#46
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#47
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The 59 and 60 Bassman apparently also differ ever so slightly from the official documentation in a couple of minor ways, just a couple of component values here and there. It's still an amazing amp when built to plan.
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"You don't have to be great to start, but you have to start to be great." -Zig Ziglar Acoustics 2013 Guild F30 Standard 2012 Yamaha LL16 2007 Seagull S12 1991 Yairi DY 50 Electrics Epiphone Les Paul Standard Fender Am. Standard Telecaster Gibson ES-335 Gibson Firebird |
#48
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Clint can you explain what that cap actually does? I mean, I think I know what a cap does but what does it physically do in that circuit to cause the overdrive?
Could it be that they eliminated it in later models to clean the amp up then? |
#49
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Second, it increases gain by stopping what's called cathode degeneration, which is basically a form of negative feedback. This roughly doubles the gain in that stage, which helps push the next stage and power tube harder. The amp still works, but you won't get to Joe Walsh or "Layla" levels of breakup without some assistance like humbuckers or a boost in front of the amp. All evidence points to his being an error on the documentation or basically an "oops". The previous model Champ, the 5E1, has it. The later blackface Champ, AA764, has it. Every late tweed Champ that techs I chat with have seen has it, and it may very well be a "Hey, I forgot something" change by the designers once production started. If you want to see what happens and if you like the change, you can clip one in or tack solder it in. Just watch polarity, it should be negative towards ground. If you like it, make it permanent. If not, pull it back out.
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"You don't have to be great to start, but you have to start to be great." -Zig Ziglar Acoustics 2013 Guild F30 Standard 2012 Yamaha LL16 2007 Seagull S12 1991 Yairi DY 50 Electrics Epiphone Les Paul Standard Fender Am. Standard Telecaster Gibson ES-335 Gibson Firebird |
#50
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#51
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Thanks clintj. That's great. I'm still trying to figure this stuff out. I did learn some things building this kit but basically it's just following a recipe and in the end you have a loaf of bread but you don't really understand how gluten works or why you should let the dough rise and so on.
What I would love to see is a video or explanation of an amp circuit that is described from the input all the way through but I've not found anything like that. I suppose I'd have to go take a class or something. But with the kit's basically solder this thing to that thing and this one to that one but no real explanation of why. But it's still VERY cool though. Mojo Tone has been known to be a bit sloppy with their layouts. I wonder though if the schematic actually had that cap in it? |
#52
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Also, most people on the TDPRI subforum for amp building rely on Rob's explanations, schematics, and wiring diagrams rather than just going by Mojotone or Stewmac instructions.
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Yamaha FS 800/Martin 0-18/1948 Stella H928/Guild M-20/Fender American Performer Telecaster |
#53
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#54
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I'm toying with the idea of putting my new 5F1 Champ build into a cabinet with a 12" speaker.
Has anyone done this or is it best to just leave it in the 8" cabinet? |
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Depending on the speaker it may get a bit boomy. The Champ circuit has fairly weak power supply filtering and no low end cut at all. I've played one as a head through a Marshall JCM800 series slant 4x12 and it was pretty impressive, though. Huge sounding combo. Worst you can do is not like it, right?
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"You don't have to be great to start, but you have to start to be great." -Zig Ziglar Acoustics 2013 Guild F30 Standard 2012 Yamaha LL16 2007 Seagull S12 1991 Yairi DY 50 Electrics Epiphone Les Paul Standard Fender Am. Standard Telecaster Gibson ES-335 Gibson Firebird |
#56
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[QUOTE=clintj;6599011]Depending on the speaker it may get a bit boomy. The Champ circuit has fairly weak power supply filtering and no low end cut at all. I've played one as a head through a Marshall JCM800 series slant 4x12 and it was pretty impressive, though. Huge sounding combo. Worst you can do is not like it, right?[/QUOTE]
I just ordered a Weber 4 ohm 12A125 speaker and a new cabinet to with it. We'll see. |
#57
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Once you've done the required reading you could probably mod the amp to better suit the 12" speaker
I keep meaning to try to build a 10" into my Epi VJ combo, it should just about fit with a couple of mods to the speaker chassis but I might just build a 110% copy of the cabinet to gain the extra space instead.
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Brian Eastwood Custom Acoustic (1981) Rob Aylward 'Petit Bouche' Selmer Style (2010) Emerald X7 OS Artisan (2014) Mountain D45 (mid '80s) Brian Eastwood ES175/L5 Gibson Les Paul Custom (1975) Brian Eastwood '61 Strat Bitsa Strat with P90s (my main electric) The Loar F5 Mandolin, Samick A4 Mandolin Epiphone Mandobird Brian Eastwood '51 P Bass NS Design Wav EUB Giordano EUB |
#58
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Changing speaker jack
EDIT...Disregard this question. I desoldered the old and put the new jack in today using the chassis as a ground and it works perfectly.
I just want to make sure I do this right. I want to change out the RCA speaker jack to a ¼" jack to be able to use different speakers a bit easier. On this one, there are 2 yellow wires going to the jack tip and the ground is provided through the chassis. Should I do the same for the ¼" witchcraft jack and just wire up the tip or do I need to add a ground wire to the new jack instead of using the chassis? Last edited by Bluside; 01-13-2021 at 12:31 PM. |
#59
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It seems to me that yes, you should wire it the same. The RCA jack is nothing but hot and ground as is your Switchcraft jack, no stereo switch or anything like that.
Maybe clintj will chime in, don't take my word on it But it does seem to make sense. |
#60
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http://ax84.rru.com/media/ax84_m35.pdf http://ax84.rru.com/p1.html The AX84 project was more Marshall inspired and they put the tonestack behind the second stage.
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