diyAB Amp The "Honey Badger" build thread

[danielwritesbac]

I would like to predict for you that OsTripper's answer to exotic caps in the power supply reservoir would be paralleled panasonic or paralleled nichicon. It takes good caps, not weird caps.

In my opinion, the excellent design shown, will defeat/reduce the difference between ordinary versus high end caps on the power board. Amplifiers are mostly sensitive to any cap on the amplifier board; and, Honey Badger's power supply reservoir isn't on the amplifier board.

However. . .
Input cap, NFB caps and amplifier board power caps are plausible spots to apply some zoot because they are on the amplifier board.

[Variac]

It appears you have the deluxe chassis which has holes drilled and tapped into the heatsinks to match the mounting holes in the boards and the output devices at the correct distance in relation to the boards. The idea is to have them mounted (vertical) right onto the heatsinks using standoffs. Sure makes building an amp a whole lot easier!

Originally Posted by jimchan

quick initial questions :
- Is it recommended to mount the boards horizontal against the heatsinks ? just wondering if it would be more space efficient to mount them vertical ?

[gundul]

Hi all

I have a problem with bias setting, i checked and follow the guide...dmm on tp1 and tp2, set voltage on R30 about 20mv, wait.for a few minutes for thermal stablize recheck again after half hour, tp1 - tp2 become 25.4mv. Turned it back to 20mv. check again for another 1 hour, tp1-tp2 become 27.7mv

It happen always all the time when i checked and tried to setting bias.
Basicly it always moving up slowly but sure.

Thanks

[audiofan]

Do you have thermal coupling for Q13 to Q21 .... all 9 transistors must be on the same heatsink and have same temperature.

[gundul]

yes for thermally coupled and yes for 9 transistors on same heatsink.. But dont know if they have same temperature, i only test using my finger and looks like all 9 transistors have same temperature.



Thanks

[tsip]

Greetings to all and congratulations for providing this project to the diy community.
I have received the boards and I am beginning to populate them. I have an issue though with the jumpers and particularly those at the driver stage transistors Q14 & Q15. The jumper from the transistors base to C18, C19 have no soldering pads. Does this mean that the wire will be soldered to the capacitor and then directly on the transistor base?
regards

[JojoD818]

Hi,

The boards already have the jumpers in place so no need for any jumpers. As for C18 and C19, it was highly recommended by the designer and iirc, a few other members, that they be installed as close to the transistors as possible.

Regards

[tsip]

Thanks, good to have this clarified. Just to point out that you mean except the one next to the C1 cap(if a big size cap is used). I assume then that CRZ should be left as is as well.

[clm811]

Hi All.
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

[ostripper]

I have a problem with bias setting, i checked and follow the guide...dmm on tp1 and tp2, set voltage on R30 about 20mv, wait.for a few minutes for thermal stablize recheck again after half hour, tp1 - tp2 become 25.4mv. Turned it back to 20mv. check again for another 1 hour, tp1-tp2 become 27.7mv

This is the case with one of my AX's (larger badger -4 op devices). It finally does stabilize , but it takes longer. I did build a smaller amp like the badger and
extended the Vbe out on a short piece of flat cable to attach it directly to one of the output devices. This shortened the stabilization time considerably.
But both amps are thermally stable ... try to use an all plastic device for the Vbe .. use either a mje340 or 2sa3503 , the differences in Hfe/internal silicon structure will create a different temperature coefficient.

To go insane , one could even use a 2 device Vbe brought out to one of the output devices with a cable. This would not require reworking the board as one could design a small "daughtercard" with the 2 devices and a couple passive component quite easily. Read Doug Self's "Audio Power Amplifier Design Handbook" - thermal compensation and thermal dynamics... This is just a suggestion as I tried this for use with a "inadequate" heatsink - and it worked !The single vbe should be sufficient with most builds.

OS