Valve (tube) amplifier schematic help

I'm in the process of trying to build this, and I'm about to start obtaining components, but had a few questions regarding some of the specifics of the schematic.

Does the polarized capacitor marked C3 @ 1uF have to be polarized, or could it be replaced with a non-polarized one of the same capacitance?

If it has to be and I can't find a polarized cap, would a non-polarized cap and a inline diode function equivalently?

Also, in regards to the tube (I will be running a 12AT7 tube in the device) is 450mA too much current? If so, how would I go about reducing the current? Since I will be running the tube heater filament directly off a transformer designed to output at 12V / 450mA, does the output need to be rectified?

More details and information about the application as it becomes necessary.

 

How would it be bad? (I'm just wondering, I don't have much experience with this stuff)

Also, the datasheet says it runs nominally at 12.6V /150mA or 6.3V / 300 mA centre tap.

Are these things fairly "hardy" - that is, can they accept over-specifications? Obviously, it most likely leads to reduced lifespan, but as it's not something that would be continuously on, as long as it doesn't blow like a light bulb it should be fine.

If 450mA is too much over, how would I go about reducing that current level?

 

Also, I know this may be one of the most electronics-newbie-ish things you've ever heard, but can you help me with the issue of grounding?

I'm used to the rudimentary circuit notion that I picked up in elementary physics that one wire goes in, one comes out to complete the loop, so this notion of one wire leading into a circuit and other wires mysteriously going to "ground" is confusing the hell out of me to be honest haha.

I have some idea, that for most things it functions as the negative wire just like on a battery or what not, but when I get into circuits like this it really messes with me.

So is the correct interpretation that all of the electrons have a common return path and are in the same "pool" of circuit, if you will? That is, I take every wire that is marked ground and twist them all together to complete circuit?

 

Oh okay. So it's like a water hose - voltage is pressure, amperage is flow - having a lot of water moving doesn't hurt, only if it's at a high pressure. Do I have the right idea?

And my project is to integrate the tube distortion module (this) in front of an amplifier with some speakers along with a bypass to make a guitar amplifier. Hope that provides some context.

 

I intend to power this thing on the first time with a 10-foot stick if that's what you intend

 

You 100% lost me with that except for the graph showing the correlation...explain for the noob?

 

Here is my plan. I was intending to make a DIY guitar amplifier with a tube distortion effect / overdrive module. From what I've read on the subject, while it's primarily used as an effect pedal in that sense, the 12AU7 can be swapped with the 12AT7 for a more subtle effect, and conversely vice-versa.

Seeing as I had a few tubes and stuff of that nature laying around and my roommate in a month's time will be teaching me to play guitar, I figured why not try my hand at this.

Chain this tube pre-amp in-line in front of a solid-state 50W speaker amp kit that I'm going to buy and assemble. That will directly drive a coupled pair of Bose 2.75" drivers that I robbed (not in the literal sense) from a mini-iPod stereo. That way, it gets around the impedance issue. A bypass (SPDT toggle) will allow the tube overdrive module to be bypassed in favor of the dry, non-effected signal, and another bypass will allow the effected signal to be out-routed to a more powerful amplifier or combo if that is the wish. Ins and outs are all 1/4" specification TRS jacks.

 

Well, I wasn't necessarily planning on trying to overdrive the circuit as much as warm it to modify the sound.

Kris, you are correct - the valve distortion factor is mainly because the original idea was you were pushing the amplifier past its limits - and there are things at work with valves that don't quite transfer over to the solid-state realm such that the clipping, overdriven sound is not harsh and biting.

Take it for what little knowledge I have applicable, I'm an amateur electronic music producer and hard clipping on a mixer comes across very harsh to the point that it's noticeable. That's the reason the top of the VU meters is always red.

There's something about valves that softens the hard-edge clips of the sound when the input signal is too gainy. Mainly, this circuit is designed to distort the sound though and give it a darker feel. Different valves in the 12A-7 series do this to different extents, and 12AT7 is more subtle than 12AU7. From what I've read, running 12AX7 valves in this circuit isn't a good idea for whatever reason though.

 

Chris,

Is that a factor which can be controlled using the Gain pot on the circuit? If not, how would I limit it to optimize the amplifier?

Also, out of curiosity, what part of South Florida are you from, if you don't mind? I used to live down there in my childhood.