New Express build; first time post

[WhopperPlate]

Hey everyone,

Finally got my caps the other day. Was going to go with all spragues but I soon found that the PT bolts push the caps too high. Ended up with 40/20/20/20 JJ cap and dual 40uf spragues on the mains. Had to angle the stack of spragues to make it fit right, looks kinda funny. Formed them up with 100k r and got it down to 3.5v (low as it would go).

Of course the problem was not solved, same issues once again, I'm just going to go throughout the amp and reflow solder connections next time I get the chance; probably rewire the tone controls when I get some more wire from RJ.

After all this time waiting and not playing the amp I forgot that this thing is a total tone monster, dripping with harmonics.

Charlie

[ampmike]

Hang in there Charlie,I just fired up a twin reverb that I worked on for months,It doesnt bias more than 37 mill and is has a terrible mess of noise,
I even paid a guy to work on it and he was ready to throw it at me,Anyway It is very frustrating but you will get it ,Im sure,Reflow as much as many solder joints,I had at least 10 that were guestionable.Im really down about this amp I had a lot invested in it.But we cant give up,My express is waiting for three caps and im going to fire that up,Gosh I hope it works,Ill let you know Mikey

[WhopperPlate]

Exciting Mike! I hate to send in for repair anything I build, and so do the repair guys. Let me know all about your status!

Charlie

[RJ Guitars]

Hey everyone,

Finally got my caps the other day. Was going to go with all spragues but I soon found that the PT bolts push the caps too high. Ended up with 40/20/20/20 JJ cap and dual 40uf spragues on the mains. Had to angle the stack of spragues to make it fit right, looks kinda funny... Charlie

If you look at a couple of the Ken Fischer builds you'll see that he actually turned the screws over and ran them into the transformer from the bottom. I have since found some special flathead screws that you can put in from the bottom and basically get them flush with the chassis. This will buy you quite a bit of real estate.

The guys overseas also can have an especially hard time with the stack o' caps because some of the euro-voltage power trannies have wires coming out of both end bells. Those can also get in the way of the caps.

I personally prefer any number of alternatives to the stack o' Caps but you can do a few things to make the spragues fit if you get clever enough.

I think it was Dana Hall made an Express with one of those multi-unit can caps and I think the results were that it performed well within the expectations for an Express build.

rj

[M Fowler]

I put my bolts from inside the chassis to the top for added room on most builds. Also on that Ceriatone Express I got a few years back, I ran the PT wires above the chassis to tame that one down. Whew she was an AC humming mess for awhile.

[geetarpicker]

Ken didn't actually put any of the standoff screws into the transformers. However a few of the standoffs on the power supply board are simply sitting as spacers with a dab of silicone holding them in place. There are screws obviously holding all the standoff to the board, but some of them rely simply on the silicone. If I recall correctly all 3 standoffs of the PT board down the center are attached with a screw, plus the one standoff near the ground connection where the AC comes in. The other 3 are siliconed. Yes a counter sunk screw would work nicely, but only if you use a thick chassis. You couldn't really do this with a thin BUD box, it's just to thin to be counter sunk. Even though the silicone doesn't seem like a good idea I've never had any issues in my original wrecks, nor two clones that followed the same technique.

[WhopperPlate]

Well, I swapped v1 and v2 sockets with shielded sockets; definitely cuts down high end hiss with v1 shielded. Still these oscillations plague me. Hit a note on any setting and about a second later the note compresses oddly then makes a scratchy sound, like a 9volt battery testing a speaker.

I have re soldered many different joints, and even tried swapping primaries (amp howled; definitely not the problem). More soldering when I get the chance.

Charlie

[dynaman]

OK, I can't resist opening my big mouth.

I looked at your pics and noticed that you've some really long wires feeding grids. Wouldn't hurt to shield V1b. I often use active shielding for V1s grids and it helps me tremendously. I've yet to hear anyone complain about high frequency roll-off.

You could also try spinning the PI layout 180 degrees so you don't have such long wires feeding the grids of the power tubes. This will shorten the wires and eliminate the need to run them under the board.

What 12AX7s are you using? Tubes with short plates will be less prone to microphonics. JJ ECC83 and Sovtek 7025/12AX7 seem to be consistent and trouble-free.

Have you tried moving the tone control wiring around when you experience probs?

I've had some coupling caps make funny noises when an amp was only pushed hard. Swapped any caps out??

[WhopperPlate]

Dynaman, I appreciate any feedback given.

Microphonics aren't a major issue, just oscillations.

I've been thinking about shielding v1b to the plate, but in my experience (with my Marshall plexi that had problems) the plate shielding killed all the gremlins, but It took away a lot of the magic IMO.

Still I'll probably try it out. I took out the grid stopper on v1b and the shielded cable (shielding did not help problem anyways) so I could try and fine tune without the bandaids, and the amp definitely feels way more responsive, though close to unbearable with the compression / crackle distortion effect.

Probably after trying the plate shield I will pull everything out and tidy things a bit more on the soldering. I've noticed a few solder bubbles pooling on the underside of the board, also I left many of the component leads relatively long (nothing longer than the turret) and they could be trimmed a bit. Besides that, I'll try making all the wire have tighter physical connections and anything else I can think of. Haven't tried swapping coupling caps yet.

BTW for everyone's information I feel the JJ cap can adds way more bass and makes it fatter.

Charlie

[PlinytheWelder]

I have the full JJ can cap setup in mine 50/50 and the 40/20/20/20 and I don't think I lack bass at all. It's a nice alternative and makes for a cleaner layout, IMO.

I think Dana Hall did it first, so kudos to him...

[WhopperPlate]

I swapped back in the F&T caps for some tonal comparisons. Right off the bat I noticed the amp was much brighter and lacked the full bass of the JJ 40/20/20/20. The F&T's add a butt load of highs and sounds brittle compared to the JJ. I immediately swapped back to the JJ and low and behold; smoother highs and fuller lows. Very dramatic change.

Charlie

[JamesHealey]

That's interesting Whopperplate..

I've just swapped out two of my F&T Caps for Vishay BC, these are the bog standard 450v caps from Farnell..

http://uk.farnell.com/vishay-bc-compone ... ay+bc+47uF

Also swapped out the 1.5k and 2.7k cathode bypass caps for Vishay BC instead of the F&T 63v..

Any low and behold much better sounding amp..


I've always Sworn by F&T because I've never tried anything else, I won't be forking out the extra cash again when I can buy these Vishay BC caps locally.

[redshark]

Talking about electrolytics, I used F&T in my express but left them there for a few months. I think they had break in nicely, I don't hear them overly bright or brittle. Maybe is a matter of time for them to get smoother and perform the way they are supposed to.

[Structo]

Interesting about the F & T.

In my D'lite I have all F & T filter caps on the power supply.

I have had a certain fizziness that rides on top of the notes that I can't track down.
I have tried all the tricks to remove it.

Now I wonder if it could be those caps?

Who'd of thought that filter caps could effect the tone of the amp?

[WhopperPlate]

I had the same thing happen to me with my super lead build. Started with F&T caps (except sprague for the screens) and the sound had a lot of edge and sizzle as well the harmonics were gritty and harsh.

First I swapped out the two 100uf on the mains with the sozo royal blues, amp became much warmer. Then I swapped out the F&T preamp for sprague and the amp got too sluggish and a bit sterile, though not as brittle or piercing. I'm going to try a JJ there when I get the chance.

I'm pretty much over the F&T now that all the evidence is piling up. My harmonics with the express are now smooth and clear instead of harsh and piercing, and there is much more touch response.

Structo, I'd give it a shot and swap out the caps for something else if it is really bothering you. I think you'll be happier.

Redshark, where did you use the F&T in your amp? I did notice that my oscillations died down a bit when I swapped out the F&T's. Maybe another piece of the oscillation puzzle. Probably all the high end emphasis.

Charlie