# Re: Reducing AC Filament Hum On A 5W SE

Phil S. wrote:
"Jim" <jim@xxxxxxxxxxxxxxxxxxxxxx> wrote in message news:VYidnQZlsZMik1DUnZ2dnUVZ_v2dnZ2d@xxxxxxxxxxxxxxxxxxxxx
Phil S. wrote:
"Mr. Green" <cliff@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message news:4fd21f2c-cf6b-4c96-8d2b-20e2eed92c13@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
On 27 Mar, 12:31, WB <s...@xxxxxxxxx> wrote:
Mr. Green wrote:
I've looked at several options and have narrowed it down to four
Are you using a choke ?

What is the AC ripple on B+, B1+, B2+ ?

What frequency is the hum across the OT ?
No choke, no way of measuring ripple or freguency. Come on, I'm just
an amature having some fun playing with my toy amp ;-)

I'd like to try out a one of these methods of reducing heater hum -
it's just an urge. Was just wondering which method, people who know
think, has the least chance of frying the tranformer if something
fails? Does a low wattage load resistor offer any protection?

I'll probably try out connecting to the centre tap and see how it
sounds. After all, you learn nothing if you do nothing.

Cheers, Green
============================
AC ripple? Just set your meter to ACV and find out if there is AC running on the circuit. Red probe to the + side of the cap and black probe to the chassis. You should see a few mV.
For frequency of the hum, use your guitar as the guide. Roughly, low A# is 60Hz, and next A# is 120Hz.
Open low E is about 82 Hz, right?

Oh, what's an octave among friends? Of course. Sorry, I missed this one by a bit. 60Hz is below the low E. Low A# on the guitar is about 120Hz. A below low E is 55, then 110, 220, 440, etc.

Your post would work better on a bass guitar, where low open E is about 41 Hz.

You and I know this, but it also bears mentioning that...

When you play an open E on a guitar with an guitar amp, there's a heck of a lot more frequencies coming out of that speaker other than the primary 82 Hz fundamental. Guitar amps generally have very poor response below 120 Hz or so, compared to frequencies above 200 Hz. That alone may make hum less of an issue in a small combo than in a tube hifi amp.

60 cycle hum sounds like a low hum. More like when you touch the tip of a cable that's plugged into your amp. 120 cycle hum tends to sound buzzier, especially with poor filtration on power supply.

If you have a keyboard handy, take a look at http://en.wikipedia.org/wiki/Piano_key_frequencies This would work best on a synth with a sine wave, but you can probably get a better idea of the difference between 60 and 120 Hz on the keyboard than on a guitar. Compare key #15 (B1) to key #27 (B2). With electronic keyboards, you also you need to make sure that the range is transposed to the lowest range of a standard 88 key piano.

Once you figure out the difference, you will know it when you hear it.
.

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