Rams Head Big Muff 2N5133, FS36999 hFE notes

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Rams Head Big Muff 2N5133, FS36999 hFE notes

Postby solderman79 » 02 Jan 2019, 02:26

A few years ago I posted the actual hfe of Q1-Q4 from a 1974 Rams Bead Big Muff with FS36999 transistors as measured using a Peak DCA55. They were: Q4: 163, Q3: 214, Q2: 171, Q1: 160.

Since that time I've worked on three more pre-1975 Rams Head Big muffs. Two had FS36999 trannys and one had 2N5133 trannys. Guess what...they all measured less than 200 hfe, lol. The one with 2N5133 trannys were as follows: Q4: 132, Q3: 117, Q2: 145, Q1: 128. I also noticed Kit Rae posted some of his own measurements on his site: "When I pulled all four FS36999 transistors from an exceptional sounding 1973 Big Muff and measured the hFE I found it ranged from 164 to 204 (Q1: 164, Q2: 204, Q3: 183, Q4: 161)."

I guess my point is this; I bet the majority of the "holy grail" big muffs from the 1970s have low hfe trannys. Remember just a few years ago when everyone on the internet was swearing up and down that you needed unobtainable vintage 2N5133 trannys with hfe of 500+ to get a magical muff. I think that is just a myth. Everyone said that less than 200 hfe resulted in mud. I have found the opposite seems to be true on my socketed test board using the so called "1973 v3 or violet schematics". While the difference is subtle, to my ears lower hfe (under 200) has the effect of decreasing low end boominess and increasing clarity at the expense of a very slight loss in overall saturation.

Also, in my opinion most of the recorded BMP sounds from DG don't really sound all that high gain and aggressive if you listen carefully, but rather they are very focused, clear, and present. Certainly everyone agrees DG has recorded some of the most beautiful Big Muff sounds ever known to mankind.

Sorry, I seem to have made a rather long post, but the lore and mystic of vintage big muffs intrigues me. lol.

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Re: Rams Head Big Muff 2N5133, FS36999 hFE notes

Postby bajaman » 02 Jan 2019, 02:34

I think all those early EHX designs used the cheapest end of line components that they could find - not surprised that the transistors were low gain - lol.
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Re: Rams Head Big Muff 2N5133, FS36999 hFE notes

Postby mictester » 02 Jan 2019, 11:01

That's why I always build the BMP using a CA3046 transistor array these days. The hfe of the devices are always around 150 - 180. This "Fuzz Chip" (thanks Lance!) is also great in the old SuperFuzz and Fender Blender circuits - especially where you need accurately matched transistors for the frequency-doubling aspect of the circuit.

If you build your "Ram's Head" BMP with a CA3046, you'll get a great sounding pedal. I have used the "spare" transistor to add an optional bootstrapped buffer / pre-amp stage before the input of the main effect. This gives proper buffered bypass. The board layout is very small (and single-sided), and can be built in about 15 minutes if you have the parts on hand. If you use the Omeg sealed cermet pots, a good quality footswitch, use rubber goop over both sides of the PCB and good quality connectors in a good quality diecast box, you'll end up with a very robust, waterproof pedal that will withstand the rigours of life on the road!
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Re: Rams Head Big Muff 2N5133, FS36999 hFE notes

Postby aionios » 02 Jan 2019, 15:43

Thank you, this is great research! I've always preferred 2N3904s (150-200) to 2N5088s (350-450), but without any research backing me up on it. Sounds like the 3904 is closer to the real thing for the most part.

mictester wrote:That's why I always build the BMP using a CA3046 transistor array these days. The hfe of the devices are always around 150 - 180.


In my own experience, the through-hole CA3046's I've measured have been way down at the low end of the datasheet's listed Hfe range, around 40-50. I also tested about a dozen SMD LM3046's that were all in the 60-90 range, and a handful HFE3046's that were all in the 50-60 range. I've never seen one of any 3046 variety that tested above 100.

My total sample size is only about 25, so I don't mean this as any sort of blanket statement – but it's enough that I wouldn't trust any chip without measuring it first if I was using it in a circuit that didn't handle super low Hfe very well (for example the Superfuzz & BMP).
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Re: Rams Head Big Muff 2N5133, FS36999 hFE notes

Postby Cub » 07 Jan 2019, 08:38

mictester wrote:If you build your "Ram's Head" BMP with a CA3046, you'll get a great sounding pedal. I have used the "spare" transistor to add an optional bootstrapped buffer / pre-amp stage before the input of the main effect. This gives proper buffered bypass.

Sounds neat! That spare transistor could also be used as a booster, similar to the the Blackout Effectors Musket Fuzz and a couple of other recent Muff clones. Then an opamp wrapper, as on your 21st Century Big Muff, can take care of the buffering.
Did the CA3046 Ram's Head replace the 21st Century Big Muff as your main Muff build, or is it an added flavour?
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Re: Rams Head Big Muff 2N5133, FS36999 hFE notes

Postby digi2t » 09 Jan 2019, 13:01

Insofar as array chips are concerned, MPQ2222 are my preferred. This applies not only to BMP's, but Superfuzz as well (with a 2N2913 in the octave section). Consistently within a 150 to 200 gain range, they do a wonderful job of pushing the amp without being obnoxious.

If I want a Muff that's loud, with lots of buzz saw presence, then I'll defer to a set of BCY 59X transistors. Haven't found any transistors with more cojonas than these yet.
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