Amp Camp Amp - ACA

Zen Mod · 2021-01-15 10:26 am

not likely to get absolute symmetry

that's nature of circuit

chermann · 2021-01-15 12:15 pm

TonyTecson said:
perhaps, what you may want to do is to match the mosfets for equal transconductance and Vgs...you will need a lot of samples though....https://www.firstwatt.com/pdf/art_matching.pdf

i will do that if i have more time for audio...this week maybe...thx

TonyTecson · 2021-01-15 11:25 pm

Zen Mod said:
not likely to get absolute symmetry

that's nature of circuit

indeed, when i first built this amp, it was mistaken for a 300b set...

planet10 · 2021-01-16 3:06 am

verticalmammal said:
My HiVis are 4 ohm, looks like I forgot to mention that.

Another argument for parallel ACA.
dave

Zachik · 2021-01-19 3:26 am

How hot is it normal for the ACA to run?
Testing my fresh build, even before closing the top cover - this thing radiates heat!!
I am sure it does not help that I managed to stuff the middle with an ACP+ to create an integrated amp...

An externally hosted image should be here but it was not working when we last tested it.

6L6 · 2021-01-19 3:29 am

They run pretty hot. That's normal.

verticalmammal · 2021-01-19 3:29 am

planet10 said:
Another argument for parallel ACA.
dave

I've elected to build an F5T V2 with cascodes in dual mono.

astromo · 2021-01-19 4:11 am

Zachik said:
How hot is it normal for the ACA to run?
Testing my fresh build, even before closing the top cover - this thing radiates heat!!
I am sure it does not help that I managed to stuff the middle with an ACP+ to create an integrated amp...

Refer the master's temperature sensing guide in The Aleph-X thread @ Post #1858.

From what I know, heat sink temperature will depend on two things:

Where you set the amp's DC Balance;
How loud you play your music (in short, play loud - run cool).

Zachik · 2021-01-19 4:24 am

6L6 said:
They run pretty hot. That's normal.

astromo said:
Refer the master's temperature sensing guide in The Aleph-X thread @ Post #1858.

From what I know, heat sink temperature will depend on two things:

Where you set the amp's DC Balance;

How loud you play your music (in short, play loud - run cool).

My thermometer's 9V battery is dead and I do not have spares

Will get a new battery tomorrow, and reply with actual numeric values...

6L6 · 2021-01-19 4:50 am

Actual numbers are not that important. If the heatsinks are cooler than 55C (130F) it's good.

130 feels really really really hot, but does not instantly hurt. (Instant pain starts around 65C/150F) You can keep your hand on it for only a few seconds it's about that temperature.

If you can keep your hand on it for 10 seconds it's around 50C/120F. You've almost certainly never felt a solid state amp this temperature.

If its awfully warm but you don't actually need to remove your hand, it's 45C/115F and it just warms your room.

And what is almost certainly the most quoted post on the entire diyAudio site - which Astromo pointed you towards;

Nelson Pass said:
Well let's see if your temperature calibration nomenclature
matches mine:

Blimey hot is 10 seconds hands on = 45 deg C.
Crikey hot is 5 seconds = 50 deg C.
Bloody hot is 2 seconds = 55 deg C.
X*?@! is 60 deg C.

All of these are within an acceptable range, although
X*?@! is resrved for the more mature constructor.

TonyTecson · 2021-01-20 12:50 am

Actual numbers are not that important. If the heatsinks are cooler than 55C (130F) it's good.

yes, and once the equilibrium temperature is reached, it stays that way....actually when playing music, the thing cools down a bit so no worries of thermal runaways so common with bipolar amps...

Zachik · 2021-01-20 1:10 am

So... best to measure (worst case / highest) temperature when amp is on, but no music playing?

6L6 · 2021-01-20 2:08 am

You will never feel the amp being cooler when playing even loudly.

Just measure after it’s be on after 20-30 min or so.

astromo · 2021-01-20 2:09 am

Zachik, that's how I'd do it... and with the case cover / lid fitted in place and away from any air flow such as a nearby fan.

Give the amp plenty of time (1/2 hour or more) to stabilise and let the temperature of the components to come to equilibrium with the amp and the environment.

You should also note the ambient temperature. Important if you're running the amp in Winter conditions because then (simply) you can take the temperature differential and estimate how warm the unit is likely to get during Summer. Just take your typical hot day temperature and go from there.

Zachik · 2021-01-20 4:32 am

6L6 said:
You will never feel the amp being cooler when playing even loudly.

Just measure after it’s be on after 20-30 min or so.

astromo said:
Zachik, that's how I'd do it... and with the case cover / lid fitted in place and away from any air flow such as a nearby fan.

Give the amp plenty of time (1/2 hour or more) to stabilise and let the temperature of the components to come to equilibrium with the amp and the environment.

You should also note the ambient temperature. Important if you're running the amp in Winter conditions because then (simply) you can take the temperature differential and estimate how warm the unit is likely to get during Summer. Just take your typical hot day temperature and go from there.

Got it - will turn amp on, not even bother with playing music, just keep it on (and idle), and take measurements after 30 minutes.

6L6 · 2021-01-20 4:33 am

It makes more sense if you listen music instead of just having it sit there... :yes:

Zachik · 2021-01-20 4:42 am

6L6 said:
It makes more sense if you listen music instead of just having it sit there...

I am trying to cause maximum heat build-up. Measure worst case scenario...
If lower playing volume would yield higher temp. -> I extrapolated that no playing equals max heat?

6L6 · 2021-01-20 4:43 am

If you play sine waves full power into a load resistor, the amp might cool down a couple degrees. Music into a speaker? Nope.

TonyTecson · 2021-01-20 10:18 am

Zachik said:
I am trying to cause maximum heat build-up. Measure worst case scenario...
If lower playing volume would yield higher temp. -> I extrapolated that no playing equals max heat?

your ambient temperature also plays a big role, if your ambient is at 0*C, most likely a 30*C temp when the amp is stabilized...

Zachik · 2021-01-20 6:55 pm

OK - took some measurements this morning... For now - with the top cover open, which I know would not give worst case temp. measurements.
See attached photo as a reminder - I have a "standard ACA" with added ACP+ in the middle, which adds its own heat.

Here are my measurements (ambient = 20C):
Time: 0
* ACP+ Heatsinks: 20C
* ACA Heatsinks: 20C
Time: 5 minutes
* ACP+ Heatsinks: 44C
* ACA Heatsinks: 32C
Time: 10 minutes
* ACP+ Heatsinks: 50C
* ACA Heatsinks: 40C
Time: 20 minutes
* ACP+ Heatsinks: 56C
* ACA Heatsinks: 45C
Time: 30 minutes
* ACP+ Heatsinks: 62C
* ACA Heatsinks: 50C
Time: 40 minutes
* ACP+ Heatsinks: 63C
* ACA Heatsinks: 51C

Looks like after 40 minutes temp. is pretty stable. As expected.

So... taking into account the top cover was open - I am not too worried about the ACA getting too hot, but I have a concern with the ACP+ radiating 63C inside the closed case...

Any thoughts? Would the ACP+ become my downfall?

I can repeat the temp. measurements with top cover closed, but will not be able to measure the ACP+ heatsinks inside. Only ACA's big heatsinks, and the case top cover which would radiate some of the ACP+ heat I assume, but I won't be able to tell internal ambient or ACP+ heatsink temp.

Amp Camp Amp - ACA

Official Court Jester

Member

Member

frugal-phile™

Member

Moderator

Member

Member

Member

Moderator

Member

Member

Moderator

Member

Member

Moderator

Member

Moderator

Member

Member

Attachments