Animato - A tale of degooping

[Crowella]

Yep! It's a blessing that circuit. Even to this day, still can rebrand it and sell it on. 

Updated the schematic and PCB PDF file to revision 1.06. Thanks for all the support and help. 

I'm still seeing 1.05.

Just double check the top post again, it was 1.06 for me.

[digi2t]

Ah, got it. Cheers!

[Crowella]

No problems.

I also realise that I didn't account for some electrolytic caps which I indicated on the PCB. They are electrolytic in the actual circuit but I couldn't determine the polarity but it should be simple enough to figure out as they are at the start or end of stages.

[analogguru]

The schematic (v1.06) is wrong.  There is no connection of the collector of Q5 to C11/R20.  Instead the collector of Q5 appears to be connected to the emitter of Q4 (which would make more sense).

[Crowella]

Hi analogguru, thanks for having a look at it.

I will take another look when I get home to confirm it. I have a picture here of the connections in that area. To the best of my knowledge, this is what it is but I can understand if it is wrong. I may have made an error with the connections to the pins
http://i.imgur.com/RgXlcK7h.jpg

My breadboarding failed and it may have been at that point indeed so you could well be right. Every stage up until there was correct voltage and settings so I'll give it another shot tomorrow.

[Crowella]

Analogguru, you are right and I owe you many thanks! Turns out I'm going blind with age.  

Sit tight, I'll edit the schematic/PCB to suit.

EDIT: Fixed. https://drive.google.com/file/d/0B7Lx-E88bAtEeDl6NkVUd3N5V1U/view?usp=sharing - Now 1.07, still unconfirmed but it explains my failed breadboard attempt. This is how you learn!  

[analogguru]

....
I will take another look when I get home to confirm it.

So when you have a look at it, maybe you can check if the connection S1A/S1B/DIST_A/DIST_B is connected to ground ? 

[Crowella]

This time I took the pedal apart instead of using my own reference photos and... it is. I couldn't get the pots out and there is a small wire running underneath the distortion pots to the ground on the volume. That actually explains a lot.

I should go to bed.  

Quick fix: https://drive.google.com/file/d/0B7Lx-E88bAtEblBSMU5GQUplOEE/view?usp=sharing

[Crowella]

Might post for help. Can some explain, if correct, how the last stage works?

I understand Q2 but don't understand Q1 onwards. Is Q1 an emitter follower thrown into the more common final stage of the BMP stage to act as a buffer?  

Is the first stage also a modified Dallas Rangemaster with a Sziklai pair? It looks kind of similar and according to the tests I would imagine it behaves in such a way.

[Crowella]

Sorry, I don't like posting multiple times in a row.

I managed to make a sim of the circuit in LTspice. I'm using 2N3904s and a 2N3906 to model it and it was my first attempt at biasing. I kept the "bypass capacitor" for the emitter of the pair but set it low. Not sure how necessary it would be with silicon transistors anyway.

The schematic for LTspice is here. I'm aware I will need to correct a few things in the schematic, mainly flip the tone pot around and make it linear.
https://drive.google.com/file/d/0B7Lx-E88bAtEUy0wdFpjQWh4WlU/view?usp=sharing

Little bit of horror when you max out the distortion. Any idea what's wrong there?   (Well, sort of, that capacitor plays tricks. Is it even necessary?)

[analogguru]

Might post for help. Can some explain, if correct, how the last stage works?

I understand Q2 but don't understand Q1 onwards. Is Q1 an emitter follower thrown into the more common final stage of the BMP stage to act as a buffer?  

Yes, the purpose is to lower the output impedance.

Is the first stage also a modified Dallas Rangemaster with a Sziklai pair? It looks kind of similar and according to the tests I would imagine it behaves in such a way.

No....simply because the "Dallas Rangemaster" is not an invention by itself.

The "Dallas Rangemaster" is a standard Mullard (and others) textbook transistor amplifier circuit with different (smaller) coupling capacitors.  So the question has to be: " Is the first stage a modified amplifier circuit with a Sziklai pair ?" and then the answer is: yes

I managed to make a sim of the circuit in LTspice. I'm using 2N3904s and a 2N3906 to model it and it was my first attempt at biasing. I kept the "bypass capacitor" for the emitter of the pair but set it low. Not sure how necessary it would be with silicon transistors anyway.

There is no difference between  germanium and silicon transistors  concerning the bypass capacitor.  As the name says this capacitor bypasses the emitter resistor (for AC-signals) thus increaing the AC-gain of this stage.  otherwise the maximum gain would be determined by the relation of the collector to the emitter resistor.  If this capacitor is too low, then the AC-gain for low frequencies will drop.

[Crowella]

Yes, the purpose is to lower the output impedance.

Phew. Got something right.  

No....simply because the "Dallas Rangemaster" is not an invention by itself.

The "Dallas Rangemaster" is a standard Mullard (and others) textbook transistor amplifier circuit with different (smaller) coupling capacitors.  So the question has to be: " Is the first stage a modified amplifier circuit with a Sziklai pair ?" and then the answer is: yes

Learning something new here. Thank you.  

There is no difference between  germanium and silicon transistors  concerning the bypass capacitor.  As the name says this capacitor bypasses the emitter resistor (for AC-signals) thus increaing the AC-gain of this stage.  otherwise the maximum gain would be determined by the relation of the collector to the emitter resistor.  If this capacitor is too low, then the AC-gain for low frequencies will drop.

Alright then. I've just not encountered or noticed the bypass capacitor before in circuits.

Anyway, layout confirmed. Gain for days! I can't quite nail that attacking tone with silicon transistors but the rest matches up nicely. I found the best is a BC549 but that's all I have available.

[Crowella]

I got it up and running but the attack isn't right and there is too much bass. I didn't quite read the 22uF capacitor right so I'm going to try putting a 2.2uF in there since that *may* be what it actually is. Would I be right in assuming that reducing that value will act as a cut on bass frequencies like you mentioned analogguru and increase the attack?  

EDIT: I have a youtube video demonstrating it so far. Will put up the correct schematic tonight.
?

NEW SCHEMATIC, revision 1.09: CONFIRMED
https://drive.google.com/file/d/0B7Lx-E88bAtEUG1zSDBsSXVSUWs/view?usp=sharing

[Crowella]

Bumping this. Got a build done and working, as well as a sound clip below. The silicon Sziklai pair is providing I think too much gain for the circuit but the main tones are able to be reproduced quite well. I'm using a 2N5087 and 2N5088 pair, with a 220k resistor instead of the 100k in the voltage divider (I just found it works nicely there, no particular reason)

https://soundcloud.com/adamcrowell1990/animato-clone-demo

I'll do an update to the schematic too, since I believe I got C9 the wrong way around in the schematic.

The added gain means when you push the distortion even more than the original it starts to really bring up the low end but makes the high attack rather peaky resulting in having to dial my amp down to stop the on board compressor from hating on the highs. I consider it a bonus.  

[Crowella]

Another bump. I've updated the schematic to fix an error with a capacitor polarity
https://drive.google.com/file/d/0B7Lx-E88bAtET1ViT3J2UEFpYUk/view?usp=sharing

Also made a sound demonstration with both passive bass, compared to the original as well as with an active bass, blended with an LS-2

[tommymariotti]

what does the dpdt switch do?

[Invertiguy]

what does the dpdt switch do?

It changes the bias on the Rangemaster front end by throwing in a couple of parallel resistors to ground, which shifts the EQ and gain slightly. It's not really a huge change though.

While we're on the topic of the Animato, though, does anyone have a good Hfe/leakage spec for the Sziklai pair? I'm putting together an Aion Polaris board right now and I'm having a hell of a time getting it to bias up.