Breadboarding Germanium Big Muff Pi

[deafbutpicky]

Thanks for trying it digi2t, to the breadboard then.

[duck_arse]

I'm such an idiot. I spent mosta the weegend working at a perf layout, nice, neat, considered. signal wires at the bottom, pot wires at the top, tone/body and clipp switch on daughterboards. I got as far as the input to the buffer transistor. realised at 03:00 last, laying in bed, the fecking thing is going left-to-right, instead of right-to-left.

bugger. there is sure to be something go wrong in the transposing .....

[digi2t]

I'm such an idiot. I spent mosta the weegend working at a perf layout, nice, neat, considered. signal wires at the bottom, pot wires at the top, tone/body and clipp switch on daughterboards. I got as far as the input to the buffer transistor. realised at 03:00 last, laying in bed, the fecking thing is going left-to-right, instead of right-to-left.

bugger. there is sure to be something go wrong in the transposing .....

Would this help? It's an NPN version, but I don't think it would take much to rework it. Let me know if you want the diylc file.

[lmorse]

Sorry its taken so long.

Who else finds that work gets in the way of life?



Happy to share the cad files if anyone wants them, just PM me.

[bluebunny]

Who else finds that work gets in the way of life?

Back of the queue, mate - back of the queue.    That's a whole separate thread!

[digi2t]

Who else finds that work gets in the way of life?

Raises hand.

Is there a higher resolution version of this schematic? It's kinds of hard to read.

BTW, shouldn't that 1M resistor (R24?) be on the input?

[duck_arse]

lee - if my eyes are squinting correctly, your supply bypass electro is backwards.

digi2 - well, thanks, that would help, except my boards are only 10 rows high. I think I can do it with some room spare (he says, knowing full well something will come along and stooge him).

and now I have a real technical question about the circuit operation. at the input of each stage is an R and a C in series. knowing the order in a series circuit doesn't matter, does the order of the cap and resistor in this case matter? the cap blocks and freq limits/shapes, but what part does the resistance of the resistor play?

I only arks because I swap them as they will fit on the board best. and because I now have to go back to my circuit and swap a few places.

[digi2t]

lee - if my eyes are squinting correctly, your supply bypass electro is backwards.

digi2 - well, thanks, that would help, except my boards are only 10 rows high. I think I can do it with some room spare (he says, knowing full well something will come along and stooge him).

and now I have a real technical question about the circuit operation. at the input of each stage is an R and a C in series. knowing the order in a series circuit doesn't matter, does the order of the cap and resistor in this case matter? the cap blocks and freq limits/shapes, but what part does the resistance of the resistor play?

I only arks because I swap them as they will fit on the board best. and because I now have to go back to my circuit and swap a few places.

That's a fine question. To my noobish eyes, the series resistor, combined with the base resistor right after it, might be responsible for setting up the gain of the next stage. Would sticking the cap in between here create a problem? I don't know. That's above my pay grade, though, I should would like to know.

[crb3]

Transistors are 2SB176,

My favourite germs

mac

Sounds like you're going for minimum transistion frequency... Typical f-ab is listed at 700 KHz on the 2SB176 datasheet; that's the lowest I've seen yet (AC128, 2N527 typically 1.5 MHz; 2N1303 at 3 MHz). Hmmm, I might just have to dig into my junkbox and see if I've got any of those on hand from my scroungy days.

[lmorse]

lee - if my eyes are squinting correctly, your supply bypass electro is backwards.

BTW, shouldn't that 1M resistor (R24?) be on the input?

Oooops, thanks for the spots. That'll teach me to rush things!

Is there a higher resolution version of this schematic?

That'll be Photobucket squishing the image, sorry.

Why can't I get images working from the gallery? Here's the link:

http://www.aronnelson.com/gallery/main.php/v/diyuser/BMP+Germanium+with+Mods.jpg.html?g2_imageViewsIndex=1

[Keppy]

C4 & C13 are backwards as well, though they are small values and not likely to be polarized caps. The LED needs to be flipped as well.

[lmorse]

Flipped, thanks. They are not polarized in my breadboard, that's probably why I didn't spot the mistake.

[bluebunny]

Why can't I get images working from the gallery?

It's because you're linking to the HTML page containing the picture, not to the picture itself.  You can right-click on the image and choose "Copy image URL" (or the equivalent incantation for your browser) and paste that between the [img][/img] tags.

[mac]

Sounds like you're going for minimum transistion frequency... Typical f-ab is listed at 700 KHz on the 2SB176 datasheet; that's the lowest I've seen yet (AC128, 2N527 typically 1.5 MHz; 2N1303 at 3 MHz). Hmmm, I might just have to dig into my junkbox and see if I've got any of those on hand from my scroungy days.

In my experience Matsushitas 2sb17x family have more highs than ACxxx... 

mac

[duck_arse]

@digi2 - please to tell - the 100nF hanging under the tone pot in your diagram, how does that affect the response? (duncan's won't run on my modern linux.)



I've just, finally, gotten this on the bb. 10k instead of 100k, 470k missing, 1n5 instead 15nF, 100nF instead of 10nF ..... my experience was less than inspiring, but I know what to change when I'm at it tomorrow.

(thus far I've got 1n4148's doing the bias, w/ some 11k collector and some 91k base resistors, ge clip Q2 and schottky Q3.)

[digi2t]

What are you using for transistors?

Here are screen shots of the tone section, from one extreme to the other. 15n cap, 3k3 resistor, 25k pot;

[lmorse]

Christmas holidays over

(shouts of "booo!")


I did manage to finally finish up my Germanium BMP over the Christmas holidays, and I love it. To answer Duck's question from last year:

orright lee, I don't think anyone has arksed yet, so I'll be the first: "what transistor types did you settle on, and what gains and leaks are in what positions?" please.

Listed as per the Big Muff Page with transistors numbered in reverse - so Q4 is the transistor immediately after the input, Q1 is the transistor just before output:
Q4 hfe259, leakage 161
Q3 hfe267, leakage 158
Q2 hfe346, leakage 173
Q1 hfe397, leakage 161



I have added switches to knock out the clipping diodes, and to switch between a 4.7n and a 22n cap in the tone stack. A few issues still with the etching so it's a bit blotchy, lettering not quite lined up etc (bought one of the new Samsung mono printers for Christmas which is awesome) - and after watching this http://music.codydeschenes.com/?page_id=2035 I think I must have a poor batch of ferric, by coincidence I have been using the same 'dipping' technique, but my etch to get this deep took 55 minutes.

... planning a Java Boost next.

[digi2t]

I finally got around to doing a video of what I have on the breadboard. I like it... except for the hiss I hear when I've got the sustain anywhere over 3. I'm thinking it's the leakage of the transistors, maybe I'll make it a hybrid, and use silicon in the first and last stages. I'll have to try it though.

Anyway, on with the shoe...

EDIT:
Replacing the first stage germanium with a 2N5087 made a world of difference. I'm still getting the Ge tone, but the hiss level has really gone down tremendously. I can dial the sustain up higher now, and the hiss is at a much more tolerable level. Not totally quiet mind you, but WAY better.

[duck_arse]

digi - my mind is slipping. I'm sure, after asking you about a 100nF in the tone stage, I posted how stupid I was for misreading that cap value about 1,000,000 times. now I can't see such a posting. I can't even say I posted it and it got lost, because the whole site went down around that time. hmmm.

anyway. breadboard? geeze, even I've finsished the codpie perf, and the codpow inverter to suit, and picked a box to recycle. no pots/knobs/paint yet, but I've pencil sketched the next version, smd on perf. no box or knobs for that either. and with 3 boxes now painted ready for final assmbly, and all the other half builds lying around on the bench, and the junk I'm supposed to be breadding and scope-ing, etc, today I decided I needed to start cutting f holes. badly.

is that yer burst box in the background, start of video?

[digi2t]

digi - my mind is slipping. I'm sure, after asking you about a 100nF in the tone stage, I posted how stupid I was for misreading that cap value about 1,000,000 times. now I can't see such a posting. I can't even say I posted it and it got lost, because the whole site went down around that time. hmmm.

anyway. breadboard? geeze, even I've finsished the codpie perf, and the codpow inverter to suit, and picked a box to recycle. no pots/knobs/paint yet, but I've pencil sketched the next version, smd on perf. no box or knobs for that either. and with 3 boxes now painted ready for final assmbly, and all the other half builds lying around on the bench, and the junk I'm supposed to be breadding and scope-ing, etc, today I decided I needed to start cutting f holes. badly.

is that yer burst box in the background, start of video?

Ha ha duckie... you're expanding my vocabulary! 

The whole thing has been sitting on the breadboard because of two PLL builds that I had to get done for folks. Anywho, do you get that hissing with all ge transistors, or is it just me? Try a si transistor in q1 if so, and let me know what you think.

Burst box? You mean in the vise? That's the Breg Sweep wah.