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Discussion in 'Shock Brother's DIY Amps' started by dunehunter, Feb 9, 2019.
Thanks @King Fan. Glad to see you here!
mm? You lost me.
Where are you from?
Well, after a day of prep and a day of colonoscopy from hell, I'm back now...
So here's a quick question before i get off on soldering the rest of the board. @robrob has two grounding schemes shown for the 5F1; one shows the Power Tube cathode resistor/cap and everything "south" of the input jack grounded to the power rail; the other, shows the entire preamp circuit grounded at the same rail as the rest of the preamp section. I was just kind of blindly following the first scheme listed but now not sure that makes sense.
Hee's ground scheme #1:
Which actually makes more sense to me...
BTW, I don't know how to put, like circles and such on graphics yet (PowerPoint, perhaps?) but the place to look is R6, V1B cathode resistor.
I know both would work but I'd think separating the preamp section entirely from the power section makes the most sense--and noise-"free" operation to me.
Glad to hear the procedure went well.
Is there a problem you're still trying to solve at this point or just looking for improvements?
This is my favorite software for basic editing if you want to try drawing circles. It's a more advanced version of the old school Paint program:
Is there ever a good day with a colonoscopy? I guess one where everything looks as it should.
Paint dot Net (Paint.Net) is fantastic and free. GIMP is, too. Both require a learning curve, though, and are more like Photoshop than the old MS Paint.
Paint still comes stock on Windows, and is easy as pie to do simple shapes and texts over pics and the like. @robrob's pics are PNG. No problem to add shapes and texts with Paint.
EDIT: sorry for the $hitpost. I'll go away now.
Scheme #1 is a more true preamp / power amp split grounding scheme. If you follow the signal path, C2 is the .02uf coupling cap that transitions from the preamp and power amp. R9 is the 6V6 grid leak. R8 and C6 are the 6V6 cathode components. That's your power section. Grounding it over by the power section ground joins those components with their corresponding filter caps C3 and C4.
Scheme #2 looks more like grounding to the closest and most convenient location in terms of proximity. Kind of a lazy choice that may sacrifice 'most optimal grounding technique' in an academic sense.
All that said I've heard and built many fairly quiet guitar amps using sub optimal techniques. Guitar amps are very forgiving in this sense. Leo's old designs aren't really 'academically correct' in many ways. The stratocaster has ground loops in how the back of the pots are wired. In most of the amp designs things like input jacks, output jacks, and pots aren't isolated from the chassis producing a double ground possibly creating a loop. Using an eyelet board and spacing tubes the way he did creates fairly long runs from the input jack to V1A's grid with no use of shielded wire. The technique you use for filament wires can be very impactful as well, and if they're center tapped.
I don't think it is wrong or bad to try and optimize your grounding scheme. Just know that it is one variable among many.
So, yeah, the problem is the two different grounding methods...although I've pretty much made up my mind to go with GM 2, above.
Thanks. I was wondering if the power tube should be joined into the power rail. That was the path that I was going down first when I saw that additional grounding scheme and thought..."wait a minute..."
Again, my first build; just trying to dot all my i's and cross all my t's. And, as I said above, each method should work. And you are probably right too that Leo was NOT particularly careful in his grounding scheme and it worked anyway
Wha...? Come back!
Oh jeez, that one went right over my head LOL
Must be the anesthetic
I used Paint to graffiti robrob's pic to show how easy Paint is to use. It was unnecessary and kinda bad taste. I deleted it. Didn't write anything offensive, though. Just really off topic and silly.
America. Let's see, in Minnesota units, 1mm = 0.0007952 rods, 0.0001988 chains, or 0.00001988 furlongs.... ;-)
Sent from my iPad using Tapatalk
I love "the rod" as a unit of measure. Seems like we only used it when putting up barbed wire fencing...
I've been down for a while and just started getting back into this in the last couple of days; already, I've got a problem that I can't figure out but hope you guys already know the answer.
So, I'm trying to check my work as i go, making sure that I have continuity where I should and making sure that my circuit "sees" resistors in their path, etc. Everything is fine so far, except...
I can't "see" my 22uF axial capacitors in-circuit. I can see the polypropylene orange drop caps in-circuit just fine, but the axial capacitors in-circuit (the by pass caps) show nothing. I've attached directly to the leads and still no capacitance. Then, I took one of them out of circuit and--22uF, just as advertised.
No power yet. Just a plain jane circuit board. Does anyone know what gives? Are these caps bad? Am I misinterpreting something? I'm ready to move on but this has me stymied.
The upper grounding scheme is optimal. Believe it or not the lower is pretty much the original Fender layout:
Look at the bypass caps in circuit. Even if you clip right to their leads, do you see another way 'around' them that lacks capacitance? A resistor maybe?
You can't necessarily measure either R or C in an RC circuit. Luckily, most caps are labeled....
EDIT: I meant to say I don't actually know any electronic theory, am making this up from my experience, so stand ready to be corrected...
So, yeah. Never really thought of it that way. Interesting, though...when on OHMS can see the resistor plain as day--and the right value too. Must be that the resistor is path of "least resistance" for small current to flow.