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Post by rockin57 on Sept 27, 2012 4:15:16 GMT -7
Hi folks. I have two questions to ask. Should i mismatched the connection between airbrake-vs-marshall jcm800 (1995) as suggested on the instruction manual?(output 8ohm trough 16ohm cab or 4ohm output in a 8ohm cab) I mean this setup is valid also for modern or relative modern amps? Cause on manual is reported " vintage 100 watt Marshall". That mean for old 60's-70's or 80's amps or is valid also for today amps like JTM45 reissue,1987x and other?
The other question is, what can i do to connect a Z-Wreck into a couple of cabs?
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Post by Mark (Basement Enthusiast) on Sept 27, 2012 7:42:01 GMT -7
Check through this thread here: ztalk.proboards.com/index.cgi?board=brakelite&action=display&thread=49422...and especially the link therein, here: www.thegearpage.net/board/showthread.php?t=327189Data seems to show that, with the Air Brake, your amp more or less "sees" a load somewhere above 8 ohms (but less than 16 ohms) under almost all circumstances— as long as it's attenuating, and not switched to bypass. This does seem to back up what the Dr. says about mis-matching cabs on purpose... probably moreso for older amps because he doesn't want to be responsible for anyone blowing a vintage transformer. Basically, what I'm saying is that yes I'd mis-match (i.e. plug the Air Brake into the 8-ohm tap when using a 16-ohm cab) even if it's not a vintage amp... I don't really see how it could hurt.
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Post by Mark (Basement Enthusiast) on Sept 27, 2012 7:44:17 GMT -7
...and to answer your second question: Check with Pro Cables 'n' Sound. They can make you a special speaker-cable that'll let you connect 2 speaker cabs out of 1 jack on the amp (either parallel or series.. your choice). Lots of guys around here use 'em and they work great.
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Post by rockin57 on Sept 27, 2012 10:49:37 GMT -7
Thanks Mark.. So when i'll have the cable i should plug it from a 4ohm output into a couple of 8ohm cabs or from 8ohm into a pair of 16ohm cabs. It's correct? Any contraindications?
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Post by Mark (Basement Enthusiast) on Sept 28, 2012 7:10:12 GMT -7
Thanks Mark.. So when i'll have the cable i should plug it from a 4ohm output into a couple of 8ohm cabs or from 8ohm into a pair of 16ohm cabs. It's correct? Any contraindications? Well, I think you could go either way... and, for the most part, with either 2x8ohm cabs in parallel (4 ohm speaker load) or 2x16 ohm cabs (8 ohm speaker load) you'd still probably want to use the 8 ohm tap on the amplifier, given that the Air Brake 'shows' just over 8 ohms to the amplifier on almost all settings. From Mr. Aiken's chart in the TGP thread (linked above), here is what I've calculated as the "effective load" that the amp sees with various speaker cabs & settings of the Air Brake: Actual Speaker Load | 0 (bypassed) | 1 | 2 | 3 | 4 | 16 ohm | 16.0 ohm | 10.3 ohm | 10.7 ohm | 11.1 ohm | 11.3 ohm | 8 ohm | 8.0 ohm | 7.9 ohm | 9.0 ohm | 10.2 ohm | 11.5 ohm | 4 ohm | 4.0 ohm | 8.0 ohm | 11.2 ohm | 14 ohm | 17 ohm |
(Keep in mind, this is for the Air Brake; the Brake Lite's numbers are shifted just a tad.) So you can see above, with the exception of setting #4 of the Airbrake into a 4 ohm speaker load (either 2x8 ohm cabs, or 1x4 ohm cab, it's all the same) that the amp will pretty much "see" roughly between 8~14 ohms, which is why I'd say use the 8 ohm amplifier output (exception: use the amp's 16 ohm tap with a 4 ohm load on setting #4). I think this seems to explain the Doc's vintage-amp suggestion, as well. You dig? Anybody else interpret those numbers any differently? Pretty sure I got it right, provided Randall Aiken's numbers are accurate. Though, I'd love to hear the Doc comment on this.
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Post by benttop (Steve) on Sept 28, 2012 8:48:39 GMT -7
Nice diagram Mark. Mind if I capture that for my datasheet? It comes up over and over....
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Post by Mark (Basement Enthusiast) on Sept 28, 2012 9:42:45 GMT -7
Nice diagram Mark. Mind if I capture that for my datasheet? It comes up over and over.... Actually, I've got it drawn up in a spreadsheet a little nicer... I'll see if I can send it over to ya' that way, and then you can use whatever format you want on your spec sheet.
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Post by benttop (Steve) on Sept 28, 2012 9:45:07 GMT -7
Nice diagram Mark. Mind if I capture that for my datasheet? It comes up over and over.... Actually, I've got it drawn up in a spreadsheet a little nicer... I'll see if I can send it over to ya' that way, and then you can use whatever format you want on your spec sheet. Ah, cool! Thanks.
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Post by rockin57 on Sept 28, 2012 14:44:54 GMT -7
Thanks Mark you've read my mind!
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Post by Mark (Basement Enthusiast) on Sept 28, 2012 19:21:03 GMT -7
Props to doveman, too, for bringing this to light sometime earlier this summer (see my link to that thread, up top). In case anyone's wondering, here's my numbers for the Brake Lite (and BL-SA) as well: Actual Speaker Load | 0 (bypassed) | 1 | 2 | 3 | 4 | 16 ohm | 16.0 ohm | 10.1 ohm | 10.7 ohm | 11.3 ohm | 12.0 ohm | 8 ohm | 8.0 ohm | 7.2 ohm | 9.0 ohm | 11.2 ohm | 13.4 ohm | 4 ohm | 4.0 ohm | 6.4 ohm | 11.5 ohm | 16.4 ohm | 21.3 ohm |
I've forwared a prettier, color-coded version to benttop (Steve); perhaps soon y'all will see it in a more permanent location among his fantastically-complete spec sheets.
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Post by dreamlander on Jun 3, 2016 16:08:31 GMT -7
Thanks Mark.. So when i'll have the cable i should plug it from a 4ohm output into a couple of 8ohm cabs or from 8ohm into a pair of 16ohm cabs. It's correct? Any contraindications? Well, I think you could go either way... and, for the most part, with either 2x8ohm cabs in parallel (4 ohm speaker load) or 2x16 ohm cabs (8 ohm speaker load) you'd still probably want to use the 8 ohm tap on the amplifier, given that the Air Brake 'shows' just over 8 ohms to the amplifier on almost all settings. From Mr. Aiken's chart in the TGP thread (linked above), here is what I've calculated as the "effective load" that the amp sees with various speaker cabs & settings of the Air Brake: Actual Speaker Load | 0 (bypassed) | 1 | 2 | 3 | 4 | 16 ohm | 16.0 ohm | 10.3 ohm | 10.7 ohm | 11.1 ohm | 11.3 ohm | 8 ohm | 8.0 ohm | 7.9 ohm | 9.0 ohm | 10.2 ohm | 11.5 ohm | 4 ohm | 4.0 ohm | 8.0 ohm | 11.2 ohm | 14 ohm | 17 ohm |
(Keep in mind, this is for the Air Brake; the Brake Lite's numbers are shifted just a tad.) So you can see above, with the exception of setting #4 of the Airbrake into a 4 ohm speaker load (either 2x8 ohm cabs, or 1x4 ohm cab, it's all the same) that the amp will pretty much "see" roughly between 8~14 ohms, which is why I'd say use the 8 ohm amplifier output (exception: use the amp's 16 ohm tap with a 4 ohm load on setting #4). I think this seems to explain the Doc's vintage-amp suggestion, as well. You dig? Anybody else interpret those numbers any differently? Pretty sure I got it right, provided Randall Aiken's numbers are accurate. Though, I'd love to hear the Doc comment on this. This chart should be a sticky. I was researching attenuators and was really getting confused by the ohm loads the Air Brake creates with different ohm speakers. This is very simple and clear. Thanks
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