Little Bear Tube Phono Pre??

[CT Jim]

The seller has remedied the situation, promptly. I did include a link to the TT forum thread, hopefully the seller will start checking his stock!
The ART DJ II or it's bigger brother are on my list.
Thanks

 

[LoStrings]

little Bear Phono preamp

I just took the plunge and ordered the Little Bear...Can one of you explain to me what exactly has to be put together when the unit arrives? I emailed the seller and he told me, but his instructions weren't that clear.

 

[ScaleAutoArt]

I just took the plunge and ordered the Little Bear...Can one of you explain to me what exactly has to be put together when the unit arrives? I emailed the seller and he told me, but his instructions weren't that clear.

You will only need to connect the transformer wires (there is a diagram on the transformer). Peal off the protective paper from the plexi and bolt the top and bottom together. Put in the tubes, connect and play.

 

[LoStrings]

You will only need to connect the transformer wires (there is a diagram on the transformer). Peal off the protective paper from the plexi and bolt the top and bottom together. Put in the tubes, connect and play.

Thank you. I am going to do the mods that all you have done on this thread....Great information.

 

[Wharfcreek]

CTJim, don't know if you're still subscribed to this thread or not, but if so, I may have a bit of 'info' for you that may be of consequence.....or not. But, I too purchased the LB 'SS' phono-pre......and in assembling it, I noted that the input and output as indicated on the PC board were reversed as indicated on the upper plate. I contacted LB about this and, sure enough, they acknowledged that they had a 'run' of misprinted upper plates.....and they quickly sent me a new one....which arrived yesterday. However, it's arrival triggered the question in my mind if, perhaps, this might not be the problem you're having? To check, simply pop the 4 screws off the top and view the PC board by the RCA connectors at each end, and look for the Identification of "input" and "output". If yours is also incorrect and you're going by the top plate......well......I doubt I need say more. Simply reverse it and see what happens. And I for one would be interested in the outcome of this........ Tom D.

 

[ScaleAutoArt]

Screwed up my LB...

I am using Blue Jeans cables and they are very rigid at the connections. While switching back and forth from my SS pre it dislodged the output connector from the board and snapped some of the thin (cheap) pins. I soldered in new brass rod to replace the pins that had sheared, reinforced the assembly and when connected all I get is a loud hum. What have I done?

 

[Wharfcreek]

Sounds like you may have either crossed the connections, or left a ground undone. Just the mechanical act of breaking off the connectors from the circuit board shouldn't damage anything within the amp......other than the connections themselves. Typically an 'input' can be grounded by shorting it completely.....and all it does is cancel any signal from the amp. As this can happen at the pre-amp....then it has the effect of doing the same thing back at the phono pre-amp. So, a 'short' on the RCA connectors shouldn't really hurt the unit. BUT.....if you mixed up the connections when you 'fixed' it.......or if you failed to properly restore the original connections....then you just my have to simply go back and attempt to re-trace the proper original connections and re-do your repair. As an alternative to attempting to restore RCA jacks on the unit, you might consider simply installing some short RCA cables...... just solder the ground and hot leads in the proper areas...then use a double-female connector at the end of your new jumper......or....make the cable long enough that it served to connect directly to your pre-amp. Final comment: If you can't figure it out....consider some pics of the effected area and your attempts at repair. WC

 

[ScaleAutoArt]

Thanks,

I had a look and everything looks fine...I may have a bad solder joint on the unit itself. I will have to re-trace. I could hard wire cables but not sure which wire will go where...can you show me?

I will also contact LB and see if they will send me a new connector. It's been fairly loose since day one.

 

[Wharfcreek]

Scale,

I suggest you pull the top and bottom plates, disconnect the power transformer, and then take two pictures: one of the bottom of the Circuit Board, and one of the top. If I'm not mistaken, this board has traces on both the top and bottom......so might help to see just where the damage is, and what needs to be done to correct it. Tom D.

 

[ScaleAutoArt]

I'll do that... in the meantime LB is sending me new rca interfaces.

 

[LoStrings]

Little Bear Phono preamp

I recieved my Little Bear Phono preamp yesterday (took about a week, not bad coming from China). I assembled it, which took no time at all, and wired it into my system. As everyone reported here, there is a ton of gain and hum from no shielding. I did the copper wire and aluminum foil...helped alittle, but still hum. If I just put my hand over the tubes it quiets down alot, so I really don't know how I will get it to be hum free. I have a Sony cd player that has alot of gain and I made a volume control box to put between the output of the cd player and the input of the preamp...It worked great. I was thinking of doing the same with the Little Bear. I tried the volume box with the Little Bear and it worked great...lowered the gain and the hum. Now I just have to build another one for the Little Bear. Overall I really like the Little Bear. It needs some time to work itself in, but I sat for a couple of hours listening to my favorite vinyl and it got better and better. At first, I felt it sounded alittle bright, but after awhile that kinda went away. I'll have to give it some time to really get a good feel of the preamp. So far, I am really liking it, other than that hum, but I will take care of that.

 

[Wharfcreek]

Would be curious to see what you've done with this outboard volume control? Maybe you could post a copy of your circuit....and a few pics of your completed unit? WC

 

[sled108]

You need to have the Wire Grid over the Top of the LB to the Ground...And, a Pie Pan Plate under It Grounding to the Posts that the Grid is around...
And!!! Check what you have out of the Transformer!!!!

 

[sled108]

Alright Guys...Let me be as Clear about this as I can...If you have a 'Little Bear' Tube Phono Pre-amp....You Must Check the Voltages from the Transformer!! The B+ going to the 3 Screw Post does not matter enough to worry about...What does matter is the 6.3V that goes to the Rectifier's Heater... If that is 7 Volts, then you'll blow the 6Z4, Fast...And then, the 15 Volt Input...It is Rectified to 19 Volt DC for the other 3 Tube's Heaters in Series...But, if you have 17V or more from the Tranny, you will also Fry the 6N2s...It will sound Bright until they Die...The Best way to fix this is with Diodes...

 

[Jimerson]

Sled's right. The diode fix calmed mine right down. The tubes are not glowing so brightly. The replacement Russian tubes helped, too. Mine is dead quiet.

 

[Wharfcreek]

Sled/Jim, Can you guys post some pics of how you've applied these diodes? WC

 

[moodydan]

Post #94, P. 7 of this thread there is a picture of the diodes in place, I believe!

 

[Jimerson]

There are pics and a schematic on page 7 of this thread, provided by Sled.

 

[moodydan]

Hey, Sled, initially you said we would need 1.5A 100V diodes, but I think you said you used 1A 100V because that's what you had on hand. I'm about to order these diodes, should I go with 1.5A? I appreciate it!

 

[sled108]

Hey, Sled, initially you said we would need 1.5A 100V diodes, but I think you said you used 1A 100V because that's what you had on hand. I'm about to order these diodes, should I go with 1.5A? I appreciate it!

Play it safe and get the 1.5A....