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Post subject: Supersonic Impedance and Bassman Hum!
Posted: Mon Mar 11, 2013 10:20 pm
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Hi
New to this board but have recently added to my Fender gear (via ebay).
That's unfortunately created a few problems and any advice would be appreciated - maybe this should be separate posts?
1. I got a Supersonic 100 head, and then decided "needed" the 4x12 cab that goes with it. After the seller shipped the cab he told me he had rewired it to 4 ohms (it's 16 ohm stock as far as I know). The head can be set to 4 ohms but I heard that can put a lot of stress on the amp. I'd be predictably unhappy if I damage something, especially the head. Or will it just be really loud (in which case I can just turn down). Other than to be really loud is there any benefit to rewiring to 4 ohm (in which case why does Fender set at 16 ohm)? Also, looking at the cabinet itself, how do you even get into the thing (you are correct - I'm not exactly an expert)
2. I also bought a used Bassman 59 Reissue. Unfortunately seller had left power tubes rolling around in bottom when, and when plugged in nothing. I replaced those (which he refunded) so it now works, but has quite loud low frequency hum. Oddly if you twiddle with both volume knobs (regardless of which jack you're plugged into) at about 9am on both it's almost gone away (it's louder when both at 0?). But as soon as turn either up (again regardless of where plugged in) it gets really pretty loud. Before I replace rest of tubes is this likely a tube problem or something else?

Thanks!


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Post subject: Re: Supersonic Impedance and Bassman Hum!
Posted: Tue Mar 12, 2013 12:07 am
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Everything loads from the front on those Supersonic cabs. The grill cloth is attached to a removable frame secured to the case via velcro. You'll need to carefully pull it off to access the speakers. To reconfigure the speaker array for 16-ohm system impedance, you'll be using a series-parallel arrangement.

Best of luck, HTH

Arjay

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Post subject: Re: Supersonic Impedance and Bassman Hum!
Posted: Tue Mar 12, 2013 1:27 am
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No guitar plug ;

If loud hum with volume at 0 this could be a filter capacitor problem or a defective/ broken solder in power supply.

If hum is more loud with more volume ; check all tubes . If you replace power output tubes with non matched tube this could make hum . Don't need perfectly matched tube but not more than 10 milliamp between them. You also need to check and adjust bias if needed. If you buy new good brand tubes there should be matched OK.


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Post subject: Re: Supersonic Impedance and Bassman Hum!
Posted: Tue Mar 12, 2013 7:42 pm
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Hi
Thanks to both Rock Icon and Rock Star
I figured you must have to access from front, but I think you need a delicate touch? Someone suggested a butter knife. Any thoughts on question about whether running at 4 ohm is a "good" or "bad" (or "whatever") thing

On the separate hum problem it definitely gets louder with volume (although has this odd thing of decreasing through quarter turn and then getting louder). So I'll try tubes first. The pair I got was matched set so I'll presume for moment that's not the issue

Thanks


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Post subject: Re: Supersonic Impedance and Bassman Hum!
Posted: Tue Mar 12, 2013 8:30 pm
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doogle wrote:
...Any thoughts on question about whether running at 4 ohm is a "good" or "bad" (or "whatever") thing...


Neither good nor bad, just a matter of taste. You can match the impedance of amp and speaker with the impedance switch. Some people prefer the sound at 4 ohms, some at 8 ohms, some at 16 ohms. IMO, you get the most from the amp when using all of the OT, which would be 16 ohms. Sometimes a slight impedance mismatch sounds better than matched. For example, 16 ohm setting on the amp with an 8 ohm speaker might sound better than with a 16 ohm speaker. Keep the impedance of amp and speaker either matched, or mismatched within a 2 to 1 ratio and you'll be fine.

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Post subject: Re: Supersonic Impedance and Bassman Hum!
Posted: Fri Mar 29, 2013 1:40 pm
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Been traveling and only now reviewing comments
Thanks for input on impedance question
I think I'm going to have it rewired back to 16 ohm, as that's apparently how Fender thought it sounded best


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