A9
Hi,
here is the first impression of the A9. It sings
It runs with + -36VDC. The offset is between 4 and 5 mV after 20 seconds (comes from 300mV when turned on). The quiescent current is 15mA. With this setup, it can be set with the trimmer between 12 and 15mA.
The gain is high. The picture shows the input with 0.1Vpp and the output is 6Vpp at 1kHz! How can I adjust it?
The switching point of the FETs can be seen?
The sound is warm and has a crisp, punchy bass. The highs are crystal clear and without any background noise. With the old speakers as test equipment very impressive!
Some advice to optimize ist?
Layout can be changed. FETs should have more distance. It was tricky to mount it...
regards Olaf
Hi,
here is the first impression of the A9. It sings
It runs with + -36VDC. The offset is between 4 and 5 mV after 20 seconds (comes from 300mV when turned on). The quiescent current is 15mA. With this setup, it can be set with the trimmer between 12 and 15mA.
The gain is high. The picture shows the input with 0.1Vpp and the output is 6Vpp at 1kHz! How can I adjust it?
The switching point of the FETs can be seen?
The sound is warm and has a crisp, punchy bass. The highs are crystal clear and without any background noise. With the old speakers as test equipment very impressive!
Some advice to optimize ist?
Layout can be changed. FETs should have more distance. It was tricky to mount it...
regards Olaf
Attachments
olafk
Nice job !!
To decrease gain you must replace 22R resistor going to the signal GND, if you put 68R resistor the gain will be approx x30, if you put 47R the gail will be x42.
The bias at the driver stage is very low, the 5mA would be better IMHO (if you replace 3.9k resistor with 1.5k)
This is my next amp I am going to build but with bit different arangement, looks superb simple and nice.
Nice job !!
To decrease gain you must replace 22R resistor going to the signal GND, if you put 68R resistor the gain will be approx x30, if you put 47R the gail will be x42.
The bias at the driver stage is very low, the 5mA would be better IMHO (if you replace 3.9k resistor with 1.5k)
This is my next amp I am going to build but with bit different arangement, looks superb simple and nice.
Last edited:
Nice work, schematic with new (red) values for fast DC servo, high bias and low gain.
Regards
Attachments
A9 ready
I have installed all the changes since the last schematic by Mile. Perfect! The sound is just great. Please do not ask how to explain it
. The offset is zero. Sine wave looks perfect.
Great!
I have made a few changes to the layout. On the component side you can see last installed values.
regards Olaf
See also my apex-autumn gallery
Many thanks
I have installed all the changes since the last schematic by Mile. Perfect! The sound is just great. Please do not ask how to explain it
. The offset is zero. Sine wave looks perfect.Great!
I have made a few changes to the layout. On the component side you can see last installed values.
regards Olaf
See also my apex-autumn gallery
Many thanks
Attachments
Last edited:
I have installed all the changes since the last schematic by Mile. Perfect! The sound is just great. Please do not ask how to explain it
Great!
I have made a few changes to the layout. On the component side you can see last installed values.
regards Olaf
See also my apex-autumn gallery
Many thanks
Many Thanks for this pcb, A9 is my favorite amp,
Regards
I have installed all the changes since the last schematic by Mile. Perfect! The sound is just great. Please do not ask how to explain it
Great!
I have made a few changes to the layout. On the component side you can see last installed values.
regards Olaf
See also my apex-autumn gallery
Many thanks
great job olaf - as usual!
what will you cook for winter? I like to build amps
A9 is one on the top of the favorites list. Unfortunately, I can never really decide.
Thanks and regads
Olaf