Ultra Champ Design Questions, Filter Caps, Rectifier, Vibro Controls

[JGK]

Hi all I'm new to the forum and have been looking at building a Ultra Champ as it seems everyone has raved about the design.  I am curious of some of the design specifications compared to a BF or SF Vibro Champ and if anyone has had any problems or explain these more in depth.   

1. Initial 33uf filter cap as opposed to recommend 20uf for a 5y3, also has any tried any other rectifier tube such as GZ34 or a 5UB?

2. Vibrato controls 50K C (what's the C stand for) 2M A as opposed to the 25K and 3M RA pots on the original?

3. I also was wondering about the small cap and what appears to be diodes on the rectifier tube what do they do?

Thanks JGK

[wyatt]

1. "Maximum Input Capacitor" varies according to plate impedance, etc.  In general, 33uF should be perfectly safe with a 5Y3, I wouldn't go higher myself, but some builders go as high as 47uF. Feel free to use a 20/22uF cap instead of you want a little looser feel.

Never use a 5U4G/B unless you know the PT can supply the required 3A's current. A 5V4 or 5R4 would be more ideal more less sag. But watch the B+ voltages.

2. C = reverse logarithmic.  I'm sure Nik adjusted it "to taste." None of his designs are supposed to be exact clones of any amp.

3. The diodes/cap are there in case the tube rectifier dies. It's one of those great ideas that everyone should incorporate (and many boutique makers are).

[JGK]

Thanks, all good info I'll have to do some additional research but I am looking for a low watt amp and even SF Vibro Champs are getting priced beyond reason. Thanks again JGK

[wyatt]

Thanks, all good info I'll have to do some additional research but I am looking for a low watt amp and even SF Vibro Champs are getting priced beyond reason. Thanks again JGK

I don't know, I can still find Vibro-Champs for $300. I couldn't build a Fender-equivalent quality clone for less than $600. Niks are $480 with head cabinet, with no attempt at Fender cosmetics or speaker. Now, I can do all the required TLC for an old amp myself, which helps, but still.

Not matter what ridiculous price someone may be asking, this is what VC's are selling for....

$299
http://www.ebay.com/itm/Vintage-Fender-Vibro-Champ-Amp-AA764-Tube-Amp-Pre-owned-/260903934129?pt=LH_DefaultDomain_0&hash=item3cbf1618b1

$282
http://www.ebay.com/itm/VINTAGE-FENDER-BRONCO-TUBE-AMP-VIBRO-CHAMP-AA764-GUITAR-AMPLIFIER-1960s-1970s-/260898740865?pt=LH_DefaultDomain_0&hash=item3cbec6da81

$299
http://www.ebay.com/itm/Vintage-1979-Fender-Vibro-Champ-/180760592265?pt=LH_DefaultDomain_0&hash=item2a162bbf89

Champs and Fender heads are a bargain on the used market, they cost less than the sum of their parts.

Think about it, here in the states, one can buy a real, stock, early-'60's 6G6/A/B Blonde Bassman with speaker cabinet for $1000.  No one can't match that price on a clone.

[JGK]

As far as the market goes Camps and VB are a fair deal I travel allot and you can find them for around 300.00 or so in stores that carry vintage type stuff. The silverface fenders are also a good deal but they still require some maintenance and overhaul work. I'm not a collector I'm just looking for something around 6=8 watts that I can crank also a class A type vib. I looked at some parts and I think I will just build it as I'd like to do a combo with a 12" speaker since I have quite a few laying around. I've built a Allen accomplice and a Trinity SIII both are a little loud to crank and I,ve got a original Super Champ which is nice amp. Plus its getting to be winter here and I need a project to stay busy with the next month or so. JGK

[wyatt]

My old-style Accomplice is my main amp (since I sold off a '60 Tweed Deluxe), absolutely great!