Amp Camp Amp - ACA

[MrJohn]

I have even forgot to solder both sides of the .47 Ohm resistors on one board and the amp didn't mind. Took me a while to figure that one out.

I didn't even know you were supposed to do that. Am I supposed to do that on the .68 Ohm resistors too? What was it doing that it took you a while to figure it out?

I'm looking these these instructions, and the v1.8 instructions for the back panel... am I missing anything?

 

[Signal lost]

The resistor has two leads that pass through the circuit board. I only soldered one lead not both. The board was mounted to a silver heat sink and that made it look like there was solder in the hole. Then I noticed that the flashlight beam went right through the hole. Just had to un-mount the board and solder it up. Could have done it from the top but I wanted to see if I missed any thing else.

 

[MrJohn]

The resistor has two leads that pass through the circuit board. I only soldered one lead not both.

I misunderstood your original comment, I thought you meant both sides as in top and bottom of the board... then I looked at the instruction photos and was thinking to myself that there looks to be a considerable amount of solder on the top side (vs flat).

 

[Signal lost]

I was testing to see if these heatsinks I had were big enough. They would heat up then level out. But they were working much better than expected meaning cooler that they should be. So I did not have the amp connected to an input or speakers. The led was on.

 

[Signal lost]

If your iron is hot enough, clean and tiinned well the joint will heat evenly and solder will flow from the bottom through the hole to the top to the board. Good solder and good technique are your friends.

 

[MrJohn]

If your iron is hot enough, clean and tiinned well the joint will heat evenly and solder will flow from the bottom through the hole to the top to the board. Good solder and good technique are your friends.

Thank you for the tip!

 

[johnah5]

Part numbers and source?

Q3 is bjt , type written on schematic

Q4 is JFet m type written on schematic

you can buy either that one (JFet) or LSK170A or LSK 170B or LSK170C
Store

Haven't got an answer from the DIYstore. Do you know where I can buy these? Do that have to be "matched"? I am dead in the water until I get one replacement part and a new Pentintometer.

Thanks
jh

 

[Signal lost]

They do not need to be matched for the ACA as it only has one per channel. The store has jfets listed under active devices but sell them as a quad (4) set. The potentiometer is a 5K ohm value and can be purchased in an assortment on amazon. Search for 5K potentiometer pc mount.

 

[johnah5]

Ok they sent me to mouser for the RCA jacks. If I can get them there it would be best. Here is what I am seeing at moser
https://www.mouser.com/ProductDetail/InterFET/J112?qs=1NkvD5QbL4GoQ/9vbJgniQ==

 

[Zen Mod]

Store

just buy cheapest possible N channel JFets

do not search around

you don't need e-mail to finish purchase from Store

 

[johnah5]

Does it matter which one?

They do not need to be matched for the ACA as it only has one per channel. The store has jfets listed under active devices but sell them as a quad (4) set. The potentiometer is a 5K ohm value and can be purchased in an assortment on amazon. Search for 5K potentiometer pc mount.

The jfets are 6-8mA and 8-11mA? I also need the Q3 transistor which I was told was a bjt? Will that come in the set of 4? Trying to get everything shipped at the same time.
Thanks
jh

 

[Variac]

Breakthrough! : DigiKey now stocks Linear Systems JFETS as specified for the ACA. Here’s what you need, and they don’t need to be matched as there is only one per channel.

ACA JFETS at DigiKey

They do not need to be matched for the ACA as it only has one per channel. The store has jfets listed under active devices but sell them as a quad (4) set. The potentiometer is a 5K ohm value and can be purchased in an assortment on amazon. Search for 5K potentiometer pc mount.

 

[Zen Mod]

ZTX - you can buy it anywhere, available as Popcorns, so really no need for Store to have them separately

JFets - as I said - buy cheapest ones, N channel, you can find in Store

for ACA, their current range (suffix) is not significant

 

[canonken]

Has anyone added taller feet to their ACA to let more air under, and thru the chassis and heatsinks? And if so, did it work? I guess I could test it stock height and 'lifted' and measure, but curious if anyone has some similar and gotten an outcome they like.

 

[Variac]

I suspect it makes more difference that many would expect! I do know that putting it on a shelf with another shelf 30cm above makes it a lot hotter. I also know one person who put an ACA in a 30x30x30 cm niche, closed on the back and the amp got too hot to touch!

So best Is on a shelf with no sides or top, ie open air, and yeah, taller feet or on a pedestal. Obviosly don’t put a preamp on top!

 

[Zen Mod]

Yo, Iguana Mate!

this is really Papaland!

you Boyz even named JFet quartets and octets, by Pa!

 

[Signal lost]

Used some left over pieces of Baltic birch to lift the chassis 18mm and it seemed to run cooler. Really helps more with my diy chassis as the heat sink is smaller than the store chassis.

 

[mraudioguru]

I use Black Diamond Racing, (MK3) cones under mine. Not only does it sound better, but runs cooler too!

 

[Nelson Pass]

you Boyz even named JFet quartets and octets, by Pa!

Actually the ones currently in the store were tested by me.

 

[johnah5]

I love my ACA. I am listening through Freya preamp tube stage and yes I don't have the center channel clarity like the other amps but this thing just sounds good. Thanks Nelson.

End of the week will have the replacement parts in and will get to here two ACAs in mono.

JH