Juntuin,
I knew you couldn’t resist the Alpha BB
!!I’ll be looking forward to seeing all the unique BB creations.
Good luck with your build.
Cheers,
Vunce
Hi X,
Yes, the transformers are going to be the key for stereo BB enjoyment.
Would feeding the BB 38vdc be ok? Since I have a 600va 32vac Antek already, I’d only need to purchase one more. Although, I don’t think the 600va will sag as much as the 300va I powered up the BB with. In that case I’d be in the 40vdc range and would have to buy a pair of transformers.
Yes, the transformers are going to be the key for stereo BB enjoyment.
Would feeding the BB 38vdc be ok? Since I have a 600va 32vac Antek already, I’d only need to purchase one more. Although, I don’t think the 600va will sag as much as the 300va I powered up the BB with. In that case I’d be in the 40vdc range and would have to buy a pair of transformers.
Hi X,
I have some encouraging news about the 600va 32vac transformer
Without load the psu output was 43vdc, with the BB connected it’s 38vdc. It does run hotter, of course, but the fans kicked up a bit to exhaust the extra heat(still barely audible). With 29.5vdc the aluminum mosfet clamp was 42°C, now powered with 38vdc the clamp is 50°C. Bias voltage is very steady .612v-.618v. But, dc offset increased from 2mV to 22mV?
One observation, with either transformer I tried, that I’m not comfortable with is the extreme woofer excursion at power up. It’s slow, but looks like the cone is stretched to the max!
So, this made my transformer purchase much better for my wallet, I only need one more
I have some encouraging news about the 600va 32vac transformer
Without load the psu output was 43vdc, with the BB connected it’s 38vdc. It does run hotter, of course, but the fans kicked up a bit to exhaust the extra heat(still barely audible). With 29.5vdc the aluminum mosfet clamp was 42°C, now powered with 38vdc the clamp is 50°C. Bias voltage is very steady .612v-.618v. But, dc offset increased from 2mV to 22mV?
One observation, with either transformer I tried, that I’m not comfortable with is the extreme woofer excursion at power up. It’s slow, but looks like the cone is stretched to the max
!So, this made my transformer purchase much better for my wallet, I only need one more
Good news on the trafo. Thanks for testing it. I wonder if we switched to a smaller C104 cap on the LTP smoothing cap, say 100uF vs 1000uF would the movement be less? 22mV is still excellent - nothing to your speakers. Main thing is that it is stable and doesn't change with temp.
That Antek 6432 is a beast! 12lbs ea!
That Antek 6432 is a beast! 12lbs ea!
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It is considerably larger than the 400va trafo used in my ALPHA20.
I will utilize the 12vac winding to feed a 12vdc power supply for the PWM fan controller. Then, I don’t have to use a separate wallwart supply.
Hello Hugh,
In post #2080, you provided 4 simulations for different compensation techniques. Correct me if I am wrong or have misunderstood but I think all of them are pretty similar is the conclusion? Except may be the fourth compensation technique?
I plan to go with default one for Alpha 20 (18p + 18p). Let me know if this will work fine.
Thanks
In post #2080, you provided 4 simulations for different compensation techniques. Correct me if I am wrong or have misunderstood but I think all of them are pretty similar is the conclusion? Except may be the fourth compensation technique?
I plan to go with default one for Alpha 20 (18p + 18p). Let me know if this will work fine.
Thanks
I successfully powered up my second ALPHA BB board. I installed a 220uF capacitor in C104 to check if that reduced the woofer cone excursion at power up.
Result: the cone moves the same distance out/in as with the 1000uF cap. But, now it moves much faster and creates a pop sound. So it’s worse with the smaller capacitor. I’ll put in the same 1000uF cap that’s installed in the first BB board to eliminate the POP sound.
Any thoughts how to reduce/eliminate the extreme cone movement altogether?
My previous 60w class-A (Aleph 5) did that also and couldn't get rid of it, I had to install dc-prot/delay circuit..
Hi Vunce,
Congrats on getting B.B. #2 fired up successfully. Probably easiest thing is a 5sec turn on delay relay system, also handles DC protect. Something like this:
Upc1237 Dual Channel Speaker Protection Circuit Board Boot Mute Delay DC 12-24v | eBay
You will have to modify it (change resistor or cap on RC time constant) to get a longer time delay. Or if using relay, use smaller cap to let it reach voltage sooner.
Congrats on getting B.B. #2 fired up successfully. Probably easiest thing is a 5sec turn on delay relay system, also handles DC protect. Something like this:
Upc1237 Dual Channel Speaker Protection Circuit Board Boot Mute Delay DC 12-24v | eBay
You will have to modify it (change resistor or cap on RC time constant) to get a longer time delay. Or if using relay, use smaller cap to let it reach voltage sooner.
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Guys,
Thanks for the feedback
I was resisting that option (dc protect/delay) but, I’d rather be safe than have an issue with my speakers. Besides, I already have four of those protect/relay boards sitting in the parts bin looking for a home.
Cheers,
Vunce
I think theres no more than relay in audio path so should not affect the sound! Major problem is how to power that circuit
I ended up wounding another secondaries on both toroids, my dc-prot/delay circuits work with AC.
