New Express, new noise

[geetarpicker]

Good tip about the leads. When it was new ,my original '89 was a little tempermental and would sometimes squeal if the volume was pegged. The trick on mine was a little bit of foam rubber wedged under the PS board, so that the OT primary wires were held down tight against the chassis right as they went under the board. That said, in recent years the foam rubber piece has gone missing but the amp now remains stable even through the wires have sprung up just a tad. Still, it's worth noting how even slight lead dress changes in these amps can make a big difference. I've also noticed Ken used a little super glue on a few preamp wires (though you can barely see it) to keep them from ever moving.

[Kassie]

Good tip about the leads. When it was new ,my original '89 was a little tempermental and would sometimes squeal if the volume was pegged. The trick on mine was a little bit of foam rubber wedged under the PS board, so that the OT primary wires were held down tight against the chassis right as they went under the board. That said, in recent years the foam rubber piece has gone missing but the amp now remains stable even through the wires have sprung up just a tad. Still, it's worth noting how even slight lead dress changes in these amps can make a big difference. I've also noticed Ken used a little super glue on a few preamp wires (though you can barely see it) to keep them from ever moving.

We are talking about high current wires.. the higher the current, the more prone to wire vibration. So filament and OT primary's are excellent candidates for that. There is a reason those wires need to be stiff and twisted tightly (fender used stiff solid core for heater wiring for instance).

Further for lead dress.. running anode and cathode wires parallel stabalises (out of phase, hence negative feedback).. you can cross the grids a bit or use a shielded wire (or 2). Good quality shielded cable should result in no audible tone loss. We are talking about 30cm of cable here. And if any, most express clones tend to sound too bright anyways.

The grounding wiring is actually quite poor on the express if I dare to say. Grounding all over the place.. it would be better to use a floating buss bar (like a dumble) and attach all the ground points via a 2 star system (including the buss bar). So one at the input jack (for all the preamp circuitry) and the other at the main power line (including the caps). The reason why Ken got away with it probably is because copper is a better conductor than aluminium.. therefore the currents travel faster through the buss bar and not too much interfering with the pots.

I played my clone a while with the attenuator on maxed out. It's actually quite scary to hear all the rattling noises... power tubes, chassis and PT. But there is nothing quite like hearing the electrons hitting the tube glass and seeing the blue glow coming down when you smash an A powerchord.

[Progear]

Hey Smoke,

I am wondering if the MV / low growl issue could by caused by the OT primary wires needing to be swapped? This would cause the global negative FB to become positive FB, thus causing oscillations. This could only happen if you are employing the Lar Mar style MV.

Cheers,
Lou

Lou,

Just swapped in a new pacific OT from RJ, the amp was howling like a wolf and squealing like a pig, swapped the OT primary and wa-la, solved problem..

Thanks
Lou.

[Smokebreak]

Ha! How interesting this thread is revived. I am, as we speak, swapping in MC OT in the Express amp in this thread, and it's...errr...no longer an Express, either. It just wasn't workin for me in this one. We'll see what she's become in the morning

[JazzGuitarGimp]

Okay, I'm thoroughly confused: who's building this amp, Smokebreak ir Progear?

[Smokebreak]

Progear will have to chime in, but I'm assuming he came across a problem solver in this thread? I just happen to be reworking this chassis as we speak. I'll call it a coincidence

Any suggestions on what this Express could become? I'm leaning 6L6 forgetten silverface.

But yea, what are you working on progear?

[M Fowler]

Add one more pot and make it into a JCM800.

[Reeltarded]

Real simple to make it a plate drive 4 stager. Easy weasy.

-gasps-

[Smokebreak]

Add one more pot and make it into a JCM800.

I actually did that the other day ...not the extra pot/normal master on the front but using previously installed ppimv on back...kinda wide open 800...didn't sound so good at lower volumes. Challenge is working with faceplate, which is done. Right now it's ppimv plexi, which didn't sound great either, thus leading to the ot swap

[Smokebreak]

Real simple to make it a plate drive 4 stager. Easy weasy.

-gasps-

I thought about that too but I've got that 3+CF switcher to finish up too, so I want something you've got to crank to get nasty with this one.

[Bob S]

My Express is now a big bottle Rocket with KT66's...
Just sayin.

[Smokebreak]

My Express is now a big bottle Rocket with KT66's...
Just sayin.

That sounds nice. What sort of KT66s are you running and what OT?

[Progear]

Progear will have to chime in, but I'm assuming he came across a problem solver in this thread? I just happen to be reworking this chassis as we speak. I'll call it a coincidence

Any suggestions on what this Express could become? I'm leaning 6L6 forgetten silverface.

But yea, what are you working on progear?

Sorry folks for the confusion, all I was trying to do was thank Lou with helping me fix an issue with my Liverpool after a OT swap.

[Bob S]

My big bottle Rocket has a Heyboer 11415 5k2 OT.
It's running GT KT66's
Also got a Rocket Reverb with JJ KT66's - same OT.
If you do this watch out for cab height - KTs are tall & the pan hangs from the ceiling.
Really Fat tone on both of them.
Switch out the verb & they sound the same.
To my ears anyway.

[JazzGuitarGimp]

Progear will have to chime in, but I'm assuming he came across a problem solver in this thread? I just happen to be reworking this chassis as we speak. I'll call it a coincidence

Any suggestions on what this Express could become? I'm leaning 6L6 forgetten silverface.

But yea, what are you working on progear?

Sorry folks for the confusion, all I was trying to do was thank Lou with helping me fix an issue with my Liverpool after a OT swap.