cyclodan
61 posts
Mar 11, 2014
8:03 AM
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I have a lovely sounding '51 Gibson BR-6F that I would like to install a line out on. I am concerned that the dynamic speaker might present issues since it is part of the circuitry. Any vintage Gibson experts or amp techs have any advice? Does anyone know what the impedance is on the speaker in this amp?
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cyclodan
62 posts
Mar 12, 2014
10:02 AM
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"Bueller...anybody?"
Rick?
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Rick Davis
3061 posts
Mar 12, 2014
10:12 AM
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LOL. I agree that is a lovely sounding amp. But I don't know the answer. I didn't try putting a line out on my BR6. That field coil speaker just ain't the same.
If the techs here don't jump in I'll ask Bruce Collins. It is an interesting question.
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-Little Rick Davis
The Memphis Mini harp amp
The Blues Harp Amps Blog
The Mile High Blues Society
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cyclodan
63 posts
Mar 12, 2014
11:10 AM
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Thanks for the reply Rick. I had already been nosing around Bruce's blog looking for contact info but came up with nothing.
Edit:
Never mind, I guess I was looking at your blog, as a google search for Bruce also leads to your site. I'll look around the Mission amps site.
Last Edited by cyclodan on Mar 12, 2014 11:15 AM
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cyclodan
64 posts
Mar 12, 2014
2:58 PM
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Well I got some info from an amp forum. One guy said no problem but this is from Mark Norwine of Carlson Amplification Inc. in New Jersey...
"A field coil speaker has no bearing.
That said, most simple "tap-off-the-signal-with-a-divider" type line outs really don't sound very good. They sound particularly bad when the amp distorts.
To make a good sounding, useful line out requires a balanced signal, a transformer, and caps & inductors to simulate the characteristics of a speaker.
Cramming all of that into a BR6 will be tough, and besides: that looks like a really nice clean specimen ..... Please don't do it."
So that begs the question...does a simple line out from an amp really sound like your amp. I know of course that your amp's "sound" includes your speaker, but to those that use a line out from a small amp to the P.A. does Mark's warning have the ring of truth? What he says does seem to make sense.
Last Edited by cyclodan on Mar 12, 2014 3:01 PM
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Rick Davis
3062 posts
Mar 12, 2014
3:05 PM
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Simple speaker tap line outs sound fine. The reactance of the speaker influences the signal. It is not dry. Still not sure about the field coil speaker, though...
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-Little Rick Davis
The Memphis Mini harp amp
The Blues Harp Amps Blog
The Mile High Blues Society
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Barley Nectar
315 posts
Mar 12, 2014
3:31 PM
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Treat a line out circuit on a FC speaker the same as you would a PM speaker. The VC on a FC speaker functions the same as any other speaker. The FC of a FC speaker is merely an electromagnet that is used in place of the perminate magnet on modern speakers. The FC is usually used as a choke in these old amps. Rig up the voltage divider on the hot wire between the OT and speaker and try it.
I have researched line outs and have read that the method Mark Norwine refers to is said to be superior. Probably does not make a lot of difference in a live setting.
Don't mess up that amp and devalue it by drilling holes...BN
Last Edited by Barley Nectar on Mar 12, 2014 3:35 PM
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Rick Davis
3063 posts
Mar 12, 2014
4:12 PM
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Thanks Goose. Good info...
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-Little Rick Davis
The Memphis Mini harp amp
The Blues Harp Amps Blog
The Mile High Blues Society
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