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Little Dot Tube Amps: Vacuum Tube Rolling Guide - Page 248

post #3706 of 7319

man, do some searching on ebay, you get a lot of choices, dual mono, dip adapter, new used (used?) lol

post #3707 of 7319
Well it is with a heavy heart that I have to report that I have removed my strapping switches from the MK IV. The past while I have had this hum in the background and every tube I put in seemed to be very microphonic. Enough was enough, I totally disassembled the MK IV tonight, removed my switch array, cut the ends off of ALL the factory wires, restripped and retinned them all and put it back together. When I powered it up this time the background was black, not a bit of hum to be found. I'll just have to strap the old way and all will be good.

Too bad as it was really convenient to have the switches, I used shielded wire and even ran grounds to the shield which sort of alleviated some of the hum but not all. Three times this weekend I had it apart and the last time was the end.

So the back chassis is too far to run pin wires in my humble opinion and I was not going to drill into the front case as that is a thick piece of aluminium, and I know it would look like dogs dinner on the MK IV.
beerchug.gif
post #3708 of 7319
Quote:
Originally Posted by TrollDragon View Post

Well it is with a heavy heart that I have to report that I have removed my strapping switches from the MK IV. The past while I have had this hum in the background and every tube I put in seemed to be very microphonic. Enough was enough, I totally disassembled the MK IV tonight, removed my switch array, cut the ends off of ALL the factory wires, restripped and retinned them all and put it back together. When I powered it up this time the background was black, not a bit of hum to be found. I'll just have to strap the old way and all will be good.



Too bad as it was really convenient to have the switches, I used shielded wire and even ran grounds to the shield which sort of alleviated some of the hum but not all. Three times this weekend I had it apart and the last time was the end.



So the back chassis is too far to run pin wires in my humble opinion and I was not going to drill into the front case as that is a thick piece of aluminium, and I know it would look like dogs dinner on the MK IV.

beerchug.gif

 



With mk II it's short way from front panel. EF95, EF92 and 7-2 strap works via switches without any extra hum or noise, but 7-1 hums. It could be something from chassis and switches. I even changed wall socket to safe ground model and no help.
post #3709 of 7319
Quote:
Originally Posted by Artsi View Post
 
Quote:
Originally Posted by TrollDragon View Post

Well it is with a heavy heart that I have to report that I have removed my strapping switches from the MK IV. The past while I have had this hum in the background and every tube I put in seemed to be very microphonic. Enough was enough, I totally disassembled the MK IV tonight, removed my switch array, cut the ends off of ALL the factory wires, restripped and retinned them all and put it back together. When I powered it up this time the background was black, not a bit of hum to be found. I'll just have to strap the old way and all will be good.



Too bad as it was really convenient to have the switches, I used shielded wire and even ran grounds to the shield which sort of alleviated some of the hum but not all. Three times this weekend I had it apart and the last time was the end.



So the back chassis is too far to run pin wires in my humble opinion and I was not going to drill into the front case as that is a thick piece of aluminium, and I know it would look like dogs dinner on the MK IV.

beerchug.gif

 



With mk II it's short way from front panel. EF95, EF92 and 7-2 strap works via switches without any extra hum or noise, but 7-1 hums. It could be something from chassis and switches. I even changed wall socket to safe ground model and no help.


Yes that is strange indeed, have you tried soldering the 7-1 wires to them selves just off the switch as a test? I had radio signals coming in on mine for a bit today as I was moving the switch wires around with the back cover off. Placement of the wires has a great infulence on the hum and the capacitance in your fingers does too as you come close to the wires or move them.

 

Good that yours works, I didn't use 7-1 very much myself, I am not sure it you do so it might not be a problem.

 

Looking forward to seeing your Octal Conversion!

 

The Octal's are starting to get a little big in size, might be time to look into a Darkvoice 336SE or a La Figaro 336C the point to point wiring on them and the open bottom is so much easier to work on and I really do like the look of those Tung Sol 5998's in the power supply. :D

post #3710 of 7319
Quote:
Originally Posted by TrollDragon View Post
 


Yes that is strange indeed, have you tried soldering the 7-1 wires to them selves just off the switch as a test? I had radio signals coming in on mine for a bit today as I was moving the switch wires around with the back cover off. Placement of the wires has a great infulence on the hum and the capacitance in your fingers does too as you come close to the wires or move them.

 

Good that yours works, I didn't use 7-1 very much myself, I am not sure it you do so it might not be a problem.

 

Looking forward to seeing your Octal Conversion!

 

The Octal's are starting to get a little big in size, might be time to look into a Darkvoice 336SE or a La Figaro 336C the point to point wiring on them and the open bottom is so much easier to work on and I really do like the look of those Tung Sol 5998's in the power supply. :D

I have not missed 7-1 strap, so haven't used more time to solve hum problem.

 

I have been thinking 6A6 tubes as power. :eek: They should be big enough for BOXZILLA. Heater pins are 4mm thick and others 3.2mm. This is going to be some serious tube rolling. There aren't many big tubes that use suitable heater current.

post #3711 of 7319
Quote:
Originally Posted by Artsi View Post
 

I have not missed 7-1 strap, so haven't used more time to solve hum problem.

 

I have been thinking 6A6 tubes as power. :eek: They should be big enough for BOXZILLA. Heater pins are 4mm thick and others 3.2mm. This is going to be some serious tube rolling. There aren't many big tubes that use suitable heater current.


The 6N7 is the version with an Octal base but like the 6A6 it is a common cathode tube, I don't know how you would use it as a power tube without major board rework.

post #3712 of 7319
Quote:
Originally Posted by TrollDragon View Post
 


The 6N7 is the version with an Octal base but like the 6A6 it is a common cathode tube, I don't know how you would use it as a power tube without major board rework.

6A6 and 6N7 could be nearly impossible to get to work. Since they do not have separate cathodes. If i have understood right, little dot uses double triode powertube somehow like serial? :confused:

post #3713 of 7319

I'm sticking with the regular power tubes lol! I doubt I'd find anything much better than what I have now anyway... Besides, now that I've been reminded of the sheer size of those octal double triodes -no wonder they call the later tube types "miniatures"- my heart is wavering... Progress & testing new grounds, or "stick with what you have"? I have a feeling, the latter option may not get much love though lol...

 

OK, this time for real, I'm selling my father's (or my secondary, depending) Little Dot MK IV SE.

 

http://www.head-fi.org/t/687709/little-dot-mk-iv-se-220v-tube-headphone-amp-preamp-eu-sale-no-customs

 

Just putting it out here in case anyone is interested; most of you couldn't care less since you don't live in Europe though... But anyway, for the European head-fiers that might be interested.

post #3714 of 7319
^^There is the great deal on an SE for you MIKELAP! Resolder two wires on the back panel and she's good to go for 120V. With super tubes already installed to boot!
post #3715 of 7319
Quote:
Originally Posted by TrollDragon View Post

^^There is the great deal on an SE for you MIKELAP! Resolder two wires on the back panel and she's good to go for 120V. With super tubes already installed to boot!

Looks like 250 euro is $360.00 canuck dollars !!!!!!!!!!!!!!

 

post #3716 of 7319

Hi AFB and Gibosi,

 

My retired engineering friend (78 years old and going strong!) came to the rescue and wired and soldered the Vector adapters to a 9 pin socket. The design is similar to AFB's flying tube, but more like a hanging tube. My friend does not think that the tube hanging upside down will affect anything. After some problems with a dead left channel that was traced to a soldering point everything finally works. I am really happy!

 

Right now I am listening to a Sylvania 12AX7A tube. All I can say is that in comparison with the best 6AV6 tubes this tube beats them hands down. First impression is MORE of everything: more bass, more midrange, more treble, more musicality, more detail, more soundstage, more dynamics. It is like this tube has much more energy than what I experienced before. What is striking at this early stage is the bass slam, dynamics, and and the midrange warmth.

 

I have to apologize to AFB for asking what the advantage is of the the 12A7 tubes over the 6AV6 tubes which are supposed to be one half of a 12A7 tube.

 

Now to the nitty gritty: If I understand correctly I could connect a 6 Volt tube such as the 6BQ7 without any changes to the wiring except connecting pins 8 and 9 on the tube itself to eliminate ground hum. Is this correct?

 

Next question: Post #3645 by Gibosi and AFB is a wiring instruction table for using 12A7 tubes. (Many thanks!) Looking at Gibosi's amp on post #3625 it seems to me that right and left is the opposite of post #3545. In post #3545 the left channel has five connections to the the adapter, and the right adapter has three connections.

It seems to me that the picture on Post #3525 has the opposite; the left channel has three connections, and the right channel 5 connections.

 

Did I see correctly, and if so, what is the correct way of right and left?

 

PS: I asked my friend why the Vector adapters are designed to be so difficult to work with. He replied that by making them basically unsuitable for taking apart they could sell more adapters after you got stuck and could not put it together again....

post #3717 of 7319
Quote:
Originally Posted by mordy View Post
 

Now to the nitty gritty: If I understand correctly I could connect a 6 Volt tube such as the 6BQ7 without any changes to the wiring except connecting pins 8 and 9 on the tube itself to eliminate ground hum. Is this correct?

 

First, congratulations! :)
 
The necessary changes have to do with the heaters. For 12AX7 tubes, pin 9 functions as part of the heater circuit.  For 6BQ7 tubes, pin 9 functions as a shield between the two triodes. Currently, for the 12AX7, you have pin 9 connected to either pin 3 or pin 4 on the adapter. (Probably pin 4 if you used post #3645). Further, you tied tube pins 4 and 5 together and connected both of them to pin 3 on the adapter.. 
 
To switch to the 6BQ7:
 
Untie tube pins 4 and 5.
Connect tube pin 4 on the socket to pin 3 on the adapter.
Connect tube pin 5 on the socket to pin 4 on the adapter.
    Now you have the heaters connected correctly

 

Disconnect tube pin 9 from pin 4 on the adapter
Tie tube pins 8 and 9 together
    Now you have the shield grounded properly.
 

Quote:
Originally Posted by mordy View Post
 

Next question: Post #3645 by Gibosi and AFB is a wiring instruction table for using 12A7 tubes. (Many thanks!) Looking at Gibosi's amp on post #3625 it seems to me that right and left is the opposite of post #3645. In post #3645 the left channel has five connections to the the adapter, and the right adapter has three connections.

It seems to me that the picture on Post #3625 has the opposite; the left channel has three connections, and the right channel 5 connections.


Yes, I can see that this might be confusing. Five connections equals the triode (3 connections) plus the heaters (2 connections). I don't think it really matters which side you use to supply current to the heaters, left or right. Use which ever side is more convenient.
 
 


Edited by gibosi - 10/27/13 at 6:30pm
post #3718 of 7319

Here is the listening station for the next two and a half weeks... I will be sad when the LCD 3's have to go on to the next lucky recipient, so they will be well enjoyed while I have the opportunity.


And now back to your regularly scheduled Dual Triode rolling. :D

post #3719 of 7319

Hi Gibosi,

 

Thanks for your answer and instructions. Just to clarify, do I only need to change one of the adapters?

 

 Seems that tube pin 4 and socket 3 already are in place - only that the lead for tube pin 5 also goes to socket 3?

 

Connecting tube pins 8 and 9, can I just wrap a 30 gauge wire wrap wire around the pins, or do they have to be soldered?

post #3720 of 7319
Quote:
Originally Posted by mordy View Post
 

 

Thanks for your answer and instructions. Just to clarify, do I only need to change one of the adapters?

 

Seems that tube pin 4 and socket 3 already are in place - only that the lead for tube pin 5 also goes to socket 3?

 

Connecting tube pins 8 and 9, can I just wrap a 30 gauge wire wrap wire around the pins, or do they have to be soldered?

 

For your 12AX7, both tube pins 4 and 5 are connected to socket 3. To use your 6BQ7, the lead for tube pin 5 must be disconnected from socket 3 and connected to socket 4. And tube pin 9 must be disconnected from socket 4 and connected to tube pin 8.

 

These connections do not have to be soldered as long as you have a very tight mechanical connection.

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