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Discussion Starter · #1 ·
Hey all. I've just finished a Weber 6A20 kit so I figured I'd start a thread describing the experience. The amp sounds great. Here's a few pics to get things started.

The completed chassis...


The front panel


The rear panel


And the guts


I'll post some notes on the build later this evening. In the meantime, for anyone who's wondering the filter caps won't be left exposed like they are now! Weber forgot to ship the "doghouse". It's on the way.
 

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Discussion Starter · #6 ·
Well, I'll address the important question first. It sounds very very nice. It far exceeded my expectations. I was expecting the OT to be the weak point but to my surprise the amp sounds very warm and full. The reverb goes from subtle to silly and is quite nice sounding. I was thinking I might want to upgrade the pan to an accutronics unit, but the Belton that came with the kit works quite well. It doesn't have the "sproingy" feel that some spring reverbs have. The vibrato (tremolo) works quite well also. The base tone is very much like a Trinity Deluxe I built last year.

And yes - it is a LOT of wiring! I would not recommend this kit for a novice builder. There's a LOT happening in there. I do have to tidy things up with some zip ties but I think I've gotten it pretty clean considering. You can't really see it in the pic but on the tube sockets I've gone "3D" with the lead dress. I also wired the filaments "Hiwatt style". I never like the elevated heater wiring in old Fenders. Makes it awkward to work in there. There are no noise issues doing it the way I did regardless as all the signal wires are well away from the filaments & B+.

I did upgrade/change a few things along with the signal caps. Here's a list...

- upgraded pots to Alpha standard & CTS
- removed switch on intensity pot (original DR didn't have it. Gives a bit of a gain boost but I didn't need that in this amp)
- upgraded lamp assembly (the one that came with the kit had a cheap feel to it)
- replaced fuse holder (same reason)
- removed ground switch (it was unused anyway) & moved bias pot to that hole for convenient access
- added bias test points to rear panel
- used different ground scheme from original DR & Weber layouts. Have separate pre-amp & HV gounds at opposite ends of chassis (quieter operation)
- "isolated" footswitch and reverb jacks from chassis (lower noise)
- changed reverb pot to audio taper (better control)
- upgraded output tube screen resistors to 1K5W (DR's tend to smoke the stock 470-ohms 2w when tubes fail)
- used GZ34 rectifier instead of Weber "copper cap" (for authenticity only...want it to run stupid hot like the original! :))
- aux AC socket is not wired in

I think's that's everything that I changed. Now, a few notes about assembly...

- This kit doesn't have the "refinement" of more expensive offerings (Mojo, Metroamp, Trinity). It took some massaging to get things to line up the way I wanted. Some of the holes don't quite line up as expected. Had to do a bit of drilling.
- second mounting hole for OT was not drilled, but I think that's intentional so you can experiment with placement for lowest interference from the PT. I found it worked just fine mounted in the traditional parallel (but oopposite "axis") position
- Due to the same chassis being used for many of their AB763 based kits, there are a LOT of holes in the chassis to accomodate slightly different configurations. It was a bit disorienting at first, especially considering there's no documentation explaining what mounts where. But after installing some of the obvious stuff it became more clear. I've looked at half a dozen 6A20 build pics and they all mount the OT & choke a little differently. I just went with what made sense to me and the result speaks for itself.
- I'm not a big fan of the "snap-in" IEC & aux AC sockets that came with the kit, but they'll be fine for my application (basement hack kind of thing). If I were gonna gig the amp I'd replace the IEC with a more solid bolt-in type.
- the layout made some of the connections a little challenging and the wiring is tough to keep tidy, but it's a dead-on match to the original Fender layout.
- I would prefer an Accutronics reverb pan, but the MIC Belton unit sounds very good. No reason to change it at the moment
- I would prefer 1/4 jacks for the footswitches, and I considered changing it. Actually, a single stereo jack would have been even better. The RCA's will do until I lose the footswitch & want to use one of the others I have kicking around.
- The chassis have a grounding bolt welded in byut I didn't use it. I couldn't get a tight ground as it started to strip, and it wasn't all that tight. I was using a slightly different ground scheme anyway so no big deal.

And I think that covers all the changes.

The PT provided by Weber has two sets of HV secondaries. I was going to use the higher voltage pair as it appeared from documentation that it would more closely match with the original DR's B+ at approx 415v. People had been getting around 420-440 with the higher voltage pair so I decided to try them. It appears Weber has updated this transformer as I was getting B+ around 500v. That's WAY too hot for most 6V6's and would probably have stressed the rest of the amp too so I decided to use the lower voltage taps. It turns out that these worked out to about 405v, probably due to my slightly higher than normal line voltage, so it worked out prefectly. Again, a little surprising as most people were reporting 385v or so.

I think that covers everything. I have a set of top-hat style knobs that came with the kit, but I've decided to go with a retro-brown look. I've ordered a set of "vintage white" Fender barrel-style knobs, and I plan to have the cab done in vintage Fender brown or blonde with oxblood grill cloth. The speaker is a Weber 12A150 (thanks StevieMac!). The current tube complement is 4 new stock EH 12AX7's, 2 NOS Jan-Phillips 12AT7's, a pair of JJ 6V6S, and a Shanguang (sp?) GZ34. I think I will be putting new stock Tung-Sol 6V6's in though, but it does sound awfully nice with the JJ's.

Boy - that got a bit long-winded, didn't it...
 

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Awesome looking build Darrin. I'm confident the 12A150 will work out great for this particular application. FWIW, I'm using the Weber CC in my brown Deluxe and quite like it. When I do use a tube rectifier, I've had the best results from JJ GZ34s. This is true of all my amps actually, not just with the 6G3. Among the 6V6s I've tried (JJs, NOS Brimars, etc) I prefer the new Tung-Sols. Better bass and top end response with well placed mids (unlike so many other 6V6s). Anyway, I hope they work just as well in your 6A20 as they do in my brownie.

Finally, if you think you'd ever consider a 2x10 format in that amp, GC member NIKO has a baffle for your amp at a decent price...

Cheers.

Steve
 

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Discussion Starter · #9 ·
Thanks all! :D

Steve, funny you should mention a 2x10. That was my original plan, but then you posted the Webers and that changed my mind. With that said I am actually considering getting 2 baffles, and even oversizing the cab a bit in case I want to try a 15" at some point. I like to keep my options open (my "Hunt for Red October" quote for the day).

I'm going to mount the 12A150 in my open back 1x12 tomorrow night & give it a try.
 

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Discussion Starter · #10 ·
Just a quick FYI folks. I was having trouble with some buzz on the vibrato channel. I thought it was a ground at first, but it turned out to be the signal wire from the volume to V2. I replaced it with a shielded wire & all is well.
 

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Discussion Starter · #14 ·
Hi folks. I received the cabinet this week. Here's a pic of the completed amp. I did have the cab built about 3" taller than a stock BFDR in case I want to try a 15" in there.

 

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Hi,

I'm very out-of-date, but I just started to build this amp. Did you installed brass plated? Also, one thing I don't understand, I'm an amateur on building this amps. What's the point of using a brass plate or bus ground if chassis already connects pots?
 

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Hi,

I'm very out-of-date, but I just started to build this amp. Did you installed brass plated? Also, one thing I don't understand, I'm an amateur on building this amps. What's the point of using a brass plate or bus ground if chassis already connects pots?
Welcome. The brass plate gives a better ground connection for all the pots & jacks. It also serves as a ground bus of sorts - the board componants are grounded to it also. And it is easier to solder to than the chassis is. Soldering to the chassis is hard. Can't get it hot enough in a localized spot for a good connection.
If you have a brass plate, I would recommend you use it.
 

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Discussion Starter · #17 ·
I didn't use a standard Fender grounding scheme, as noted in my long-winded build post above, so I didn't use the plate. well, I don't remember using it at least. It was a while ago!

I haven't had that amp fired up on a while. Think I'll give it a go later.
 

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Nice build. I built the amp in 2013 .... only my second build (did the 5e3 first). Mine basically stock with a couple of tips from a Weber forum user for wiring the Reverb up. I did not use Brass plate for ground ended up using a copper wire buss bar for preamp/input grounds and power section mount to PT ground. (something like that ... it's been a while). Here's a link to some Pics. (I'm still a novice you may find it a bit sloppy).

https://plus.google.com/photos/102064953391320019864/albums/5870785701231578225


BTW: I had to do some drilling of holes etc.... also. The OT in Pic had to be moved from where it is in the Pic due to it hitting the speaker when placed in the cabinet. Also the doghouse/filter caps wiring was a pain for me ...it seemed to be upside down and backwards on the Weber diagram... needless to say... I did get it working and it sounds really good even with the cheap parts. Wanting to build something else soon. maybe a weber 45watt marshall clone or the weber AC30 clone. if you are going to build a combo amp Weber seems to be the most inexpensive ( though I suppose if you upraded all the parts it would cost alot more ) ... but you get such a good deal on their speakers when you buy the complete kit ...it's hard to pass up.
 

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first of all....great looking build...I see far too many of those 5 watt toy amps that folks love to build.
This certainly seems like a wonderful reward after all the hard work.

Question...

Can someone please explain the function of the "Normal" channel and why would anyone want to use it.

I can see back in the "good old days" when someone got an amp and their buddy didn't have one, he could plug into the amp and have his own controls. That I understand.
I really dont think that option applies any more but they still keep making that wonderfull useless "normal" channels..

your thoughts.

G.
 

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Looks really good. I like to see nice neat work. I like the mojotone kits because you can solder to the chassis but this looks really good. You should be proud! I get lots of guys building kits that bring them to me to "fix" I end up gutting them and redoing the whole thing. You obviously took your time and that is the key. Its not a race and once its built it will last a lifetime. I would ditch the filter caps you have for something more reliable as the offshore stuff tends to have a higher failure rate. Maybe think about F&T or Atom.. But the Atoms are super expensive right now. Another place to check out for good caps is ARS.
 
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