Rams Head Big Muff FS36999 hFE measured

Discussion regarding early stompbox technology: 1960-1975 Please keep discussion focused and contribute what info you have...
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solderman79
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Post by solderman79 »

I would like to start by saying my post here is purely informational in nature. I've had the chance to actually measure the hfe of the FS36999 transistors in a Rams Head Big Muff. It needed new pots and all new electrolytic caps. Only one of the org. pots came with the pedal and it was coded for 1974. I have often wanted to measure these and I'm not saying that these are typical of every BM out there, only that this is what my particular one out of the 1000's made read on my Peak DCA55. I'm not trying to say that these are required mojo trannys. It's purely to document what these FS36999 happen to measure. All 4 were lot code 335 and measurements were made at room temperature. All components were removed from the transistors pcb traces for the measurements.
Q4: 163, Q3: 214, Q2: 171, Q1: 160

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Post by jay42 »

Could you talk about the tone -- is it an average one or very very good?

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Post by solderman79 »

I bought this big muff as a fixer upper. Whoever owned it before me tried to put new pots on it and did a terrible job. They messed up the wiring so bad that when I first got it home, it wouldn't even work. I installed three new pots, fixed the wiring, played it and it sounded like crap. I then went ahead and unsoldered one of the 10uf electrolytic caps, tested it and it was bad. So I replaced all 3 10uf caps, reassembled it and it worked fine. I played it like that for a while but I was never really happy with the sound. This particular Big Muff circuit had 10uf caps at C1, C2, C13, a .05uf cap at C7 and a .0068uf tone cap at C8. It had a TON of low end, lots of bass...too much for my taste anyway. So, seeing how this Big muff was not an un-molested collector piece, I modified it with all .1uf caps and a .01 cap at C8. Basically I made it a clone of the Violet BM circuit; and it I LOVE it now. It's one of my favorites. I have made many Big Muff clones in the past, and I have made them with all kinds of transistors: 2N5088, BC239C, 2N3635, SE4010, MPSA18 and 2N5133. For me, I've found that I prefer the Big Muff sound with slightly lower gain transistors, around 150-250hFE. In my opinion, their really isn't that much difference in the sound until the hFE gets below 100-125. I have tested using gains as low as 75-80 hfe and it still sounded ok.

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Post by electrosonic »

Can you accurately measure transistor specs in circuit? I would think you would need to remove them from the circuit to get accurate measurements.

Andrew.

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Post by lolbou »

electrosonic wrote:Can you accurately measure transistor specs in circuit? I would think you would need to remove them from the circuit to get accurate measurements.

Andrew.
+1 Remove these from circuit to use the DCA Analyser. :wink:
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Post by modman »

lolbou wrote:
electrosonic wrote:Can you accurately measure transistor specs in circuit? I would think you would need to remove them from the circuit to get accurate measurements.
Andrew.
+1 Remove these from circuit to use the DCA Analyser. :wink:
All components were removed from the transistors pcb traces for the measurements.
Probably so as not to damage the transistor in desoldering.

But it's no problem that you document the gain in the transistors of a vintage unit.
It's not even a problem that you use pics: but they needn't be 1MB...
If somethings going to kill the forum it's the 10GB of attachments.
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Post by solderman79 »

modman wrote:
lolbou wrote:
electrosonic wrote:Can you accurately measure transistor specs in circuit? I would think you would need to remove them from the circuit to get accurate measurements.
Andrew.
+1 Remove these from circuit to use the DCA Analyser. :wink:
All components were removed from the transistors pcb traces for the measurements.
Probably so as not to damage the transistor in desoldering.

But it's no problem that you document the gain in the transistors of a vintage unit.
It's not even a problem that you use pics: but they needn't be 1MB...
If somethings going to kill the forum it's the 10GB of attachments.
Modman, sorry for the large file size on the pics, I deleted them and will re-post with smaller files. I'm not as keen with computer software, I'm more of a hardware guy https://www.freestompboxes.org/posting.p ... 9&p=256465#

You are exactly right about me not wanting to risk damage to the transistors in de-soldering. Instead, all surrounding components were removed from the traces leading to the emitter, base, and collector of each transistor as you can see in the pics. It is much easier to de-solder and remove these other component as the leads are not as long and are mostly going straight though the board.

I made a small typo in my last post, I meant to say I have made BM clones using 2N3565 trannys, not 2N3635.
Attachments
Q4 (1024x768).jpg
Q3 (1024x755).jpg
Q2 (1024x768).jpg
Q1 (1024x768).jpg

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Post by solderman79 »

This the circuit as it was before I changed the caps out.
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IMG_0370 - Copy (1024x768) (2).jpg

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Post by uncleboko »

The ram’s head in hand bring I,
Bedeck'd with bays and rosemary.
I pray you, my masters, be merry
Quot estis in convivio

possibly not quite right :D

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Post by modman »

Doc Holiday on Musikding forum 27-10-2005 wrote:Yes, yes ... the magical FS36999 from the old Big Muff's. To make a long story short - this transistor does not exist and there was never !!! Sounds funny, I know, but is so. Here the story that, by the way, I got from Mike Matthews personally. FS36999s are quite simply 2N5088s, nothing more. EH had bought these transistors in large quantities and had them specially printed with FS36999 to drive the competition crazy. Later Muff's (RAM are thus head version, etc.) are then printed with FS36999 German (!!!) BC239 transistors.
I also very long searched for it and then unceremoniously desoldered transistors from my Triangle Big Muff and studied, I have this almost at nothing done ... X, Digital Curve tracers, HFE measurement etc. And I can from the result only MM confirm's statement ===> FS36999 = 2N5088 from the 70's !!!
http://musikding.rocks/wbb/index.php/Th ... #post69872


but then again:
Skreddy on Offsetguitars.com forum wrote:Here's what a BC239 and a 2N5088 both look like:

[ Image ]
This is called a TO-92 package.

Here's what an FS36999 looks like:
[ Image ]
This is called a TO-106 package.

There were never any 2N5088's or BC239's made in TO-106 packages. The FS36999 is almost certainly a rebranded 2N5133, and Mike likely purchased them on the surplus market like he did so many other parts that had date codes of circa 1968 on his circa 1971 BMP's. Maybe a 60's TV mfg had them custom numbered, but I do not think Mike had the money to have custom transistors made for him at that time.

http://www.offsetguitars.com/forums/vie ... 87#p628489
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Post by Bernardduur »

These FS36999 transistors are really 2N5133; I just fixed a '73 Ramshead Big Muff that had a transistor that was partially printed as 2N5133 and partially FS36999

https://www.instagram.com/p/B6O7_ISnUuz ... hare_sheet
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Post by HamishR »

I have built various versions of Big Muff with lower gain transistors - 2N2222A and 2N3904 - and really liked the results. But then I usually play them at lower gain levels, ie gain not much further up than 8-9.00. The lower gain trannies give a smooth, fat buttery sound rather than the buzz saw of the higher gain trannies. Obviously both are valid, but I really like the creamy responsiveness of the lower gain trannies.

More and more I am leaving off the second gain stage's clipping diodes too - if you're into that syrupy, vocal Gilmour tone you will probably enjoy these mods. You get more touch responsiveness. I got the idea about the clipping diodes from the Supa Tone Fuzz.

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Post by mictester »

HamishR wrote:I have built various versions of Big Muff with lower gain transistors - 2N2222A and 2N3904 - and really liked the results. But then I usually play them at lower gain levels, ie gain not much further up than 8-9.00. The lower gain trannies give a smooth, fat buttery sound rather than the buzz saw of the higher gain trannies. Obviously both are valid, but I really like the creamy responsiveness of the lower gain trannies.

More and more I am leaving off the second gain stage's clipping diodes too - if you're into that syrupy, vocal Gilmour tone you will probably enjoy these mods. You get more touch responsiveness. I got the idea about the clipping diodes from the Supa Tone Fuzz.
It's worth making the diodes switchable! I omit the first pair in some modes - and I replace them with Schottky types in others. The biggest range of tonal changes with this circuit is by changing the diodes and using low hfe transistors. I built a run of these using CA3049 transistor arrays, which have transistors with gains of around 75 - 100. I'd also recommend this chip for building reproductions of the Univox "Super Fuzz", since the original transistors in the Japanese boards were 2SC828, which are pretty low gain.
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Post by HamishR »

I used to make the diodes switchable. Reason I stopped is that with higher gain transistors the change was not so noticeable - definitely it had an effect but I always prefered the lower gain setting anyway. And while it's more noticeable with lower gain trannies I still prefer the lower fuzz setting!

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Post by solderman79 »

Bernardduur wrote:These FS36999 transistors are really 2N5133; I just fixed a '73 Ramshead Big Muff that had a transistor that was partially printed as 2N5133 and partially FS36999

https://www.instagram.com/p/B6O7_ISnUuz ... hare_sheet
Thanks for sharing that!! Very cool find indeed. It has been a few years since I originally posted this and I have worked on several more old big muffs in that time. Some had 2N5133 and others had FS36999 but they all had Hfe between 120 to 180 when measured. One might have hit 200 if I recall correctly. Kind of funny how everyone back in the early 2000's thought these vintage muffs all had insanely high hfe transistors in them.

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