Hi Niko
I would be surprised that the j112 are faked because real ones are very cheap price (0.62$) anyway.
Fab
I would be surprised that the j112 are faked because real ones are very cheap price (0.62$) anyway.
Fab
Those of you that are awaiting boards or have boards remember that not only is the design very, very good, Fab has written a manual second to none.
If you follow his very thorough manual you will extract every bit of performance out of the design. It is the details that count, and he tells you exactly how to handle those details.
If you follow his very thorough manual you will extract every bit of performance out of the design. It is the details that count, and he tells you exactly how to handle those details.
@Fab,
I am trying to push a little further on the bias, since i m running a bit low on the rail voltage, +/- 23.2 Vdc.
How high can i bias ?
Is it safe to bias till the heatsinks stay constant at 55-60 DegC ?
Thanks
I am trying to push a little further on the bias, since i m running a bit low on the rail voltage, +/- 23.2 Vdc.
How high can i bias ?
Is it safe to bias till the heatsinks stay constant at 55-60 DegC ?
Thanks
Hi meanie
55C is no problem. More than that it may be too hot for the skin when touching the heatsink...
With about 1.1A you are already in full class A at max power with 8 ohms speakers.
Only for 4 ohms speakers you benefit for more bias to stay in class A at higher power. Also at the same time, more bias means more open loop gain and slightly higher damping factor for this topology.
Fab
55C is no problem. More than that it may be too hot for the skin when touching the heatsink...
With about 1.1A you are already in full class A at max power with 8 ohms speakers.
Only for 4 ohms speakers you benefit for more bias to stay in class A at higher power. Also at the same time, more bias means more open loop gain and slightly higher damping factor for this topology.
Fab
Thanks, Fab!
Something happened when I was trying to increase bias, my meter show the reading jumping back and forth between 65mA and 58mA.
Then I realized I had a bad quality pot (P1,P2), so I had to strip the amp again and replace the pots.
Pls use quality brands like Bourne, you will get fewer issues in the long run.
Something happened when I was trying to increase bias, my meter show the reading jumping back and forth between 65mA and 58mA.
Then I realized I had a bad quality pot (P1,P2), so I had to strip the amp again and replace the pots.
Pls use quality brands like Bourne, you will get fewer issues in the long run.
meanie,
Good that you identified the issue quickly. Hope you can get your amp up and running soon.
Good that you identified the issue quickly. Hope you can get your amp up and running soon.
Do you simultaneously act on P1 and P2 for the bias while keeping the output offset (0V) as low as possible?
The must be done with two multimeters because if for example you act on P1, it is normal that the value of the bias changes to P2.
Thanks for your advice
Yes, I did.
I use 3 meters, monitoring the output while adjusting both P1 and P2 simultaneously. Yet the figure jumps over the place.
The other channel responded to the adjustments well.
Hi Meanie
i have the same issue.... cold welding bad join on trimmer Vishay ...solved..
T93YA102KT20 Vishay / Sfernice | Mouser Greece
my measurements were slowly coming to me...
Last edited:
I will recheck while changing the pots.
It was working fine @1.3A till this attempt to increase bias...
On re-reading the above quote I found a couple of measurement typos! I have corrected them in red in the quote above. As it was well outside the 30min editing opportunity I think that this is the best way to correct the post and also to get some response.
Many thanks 🙂
Attachments
Last edited:
brianco,
Looks like you have enough heat sink there. The area you have with 228mm x 250mm heat sink is larger than the 300mm x 165mm heat sink of the 4U Deluxe chassis available at the diyA store.
The fins also have nice little corrugations, helping increase the fin surface area and heat dissipation.
Last edited:
Nice DIY badge Vunce. By the time you've completed the chassis work, you will have a unique looking amp 🙂
