ScaleAutoArt
Super Member
It sounds pretty good out of the box but it is noisey . I would love to know if grounding pin 9 will take most of it away. Will see after I do the soldering tomorrow.
Little Bear Tube Phono Pre??
- Thread starter sled108
- Start date
vinylkid58
Super Member
sled108
Super Member
Have you checked the Voltages at the Blocks? The 6.3v & 15v for the Heaters are Very Important. They were 7.3v & 18.2v on mine. I used Diodes to drop them.
ScaleAutoArt
Super Member
How about JJ Tesla high gain 12ax7 tubes?Maybe the stock Chinese tubes aren't helping.
jeff
vinylkid58
Super Member
No, I was thinking of the Russian 6N2P-EV.
BTW, it's just "JJ". Tesla hasn't made audio tubes in many years now. They still exist, but only for industrial goodies.
jeff
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ScaleAutoArt
Super Member
What is the purpose of the bold white arrow with a "J" next to it?
The hum is coming from the tube near the input/output jacks. When I tap that tube it thumps... normal?? or could this be the source of the hum?
The hum is coming from the tube near the input/output jacks. When I tap that tube it thumps... normal?? or could this be the source of the hum?
ScaleAutoArt
Super Member
That was my next move. The hum increases with volume.
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ScaleAutoArt
Super Member
It does not move with the tube.
sled108
Super Member
How far do you Turn it Up until you Hear the Hum at 6 Feet? You will hear any Tube Stage if it is Up enough...And, this Is the Most Economical Tube Phono Pre that you can get. Mine will get to 12:30 before I Hear It...By then, when the Needle hits the Groove my Neighbors know what I'm Playing...
ScaleAutoArt
Super Member
About 12 at 6 feet...and of course the sub enhanced it depending on it's volume. I normally listen st about the 10 o'clock position so I am OK with it...just wanted to be sure it was not abnormal. My art DJ as I'd dead quite but lacks the warmth and mid range this has.
ScaleAutoArt
Super Member
I understand... having modified a jd9 and owned a ms22b...this is closer to the jd9 in performance so I made a good purchase. The ms22b falls flat stock.
ScaleAutoArt
Super Member
I now have found most of the hum is coming from the sub...more gain - more hum.
sled108
Super Member
They are the 2 Smaller Red Wimas...
Jimerson
Well-Known Member
Yeah, mine sounds very good, but hums like a box of bees. One reason is the gain is so high, I can barely crack 8 o'clock on my preamp. The 6z4 and one of the 6n2's are suspiciously bright. Sled, you mentioned some diodes to tame the voltage, could you be more specific, like what kind and where to put them? Thank you.
As an experiment, I covered the unit with a box of foil grounded with a gator clip and 90% of the hum disappeared. No, I didn't leave it on there! Looks like an enclosure would benefit mine.
As an experiment, I covered the unit with a box of foil grounded with a gator clip and 90% of the hum disappeared. No, I didn't leave it on there! Looks like an enclosure would benefit mine.
ScaleAutoArt
Super Member
I am new at some of this but would connecting a ground from the existing terminal to another components chassis work? I guess it won't. So...simply dropping the assembly into a metal chassis should work and if so how does one ground the chassis?
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