diyAB Amp - The "Honey Badger"

[Rokhadin Nopianto]

thank for all

[kclusa@yahoo.co]

Hi Everyone,
I was wondering whether anyone tuned this amp ?
Can you share the experience and procedure with me please ?
Just got the PBC, collecting the parts and currently soldering everything together.
However, the capacitor selection started with WIMA cap ?
My understanding of Amp building is started the most natural sound without any high end cap. This will give the most smooth response to begin with.
If you start with high end cap, a unique sound signature already build in and will be hard to find other cap to cancel this effect plus adding the new sound signature as you desired.
Thanks
Lou

[a.wayne]

Will the badger operate with 40 volt rails ...?

[kclusa@yahoo.co]

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.

[toufu]

Hi guys, for a balanced version, can I add -IN to Q2? Thanks.

[chunek]

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

[Keith Taylor]

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

[chunek]

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

[chunek]

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

[AndrewT]

Originally Posted by chunek

I just removed the bulb..................... It is not advisible to tune bias current in bulb test as it is really not accurate. ...........

Yes, that is what is advised in many previous replies.
But, too many refuse to read !