Thanks @danieljw I will update the build guide to show the improved connection point shortly. If anyone has solder the original point listedin the build guide, you may want to consider switching it.
Hi Guy's
Now that @danieljw has very thoroughly tested both feedback trace options.
I have updated the Build Guide to show the updated details for the feedback trace.
The current version is now "Wolverine Precision EF3 Build Guide revision 24 (08-09-22)"
Check your Dropbox project folder for the updated file.
Enjoy 🙂
Now that @danieljw has very thoroughly tested both feedback trace options.
I have updated the Build Guide to show the updated details for the feedback trace.
The current version is now "Wolverine Precision EF3 Build Guide revision 24 (08-09-22)"
Check your Dropbox project folder for the updated file.
Enjoy 🙂
If you did this you would need to tape the wire to the PCB. I don't think its wise to have a wire floating in mid air.
Part of the reason the second option may have preformed better is due the fact that it runs closer to the ground return trace sooner and exposes less loop area so radiated fields are not picked up as easily.
Hi,
When I was going through the BOM I found an extremely small error. Under the description for D107 and D108 it says "which has the same lumens as D8 & D9". I believe D8 and D9 are the BAV21 diodes.
When I was going through the BOM I found an extremely small error. Under the description for D107 and D108 it says "which has the same lumens as D8 & D9". I believe D8 and D9 are the BAV21 diodes.
I am testing EF3-3 with transistors and I have a question about the function of transistor Q104.
At a heatsink temperature of 20 degrees, I have 65mV on TP101/TP102 (power on). After 20 minutes I have 38mV on TP101/TP102 (heatsink temperature at the output transistor is 40 degrees).
Is it OK or is it possible to reduce the bias drop (adjust Rcc) ???
Q104 is mounted on the output transistor, Q104 has a gain of 80, Rcc is 91 ohms.
At a heatsink temperature of 20 degrees, I have 65mV on TP101/TP102 (power on). After 20 minutes I have 38mV on TP101/TP102 (heatsink temperature at the output transistor is 40 degrees).
Is it OK or is it possible to reduce the bias drop (adjust Rcc) ???
Q104 is mounted on the output transistor, Q104 has a gain of 80, Rcc is 91 ohms.
thimios:
Just to follow up, the speaker protection circuit has been reinstalled in the amp and is working perfectly. DC Offset is being adjusted today (currently 1.4 mV and 0.9 mV, with a target of reducing those numbers by two-thirds) and the amp will be delivered to my parents in 2 days.
All:
My Wolverine project has been subjected to about 150 hours of burn-in using a modified Hagerman FryBaby 3. I've been listening to this amplifier a lot over the past few days and am very pleased with it. You have to take builders' observations about their projects with a huge grain of salt -- I am, at least, unavoidably and positively biased towards the things I build. That said, this is a very good-sounding amplifier.
Kudos, once again, to the entire Wolverine Design Team!
Regards,
Scott
It's not uncommon for bias to start out different on power up until heatsink temp warms up from the idle bias. Changing Rcc won't make this any better. Rcc reduces variation in the bias from power supply fluctuations.
Try this...
Power up and wait for the bias stabilize completely. This may take up to 30min. While monitoring the bias start blowing a fan on the heatsink and watch how the bias responds. If it drifts a lot then there's a problem.
Jeremy
Hey guys,
I am building two sets of EF3-3 Boards and with one amp I am in the final steps of biasing. Regarding this amp I could use some advice. Both boards are biased approximately to 44mV and toggle around that value even after running for more than 30 minutes (+-2mV). DC offset is dancing around +-0.5mV. My first question is: are those values fine or should I try to get more exact biasing and offset?
Being curious I already tested the amp with some cheap speakers, and it was playing music! I am using a soft start board from the store and am experiencing a quite hefty thump when turning on the amp. Is that to be expected with an 800VA transformer running ~57V? The relay clicks after around 0.5 seconds. With a speaker protection board with a turn on delay this might be fixable and is planned for the near future.
Now to the issue I am most insecure about: When turning on the amp, the bias of both boards race to around 55mV and 65mV respectively. Both drop to ~44mV after 15 to 20 minutes. The “hotter” side does that in a faster manner. I did the test suggested by jjs in post #490 and the bias indeed does drop as soon as I point a fan on them. One board drops quite low to around 32 mV and the other one stabilizes at around 40mV after dropping to 35mV at first. I cannot estimate what would count as “too low” and therefore would like to know, what you guys think about that. Below I have compiled some data about both boards. Should I try to get some Q104s with a lower hfe and replace rcc accordingly or is said behavior acceptable?
Board A:
Startup bias: ~65mV, dropping pretty fast to ~44mV
Q104: ~170 hfe
RCC: 68.1 ohms
Board B:
Startup bias: ~55mV, dropping slower to ~44mV
Q104: ~170 hfe
RCC: 68.1 ohms
Best regards,
Michael
I am building two sets of EF3-3 Boards and with one amp I am in the final steps of biasing. Regarding this amp I could use some advice. Both boards are biased approximately to 44mV and toggle around that value even after running for more than 30 minutes (+-2mV). DC offset is dancing around +-0.5mV. My first question is: are those values fine or should I try to get more exact biasing and offset?
Being curious I already tested the amp with some cheap speakers, and it was playing music! I am using a soft start board from the store and am experiencing a quite hefty thump when turning on the amp. Is that to be expected with an 800VA transformer running ~57V? The relay clicks after around 0.5 seconds. With a speaker protection board with a turn on delay this might be fixable and is planned for the near future.
Now to the issue I am most insecure about: When turning on the amp, the bias of both boards race to around 55mV and 65mV respectively. Both drop to ~44mV after 15 to 20 minutes. The “hotter” side does that in a faster manner. I did the test suggested by jjs in post #490 and the bias indeed does drop as soon as I point a fan on them. One board drops quite low to around 32 mV and the other one stabilizes at around 40mV after dropping to 35mV at first. I cannot estimate what would count as “too low” and therefore would like to know, what you guys think about that. Below I have compiled some data about both boards. Should I try to get some Q104s with a lower hfe and replace rcc accordingly or is said behavior acceptable?
Board A:
Startup bias: ~65mV, dropping pretty fast to ~44mV
Q104: ~170 hfe
RCC: 68.1 ohms
Board B:
Startup bias: ~55mV, dropping slower to ~44mV
Q104: ~170 hfe
RCC: 68.1 ohms
Best regards,
Michael
I'm having Fireanimal or Daniel check the behavior of their amps so we can compare.
How do you have your Q104 mounted?
Jeremy
Q104 is mounted underneath the boards to the ums heatsink ("alternative" mounting as stated in 12. iv in the guide).
I get a bit of a thump when turning my amp on, its dual mono 300va per board with a soft start (around 0.5 second). I dont have any speaker protection at the moment. perhaps this is pretty normal without a relay on the output....
This behaviour is normal, in fact when cold my build starts at over 100mV and then drops down to the value that I set at burn in which was 44 mV
Since I am using a 5U heatsink for each channel (overkill at 200 mm x 400 mm x 40 mm)
The time taken to 44mV can vary depending on the ambient temperature of the room. But it is half an hour or less.
I have the vbe transistor mounted on an output device directly.
Hope this helps.
- Daniel
65mV=150mA of bias per output pair
44mV=100mA of bias per output pair
35mV=80mA of bias per output pair
Everything sounds normal except when you say the bias voltage drops when you put a fan on the heatsink.
Ideally the bias should not change with temperature but it is hard to get this level of accuracy. You don't want a positive slope meaning as the temperature goes up the bias goes up, this could lead to thermal run away. What you want is a slight negative slope so as temperature goes up the bias comes down, this helps keep the amp thermally stable. A aggressive negative slope is undesirable also because it could lead to under biasing when hot causing crossover distortion.
If you could try the fan test again that would be appreciated. Is the output loaded with 8ohms?
-Make sure the amp as been idle for 30min so the everything is thermally stabilized.
-Next turn on a fan only blowing on the heatsink fins and monitor the bias. The bias should go slightly up as the heatsink cools from the fan.
Jeremy
Thank you so much for the immediate help and the detailed answers! I will redo the fan test after letting both heatsinks warm up for at least 30 minutes. I will have to try it with a smaller fan to directly point the airflow to the heatsinks, since I did not assemble the case yet. Wanted to make sure everything works as intended prior to that. I have some old 4 ohms speakers attached to the output and unfortunately do not own any 8 ohms speakers.