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Little Bear Tube Phono Pre??

well mine arrived today, got it working but not really impress with it. It sound the same I'm already thinking maybe what I got is a dud. anyways maybe you can answer this simple question; does it supposed to have sound or music coming out even if you turn of the pre amp? because that's how mine is and I really can't tell any difference with the sound. M aybe it would need some burn in time.
 
cbox83 said:
Did anyone just miss my instructions earlier about how EASY it is to convert it to a 6X4? Its 4 solder points. Its worth doing permanently and easily reversible. Took me all of 5 minutes.
Click to expand...

26 pages and I must have blinked. Any possibility of linking to the instructions?
 
maxhifi said:
Here it is almost done. Mods as follows:

1. Off the shelf aluminum Hammond instrument case as enclosure

2. Tube shields fabricated from HVAC steel... Cut to size with tin snips, wrap Around a metal bar smaller than tube, so it fits on tube with Spring pressure.

3. Star grounded to chassis at transformer, inputs and outputs isolated from chassis

4. Will drop voltage to transformer to 110V with a 5W reaistor to be located on terminal strip by Transformer.

5. Pin 9 of 6H2 tubes grounded.

The power switch I bought (carling) melted and was wrecked when i soldered to it.... Damn will have to get a new one and some crimp connectors. Kind of anti climactic to wreck the switch, I can't wait to try it now!

A dumb question - which two tubes should be replaced with my russian 6H2's ? I can't tell from the top of the board which tube does what and don't want to pull the board again.
Click to expand...

Maxhifi, what value of resistor did you end up using in step #4? I suppose I may need a different value, but a starting point might be helpful. And do you have a pic of that particular addition?
 
To get the best from this kit you need to put it into a shielded chassis. This means complexity sealed. I used an old 1970's cassette deck chassis for mine. This gets rid of 95% of the noise. I mounted my transformers outside the chassis.

I also placed aluminum foil over the tubes with a piece of wire running down between the tube and the foil, and then attached the wire to the ground lug. (you have to ground the foil or otherwise it does nothing) The foil and wire is held in place using a cable tie (appropriately tensioned).
The tubes do not overheat.

The only way to stop noise on this kit is to place it into a metal chassis otherwise it gets bad hum no matter what you do. Once in a chassis the preamp is wonderful. The Chinese tubes are excellent and I don't know why anyone swaps them out. They are miles better than the Russian tubes (which have no top end or detail). Don't believe me? put your Chinese tubes back in!
 
eltech said:
To get the best from this kit you need to put it into a shielded chassis. This means complexity sealed. I used an old 1970's cassette deck chassis for mine. This gets rid of 95% of the noise. I mounted my transformers outside the chassis.

I also placed aluminum foil over the tubes with a piece of wire running down between the tube and the foil, and then attached the wire to the ground lug. (you have to ground the foil or otherwise it does nothing) The foil and wire is held in place using a cable tie (appropriately tensioned).
The tubes do not overheat.

The only way to stop noise on this kit is to place it into a metal chassis otherwise it gets bad hum no matter what you do. Once in a chassis the preamp is wonderful. The Chinese tubes are excellent and I don't know why anyone swaps them out. They are miles better than the Russian tubes (which have no top end or detail). Don't believe me? put your Chinese tubes back in!
Click to expand...

It is my considered opinion that you are either crazy or I got a bad set of tubes... Switching them out for nos Soviet tubes was like night and day. The Chinese tubes went straight into the trash. Everything else here is spot on. I used perforated aluminum to make a cage and some copper mesh to make tube shields. The hum is now acceptable. This preamp sounds Tony the Tiger GREAT!
 
Can I use K40Y-9 0.47uF 200V or do I need to find the 450v versions? I might have jumped the gun and ordered the wrong ones......
 
Last edited:
Well… A couple of weeks ago I happened to be in shezhen so I went to this guy's place to get my T10 pro. Got back home, assembled the thing, plugged in listened for a while and told to myself that it was better than my Cambridge 540P. But now, over time after I cooled down a bit after geting my first ever tubes device and it's not so awsome as I thought.
At first : the hum is not gone, I mean I can't compare to those first rev's you guys got but it seems that LB hasn't improved the design in case of hum. Around 50% at my amp and it's really bad.
Second : the chinese 12ax7 seem to be very low quality. As a matter of fact you can see with your bare eyes that different components are used to make the tubes between one and the other.

About the mods. As for now i've only changed the resistors from 62 to 47k cause that's supposed to be better for my cart. I'm also thinking of buying some JJ's ECC83's and russian PIO's.

What more about the hum. It seems that waving my hand around the tubes doesn't make any difference. What I found strange that, when I was turning my record to other side and all I could hear at the time was the hum, I could hear the hum changing to louder or quieter, like switching. It wasn't triggered by me in any way. I observed that it kinda happened "on it's own"

P.S. Sorry for my english but I don't use it on a daily basis
 
jurmaan said:
At first : the hum is not gone, I mean I can't compare to those first rev's you guys got but it seems that LB hasn't improved the design in case of hum. Around 50% at my amp and it's really bad.
Click to expand...

No surprise really.

jurmaan said:
Second : the chinese 12ax7 seem to be very low quality. As a matter of fact you can see with your bare eyes that different components are used to make the tubes between one and the other.
Click to expand...

For anyone buying one of these, the first thing to do is get some decent 12AX7's. Something like a Sovtek 12AX7LPS, which has a good rep. regarding lack of noise and hum.

jurmaan said:
P.S. Sorry for my english but I don't use it on a daily basis
Click to expand...

Actually, your English is better than some of the locals.;)

jeff
 
vinylkid58 said:
Something like a Sovtek 12AX7LPS, which has a good rep. regarding lack of noise and hum.
Click to expand...

What about JJ's base ECC83S ? I'm asking 'coz the Sovtek is nearly twice the price. I understand that the sovtek tube will be better but will JJ ECC83S be noticably better than chinese 12ax7 ?

And about PIO's what voltages should I get those caps ? 400V at least ?
 
I think I'll go for the Sovtek 12AX7LPS then.
I also have to bare with availability in my country.

Can u tell me what are the differences between 12AX7WA / WB / WC / LPS ?
 
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