[Raymond Koonce]

John Byrns wrote:

In article ,
Raymond Koonce wrote:


Patrick Turner wrote:


"Mikkel C. Simonsen" wrote:


Raymond Koonce wrote:


Hi RATs,

Here's a link to a project I've had on the bench for a while and got
finished today. I learned quite a bit on this one.

http://www.timebanditaudio.com/47%20Amp/Carmen47.html

It sounds as good as it looks.

Comments, questions?

Looks great - as usual

Best regards,

Mikkel C. Simonsen


The specs indicate 1.5mV of hum.

In horn speakers with 100dB/W/M that 1.5mV would plainly be audible
if the horns were that sensitive at 100Hz, and the hum was 100Hz hum.

Has any attempt been made to reduce the hum?

Patrick Turner.

Hi Patrick,

My speakers are fairly sensitive, Klipsch Cornwalls, rated 101dB/W/M.
The hum (60 Hz probably from filaments) is not audible to my 50+ year
ears from closer than a normal listening distance. If I stick my ear in
the woofer, I can hear some, but it's not objectionable. I am running
my 47 filaments on AC with hum pots and all I've done is to adjust the
hum pots to the lowest AC at the speaker terminals.

My PSU is LCLCRC and is very quiet, no 120Hz hum at all.


Doesn't a correctly adjusted filament "hum pot" cancel the 60 Hz
component of hum caused by the filament, leaving only 120 Hz hum, and
higher harmonics, due to the filament?


Regards,

John Byrns


Hi again John,

Yes, you're correct. Thanx.

Raymond