first build,output transformer buzzing,dc heaters

[giorgiosecco]

Hi everybody,big problem here..I recently finished my express build,I have a toneslut output transformer that's buzzing,more than they normally do (IMO).
I didnt follow exactly the layout(I'll post some pictures one of these days)cause I used a different chassis,I suspended the heater wiring OVER the tubes,like I saw in some Dumble amp(maybe not as good!!!).I used solid core to do it,I think the chassis "sounds" to much,and vibration from the transformer is mechanically tranferred to the tubes,and they amplify it really well.NOW:before I start trying rubber under the transformer or even substitute it,I wanna try dc heaters,just experimenting and excluding noise caused by heaters ac problems in my wiring.I have a toneslut power supply,with center tap,HOW could I rectify 6,3 ac to dc in my express?anyway,I have many amps and have been playing as a pro in the last 15 years and this is absolutely the best sound I heard!!!Just too noisy,I wanna fix it,need some help from you,guys......

[markr14850]

Is is a 60hz hum or a 120hz buzz?

Is it *bad*, or just mildly annoying when the room is quiet?

If it's bad, something is wrong, and you should find and fix that before trying dc heaters. Make sure you have a proper reference between the heaters and ground - either the heater CT grounded, or the "virtual center tap" made by two 100 ohm resistors. (Not both!) Also, make sure that all of your power supply filter caps are properly grounded.

If it's just annoying, I would add a hum balance pot, and elevate the reference point of the heaters from ground to at least 25vdc. Elevation is super easy (2 resistors, 1 capacitor) and works very well. There is discussion of both of these mechanisms here: https://tubeamparchive.com/viewtopic.php?t=5360

If you want the last 5%, you can do dc heaters. I'd just do V1 and maybe V2. It's probably wrong to do the PI or the power tubes. There are many ways, but try the elevated reference first.

[giorgiosecco]

its something more than annoying,but not so bad you couldnt do a gig,if you compare noise and volume..and,yes its higher than 60hz to my ear.I'm carefully reading the post you indicated,and I'll try the elevation method,I checked the heater's center tap,its grounded,caps are grounded,I tried with a wire to simulate grounding from other points,but still hum!!what do you think about the output transformer,cause I can hear the buzz is the same kind and frequency,just amplified.....

[castor]

One part that can be checked 2-3 times is near the volume pot.. specially the position of the wire that comes from the 1st tube to the central pin of the pot (so the wire that goes out from the pot). Another important thing in sensitivity and noise is the 1st tube.. try replacing it.
castor

[M Fowler]

I re-read your post and do not see that you have told us which amp your building and which layout or version of the layout as they have been under many changes since last November.

Mark

[Kregg]

Did it happen before he plugged in his tubes? Sounds like a grounding issue or the rare occasional bunk tranny. Some of the old HO toy trains used to buzz and hum until you touched the track. Does it go away when you touch the pots?

[giorgiosecco]

I posted an mp3,buzz is louder in real life,than what hear at the beginning and the end of the demo,in the middle me playing.Volume around 2(I'm home!!),vinetto strat straight in the express,shure 57 straight in the middle of a 1x12 celestion gold 100w,in a small anniversary serie marhall cab.
To answer your questions:I followed the last update of the layout,more or less,I must post some pictures but dont have the camera here!the wire goes out of the tube,passes UNDER the board and straight to the pot.It doesn't go away when I touch the pots.Unfortunately,I had a bad 40uf cap that I substituted with 2x20uf,this took lot of space,and the chassis was already smaller!!thank you guys for the support,I hope you can hear the buzz,just the quality of it,its really louder here than in the 57,and it seems a little better when the amp its REALLY warm,after couple of hours

[Kregg]

Wonderful tone, nice playing. It might just take a little flight time to burn the buzz. But, it sounds like a ground. I got quieter with your hands near the pickups.