1st semi build express help

[23h2o]

Hello I ordered a ceriatone express w/out the trannies and PPIMV. I installed classic tones pt and ot. Amp sounds great but I have noticed that the wires on the mv are not shielded but are just twisted cloth wires and I am having a noise issue. I was told to check lead dress with my guitar volume off and the amp dimed... no noise this way. Turned the guitar volume up and I have a hiss that fluctuates with the mv and on the stranger side at noon on the mv the hiss gets considerable less and then returns just above noon. Used a chop stick to move around the flying leads with no change.

Is the non use of shielded wire the cause? Is the MV the cause. I also notice that the presence knob doesnt do much which i was told is a result of the mv being installed. Any of this true or correct. Im willing to uninstall the mv to gain the presence control function back and loose the noise.

The head isnt mounted in the cab yet, any advice is greatly appreciated.
Thanks sands

By the way nik did a great job on this build, dont want anyone to think im trying to bash his work.

[M Fowler]

Your going to have hiss in a high gain amp like this Trainwreck Express and especially when turning the MV or gain all the way up. This is where you want to roll some tubes through those V1-V3 spots and see what sounds best both in tone and noise reduction. If not using NOS then try gold pin JJ ECC83's.

The presence should be working fine with the MV. Apparently you installed a LarMar PPIMV I assume since you were talking about twisted hookup wires to the MV pot.

Those Triode MC transformers are huge but I do like the tone.

Mark

[martin manning]

Presence loses its effectiveness as the MV is turned down. I think you ordered the amp with the MV installed, right? Do you know what type it is? Mark is right, roll some tubes through, especially V1, to find one that is both quiet and has tone you like. I wonder about the dip in noise with the MV at noon too. It would be good if you could post some good gut shots.

[hans-jörg]

Hi,
with a LarMar MV you have to shield the wires in an Express. With only twisted ones you get crossover (and hiss). Just my experience.

If you leave the MV full open your Presence will work as normal. But as more as you close the MV as less action of Presence pot.

And: (as Mark wrote) tubes, tubes, tubes!

Best

Hans-Jörg

[jelle]

I was told to check lead dress with my guitar volume off and the amp dimed... no noise this way.

Your amp is fine, noise is clearly coming from the guitar. Have fun!

[martin manning]

Doh! I guess we missed that. Finding a quiet tube for V1 is still something to look into, though, and if there is no grid stopper on it, adding one could help reduce the hiss when a guitar IS plugged in. I would like to see the MV and it's lead dress, as this implementation with twisted (not shielded) leads is stable. Mine uses twisted leads and works fine, but it is not built to the KF layout.

[23h2o]

I used JJ tubes power and pre. Ecc83 s and el34.

heres some pics.... I plan to move the heater wires around to the back.

[IMG768]http://i1264.photobucket.com/albums/jj4 ... f2056c.jpg[/img]


[IMG768]http://i1264.photobucket.com/albums/jj4 ... 8e5a47.jpg[/img]


[IMG768]http://i1264.photobucket.com/albums/jj4 ... 542dcc.jpg[/img]

[IMG768]http://i1264.photobucket.com/albums/jj4 ... 12f023.jpg[/img]

I am considering completely removing the master if it will help the response of the presence and tone stack.

thanks sands

[23h2o]

Jelle, how can i make sure? As my guitar is not noisy with my other high gain amp. Nice amps by the way.

thanks sands

[23h2o]

OK been reading the build guide. chord plugged in no guitar. Gotta hum. Am going to move the heater wires to match those of francesca. Do i need to put a resistor on the grid of V2 or is parasitic oscillation a different sound than a hum? IF i do need to do this that would be pin 2 right?

[martin manning]

If the amp is quiet (no hum) with nothing plugged in then the heater wiring is good. When you plug a cord in (with no guitar on the other end) you have opened the shorting contact on the input jack and you are feeding 60Hz (from stray EMF) into the amp. I see there is a small (looks like 2k2) grid stopper on the input grid, and also one on the second stage which I can't read. Parasitic oscillation is typically very high frequency, and often ultrasonic. I haven't heard the noise you are hearing, but IMO you probably don't need to do anything except look for a quiet tube for V1.

When turned all the way up, this type of MV is not affecting the circuit at all, as if it wasn't there. Everything including the presence works as normal.

[23h2o]

So everything looks ok?

will start switching tubes and see what i can come up with got any recommendations for a quiet good sounding 12ax7.

Got any ideas what the dip might be in the mv?


Thanks guys, sands