Re: Will the badger operate with 40 volt rails ...?
Yes
The only concern of lowering the voltage from +/- 60V to +/- 40V is biasing the BJT. With lower bias, BJT (transistor) may not be operated at the point as the original designer intended.
Since the differential pair and VAS stage has current source, as long as the current source is maintained, you should be fine.
Yes
The only concern of lowering the voltage from +/- 60V to +/- 40V is biasing the BJT. With lower bias, BJT (transistor) may not be operated at the point as the original designer intended.
Since the differential pair and VAS stage has current source, as long as the current source is maintained, you should be fine.
Hi All,
I did a bulb test on HoneyBadger on 1 channel. Without initial R30 set near to 500ohms, The light bulb is off. But when tune the TP1 to TP2 to ~35mV, The bulb started to light up. Just would like to know whether this is normal or not. Anything needs to check??
Cheers,
James
I did a bulb test on HoneyBadger on 1 channel. Without initial R30 set near to 500ohms, The light bulb is off. But when tune the TP1 to TP2 to ~35mV, The bulb started to light up. Just would like to know whether this is normal or not. Anything needs to check??
An externally hosted image should be here but it was not working when we last tested it.
Cheers
,James
James, to be a bit pedantic maybe this needs to be in the "build" thread. The bulb test is meant for first switch on where we can see that nothing is overheating, fuse blowing or worse. Not certain if you are adjusting output DC offset or bias current. If the latter the amplifier will draw more power from the mains as Iq is raised and the bulb will glow more brightly. Is this a gradual increase with adjustment or does it suddenly take more power when a threshold is reached?
If the former you can dispense with the bulb and run on full voltage. If the latter you may be having instability problems. Without an oscilloscope one indication of instability could be overheating of the output Zobel resistor. Good luck with your project.
Keith
If the former you can dispense with the bulb and run on full voltage. If the latter you may be having instability problems. Without an oscilloscope one indication of instability could be overheating of the output Zobel resistor. Good luck with your project.
Keith
Keith, thanks for your advice! When I adjusted DC offset and CCS, the bulb still remained no light. Once I adjusted bias current to 10mV and above, the light started to glow gradually as increasing the voltage across 2X 0R22 Re. Currently I put it at 30mV and the brightness of light remains the same for an hour. Is this considered as formal case? I will try to dispense the bulb and try it tomorrow night again.
Cheers,
James
Cheers
,James
Keith, I just removed the bulb. Now my speaker is singing with dc bias set to 40mV on 1 ch. The sound is warm and rich.
Just share the experience what I have. It is not advisible to tune bias current in bulb test as it is really not accurate. I did it with 35mV with bulb. However, when I removed the bulb and connect directly, it shoot up more than that and continue increasing. Luckily I offed it immediately and tuned to Rmax again, removed bulb, turn on, and adjust to 20mV. Then, adjust it every 1/2 hrs. Now it is set to 40mV.
Cheers,
James
Just share the experience what I have. It is not advisible to tune bias current in bulb test as it is really not accurate. I did it with 35mV with bulb. However, when I removed the bulb and connect directly, it shoot up more than that and continue increasing. Luckily I offed it immediately and tuned to Rmax again, removed bulb, turn on, and adjust to 20mV. Then, adjust it every 1/2 hrs. Now it is set to 40mV.
Cheers,
James
Yes, that is what is advised in many previous replies.
But, too many refuse to read !
Burned out Power transistor
Hello,
I am having issues of burned out power transistor.
After adjusting the offset to near 0V (+/-5mv) and bias to 15mv (between TP1 and TP2, and wait for few minutes), I started the music listening on one channel.
Everything is fine for few minutes, the heat sink is not hot, output is no more than 3V RMS.
Suddently, the transformer fuse (4A) at 120V side blown and sound stop.
After debug, found out that only Q17's and Q19's Collector and Emitter shorted, thus cause fuse blow. Other 4 power transistors are fine.
Since the heat sink is not hot at all and only one bias controls 6 power transistor, I have to assume the bias setting is as good as it can be.
I am guessing that the three transistors in parallel may fight with each other.
Transistor with higher hfe may try to charge transistors with lower hfe ??
To allow hfe difference among transistors, my understanding is to use R37 - R42 to minimize the hfe difference.
While looking at other similar design with parallel transistor, they were using 100-470 ohms as the base resistor.
If my understanding is correct, my question is how is the value of 2.2 ohms be determined ? Is it too small ? Or it requires very tight hfe matching ?
I do not believe matching hfe can be done just by using a multi-meter. Hfe will shift based on bias and frequency (thus called beta instead of hfe).
If anyone do not have burned out issue yet, it may simply indicating that those three transistors are not fighting hard enough yet.
I also remember someone else has the similar issue immediately after building the amp.
Any thought ? Any input is appreciated.
Hello,
I am having issues of burned out power transistor.
After adjusting the offset to near 0V (+/-5mv) and bias to 15mv (between TP1 and TP2, and wait for few minutes), I started the music listening on one channel.
Everything is fine for few minutes, the heat sink is not hot, output is no more than 3V RMS.
Suddently, the transformer fuse (4A) at 120V side blown and sound stop.
After debug, found out that only Q17's and Q19's Collector and Emitter shorted, thus cause fuse blow. Other 4 power transistors are fine.
Since the heat sink is not hot at all and only one bias controls 6 power transistor, I have to assume the bias setting is as good as it can be.
I am guessing that the three transistors in parallel may fight with each other.
Transistor with higher hfe may try to charge transistors with lower hfe ??
To allow hfe difference among transistors, my understanding is to use R37 - R42 to minimize the hfe difference.
While looking at other similar design with parallel transistor, they were using 100-470 ohms as the base resistor.
If my understanding is correct, my question is how is the value of 2.2 ohms be determined ? Is it too small ? Or it requires very tight hfe matching ?
I do not believe matching hfe can be done just by using a multi-meter. Hfe will shift based on bias and frequency (thus called beta instead of hfe).
If anyone do not have burned out issue yet, it may simply indicating that those three transistors are not fighting hard enough yet.
I also remember someone else has the similar issue immediately after building the amp.
Any thought ? Any input is appreciated.
Performance measurements
This is the only "Test" information I have ever seen:
http://www.diyaudio.com/forums/solid-state/169590-mongrel-supersym-ii-123.html#post2430133
This is the only "Test" information I have ever seen:
http://www.diyaudio.com/forums/solid-state/169590-mongrel-supersym-ii-123.html#post2430133
Are you absolutely sure your output transistors are genuine? I ask because there are really a lot of fakes floating around.
Transistors fight each other? The emitter resistors are actually there to force the transistors to share the load regardless of hfe.
The official prototype has been playing happily for more than a year now, I even use it with my Numark Mitrack Pro for some DJ action.
The one you remember having busted outputs immediately after building the amp has been figured out already. It was the builder's fault not the circuit, he forgot to mirror the pcb when he cloned it, hence, most of the transistor leads were installed the other way around...
Re:Burned out Transistor
Hello again,
All of the transistors are from Mouser. It is as real as it can be.
I only purchase 6 power transistors per type and try to match as much as I can.
If we believe the circuit is as generic as possible, then I will go back and look for other issue.
Thanks
Lou
Are you absolutely sure your output transistors are genuine? I ask because there are really a lot of fakes floating around.
Transistors fight each other? The emitter resistors are actually there to force the transistors to share the load regardless of hfe.
The official prototype has been playing happily for more than a year now, I even use it with my Numark Mitrack Pro for some DJ action.
The one you remember having busted outputs immediately after building the amp has been figured out already. It was the builder's fault not the circuit, he forgot to mirror the pcb when he cloned it, hence, most of the transistor leads were installed the other way around...
Hello again,
All of the transistors are from Mouser. It is as real as it can be.
I only purchase 6 power transistors per type and try to match as much as I can.
If we believe the circuit is as generic as possible, then I will go back and look for other issue.
Thanks
Lou
Hi,
Okay so we can at least remove that bit of worry in our mind about the authenticity of the transistors.
The output transistors do not need any matching in this application.
I suggest you go check, and re-check your parts placement, lead orientation, etc. With your described situation I am more leaning towards parasitic oscillation as cause of those busted output transistors.
Re : Burned out transistor
Hi,
I think I find the issue and try to find the solution.
I may have thermal run away. I notice the transistor is too hot to touch while heat sink is not that hot.
This is the first time that I purchase heat sink and tap the screw by myself.
I am using thermal pad and using #4 screw to secure transistor :
a. After tapping, do I need to polish the aluminum surface ? Or just use fine grid sand paper ?
b. Will thermal grease with thermal pad help ?
I do know mica need thermal grease. But not sure for thermal pad.
c. Will washer for #4 screw apply pressure more evenly ?
d. How do I know whether the screw is not too lose nor too tight ?
e. Is there something that I need to watch out to lower thermal resistance ?
f. I am able to play music with about 30mA idle current.
I burned two pair so far. Only one pair is running for the first channel.
Thanks
Lou
Hi,
I think I find the issue and try to find the solution.
I may have thermal run away. I notice the transistor is too hot to touch while heat sink is not that hot.
This is the first time that I purchase heat sink and tap the screw by myself.
I am using thermal pad and using #4 screw to secure transistor :
a. After tapping, do I need to polish the aluminum surface ? Or just use fine grid sand paper ?
b. Will thermal grease with thermal pad help ?
I do know mica need thermal grease. But not sure for thermal pad.
c. Will washer for #4 screw apply pressure more evenly ?
d. How do I know whether the screw is not too lose nor too tight ?
e. Is there something that I need to watch out to lower thermal resistance ?
f. I am able to play music with about 30mA idle current.
I burned two pair so far. Only one pair is running for the first channel.
Thanks
Lou
If you suspect thermal runaway then those transistors blowing might not be thermally bonded to your heatsink.
a. yes you need to make it smooth and level.
b. most thermal pads don't need the use of thermal grease, though I've seen some using both so I guess that won't hurt.
c. yes a washer can distribute the clamping force of your screw over a wider area.
d. there is a recommended torque for tightening bolts for power transistors.
e. the transistor and the heatsink must be smooth and clean, also check your thermal pad if they are really that good. I leave the chewing of specs to you.
f. fyi, the official Honey Badger amp that I have in front of me now runs with an idle of 250mA. this is too much but the reason I did this is to torture the amp and see what happens if a too high idle current was inadvertently chosen. the amp runs fine with 30mA to 50mA idle current.
a. yes you need to make it smooth and level.
b. most thermal pads don't need the use of thermal grease, though I've seen some using both so I guess that won't hurt.
c. yes a washer can distribute the clamping force of your screw over a wider area.
d. there is a recommended torque for tightening bolts for power transistors.
e. the transistor and the heatsink must be smooth and clean, also check your thermal pad if they are really that good. I leave the chewing of specs to you.
f. fyi, the official Honey Badger amp that I have in front of me now runs with an idle of 250mA. this is too much but the reason I did this is to torture the amp and see what happens if a too high idle current was inadvertently chosen. the amp runs fine with 30mA to 50mA idle current.
4 ohms with 63vdc rails?
(Also posted elsewhere)
Making monoblock amps with a similar circuit, but only 2 instead of 3 OPT's.
I have a pair of 300VA 45-0-45vac transformers(63vdc rails, measured), and will be using two each of the beefier ON Semi MJL4281-4302 transistors, mounted on large 350mmx150mmx50mm heatsinks (Conrad MF35-151.5).
My speakers are rated at 4ohms (Dynaudio Focus), and therefore present a lower impedance than most.
Any concerns or cautions?
Happy Holidays!
-Chas
(Also posted elsewhere)
Making monoblock amps with a similar circuit, but only 2 instead of 3 OPT's.
I have a pair of 300VA 45-0-45vac transformers(63vdc rails, measured), and will be using two each of the beefier ON Semi MJL4281-4302 transistors, mounted on large 350mmx150mmx50mm heatsinks (Conrad MF35-151.5).
My speakers are rated at 4ohms (Dynaudio Focus), and therefore present a lower impedance than most.
Any concerns or cautions?
Happy Holidays!
-Chas
I'm no expert but can say from experience that it is risky. I built the mongrel amp (which this design came from) with the 2 output transisters NJW03, NJW0281 mounted on a conrad 300 heasink for each channel and a single 300va 45v transformer 60v rails. This ran fine while driving 6 ohm speakers, however blew the outputs when I cranked up the volume on a set of diy mini statements which go down to 4 ohm.
Life is risky ..
First of all , Jojo's construction PDF is VERY well done ... and the boards are so nice I am considering a purchase.
I test all types of used speakers and sources at the thrift shop I work at. And guess what I use ? .... the original AX/(badger)! I blew the rail fuses twice with
PA speakers(cheap/4R) , one time just the negative rail fuse blew and the amp sounded distorted but had no offset.
I started using this amp because the OEM test amps would not survive too long.
The badger is also much better at auditioning all these used speakers (they sell quick after the customer hears all that headroom) I repair many Sherwood/KLH/Sony discrete receivers/amps and they are inferior (sound/durability).
As far as instability , !! With 10pf miller compensation .. maybe ? (I detected minor ringing with a single 22pf silver mica) ,but the amp still was rock solid.
The DIYaudio badger PCB has a better layout than my "hacked" (recycled)
prototypes , so it should be even more bulletproof.
Really good work.. guys !!
BTW , my account was not hacked .. my brain was .
OS
First of all , Jojo's construction PDF is VERY well done ... and the boards are so nice I am considering a purchase.
I test all types of used speakers and sources at the thrift shop I work at. And guess what I use ? .... the original AX/(badger)! I blew the rail fuses twice with
PA speakers(cheap/4R) , one time just the negative rail fuse blew and the amp sounded distorted but had no offset.
I started using this amp because the OEM test amps would not survive too long.
The badger is also much better at auditioning all these used speakers (they sell quick after the customer hears all that headroom
) I repair many Sherwood/KLH/Sony discrete receivers/amps and they are inferior (sound/durability).As far as instability ,
!! With 10pf miller compensation .. maybe ? (I detected minor ringing with a single 22pf silver mica) ,but the amp still was rock solid.The DIYaudio badger PCB has a better layout than my "hacked" (recycled)
prototypes , so it should be even more bulletproof.
Really good work.. guys !!
BTW , my account was not hacked .. my brain was
.OS
First of all , Jojo's construction PDF is VERY well done ... and the boards are so nice I am considering a purchase.
I test all types of used speakers and sources at the thrift shop I work at. And guess what I use ? .... the original AX/(badger)! I blew the rail fuses twice with
PA speakers(cheap/4R) , one time just the negative rail fuse blew and the amp sounded distorted but had no offset.
I started using this amp because the OEM test amps would not survive too long.
The badger is also much better at auditioning all these used speakers (they sell quick after the customer hears all that headroom
As far as instability ,
The DIYaudio badger PCB has a better layout than my "hacked" (recycled)
prototypes , so it should be even more bulletproof.
Really good work.. guys !!
BTW , my account was not hacked .. my brain was
OS
Hey Ostripper, welcome back man!!!!
