Noise sensitivity

[warioblast]

I finally put my amp back into its headshell... I stayed without playing into an amp for 3 years...
It's a plexi / JCM800 hybrid built from a DSL50.

The amp is pretty quiet; I'm almost only hearing hum from the PT on the plexi channel. But it is very sensitive; and whenever I get close with the guitar it starts to hum quite loudly. Way louder than I remember. Like I said I havent played a tube amp for more than 3 years.
Could it be because my chassis has a lot of holes in it ? On the front pannel and on top. See pics.

[vampwizzard]

wario, did they use shielded conductors for the input signal to the first triode? Is there foil/metal grille on the back panel to keep the faraday cage closed?

[shooter]

change guitar and it's cable, retest

[shooter]

Adding to DummyLoads reading;

[Latole]

Look amp have too much gain.

A Plexi /JCM800 Hybrid.. from a DSL 50 ??   Show your schematic as built, it is a must to see what you do .
 
Picture inside the chassis may help us.
 

[warioblast]

wario, did they use shielded conductors for the input signal to the first triode? Is there foil/metal grille on the back panel to keep the faraday cage closed?

I built the amp. I used shielded cables from the input jack to both preamp tubes. And yes the headsheel still has its metal cover on the bottom, like this
My chassis is tightly bolted.

change guitar and it's cable, retest

Obviously I have way more hum with a tele or a strat. With a LP not so much. I tried different cables too.

Look amp have too much gain.

A Plexi /JCM800 Hybrid.. from a DSL 50 ??   Show your schematic as built, it is a must to see what you do .
 
Picture inside the chassis may help us.
 

There is not much left from the DSL 50 
Headshell, chassis, transformers and front switches.

I do get less hum with lower gain settings.


Maybe I stayed too long without playing a tube amp.
But like I said the amp can be pretty quiet, but I may move from 5° and the hum kicks in.
The DSL was a very quiet amp. I looked at the schematic and it seems like the 2 first preamp tubes have DC heater. I might give it a try.

[shooter]

the hum kicks in.

so, define "it"
60hz, 120hz, radio station bleed, "static", guitar feedback......

[Latole]

What is that ? i wish a better pictures with resolution

[Latole]

I'll try 470K, one or two.

[warioblast]

the hum kicks in.

so, define "it"
60hz, 120hz, radio station bleed, "static", guitar feedback......

I'll record a clip you'll be the judge.

What is that ? i wish a better pictures with resolution

That's the relay. I used shielded cables there too, I know it looks messy.
The DSL50 restarted its life as a JTM50, 3 years ago. It looked pretty clean back then. I went through a lot of mods since. Hence the messy look, separate bias, turret strips...

I velcro'ed the back of the relay to the chassis so I have easy access to the pins in case of potential debug/mods.

I'll try 470K, one or two.

I'll give it a try ;)

[shooter]

I'll record a clip you'll be the judge

mine are quiet, I have no reference 

[Latole]

Few years ago I built a Marshall 50 watts with master volume, model 2204 with a reverb ( Fender Circuit) . My own desing
All from scratch parts. It is very quiet and play very well.

I built many amps, never kits.

[pdf64]

If the hum noise is dependant on the setting of the vol control on the guitar, such that it disappears when it’s fully counter clockwise, then the noise is unrelated to the amp’s particular circuit per se. ie it’s purely related to degree of gain - frequency.
The same gain - frequency response from a pedal or whatever would result in the same noise, given the same environmental conditions, perhaps most significantly the proximity of the (energised) transformers.

[warioblast]

^^
pdf64,
it does dissapear with the volume rolled off.
And the closer to the PT, the louder the hum / buzz... whatever you call it

Few years ago I built a Marshall 50 watts with master volume, model 2204 with a reverb ( Fender Circuit) . My own desing
All from scratch parts. It is very quiet and play very well.

I built many amps, never kits.

Would you mind sharing your schematic ?

[Latole]

I will post today.
It is on a paper sheet, I'll scan to make a PDF.

[Latole]

There are my schematic for my Marshall master volume with fender reverb
Sorry I can't scan in one piece.

I have to reduce file, forum write ; fil is too big = poor resolution

[Latole]

Schematic last part.

[sluckey]

Unreadable

[warioblast]

Thanks but I can't read anything 
Could you send the unedited scans at warioblast@outlook.fr

[Latole]

Send, sorry my scans are not perfect

[warioblast]

Thank you Latole ;)

[Latole]

I'll try to send you a better copy tomorrow

[PRR]

.

[Latole]

PRR you do a very good job with my schematic, no need a better copy, thank's

[warioblast]

So do you guys think it's normal ?
Should I bother trying to install elevated or DC heaters ?

[sluckey]

It's all good. Leave it alone. Different guitars will behave differently.

[Latole]

So do you guys think it's normal ?
Should I bother trying to install elevated or DC heaters ?

No on both, it is not the issue.

Repairing an amp that never worked without having the amp in front of you is very difficult.
If in addition the amp is a particular design and which does not exist, then this would be mission impossible.