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Little Bear p-2 chinese tube amp with new IRF510 mosfets sounds good but...

post #1 of 12
Thread Starter 

This amp is like the Bravo v-2 except it has a switch for 6 or 12 series tubes so it should have a greater choice in tube rolling.  Mine has a GE 5814 tube but I don't know how good(or bad) this tube is vs other options out there for a reasonable price.  The new mosfets fix the rolled off highs problem, now I'm wondering if a better tube would make as big a difference.  Has anyone tried another tube(or other mod) that has made as big a difference?

post #2 of 12
I have the p-1 amp with the same tube, so far I have installed the irl530s the lm317a and nichicon audio grade caps. The output caps help extend the bass. I only used the 5814 tube the first night and haven't touched it since. If your up for some tube rolling, you'll be surprised at the differences they can make.

This is my first amp and decent headphones, so I wasn't sure if I would even be able to hear any differences. But after about two months now I have 4 sets of headphones and a pair of senngrados I put together, and can easily tell the differences the tubes can make.
For tubes I have:
A Amperex bugle Boy, it gives a a richer fuller sound with better base
A RCA clear top which is very clean and clear, low bass
A RCA long black plate ( organ pull ) a lot like the bugle boy but slightly cleaner
A tung-sol black glass with the black plates, the bass is heavy and cuts back on the highs
I also have about a dozen others now but the above have become my goto tubes.

The 6 volt tubes have a little more buzz to them whereas the 12 volt tubes seem to run a bit cleaner, but at volume you really can't tell. You will find that certain tubes will fit better with certain headphones and types of music.

The little bear may not be the best, but it's been a lot of fun to start out with. And if your up for some tube rolling I think you'll really enjoy the experience. Beware though, it's like a gate way drug, or lays chips, once you start it's hard to stop. smily_headphones1.gif
Edited by TroyS - 7/18/14 at 4:14pm
post #3 of 12
Thread Starter 

Awesome man!  I've also got the Schiit Vali with HE-400 cans so the p-1 is an experiment in progress.  What exactly is a lm317a?  The HE-400's are a bit bright sounding so something thats a bit softer would balance those.  I've ordered a Mullard 12ax7 from Amazon so we'll see how that sounds.  I'll also check out the tubes you've mentioned.  It is a bit of a drug but hey, there are a lot worse addictions.  Happy listening.

post #4 of 12
I believe they are rectifiers, they look like the mosfets and are on the second set of heatsinks. From what I read they don't effect the sound quality but they were on the mod list so I replaced them while I was at it.

I have a Mullard 12au7, it is a lot like the bugle boy, a fuller bassier sound. That should work well for you.

I've been looking at the schiit modi with the optical input as my next step. I just picked up a 2009 Mac mini for my music player, so it has been a busy couple of days learning how to set it up headless and remote control it.

I'm gonna need a second job at the rate I'm going.
post #5 of 12
Thread Starter 

One of the things I've noticed vs the Vali is a reduction in channel separation.  It's not huge but noticeable on some material.  The Vali still wins but it's not by much.  I'm using a Fiio x-3 as my source which sounds pretty good on it's own.  When I plug in the tube amp, I use the line out not the headphone out because it sounds better...you're essentially bypassing the amp in the x-3 and just using it as a DAC.  I'll post something when I get the Mullard 12ax7 on it's sound signature.  thanks for your input.

post #6 of 12
Thread Starter 

Well the Mullard 12ax7 was a bust...didn't work at all.  I think it's just not compatible with the p-1(too much gain I think).  I've also got some vintage Sylvania 12au7's that sound GREAT!  In fact I now prefer it to the Vali!  The original GE 5814 tube would start to distort on musical peaks as it heated up.  The 12au7's sound just right with a minor bias adjustment.  Just listening to some great music now!

post #7 of 12
Never tried the ax type, but the 12au7 works great. I have some sylvanias but haven't tried them in a while. Fun part is that a different set of cans may sound better with a different tube. I have a set of grado sr60 that I really like with the 12au7 rca black plates that come from organ pulls. On the senngrados I built I have to stick with the rca cleartops or the bass is way to strong.

Amazing what a cheap amp with a good tube and a little upgrading can sound like.
post #8 of 12
Thread Starter 

Did you put the irf510 in your amp or the irl530?  I put in the irf510 and I just read the irl530 gives more power and headroom so I ordered 5(it was cheaper to buy 5 than 2!) and will put them in when they arrive.  I'll let you know how the experiment goes...

post #9 of 12
I went with the IRL530, I believe the IRL510 had a higher range in the high frequency area.
post #10 of 12
Thread Starter 

Yeah .I put the irf510 in and apparently, the irl mosfets also lower distortion so I've just ordered some irl530's... it also makes the lm317 run hotter too.

post #11 of 12
Haha, those heatsinks get really toasty. I made the mistake of purposely touching them just to see how hot they really were.
post #12 of 12
Thread Starter 

I know, I've burned a finger or two especially on the lm317.  I use the amp with the plastic top off and have a little fan going to help keep it cool.  I also unplug the power supply when not in use as it stays warm and seems to draw current when the amp is off.  My Vali is the same way, the wall wart stays hot when it's plugged in whether the amp is on or not.  Saves a little energy too...

  I think we're using the same source for the modifications:

http://www.mediafire.com/view/?648rn66jncce788 is where I got my info.

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