TIP29 fuzz

[bluebunny]

I thought the "B" stood for "Bratwurst"...   

[PRR]

Coming late to dinner...

> how come Q1, with grounded emitter, is only 250mV at the base?

2N3055 is a nominal 15A part. 15,000mA!

Here it is run at 8V/22K= 0.3mA.

40,000 times smaller than it "could" do.

Junction drop changes 20mV for 2:1 change of current, 60mV for 10:1 change.

60mV+60mV+60mV+60mV+20mV+20mV= um um um 280mV.

Taking "600mV" as the nominal junction drop at "intended" current, this super-tiny current should cause Vbe=320mV.

Which is in sight of 250mV. But not quite there.

More complication: 2N3055's Vbe at 15A is over a Volt, not 600mV. But much of this excess is stray resistance which drops-out at very low current.

Fiddling in SPICE with Duncan's 2N3055 model, I do not get Vbe as low as 250mV. More like 450mV. Taking the no-parasitic Vbe of '3055 at 15A (which is really socking it to the Silicon) as ~~730mV, this does come out right for 0.3mA.

Another way to "drop Vbe" is to take the collector WAY high, near breakdown, so C-B leakage dominates the junction. But for '3055 that would be way over 60V, and he's only got 9.5V.

TIP29 should not be majorly different.

Do not know why Gus' sim shows 250mV. Can't really care.

[duck_arse]

as ever, thanks paul.

[Gus]

Finally finished putting the circuit in an enclosure

Measured voltages
Q1 base .54VDC
Q1 collector 1.5VDC
Q2 collector 7.28VDC
Supply voltage 9.66VDC

[Cozybuilder]

Photo?

[Gus]

recent builds clockwise from top left
silicon supa like
PN2222 one control fuzz 1.6VDC 7VDC

TIP29 one control fuzz

4 control fuzz with input cap selector switch
over the top BMP
another one control fuzz
another one control fuzz
The one controls have different biasing and other adjustments. I have a few more built that need to be boxed.

[Gus]

A bump because I have not seem much about power transistor overdrive or fuzz circuits

[tubegeek]

I just got in some TIP31 and TIP32 for my mini amplifier project, I might well try this thing at some point. So just a little re-bump to say Thanks Gus for all the interesting design work!

[Mark Hammer]

One knob, two transistors? Shoot, this sounded like it should fit in a 1590LB. It does.

2N3055 Q1, TIP31c Q2, BS170 Millennium Bypass, Wima 1uF poly out, short Panasonic 100uF 16V electros; trimmed jacks & transistors, ⅝" standoffs with 2-56 screws; and a bit of head scratching to make it all fit. (& yes, it was worth it)

Cheers and thanks to Gus for another interesting, great sounding design

I was going to make a snarky comment and ask "But can it fit in a 1590A?".  However, clearly it can, with a bit of planning and wise jack/switch choice.

[Rob Strand]

Cozy builder did some great builds.   He always raised the bar on what could be done.    It's all hand-wired stuff, not two-sided boards and SMD parts.

[tubegeek]

Stuff like this blows my mind. I have trouble fitting some builds on my workbench.

[amptramp]

This is good - the low bias voltage of germanium without the leakage current.

2N3055 has now become a catch-all number for power transistors that do not quite meet the specifications of later power transistors so if, say, Hfe was too low, it might get packaged as a 2N3055 rather than whatever it was supposed to be.  Manufacturers sometimes do their own counterfeiting.

[Rob Strand]

2N3055 has now become a catch-all number for power transistors that do not quite meet the specifications of later power transistors so if, say, Hfe was too low, it might get packaged as a 2N3055 rather than whatever it was supposed to be.  Manufacturers sometimes do their own counterfeiting.

Some years back there were fake 2N3055's effectively 2N3904 rating transistors inside.  They test out OK but when you
put any sort of load on them they fry.

[edvard]

Well bust my buttons, I've thought of this kind of thing many times but never took the plunge.  Nice!
I'd like to see a build with 1/2 watt resistors and bumblebee caps around two big ol' TO-3 transistors, woop!! 

[tubegeek]

OK, so digging through the Miscellaneous Old Semiconductors stash I got a few years back, I find a bunch of useful items. Just pulling out the TO-220's as a starting point

NPN's:
TIP3055's with hfe's of 229, 179, 193, 108, 73
MJE3055; 19
EP2437; 16, 13
MJE5984; 37

And a fair few PNP'S as well.

Starting with the 108 and 179 TIP3055's for now.

[Rob Strand]

The large devices have a *lot* more capacitance which smooth out the sound of silicons.

[tubegeek]

The large devices have a *lot* more capacitance which smooth out the sound of silicons.

Is there much to be gained in that regard by going from TO-220 to the big TO-3 package types? (I don't happen to have any TO-3 on hand at the moment.)

[highwater]

If they're the same part number in a bigger package, not likely. The capacitance could even be slightly *less* simply because the leads (and bonding wires inside) are farther apart from each-other.

[mac]

Try those inside low consumption lights, hfe: 20. Good for darlingtons.

mac