diyAB Amp The "Honey Badger" build thread

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#1,501
Connecting the screen at both ends is compulsory where vhf interference is being considered.
At audio frequencies, a screen connected at one end only is OK.

But the Audio Receiver does need to have good interference rejection at the vhf frequencies, where the (optional) one ended screen is used.

I am referring to a screen. Not to a coax, where the screen is required to achieve the double duty of signal Return AND screen. Here the Signal Return function over-rules everything else. The Signal Return MUST be CONNECTED at BOTH ends to minimise interference.
 
#1,503
Gizmosis said:
What heatsink is preferred ? just one of many question to come 😀
Click to expand...

Fresh troops for the Honey Badger Army! Welcome to the HB world. There are so many different options to build the HB. You really should read this entire thread, at least once. I wrote down notes on which items I thought were important concerning parts, values and I still had lots of "dumb" questions.

I used Heatsink USA 5" x 10" heatsinks and they get body temperature warm, depending on bias setting. The sinks did not get hot ever, not like a class A amp. Understandably so. I would have preferred a 12" long HS but 10" works as a minimum.
10.000" Wide Extruded Aluminum Heatsink - HeatsinkUSA, LLC Store
$17.10 US dollar
Ron
 
#1,504
Renron said:
Fresh troops for the Honey Badger Army! Welcome to the HB world. There are so many different options to build the HB. You really should read this entire thread, at least once. I wrote down notes on which items I thought were important concerning parts, values and I still had lots of "dumb" questions.

I used Heatsink USA 5" x 10" heatsinks and they get body temperature warm, depending on bias setting. The sinks did not get hot ever, not like a class A amp. Understandably so. I would have preferred a 12" long HS but 10" works as a minimum.
10.000" Wide Extruded Aluminum Heatsink - HeatsinkUSA, LLC Store
$17.10 US dollar
Ron
Click to expand...

That is the one i was looking at , and chassis i ordered from china, i have read the entire thread several times, but i forget soon as i shut the pc down..😀
 
#1,508
Is there any reason to check R14 for 3.75mA, if the offset is .05mV and the Bias is set at 30mV between TP1 - TP2?
R14 is rather hard to measure (safely) once the amp is built.
Tomorrow I'll hook up the preamp to the Badger, and give the garage speaker a workout.

Ron
 
#1,511
Hi guys,

I've deen doing some research on transistor pair matching. And, before I take on another load of reading and work, however fascinating, I'm wondering if the Honey Badger would benefit (significantly) from matched pairs anywhere in the circuit. Do the output devices on one side all need to be identical? Do the devices on both sides need to be exact mirrors? Etc.

It seems that some designs benefit from it, others really don't care. I'd rather not waste my time and money when there's absolutly no need for it.

I'm about to embark on reading D. Self. That'll be quite a challenge, and it'll be a while before I can really grasp what it's all about...

Thanks!

James!

PS: Renron, I'm really hoping you'll enjoy your finished Badger! Please let us know your experiences!
 
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#1,512
As resident Dummy, I'll say that I did not match ANY pair of transistors. Although in post #531 OS recommends matching a few. Each channel has a set of 3 mirrored output Transistors, PNP and NPN, they are complementary. Other transistors on the board are complementary too. Order them in sets from a vendor you trust.
I measured everything excluding Transistors, but I read each one's datasheet and checked for proper pin/leg out orientation before I soldered it on the board. I matched R and C as close as possible to the specs. Left board same values as right board. I had ZERO issues setting the DC offset or the Bias.
Having zero knowledge in electronics when I started 8 years ago, this forum has taught me quite a bit. I now know, how much I don't know. 🙂
Enjoy reading Douglas Self's papers.
Ron
 
#1,513
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#1,515
@Ron and @Bob:
Thanks for your input. That's exactly my question: will I gain performance if I put in the extra effort of carefully matching relevant transistors? Some designs don't require it, the Honey Badger may be one of those. I've read post #531, it seems it has mostly to do with LTP symmetry and DC-offset, if I understand everything correctly.

It's all fun and educational. But, concidering the potential additional cost, it should also serve a purpose.

@Ron: I agree that hanging around here and reading a lot can be quite a humbling experience 🙂 Very educational!
 
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#1,516
There are those who say that matching output devices (NPN to NPN and PNP to PNP not NPN to PNP) is worthwhile, but I haven't tried it. I don't think my current speakers are capable of resolving the difference. With bipolar devices you can count on a pretty good match if all are from the same lot.

Consider a few extras just in case, perhaps a full tube of each if budget permits. (you aren't going to stop at one amp, are you?) MJLs are cheap enough that a tube of 25 is an easy way to get all from the same lot. Mouser has always sent me same lot tubes, although mixed is possible.
 
#1,517
Stop at one amp? That depends on a) if I can complete this project satisfactorily and b) how I like it's sound and performance. Building so far proves to be quite the stretch financially, since I have nothing, save for a few tools. I have zero parts.

If all goes well and if I like what I get, I might build a multichannel version. 3 or maybe 5 channels in one package would be killer! 🙂

[edit:] my speakers are capable of quite a bit of resolution and my room goes a long way in getting all that information across as well. So, with that in mind, I would really like this amp to be better than what I have now (which doesn't at all sound bad: a Rotel RSX-1067 AVR). Some here say that it will, so I guess I'll be good.
 
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#1,520
BobEllis said:
There are those who say that matching output devices (NPN to NPN and PNP to PNP not NPN to PNP) is worthwhile, but I haven't tried it. I don't think my current speakers are capable of resolving the difference. With bipolar devices you can count on a pretty good match if all are from the same lot.

Consider a few extras just in case, perhaps a full tube of each if budget permits. (you aren't going to stop at one amp, are you?) MJLs are cheap enough that a tube of 25 is an easy way to get all from the same lot. Mouser has always sent me same lot tubes, although mixed is possible.
Click to expand...

Matching -
From my current 5 pair experience ... with the .22R Re's - if you are within
a mV Re (15mv , for example) upon being thermally stable , Good !

All the pairs should be 14-16mv (@ 60-75ma). All will be optimally AB biased.
They will all act just like one big happy single (pair of) transistors.


If your genders ( P and N) are mismatched globally (all N's the same , all
P's the same) , the amp will just compensate through DC feedback.
This usually the case with ON/Sanken.

The only bad mismatch is one "orphan" device that will settle a few mV's
higher than the rest ... it usually is defective or has a different hfe.
It will "hog" current and possibly experience thermal runaway.
Check all 6 Re's on the badger for any discrepancies.


Most mouser MJL/NJW , if bought from the same batch (tube of 10+)
will be within that mV scenario I explained.

OS
 
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