Preamp Deal of the Century

abe:

i built the cable as per your instructions, but the hum is still present no matter which way the cable is oriented. i'm going to try to spread the cabernet, cabernet power supply, and yamamoto as far apart as possible tomorrow just to be sure it isn't some kind of interference causing the hum. any other ideas? thanks.

Hello Kgturner,

Hmm....I was hoping that the cable will solve your hum problem. I guess spreading the components out is the next thing to try.

So, when you use a different preamp, you do not have a hum? If yes, then does the preamp and amp have a ground point on the back or chassis where you can hook them together?

Does the Yamamoto use tubes? I am not familiar with them but if it does and tube rectified, have you tried a new tube in the rectifier position?

Goodluck!

regards,

Abe

abe:

the yamamoto is a 45 tube amp and it is tube rectified. i have a few 80 tubes that i can roll to see if that reduces the hum. i emailed kevin covi and he seems to believe the hum is caused by the 101D tube as when i switch the amp to mute, the hum disappears.

Kgturner,

Let us know what is kevin Covi's recommendation.

here is what kevin covi had to say:

"The hum is coming from the 101D's, and unfortunately hum (and microphonics) are all-too-common attributes of directly-heated triodes."

i sent him a picture of my setup to which he stated:

"I can see right away that the Cab power supply is too close to the preamp, as are the components sitting on top. The DHT's are quite sensitive to external fields so it is essential to keep them far away from any equipment that contains a power supply. The output transformers are also susceptible in this way. The extremely high sensitivity of your speakers just compounds the problem. You also might try building electrostatic shields around the 101D's. As an experiment try placing an empty tin can over each tube to see if the hum goes away. Or maybe aluminum foil. Either way make sure the shields touch the chassis to shunt the noise to ground."