Clueless on impedance selector switch

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Clueless on impedance selector switch

Postby Hiwatt5 on Mon Mar 25, 2013 12:27 am

I'm building the Two Stroke amp and I'm not sure which is the correct impedance switch to use. I'm want to be able to connect two speakers and select between a single speaker at 8 ohms and two speakers at 4 ohms.

I have a Carling SPDT grounding switch, but that doesn't look right. Can I use a heavy duty SPDT 3 (on/off/on) position switch? or do I need to order a DPDT?
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Re: Clueless on impedance selector switch

Postby pdf64 on Mon Mar 25, 2013 5:12 pm

An output transformer is very sensitive to open circuits on its secondary; putting a switch in there seems to be something that it would be beneficial to avoid, as it introduces more failure modes.
How about fitting 3 jack sockets, 1 for 8 ohms and 2 for 4 ohms?
That method gets a bit clunky with 4/8/16 ohms outputs, and the balance may be perceived to swing back in favour of a suitable switch.
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Re: Clueless on impedance selector switch

Postby Unit_1 on Mon Mar 25, 2013 6:29 pm

pdf64 wrote:An output transformer is very sensitive to open circuits on its secondary; putting a switch in there seems to be something that it would be beneficial to avoid, as it introduces more failure modes.
How about fitting 3 jack sockets, 1 for 8 ohms and 2 for 4 ohms?
That method gets a bit clunky with 4/8/16 ohms outputs, and the balance may be perceived to swing back in favour of a suitable switch.
Pete


yeah that's what mesa did on the nomad i own (and never use anymore)

gotta sell it when the market kicks back up. IF it ever kicks back up..... :POd:
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Re: Clueless on impedance selector switch

Postby Hiwatt5 on Mon Mar 25, 2013 6:52 pm

I don't think I can make another speaker jack fit. I barely got two in the 5f2 chassis I'm using. And it looks like I need to stay away from a 3 position toggle switch that would result in the OT seeing no speaker load in the center position...which would be bad.

Hate to have to pay shipping charges again just for one switch, but it seems I'll have to. Buying a kit would have been simpler for my first build, but I guess I'll know better next time. :)
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Re: Clueless on impedance selector switch

Postby Unit_1 on Tue Mar 26, 2013 4:46 am

Hiwatt5 wrote:I don't think I can make another speaker jack fit. I barely got two in the 5f2 chassis I'm using. And it looks like I need to stay away from a 3 position toggle switch that would result in the OT seeing no speaker load in the center position...which would be bad.

Hate to have to pay shipping charges again just for one switch, but it seems I'll have to. Buying a kit would have been simpler for my first build, but I guess I'll know better next time. :)


if you wire the output jacks in parallel then if you're only using one it will be 8 ohms. if you're using both it will be 4 ohms x 2

i think... since i've never tried it before, and i'm on my second glass of burgandy :mrgreen:

any one else wanna chime in here?
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