Express done.. I love it! (title edit)

[tsl602000]

I played around with pre-amp tubes today and finally settled with a TAD, Ei, vintage Sylvania combination that made the amp a bit smoother sounding.

The wall voltage in my house ranges from 225 to 235V. I have Nik's 220/240 PT and initially connected the 220V tap.
With the 220 tap I got too high voltages, so I changed it to the 240 tap. Now my voltages are like this:
B1: 378
B2: 364
B3: 292
B4: 275
B5: 259
bias: -26.4

The pre-amp voltages are all in range except for pin 7 on V3, which measures only 10V and my heater wires measure 2.55V rather than the normal 3.15V

I still hate the low end when heavy distorted. It's not tight, and buzzy on every low note I play. Would a choke instead of that huge 1K resistor take care of that?
Higher up the neck the notes start to "sing" with my new pre-amp tubes. The amp is not noisy at all, no ghosting and no oscillation.

[doctord02]

The target voltage for B1 should be apx 395-405V You may have been closer with the other tap. A choke will tighten it up a bit, but I think it will drop your voltages even further. Perhaps try the other tap again and either adjust the power resistors to lower the voltage or try your choke there...

[castor]

Check again for wrong or false connections.. since all heathers ar connected together, you should have the low value on all tubes.
If you misure the voltage between pin 4 or 5 and 9 of 12AX7 you should have a value from 6 to 6.5 V..

[tsl602000]

Castor,
There are no wrong or false connections on this amp. I checked everything at least five times.
I measured the heaters to ground.

[Fischerman]

tsl,
When I first built my Express I experienced exactly what you are (based on your descriptions). The amp got real distorted alright...but the low notes were way too muddy. A funny description I heard on another amp site is "like a foghorn with your head wrapped in waxpaper"...or my own description...the Contra-kazoo. I like more of a percussive, crisp attack that has a woodiness to it...more cello-like.

But my amp had power scaling and I was using the Mallory 150s and the stock Ceriatone filter caps. However my voltages were spot on and I used good Heyboer iron (5k2 primary). So I didn't know what to 'blame' it on...still not sure.

Anyway...here's what I did that helped:

The PI plate resistors are IMO (at the very least) backwards...the 91k should be on the 'input' triode and the 100k should be on the other one. But for me...91k is still too high and I went to an 82k (like most amps including Marshalls). That gets the PI much more symmetrical and less fuzz-like. Then I increased the 10k tail resistor to 22k (I've heard other people went up to 39k...which I guess is a Liverpool value). I never adjusted the PI cathode resistor...with a 39k tail you might need to (increase it).
EDIT: I just checked the Ceriatone layout and he switched to an 82k plate resistor on that plate of the PI...I also noticed that the PI is wired a little 'backwards' in that usually the plate resistor closest to the preamp end of the board is for the main input and the one at the far power tube end of the board is usually the second input (on most amps I've seen)...on the Ceriatone it's reversed from this. In any case...make sure that the lower value resistor (whether 91k or 82k) is on the first (main) input to the PI and the 100k is on the second (unused) input.

I still wasn't happy and went to a more Komet-like preamp (sans Fast/Gradual switch) and that seemed better...but AdmiralB (another poster here that tried both preamps plus the Concorde preamp in the same amp) said he thought the Express had a tighter attack. I didn't experiment with different cathode cap types (none on hand to try) but some posters here have said that certain ones sound like crap...when I switched to the Komet pre I used some non-elytic .68uFs that I've used in Marshalls with good results.
Another EDIT: It appears Nik is using different cathode bypass caps now...mine didn't look like those blue ones pictured on his site.

I still plan to try the Concorde preamp (which is pretty much just adding a cathode follower at the end of the preamp and adjusting a few other values). If that doesn't cut it I may try a Marshall 2203 type preamp...having the tone stack later in the preamp usually works better for me.

I should also add that I think much of my disappointment with mine was more of a "it's not you...it's me" thing. My Express sounded very similar to many of the clips I've heard...it sounded very close to those ZZ Top riffs that Glen did in those shootout clips. But that's just not the tone I'm after...I grew up listening to modded-Marshalls and boosted Marshalls and I really have to have that crisp, fast attack to be happy. I'm also not nearly the finesse player that Glen is so much of the Express magic is lost on me. I'm a crank the guitar volume to 10 and wail player...that doesn't let the Express...express.

Wow...that got long-winded...sorry but I hope it helps.

[tsl602000]

Fischerman,
Thanks for taking the time to share your story!
I'm starting to like the tone "higher up the neck" on this clone, but playing a powerchord makes me go "yuk" again.

I'll invert the PI plate resistors and see what happens. I'm also planning to change the OT to the 5200 taps. Thing is that I can build an amp, but I have no clue what I'm doing..

Changing the pre-amp to Marshall style is something that crossed my mind too.
I don't know how a Komet or Concorde sounds and I've never seen a schematic of those.
However, changing this Express into a Marshall/Express thing could be just my ticket to go.....

Thanks,
Coen

[ODwan]

Hello,
you can also try to increase the capitance on the PI and Screen, maybe even the Plate supply nodes. As I played around with my clone I did this and it had most effect on the PI node. The bass got tighter up to sounding sterile and lifeless. Just an idea, but maybe adding 10-22µF would make yours sound right. After all, tweaking is what building Trainwrecks is all about!
As KF said: milk the most out of the amp!
Have fun,
Timo

[Fischerman]

tsl,
Don't necessarily invert them...just make sure that the lower value plate resistor (91k in a 'stock' Express) is for the plate that is the main input for the PI. So if your preamp output (where that 1M resistor and .1uF cap connect) goes into pin 7, you want the plate resistor for pin 6 to be the lower value one...but if the input grid is pin 2 then make sure that the plate resistor for pin 1 in the lower value one.

Yours actually looks right from the pic (it looks like you're using pins 6, 7, & 8 for the main input) but I can't be 100% sure because I can't see exactly where the wires go under the board. If yours is already correct...maybe try an 82k instead of the 91k. And also try a 22k tail resistor instead of the 10k for the PI...see if that helps.

The 'problem' is that sometimes the PI main input triode clips way before the other one and it's too asymmetrical and has that 'fuzz-like' attack...which also sort of chokes the tone such that it doesn't sustain as well as it should.

[tsl602000]

Timo,
Forgive my ignorance, but where would I put that 10-22µF cap exactly?
My band played "near Hannover" a couple of months ago. I'm sure you know that great place called "the Bluesgarage"....

thanks,
Coen

[tsl602000]

tsl,
Yours actually looks right from the pic (it looks like you're using pins 6, 7, & 8 for the main input) but I can't be 100% sure because I can't see exactly where the wires go under the board. If yours is already correct...maybe try an 82k instead of the 91k. And also try a 22k tail resistor instead of the 10k for the PI...see if that helps.

Yes, I'm using 6,7,8 for the mail input and it's got a 82k installed.

The 'problem' is that sometimes the PI main input triode clips way before the other one and it's too asymmetrical and has that 'fuzz-like' attack...which also sort of chokes the tone such that it doesn't sustain as well as it should.

That is EXACTLY the problem with this amp. I'll try a 22k tailresistor. I'll let you know!

Thanks,
Coen

[ODwan]

tsl,

The 'problem' is that sometimes the PI main input triode clips way before the other one and it's too asymmetrical and has that 'fuzz-like' attack...which also sort of chokes the tone such that it doesn't sustain as well as it should.

Using "balanced" dual triodes for the PI helps that, too. Balanced means that the tubes are selected for equally performing triode sections.

The 10-22µF elcap should be in parallel with the 20µF powersupply filtering cap that is connected to the PI plate resistors.
And yes, I know the Blues Garage! Great place! I've been there only twice, though, to see Carl Verheyen and Popa Chubby. "Near Hannover" is actually 60km south of, so it's over an hour drive from my home. Can you tell me the name of your band? Would be interesting.

Greetings,
Timo

[tsl602000]

Ok, I changed that 10k tailresitor for a 22k and I can't believe what a difference that makes! I'm actually starting to like the amp now.
I'll even try a 32k and see what happens. Thanks so much for your input!

[ODwan]

Check this out for good info on how a Schmitt splitter works:
http://www.aikenamps.com/LongTailPair.htm
Timo

[tsl602000]

Thanks for the link, Timo!

I did a few "mods" on my clone. I installed a hi-cut like a Komet, changed that tail resistor to 32k, changed those cathode bypass caps to Sprague's and installed a 820 resistor between on pin 2 of V2.
The amp sings like $%^&%* now. The bottom end is so much tighter and I'm starting to like it alot.
The most remarkable "mod" is changing that tail resistor to a 22k or 32k.

[Fischerman]

I also used a Hi Cut but I used it instead of the Presence (just put a 4.7k resistor in it's place). I typically run Presence controls all the way down anyway and my Express needed the ability to reduce highs...not add them.

Glad you're starting to like it!