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Little Dot Tube Amps: Vacuum Tube Rolling Guide
Jul 17, 2015 at 4:29 PM Post #9,736 of 13,432
To my ears the 6HM5 is the best 7 pins i've used for my MK III and 1+  and the best tubes for me so far is the C3g/6SN7 combo,maybe he/she should try C3g.
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Jul 17, 2015 at 5:11 PM Post #9,737 of 13,432
meddlesome duck said:
  I mentioned earlier I was having issue with some EF91 tubes in my little dot i+ well the seller has sent me a second pair of tubes next day delivery. I'm trying them now and it's the same problem. The sound is very quiet I have to set my source to 100% and my little dot to 20% in order to get decent level for listening and even then the bass is not really there and the highs clip slightly. If I increase the little dot's volume everything slowly starts clipping. Has anyone encountered a similar issue, the pins again are slightly dirty, the tubes are CV5377.
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Since you have experienced this with two sets of EF91 tubes, I doubt that the tubes are at fault. I now suspect that the J1 and J2 jumpers are not making a good contact. And there is a way you can test this. First you will need two short pieces of small gauge stranded wire, 22 gauge or smaller. Strip both ends and in each socket insert one end in pin-hole 6 and the other in pin-hole 7. Do this in both sockets. And then carefully insert your tubes. This is precisely what the J1 and J2 jumpers do, they strap 6 and 7 together.
 
Scroll to the bottom of Acapella11's post below, for pictures and diagrams to help you understand "strapping pins together in the socket.". Also, note that in the the LD 1+, the sockets are mirrored, left to right, whereas, in the LD III and IV, they have the same orientation, left to right.
 
http://www.head-fi.org/t/563884/little-dot-tube-amps-vacuum-tube-rolling-guide/1140#post_9392055
 
After strapping, if the tubes sound good, then J1 and J2 are not making good contact, and you might want to open your amp up and clean them and also make sure the jumpers are tight and secure.
 
Good luck! :)
 
Edit: Ummm... You did open your amp up and jumper J1 and J2 before running your EF91?, didn't you?
 
Jul 17, 2015 at 8:41 PM Post #9,738 of 13,432
gibosi said:
  Edit: Ummm... You did open your amp up and jumper J1 and J2 before running your EF91?, didn't you?
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Hi gibosi,
 
Thanks for the reply, referring to the little dot i+ reference guide it says I should have both jumper J1 and J2 closed for EF91 tubes.
On a second glance at the amp I've noticed the gain is currently running in an open circuit which is probably too high for my fidelio x2's I also noticed two yellow wires connecting both tube sockets. I bought this amp pre-owned and the guy I bought it off never mentioned any modifications to the amplifier. The jumper housing is missing so I can't alter the gain for the moment I've had to order housing online. Below is a picture of my amp.
 
Green: J3 + J4 (Gain)
Purple: J1 + J2 (Housing installed)
Red: Mystery wire
 
Picture of my amp
http://postimg.org/image/j7vxsdlfj/
 
little dot i+ Reference Guide
https://dl.dropboxusercontent.com/u/6037680/Little%20Dot%20I%2B%20Reference%20Guide.pdf
 
Jul 18, 2015 at 12:09 PM Post #9,741 of 13,432
gibosi said:
  Edit: Ummm... You did open your amp up and jumper J1 and J2 before running your EF91?, didn't you?
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Thanks for the reply, this is terribly embarrassing, I bought this amp second hand, the jumpers for gain control were missing which the pins are soldered directly onto the circuit board. J1 and J2 have plastic at the bottom of the pins before they touch the circuit board. I mistook these pieces of plastic as the jumpers. Oh dear, I realised last night on closer inspection when I tried to remove what I thought were jumpers.
 
The tubes are sounding great I no longer have a slight buzzing sounds in the background, everything is very clear now.
 
Appreciate the help.
 
Jul 18, 2015 at 4:24 PM Post #9,743 of 13,432
meddlesome duck said:
 
On a second glance at the amp I've noticed the gain is currently running in an open circuit which is probably too high for my fidelio x2's I also noticed two yellow wires connecting both tube sockets. I bought this amp pre-owned and the guy I bought it off never mentioned any modifications to the amplifier. The jumper housing is missing so I can't alter the gain for the moment I've had to order housing online. Below is a picture of my amp.
Click to expand...

 
The yellow wires power the tube heaters. The heater supply circuit is completely separate from the circuitry that actually runs the amplifier. While I haven't popped my amp open in a long time, everything looks normal to me.
 
Jul 20, 2015 at 8:46 AM Post #9,746 of 13,432
mimart7 said:
Sadly, my wife tells me to stop buying tubes.  I guess I have my purchases shipped to work, lol.
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My wife bought me this amp through the current massdrop promotion. She had no idea what tube rolling was. I'll be recieving all my tubes at work:)
 
Jul 20, 2015 at 10:16 AM Post #9,748 of 13,432
My wife asked me why I have so many of those little glass things - didn't really know what to answer, so I told her that they are all a little different, and I am looking for audio perfection....
 
Funny thing is that they seem to appreciate in value, but unfortunately not so easy to sell LOL
 
Jul 21, 2015 at 7:00 AM Post #9,749 of 13,432
I just received my second set of tubes, Canadian made northern electric NE-408A. I'm very surprised what a difference they have made, it blows both the stock 6J1 and the EF91 CV3577 out the water. Using Philips Fidelio x2 I christened them with the track Elegia by new order, the first minute of the track fades in with low bass tones with the EF91's It generates a subwoofer style bass that's very airy and somewhat irritating, the 408A's dials this way down, it actually allows the bass to build up and when it does it's very tight and clean, the mids and highs are very clear now too. During the middle of the track you have a few voices in the background which are very faint I could barely make these out with the EF91's genuinely forgot about these until last night, the 408A's made them stand out thought I could hear someone whispering in my ear very creepy. Overall it's a very bright tube and I absolutely love them, these will definitely be my daily drivers from now on. Now just eagerly awaiting my next batch of tubes the Russian made 6HM5 which where mentioned in previously in this thread.
 
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Jul 31, 2015 at 5:12 AM Post #9,750 of 13,432
Hello all,
 
First of all, thanks for this topic on wich we can find a huge amount of information concerning tube rolling !
 
I've recently bought a Little Dot I+ for my AKG Q701. I've bought it with the standard 6J1 tubes and I found it souded great !
 
Following the comments of many people I decided to buy a pair of Voskhod 6ZH1P-EV. I've also ordered an OPA2107 that I'm still waiting for.
 
I've received the voskhod yesterday and I must say that I'm a bit disappointed about them. In fact, the mids and trebles are really detailed, and more "clean" than the 6J1, but I also find that there is less bass than with the 6J1, and maybe too loud high-mids. It is exactly what are, from my point of view, the 2 weak points of the Q701.
 
But what is strange is that I read that Voskhod have really good bass, so I wonder why for the moment I found the bass less present than with the standard 6J1 ? Do they need some burn in ?
 
Or maybe the Voskhod are well adapted for Sennheiser earphones, but less for AKG ?
 
What do you think ?
 
Thanks for your help. :wink:
 
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