G33/33 said:Hi Alex,
is there any alternatives for ZVP3306A ? I can't find it in Indonesia
can I use IRF 9610 / 9510 ?
ZVP3306A is available from Farnell. Possible alternatives are ZVP3310A, ZVP2110, ZVP4105, BSP254.
IRF9610/9510 are far too big for this position and would seriously impair performance and stability. I am considering now an "upside down" version of the amp, using PNP input and N-ch MOSFET instead of P-ch - as there is wider choice of suitable devices. Another possible P-ch alternative could be 2SJ76-79, I may try it in that position and see what happens.
Alex
Hi Alex and All,
for the power bjts I would like to suggest the a1943 and c5200 by Semelab , I have tried they I can say the Semelab works very fine more than the same bjts by other companies.
I have used they in a my amp. I have found they at Farnell.
For q9 I would like to suggest the bc327.
for q8 and q10 other changes don't improve the sound for their configurations.
change q9 I think it's important.
for q3, q4, q5,q6 other changes don't improve the sound for their configurations.
Pier Paolo Abbate.
for the power bjts I would like to suggest the a1943 and c5200 by Semelab , I have tried they I can say the Semelab works very fine more than the same bjts by other companies.
I have used they in a my amp. I have found they at Farnell.
For q9 I would like to suggest the bc327.
for q8 and q10 other changes don't improve the sound for their configurations.
change q9 I think it's important.
for q3, q4, q5,q6 other changes don't improve the sound for their configurations.
Pier Paolo Abbate.
Another update.
After playing in LTSpice with A3i circuit I found an alternative way to compensate it, resulting in a substantial increase of OLG at high frequencies and better THD figures. Here are the results after I've tried the simulated network on a real A3i:
THD+N measured by Amber 3501 in 300 kHz measuring BW for full 50W into 8 Ohm are 0.006% for 10 kHz and for 0.008% for 20 kHz - . At lower frequencies or levels distortion are on the limit of my measuring equipment. Attached picture shows the spectrum of 10 kHz 10V RMS into 8 Ohm - in 48kHz bandwidth THD is 0.0004% .
Alex
After playing in LTSpice with A3i circuit I found an alternative way to compensate it, resulting in a substantial increase of OLG at high frequencies and better THD figures. Here are the results after I've tried the simulated network on a real A3i:
THD+N measured by Amber 3501 in 300 kHz measuring BW for full 50W into 8 Ohm are 0.006% for 10 kHz and for 0.008% for 20 kHz - . At lower frequencies or levels distortion are on the limit of my measuring equipment. Attached picture shows the spectrum of 10 kHz 10V RMS into 8 Ohm - in 48kHz bandwidth THD is 0.0004% .
Alex
Attachments
Hello,
my A3i amp died two weeks ago and I found the fault Q8 transistor that I already replaced.
I thought it would be all fine, but after listening to some music for a few minutes, loud DC noise (again) in same channel speaker + relay protection (outputs cut).
Turning the amp off then on again, seems to work for a few minutes, no more.
The LED2 seems to be fine (lighted). Can it still be damaged? SHould I replace it anyway? It's almost sticked to the PCB, but not warm at all and visibly working.
When turning to faulty state, I can measure about -30 Volts on the collector of Q8 instead of 1.1 Volts (that I can measure on Q108, or when starting the amp, on Q8).
Any help greatly appreciated.
Cheers,
Gilles
my A3i amp died two weeks ago and I found the fault Q8 transistor that I already replaced.
I thought it would be all fine, but after listening to some music for a few minutes, loud DC noise (again) in same channel speaker + relay protection (outputs cut).
Turning the amp off then on again, seems to work for a few minutes, no more.
The LED2 seems to be fine (lighted). Can it still be damaged? SHould I replace it anyway? It's almost sticked to the PCB, but not warm at all and visibly working.
When turning to faulty state, I can measure about -30 Volts on the collector of Q8 instead of 1.1 Volts (that I can measure on Q108, or when starting the amp, on Q8).
Any help greatly appreciated.
Cheers,
Gilles
Hi Alex,
I replaced the LED2 today. I simply cut the old one on the PCB and soldered the new one directly on the remaining "legs", therefore at least 20 mm above the PCB. Also the Q8 trans was installed this way. Not nice, but replaced within 2 x 2 minutes!
Unfortunately, today, after listening to some music for 10 minutes (very mild volume), the amp relay switched off again.
Some clues:
Even after the relay switches off, the LED2 is lighted, and I can measure about minus 30 Volts on the Q8 trans collector.
I presume that another active component got damaged due to the initial Q8 death (in bypass). Do you have any idea?
Again, Alex, thanks very much for all your help.
Cheers,
Gilles
I replaced the LED2 today. I simply cut the old one on the PCB and soldered the new one directly on the remaining "legs", therefore at least 20 mm above the PCB. Also the Q8 trans was installed this way. Not nice, but replaced within 2 x 2 minutes!
Unfortunately, today, after listening to some music for 10 minutes (very mild volume), the amp relay switched off again.
Some clues:
Even after the relay switches off, the LED2 is lighted, and I can measure about minus 30 Volts on the Q8 trans collector.
I presume that another active component got damaged due to the initial Q8 death (in bypass). Do you have any idea?
Again, Alex, thanks very much for all your help.
Cheers,
Gilles
r7aake said:
Hi Giles,
that is not a good way of replacing devices! It is just possible that there is a dry joint on the PCB that you would see it if you remove the PCB from the case. It is really quite easy - you need to remove 6 screws from the speaker connectors at the back, 4 screws which hold the PCB supports from the bottom and 4 more that hold the heatsink brackets from the top. Disconnect a short link on the input and the whole power amp assembly can be lifted out and turned upside down for a proper inspection/repair.
Cheers
Alex
Hi Alex,
So far, it's all sorted out. I found out that after a few minutes of mid output power, the LED1 was shutting down.
I have unmounted the PCB as you advised, installed 4 bran new green LEDs, installed also correctly Q8.
For info, original LEDs in my amp were all yellow, not green.
Thanks again for all your help and for this nice amp design and sound.
Cheers,
Gilles
So far, it's all sorted out. I found out that after a few minutes of mid output power, the LED1 was shutting down.
I have unmounted the PCB as you advised, installed 4 bran new green LEDs, installed also correctly Q8.
For info, original LEDs in my amp were all yellow, not green.
Thanks again for all your help and for this nice amp design and sound.
Cheers,
Gilles
Power into 4 Ohms
Hey ho !
I have been using my repaired A3i now for a while, and it sounds realy great. (Thanks to x-pro for the fast help !)
Now I´m going to drive my main speakers with it, because I don´t have any other amp at the moment.
(Theese: http://www.visaton.com/en/bauvorschlaege/3_wege/concorde_mkiii/index.html )
How mutch power do you think can the amp provide into 4 Ohms and what is the weakest point then ? I don´t think it will be the output transistors if i provide a good cooling.
How mutch power is the transformer ratet ?
I also will replace the main caps to higher capacity ones.
Thanks in advance, have a nice weekend !
falk
Hey ho !
I have been using my repaired A3i now for a while, and it sounds realy great. (Thanks to x-pro for the fast help !)
Now I´m going to drive my main speakers with it, because I don´t have any other amp at the moment.
(Theese: http://www.visaton.com/en/bauvorschlaege/3_wege/concorde_mkiii/index.html )
How mutch power do you think can the amp provide into 4 Ohms and what is the weakest point then ? I don´t think it will be the output transistors if i provide a good cooling.
How mutch power is the transformer ratet ?
I also will replace the main caps to higher capacity ones.
Thanks in advance, have a nice weekend !
falk