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FDP Forum / Fender Amps: Vintage (before 1985) / Tubes For '64 BF Champ

jillfen

cuyahoga falls, OH

Mar 29th, 2019 07:19 PM   Edit   Profile  

Hello folks, My only tube amp is a 1964 BF Champ. Just put a Weber in to replace the tired Oxford and am breaking it in. Right now there's a Sovtek 12 AX7, a Sovtek 5Y3 and a Groove Tubes 6V6 which is branded Electro Harmonix, all Russian. Any suggestions for tubes which might increase volume, punchiness, tone, etc.? In other words, what tubes would improve it?

pcalu

usa Thumb area Mi

Mar 30th, 2019 07:04 AM   Edit   Profile  

IMO when looking at NOS tubes the power tubes are the one you really notice the difference between new and old.

Preamps, to my ears not so much. For example, I can't really tell the difference from a JJ5157 and an RCA 7025, no matter what vintage amp I tinkering with.

Like everything it's subjective, that said I use JJs in all my Fenders again its what my ears like best (besides NOS)

Peegoo
Contributing Member
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Just beyond Mars

there's a world of fools
Mar 30th, 2019 07:50 AM   Edit   Profile  

If you want to increase volume and punch, one really simple mod is to replace the 5Y3 tube with a solid-state rectifier.

A Weber Copper Cap rectifier is probably the best one to use because it's more than a simple diode bridge. It contains resistors that allow the tubes to slowly warm up (like a tube rectifier does), rather than smack the tubes with full voltage as soon as you hit the power switch. The added bonus is it plugs in just like the tube does.

How does diode rectification make an amp louder and more punchy, you ask? A tube rectifier requires its own power to generate current that drives the power tubes and output transformer. Diodes are a whole lot more efficient because less energy is lost to heat.

Since the solid-state rectifier draws a lot less power, the additional power "wasted" by a tube rectifier is now available for use by the power section (volume increase).

A diode rectifier also delivers current faster than a rectifier tube can; there's no power ramp-up time, and that makes the amp faster and more punchy.

In some amps, replacing a tube rectifier with solid state can reduce sag (depending on the power tubes you have in there), but that's the trade-off.

I've had a Copper Cap in my Princeton Reverb and one in my blackface Champ for years because the difference is that good.

I was first hipped to this approach many years ago by an article written by Cesar Diaz, who was Dylan's touring guitarist for years. He was an amp and effects pedal mad scientist, and was the amp go-to guy for many famous players. Stevie Vaughan asked him if he could make his touring Vibroverbs bigger and punchier, and he converted them to diode rectification.

I'm guessing Cesar took a cue from Jim Marshall, who used a Bassman-style circuit in his amps, but instead of a rectifier tube like Leo's design, he used a diode bridge.

I tried this in the Princeton and it did make a positive difference. Next I tried it in the '66 Champ. It made such an improvement in volume and punch that I used the Champ as my band rehearsal amp. It had no trouble keeping up with a full drum kit, another guitarist, a bassist, and a PA.

Check out the Weber Copper Cap. The WY3GT/WS1 is the replacement for a 5Y3 tube.

(This message was last edited by Peegoo at 09:53 AM, Mar 30th, 2019)

jillfen

cuyahoga falls, OH

Apr 1st, 2019 10:20 AM   Edit   Profile  

Peegoo,
Thanks for the suggestion. I checked with Weber and they are out of stock at the moment but hope to have some in next week. Is this just a straight switch? I'm quite ignorant technically amp-wise. They mentioned checking the bias and plate voltage to prevent overheating the power tube, which I have no idea how to do and wouldn't attempt anyway. Thanks.

(This message was last edited by jillfen at 12:11 AM, May 14th, 2019)

Peegoo
Contributing Member
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Just beyond Mars

there's a world of fools
Apr 1st, 2019 10:29 AM   Edit   Profile  

jillfen, it's a simple "remove the rectifier tube and plug in the Copper Cap" operation. Just like replacing a tube.

When you remove and replace tubes, be very gentle because if you rock the tube too much in the socket you can stress the socket's contacts (they use spring pressure) and that makes for a poor connection with the tube's pins. That leads to all kinds of bad stuff including noisy operation, lost bias, or no sound at all.

Far as checking the bias on the power tubes, that is a job for an amp tech. It requires using a meter and knowledge of safe practices when working inside a live amp. There are lethal voltages in there and a simple goof can be fatal.

(This message was last edited by Peegoo at 12:32 PM, Apr 1st, 2019)

jillfen

cuyahoga falls, OH

Apr 1st, 2019 10:32 AM   Edit   Profile  

Thanks Peegoo. That's the answer I was hoping for. That's as far as my technical proficiency goes as far as tube amps go. Glad to hear it and thanks again for your suggestion.

jillfen

cuyahoga falls, OH

May 13th, 2019 01:57 PM   Edit   Profile  

Peegoo, well it took awhile to get them back in stock but I finally got a Weber Copper Cap in my Champ. You weren't kidding. More punch, volume,...in other words, ballsier. Just what I was looking for. Thanks so much for the recommendation. For anyone else who's interested, it's a great mod.

pcalu

usa Thumb area Mi

May 13th, 2019 02:40 PM   Edit   Profile  

https://www.thegearpage.net/board/index.php?threads/weber-copper-cap-rectifiers-are-not-what-they-seem.11663/


Titled " Weber Copper Cap Rectifiers are not what they seem"


Some in the thread are claiming weber's caps sag more than a decent tube rectifier??

found that interesting


FDP Forum / Fender Amps: Vintage (before 1985) / Tubes For '64 BF Champ




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