Hi All
Well just powered on the two ACA I have, put the bowie on, different flac file, thought god that's rubbish noticed one of the channels LEDs not on........OK felt the power bricks one was cold swapped over, LED off swapped power supply to another channel and the othe one went dead, great one of the Ebay Chinese power supplies has given up, swapped the power leads to confirm and it is dead.
But now I come to the OCD part should I buy another new same rated power supply and drop in or, as I feel compelled to do, buy two so I have matched power supplies, knowing its cheap crap and better to have them from the same supplier so they might be at least be a better match L/H to R/H? power supplies are rated 19V 4.74A 90W
For the sake of another 12 quid I will feel relaxed and enjoy the music!!, but my question is. Is there a better choice power supply wise (without DIY as I havent finished projects already started and aim to) ?
Well just powered on the two ACA I have, put the bowie on, different flac file, thought god that's rubbish noticed one of the channels LEDs not on........OK felt the power bricks one was cold swapped over, LED off swapped power supply to another channel and the othe one went dead, great one of the Ebay Chinese power supplies has given up, swapped the power leads to confirm and it is dead.
But now I come to the OCD part should I buy another new same rated power supply and drop in or, as I feel compelled to do, buy two so I have matched power supplies, knowing its cheap crap and better to have them from the same supplier so they might be at least be a better match L/H to R/H? power supplies are rated 19V 4.74A 90W
For the sake of another 12 quid I will feel relaxed and enjoy the music!!, but my question is. Is there a better choice power supply wise (without DIY as I havent finished projects already started and aim to) ?
Last edited:
@mikegranger
Thanks a lot. This WE, I looked closer at Q1-4.
Continuity tests are OK. Pinout is good (j111 and 2kl170 are differents : DSG vs DGS ... with j111's DS interchangeable)
Q3 : resistor collector to emitter = 16k ohm
collector to base = 16k9 ohm
base to emitter = 1k ohm (= r8)
Q4 : gate to drain = 334k (=r 10+r9+drain to source)
gate to source = 333k (= r10+r9)
drain to sorce = 20 ohm (datasheet = 30 ohm max)
They look OK
.
So I asked for help to my brother (who were hardware developper) and he think there is a bug with the constant current source : Q2 or C2 seem guilty. It looks more and more strange and I'm completely lost
.
He should have a closer look at work and confirm that with his fellow workers. Then come back to give me instructions. I'll keep you informed of progress.
Next thing should be to buy new Q3 (ztx651) and Q4 (2sk170 on ebay) ....
Thanks a lot. This WE, I looked closer at Q1-4.
Continuity tests are OK. Pinout is good (j111 and 2kl170 are differents : DSG vs DGS ... with j111's DS interchangeable)
Q3 : resistor collector to emitter = 16k ohm
collector to base = 16k9 ohm
base to emitter = 1k ohm (= r8)
Q4 : gate to drain = 334k (=r 10+r9+drain to source)
gate to source = 333k (= r10+r9)
drain to sorce = 20 ohm (datasheet = 30 ohm max)
They look OK
. So I asked for help to my brother (who were hardware developper) and he think there is a bug with the constant current source : Q2 or C2 seem guilty. It looks more and more strange and I'm completely lost
.He should have a closer look at work and confirm that with his fellow workers. Then come back to give me instructions. I'll keep you informed of progress.
Next thing should be to buy new Q3 (ztx651) and Q4 (2sk170 on ebay) ....
You may want to buy these:
8 pieces of LSK170 ULTRA LOW NOISE SINGLE N-CHANNEL JFET - Parts
They are very good and known to be genuine. Not too sure about offerings on eBay.
8 pieces of LSK170 ULTRA LOW NOISE SINGLE N-CHANNEL JFET - Parts
They are very good and known to be genuine. Not too sure about offerings on eBay.
My improved ACA:
More imgs here.
An externally hosted image should be here but it was not working when we last tested it.
More imgs here.
Aibusine, I think your problem is in using the j111 . Using this device you end up with too much voltage across R9 which is applied to the gate of Q1 . It's not spelled out in the article but we would need something between 3 and 5 volts at the qate of Q1. 6.8v would result in the device being in saturation and be expected to just have a small voltage across it just like you are measuring.
@ acamilicko
Really nice, I love yours front and back plate : very professionnal !
@ woody
I got some news form my brother ... He think the main problem is Q4 which is used as a variable resistor here but looks to small according to R9.
First I have to send some signal in the board and look if I see it at the output.
Then decrease R9 value to 800ohm (5.8v) and 600 ohm (4.7v) and measure all voltages.
Test again if the signal is in.
Finally buy and put in the initial design's transistor : 2sk170 !
==> his words were : "Never change a component ! Design is made for this one and any different component have differents properties which requieres to adapt things around. Next time buy the original and save time
"
Really nice, I love yours front and back plate : very professionnal !
@ woody
I got some news form my brother ... He think the main problem is Q4 which is used as a variable resistor here but looks to small according to R9.
First I have to send some signal in the board and look if I see it at the output.
Then decrease R9 value to 800ohm (5.8v) and 600 ohm (4.7v) and measure all voltages.
Test again if the signal is in.
Finally buy and put in the initial design's transistor : 2sk170 !
==> his words were : "Never change a component ! Design is made for this one and any different component have differents properties which requieres to adapt things around. Next time buy the original and save time
"Some update
Some news :
I tested with VCC = +22V and R9 = 200 ohm (I don't try lower value here : not sure it's a good idea) : Q1 drain = 1.89v
VCC = +20V and R9 = 200 ohm : Q1 drain = 2.35v
That's better but not good at all
I plugged 8ohm speaker and it sang ! (ear at 10cm ....) : I'm delighted
Some news :
Yes there is.
No big change ....
I tested with VCC = +22V and R9 = 200 ohm (I don't try lower value here : not sure it's a good idea) : Q1 drain = 1.89v
VCC = +20V and R9 = 200 ohm : Q1 drain = 2.35v
That's better but not good at all
With my (cheap) multimeter : there were 0.20/0.25 VAC in for 0.4/0.45 out ... Huumm the signal is amplified
I plugged 8ohm speaker and it sang ! (ear at 10cm ....) : I'm delighted
I should receive some 2sk170bl for this WE.Finally buy and put in the initial design's transistor : 2sk170 !
While I'm trying to replace and organize internal wires in my F-5, I did something stupid and smoked mosfets. While waiting for new parts I connected ACA.
The thing is; I'm not sure about repairing F5 anymore. Don't get me wrong, but ACA monoblocks sounds way better than my F5 IMO. I'm using fairly sensitive speakers btw (~96dB) . Maybe I did some mistakes while building F5, or my speakers mate better with ACA. I really don't know...
In the meantime, I tried BA3-FE with ACA. Just incredible...
The thing is; I'm not sure about repairing F5 anymore. Don't get me wrong, but ACA monoblocks sounds way better than my F5 IMO. I'm using fairly sensitive speakers btw (~96dB) . Maybe I did some mistakes while building F5, or my speakers mate better with ACA. I really don't know...
In the meantime, I tried BA3-FE with ACA. Just incredible...
Turns might be less gradual. You might not be able to fine tune as easily.
Maybe someone has a better answer for you.
Amp camp fired up!
Hi, I finally got around to building my amp camp. Setting the bias was interesting, minute movements required when around 10v. I've tested it this evening using some speakers from an old Sony mini hi fi and Internet radio using my phone, just in case! It worked fine but what was interesting was the development of the sound stage. After being on for about 2 hours, and this is with the speakers placed on the floor, it was a surprise to hear it's width and depth. I'm looking forward to placing it in my system this weekend. Nice one Nelson!
Hi, I finally got around to building my amp camp. Setting the bias was interesting, minute movements required when around 10v. I've tested it this evening using some speakers from an old Sony mini hi fi and Internet radio using my phone, just in case! It worked fine but what was interesting was the development of the sound stage. After being on for about 2 hours, and this is with the speakers placed on the floor, it was a surprise to hear it's width and depth. I'm looking forward to placing it in my system this weekend. Nice one Nelson!
Higher PSU voltage?
A friend of mine asked me if he could build the ACA with a higher PSU voltage. He already has a 22 VAC torodial transformer, which he'd like to use for this. After rectification, the voltage would be around 28 VDC or so, quite a bit higher than the 19 VDC in the original design. What will happen with such a higher voltage? What happens to the biasing?
A friend of mine asked me if he could build the ACA with a higher PSU voltage. He already has a 22 VAC torodial transformer, which he'd like to use for this. After rectification, the voltage would be around 28 VDC or so, quite a bit higher than the 19 VDC in the original design. What will happen with such a higher voltage? What happens to the biasing?