CHAMP REVERB version 2 - built from scratch

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sookwinder
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CHAMP REVERB version 2 - built from scratch

Post by sookwinder » Fri May 07, 2010 9:44 pm

My previous inroads into the world that is known as Amp repair/Amp modification allowed me to create a Champ Reverb which I have to say sound fucking awesome (as Wordsworth would put it), especially when played through my 2x8" cab with vintage Jensens.

But there were a couple of issues / design flaws in what I eventually came up with as a design. As you can see if you added a sauce and some garlic bread it would look like the perfect Spaghetti main course at your local Italian restuarant.
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Over the past month or so my mind has been thinking of ways I could have made this modifiction "cleaner / better laid out"

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I received the 2x8 cab from MOJOTONE .... again excellent quality workmanship. I am most impressed with them so far.

I was also pleasantly surprised the the attachment screws for the speakers. (the cab I ordered was just a cab .. no wiring or speakers). Rather than the usual threaded rod which you fit the speaker over and then spend hours with a spanner to tighten a nut over it .... what mojo has fitted is a female threaded section in the baffle which I use a screw driver the lighten a threaded screw into it. Speakers where fitted in in less than 4 minutes. maybe I missed this new technology, but it is great.

The 2 1964 Jensen C8R speakers just blow away the 2 10" weber blue pups I have in my other cab.... I don't have a sound level meter to measure actual dB levels, but just by sitting infront and A-B ing each cab, the 2x8 jensens are louder, crisper, more articular and just rock !!! the blue dogs may have a touch louder bass... (given they're 10") ... but this maybe just a function of them sounding dull compared to the jensens

It was a little hard taking pics with the sun as it is, so I had them in the shade under a tree in the front garden.
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This is where I was at 3 or 4 weeks back. waiting for the Faceplate and backplate to be printed which would allow me to put the amp into the Champ head and everything would be finished. But then the project bug started eating into my brain.... it was somewhat problematic modifying an existing VC, given that all mods had to be done insitu, so could I build a Champ Reverb from the ground up, incorporating the "fixups" that I had been considering.

The redesign of the circuit is shown here... effectively I am now removing the total freakout feedback of the reverb signal, which I had in version 1 (moderated via a 1M resistor)
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I went straight to the internet and spent an hour or so seeing what was available at the various amp parts suppliers and pretty quickly realised that I could order all the parts needed to build up my own eyelet board for the amp components. In fact all one really needs is the fibreboard, some eyelets, your mother's or grandmother's "stamps" for putting press-studs onto clothes, a hammer and your there!

So I ordered a shit load of fibreboard , 1000 eyelets (enough to keep me going for a year or two) and while I waited for the parts to be shipped from the States, i went about and started to redesign the layout of the components.
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When one looks at the final design (or as final as anything really is) it looks pretty simple and easy to come up with, but I can tell you it took many evenings of just staring at the circuit diagram and trying to "discover" the cleanest layout to arrive at where I did. Obvious factors (which could not be followed when I did version one of Champ Reverb, modifying an existing VC) included trying to minimise lead lenghs, aligning eyelets close to where the valves are that will be connected and if there are multiple connections to a single point, try and reduce these. Also, where major connections occured on the fibreboard (400V from the Cap can or the main signal lead through to the 6V6) I ensured that these had their own eyelet ... essentailly to reduce clutter and make trouble shooting later one easier. I am sure they have PC programs to do this, but that would not have been as much fun.

What I came up with is:
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I also made the fibreboard half an inch taller than what is used in the Fender VC ... just to make things a little more spaced out.

Other items were ordered, PT, OT and reverb trannies, more electrical components, a shit load of solid core 18 and 22 AWG cloth covered wire. (and how good is solid core wire to work with in amps, compared to multicore).

Then again I started thinking .... never should start thinking ... I knew my nephew would love a Champ reverb head with a 2x8 Cab and I could teach him about building amps at the same time. Obviously I will be making my second CR, so I changed my mind about what I would do with version one of the CR. I will stick it back into the black VC cabinet it came from, once the faceplates arrive and fit a 4 ohm vintage Jensen C8R which I just happen to have lying around.

I will then use the version 2 of the CR which I am building currently with the Foam Green tolex head and 2x8 cab.

My nephew wanted the Champ head/2x8 cab to be "Electric Blue" coloured tolex. The guys at MOJOTONE managed to locate some tolex of that colour ... Fender had used it on a limited build of HRDs some years back.
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So let's recap ... building up version 2 of the CR which will now go into the FG head/cab. Ordering electric blue coloured head/cab for Daniel, so he can catch the amp bug. What next ? why not order another head/cab unit ... just because .... I can .. just because I already have the vintage jensens to go in it. (Picked up four 1961 C8Rs for a song on ebay). What reason do I need other than .. yeah I can.

So I asked MOJOTONE about what other colours of tolex they can get. I asked about Salmon coloured tolex. No. I asked about lemon (soft yellow lemon) coloured tolex . No. Iasked about Coral coloured tolex. No. I asked about any other soft pastel blue coloured tolex (other than "baby blue") No. In the end I went with Marshal style white tolex. I really wish Amp makers/parts suppliers realised that there is a whole spectrum of colours out there other than black, tweed or red. Remember only a real man can play with a soft pastel coloured tolexed amp. :D

Ordered (and received very quickly) some reverb tanks from Belton in Korea. Decided to get the 2 and the 3 second reverb time versions. Will choose later which I prefer.
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About this time the fibre board and the eyelets arrived and I went ahead to build up the eyeletboard ready for the compenents to be fitted to. initially I thought I could just measure along the fibrebaord, marking out as I went the location of each eyelet. Then using an electric drill, drill the holes. But as I discovered this method produces a finished product that isn't straight or aligned. Not what I was hoping for.
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So I went on a different tac .... I printed out (at work) the layout of the components in exact 1:1 sizing. Wrapped that piece of paper securely around the fibreboard I had cut to the desired size. Then using a centre punch, made indentations in the paper (and the fibreboard) of the eyelet locations. This process worked a lot better.
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Started to layout the components. Again went with the Sozo caps and the Jupiter coupling cap. The sound they make is superb,
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Pretty quickly all the componets were inplace. I had decided to utilise a few under the board hookup wires, to reduce the number of leads going from the fibreboard to the valves. (you can see these a bit later).
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During the build up I did realise that I should modify my layout (which will be done on subsequent builds) This just puts the start of the lead going to the valve closer and reduces the length of hookup wire.
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The finally the hookup wire connected. Now I must wait for the CHAMP chassis I am ordering from a supplier in Thailand to arrive. Can't wait to start on the next stage.
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Re: CHAMP REVERB version 2 - built from scratch

Post by jimboyogi » Fri May 07, 2010 9:57 pm

Looking fantastic David :w00t:

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Re: CHAMP REVERB version 2 - built from scratch

Post by Orang Goreng » Sat May 08, 2010 2:54 am

I'm really itching to try something like this one day. Last week all of a sudden I found I can in fact read schematics much better than I thought. I get it now, awesome. I'll attempt my first cap job today, yay :). (I'll make sure I'll leave a note for my relatives to confirm my demise on OSG if it goes wrong ;)).
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Re: CHAMP REVERB version 2 - built from scratch

Post by sookwinder » Sat May 08, 2010 3:10 am

Orang Goreng wrote: Last week all of a sudden I found I can in fact read schematics much better than I thought. I get it now, awesome.
yeah it's great when that happens ;D
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Re: CHAMP REVERB version 2 - built from scratch

Post by Orang Goreng » Sat May 08, 2010 3:16 am

Yeah, I'd been approaching it the wrong way. Quite stupid in retrospect. Looking at it like a set of modules and then following the flow of current in each module seems to be the trick. Everything becomes clear as day that way. The only thing I still need to develop a feel for are the actual component values.
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Re: CHAMP REVERB version 2 - built from scratch

Post by øøøøøøø » Sat May 08, 2010 7:03 am

This is awesome.

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Re: CHAMP REVERB version 2 - built from scratch

Post by øøøøøøø » Sat May 08, 2010 7:12 am

You might try your hand at tolexing yourself. Raw cabs are cheaper and there are lots of different tolexes available. Here's a lemon yellow:

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Here's one called "light blue bronco:"

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Re: CHAMP REVERB version 2 - built from scratch

Post by sookwinder » Sat May 08, 2010 4:54 pm

Brad ... I did find quite a few places on the net (in the USA) that had tolex-like material in colours that I liked. For example : http://www.garysupholstery.com/naugahyd ... fside.html" onclick="window.open(this.href);return false;

But when I mentioned this to MOJOTONE they said I must order the material myself and then have it shipped to MOJOTONE. Which to me is just all to hard given I'm in Oz. And what just amazes me is that I was willing to spend more $$$ to cover the time for MOJO to order the material themselves....

maybe you're correct ... next time I should try and cover a cab myself...
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Re: CHAMP REVERB version 2 - built from scratch

Post by øøøøøøø » Sat May 08, 2010 8:46 pm

If you start with a raw cab, it's actually not that hard. I came out with a pretty good result on my very first try.

The hardest part is removing the old tolex on a re-tolex job. Starting with a smooth-sanded raw cab is pretty straightforward. You should give it a go!

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Re: CHAMP REVERB version 2 - built from scratch

Post by Slow-Pop » Mon May 10, 2010 10:09 am

wow man, you've really started running with this amp stuff! Everything you do, always seems so thoughtful and cool. Hats off to you! 8)

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Re: CHAMP REVERB version 2 - built from scratch

Post by Jay » Mon May 10, 2010 11:35 am

In poker terms I believe this is what they call "all in." :D

Since we're really getting into "full custom" territory I'll make a few suggestion to improve the design in terms of flexibility. It might be a good idea at this point to consider using a star grounding scheme to eliminate the potential for ground loop hum. You may also want to consider making some modifications to the output circuit to make it flexible in terms of what tubes can be used there. Compared to the Vibro Champ, adding a big 5W screen grid resistor (you want it on the tube socket), up-specing the cathode cap/resistor to 100V/5W and moving a couple leads around sets the amp up for handling pretty much any octal tube you can throw at it. This of course is provided you have a PT beefy enough to handle any additional current draw requirements some tubes may have. You'll also have to choose a cathode bias resistor that splits the difference for a variety of tube types (or build in a switch that allows you to select a few values) and have an OT with multiple taps as the different tubes will create impedance mismatches that need to be accounted for by selecting a new output impedance. I have to say though, a champ running a 6L6 sounds amazing—just enough extra oomph and a little sweeter and punchier OD tone IMO.

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Re: CHAMP REVERB version 2 - built from scratch

Post by Jay » Mon May 10, 2010 11:38 am

sookwinder wrote:Brad ... I did find quite a few places on the net (in the USA) that had tolex-like material in colours that I liked. For example : http://www.garysupholstery.com/naugahyd ... fside.html" onclick="window.open(this.href);return false;

But when I mentioned this to MOJOTONE they said I must order the material myself and then have it shipped to MOJOTONE. Which to me is just all to hard given I'm in Oz. And what just amazes me is that I was willing to spend more $$$ to cover the time for MOJO to order the material themselves....

maybe you're correct ... next time I should try and cover a cab myself...
So why can't you buy direct from Gary's Upholstery? If it's just becuase they are a "b to b" distributor or something then I might be able to figure a way to work around that for you. I have a good friend in FL that runs an upholstery business.

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Re: CHAMP REVERB version 2 - built from scratch

Post by sookwinder » Mon May 10, 2010 4:04 pm

Jay, there is no problem actually buying from Gary's Upholstery... if I do go down the road of doing my own tolex I will, the issue was more that I was willing to pay more $$$ to have mojo order it directly rather than me be a middle man... (where problems always arise)... so it was just "to hard" to organise (I am also lazy) so i went with the marshal white tolex.
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Re: CHAMP REVERB version 2 - built from scratch

Post by tribi9 » Mon May 10, 2010 8:00 pm

I love this thread. Awesome project. I was just thinking about buying some blank boards and getting some eyelets as a finished board I want is about $25 and with that same amount I can get me all the supplies to make me a few "custom" ones as well.

That supplier in Thailand... How are his chassis prices?

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Re: CHAMP REVERB version 2 - built from scratch

Post by sookwinder » Mon May 10, 2010 9:22 pm

tribi9 wrote:That supplier in Thailand... How are his chassis prices?
Well I still haven't got prices yet .... he is just now finalising his first build of CHAMP chassis (not VC but Champs ... his rationale is that if you want to do a VC, all you need to do is drill the extra holes in the Champ chassis to get the VC .... which I tend to agree with)

He already sells PR, Bassman and other (larger) Fender Chassis which i have read superb reviews about on various sites. Pplus his prices are really low.

He also has the brass plates on them (where the pots are to be located.

As soon as I get prices/pics I shall put them up here. he sells off ebay, but i have just been communicating with him directly and have used PAYPAL. Very very niuce guy as well .... stay tuned.
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