Be careful. Did you check the DC voltage on the output?
diyAB Amp The "Honey Badger" build thread
- Thread starter Variac
- Start date
never connect your speakers if the output terminals are more than +- 100mV....
and please use a light bulb in series with the ac line until the amp is normal...
in my badger build i made an error which could let out the magic smoke, that light bulb was a life saver.....
Reading earlier post and it showed different trannie sec voltages against load. Why does higher sec voltages not support lower 4 ohm loads? Was thinking this amp was rated at 150w r8/ 250w r4.
you can of course use the same voltage for both 8 and 4 but with 4 ohms you are wasting more power heating the output trannies than if using lower voltage.
if you have plenty of output trannie pairs, and bigger heatsink, using the same secondary voltage is no problem....
engineering economics determine the least amount of resources to get the same results, but being diy'ers of course we can go crazy and do something else...
diy'ers are not limited by engineering economics....because we can....😀
The idea is if you're DESIGNING for a true 4 ohm load, you probably don't need the voltage swing that higher rails will provide. Lower rails improve the high current safe operating area of the output devices, leading to greater reliability. It's all about design tradeoffs.
i would even go as far as designing for 1 ohm loads, but that would be classified as crazy....😉😎
One other question and I know this has been discussed before from reading throughthe thread, but I just want to make sure I have it correct.
so from what I have read. If I am going to build this as a dual mono amp and I want to be drive a 4 ohm load, I need to have rails lower than the 65V or so a 45+45Vac transformer will give.
Would a 35+35Vac 300VA toroid for each channel be a good choice for a dual mono implementation driving 4 ohm loads?
Thanks
Debra
so from what I have read. If I am going to build this as a dual mono amp and I want to be drive a 4 ohm load, I need to have rails lower than the 65V or so a 45+45Vac transformer will give.
Would a 35+35Vac 300VA toroid for each channel be a good choice for a dual mono implementation driving 4 ohm loads?
Thanks
Debra
I've run car audio woofers with the badger. Even at the higher rails and WITH
the "iddy biddy" NJW's. BTW - just 2 pair !!! never blew them.
The trick is , just use normal musical content....
20hz will be about 40ms total , each set of 3 npn/3 pnp will see 20ms or less
full current.
At 4R , the amp would heat up (mine did !) ... here you have to factor in
the thermal de-rating of the soa.
About 15A (3 pair) at room temp (50ms soa at 60V) , derated 1/3 at 60c (10A+) ,
that is real hot (you should shut down at this point).
But that is a sustained (test)signal .. music (even techno), will not be a
full 2V sustained input signal.
Larger outputs would even have a larger safety margin at 4R.
OS
the "iddy biddy" NJW's. BTW - just 2 pair !!! never blew them.
The trick is , just use normal musical content....
20hz will be about 40ms total , each set of 3 npn/3 pnp will see 20ms or less
full current.
At 4R , the amp would heat up (mine did !) ... here you have to factor in
the thermal de-rating of the soa.
About 15A (3 pair) at room temp (50ms soa at 60V) , derated 1/3 at 60c (10A+) ,
that is real hot (you should shut down at this point).
But that is a sustained (test)signal .. music (even techno), will not be a
full 2V sustained input signal.
Larger outputs would even have a larger safety margin at 4R.
OS
Attachments
Just the clamp diode (optional) and easier screenprint/multipitch cap pads.
All else is the same.
OS
Most you could get with a 35-0-35V trafo is about 52V rails. At 100V p-p ,
12A for 20ms(below). The NJW (3 pair) soa is about 17-18A (60C -20ms).
With a large heatsink , normal music content ... the amp would not "strain"
at all.
Attachments
Very nice! Non -inductive OPS resistors , perfect inductor (nice Hi-gauge wire).
The VAS heatsink will be good for summer "party duty".
Many years of "hard service" ahead. 🙂
OS
What! What!
I have a 2kVA Xfmer that can be tapped for 30vac secondaries up to 110 vac secondaries. Designing for electrostatic or planar magnetic at 4-6 ohm. I have plenty of pairs of MJL 21193 and 4's. And industrial drive heatsinks, 24" X 10". 11 fins that are 2" deep on base of .35". One heatsink per channel. You can only use 3 Trannie Pair per channel with DIY boards correct? Does this sound like it would support 60 volt rails at R4?
I have a 2kVA Xfmer that can be tapped for 30vac secondaries up to 110 vac secondaries. Designing for electrostatic or planar magnetic at 4-6 ohm. I have plenty of pairs of MJL 21193 and 4's. And industrial drive heatsinks, 24" X 10". 11 fins that are 2" deep on base of .35". One heatsink per channel. You can only use 3 Trannie Pair per channel with DIY boards correct? Does this sound like it would support 60 volt rails at R4?
3 pair of 21193/4 would not "break a sweat" driving 4R at 60V.
VAS would preferably run a tad "hotter" with a 47-56R CCS resistor to drive
the larger OP's. Those heatsinks are overkill !
V2.4 PCB also has "fatter" rail tracks and plated through holes ... more current!
OS
Great this is the feedback I'm looking for! Do you think that the size of heatsink I'm using could support both channels. Or even parting in half would be enough for one for each channel? I'm correct in that the boards can handle only 3OP pairs? Is that the max anyone is using? What are some of the higher rail voltages being used right now?
The heatsink capacity is determined by:
your chosen quiescent dissipation (output bias current times PSU voltage) and
your worst case average listening Power and
your worst case ambient temperature.
If you give us information we can tell you the first one.
No one on this Forum can tell you the second two.
your chosen quiescent dissipation (output bias current times PSU voltage) and
your worst case average listening Power and
your worst case ambient temperature.
If you give us information we can tell you the first one.
No one on this Forum can tell you the second two.
Ok understand what you are saying but then how does he know that they are overkill as above post? Really just looking for a ballpark educated guess based on past experience from other amps. Worst case ambient would be 85F. Speakers are 6ohm and 89 db sensitivity. Play music at loudest 95-100 db