diyAB Amp The "Honey Badger" build thread

I guess there isn't any standard for that. In commercial products the connections are often made by flatcables or the terminals are directly soldered at the pcb. Maybe you could take some clear isolated stuff with polarity-marker like normal speakercables. Just take care it couldn't be confused with any other connections inside the amp.
 
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Be aware that there are different national standards and hence safety issues that are specific to our own countries or regions. The US and Australia for example have different colour coding for wiring that carries mains connected current. There are no laws that I'm aware of that say you cannot build and use appliances with wrong colour codes but common sense tells us that uniform standards and practice is the key to recognizing dangerous potentials. It really isn't wise to use anything else and in any case, there is usually a bundle of appliance cords around the home that already have the correct 10A rated and coloured triple flex inside the outer sheath.

Look at any mains plug wiring for the correct local code or if that's too difficult, you can Google colour codes for almost any country on planet earth. Australian 240V wiring colours - Google Search

If you look on the rear of any amplifier, the speaker terminals are universally red/black, right? Would that suggest something about appropriate connecting lead colours?
 
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Thanks for you input Ian. I guess I just wanted to see if there was a standard for all of these. I didn't really want to use red as my output as red is the color of my 240v input supply. So I was just asking the question. I will just avoid using colors that could be confused with a mains voltage color.
 
Thanks, I missed R3 (due to lack of knowledge :) ).

Would it be considered optimal to match the output of a passive preamp to the input of this? I am making this assumption because I match my Guitar amplifier head unit to the cabinet . I realize that in this analogy the cabinet would be the speaker load, but I figured it would be the same for the preamp to amp?
 
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Hi helitim,
If you are using a passive preamp, you are behind the 8-ball already. The lower the output impedance is for the source device (your "preamp"), the lower noice and distortion you will have. Don't forget that you have to drive the capacitance of the cables, and any non-linearities the cable alone may have. Depending on the components used, the input of a power amp may also be affected with the high output impedance.

On my service bench, a signal to drive amplifiers on my bench has a buffered output for exactly those reasons. The only commercial use of pot to input is as designed in many integrated amplifiers. They don't use shielded cable for that run so don't have anything over the input stage capacitance and non-linearities to deal with. That is a massive difference to your setup.

If I were you, I would modify your "preamp" to include a buffer for the output to drop that impedance to ohms instead of kiloohms. It doesn't need gain, just current amplification. This will also restore the correct loudness curve to your pot or switched resistor network. Nothing but pluses from where I sit. Try a diamond buffer output that has a high input impedance. THe sound quality should be improved quite a lot.

-Chris
 
Thanks Anatech. I was thinking about using a modified Pass B1 buffer (unity gain). If you are familiar with that circuit...Would that meet the buffer requirement you describe? I will look into the diamond buffer idea as well.

In the end, this whole process is more about learning for me, and I will probably make multiple options to experiment with. I don't want to take out an expensive amp in the process :).

Thanks again for the advice/ help!

- Tim
 
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Hi Tim,
An amplifier should survive most of what a preamp throws at it as long as it has a DC blocking capacitor at the input. In other words, no problem.

I'm not 100% familiar with all Nelson's work, but if it has a high input impedance it would work wonderfully. It would be a very nice sounding preamp.

-Chris
 
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Badger catches on fire!

One channel caught on fire. The power supply is +/-62vdc and the output transistors are Toshiba 2SA1302/2SC3281 purchased about 15 yrs. ago from a US distributor. After some research I believe the 1302's are fake, and failed. What do you other builders think?
 

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even with genuine parts, the amp can still go up in flames if there is a mistake in the biasing....so the use of the series lamp tester is strongly suggested to avoid the magic smoke from coming out...when doing the preliminary testing and idle current boas setting up..

FWIW, i use ON semi parts, the mjl1302 and mjl3281
 
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Hi Tony,

I've built 8 channels of the Badger, 4 using the Toshiba 1302/3281 (+/-62v supply) and 4 with the NJW0320/0281 (+/-42v supply). For initial power up I used my +/- 30v bench supply and did the initial measurements and adjustments as detailed in the build guide. The all powered up fine without a hitch. Then I would hook them up to the amp power supply and do the final adjustments, and let each channel run for at least a half hour and monitor all the test points. They all worked fine except one channel with the Toshiba transistors caught fire on the bench shortly after connecting to the +/-62v amp supply. I replaced that channel with a new pcb and parts using the toshiba transistors again and it powered up just fine. The channel in the picture blew up having been in my system and playing music for about 8 days. I could not find any errors in the build so I started suspecting the transistors.
 
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Hi audiorasp,
There are all kinds of reasons why an output stage can fail. Fake parts are one way. Bias or defects in mounting the part also kill lots of outputs a year. These days I would use On-Semi parts. It's just not worth the risk of having fake parts.

The NJW0320 and NJW0281 parts were fantastic parts. Same for the ones without the bias diodes.

-Chris