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Messages - mattilla

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The Newcomer's Forum / Re: Wiring 2 speakers for 4/8/16 ohms switchable?
« on: October 25, 2015, 12:48:44 AM »
My apologies for disappearing & not responding. Major computer troubles/internet connectivity troubles/life troubles... gah blow me up...

Thanks everybody for contributing to this thread. Too many delays, now I'm building this f$#%'en thing AT LAST!

Roly, if you are still around, can I just query you on this? --

what happens to the cab air loading on the driven speaker in the 8 ohm position where only one speaker is driven?   8|

I'm not too sure what you mean by this, and why it's a possible issue if only one speaker is being driven? Could you clarify? Thanks!

The Newcomer's Forum / Re: Wiring 2 speakers for 4/8/16 ohms switchable?
« on: September 07, 2015, 10:41:13 PM »
Thanks again, J M Fahey! I really appreciate your input - here & elsewhere on this forum. I do agree I am over-thinking this & the "phase" switching is probably over-the-top.

This might sound stupid,,, but Why?
Why do you need all 3 options?

Reasonable question. As J M Fahey says just after your post, I want "versatile" - something I can plug any kind of head into. My original plan was just to use the standard 4/16 switchable wiring scheme, but then I thought why not add the 8ohm option? That's when my brain fell into pieces, and I started babbling out loud on this thread. Sorry about that.  :-[

The Newcomer's Forum / Re: Wiring 2 speakers for 4/8/16 ohms switchable?
« on: September 06, 2015, 09:55:11 PM »
OK so I came up with this - each socket has it's own "phase" switch. Does this look ok do you think?

Combining the 2 phase switches into one master toggle switch is beyond my brain capacity.  :loco

The Newcomer's Forum / Re: Wiring 2 speakers for 4/8/16 ohms switchable?
« on: September 06, 2015, 07:27:16 PM »
OK lol, try again... Would this do the job? I made J2/socket #2 a switched socket, so that plugging into it effectively cuts the circuit to the other speaker altoghether (I think?)...

Any suggestions/advice at this stage more than welcome!!  :P

EDIT: Damn, why did I smoke so much weed as a kid? Looking at this, I'm already seeing that when I plug into Socket 2, the tip & sleeve of the socket are connected to the opposite speaker lugs as Socket 1. Does this matter? If only one speaker is being used, does it matter which way around it is connected? A speaker isn't "polarized" as such, is it? Obviously if using 2 speakers together you want them "in phase", but with one speaker only it should be ok? HELP!  :crazy2:

EDIT2: More over-thinking on this lol.... Hmm, how to incorporate a "phase" switch, so that  I have the option of reversing speaker polarity? Googling around, the verdict seems to be that if you're feeding the speaker a pure sine wave, polarity doesn't matter... but of course guitar & distortion etc is asymmetrical  & whether the speaker "pushes" or "pulls" can affect the sound/"presence" out the front of the cab... So, a "master switch" that can toggle the polarity of both speakers would be a good idea yes? After all, some amps/pedals invert the signal & some are non-ionverting, so having the option to toggle the speaker polarity would actually be very handy yes?

The Newcomer's Forum / Re: Wiring 2 speakers for 4/8/16 ohms switchable?
« on: September 06, 2015, 06:29:27 PM »
Thanks guys. Yes I think I have been "over-thinking" this lol.

J M Fahey, does this look right to you?

If "J1" is unplugged and "J2" is plugged in (for 8ohm single speaker), is there no "crosstalk" over into the other speaker at all? Does J2 need to be a switched socket or anything, or just the standard non-switched mono socket like J1 will do? (Am I over-thinking again? Lol)...

One other quick question, to keep the unused socket "sealed" so no air escapes (it will be closed-back cab), I believe there are "socket caps" I can use to seal the unusued socket?

Thanks again for your help.

EDIT: Hmm, see, I'm looking at this diagram, and I'm thinking, if S1 switch is "up" (for 4ohm parallel wiring), and J2 is plugged in, then Speaker 1 is effectively tied into the "loop", there is a closed circuit? If switch is "down" (for 16ohm series wiring) then Speaker 1 is in open circuit & effectively cut out. Hmm. This is doing my head in!  :duh

The Newcomer's Forum / Wiring 2 speakers for 4/8/16 ohms switchable?
« on: September 06, 2015, 06:05:47 AM »
Hi, please forgive this largish post, but I've been wracking my brains with this. I have 2 Jensen Mod speakers in a homemade cab, both rated 25W @ 8 ohms. What I would like is to be able to wire them up so that I can toggle between 4, 8 and 16 ohms. Obviously, 4 ohms would require the speakers to be in parallel, 16 ohms in series, and 8 ohms would just use one of the speakers directly. I know there are wiring diagrams around that already clearly explain how to wire up 2 x 8 ohm speakers for 4 and 16 ohms selectable output. But adding the extra 8 ohm option does my head in!  :duh

I've broken it down & I "think" I have arrived at a solution, but could some of you more knowledgeable amp techies please have a look?

Here are the 3  different wiring options (for 4, 8 & 16 ohms) --

And here's the solution (?) I came up with. I "think" it would work, however, it requires 2 toggle switches to route the signal path appropriately --

Here it is again with the 4, 8 & 16-ohm signal paths traced out in different colours to avoid (??) confusion of where I'm going with this ---

What I plan is a metal plate on the back of the cab with a couple of toggle switches and of course the mono input socket, something like this --

I "think" this is a viable solution, but to be honest I don't like the two toggle switches - it looks a bit awkward & ugly. Also you would have to be very careful to have the switches toggled correctly. But is this the only way to do this, do you think? Does anyone have any suggestions or ideas around this?

Thanks in advance.

You could flip that thing upside-down and build a metal chassis on the "bottom", screwed to the sides. Then just use two wooden planks for the front and back and voilá!
Simply drill a hole in the midde of the bottom (now your top) piece to run the wires for the speakers. That way you can have a better closed area for the speakers.

Thanks blackcorvo! Yes I plan to use the cab upside-down (as I mentioned in my first post heh)  ;) This unit is actually a perfect size for a couple of 8"s, solid pine too, and next-to-nothing costwise.

being surrounded on 3 sides by grounded metal is almost always enough, but if needed, you can glue to the wooden side closing your cabinet a sheet of kitchen type aluminum foil and ground it, a very common trick, used even by Fender and Marshall, go figure.

Ah thanks Mr Fahey! That's what I was wondering! Well, as it happens, I did find an enclosed 19" aluminium rack case online for a good price that will fit into the "top" section (actually "bottom") very nicely. Nice to know about the aluminium foil trick, thanks.

This is a labour of love that's been dragging along too long now, I'm gonna step it up a notch & post results when I can.

Thanks I'll look fr a 19" aluminium rack case then

This might seem a dumb question... I'm building a Tiny Giant amp into a simple cab (an upside down Ikea "Rast", see pic!), with a couple of Jensen Mod 8" speakers... The space at the top of the Rast is exactly 2RU 19" rack panel size. I can mount knobs etc onto the rack panel with the Tiny Giant PCB behind it... My question is, does the amp PCB require an aluminium enclosure to shield against RF/hum etc? In which case, can I still have wires coming out of the enclosure to connect with the pots & switch etc on the front rack panel?

My confusion comes from seeing some DIY amps fully enclosed, others half-enclosed, others not at all, etc etc...?

I hope I'm making sense here lol.

(Rast unit below - imagine it upside down!)

Amplifier Discussion / Re: FS Audio FG212DSP guitar combo??
« on: November 22, 2013, 08:56:30 AM »
Can't, different state.

Amplifier Discussion / FS Audio FG212DSP guitar combo??
« on: November 21, 2013, 10:16:14 PM »
Has anybody heard of this Chinese brand?

For a 250W combo it is very cheap!? Piece of *s!!t* you reckon?

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