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Little Dot Tube Amps: Vacuum Tube Rolling Guide - Page 243

post #3631 of 10489
Hi. I just bought a pair of GE jan 5654 w tubes from nostubestore.com , there is quite an obvious humming noise when the music is not playing. Is this because I did not put the tubes in properly? I'm using the little dot 1+. Thanks
post #3632 of 10489
Quote:
Originally Posted by MRpilgrim View Post

Hi. I just bought a pair of GE jan 5654 w tubes from nostubestore.com , there is quite an obvious humming noise when the music is not playing. Is this because I did not put the tubes in properly? I'm using the little dot 1+. Thanks
What tubes did you have in before? Did you check your manual for the proper jumper settings for that type of tube?

Dirty pins on the tube not making good contact could be the cause as well.
Edited by TrollDragon - 10/21/13 at 10:12pm
post #3633 of 10489
I was using the stock Chinese 6J1 tubes. Both of then use the same EF95 setting.
post #3634 of 10489
them*
post #3635 of 10489

Box seems to need one improvement. To get rid of humming with 6DJ8 and 6922 tubes Pin9 needs to be connected to right channel cathode, Pin8. I'll add it via extra switch to free connector of already connected 9pin switch. Left channel cathode did not help at all.

400

post #3636 of 10489

I wouldn't worry too much about heater current on our amps with double triodes. I used pairs of 0.3A+ tubes for months without issues (actually 0.3A heaters the minimum I would consider using for pentodes and single triodes, I often used 0.4 and 0.45A tubes, so a total of 0.9A), so 0.6 to 0.9A total driver heater current. The tubes we're looking at now have pretty petty heaters compared to what we've been using lol!

 

Interestingly, and despite the high gain of the 12AX7 tube I'm using, I find that the amp runs pretty cool compared to my previous standards. And that can't be a bad thing!

 

So, I guess we've reached a temporary conclusion on what to do with the shield on 6DJ8 tubes huh? Great, now I can get started on my soldering work.

 

Btw, I've just added a large amount of tubes of all types to my selling thread; just putting it out here in case someone's interested (there's a pretty large array of choices there lol).

 

http://www.head-fi.org/t/671097/little-dot-driver-tubes-ef95-ef92-ef91-more

 

There's also a thread below that one in the classifieds with my last DR supertubes; if anyone wants a "glory package" along with nice driver tubes... I might also have a MK IV SE unit for sale in a few weeks, if someone is looking for an even more glorious package lol. It's not mine, but my father's, who hasn't used it much apart from the preamp section and doesn't see the point of keeping it (so, it doesn't have loose driver sockets like mine does lol).

post #3637 of 10489
Quote:
Originally Posted by mordy View Post
 

Hi Gibosi,

 

I like your idea of using connections that do not need to be soldered to try things out. From the pictures I gather that you are using one 6DJ8 tube for both channels, whereas in the past I always saw two tubes being used.

 

I have one each of the 6BS8 and 6BQ7 tubes. Can these tubes be used singly without cutting any pins (the same as the 6DJ8)?

 

I found it difficult to put together the Vector adapter after I took it apart. I assume that you took it apart to wire the adapter. What kind of crimp on pins could I use on the Vector adapter to avoid disassembling it?

 

Hi Trolldragon,

 

Would the above mentioned 6V 6BS8 and 6BQ7 tubes with a rating of 0.40 A be safe to use with the Little Dot MKIII?

 

First, as has been noted by others, many of us have been using Tung-Sol 6485 / 6AH6 for quite some time, which draw .45 amps, and I am not aware of any problems. However, given TrollDragon's post, to be on the safe side, I think I will consider .45 amps to be the upper limit for me. And given that so many of us have used our Tung-Sols with no issues, I believe the 6BQ7 (which is the same as 6BS8 and 6BZ7), with .4 amps, should not be a problem. However, I can assure you, the 6DJ8 and 12AX7 will sound much better and have the additional benefit of a lower current draw. So your current tubes are fine to experiment with, but I encourage you to move on to these better tubes in the future.  

 

And yes, the Vector adapters are a pain to reassemble. I loosened the screw and pulled them apart only a fraction of an inch, just enough to allow me to thread a wire through the eye of the test point tab. I twisted the wire tightly several times, and then, once the adapter was screwed back together, I have a secure mechanical connection. (Sorry that the picture is not the greatest, but I think you can see what I have done.)

 

post #3638 of 10489
Quote:
Originally Posted by Artsi View Post
 

Box seems to need one improvement. To get rid of humming with 6DJ8 and 6922 tubes Pin9 needs to be connected to right channel cathode, Pin8. I'll add it via extra switch to free connector of already connected 9pin switch. Left channel cathode did not help at all.

 

I'm glad you tried the left channel cathode. I didn't think it would work as the ground hum was in the right channel, but it is good to have this confirmation. :)

post #3639 of 10489
Quote:
Originally Posted by gibosi View Post
 

 

I'm glad you tried the left channel cathode. I didn't think it would work as the ground hum was in the right channel, but it is good to have this confirmation. :)

There was little hum with left channel too, but not like right. I've been listenin nearly all the time with 6N2P-EV -76 and i'm very very happy with this cheap one. 6N2P does not hum and i can't notice any difference in sound if my shield-ground-switch is on or off. This was the tube which made me nearly cry and i think it is still getting even better with more on time.

 

I bought this cheap bastard from here http://www.ebay.co.uk/itm/130967121083.

post #3640 of 10489
Quote:
Originally Posted by Artsi View Post
 

There was little hum with left channel too, but not like right. I've been listenin nearly all the time with 6N2P-EV -76 and i'm very very happy with this cheap one. 6N2P does not hum and i can't notice any difference in sound if my shield-ground-switch is on or off. This was the tube which made me nearly cry and i think it is still getting even better with more on time.

 

I bought this cheap bastard from here http://www.ebay.co.uk/itm/130967121083.

 

I have four of these coming to me, veryyyy slowly, from Tbilisi, Georgia, and I am very glad to know they sound good. :)

 

I found one person who tried them in his Schiit Lyr, and he said they were terrible! lol But I think the LD is much more flexible than the Lyr when it comes to tube rolling....  

post #3641 of 10489

I thank everybody for answering my questions - thanks.

 

Hi Gibosi,

 

I am getting in a 9 pin socket with tabs underneath that have holes in them. Using Gibosi's wire wrap method I think I could make a temporary set up without soldering. I have a 12AX7 tube to try.

 

What I need is simple instructions how to route the wires. The Vector adapters have numbers printed on them. The 9 pin socket can be numbered underneath left to right 1-9, where 1 is starting at the pin gap left.

 

Something like: Vector left adapter (VL) #2 to Tube (T) #3 or VL2 to T3 and so on. Vector right tube would be VR etc.

 

Is the wiring for 12AX7 different than the wiring for 6DJ8?

post #3642 of 10489
Quote:
Originally Posted by mordy View Post
 

I thank everybody for answering my questions - thanks.

 

Hi Gibosi,

 

I am getting in a 9 pin socket with tabs underneath that have holes in them. Using Gibosi's wire wrap method I think I could make a temporary set up without soldering. I have a 12AX7 tube to try.

 

What I need is simple instructions how to route the wires. The Vector adapters have numbers printed on them. The 9 pin socket can be numbered underneath left to right 1-9, where 1 is starting at the pin gap left.

 

Something like: Vector left adapter (VL) #2 to Tube (T) #3 or VL2 to T3 and so on. Vector right tube would be VR etc.

 

Is the wiring for 12AX7 different than the wiring for 6DJ8?

 

I have yet to get a 12AX7 so I haven't really sat down to work it out exactly. However, the only difference in how we connect the 6DJ8 and the 12AX7 is the way the heaters, tube pins 4, 5 and 9 are connected.  But this will get you started.  And if someone else can tell us how to connect the heaters, that would be great.

 

9-pin socket           left LD socket        right LD socket
 
1 plate triode 1                5                        
2 grid triode 1                  1
3 cathode triode 1            2
4 heater                          ?                         ?
5 heater                          ?                         ?
6 plate triode 2                                           5
7 grid triode 2                                             1
8 cathode triode 2                                       2
9                                    ?                         ?


Edited by gibosi - 10/22/13 at 7:42am
post #3643 of 10489
Quote:
Originally Posted by gibosi View Post
 

 

I have yet to get a 12AX7 so I haven't really sat down to work it out exactly. However, the only difference in how we connect the 6DJ8 and the 12AX7 is the way the heaters, tube pins 4, 5 and 9 are connected.  But this will get you started.  And if someone else can tell us how to connect the heaters, that would be great.

 

9-pin socket           left LD socket        right LD socket
 
1 plate triode 1                5                        
2 grid triode 1                  1
3 cathode triode 1            2
4 heater                          ?                         ?
5 heater                          ?                         ?
6 plate triode 2                                           5
7 grid triode 2                                             1
8 cathode triode 2                                       2
9                                    ?                         ?

 

Easy!

 

Just connect pins 4+5 to one the B7G socket heater pins (let's say pin 3 for instance) and connect pin 9 to the other B7G heater pin on the same socket (so pin 4 in this case). And, voila, you get paralleled 6V-fed heaters instead of the typical 12V in series (heaters work the same in both scenarios).

 

That's also the good thing about the 12Ax7 types is that nothing forbids us from only using one heater (pin 4 or 5, depending on triode to heat, would be routed to B7G pin 3, and pin 9 would still go to B7G pin 4), and leaving the other hanging without eventual cathode poisoning.

 

Like I said: easy! (and no possible shield issues, like on 6DJ8 tubes...)

post #3644 of 10489
Quote:
Originally Posted by gibosi View Post
 

12AX7

 

9-pin socket           left LD socket        right LD socket

 
1 plate triode 1                5                        
2 grid triode 1                  1
3 cathode triode 1            2
4 heater                          3                         
5 heater                          3                         
6 plate triode 2                                           5
7 grid triode 2                                             1
8 cathode triode 2                                       2
9                                   4

 

Updated to per AFB. :)


Edited by gibosi - 10/22/13 at 9:59am
post #3645 of 10489
Quote:
Originally Posted by gibosi View Post
 

 

Just an update. With all these wires flying around, this arrangement is rather susceptible to picking up RF noise. Fortunately, moving it a few inches often helps, and after all, since this is a prototype, it is very acceptable until I can build a proper adapter box.

 

Also, I am happy to report that I was able to straighten the bent pins on one of my Bugleboys and it works fine.... Life is good. :)

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