• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

What tube for QUIET phono pre??

Was just posing the question about what tube type for phono front end would be the quietest ? I have just begun testing a Tetra with 12AX7 frontend. I hear some hum at full volume. May just need to play around with grounding /shielding some more. Comparing to my Bottlehead Seduction with 6DJ8 it is qiueter. The 6DJ8 is supposed to be a low noise design from what I have read.
Opinions???
 

kevinkr

Administrator
Paid Member
D3A triode connected has an equivalent noise resistance of around 60 ohms and as SY can also attest is vanishingly quiet in a phono stage. In fact take a look at his article "His Master's Noise" for an excellent discussion surrounding the design criteria for a "blameless" phono stage. (I designed and built a D3A/5842 based phono stage 3 yrs ago, and without a doubt it is the quietest I have ever used)
 

JMauck27

Member
2010-08-26 10:35 pm
Golden Dragon Tubes

These are THE BEST tubes for high-end audio equipment, much different than a guitar tube, these are made to be completely quiet and clean and bring out all the subtle nuances of your recordings. Fantastic tubes, kinda tough to find though, I found some at guitarpartsdepot.com

Hope this helps!
 

ChrisA

Member
2008-01-08 12:22 am
Was just posing the question about what tube type for phono front end would be the quietest ? I have just begun testing a Tetra with 12AX7 frontend. I hear some hum at full volume. May just need to play around with grounding /shielding some more. Comparing to my Bottlehead Seduction with 6DJ8 it is qiueter. The 6DJ8 is supposed to be a low noise design from what I have read.
Opinions???


"Hum" is not caused by a noisy tube. When we talk about a "quiet" tube we are talking about random thermal noise or "white noise" or "hiss". If you have hum this is something else.

Hum is caused by the AC power supply leaking into the signal. There are many paths by which it can leak:
1) ripple in the DC power supply
2) AC from the heater supply
3) magnetic leakage from the power transformer
Lots of other ways but fix the above first