Re: HO hum hum hum hum

What amp is it? Lets start there. Hum can be minimized...one step at a time, til all the culprits are eliminated. A few tidbits...is it 60 cycle or 120 cycle hum? Using good sprague filter caps with extra filtering in first stage? All tube sockets cleaned and retensioned? Wiring lead dress done properly (shield all long grid wires going to input jacks and volume controls); all ground wires placed properly and tested? All other grid wires as short as possible? Filament leads to output tubes using proper polarity (same pins)? Bias cap and all other caps not leaking and using proper values? Shielding being used for the chassis? step one, what amp is it? :-)
CJ
"Newbie Doobie" <savy@xxxxxxxxxxx> wrote in message news:1142787394.430148.134290@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
I've re-posted this as a new topic so as not to go unnoticed in the
other thread.

I am concerned about noise (hum) and am attempting to make all the
right moves to minimize it. I have just been through tweaking my other
amp with all new filter caps (only slightly higher values than
origional), re routing leads (inc. better zoning of grounds), installed
2 100k Rs in the "make do" heater CT and floated the circuit at +35v,
shielding on preamp signal wires, isolating input jack (did the stereo
jack trick), isolated the speaker (bypassed the jack), replaced B+
carbon comps with flameproofs, replaced any coupling or tone caps that
hummed when I waved my finger near, installed mostly all new and
matched tubes, replaced all cathode bypass caps, re-built the PI (and
subbed in a choke as a tail), installed individual bias pots, cleaned
all pots and tube sockets, re-soldered any suspicious contacts,
Installed a 500 ohm 25 w R after the ss rectifier (before the choke),
and to further address the noise issue drew a deep breath and yelled
"GET OUT!" !!!
This amp now sounds better than it ever did but the hum is still
apparent (not bad but still there... ya know) and even though I
thoroughly shielded and star grounded the guitar and use a 2 conductor
guitar cable with full foil shield grounded at one end only....I still
get a reaction in the eletrical sounding buzz when I touch the guitar's
metal parts or touch the amp chassis (the buzz goes away)....WHAT UP !
When I record, am I gonna have ta stick a wire down in my my boot to
quell the buzz ?
(yes I'll risk death to eliminate the noise !) sheesh....

Short of going DC on the heaters (some report difficulties in
regulating and getting all voltages right),

Would it be a benifit to add more B+ filtration ?

(even though both amps have ss rectifiers I wouldn't want to go so far
with extra filtering so as to affect the tone response (might flatten
out too much )???

Does any one have a spare can of "buzz be gone" ?

What about doing a dedicated (local) chassis ground (instead of
sticking the wire in my boot)... any loop issues ?

Thankfully unplugged is an acceptable style... where is that old
flattop ?!

savy


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