Amp Camp Amp - ACA

[kmj]

agh, as you probably can tell I haven't done this for the last decade or two and I wasn't really good then.
I'll try that.
Thank you.

 

[JamesHH]

Reporting in with what seems to be a success:

Took about seven hours. Sounds great driven directly from my PC, however the max volume is not too loud, so I think I may need a pre-amp.

 

[TonyTecson]

Ok, back again with the humming.
I have found the source but not the solution.
If I power up with no source connected the humm is much lower but as soon as I connect a source the humm is back.
I don't own a preamp yet (got parts and board for a BOZ and jFet BOZ) so I am limited to Chromecast audio and misc phones/tablets but battery or line powered doesn't matter.
I tried a starground with some alligator clips but that didn't do anything.
I then tried to elevate the signal ground by adding a 10R resistor (in series) between the RCA ground lug and the signal ground connector on the board but that didn't help either.

this is the reason i switched to using smps psu's...

 

[TonyTecson]

good job JamesHH....

 

[toobhed]

...just finished the ACA 1.6 with back panel power button...first power up everything worked perfect. This is the only electronic build, except the AC Preamp build, that I haven't had to troubleshoot in some way.



I'm driving it with the B1 Korg that was finished about a month ago and it's powering BOFU bookshelf speakers built years ago...very very nice and thanks out to Nelson and Jim for the guidance.


...still have two more 1.8's that will be used a monoblocks...


Mario

 

[Zen Mod]

whoa!

those blue lightning thingies are reaching out!!!

beware!!!!

 

[toobhed]

Exactly....like the antennae of a Roger Corman alien.....

 

[TonyTecson]

on blue led's i use a higher series resistor, like 22k to 47k instead of the 10k indicated, my blue leds did not require a lo of current...

 

[Zen Mod]

yup

modern ones are eating your brain, if you give them more than 1mA

 

[TonyTecson]

thanks, barely visible is what i like in my led's regardless of color....blue one's get by with 0.4mA....

 

[Zen Mod]

rule of thumb really - for each rail Volt, take one KOhm

if that's still too bright, just double it

that's at least one thing, for which I don't need calculator anymore

 

[kmj]

this is the reason i switched to using smps psu's...

I hade one of those but I wanted all in one case and the parts for the PSU was in the junk bin anyways.
The new internal wiring didn't help so replacing the rectifier bridge is the next step.
I noticed that the MURs run blistering hot so I'll replace them with 2x 50A bridges.

 

[TonyTecson]

i tried toroids, ei traffos and humming was the issue, can not tame the hum....what to do? smps to the rescue...

 

[TonyTecson]

rule of thumb really - for each rail Volt, take one KOhm

if that's still too bright, just double it

that's at least one thing, for which I don't need calculator anymore

i also heard NP say that in his interviews or lectures that he is also tired of calculations, he use a pot and then turned it to find the operating points is fine then get the equivalent fixed resistors....

 

[umut1001]

Hi.Can i use Meanwell LRS-150-24 ?It is much cheaper in my country.And according to specs it writes load regulation is +-0,5% much better than GST120A24 ?

 

[Stanislav]

i tried toroids, ei traffos and humming was the issue, can not tame the hum....what to do? smps to the rescue...

One sure way to kill hum is to use 2 trannies back to back, unfortunately only feasible for pre amp use due to cost and space constrains.
For linear supplies lots of RCLC plus CapMX followed by more RCRC.
N.B. It must be RCRC, not CRC.

So, at the end, Tony's advice is very sound, SMPS kills a few rabbits with one bullet.

 

[TonyTecson]

Hi.Can i use Meanwell LRS-150-24 ?It is much cheaper in my country.And according to specs it writes load regulation is +-0,5% much better than GST120A24 ?

yes, by all means, the price is not that high, but my 24v bricks cost may lower than the meanwell...https://shopee.ph/-sale-COD-AC-110v...ing-Power-Supply-Board-i.272828555.5444293507

 

[Zen Mod]

i also heard NP say that in his interviews or lectures that he is also tired of calculations, he use a pot and then turned it to find the operating points is fine then get the equivalent fixed resistors....

oh yeah

he's doing these things since right after moment of wheel invention ..........

second nature is thing of past, now he's doing it as first nature

 

[Dneu2011]

Ok. I tried the changes but it still blows the 2.5A before each transformer.

When I was testing on the bench I did NOT have the added 2.5A Fuses in front of each transformer which probably explains why each amp worked fine then.

Any harm in increasing the rear single fuse to 4A and increasing each fuse in front of each transformer to 2.75A or even 3A?

I’m quite embarrassed but I fixed my problem. A couple of the keratherm pads I used had been penetrated by the screw holes of my chassis (don’t think dirty, haha). The Irfp9140 on one of the boards was for sure sending voltage into the chassis and I caught it. I sanded the screw holes and swapped out all the keratherm with mica and thermal paste and everything is working perfectly.

 

[kmj]

i tried toroids, ei traffos and humming was the issue, can not tame the hum....what to do? smps to the rescue...

I fired up only one channel and still buzzing.
Reconnected the old 19V laptopbrick and dead-quite (just as you said).
I don't want an external supply so I found a cheap 24V 5A SMPS that I plan on mounting inside the chassi.
I just hope it doesn't die due to the heat.

DC 24V aluminiumlegering interna stromforsorjningar for LED-skarm, CCTV, stromforsorjningsadapter for LED-skarm Ljusstang 3D-skrivare(24V / 5A / 120W): Amazon.se: Electronics