bit on there. Can't hurt.
Others (per the norm) are likely to disagree with my opinion, and I welcome it. I simply wanted to provide better clarity around my (fairly strong) opinion.
Most importantly, congratulations and good luck with the kit. Enjoy the tunes! It's absolutely fabulous.
Thanks, everyone, for your replies. Basically I was wondering if I needed to insulate the transistors, because on some amps you do, including the Amp Camp Amp. The build guide for the ACA mini doesn't even mention this; it would help if it said "You do not need to insulate the transistors". Yes, I can look at the circuit diagram and see that the heatsinks are themselves connected to ground, and that since power comes from a wall-wart, there is no possibility for a ground loop, but that's getting past beginner-level mojo and makes me wonder if I didn't forget something else which is also just as obvious to an expert ("can't you just look at the circuit and see?") but not to me.
"attach those buggers to the sinks per the original concept of the designer himself" -- you see, I didn't know this was the concept of the designer, because "insulate the transistors" is pretty standard on most of the Nelson Pass amps I'm familiar with. So is it not mentioned on this one because "everyone knows you have to insulate transistors" and why mention the obvious, or because "this one is an exception where you don't have to insulate the transistors"?
An explicit call-out in the docs/build guide would be helpful.
Thankfully all of your answers above have given me the clarity I needed. As always, appreciate this forum.
"attach those buggers to the sinks per the original concept of the designer himself" -- you see, I didn't know this was the concept of the designer, because "insulate the transistors" is pretty standard on most of the Nelson Pass amps I'm familiar with. So is it not mentioned on this one because "everyone knows you have to insulate transistors" and why mention the obvious, or because "this one is an exception where you don't have to insulate the transistors"?
An explicit call-out in the docs/build guide would be helpful.
Thankfully all of your answers above have given me the clarity I needed. As always, appreciate this forum.
Now, I'm aware of a good reason...
Personally, I won't be adding insulators / cutting traces etc., but thank you for sharing why you may choose to. It's very valuable. Copied into the library for future reference.
Thank you!