Question about the blueguitar express schematics version a3

[KellyBass]

Greetings all,

Just wondering if anyone out there has ever built the A3 version of the express from the blueguitar.org schematics? Just wondering how it turned out.

Looks like an interesting design. Some fairly radical differences in some of the resistor values...from most of the other schematics.

Regards,
Kellybass

[M Fowler]

I have not built the A3 version but I have changed the Ceriatone Express I have and the fact that A3 uses the 250k treble pot is more standard in a lot of amps.

This is something I was thinking about doing. Also the 500pf cap to the treble pot I changed to 250pf silver mica. The .022 caps to the bass and mid pots I changed to .033 and reduced the bias.

For the first time that Express is has some great tones. I still have the gain, harmonics and less treble but can get plenty of treble with the pot turned up more to 12:00 or switch the 100pf or 500pf in now without having that glass breaking treble. Actually I like switching in the 100pf brite cap in now, sounds good that way.

Mark

[KellyBass]

Mark,

Sounds like you have made some very usable changes. I'll have to give those a try. I would definitely like to tame the treble in mine a bit. Way too glassy...

I'm seriously thinking about tackling the a3 version...I've got the parts...do you see anything on the schematic that might give me some fits?

kelly

[jjman]

I used a 250pf for the treble on mine initially and thought it sounded good. Then at a gig I was wanting more treble so I went to the 500pf and prefer it. Of course there are several other components that could affect which one is "better" in amp X.

[M Fowler]

One thing I did notice is that now I can use the brite switch and engage that quite often now, much better sounding amp overall. I want to check the voltage on my PT and see if that is the reason the Ceriatone is so brite before I modified it.

Mark

[KellyBass]

Well, I tried the 250pf cap and it did the trick! Thanks, Mark! Sometimes the particular room I'm playing in really soaks up the treble...but the 500pf was just too much.

Well, since no one posted any warnings or misgivings about the a3 schematic, I'm giving it a shot. Wish me luck!

[M Fowler]

Kelly,

I am glad the 250 cap worked well. I too have discovered a new amp with my changes, nice. I tried some NOS tubes but ended up using some new GT 12ax7 gold series and man did that amp come alive. I still have some hum so I am going to get some new Mallory filter caps to get the residual hum out of the first stage B1 the rest I am sure will be just fine. I am going to wire series caps to get more filtering on B1.

Good luck on the A3 version and keep us posted its all fun.

I am working on a exact Express, 100 watt Express, 18 watt Marshall plexi into my Estey Organ chassis, Dumble SSS, 59 Tweed Bassman, and Carmen Ghia. Got my Root 66 clone working nicely but still think I will pull the JTM 45 iron and get the correct PT with 50v bias tap and OT with ultra linear taps. Ran out of money! No wonder with all that iron huh.

[KellyBass]

Mark, you've got some cool stuff goin' on! Don't let a little thing like money get in your way!

Big thanks for the heads up on the GT golds!...I've been wondering about those...

On my first express build, I used hovland musicaps for the signal caps and am very pleased. The harmonics are really jumping out tof this thing now. They'd better be for almost $10.00 a pop!

I'll be sure and keep you posted on the a3 build. Hopefully, it will be a gain monster!

kelly

[M Fowler]

Kelly, I looked at those hovland musicaps before and you think that they really helped, maybe when I find a amp that I want to go all out on I will go that route. Actually my favorite TW is the Rocket but I would love to build that sucker into a 80w like Allyn Meyer did with the Express now that would be an amp worth spending some cash on.

Who makes the best pots, in 3/8 long threads. The only pots I find that I like are the Bourns because they are long threaded and cheap. I have bought Alpha and PEC but they have smaller shaft size and are short. I need some advice in this department people.

Mark

[KellyBass]

Mark,

I can't help you on the pot question. Some years ago, I posted a simple question on an audio forum "Who makes the best pot"?

You can't imagine the crazy responces I got!

The Bourns I have used, I loved!

[rooster]

Hey, let me jump in here? Changing the treble cap to 250pf - if it was 500pf originally - would make the amp, all controls being set the same and all other components remaining the same - BRIGHTER, not darker.

So I am confused why it seems the treble became less in the given room. ?

The Hovland caps, yeah, I tried those once. My reaction is that they are maybe going to work in a HiFi amp but not in a musical instrument amp. You should try those Sozo caps in the amp that is running the Hovlands, just do a straight swap on the coupling caps in the audio path - don't bother with the Bass control caps. I would bet that amp becomes immediately more musical. Yeah, I wanted the Hovlands to perform some magic, too, but I don't hear it. Too, think about what some really well known and respected builders are using. Say Dumble as an example. You won't find any Hovlands in there and certainly the price cannot be an issue in a $15K amp.

[M Fowler]

Negative, lowering the 500pf cap to 250pf darkens the tone in my experience. We still have the bright switch with the 100pf and 500pf to engage for more treble boost.

Mark

[rooster]

Hmm, OK. And here I was thinking that a Fender BF was a pretty bright amp running that 250pf treble cap.

...So you are saying that I can make it darker by reducing the 250pf cap to say 50pf?

[M Fowler]

Rooster,

Unless your just trying to make a point about my use of words regarding the 250pf cap?

First off we are talking about Ceriatone Express amps built by Nik they are very bright. Secondly I already changed the tone caps from .022 to .033 and at the same time changed the 500pf to 250pf it is worked great lowering the treble. Now from what I know 250pf should be brighter than a 500pf vs going up the scale to .1, .01 etc. In other amps know we all know that the lower the value of the cap the brighter the tone.

Just so that you can have the last word I will change the 250pf back out to the 510pf Nik had in there leaving my already changed tone caps .033 and see the difference, its still sitting on the table and no big deal to change out the cap for testing.

I don't know if KellyBass only changed the 510pf to 250pf or changed the tone caps as well?

(Edited cap values .022 and .033) C3/C4 are .022uf and C2 500pf on AG layout/schematic in file section. Changed Ceriatone C3/C4 to .033uf and C2 to 250pf


Mark

[Firestorm]

It seems counter-intuitive, but in most tone stacks changing the value of the treble cap affects the midrange "scoop" frequency far more than the treble frequency. In a stock Super Reverb, changing the treble cap from 250pf to 50pf will shift the midrange dip to nearly 2000Hz. Considering that the note on the 12th fret of the high E string is only 660Hz, this would certainly kill off some harmonics. On the other hand, changing that cap to 500pf sets the midrange dip almost exactly to 660Hz so you're beginning to attenuate higher fundamentals.

But it depends a lot on the stack. In a Marshall or a 5F6 or 5F8 Fender, the lower source impedance changes everything.

This is one of the great joys of tweaking amps. Change stuff and see how it sounds.