Proximity buzz?

[sonofmickel]

Hi all, it's been a while.
I recently acquired a Phaez Rooster (EL34 AB 40 watt Blackface/Bogner Shiva). I get extremely loud hum when my strat gets close to the torroidal PT. I mean loud, almost violent hum! Sorta scary.
I have never experienced PT hum this bad ever in any of my home builts or boutiquey purchased amps.

(fixed-new set of EL34 tubes)There is also a low level 60 HZ hum that coincides with the Master Volume being turned up. It is also there when the amp is at idle and is louder than most amps i have heard. Hummmmmm......

(fixed- reguler dc on the presence ala Marshall) the only scratchy pot is the presence knob, full scratching the full sweep of the pot until maxed.

Any insight?

Forgot...it smells like peppermint inside the amp, NICE TOUCH! I like it : )

[eddie25]

You want to be measuring AC for the heater voltages.

The scratchy presence pot could be because it's the same design as some Marshall's that puts DC on the pot, thus making it scratchy. Nothing to really worry about if that's the case.

The Strat hum could very well be normal also. If it's a high gain amp then I would expect it to be noisy at high volumes with the guitar right near the PT, but obviously it's hard to say without being there.

[Colossal]

If you are measuring 33VDC riding on top of the 6.3VAC heater string, then yes, that is likely DC elevation/offset. This is good practice, easy to implement, and a good idea for any amp with a cathode follower.

[sonofmickel]

Thanks, and a big oops on the heaters.
I measured in AC first but thought it was wrong as I did not read 6 volts!
OK heaters are 80-81 vac, about what should be for elevated heaters. Right?

The Strat buzz happens even on the clean channel. Loudest I have ever heard. Maybe it's just the way the amp is.

I would love to make the Lead channel more Plexi though, the amp seems to lack a bit of sustain, but it does sounds close to my old Shiva that I sold.

[Stevem]

That compacted magnetic flux in one spot on a toroidal is normal as they put out a lot less everywhere else around them!

[Leo_Gnardo]

Hi all, it's been a while.
I recently acquired a Phaez Rooster (EL34 AB 40 watt Blackface/Bogner Shiva). It appears to have 33 volts on the heaters. Is this an example of elevated heaters(still a nooB)? The preamp tubes get quite hot. I have never seen the heaters wired like this, they go from the usual 6.3v PT taps to the power tubes (EL34's) then, as usual, all the 12ax7's(but not twisted!). Then they are finally hooked up at two 6.3 volt taps on the power supply circuit board? 33vdc at all test points?

They must be DC-floating the filaments apparently.

Also I get extremely loud hum when my strat gets close to the torroidal PT. I mean loud, almost violent hum! Sorta scary.
I have never experienced PT hum this bad ever in any of my home builts or boutiquey purchased amps.

There is also a low level 60 HZ hum that coincides with the Master Volume being turned up. It is also there when the amp is at idle and is louder than most amps i have heard. Hummmmmm......

Toroids are s'posed to minimize stray external fields. Theoretically. So much for theory. Possibly the one in the amp is a wee bit under rated for the task, is it MIC? Also if it was designed for 60 Hz use but you're in a 50 Hz area that would derate the transformer some and maybe that's why it's complaining. Overall audio hum might be another symptom.

And...another thing the only scratchy pot is the presence knob, full scratching the full sweep of the pot until maxed.

Any insight?

what eddie25 said.

it smells like peppermint inside the amp, NICE TOUCH! I like it

You and your band will have to bring back the Peppermint Twist. In a similar observation I've found Spector basses smell fruity like cherry, especially the red ones. Beats that funky mold smell that usually accompanies amps & instruments, don't it.

[Colossal]

Thanks, and a big oops on the heaters.
I measured in AC first but thought it was wrong as I did not read 6 volts!
OK heaters are 80-81 vac, about what should be for elevated heaters. Right?

80-81VAC? should be volts DC! The AC component should only be 6.3VAC.

60-80VDC is fine for elevation.

[sonofmickel]

Thanks people.
DC is measuring 38 VDC
AC measures 73VAC now.

AC at the plug just fluctuated from 121, to 129, to 125VAC

The humm/buzz gets very loud when the guitar is(now my Les Paul) within a foot of the toroidal.
The amp Master volume was only opened to 8-9 O'clock.
Still has the really loud proximity humm.

[Colossal]

Thanks people.
DC is measuring 38 VDC
AC measures 73VAC now.

AC at the plug just fluctuated from 121, to 129, to 125VAC

Yes it gets crazy loud when the guitar is(now my Les Paul) within a foot of the toroidal.

Dude, 73VAC or 7.3VAC? check your decimal place!

If you are actually measuring 73VAC on your heaters, you have a problem.

[sonofmickel]

The Dude abides...man!

73.5VAC!

What may be the cause?
My cheapy meter seems to reading correctly.

[gui_tarzan]

Beats that funky mold smell that usually accompanies amps & instruments, don't it.

I like that old funky mold smell.

[Colossal]

The Dude abides...man!

Indeed he does!

73.5VAC!

What may be the cause?
My cheapy meter seems to reading correctly.

Yikes!

Battery check on your DMM? Something ain't right...

[sonofmickel]

The meter seems to read wall voltage, DC on the v1,v2,v3 etc correctly.
I have asked Phaez for a schematic but no reply....

Maybe a failing toroidal?

[sluckey]

You cannot measure your filament voltage from one tube pin to chassis since the filaments are dc elevated. That 73 VAC reading is bogus.

Set your meter to measure AC volts. Put one meter probe on pin 2 and put the other meter probe on pin 7. Then you will get a true filament voltage reading.

[sonofmickel]

the Dude feels shame.....
6.2 VAC.
Such shame....

OK so that seems correct.
How about that hum from the toroidal?

The amp does sound very good regardless of $$$. I have had $3000 amps that pale compared to this. Well, except for the awful proximity hum.