Amp Camp Amp - ACA

[HemiBooch]

A few additional notes:
1) the bad amp seems to generate no heat, the good one gets warm on the heatsinks pretty quickly
2) bad amp passes signal, buy very low amplitude and very distorted
3) I checked the Keratherm on both, all sheets are good, i.e. no holes, tears, etc.

 

[rnjorge]

Hemi:

This may sound too basic, and probably you did it already but have you tried swapping PSUs from good to bad?

 

[HemiBooch]

rnjorge: Yes - swapped PSUs and have eliminated many other variables as well, e.g. tried different preamps, different sources, etc.

 

[Zen Mod]

DIY friends. Finally had an opportunity to take and post some photos of my wayward 1st attempts at building amps.
So, first, 4 photos of the good one.
Then, 4 photos of the bad one.
The ugly? Well, one look at my soldering...
Thanks for any and all sleuthing to help this rookie DIYer...
I must confess, about ready to throw in the towel

good one is good by sheer luck

bad one is bad most likely because of bad soldering , all over the place

remove pcb from htsnk , inspect and redo ............ everything

if your solder iron is too weak , find more powerful one

 

[HemiBooch]

good one is good by sheer luck

bad one is bad most likely because of bad soldering , all over the place

remove pcb from htsnk , inspect and redo ............ everything

if your solder iron is too weak , find more powerful one

OK - what do I look for to ensure a proper solder iron?

 

[Zen Mod]

well , plenty of tutorials on ootoobe , much more informative than I could write here

I believe you can find cheap soldering station in power range of 50W and do everything what amateur needs

after decades of using cheapest ones , same as pro range , now I'm having two of these on my bench

I need big bada$$ 60W only for crudest speaker terminals

also - it pays off finding some old pcb (old TV or PC Monitor or whatever , and have some fun desoldering and soldering

 

[HemiBooch]

OK - thanks guys. Looks like my soldering needs a lot of practice and a better tool for the job. You are all gracious and helpful, and most appreciated.

 

[Variac]

Seems like you could reheat each joint a bit hotter, maybe you were afraid to overheat stuff. And if the solder doesn't flow then get some flux and paint it on the joint and reheat. Make sure there are no shorts, I see some wire strands close to each other..

My initial trouble shooting routine:

- make sure resistors are correct values- esp. the ones with or without K in the value.
-Make sure caps are inserted with the plus lead in the correct hole
-Make sure the tiny transistors are in the right places.
-reheat each joint until it flows better, sometime feeding in a bit more solder to add flux.
-check no "whiskers " of solder or strands of wire are shorting something out..

 

[koja]

as a suggestion: the ACA kit should offer the DPST version of the same switch so one can optionally implement a relay on the speaker output to reduce the turn off thump. I just did it and I had to break the original switches as I could not pry them out of the front plate. just saying...

 

[HemiBooch]

Re-soldering in my future...

Seems like you could reheat each joint a bit hotter, maybe you were afraid to overheat stuff. And if the solder doesn't flow then get some flux and paint it on the joint and reheat. Make sure there are no shorts, I see some wire strands close to each other..

My initial trouble shooting routine:

- make sure resistors are correct values- esp. the ones with or without K in the value.
-Make sure caps are inserted with the plus lead in the correct hole
-Make sure the tiny transistors are in the right places.
-reheat each joint until it flows better, sometime feeding in a bit more solder to add flux.
-check no "whiskers " of solder or strands of wire are shorting something out..

Thanks Variac:
Will re-do everything and hopefully my skills are good enough to now to make this thing sing!

 

[kpsthakur]

Also please test your MOSFET's...n good luck


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[ZacharyP]

Initially I planned to build a b1 buffer, but I'm not sure if 2vrms is enough to drive both channels of the ACA to clipping. This leads me in search of a low-gain preamp that I can use with my ACA.

Any recommendations or thoughts?

 

[kpsthakur]

Yeah, B1 can make it loud enough, but not make it clip, use BA-3 frontend


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[ZacharyP]

How much gain in the BA3 front-end? I don't need much, maybe 4x-to 8x. My dac outputs 2.1vrms, and I believe the ACA needs 3-4vrms to be able to drive to clipping.

 

[Dennis Hui]

Hi ZacharyP,

The ACA with gain of 14dB (x5) will clip on a 2.1V rms input:
2.1V rms x 5 = 10.5V rms which is over 29V peak-to-peak.
This is significantly higher than the 19V rail voltage of the ACA.

Cheers,
Dennis

 

[ZacharyP]

Thank you for the clear and concise answer my friend. B1 it is!

 

[vdi_nenna]

How much gain in the BA3 front-end? I don't need much, maybe 4x-to 8x. My dac outputs 2.1vrms, and I believe the ACA needs 3-4vrms to be able to drive to clipping.

Build a boz-j. Simple, has gain and sounds way better than its parts count would suggest.

Currently driving an ACA.

This is my second boz-j. Sounds a little better than my first, probably because I left the power supply outside the main box. This one will be for sale. I don't need two.

Vince

 

[ZacharyP]

You have a pm

 

[taj94]

I want to find a preamp for ACA, somebody give me a hint,plz?

 

[kpsthakur]

B1 please


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