Tycobrahe - Octavia  [schematic]

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

125B is for sissy boys and gay people (no offense Tube Exorcist)
Do one for DEM size-E with big audio transformer and wall powered. Should have bigger headrom that way

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Post by rosetta »

Image

PLZ. 1590b and sounds awsome.

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Post by beedotman »

:lol:

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Post by sinner »

Are you trying to tell me that the enlosure size doesn't matter?

Sounds heretic

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beedotman
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Post by beedotman »

sounds like complex :lol:

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Post by warioblast »



I have a Tyco on my breadboard. I've tried 3 variations of the circuit; Mr Huge's Tycobrahe schematic, the hand drawn one and the Dunlop Octavio. No matter how I combine the dozen different types of transistors I have I don't get such a nasty and thick sound. :cry:

I've had the GGG Tyco and the wedge Dunlop octavio. I've watched a bunch of YT videos of different clones and I'm starting to believe the guys who claim that there is nothing like an original Tycobrahe.

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Post by 4ab3c1b »

Howdy folks, first post here. This thread is pretty old with a good bit of "link rot", but from the surviving gut shots it seems Q1 is reversed from some of the common schematics floating around the web (GGG and Fuzz Central), with emitter connected to the 220r and 220k etc. The Jeorge Tripps-drawn schematic I have backs that up.

Can anyone confirm that the original Tycobrahe transistors are MPSA18, 2x 2N6519?

Thanks!

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Post by dv8r601 »

4ab3c1b wrote:Howdy folks, first post here. This thread is pretty old with a good bit of "link rot", but from the surviving gut shots it seems Q1 is reversed from some of the common schematics floating around the web (GGG and Fuzz Central), with emitter connected to the 220r and 220k etc. The Jeorge Tripps-drawn schematic I have backs that up.

Can anyone confirm that the original Tycobrahe transistors are MPSA18, 2x 2N6519?

Thanks!

I can confirm the q1 is MPSA18. I'm looking for pics of the others as we speak.
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Screenshot_2018-06-06-20-18-07-02.jpeg

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Post by dv8r601 »

Here ya go you can clearly see they're MPSA18 and MPS6519
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TycobraheOctavia-2_zps9225b096.jpg

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The Rotagilla
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Post by The Rotagilla »

I got the GGG kit the other day and have been collecting schematics along the way. Some observations...

1) With the exception of the early hand drawn and Dunlop schematics, all the others seem to be the same. Am I missing some glaring discrepancies?

2) The completed GGG kit left me underwhelmed so I started digging around and checking things.

- MPSA18's have a gain range of 500-1500hfe (according to current datasheets). I built the negative ground version which uses a 2N5087 and has a gain range of 250-900hfe. I did not measure mine yet.

- MPS6519's have a gain range of 250-500hfe (according to current datasheets). The GGG kit uses 2N4401's and they have a gain range of 100-300hfe.

3) I kept the 2N5087 because I didn't have anything else on hand but swapped the 2N4401's for 2N5088's and noticed an improvement. The fuzz portion sounds closer to what it should.

4) I had read that the diodes need to have low forward voltage ratings and some people posted that they got better octave results if the diodes were matched. I did swap out the Ge diodes GGG sent with some low forward voltage ones I had and got a stronger octave.

5) I have a Chicago Iron Octavia coming in tomorrow, I'll dissect and report.
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Post by The Rotagilla »

Chicago Iron Octavia #20.

1) It is a 1:1 clone of the Tycobrahe.

2) One of the electrolytic caps was blacked out and I'm not sure why because it was the 100µF.

3) Q1 had the numbers scratched off but the hFE was 1039 per my Peak DCA55 and the emitter does go to the 220k/220r.

4) Q2 and Q3 were MPS6519's.

5) The diodes were matched.

6) My negative ground GGG build sounds exactly the same.

That's all.
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Post by 4ab3c1b »

Wow, I've been gone for a while!

Thanks to all those who responded to my questions, but I was able to find out via other means what everyone has confirmed here. MPSA18, MPS6519, "backwards" Q1, etc...
6) My negative ground GGG build sounds exactly the same.
The GGG schematic has Q1 reversed compared the Tyco originals, but the circuit works either way, and sounds about the same.
4) I had read that the diodes need to have low forward voltage ratings and some people posted that they got better octave results if the diodes were matched.
This is mostly true. Matched, yes, but you can go too low on Vf and the tone gets thin and shitty. The "ideal" forward voltage probably depends on the gain of the transistors, the specific transformer used, and maybe also what guitar/pickups you plug into it.

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