TW "Manning" Express Build

[ChopSauce]

Very nice build. I'm glad the soldering to the sockets went fine. I often thought about that technique but always went back to tagboards, in doubt.

How high did you raised the board above the chassis, approximately?

[jazzbass]

Hi,

clips, clips, clips please

Franco

[pfarrell]

I would have zero issues doing a similar build in the future...assuming it checks out to be quiet(ish) etc...I don't see how this style is any better or worse than the traditional layouts if one needed to access the underside of the board—not easy in either case. I'm more concerned about proximity of heater wires and lead dress...then again, I've done some builds where sensitive stuff was going all over the place—and that amp I'm thinking of in particular (5E3) is absolutely silent when on.

The standoffs I used were 1/2", what I had laying about...seem perfect to me.

(Martin—of course what you state about bias pot hookup makes perfect sense! Thanks.)

[pfarrell]

Hi,

clips, clips, clips please

Franco

Ha! Okay—I'll have to get over the fact that I've only been at the guitar for a little over a year! OMG. I may enlist one of my teachers....

[martin manning]

If you used all under chassis mounted sockets, and made the power tube access holes a bit bigger, you might be able to access the underside of the board quite easily.

[pfarrell]

Quick shot of the front panel (doing a little plaster work in the kitchen). This panel labeling process definitely bears further exploration in the future—it's not hard, and I was able to redo stuff before things dried—I could have made it even more "perfect" but the TWs I've seen are far from that—I like the wabi-sabi vibes—refreshing. Color is possible too. I have a piece of continuing veneer for the top front cover.

Real close to firing up—some tubes arrived today too. Need to connect the MV and shielded leads... then a close look and review... then bulb-limiter comes out...

PF-TWExpress-Manning_08.jpg

[pfarrell]

So... She lives!!!!!!

BUT.

I'm pretty sure something is off someplace. Need more experienced/second set of brains/eyes.

Symptoms:
—Can't find any clean tones (I have zero Trainwreck experience—but I've watched the demo vids I have found up here) and overall I'd say everything is distorted/muddy at some level and the sound seems to die quicker than it should and output seems low..........
—MV doesn't kick in until around 6 (guitar around 3) See pic—Obviously preamp vol changes this balance—no clue what "normal" is for this implementation of MV. If I push the guitar vol, and dial down the MV + V ratio, things get REALLY bad sounding. Tone stack is having an effect—(but overall everything is really distorted) IMO. I've played with all the volumes to see what's what. And the stack to try to figure out if may something is bad someplace....I more or less expected this amp to behave a bit like my MV Marshall (similar wattage) where I can dial in clean on a pickup and then go dirty on another and drive it all crazy good with aggressive playing if wanted—Which is more or less what the Express demo up here showed.
—Not sure if this is related—I can't get any readings off the bias points, could be my noobish status—I have a not lowend Fluke DMM, and I thought I was looking for mV—no readout on any setting—but if I plug in and play—I can see some action in mV DC. I CAN get a bias reading from the bias pot directly which is pegged to one end at: -32.5VDC, so no real adjustability there other than lower, but my PT (Heyboer) could need an R29 (on schematic) adjustment.
—No smoke, no drama, bulb limiter did everything it was supposed to. (Obviously that's not in use now for eval)
—chopsticking doesn't seem to find any culprits!

—I don't see anything weird visually, welds are good—I reverified all the component values and connections (one can actually see the underboard connections in the right light, beep verified them all anyway)—I didn't reflow everything, but did a few spots.
—The voltages B+1-5 are all about 10VDC higher than the schematic, which seems within range but IDK. 405VDC B+1..
—The amp is dead quiet in terms of hum—but since my instinct is the signal is off someplace... Hiss (also NONE) is subject to change.
—I've tried multiple speakers and guitars to rule that side out.
—I haven't put these new EL34s into the Marshall to verify them.
—I swapped the OT leads for fun—no change—and no squeal in either position.

If no-one has any ideas—I'll trace the signal path on the schematic (for my own edification), and put a 1K signal in and see if the scope reveals anything.

It's probably something simple.

PF-TWExpress-Manning_10.jpg

PF-TWExpress-Manning_09.jpg

[martin manning]

It should be capable of loud clean tones. Erratic bias voltage behavior and low/distorted output could be the result of an oscillation. Pull the two preamp tubes and see if the power amp is stable. Take a voltage survey, and see if you can get stable bias readings with the MV all the way up and all the way down. Sometimes MV's can cause oscillation.

[pfarrell]

Thanks Martin. I took the MV out completely, not really knowing how exactly to test for stability with the 2 preamp tubes pulled. What I can report with MV out of the chain is it sounds way way worse, now with added pops and krackles—which is fascinating—before I was at least wondering if it was "normal". All the voltages seemed the same as previous (but I'm not sure what specific voltages I should be looking into as diagnosis). I will put the MV back, and pull the preamp tubes—bias checking w/ those tubes pulled resulted in some insane squeals from the speaker (dummy load?). I'm not sure the bias is unstable. When I take a measurement from the pot (w/ or w/o MV), it's rock solid (and the same either way), I just can't dial past -32.75VDC....lower is available—currently -30.5—and I don't get any readings from the bias jacks (meter set on mV DC)... this is good learning for me for sure! I guess the first build with actual issues, out of 6 completed amps that are fabulous is a pretty good run. Haha. I think I'm going to love this thing when I can get it behaving...

I'm going to reflow every joint to rule that out, never know.

PF-TWExpress-Manning_11.jpg

[jazzbass]

Hi Pfarrell,

I built all three amp models designed by Ken Fischer and the most difficult to make sound as expected is the Express.
You have to consider that ken was looking for the sound by minimizing the components to prevent the input signal from being compromised, but this meant paying extreme attention to the position of each component and to the led dressing. The most striking and significant result was the Express.
For this amplifier I looked for every file obtainable from the web and at the end of the study I decided not to deviate from Ken's project because it would have meant having built another amplifier not Ken's Express.
As a precaution, I turned to Ceriatone who had made a copy that was not perfect but easily modifiable to bring it closer to the original.
Attention, the project is of an extraordinary instability, you are always on a razor's edge but once you have achieved the result you have a truly extraordinary amplifier. It took me over a year to stabilize him, he was like a wild horse. What I got was a sound that, even working a lot on the guitar volume pot, was distorted by just after 9 o'clock on the volume pot. I had to learn how to use the guitar pots well and I was desperate for the quality and intervention point of the potentiometers that I found on the market. I tried with Ken's designed attenuator and already things worked out better but with this amp I couldn't attenuate more than a notch or I was losing sound quality. Then I discovered, thanks also to the diagrams I am attaching to you, that the point where I had to intervene was the coupling capacitor and the resistance to ground after V1b towards the V2a input. Now I don't remember exactly what values ​​I chose but it's finally the way I like it without being too far from the project.
Some members of TAG (see eg. Colossal, Abott, Manning) have created some splendid Express after having studied them thoroughly and on this blog you should find a lot of news but .... the greatest satisfactions I have had by keeping myself faithful to the original design otherwise I would have gotten a Komet.
P.S. I advise you, if you have not already done so, to carefully read "The Trainwreck Pages"

A hug, Franco

[jazzbass]

Hi Pfarrell,

where did you find the schematic to build there Express?
Compared to the diagrams I sent you, the bias adjustment potentiometer has a value and it seems to me connected in a different way.

Franco

[martin manning]

...with MV out of the chain is it sounds way way worse, now with added pops and krackles—which is fascinating—before I was at least wondering if it was "normal". All the voltages seemed the same as previous (but I'm not sure what specific voltages I should be looking into as diagnosis). I will put the MV back, and pull the preamp tubes—bias checking w/ those tubes pulled resulted in some insane squeals from the speaker (dummy load?). I'm not sure the bias is unstable. When I take a measurement from the pot (w/ or w/o MV), it's rock solid (and the same either way), I just can't dial past -32.75VDC....lower is available—currently -30.5—and I don't get any readings from the bias jacks (meter set on mV DC)...

If you pull the second preamp tube it should be dead quiet, and the bias voltage should be stable. That would confirm that the power amp is not the source of the noises or an oscillation. If you can't get any reading on the bias jacks, then something is wrong there. Maybe check that the power tube cathodes and suppressor grids (pins 1 & 8) are grounded correctly through the 1Ω resistors and the test jacks are connected to pins 1 & 8. You should adjust the bias circuit to move the bias range down if you can't get the power tube dissipation where you want it.

[pfarrell]

It's probably something simple.

Quoting myself!

Well, the amp is pretty glorious. I need to spend some time with it... but here's the report:
Martin, since it's his version, had the right instinct. I've never built an amp with this bias setup—though I have read about it—cathodes to ground thru 1R resistor. Long story short—I wasn't giving it the juice! Hence, no "readout" on the meter. Haha. So, now I can tell you (me) what the amp sounds like with no power. The other surely noob thing that confused me was the reading in mV...I twiddled the bias pot until I saw .044VDC on the meter which would be 44mA which is a yes? In any event, I heard a squeal, which was a good sign, swapped the OT primaries, and fired up again, twiddle bias to .044VDC... and .... beautiful clean LOUDness. Noise floor was pretty big—not hum—BUT the MV was disconnected and the amp—while completely underpowered per previous startup attempts, really was better with the MV from a noise perspective... so in that went again... power up—100% reduction in noise floor—lots of control over everything. This is a cool MV iteration. First blush compared to my similarly powered Marshall, this amp has something special I think. I need to try it out with the same speaker... and figure out the edge of breakup and then I can post some beginner clips.

Anyway—more later. I will make a bottom plate for the chassis. Usually I copper line (heavy foil tape) the amp side of the cabinet.

@jazzbass:
Big thanks for all those docs. I had not come across all those schematics. And your instinct was also pointing in the right direction of a solution with your second post. I was working off of Martin's layout (his thread of inspiration is linked in the first post) plus a schematic I did find labeled "Kelly". I compared it to Martin's version to get a sense of whatever... it was helpful. I'd say what I've built is a slightly modded A1a—I changed a couple of Martin's PI values, no real reason. I made some mods to Martin's build in the direction of more "stock"—presence setup. The build you posted is GORGEOUS. VERY nice. The short story is...I hadn't planned to build a TW yet—I'm working on a Dumble #183 in another thread... and I'm hung up waiting for iron...and started perusing the TW forum (I had read the Trainwreck pages at robrobinette's site since his work and generosity has resulted in all of the amps I've built to date—some have TW MV mods)... and got inspired by Martin's unorthodox build... and literally started making it immediately upon discovery...All your points make total sense. I did very little research. Now I have a deeper understanding...Thanks!!!!

[martin manning]

Good to hear! I converted mine back to presence because the presonance would squeal when turned up all the way. You can read about that in the build thread. Another member built one with the presonance, and did not have that issue.

I twiddled the bias pot until I saw .044VDC on the meter which would be 44mA which is a yes?

Correct.

[pfarrell]

I DID read that in the thread about presonance... I may try it later on once I know this amp a bit better.... it's giving really good vibes at the moment. Thanks Martin!
Meanwhile I'll finish the case...give it a home...