Amp Camp Amp - ACA

[Zen Mod]

may be or may not - depending of source in front and safety gnd

however , I'm not expecting too much trouble in either way

 

[Rewind]

Guess I have to figure out this one kamikaze style.

 

[Zen Mod]

all wrong could be some hum

if you want to play safe = isolate audio gnd of both pcbs and route them each through 10R NTC to case

 

[Rewind]

Audio ground, i.e. the ground on the RCA connections?

 

[Zen Mod]

RCA isolated from case , so audio gnd is on channel pcb

use exactly same eyelet on pcb which you are going to insulate from case

 

[Variac]

The "positive" connections on the case are ground and the "negative" are live as Papa wanted it to be non-inverting. So using it with headphones for example might require a moment of thought.

 

[Rewind]

The "positive" connections on the case are ground and the "negative" are live as Papa wanted it to be non-inverting. So using it with headphones for example might require a moment of thought.

Are you talking about the positive connections of the RCA connection, or the positive power supply cables?

Back to the question, can two ACA share one heatsink, as long as the RCA connections are isolated from each other? The heatsink is aluminum and would conduct electricity through the mounting holes on the PCBs. The mounting holes is connected to ground in the individual PCBs.

 

[Zen Mod]

I'm staying with same replies

 

[Variac]

The connections to the speaker terminals. Sorry I realize that was confusing..

 

[Rewind]

RCA isolated from case , so audio gnd is on channel pcb

use exactly same eyelet on pcb which you are going to insulate from case

This is the first time you mentioned eyelets on the pcb. There are a few eyelets on the pcb. Do you mean an eyelet that is connected to the RCA connections?

Since the poles on the speaker connections are reversed, maybe they also need isolation from the heatsink.

I may just as well saw the big heatsink in two.

 

[Zen Mod]

eyelet , meaning screw hole having gnd connected - exactly that one you are asking about

 

[bcmbob]

Rewind, you could help us all if you posted a few photos of your project. Most RCAs and speaker posts have insulation/isolation designed in. PCB mounting holes generally don't have continuity to ground - so I'm getting lost.

PICTURES PLEASE !

 

[6L6]

I think the question is about this screw -

In the original build, the PCB is attached to gnd through a trace on the PCB, thence to the chassis. Being a monoblock with a isolated supply, this makes no ground-loop issues.

Making it stereo in the same chassis will probably hum.

I would begin by mounting the PCB with nylon hardware. Then, how exactily to ground it? I don't know yet, let's see if wiser heads have any ideas...

 

[Zen Mod]

I said - isolate , put wire , then through NTC to case .

though ,

let's see if wiser heads have any ideas...

 

[Rewind]

I have ordered nylon standoffs, but I want to listen to it this weekend. Maybe the 1.2kg aluminum heatsink is too small for both boards though.

This is what I have to work with:

I have two 19.5V (4.5A) laptop adapters. I also posted some examples of the standoffs, and connections. None are isolating in any way.

My alternative is to saw the heatsink in two (an ugly job with a hobby saw), and then isolate the speaker connections and the rca connections and the heatsink from each other using some tasteful oak. That would look more like what the rest of you has created. But will 600 gram aluminum be enough for each amp? That is the weight of a cpu heatsink and CPUs give off between 20-70 watts.

 

[Zen Mod]

do not complicate

build normal , put 3 metal standofs on each pcb , solder wire on 4-th hole , route NTC to case

RCA and LS posts are isolated from case anyway

 

[cochleus]

I think if you used a couple of small quiet fans that heatsink would do the job.

 

[Rewind]

Okay, thanks. I don't actually have a 10R NTC yet. Will take a 2 weeks to get one.

The saw seem more and more alluring.

 

[bcmbob]

I have two 19.5V (4.5A) laptop adapters. ...........

But will 600 gram aluminum be enough for each amp? That is the weight of a cpu heatsink and CPUs give off between 20-70 watts.

........and connections. None are isolating in any way

So it sounds like you are building monoblocks (2 PS bricks) that simply share a single chassis, not stereo - is that correct?

The saw may be necessary only because your photos suggest the HS fins will be horizontal - vertical is more efficient and the two amps shouldn't be stacked. CPU heatsinks worked fine (very warm but not hot) on this build and yours appear about equal in metal content.

Don't understand why you say your RCAs and speaker posts are non-isolating.

 

[Rewind]

Yes. We are discussing about whether or not the ground of the two amps can mix by being connected to the same heatsink. The mounting holes on the PCB is part of the ground. Many think there will be hum if the grounds are not separate. But nobody seem to know really. Anyone dare to connect their two heatsinks together with crocodile clamps and listen what happens?

I do hope the heatsink will be enough. Looks like it from your pic. In the worst case I can add a fan.