Champ 12 mod thread - DEMO ADDED on page 1

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Will
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Champ 12 mod thread - DEMO ADDED on page 1

Post by Will »

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ALL YOUR BASE ARE BELONG TO US

I've got it working for now - good enough to play around with. The power tube socket is damaged and has been arcing - replacement is on its way. The 1st input jack is intermittent; still have to figure out the best way to replace it. The channel switching also seems screwy - when the overdrive is on, it cranks up the distortion but the volume and gain controls don't seem to do anything. Probably an issue with one of the optocouplers. Besides that, it seems alright. I'm gonna do a few extra things to it - add a midrange control, external circuit breaker, amp fan, new reverb tank, proper lead dress, new filter caps, new speaker, etc.

Should be pretty cool once I play with the circuit a bit. Stay Tuned...
Last edited by Will on Sun Sep 21, 2008 6:10 am, edited 2 times in total.
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Post by robroe »

god get rid of those ugly fucking knobs


tinker around with it after you replace those ugly fucking knobs
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Post by robroe »

always wanted a practice amp with TAPE IN jacks. just seems like you could crank the mids on it and make any recording sound like its coming over AM radio. it would be so much fun to drive hilary crazy with
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Post by Will »

robroe wrote:god get rid of those ugly fucking knobs


tinker around with it after you replace those ugly fucking knobs
Never. I don't mind if my amp is a little ugly - keeps people from stealing it. Between this and the Princeton Chorus, I've got a little tower of REB KNOB POWER.

I'm looking forward to the next concert - I'm gonna link the 2 amps together and blast them from either side of the stage.
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Post by Sloan »

i used to have a p-chorus with the commie knobs too. was kool.
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Post by robroe »

what is 1 volt line out mean?

is that like a "warm" pre amp out type a thing?

like you could plug a record player using the tape in and then run a line out the 1 volt thing hot to a set of speakers?
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Post by Will »

robroe wrote:what is 1 volt line out mean?

is that like a "warm" pre amp out type a thing?

like you could plug a record player using the tape in and then run a line out the 1 volt thing hot to a set of speakers?
I have no idea - the Tape In allows a signal to be patched in after the tone stack. It looks like it then gets buffered by half of a 12AX7 and then amplified by the 6L6. The line out is an attenuated signal taken after the power transformer - sort of like if you plugged the speaker out of you amp into a Power Brake or THD Hotplate. Except in the Champ the attenuation is just done with a couple resistors, so it probably doesn't sound too great. I think the "1 volt" thing is just the maximum output level. I haven't tried it cause it seems like it would be hard on the OT and generate a lot of heat inside the chassis.

I've got a few impressions after playing with this for the last few hours. First, it sounds exactly like a Champ. I think a lot of the players who've given it bad reviews think that just because it has a 6L6, 12" speaker, and reverb it's like a Deluxe or mini-Twin. It's not - it's a small, punchy, plunky Champ sound. Second, it's extremely clear sounding, especially in the bass. There's no way to hit a low note and get a big, powerful rumble. It sort of reminds me of the way a Dobro sounds - totally twangy. Third, it negates the reason most people buy Champs. There is absolutely no way to get distortion at any sort of reasonable volume unless you use the OD channel, which sounds shitty (although it is broken, so who knows). Finally, it's loud as fuck for its size. It's not gonna be a late-night practice amp for me.
I'm really warming up to the sound overall. It's a big departure from my normal wide-and-clean 60s tone, more in the early 50s rockabilly camp. Very nice - it'll be interesting to see how it works for the next band practice.
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Post by mezzio13 »

Dude, I'm glad it went to a new home!!!! Your observations are about what I felt from years of playing it. I bought it new as soon as they came out to use as a stage slave so I could hear myself over my Carvin and the monitor mix. It was perfect for that as well. Glad you like it!

Btw, Dou is a stand up trader, for anyone who may do buisness with him in the future.
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Post by Will »

Alright - mod #1. Like the black and silver champs, there's a full 3-band tonestack lurking inside this amp - the midrange control is just set by a fixed resistor. Unfortunately, it's set with its value at "10". Decreasing this resistor to the Deluxe's value has the effect of rolling the mids back about halfway. Not as sleek as a knob, but there's no extra space in this chassis to put a knob where it wouldn't pick up noise or look weird. Since I might want to change this value in the future, I put the resistor on the outer side of the board so I don't have to disassemble the whole thing.
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Sounds a bit better now - less honky and much clearer. The cranked tone is a little better as well. More to come...
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Post by James »

Put a trim pot on there, it won't be easy access but you can change it much easier than a fixed resistor.
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Post by mezzio13 »

Fuck, I'm really hyped about this thread. This kicks total ass!!!
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Post by Ninja Mike 808 »

James wrote:Put a trim pot on there, it won't be easy access but you can change it much easier than a fixed resistor.
trims are good, but delicate, I've heard... Some times people have been too rough or too constant with them that the plastic part you turn falls off... I know of some heavy duty ones, but everything has a limit I would assume.
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Post by Will »

I didn't do a trim pot because I want to discourage fiddling. If I know I can tweak it too easily, I'll be taking it apart every day.
I'm putting together my Weber order tonight - new speaker, circuit breaker, tube sockets, vibration dampeners for the pre tubes, jacks for the speaker connection, input jack, and whatever else strikes my fancy
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Post by Will »

New mods tonight - nothing major, just little stuff:
1. Back plate was missing so I cut a new one out of plywood and sprayed it black - looks OK and does the job.
2. New plugs/jacks for the speaker and footswitch - both of these had integral wires running from inside the chassis. I did 1/4" plugs and jacks so if I ever get something like a Leslie or need more speakers I can just plug 'em in.
3. New input jack - old plastic one was intermittent, just stuck in a metal Switchcraft jobber.
4. New preamp tube - JAN Philips in the V1 slot (V2 is the overdrive channel I'm not using). Seems to make some difference, maybe just placebo. There's maybe a hint more grind when playing hard.

edit: HOLY SHIT - the last time I looked at JAN Philips tubes they were around $15, now they're over $50. FUCK. I think I have another one lying around (really hope I didn't leave it in that Kustom amp I sold...).

I ordered a Weber Alnico 12S which should be here next Monday or Tuesday - I'll do a demo once it's installed.
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Post by Will »

DEMO TIME!!!!
[youtube][/youtube]
Took a while - I wanted to give the speaker a few days to break in. I just did this long-ass no-talking-allowed demo with 3 different guitars - took FOREVER. I used all 3 positions of my Mustang (including a little jazz on the neck), some Cat Power with my U1, and some Hendrix with a 335. I think it turned out rather well, if a bit over-long. If nothing else, it shows that this isn't the crappy amp the Gear Page hounds would have you believe it is.

The speaker is really nice - it brought out a lot of sparkle and attack. Lost a little volume, but it seems to cut better. It also knocked about 5lbs off the weight, so I can't complain there. It's not the most versatile of speakers, but for me it's quite nice. I really like this for rehearsals and grab-and-go stuff now. A very nice little amp.

Thanks Mezz!
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Post by Ninja Mike 808 »

Great demo.
If you think of god as a pair of pants, a spiritualist thinks he needs pants, in fact he wants pants but none of the conventional types of pants seem to fit just right, so he makes his own pants and is happy that his knees are no longer cold.-fibus