Updated Express Layout Again (V1.4)

[bnwitt]

That is the Francesca layout.

[drhulsey]

... I assume your bright switch is wired like Francesca?

Yes. Mine's wired like Francesca, and I think she sounds very good. I'm sure it just gives you a variation on a theme. I haven't found a schematic around here yet that shows the two bright caps on the same lug of the bright switch. In fact, I've had trouble finding a picture of both bright caps on the same lug. I certainly trust what Allen is telling us. I just hadn't heard it before. I may switch just to see what happens. I have no stake in it one way or the other, except to get the best tone.

[bnwitt]

Doc, I don't think anyone has a stake in it I just like to know what I'm doing makes sense rather than blindly following an example for unknown reasons. Attached is a pdf with the schematic shown both ways. You can see by comparison why I can't imagine it making a difference. Even from a lead dress perspective it doesn't change much.

As far as both caps being on the same lug of the bright switch, I don't think anyone is saying that. Ron's drawing at the moment has the lead of the 500pf cap under the switch layer which makes it look like it is going to the bottom lug. He just needs to bring that lead to the top layer and you'll see it goes to the top lug of the switch. I believe that it has always been a spdt either or switching choice between the 500pf or the 100pf bypass capacitor. I'm not sure why KF wouldn't have had a choice for no bypass cap at all but I guess 500pf is close enough to none (when it comes to treble frequencies) anyway.

[geetarpicker]

Ken Fischer used a SPDT switch with a center off position giving you basically 3 positions. So, in the middle position neither cap is hooked up.
On my original the down position is the 500pf position, center is bypassed, and up it's a 50pf cap. Ken might have ran out of 100pfs that day. I almost never use the 50pf position.

[bnwitt]

Ken Fischer used a SPDT switch with a center off position giving you basically 3 positions. So, in the middle position neither cap is hooked up.
On my original the down position is the 500pf position, center is bypassed, and up it's a 50pf cap. Ken might have ran out of 100pfs that day. I almost never use the 50pf position.

Now that makes alot more sense on the choices.

Here is an updated schematic showing a center off position

[drhulsey]

Ken Fischer used a SPDT switch with a center off position giving you basically 3 positions...

Glen,
What about the center pole of the bright switch and the other end of the caps? Where do they wind up?

[funkmeblue]

I wired my octal xpress (6sl7) first the francesca way and when this thread first came up I changed. Made my amp much noisier, switched it back, did not notice any difference in tone. maybe it's the octals or maybe it just depends on the amp.

[drhulsey]

... As far as both caps being on the same lug of the bright switch, I don't think anyone is saying that...

Maybe I misunderstood what Allyn was saying:
"The others that I have seen and been in, all had the Bright switch wired with the caps on lug 3 (Hot)"
After magnifying Ron's layout, I can see that the 500pF cap lead needs to be brought into a more superficial layer so it can be seen.
I think I have my brain around this, now
Thanks for your patience

[bnwitt]

Maybe I misunderstood what Allyn was saying:
"The others that I have seen and been in, all had the Bright switch wired with the caps on lug 3 (Hot)"

Yeah, that comment threw me too. I don't think he meant lug 3 of the bright switch but rather lug 3 of the treble pot. Maybe he can clarify whether or not my last schematics are correct.

[bnwitt]

I wired my octal xpress (6sl7) first the francesca way and when this thread first came up I changed. Made my amp much noisier, switched it back, did not notice any difference in tone. maybe it's the octals or maybe it just depends on the amp.

Well it seems from your experience that it is a per amp situation. Maybe the note should say "Reverse wires from bright switch common lug and 500pf/100pf bypass capacitors common leads at treble pot to find lowest noise level setup."

[drhulsey]

I have revised the Express schematic to reflect the more common bright cap/switch arrangement. I have forwarded it to Ron Worley for the file.

[bnwitt]

I have revised the Express schematic to reflect the more common bright cap/switch arrangement. I have forwarded it to Ron Worley for the file.

Well hopefully this won't lead many to build noisier amplifiers.

[drhulsey]

... Well hopefully this won't lead many to build noisier amplifiers.

I put a note about Frannie being different. The builder can choose.
I wish I had the time to send you my clone to scope out the difference in the two wiring schemes, but I use it most every weekend

[bnwitt]

I wish I had the time to send you my clone to scope out the difference in the two wiring schemes, but I use it most every weekend

I'm sure its a minor mystery that won't reveal any epiphany. When I build one again I'll do the tests and inform all. It still amazes me that it makes any difference at all and it probably only does because it is in the first stage preamp section where the slightest noise is amplified in a big way. I'll be anxious to hear your findings when you switch yours Doc.

[skyboltone]

Ron,
I would say you still have the bright switch wrong in the layout. The wire from the right lug of the volume pot should go to the middle lug of the bright switch. Each cap then comes individually from each end lug of the switch and then to the middle lug of the pot which is connected to the next stage grid. This gives you a selection of either the 500pf or the 100pf as the bypass across the volume switch to the next stage.

See the picture of Franchesca attached

You're not getting the big picture bnwitt. It will and does work the way Ron and Glen describe. I think the whole business is loopy anyway. Total brite cap "antenna" is identical in both cases. It's about lead dress though, and apparently KF did it both ways. There's no "right" way.

Does it make a difference which end of the resistors goes towards the pots? I've heard they sound better with the stripy end north......