Tube Screamer Schematic Analysis

Рет қаралды 8,123

The Andromeda Corporation

Күн бұрын

Пікірлер: 39

@joet4348 Жыл бұрын

Great video, thanks for posting. At 6:44 I believe the equation should be Av = 1 + Rf/Rg for a non inverting op amp

@theandromedacorporation 11 ай бұрын

You're right! I'm always forgetting about that +1. Luckily my error is fairly negligible compared to the influence the distortion pot has. Good catch!

@grahamhart721 6 ай бұрын

Dude! I need this lol, I’m brand new to building pedals but I’m seriously fascinated with everything. PLEASE do more of these videos for the other popular circuits. You’re the only one I’ve found that actually explains what all the components are actually doing and it’s super helpful. Thanks!

@bobsbarnworkshop Жыл бұрын

C3 actually blocks DC gain. With the input sitting at 4.5 vdc, the gain of the op amp would drive the output constantly to the positive rail

@theandromedacorporation 11 ай бұрын

True.

@MichaelFairhurst 11 ай бұрын

Hmm, I'm new to this, am I understanding correctly? I get the gist that if the op amp sees, say, 5v on the noninverting input, it's output must be ~5.7V to compensate for the D2's voltage drop (minus whatever gets through the level pot). Hopefully got that right. To soft clip a "negative" signal like 4v, we need a negative voltage crossing D1. C3 and R4 are a high pass circuit with a center frequency of 720hz. So lower frequencies, including DC, are blocked. That means C3 is usually charged to 4.5v, which means the opamp sees 4.5v on the - pin and 4v on the + pin....it tries to sink .5v of current but has to sink an extra .7v to overcome D1's voltage drop (minus whatever flows through the level pot), and it sources that current from C3? So the saturation curve is linear with some slope (set by the feedback resistor), and when the output of the curve hits .7v, the curve is linear with a slope of 1? Thanks in advance. And, if I'm wrong all over the place, I apologize and don't expect a super thorough correction, I just need to go back to basics if so I think.

@OreilleGauche 5 ай бұрын

Great, great explanation! funny and to the point. Exactly what I needed. Thaaaaannnnks!

@cwrigh13 2 ай бұрын

Great explanation. Thanks for sharing

@planker Жыл бұрын

Excellent

@MichaelFairhurst 11 ай бұрын

I'd actually really enjoy an explanation of the JFET bypass circuit! Is it a common bypass utilized often in pedals?

@theandromedacorporation 9 ай бұрын

I think the website electrosmash has a good walk through of that buffered bypass circuit. Check there. Most pedals are “true bypass” in my experience. I

@Liushenfanushui Жыл бұрын

R4 4.7k and P3 100k are both connected to 4.5V V bias instead of Ground. You can open up an 808 or 9 and see. I've studied TS/ DS-1/ Klon schematics from ElectroSmash so far, lots of time spent, and I found that all of them had a little bit of differences. An object or a reliable replicant is needed when you really want to understand the whole thing through.

@theandromedacorporation 11 ай бұрын

Interesting. Thanks for the insight! Yeah, did a quick google search and I found an example that's biased like you describe. Luckily those differences don't really change what's going on in the circuit. R4 could be biased to either voltage or even +9V and not have any audible difference since audio sees all kinds of stuff as ground, and if I'm not mistaken the gain on the input amp would still be very close to 1 if you bias R3 to either 0V or 4.5V, so that's no biggie either. I wonder if these differences are accurate depictions of different circuit board revisions, or if somebody made an error while copying the circuit.

@mikegardner5859 Жыл бұрын

Surely, the battery negative will be disconnected from all parts of the circuit as soon as the input has anything plugged in! Likewise, the Power Supply negative has no connection to any part of the circuit at any time. Is this intentional?

@theandromedacorporation 11 ай бұрын

Not sure I fully understand your question, but the negative end of a power source here is what we call ground. If it's not connected to the circuit you'll have an "open circuit" and the circuit wont work. All those points with layers of lines are the negative terminal of a power supply. So, there are a whole bucket of connections from power supply negative to the circuit. Hope that answers the Q.

@mikegardner5859 11 ай бұрын

@@theandromedacorporation Thanks for taking the time to reply, that clarifies the point behind the query as there are plenty of connections to ground showing on the schematic, but nothing showing the connection between the battery negative and ground.

@theandromedacorporation 11 ай бұрын

@@mikegardner5859 Right. It's pretty typical in this sort of schematic to see multiple nodes labeled as voltages and ground without actually including a symbol for the power source that supplies those voltages.

@stephenmonike1906 10 ай бұрын

How would you boost the output volume in the output section of the schematic?

@theandromedacorporation 10 ай бұрын

@@stephenmonike1906 I wouldn't. The circuit amplifies the signal up, and then the volume knob turns it all back down. If you're building a tube screamer and it's quieter than your input signal you've probably got the wrong resistance somewhere in the opamp stages, or something like that.

@PorkPioneer Жыл бұрын

Dumb question about the JFET Bypass switch in the very beginning: The first schematic is an example of a pedal WITHOUT true bypass? And true bypass is a simpler way to do it than the JFET Bypass switch?

@theandromedacorporation 11 ай бұрын

Yeah, true bypass is basically a switch that flips between your input passing through the pedal circuit and then to the output, or simply connecting your input jack straight to the output jack.

@pfbrodriguez 7 ай бұрын

can this bypass be replaced by a dpdt switch ?

@AlexusDelphi 9 ай бұрын

What's the resistor labeled RA?

@dratonbalat3423 4 ай бұрын

1. 3db drop is 50%. 2. Think of the diodes on the first opamp as bleeders

@TedSchoenling 9 ай бұрын

thought that was a filter cap on the power there.. (C17)

@NotMarkKnopfler 10 ай бұрын

There's no bypass path for when the pedal is not engaged.

@theandromedacorporation 9 ай бұрын

Actually that whole orange section labeled "JFET Bypass Switch" is the bypass path. It's not a typical "true bypass" though, so even when you switch the pedal off there is at least a buffer and some other stuff going on. So in that sense this circuit never fully turns off. If you want to mod it with a true bypass that would be super easy though.