Documenting Express clone performance...

[Noel Grassy]

Excellent!

Thanks man,









Noel Grassy.

[redshark]

What a temperamental amp!!! Well, as I reported on other thread I started experimenting with preamp tubes although I think it's just the beggining. I've been running the NOS Siemmens EL34's and I left the bias set at 44-45mA. That said my preamp tubes were V1 and V2 old Mullard ecc83's and on V3 a new production sovtek 12ax7wa labeled as "balanced".
With those preamp tubes the amp is warm, gainy with a nice clean to mean range. Tried to use a peterson (true bypass) tuner and a Teese picture wah, both with batteries to avoid pedalboard power supply noise. The tuner by itself worked perfectly since it's true bypass, the wah was a diferent story, with the guitar volume all the way up or past 7 the wah performs fine but trying to get funky clean wah sound with the guitar volume less than 5 injects a lot of white noise and hiss in the amp. Emailed Teese about it and he sent me a new pot which is supposed to decrease the white noise.
Going back to preamp tubes I've learn here about Ken's preference of tungsram and EI ecc83's with this amps. I got some on ebay so far 1 EI and 2 tungsram and by experimenting with them I found that both tubes make the amp brighter switching positions and some add hiss to it..I ended using 1 of my old mullards on V1, tungsram on V2 and EI on V3 but I guess is just the beggining of experimenting since I would like to try sylvania's 12ax7's and a few more tungsrams and EI's until I find the best sound for my clone.
There has been here a LOT of discussions about the bright switch, how is wired and if it's too bright or not.
We all have learned a lot from Glen Kuykendall and his approach to get good warm sound with the 2 cables trick, old cabs with prerola speakers etc., is clear to me that he makes an effort in order to dark the amp sound enough to be able to use the bright switch in full and get more chimey bell complex tones when his guitar volume is rolled down.
I hear what he says about the bright switch adding complexity to the cleans but I think Ken's intention to have a switch wasn't to be played in full all the time. If that was the sound he would just make the amp brighter but the switch compensates for a few things. Rooms change, speaker cabinets change, guitars change, pickups change, even guitar pots change. Simply play a LP with 500k pots with your express and then play a "stock" LP with 300k pots. The one with 500k pots would sound good with the mild setting versus the one with 300k will sound muddy if not having full bright switch on.
Other important thing that plays a role here is the output tranny. I think is an interleaved design but I'm no expert. Anyway using 16ohm cabs like Glen uses will get more of the tranny sound in the mix than using 8 ohms or 4 ohm cabinets. More windings are needed to match 16ohm impedance and therefore it will have a bigger impact in the sound.
Opinions change, diferent taste for tone is the fuel of this forums and experimentation but one thing is clear: THIS AMP ROCKS!!!!
Finally my express will have a cherry cab. I have read also that the amp sounds better once inside the cherry box, then I will make some demos and end experimenting with preamp tubes.
If you guys read this, all suggestions are welcomed for better results with preamp tubes.

[geetarpicker]

Funny though, I had been using the two cord trick and old speakers years before ever getting a Trainwreck heck back when the "old cabs" weren't even that old. My prior amp rig was a '68 Marshall Plexi 100 that I played for over a decade without pedals, simply dimed. I ran attenuators live, but wide open in the studio. Live the sound man dialed in chorus, delays, and a Space echo from the PA board and that was it. Simple gain control from the guitar. That amp needed the same tricks and still overall it was a slightly brighter rig than my Express especially with the G12Hs I used to run. Turning down the treble & presence on the amp didn't work as well as I needed the gain of it all dimed. That said the two cord trick was more of a necessity but it also smoothed out the tone nicely. I'd stack two 4x12s plus two heads (backup head was a 50 watter) and run a 20' cable down through the handles. At that point you only had about 12' left so on a big stage you just needed more cable to get around. Hook another in series and good to go. Looking at old videos of Jimmy Page it seems he also ran alot of cable so he could play WAY across the stage. His tone was still quite cutting and clear with the old Marshalls and perhaps would have also been too bright without the long cords. Same goes for Hendrix and the curly cords. I used to use a particular favorite 40' cord that measured about 3500pf. That's almost as much capacitance loading as six 18' Mogamis in series as in over 100' of modern spec cable! I've tried shorter cables with added caps to simulate this, but for some reason the long cable just sounded better. Perhaps there is more to it than just the extra capacitance.

Pardon the long post, continue...

[Cliff Schecht]

You're right in that capacitance isn't the only thing affecting your tone. Every cable can be modeled as an R-L-C circuit that scales proportionately to the length of the cable. Just adding in capacitors will affect the C without changing the resistance or inductance and therefore will sound different than a long cable run. All of this not only affects the amp but messes with the loading on the pickups and changes their characteristics accordingly.

[Noel Grassy]

Noel here are my voltages taken quickly:

V1 pin 1 204 pin 6 177.2
V2 pin 1 262.6
V3 pin 1 206.8 pin 6 210.6
V4 pin 3 408
B+1 409
B+2 392
B+3 312.7
B+4 293.8
B+5 278

Biased at 44mA
Running Allyn's pacific set.

Well I'm thoroughly flummoxed with my build! I've changed V1's tube enough times and I don't have a 'microphonics' issue but I
can't seem to get my plate voltage below 290VDC. My supply string resistors all hover around 9.1K and taking measurements at the point where B5 heads under the pre-amp board the numbers are the same as when measured post the two 100K plate resistors. I'm tempted to insert another value 2Watter
but the formula for obtaining the desired resistance escapes me.Is it R=E/I? All I can remember is the Voltage is always on top, right? (equation-ally speaking that is).


NG.

[ampgeek]

Hey Noel,
Your re-arranged Ohms Law equation is correct.

Strange that you are not getting any voltage drop across your plate resistors. That would indicate that there is no current flow through the tube(s).

What are your cathode voltages? If high (like...above 3 or 4 VDC) double check for a good ground after the cathode resistors.

Any other symptoms that something might be awry?

Dave O.

[redshark]

Noel, that is strange but I don't know what to say. Not much of a tech here. My express came to life without any problems. Actually I was one of those fearless dudes that didn't take any precautions when the smoke test. Just started it up!! the only thing that I did is turned it on with a super crappy pair of 6L6's and old 12ax7s that I don't care for. Bias at max negative voltage of course.
Did you check that your 100ks after B+5 are ok? what about the 9.1k to goes to B+5? did u check for not good solder joints from the last electrolytic cap to B+5? is your wire under the board? are the connections solid?
I would be tracking those little things.

[rooster]

redshark - Just wanted to add that I am glad for you that you got this up and running. Your work looks good, too. What are those pots you used, BTW? Anything special besides the CTS brand that they seem to be? You did well to get that OT, too, I think. One of mine has a TS version Heyboer in it and it just honks with midrange vs. the Pacific I think. Eh, and some people like that, so sure, not an attack on the TS OT.

Thanks too for your info in regard to tubes. The pres are a search but you will find a combination that works for you. Try everything you can. On that note you might want to try a 5751 if you are intent on using pedals. It will change the gain and the 'Glen thing' will be lost, but the pedals might work better for you. I use pedals so this is what I do. With a TB modded TS9 and the amp volume set around 10 o'clock you can really get things going I think. I run the GE brand 5751 but there are others out there. Also consider adding the buffer on the wah circuit. With a TB wah it will only come on for the wah. I run a Clyde Deluxe like this and it sounds wonderful (new pot from Area 51, BTW). For power I am running the J/J KT77s, BTW, and they perform pretty well I think. After break in, 4 hours, they can develope a bit of tube shake noise, but eh, what can you do? Like I said, they are pretty good sounding tubes in the Express. Your Siemens are better maybe but well, for 'new' these are not bad - that's what I'm saying. I have also heard great things about the Tungsol EL34s but have yet to try them. I also heard you need to buy a quad to make sure you end up with a long running pair but this is kind of a Russian tube thing I think. ?? Didn't you reccomend the Tungsol brand 6L6 to me? I haven't tried those yet either but I will.

Any, good job and have fun! There is nothing like an Express that is running right. Hopefully you will have some gigs where you can turn things up, too.

[redshark]

Thanks Rooster!!

I think I didn't recommend you the tungsol 6L6, what I did is mention that one of my fav NOS tubes that I own are the old 5881 tungsols.
I do not claim that I have an extraordinary ear but I'm always able to tell the diference between NOS and new production tubes, so I'm not a collector because you need to be rich for that but I have a few preamp tubes that I like to experiment with and a couple of matched sets of NOS tubes.
About the express I don't think I'm done with it, still experimenting a little bit more with preamp tubes. I think I'm a lucky dude because I didn't find any problems in my build, it was clean, the amp came on the very first time I tried it without a bulb limiter.
Now that you ask about the pots, I ordered first some alphas but I found them cheap and not reliable just by visual inspection so I remember I liked those mojo cts and those are the ones I ended up using. I decided not to get fancier military spec pots because the magic of the wreck is to have a flat eq and control it from your guitar, is not like you are going to be moving the controls of your amp a lot.
Reading old threads here, some Ken fischer articles and the reports of people who had been inside real trainwrecks I came to a conclusion....the real meaning of this:

"Only Ken Fischer can voiced this amps to sound right..."

That is close to the true...but this depended on 2 things.....

A very good ear and knowledge of how tubes perform and...
a big stash of NOS tubes.

I don't think there is any other secret beyond that. The first allowed him to fine tune bias by ear, the second is to give the last voice and character to the amp via the preamp. Let's leave it like that, voicing a clone is a challenge that involves resources and a "magical talent".

About using a wah I would like that to happen without compromising the "clean to mean", is hard because the wah circuit generates certain noise. Having a good pot in the wah is key, actually Geoffrey Teese just sent me one of his new sealed pots that he's using in all his new wahs and yes it seems to be more quiet. I will try it again, the other wah that I actually used with the xpress is the arteffect bonnie which had already a sealed pot and that sounded better than the Teese before the Teese's pot change.

About the use of the 5751 tubes, I did an experiment using it on V2. Very nice and it cut the gain just a little, still giving a nice range from clean to mean. As I said before I will keep "fine tunning" the amp.....My idea is to use a "reduced" board with this amp. guitar>tuner>wah> amp. maybe a delay but I have to see how that works. I have true bypass effects so that is a good start.

[redshark]

Tried to experiment again fronting with a wah pedal...
still dissapointed with the results. This amp adds to the guitar sound, it amplifies everything and it also amplifies the noise. Maybe the suggestion of using lower gain tubes might help but it loses the beauty of the clean to mean.
Oh well, maybe in a "live" situation it could be aceptable.

[two tone]

with my build,I deleted the cathode bypass cap of the second
stage,less hiss ,less gain,smoother sound,you can turn the volume to
ten!