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Another Amp Question -- Modding a Champ


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So, I'm upgrading my little Fender Champ 600, and I wanted some opinions. There are not a lot of 6" amp speakers on the market; in fact, I've only found them offered from Jensen and Weber. Has anyone had experience with these? Any preferences? Should I just stick with the stock speaker?

 

The first thing I did upon getting the amp was to change out the crappy Chinese 12AX7 tube -- it was microphonic on arrival and rattled at several frequencies. Luckily, I had a couple of decent 12AX7's laying around. I may change out the power tube, too, but it sounds good for now. It's actually an electro-harmonix tube (not sure why they used a generic Chinese tube for the 12AX7 but a better name-brand tube for the power tube -- better then having two crappy generics, though). Any thoughts? I'm leaning toward sticking with the EH tube for now, partially because it seems to be almost impossible to buy just one 6v6 tube instead of a matched set and also because the current tube appear to be of fairly good quality.

 

Even with the initial rattle problem (which is apparently very common with the 12AX7 on the Champ), it's been a great recording amp. It has a great tone and breaks up easily at the lower volumes I'm looking for.

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Speakers:

Jensen for six inchers but make sure you match the amp load, right?

 

Tubes:

Go here and drool...in that amp, the right tube makes all the difference...and make sure you checkout the FAQ on that site...because of demand form amp manufacturers and corporate inbreeding from procurement of patents and tradenames, many tubes and namebrands are way different than in the even the recent past...

 

http://www.vacuumtube.com/guitartubes.htm

 

 

 

 

oops, now im prolly gonna spend some money

 

 

 

 

 

 

j

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I've had really good experience with Weber speakers. I got an 8" there, an 8A125, for my blackface champ.

 

I'd also recommend the Tung Sol reissue tubes for the 12AX7 and the 6V6. There's also a Russian made Mullard reissue for the 12AX7 that is supposed to be good too, but I haven't tried one yet.

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Afraid im not much of a fan of those particular tubes, Tung-Sols are not made by that manufacturer anymore, new company that bought the rights to the name...Same with the mullards mentioned, except it is common for the new russian owners to spend more on the re-packaging of random, old surplus tubes and claim they are manufactured to the design specs for the mullards, clearly a scam...JJs are better in that price range...

 

I think NOS tubes (like RCA, GE/Sylvania), would be more of a value...in most cases they will perform better and far longer, and while you could pay up to $50 for a single 6V6 tube, the results would be far beyond the run of the mill russian or chinese...

 

 

 

j

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Afraid im not much of a fan of those particular tubes, Tung-Sols are not made by that manufacturer anymore, new company that bought the rights to the name...Same with the mullards mentioned, except it is common for the new russian owners to spend more on the re-packaging of random, old surplus tubes and claim they are manufactured to the design specs for the mullards, clearly a scam...JJs are better in that price range...

 

I think NOS tubes (like RCA, GE/Sylvania), would be more of a value...in most cases they will perform better and far longer, and while you could pay up to $50 for a single 6V6 tube, the results would be far beyond the run of the mill russian or chinese...

 

 

 

j

 

 

I like NOS tubes too, but I think an RCA blackplate (@ $75 a piece) might be a little overkill for a $200 amp and a 6" speaker.

 

The Tung Sol 6V6 reissues are $15 a piece vs. $50 for a NOS tube and, I think, are superior to the EH, Groove Tube and Sovtek lines. I haven't tried the JJ's, but hear lots of people like them.

 

If you do go NOS, look out for scams. Ebay is pretty risky. There is a lot of relabeling going on. I really like this guy: KCA NOS. But it's sure easy to spend a lot.

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I like NOS tubes too, but I think an RCA blackplate (@ $75 a piece) might be a little overkill for a $200 amp and a 6" speaker.

 

The Tung Sol 6V6 reissues are $15 a piece vs. $50 for a NOS tube and, I think, are superior to the EH, Groove Tube and Sovtek lines. I haven't tried the JJ's, but hear lots of people like them.

 

If you do go NOS, look out for scams. Ebay is pretty risky. There is a lot of relabeling going on. I really like this guy: KCA NOS. But it's sure easy to spend a lot.

 

There are plenty of options under $50 a piece for NOS, but your point is well taken...i sort of got the feeling the champ was vintage or something more than a cheap amp, and worth the investment, but either way, the retube will make a huge impact on the sound...for my 65 Deluxe Reverb ri a complete retube with NOS could be as much as $300, but thats $300 that over the course of a lucky 2 year life span is $12.50 a month, and pays itself off with tone and string response...

 

The scam issue with NOS tubes, on ebay especially, was something i was trying to touch on without going to far in the explanation...its a shame when the tube companies themselves are as bad as the everyday scum that profit from fraud...self education can be a wonderous thing...

 

If someone knows of a board or site where people leave reviews and purchase details on tubes in general, id sure be interested...

 

also, glad to hear about the webers, never tried them...

 

 

j

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One other thing while im thinking about it...for those of us with the pleasure (or disadvantage, depending) of having 6V6 tubes, the options are significantly more limited, as the plate voltages vary in amps using 6V6s. some tubes dont perform in some amps...prime example: Fender Deluxe Reverb, >450volts at the plate, meaning that the tubes have to be rated that high to handle it, and even so, youll burn though tubes much faster than in some amps...

 

not sure on the champ however, so its in your best interest wheeldwagon to inquire about this when purchasing your tubes...

 

 

 

j

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I like NOS tubes too, but I think an RCA blackplate (@ $75 a piece) might be a little overkill for a $200 amp and a 6" speaker.

 

That was my original thought -- why spend much of anything on an inexpensive amp? Then again, this amp has become my primary recording amp. I don't really play out much anymore, so that makes it pretty much my primary amp (for the time being -- one day I might get a little boutique recording amp). So, I'm starting to think that for a small investment I can really get a lot out of this amp. As I noted, I've already been surprised at how good it sounds as is -- I bet I can get this baby to sound like a much more expensive amp. So, while I may not shell out for an RCA blackplate, I may investigate a good NOS tube.

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This is my first time doing more to an amp than changing out the tubes, so thank you all for putting up with my stupid questions. That said, how big a difference is there between a ceramic speaker and a AlNiCo speaker? Is it an issue of quality (I've noticed AlNiCo's are typically more expensive) or do they each have potentially desirable sonic qualities? Weber actually sells both in the 6" size (intended primarily for the Champ), and the ceramic is pretty reasonably priced ($24). Does the material used in the speaker affect the voume at which it breaks up?

 

I've noted above that I don't mind putting a little money into the amp, but I would find it hard to justify putting in a single tube that is more expensive than the amp. If you think about, the lower price actually justifies spending a little more on upgrades (like getting a good deal on a car but having to put new tires on it), but if you go too far, it's like spending $20,000 on rims, hydraulics, and stereo equipment for a $2,000 car. Anyway, I think the basic electronics of the amp are solid, and thus it makes sense to upgrade the tubes and speakers within reason (if only I had the skill to convert it to tube rectification). So basically, I don't want to use anything that's so cheap that it's barely an improvement, but I don't want to put pearls on a pig, if you will.

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Ok you crack me up....certainly not stupid questions

 

First question on ceramic vs alnico....same as how ceramic compares to alnico in pickup magnets...exactly the same physics...its a taste issue and im really not sure how to classify...its a feel thing...the real issue with break up is a combo of ampage vs material, and the coil assembly prolly has much to do with it as the magnet...and the reality is that with 6 inches, theres only so much you can expect ( applies to women as well)...

 

OK tire analogy is good...think about driving a new car with a heathy V6 with shitty worn tires...no traction, wheels spin when you floor it...string response is the accelerator

A tube takes the signal directed to it and in theory amplifies it and adds character to it...a shitty tube can spin the wheels fine but wont grip the pavement or respond to the texture of the road, a better car analogy would be adding a nitrous tank to a carb..im not advising a hundred dollar investment on a single tube...but in a way you are talking about pearling a pig...outside of re capping and adding point to point on that shit, the retubing is the single most important change you can make on that amp...

 

experimentation is the key...after reading your posts, you are obviously looking for the strongest performance from that amp, well you should...its going to take some playing around to get to 'boutique' status...

 

happy to help

 

 

j

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Yeah, I agree that you may not see much difference with a 6" speaker. Little hard to get bass response out of a speaker that small. Maybe you consider putting a speaker jack in and using an extension cab with a 10" or 12" speaker. I think 5 watts might be enough to drive the speaker and you'll get a better range of frequencies and probably a lot more volume. If you get a big enough cab, you can just set the champ on top like an amp head.

 

You need to be careful to get the impedance (ohms) of the speaker right. If the impedance of the speaker is too high, the amp will not be harmed, but won't perform as well. If it's too low (or if you neglect to plug in the speaker), you may fry your amp.

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I don't have any delusions that I'm going to get this amp up to boutique status (or at least the quality most perceive as boutique status -- I'm sure there are some "boutique" amps that are utter crap); I'm just trying to get the most out of it that I can. Honestly, I've been pretty happy with the sound I've been getting with it recording so far -- due mostly to the lower volume needed to get it into the "sweet spot."

 

As for the size/power of the amp, I don't see this as a drawback since the size and wattage were the exact reasons I bought it. I intentionally bought the lowest wattage tube amp I could find. I needed an amp that would break up at lower volumes, would be easy to record, wouldn't create problems with rattles, buzzes, vibrations, etc. in my "studio," and that wouldn't annoy the hell out of my wife on the other side of the house. My main amp (old Fender Bassman 4x10) was a problem in this regard and needed serious volume to perform as desired. While I am at the point in my life where I can afford to buy an expensive amp, I'm also at point in my life where I can't justify spending that money (to myself or to my wife) on the amp (instead of a new roof, lawnmower, living room furniture, etc.). Eighteen-year-old me would smack thirty-year-old me if he could look into the future and read that.

 

Does anyone here set the bias on their tubes themselves? Just curious as to how difficult it is. It sucks to dish out for good tubes and then have to pay a tech even more for setting the bias, but I'm not sure it's something I want to mess with.

 

Anyway, the three speakers I'm looking at all match up with the amp at 4 ohms. The amp is 5 watts, all three speakers are 15 watts. I'm not really worried about the smaller speakers lacking bass response -- as is, the amp is getting a pretty nice bass response (believe it or not). Anyway, it looks like I've found compatible replacement parts, so I'll leave ya'll alone and just do some experimenting.

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Does anyone here set the bias on their tubes themselves? Just curious as to how difficult it is. It sucks to dish out for good tubes and then have to pay a tech even more for setting the bias, but I'm not sure it's something I want to mess with.

 

If it's not an adjustable bias amp, I think you'll have to swap out the right resistor. Can't help you there.

 

 

Let us know how your experimentation went.

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People make much more out of this than need be...setting bias on a retube is extreme tweaking...the tubes and accompanying grid have built in tolerances...as long as youre within those, theres no reason to fret of biasing...in amps with no bias pot, you shouldnt have to worry about making a change, the amp design allows for discrepancys in tube tuning, and swpping out resistor makes no sense...youd need the proper tube tester and scope to rate the tubes and then set bias, but it is rare that the tube ratings are far enough out of the amps tolerances to warrant a substantial change...\

 

 

j

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People make much more out of this than need be...setting bias on a retube is extreme tweaking...the tubes and accompanying grid have built in tolerances...as long as youre within those, theres no reason to fret of biasing...in amps with no bias pot, you shouldnt have to worry about making a change, the amp design allows for discrepancys in tube tuning, and swpping out resistor makes no sense...youd need the proper tube tester and scope to rate the tubes and then set bias, but it is rare that the tube ratings are far enough out of the amps tolerances to warrant a substantial change...\

 

 

j

 

I've always suspected as much. Thanks.

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