Newbie Help
Hi,
I am building the Honey Badger amp first time out. I've read a lot on this forum, but before I proceed, I would like some basic help on some rudimentary questions about this amp.
I have attached the PCB board design with the interface points on the board. Hope to get some help on the following.
1. Do I connect the +- VDC rails to V- and V+ accordingly?
For example, -45v - 0v - +45v, hence I connect the -45v to V- and +45 to V+?
2. GND is where I connect the 0v center tap from transformer?
3. From the schematics, I realize there is 2 ground types, GND1 and GND2. Are they the same?
4. Do I connect the to speakers in the following way: Output -> speaker + and SPK GND -> speaker -?
5. For audio in, i just connect the + and - from a preamplifier audio output to IN --> + audio signal, 0V --> - audio signal?
6. Should the -ve audio signal be grounded with SPK GND?
7. I plan to operate this amp with 4ohm and 8 ohm speakers. What is the best transformer specs to use?
8. Anywhere I can get the PSU rectifying board PCB design in Gerber or Sprint Layout format?
9. What speaker protection board should be used with this amp?
Thanks for all the help. appreciate for your answers in advance.
Hi,
I am building the Honey Badger amp first time out. I've read a lot on this forum, but before I proceed, I would like some basic help on some rudimentary questions about this amp.
I have attached the PCB board design with the interface points on the board. Hope to get some help on the following.
1. Do I connect the +- VDC rails to V- and V+ accordingly?
For example, -45v - 0v - +45v, hence I connect the -45v to V- and +45 to V+?
2. GND is where I connect the 0v center tap from transformer?
3. From the schematics, I realize there is 2 ground types, GND1 and GND2. Are they the same?
4. Do I connect the to speakers in the following way: Output -> speaker + and SPK GND -> speaker -?
5. For audio in, i just connect the + and - from a preamplifier audio output to IN --> + audio signal, 0V --> - audio signal?
6. Should the -ve audio signal be grounded with SPK GND?
7. I plan to operate this amp with 4ohm and 8 ohm speakers. What is the best transformer specs to use?
8. Anywhere I can get the PSU rectifying board PCB design in Gerber or Sprint Layout format?
9. What speaker protection board should be used with this amp?
Thanks for all the help. appreciate for your answers in advance.
Attachments
Run away bias. When I am trying to set my bias at around 15 MV the bias takes off on its own and by the time I shut the power down it could be 70+ MV. When I turn the amp back on the bias is back down but runs away as sone as I start turning the resistor. A few months back when I first completed this amp I had the same problem on this channel so my solution was to order new boards and rebuild the channel I have been playing music with success at a bias around 12 MV but sometimes really load passages will set the bias running a quick on off will fix it any ideas?
yes..
yes unless you have a filter bank off board..
yes
yes
yes
no, there is a ground point with the input
at least 300 va
i doubt you can get the gerbers, this a forum commissioned amp...
there is no SOA protection scheme on board....
dc detect and peaker delay can be found in the diyaudio store .. Soft Start & Speaker Turn-On Delay / DC Protector Combo – diyAudio Store
Thanks Tony and everyone else here for your input. Very much appreciated.
So much great advice and helpful people on DIY Audio [emoji3][emoji16][emoji3]
Anatech. Yes I agree it seems odd that this same problem would happen on 2 separate builds. I do not have a scope which is why I decided to just rebuild this channel and I had most of the parts Could this be a bad batch of transistors or a pair that is poorly matched if so which ones are most likely?
I don't have much first hand experience solving oscillation but more experienced members can tell you where to look be seeing what frequency the oscillation is occurring at.
You would need a signal generator to go along with a scope. You can pick up used equipment fairly cheap or there are some inexpensive USB options that work fairly well. I keep a cheap Vellemen USB scope on my bench for quick testing. I pull out a better unit for more precise measurements though. It has a built in signal generator.
PCSU1000: 2-CHANNEL USB PC OSCILLOSCOPE – Velleman, Inc.
There are lots of Youtube videos available on operating a scope. One thing to remember is to always keep the probes set on 10x to protect your scope from high voltage mistakes. It's not a bad idea to crazy glue the switches in that position.
You would need a signal generator to go along with a scope. You can pick up used equipment fairly cheap or there are some inexpensive USB options that work fairly well. I keep a cheap Vellemen USB scope on my bench for quick testing. I pull out a better unit for more precise measurements though. It has a built in signal generator.
PCSU1000: 2-CHANNEL USB PC OSCILLOSCOPE – Velleman, Inc.
There are lots of Youtube videos available on operating a scope. One thing to remember is to always keep the probes set on 10x to protect your scope from high voltage mistakes. It's not a bad idea to crazy glue the switches in that position.
Hi rock12,
You really, really do need an oscilloscope. An older analogue one would be the best as you won't run into a lot of problems that digital 'scopes have. The input is also a lot more rugged than the USB scopes.
See if you know someone, or if there is a member near you that can help out. If you were close to me I wouldn't hesitate to put your amps on the bench and have a look see.
Any capacitors from Ebay? If so, yank them and buy some new ones from Digikey, Mouser or someone like that. Make certain breakdown voltages are more than what you are applying to them.
Matching won't cause oscillation. Transistors that are not what they claim to be most certainly can. Any transistors from Ebay? Change them out for known real parts. Same sources as the capacitors. You might want to check the resistors also. I have seen inductive metal film resistors (Ebay).
-Chris
You really, really do need an oscilloscope. An older analogue one would be the best as you won't run into a lot of problems that digital 'scopes have. The input is also a lot more rugged than the USB scopes.
See if you know someone, or if there is a member near you that can help out. If you were close to me I wouldn't hesitate to put your amps on the bench and have a look see.
Any capacitors from Ebay? If so, yank them and buy some new ones from Digikey, Mouser or someone like that. Make certain breakdown voltages are more than what you are applying to them.
Matching won't cause oscillation. Transistors that are not what they claim to be most certainly can. Any transistors from Ebay? Change them out for known real parts. Same sources as the capacitors. You might want to check the resistors also. I have seen inductive metal film resistors (Ebay).
-Chris
you need also a signal generator, look out for a Heatkit IG-18, they should sell cheap over there and a scope at least 20mhz, 8 ohm 1000 watt dummy loads are now very cheap, i got 6 of those....
i suppose that yoour two channels feed from the same psu...
so try to get the input ltp trannies well matched in terms of hFE...
i suppose that yoour two channels feed from the same psu...
so try to get the input ltp trannies well matched in terms of hFE...
Hi rock12,
An oscilloscope is easy to use. All you need is some confidence and a quick lesson. For almost everything you can do in this hobby, you need an oscilloscope. At the very least, it will make understanding what is going on easier.
Remember, every one of us started in your shoes. I had to teach myself how to use a 'scope, no help from anyone. Books from the library helped, but now there are literally thousands of members here that can answer questions and help you through it. You're in better shape to learn than most of us were in your situation.
-Chris
An oscilloscope is easy to use. All you need is some confidence and a quick lesson. For almost everything you can do in this hobby, you need an oscilloscope. At the very least, it will make understanding what is going on easier.
Remember, every one of us started in your shoes. I had to teach myself how to use a 'scope, no help from anyone. Books from the library helped, but now there are literally thousands of members here that can answer questions and help you through it. You're in better shape to learn than most of us were in your situation.
-Chris
A quick test to see for oscillation. Take one 1ohm 1/4watt resistor and one 100nf/250v capacitor. Connect this in series. One wire from resistor & one wire from the capacitor together. Desolder the original zobel and connect this circuit instead. Play some music or some test signals if available. Touch the resistor, is it hot, can you smell something? If yes, your amplifier is unstable. Another way is the overcompensation. Add more caps in parallel to comp. caps. Are you sure that your speaker isn't fault? Measuring with an ohmmeter the disconnected speaker, you can see if a non normal reading. Good luck!
Input pair Hfe or current mirror Hfe in excess can also cause the Badger to oscillate. I actually did this on the similar wolverine , but just doubled R in the
current mirror degeneration resistors. The Badger's TMC magnifies the effect of excess gain in the input stage.
There is a very wide range of gain classes for the to-92's <100 to 800+ , insufficient phase margin might occur at extreme Hfe. I used my DVM to get @ 200Hfe for all my to-92's.
Just another possibility. PS - The spice transistor models for the Badger and all my other designs average 200-300hfe. Margins were based on these.
Edit 2 - actually that is the trick to using very high Hfe devices - example - 600hfe input pair = double its degeneration R , it will then approximate a 300Hfe. This will not affect the Badger's general operation , BTW. OS
current mirror degeneration resistors. The Badger's TMC magnifies the effect of excess gain in the input stage.
There is a very wide range of gain classes for the to-92's <100 to 800+ , insufficient phase margin might occur at extreme Hfe. I used my DVM to get @ 200Hfe for all my to-92's.
Just another possibility. PS - The spice transistor models for the Badger and all my other designs average 200-300hfe. Margins were based on these.
Edit 2 - actually that is the trick to using very high Hfe devices - example - 600hfe input pair = double its degeneration R , it will then approximate a 300Hfe. This will not affect the Badger's general operation , BTW. OS
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