Little Bear Tube Phono Pre??
- Thread starter sled108
- Start date
I am pretty new to the audio world and decided to dip my toes into the tube world and bought the Little Bear T10 V2.2 off amazon. My current setup is Project Debut III (Ortofon OM5e cartridge) -> Little Bear T10 V2.2 -> Crown XLS1002 AMP (.775V input sensitivity) -> Klipsch Icon wf-34 speakers.
The issue I am having is the mid range is very distorted. I first listened to Miles Davis' Some Kind of Blue and the highs sounded great, but everything else sounded distorted. I initially chalked this up to the tubes being new and needed time to burn in, but after a few days of listening there has been no change. My buddy who has some experience with tube guitar amps recommended playing something more modern with a lot more mid range to try and diagnose what is going on. We played Journey's Don't Stop Believing and it sounded terrible. I double checked to make sure I wired everything correctly and everything was switched to 6N2. He chalked it up to bad tubes. According to the specs on my Crown Amp and the Little Bear the sensitivities should be compatible.
Do you guys think its the tubes? Or is there a larger issue at hand? I am very new to this and I don't want to spend $60 on new tubes for a $120 pre-amp. Any help you guys can provide would be greatly appreciated. Thank you.
The issue I am having is the mid range is very distorted. I first listened to Miles Davis' Some Kind of Blue and the highs sounded great, but everything else sounded distorted. I initially chalked this up to the tubes being new and needed time to burn in, but after a few days of listening there has been no change. My buddy who has some experience with tube guitar amps recommended playing something more modern with a lot more mid range to try and diagnose what is going on. We played Journey's Don't Stop Believing and it sounded terrible. I double checked to make sure I wired everything correctly and everything was switched to 6N2. He chalked it up to bad tubes. According to the specs on my Crown Amp and the Little Bear the sensitivities should be compatible.
Do you guys think its the tubes? Or is there a larger issue at hand? I am very new to this and I don't want to spend $60 on new tubes for a $120 pre-amp. Any help you guys can provide would be greatly appreciated. Thank you.
I'm pretty new to tubes but i just got my Russian tubes and its working much much better with distorsion and noise. Money well spent IMO.
tried swaping the tubes around and see if it makes it sound different?
Thank you for the reply. I did move the tubes around in a couple different configurations and did not notice a difference. I am trying to borrow some 12ax7's from my buddy's guitar amp to see if swapping out tube clears up the issue. From what I have read online the amp should sound half way decent with the Chinese tubes, but since it sounds so bad with those Chinese tubes I am concerned there is a large problem at hand. Any other suggestions? I am half way tempted to return the unit while I still can...
test it with your friends tubes if you can do it before the time runs out for return. It should sound alright even with Chinese tubes. even with the wrong resistance etc for your cartridge it should just be sounding thin not distorted.
neevo
Super Member
Well it looks like I have hum in my v2.6 Little Bear too. It's loud at half volume on my amp, but to be fair that's also bloody loud on the sound too.
It's not a problem with music but definitely something I'm wanting to get rid of.
The gain switch certainly helps but all it does is boost the output audio signal and so masks the hum vs helping to make it go away. Also playing with the grounding switch didn't appear to do anything.
I moved the LB amp to a space away from the power amp and other cables etc but it made no diff. Also disconnected the turntable earth lead and that made no difference either so something is going on (might see what happens if I ground the TT to the Kenwood amp instead.
Either way I'm pushing ahead with an Alu housing for the amp which hopefully will provide much better grounding/shielding.
Edit: I forgot I had the tube shields. Will test some of those on some of the tubes and report back what impact they have.
Second edit: tube shields did nothing. Rotated all the tubes out for some spares too, no change. Unplugged the earth lead off the TT, no change. My LB is on top of my Kenwood Amp which doesn't help as if I move it up a bit the hum goes down 20%, but at half vol on the Kenwood the hum is still pretty pronounced.
I suspect a metal enclosure is what is required and so I'm working on a solution to fix that.
It's not a problem with music but definitely something I'm wanting to get rid of.
The gain switch certainly helps but all it does is boost the output audio signal and so masks the hum vs helping to make it go away. Also playing with the grounding switch didn't appear to do anything.
I moved the LB amp to a space away from the power amp and other cables etc but it made no diff. Also disconnected the turntable earth lead and that made no difference either so something is going on (might see what happens if I ground the TT to the Kenwood amp instead.
Either way I'm pushing ahead with an Alu housing for the amp which hopefully will provide much better grounding/shielding.
Edit: I forgot I had the tube shields. Will test some of those on some of the tubes and report back what impact they have.
Second edit: tube shields did nothing. Rotated all the tubes out for some spares too, no change. Unplugged the earth lead off the TT, no change. My LB is on top of my Kenwood Amp which doesn't help as if I move it up a bit the hum goes down 20%, but at half vol on the Kenwood the hum is still pretty pronounced.
I suspect a metal enclosure is what is required and so I'm working on a solution to fix that.
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i only need a tube shield on V1 and my hum is only really noticeable at half vol on my Yamaha a-s501. seems it doesn't care about high or low gain on the LB.
if i turn it up to 50% the hum is the least of my issue. getting fined for noise complaint would be worse
did you make sure the tube shield really touched all contacts? I noticed mine did nothing cos it wasn't making a good enough contact at first.
if i turn it up to 50% the hum is the least of my issue. getting fined for noise complaint would be worse
did you make sure the tube shield really touched all contacts? I noticed mine did nothing cos it wasn't making a good enough contact at first.
neevo
Super Member
Left the amp on a bit last night as I was listening to some music at dinner time. When I went to shut amp down I noticed there was an audible hum from the amp, not speaker hum in the audio path, but the actual unit itself was vibrating.
Questions:
1. Could this be contributing to my audio hum issue?
2. What could be causing this? I would assume the power supply? Is this something I should contact the vendor about?
Questions:
1. Could this be contributing to my audio hum issue?
2. What could be causing this? I would assume the power supply? Is this something I should contact the vendor about?
1) Unlikely.
2) It's the metal laminations of the mains transformer rattling/buzzing. Tightening (or loosening) the bolts can tune it out, but the best way to prevent it is to have the laminations and coil potted.
neevo
Super Member
In an attempt to try and rectify the hum in my Little Bear T10 v2.6 I tried a few different options.
1. I found a IEC lead without an earth pin, to see if I was getting a ground loop in the preamp. It changed the hum through the Little Bear (actually made in worse I would say) but was not having any affect that was fixing the issue.
2. I got a bit mad cap, to see if I could shield the unit from interference to see if the issue might be external. Not sure if what I did would have any effect but I thought I would give it a go, what did I have to lose?
The result? Exactly the same
I've been in contact with the vendor to try and trouble shoot and he's been helpful up to this point. I am wondering if there is an issue with my LB that's internal?
1. I found a IEC lead without an earth pin, to see if I was getting a ground loop in the preamp. It changed the hum through the Little Bear (actually made in worse I would say) but was not having any affect that was fixing the issue.
2. I got a bit mad cap, to see if I could shield the unit from interference to see if the issue might be external. Not sure if what I did would have any effect but I thought I would give it a go, what did I have to lose?
The result? Exactly the same
I've been in contact with the vendor to try and trouble shoot and he's been helpful up to this point. I am wondering if there is an issue with my LB that's internal?
lomaster
New Member
Hi, everybody. I here for the first time. And I badly know English. But I want to share the experience with you uses of LB. I did different experiments to improve a ratio signal \noise but then left everything as was in the original scheme. I changed only polarity of power supply of heaters. I cut a board to divide the power unit and the amplifier. Also I replaced sockets of tubes with sockets with shields. Here is how it looks now. The sound became much better. Noise disappeared. And already almost everything is pleasant to me
Attachments
vinylkid58
Super Member
neevo
Super Member
Trouble shooting my T10 v2.6 issues with the supplier. I have to say they have been fantastic to date and offering to ensure I am completely happy. Tonight I will be testing the Toroidal transformer voltages to make sure its all in spec. I have a question for those that have done this in the past. I assume I find a suitable ground point, then simply probe each of the mounting screws from the transformer to measure the voltages (vs measuring across each of the mounting screws)?
I am still concerned about the mechanical hum the transformer makes, however the vendor seems to think (as did someone else in this thread) that its not the cause of my excessive audio signal path hum.
Once I have the voltages I will speak to the suppler about solutions to test/fix. I will keep everyone updated as I go.
I am still concerned about the mechanical hum the transformer makes, however the vendor seems to think (as did someone else in this thread) that its not the cause of my excessive audio signal path hum.
Once I have the voltages I will speak to the suppler about solutions to test/fix. I will keep everyone updated as I go.
