Newest Badger Builder
Hey Badger Fans,
I'm gearing up to build 2 channels of Honey Badger for home system. I already have a pile of parts I was going use for a Mongrel build that never happened.
First off, my listening room is small, my speakers are small, and I really dislike loud music. My current system is 40 WPC, and I keep the volume around 2 out of 10, or lower. So yeah, I'm an old fart.
That said, I already have a pair of Antek 100 VA toroids, 30-0-30, which nominally gives 42 volt rails. My question is : Will I be okay with just 2 output pairs instead of 3 ? I'm using NJW0281G and NJW0302G. Lazy math sez that if 3 pairs are good for 150 WPC, then two pairs in my system are probably overkill. But I want to make sure I'm not overlooking something .........
Also, I already have lots of 2200 uF/105C caps rated at 50V. Is that safe enough for 42 V rails ?
Finally, for the DC offset adjust pot, R17, I have a pile of 10k 10-turn pots. Will these work in place of the 1k pots ? (FWIW, I have 100 each of Q1/2 and Q3/4, so I plan to do some beta matching.)
TIA, I'm sure I'll have more questions in the near future ...
Hey Badger Fans,
I'm gearing up to build 2 channels of Honey Badger for home system. I already have a pile of parts I was going use for a Mongrel build that never happened.
First off, my listening room is small, my speakers are small, and I really dislike loud music. My current system is 40 WPC, and I keep the volume around 2 out of 10, or lower. So yeah, I'm an old fart.
That said, I already have a pair of Antek 100 VA toroids, 30-0-30, which nominally gives 42 volt rails. My question is : Will I be okay with just 2 output pairs instead of 3 ? I'm using NJW0281G and NJW0302G. Lazy math sez that if 3 pairs are good for 150 WPC, then two pairs in my system are probably overkill. But I want to make sure I'm not overlooking something .........
Also, I already have lots of 2200 uF/105C caps rated at 50V. Is that safe enough for 42 V rails ?
Finally, for the DC offset adjust pot, R17, I have a pile of 10k 10-turn pots. Will these work in place of the 1k pots ? (FWIW, I have 100 each of Q1/2 and Q3/4, so I plan to do some beta matching.)
TIA, I'm sure I'll have more questions in the near future ...
R27 is 68 Ohms, measures 67.9
R28 comes in at 2.19K ohms
R29 comes in at 668 Ohms
R30 comes in at 479 Ohms. It doesn't quite make it to the full 500.
I'm going to check over my semis again. I must be missing something very stupid and obvious that I am taking for granted.
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I'd change R27 to 82R. Much more bias range.
Center of the bias trimmer will give 55ma per device with the 82R -
VAS runs at 7.8ma .... much cooler and sufficient for a EF2 output stage.
PS -(small copper plate or roof flashing as VAS heatsink).
OS
30-0-30Vac will allow a maximum power of around 80W into 8r0.
For a very reliable build, use 400W of output devices.
2pair of >=100W devices meets that requirement.
You don't need 3pair for 8ohms speakers.
But if you have 4ohms speakers, where 30-0-30Vac will allow a maximum output power of around 150W, then you would need 3pair of >=125W devices.
It should be OK, but you need to take a few measurements to ensure it is OK for worst case conditions.
Measure the mains input voltage and the secondary output voltage without any load.
Use that to determine the maximum output voltage when mains supply is up at the maximum tolerance your supply company claims it will never exceed.
Then you can calculate the maximum voltage on your smoothing capacitors.
BTW,
I recommend +-20mF/ch for 8ohms speakers and good extended bass response.
That will require 9off 2200uF on each power rail and that equals 36 capacitors for a 8+8ohms amplifier.
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When I was taught long ago, learning about Farad as a unit, it was explained as a large unit and usually depicted in pF , nF and μF.
mF (milli) was never stated as a usual prefix for Farad.
Even when looking at the markings on Capacitors, the largest prefix I usually see is (micro) μF. for example 10000μF and not 10mF.
But I guess that this is not a law, and with larger and larger values of capacitor milli Farad will become more and more used.
I remember been told that Farad is such a large unit that a 1 Farad capacitor would be the size of a large chair. Those days are gone.
Regards
Judging by the non-response, it is a dumb question or self-apparent to you guys. I guess I will get some np caps and go that route. Trying to do the amp with Elna Silmic throughout. I'm basically to that terrifying moment where I actually plug it in.
I have the light bulb and a variac, have not put in the output trannies, installed the temporary bypass resistors and the sacrificial resistors, etc. etc.
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Judging by the non-response, it is a dumb question or self-apparent to you guys. I guess I will get some np caps and go that route. Trying to do the amp with Elna Silmic throughout. I'm basically to that terrifying moment where I actually plug it in.
If you are doing it that way , good for you
.I just did another like that .... If you just plug it in for a split second , the
driver plus the input stage current draw should keep it working for
several minutes off of just the capacitor banks.
If it shuts down quickly , the IPS/VAS/drivers are drawing far more than
the typical 15-20ma per rail .
PS - then set for 1.1V between driver emitters -
Touch or hold a heat source to the MJE Vbe , you should see the 1.1V drop.
..... any later installed outputs should be
right below conduction - no magic smoke.
OS
Cool, thanks. Never built a BJT A-B amp. It's been a lot of fun so far!
To clarify what i meant ... solder two temporary 1K resistors from Q14 and 15
emitters to the output rail.
This will actually run the amp with the drivers completing
the feedback loop (with no outputs installed).
Once you have the low current section set , populate with DMM tested output
devices.
OS
100W into 4r0 requires an output of 28.3Vpk.
Allowing for a voltage drop through the amplifier of around 3V, you would need ~+-31Vdc at the supply rails when the amplifier is delivering full power.
The supply rails will sag from Quiescent to full power by an amount that depends on how you build your PSU. Expect at least 2V of voltage sag, but expect much more if you don't build in sufficient current capability.
Assuming 3V of sag and 3V of amp loss, you will need quiescent supply rails of around +-34.3Vdc.
You should be able to get that from a 25-0-25Vac transformer.
Test into a 2r0 dummy load to see how bad your PSU is and how badly your amplifier is at passing typical speaker currents.
If you want a more severe test (but still less stress than driving a 4ohms severe reactance speaker) use a 1r3 dummy load. This gives a real test of how much current your amplifier can supply to a speaker, but without the stresses of driving L and/or C.
Allowing for a voltage drop through the amplifier of around 3V, you would need ~+-31Vdc at the supply rails when the amplifier is delivering full power.
The supply rails will sag from Quiescent to full power by an amount that depends on how you build your PSU. Expect at least 2V of voltage sag, but expect much more if you don't build in sufficient current capability.
Assuming 3V of sag and 3V of amp loss, you will need quiescent supply rails of around +-34.3Vdc.
You should be able to get that from a 25-0-25Vac transformer.
Test into a 2r0 dummy load to see how bad your PSU is and how badly your amplifier is at passing typical speaker currents.
If you want a more severe test (but still less stress than driving a 4ohms severe reactance speaker) use a 1r3 dummy load. This gives a real test of how much current your amplifier can supply to a speaker, but without the stresses of driving L and/or C.
If you have not bought the caps yet , get 80-100V ones.
The Badgers real strength is it's ability to produce those big transients , which
equates to a more realistic sound stage.
In the future , either through e-waste or tax return .... a 40-50V trafo will
come your way.
OS
So I ordered new parts, everything in the VBE/Driver/Output sections. Until the parts arrive, I will be painstakingly looking over everything.
I will definitely be using the methods you (building up to the drivers w/resistors) and Andrew T (the bulb limiter) prescribed.
I'm new at this (since high school - 13 years ago - my only major electronics project was restoring an old pair of Dynaco Mark III mono-blocks). I seem to have greatly underestimated how easy it is (for me) to screw up.
Happy Honey Badger
I completed this amp a year ago and its not missed a beat since, very reliable. Sound quality far surpasses my previous NAD product and runs a
lot cooler, I don't listen at high volumes.
I did splash out on a Schiit Ascard headphone amp which doubles as a front end pre, very happy. Altogether probably into the amp and pre combo at around $750 Canadian. Very happy with the performance value,
and the satisfaction of assembling myself.
For anyone contemplating building one of these, give it a shot, you will not regret it. Take your time, and let the forum help if required, I did and am
still grateful for the advice during the build.
Again thanks to the forum members that enabled me to acheive this.
I completed this amp a year ago and its not missed a beat since, very reliable. Sound quality far surpasses my previous NAD product and runs a
lot cooler, I don't listen at high volumes.
I did splash out on a Schiit Ascard headphone amp which doubles as a front end pre, very happy. Altogether probably into the amp and pre combo at around $750 Canadian. Very happy with the performance value,
and the satisfaction of assembling myself.
For anyone contemplating building one of these, give it a shot, you will not regret it. Take your time, and let the forum help if required, I did and am
still grateful for the advice during the build.
Again thanks to the forum members that enabled me to acheive this.
VERY nice amp , Pthep !
I'd be building a Badger , but I have so many slewmasters to use .
Wolverine (reverse Badger) was the first VFA amp I designed for the
slewmaster.
I WOULD NOT of bothered ... if this (the Badger) was not
a top quality design.
My Wolverine is the "tester" input stage (modular design) - absolute stability !!
Listening impressions ??
OS
I'd be building a Badger , but I have so many slewmasters to use
.Wolverine (reverse Badger) was the first VFA amp I designed for the
slewmaster.
I WOULD NOT of bothered ... if this (the Badger) was not
a top quality design.
My Wolverine is the "tester" input stage (modular design) - absolute stability !!
Listening impressions ??
OS
OS While not pretending to be any kind of "audiophile", my hearing
is keen enough to appreciate good and improved reproduction.
I can only compare to components I have previously owned, which
were in the low to mid range of commercial offerings.
To put one word to decribe this amp it would be dynamic.
That coupled with an extension in both the lower and upper
frequencies it actually sounds like the drums are in front of me.
Of course it is restricted by its surrounding components. My source
is flac files through a networked player with dac, the speakers are
MA Rx6, and they have never sounded better.
All in all I rate it as a very worthwhile project resulting in a nice
upgrade to my system.
Incidently, I built mine exactly as per the bom and manual, no mods.
*** "And it Worked"****
Cheers P.
is keen enough to appreciate good and improved reproduction.
I can only compare to components I have previously owned, which
were in the low to mid range of commercial offerings.
To put one word to decribe this amp it would be dynamic.
That coupled with an extension in both the lower and upper
frequencies it actually sounds like the drums are in front of me.
Of course it is restricted by its surrounding components. My source
is flac files through a networked player with dac, the speakers are
MA Rx6, and they have never sounded better.
All in all I rate it as a very worthwhile project resulting in a nice
upgrade to my system.
Incidently, I built mine exactly as per the bom and manual, no mods.
*** "And it Worked"****
Cheers P.
I completed this amp a year ago and its not missed a beat since, very reliable. Sound quality far surpasses my previous NAD product and runs a
lot cooler, I don't listen at high volumes.
I did splash out on a Schiit Ascard headphone amp which doubles as a front end pre, very happy. Altogether probably into the amp and pre combo at around $750 Canadian. Very happy with the performance value,
and the satisfaction of assembling myself.
For anyone contemplating building one of these, give it a shot, you will not regret it. Take your time, and let the forum help if required, I did and am
still grateful for the advice during the build.
Again thanks to the forum members that enabled me to acheive this.
Very, very nice work. I'm in the process of building the HB also. Although lately it seems other life priorities have intervened.
Rick
BTW, what enclosure did you use? Looks like it's just about the right size for the amp.I completed this amp a year ago and its not missed a beat since, very reliable. Sound quality far surpasses my previous NAD product and runs a
lot cooler, I don't listen at high volumes.
I did splash out on a Schiit Ascard headphone amp which doubles as a front end pre, very happy. Altogether probably into the amp and pre combo at around $750 Canadian. Very happy with the performance value,
and the satisfaction of assembling myself.
For anyone contemplating building one of these, give it a shot, you will not regret it. Take your time, and let the forum help if required, I did and am
still grateful for the advice during the build.
Again thanks to the forum members that enabled me to acheive this.