Tip102/tip107

[j9184p]

I am looking to design an amp to use to drive a powered subwoofer for my home audio system. I am looking to use TIP102/TIP107 darlington pair transistors. They are NPN/PNP. This is the first time I will be designing an amp so any help with design is greatly appreciated.

[CBS240]

Hi j9184p,

Welcome to DIYaudio!

Any thoughts on power and complexity willing to be undertaken? Specific topology?

[j9184p]

I am looking for about 100W RMS. I want to build an amp to use along with a sub for a powered subwoofer for my home theater system. I got the idea for using these D-transistors by looking at a Soundstream amp schematic. They are using 18 of em per channel for 800W RMS with +/-39.6 for the rails. I am new at designing but I spent the past three years fixing all types of electronics.

What do you mean by topology?

[richie00boy]

No offence but you clearly have a hell of a lot to learn. I would suggest you start off building a kit with good documentation, and then settle yourself down for a lot of reading.

If you want 100W RMS you will need 2 pairs of those devices per channel.

The TIP devices aren't too bad but there are better ones out there. I like Darlingtons for their ease of use and am using TIP142 and TIP147 in a design at the moment.

[j9184p]

I'll admit that there is a lot I need to learn. I have done reading on the subject of designing circuits. I got a few electronic books on the subject of engineering that I read constantly. I also have reverse engineered RF circuits and drawn up schematics due to lack of tech data. I don't have much experience with audio amps and when it comes to design, I just don't know where to start.

[richie00boy]

I suggest you start here http://sound.au.com

[Leolabs]

Hi j9184p,you can go for TIP142/147 too.Audio Analogue did use them.

[j9184p]

Thanks for the tip. I think i'll use those. What Q current should I use? Also should I use 500 or 1000 for the hfe?

[djk]

The TIP 102/107 pair are woefully inadequate for more than about 40W, the TIP 142/147 can do about 60W.

You want 100W out of a single pair of darlington devices you may want to use:

Mouser

2N6284 TRANS DARL NPN 20A 100V 160W TO3 $3.84
2N6287 TRANS DARL PNP 20A 100V 160W TO3 $3.88

second choice:

Digi-Key

MJ11015 TRANS DARL PNP 30A 120V 200W TO3 $3.65
MJ11016 TRANS DARL NPN 30A 120V 200W TO3 $3.65 (non stock)

[wrenchone]

On Semiconductor has a plastic version of the 2N6283 darlington series that may be worth a try. The old metal case devices may be hard to get these days.
I did some simulation in PSpice of amplifiers using the TIP142/147 output devices with MPSW06 and W56 in all other positions. Properly biased, I got about 0.02% THD with a single ended differential front end, and about 0.01% THD with a complementary differential front end. Harmonic distribution was not too bad, though I get better results with pure Class A designs (is anyone surprised? - I thought not...). As always, the simulations are for indicating general trends/shortening bench time, not a be-all and end-all. After all, you can't listen to a simulation. I started with a circuit out of the old Motorola power darlinton app note from circa 1973 using an extra driver stage with the emitters hooked together with a resistor. Simulated performance for the single ended differential amp was not too shabby with a 100ma output quiescent current, though the amp needed lag compensation to quell oscillation, just like in the app note... I will post some circuits if folks are interested.