after some tweaking...
It seems I can get the values into the ballpark?!
-3,7mV DCoffset (at speakeroutput) is good. But I ran out of wiper at the trimpots to bias higher.
I have to change some resistors... The adventure continues.
Cheers
Dirk
Enjoy every day in these crazy days... Listen to some good music!
It seems I can get the values into the ballpark?!
-3,7mV DCoffset (at speakeroutput) is good. But I ran out of wiper at the trimpots to bias higher.
I have to change some resistors... The adventure continues.
Cheers
Dirk
Enjoy every day in these crazy days... Listen to some good music!
Attachments
Hello out there,
i have biased the 'baby' to 400mV over the 0,15 Ohm resistors. So I am at around 2.67 A.
After 30 minutes I measure around 38° C at the outside of the heatsink (where the Mosfets are inside).
I am a cook...
Cheers
Dirk
i have biased the 'baby' to 400mV over the 0,15 Ohm resistors. So I am at around 2.67 A.
After 30 minutes I measure around 38° C at the outside of the heatsink (where the Mosfets are inside).
I am a cook...
Cheers
Dirk
Attachments
Hello ZenMod,
I think it is solved. I have made my own bias-boards. The circuit is very close to your Babelfish XA252-
OS-bias-circuit. I have used ZETEX NPN and PNP for the Wilson-current mirrors. I also had to adjust
some resistor values. I have to say - I copied from you! Offset is at the moment around 5 - 10mV after 30 minutes. At startup larger. Will see what the speakers will say at switching on? - Oooomph
Perhaps I need my first speaker-protection - boards?
Second channel is also biased up. Have to add input RCAs. Perhaps a little listening test this night -
or tomorrow.
As we all know - patience is our friend. Especially if we seem to see this
Cheers
Dirk
I think it is solved. I have made my own bias-boards. The circuit is very close to your Babelfish XA252-
OS-bias-circuit. I have used ZETEX NPN and PNP for the Wilson-current mirrors. I also had to adjust
some resistor values. I have to say - I copied from you! Offset is at the moment around 5 - 10mV after 30 minutes. At startup larger. Will see what the speakers will say at switching on? - Oooomph
Perhaps I need my first speaker-protection - boards?
Second channel is also biased up. Have to add input RCAs. Perhaps a little listening test this night -
or tomorrow.
As we all know - patience is our friend. Especially if we seem to see this
Cheers
Dirk
Hello ZenMod,
DCoffset at speakerout is at switch on around 150-200mV, but immediately goes down to around
40-50mV offset. After warm up (min. 30 min.) it is anywhere inbetween 5-20mV.
railvoltages are +-31.4 V DC unloaded and +-28.9 V DC loaded. Ripple voltage at the PSU was 0.4mV
unloaded and is now with 2.67 A of bias at around 18 - 20 mV AC.
Temperature at heatsinks is around 38° - 40° C.
No nasty blops. I am listening at the moment in the listening room...
ACP+ as preamp and those two 'big blocks' behind.
Cheers
Dirk
I forgot - some porn...
DCoffset at speakerout is at switch on around 150-200mV, but immediately goes down to around
40-50mV offset. After warm up (min. 30 min.) it is anywhere inbetween 5-20mV.
railvoltages are +-31.4 V DC unloaded and +-28.9 V DC loaded. Ripple voltage at the PSU was 0.4mV
unloaded and is now with 2.67 A of bias at around 18 - 20 mV AC.
Temperature at heatsinks is around 38° - 40° C.
No nasty blops. I am listening at the moment in the listening room...
ACP+ as preamp and those two 'big blocks' behind.
Cheers
Dirk
I forgot - some porn...
Attachments
Yeah, I think I'll make it out of wood. It shouldn't be too hard. Something more like a base with fence like slats to keep fingers out and let air flow than a real metal chassis.Hello audiosteve,
I think your ACA Mini deserves a 'nice little house'.
Although I have to be quiet - many of my projects are laying around naked or on wooden boards.
Greets
Dirk
Best amplifier till now in my setup! Sounds wonderful, with large and very high soundstage, beautiful tones and great detail. A special mention need the bass range: very "materico", three-dimensional, you have the desire to tap your feet... Like a very good analogue source, both with OB Lii15 and Pi4!