Hi all,
I'm starting to build the Honey Badger Amp in dual mono configuration and I need to choose the transformers.
My speakers are 4 ohm. I know that it is recommended to have a lower power supply voltage than the one used for 8 ohm speakers.
Let's say I put two 400 VA transformers (one per channel), what is the suggested secondary output voltage? 2 x 40V or even less?
With 400 VA 2x40 V the maximum current could be 5 A every secondary. This would be fine to guarantee 300W on the 4 ohm load?
Thanks!
I'm starting to build the Honey Badger Amp in dual mono configuration and I need to choose the transformers.
My speakers are 4 ohm. I know that it is recommended to have a lower power supply voltage than the one used for 8 ohm speakers.
Let's say I put two 400 VA transformers (one per channel), what is the suggested secondary output voltage? 2 x 40V or even less?
With 400 VA 2x40 V the maximum current could be 5 A every secondary. This would be fine to guarantee 300W on the 4 ohm load?
Thanks!
You won't be able to get to 300W continuous on 4ohms without at least going to 2x42Vac. 400VA per channel will just barely get you there or just a little shy. I'd bump that up to 500VA per channel to guarantee 300W on 4ohms. I'm not sure what outputs you are using so keep in mind SOA.
Jeremy
You might be confusing AC vs DC requirements. 49 VDC at the output would be 600.25 watts peak or 300 watts continuous. Emitter resistors of 0.33 ohms will use 4.04 volts at peak, though this would be divided by the number of parallel output devices. Add another 5 volts for overhead and the DC rail requirement will be 58 volts. Peak current will be 12.25 amps and this will load the supply voltage. 60 volt rails would be the minimum. The transformer would have to be at least 44-0-44 volts AC and be able to sustain that. The other major concern is filter capacitor ripple current. At 12.25 amps peak, ripple current will be 30-40 amps.
It does help that a 10 dB peak to average ratio would bring it down to 30 watts long term continuous. That consideration will reduce transformer and heat sink requirements but the peak values will still be needed when 300 watts is called for.
It does help that a 10 dB peak to average ratio would bring it down to 30 watts long term continuous. That consideration will reduce transformer and heat sink requirements but the peak values will still be needed when 300 watts is called for.
The Honey Badger uses .22ohm emitter resistors
Sqrt(300W*4ohms)*Sqrt(2)=49V peak
49V/4ohms=12.25A
12.25A*.22ohms/3=.89V (divide by 3 since there is 3pairs)
1V(output vbe)+1V(driver vbe)+1V(vas)+.89V=3.89V, round to 4V
49V+4V=53V (rails needed under load)
53V*110%+1.4V(bridge loss)=~60V unloaded (110% for stiff supply) or 2x42Vac
53V*115%+1.4V(bridge loss)=~62V unloaded (115% for a normal supply) or 2x44Vac
Using the simple equation for DC Power
2/pi*53V^2/4ohms=447W
So I definitely recommend 500VA per channel.
You can get by with a lower Vac rating if the transformer is oversized as the power supply will sag less. 500VA for the 2x42Vac and 400VA for the 2x44Vac per channel.
Jeremy
Thank you for your answers!
So lets say I'd settle for 250 W into 4 ohms,
the power peak would be 500W. Voltage and current peaks would be 44.7 V and 11.18 A
Following your formulas the required voltage rail under load would be 49 V
Adding a 115% overhead plus the bridge loss you will have almost 58V . This mean 2x42Vac
The DC power would be 382W, so 400VA per channel.
These numbers would be fine with MJL4281A / MJL4302A as power devices?
Thanks!
So lets say I'd settle for 250 W into 4 ohms,
the power peak would be 500W. Voltage and current peaks would be 44.7 V and 11.18 A
Following your formulas the required voltage rail under load would be 49 V
Adding a 115% overhead plus the bridge loss you will have almost 58V . This mean 2x42Vac
The DC power would be 382W, so 400VA per channel.
These numbers would be fine with MJL4281A / MJL4302A as power devices?
Thanks!
MJL4281A/MJL4302A are more than adequate. You could run those at +/-64V at 4ohms no problems but leaving the rails at +/-58V to +/-60V you'll have very robust output stage.
Jeremy
Very inspirational! Have been contemplating a 4 ch build for a pair of lx mini's.Hope you enjoy and get som inspiration
Thanks AudioSan 👌
Glad to help. a four ch yoy say. bass and mid? or mid and tweeter. anyway. i would take a close looke at what ypu dont see. the bottom is cut out for each ch, and the top is only cut out for i bit of that. that creaties a natrual forced convection. more air is fprced /pusced in to the chassis then the air that leaves the chassis. you get å turbulent air between the channels. hat actually takes care of most of the heat.
Their SOAR even looks a bit better than the MJL4281A/MJL4302A's, and they're also listed in the BOM (afaik). So, why not? Anyway, their fT is much lower (4 MHz vs. 35 MHz). Maybe someone who is more knowledgeable than me may know about the impact?
Best regards!
Hello, Did you pair the transistors when building? I am mainly talking about the KSC3503 transistors which are only available in version D and the ksa1381 which are only available in version E.The ksc3503 D that I have have an hfe of 84 to 89 and the ksa1381 E have an hfe of 118 to 127. Do you think that will work? Impossible to find ksc3503 in version E. Cordially
awfully hard to match npn's and pnp's the better thing to do is to select the higher Hfe's for either types