Hotrodster
Member
That's the way I'll probably do also, but use 12v on both outlets.
Feed the Little Bear and Chinese amp I have from it.
Feed the Little Bear and Chinese amp I have from it.
Little Bear Tube Phono Pre??
- Thread starter sled108
- Start date
mvickers03
New Member
I ordered the little bear T10 2.5 pro from Ebaya few weeks ago. I can't see a high gain switch on the device? there are switches to switch out for different tubes though.
Where should the switch be located?
Where should the switch be located?
Hi all. Mine arrived today. I'm pretty impressed... The Chinese 12ax7 valves were really bad!!!! The 6z4 was very hard to seat. I suspect that the transformer is outputting a little high as reported by others as the 6z4 is very bright. I will sort this.
I swapped the valves for some Brimars that i have and it sounds great. Although currently a little muffled in the tops. I am hoping that some different caps to replace those red Wimas might reveal more of the top end.
I am thinking of putting the whole thing in a steel box and replacing transformer.
Does an body have an recommendations for enclosures and replace men 6z4 valves?
I swapped the valves for some Brimars that i have and it sounds great. Although currently a little muffled in the tops. I am hoping that some different caps to replace those red Wimas might reveal more of the top end.
I am thinking of putting the whole thing in a steel box and replacing transformer.
Does an body have an recommendations for enclosures and replace men 6z4 valves?
Hotrodster
Member
maxhifi
Addicted Member
I put mine into a generic Hammond instrument enclosure, and used a 100 ohm 5W wire wound dropping resistor on the primary of the transformer to get the voltages in line. I made tube shields out of HVAC sheet metal and grounded them. I used panel mount RCA jacks and removed the ones it came with. The proper enclosure and tube shields totally killed the hum problem, and the enclosure nicely draws heat away from the transformer and keeps things cool. I also installed an illuminated power switch. All the tubes are the ones it came with.. sounds like magic with my Clearaudio Emotion and Ortofon Blue.
The enclosure also cures the safety problem with the original design... I don't like all that exposed line voltage stuff, and I am not crazy about how that transformer is mounted.
Mine is fully enclosed, no glowing tubes to see, but well, who cares, I have JJ 300Bs to admire, a few 12AX7s are nothing special to see.
The enclosure also cures the safety problem with the original design... I don't like all that exposed line voltage stuff, and I am not crazy about how that transformer is mounted.
Mine is fully enclosed, no glowing tubes to see, but well, who cares, I have JJ 300Bs to admire, a few 12AX7s are nothing special to see.
Last edited:
cheehpogi
It's better to burn out than to fade away.
Where did you get that? Really nice.
batman7349
New Member
Here is what I did for mine. I cut up a side of an old computer case and made an open top box for the little bear to sit in. Then used 2X3 oak from Menards to build a box.
Also used copper foil from a stained glass supply store for the grid on top. Made a tube shield from aluminum screen and grounded everything.
Swapped in two Russian PIO caps and some diodes to drop the voltage.
I paralleled two 1/2 watt resistors to get the cartridge load to 47k.
The only thing I'm not happy with is using a small wooden dowel to turn the unit on and off via the hole I drilled in the top plexiglass plate.
Also used copper foil from a stained glass supply store for the grid on top. Made a tube shield from aluminum screen and grounded everything.
Swapped in two Russian PIO caps and some diodes to drop the voltage.
I paralleled two 1/2 watt resistors to get the cartridge load to 47k.
The only thing I'm not happy with is using a small wooden dowel to turn the unit on and off via the hole I drilled in the top plexiglass plate.
batman7349
New Member
Now that's a good idea!
highwaychild
Well-Known Member
Nope, don't know about this change.
What I did: I got me one of those R-C-thingie ("EMI filter") and shielded all tubes in the signal-path. Shielding the rectifier tube didn't do anything, so I let the tube shine...
The hum is almost gone, I even tried my AT-F7-MC pickup with good results.
The filter can be found here:
http://www.ebay.de/itm/111558091499?_trksid=p2059210.m2749.l2649&ssPageName=STRK:MEBIDX:IT
What I did: I got me one of those R-C-thingie ("EMI filter") and shielded all tubes in the signal-path. Shielding the rectifier tube didn't do anything, so I let the tube shine...
The hum is almost gone, I even tried my AT-F7-MC pickup with good results.
The filter can be found here:
http://www.ebay.de/itm/111558091499?_trksid=p2059210.m2749.l2649&ssPageName=STRK:MEBIDX:IT
Ok, here's a list of what I changed in my T10 Pro v2.2:
- Diodes mod for the 15v (the 6.3v is 6.5v under load on mine)
- New noval sockets along with the shields, grounded
- Russian PIO's instead of all wima's
Well must say that the hum is acceptably gone but another issue has shown up. It's the distortion. Dunno why but first couple of sec's after power-up it's ok but around 45s after startup, when the lamps start to warm up the distortion is awful! It sounds like 96kbps streaming or even worse. Any thoughts of a reason ?
- Diodes mod for the 15v (the 6.3v is 6.5v under load on mine)
- New noval sockets along with the shields, grounded
- Russian PIO's instead of all wima's
Well must say that the hum is acceptably gone but another issue has shown up. It's the distortion. Dunno why but first couple of sec's after power-up it's ok but around 45s after startup, when the lamps start to warm up the distortion is awful! It sounds like 96kbps streaming or even worse. Any thoughts of a reason ?
OneyedK
Active Member
I think your PIO's are leaking...
Sorry but I wasn't clear enough. Actually I noticed the distortion problem before changing caps. It occured somewhere between changing sockets and desoldering the WIMA's and soldering them again ('coz i couldn't stand listening to cambridge's flatness, while waiting PIO's to arrive). Could I have screwed something up ?
OneyedK
Active Member
Yes, but it's hard to say what exactly.
Could be a loose connection, a cold solder joint or a damaged (internally) cap...
Hello, I ordered the new Little Beat v2.5 and really excited I spent the extra money after reading this thread several times. Hope it is already set for 100 pf and 47K Ohm. I read something about a "gain switch"...does anyone know what gain setting this switch is set for?
Question: What mod do I do to have this phono preamp match my Rega Exact 2 Cartridge Specifications: Output: 6.8 - 7.2mV
Capaticance: not sure but I think I heard it was 200.
post 424
Question: What mod do I do to have this phono preamp match my Rega Exact 2 Cartridge Specifications: Output: 6.8 - 7.2mV
Capaticance: not sure but I think I heard it was 200.
post 424
Last edited:
Well I'm pretty sure now that I've screwed something up while changing the sockets coz one of the tubes doesn't even glow now. I'll look closer into it when i find some time
Might even try to resolder original sockets just to try it out. Problem with my new ones is the differens with the pins layout diameter and also pins type. Had to cut them and they doesn't go through holes on the pcb propertly.
the first one is the original and in the back is one of those shielded ones I bought
