Little Dot Tube Amps: Vacuum Tube Rolling Guide
Dec 22, 2014 at 9:39 PM Post #8,762 of 12,779

mordy

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Hi siles1991,
 
Here is a quote that may be helpful:
 
"You mention that one of the stock tubes completely burnt out after two years. How do you know it burnt out? The reason I am asking is that I had the same experience. However, for some reason I saved it.
A year later on a hunch I took out my little pocket knife and and scraped clean the pins on the bad tube. Pushed it back in, and you wouldn't believe it! It lit up again and works fine. Looks like a little corrosion made it stop working.
 
About the IR tubes: Although they are rated for 500 hours, and the regular 6N6P tubes for 3000 hours, I agree with the posts that state that this is for severe military working conditions (maybe in a MIG fighter plane).  IMHO they should last much longer in a little quiet preamp...."
 
I used my own 6N6P-IR extensively for around 18 months. After that I switched to what I consider to be better tubes. Tried the 6N6P-IR as a driver with a breadboard and the Vector adapters. I was surprised to hear that one channel was much lower in volume on both tubes - did not notice this when used as power tubes.
 
 If the tube turns white inside instead of silver, this is a sure sign that you lost the vacuum and the tube is finished. If it looks normal, try scraping the pins gently in case they oxidized.
 
Dec 22, 2014 at 10:15 PM Post #8,763 of 12,779

siles1991

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  Hi siles1991,
 
Here is a quote that may be helpful:
 
"You mention that one of the stock tubes completely burnt out after two years. How do you know it burnt out? The reason I am asking is that I had the same experience. However, for some reason I saved it.
A year later on a hunch I took out my little pocket knife and and scraped clean the pins on the bad tube. Pushed it back in, and you wouldn't believe it! It lit up again and works fine. Looks like a little corrosion made it stop working.
 
About the IR tubes: Although they are rated for 500 hours, and the regular 6N6P tubes for 3000 hours, I agree with the posts that state that this is for severe military working conditions (maybe in a MIG fighter plane).  IMHO they should last much longer in a little quiet preamp...."
 
I used my own 6N6P-IR extensively for around 18 months. After that I switched to what I consider to be better tubes. Tried the 6N6P-IR as a driver with a breadboard and the Vector adapters. I was surprised to hear that one channel was much lower in volume on both tubes - did not notice this when used as power tubes.
 
 If the tube turns white inside instead of silver, this is a sure sign that you lost the vacuum and the tube is finished. If it looks normal, try scraping the pins gently in case they oxidized.

ok i,ll try cleaning the pins and try again thanks for the info
 
Dec 23, 2014 at 3:07 PM Post #8,765 of 12,779

MIKELAP

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If anybody is looking for loctal sockets good ones TUBE DEPOT has them $4.95 each hopefully they still have them in stock                                                     https://www.tubedepot.com/products/8-pin-loctal-socket-4cx250b-4cx400a-etc
 
Dec 23, 2014 at 4:45 PM Post #8,766 of 12,779

Acapella11

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Hi, Just for Christmas I have put together a table as a reminder for everyone in the thread  and to help new arrivals. The table is now pretty much complete.
 
Please, let me know if you find any additions or anything that requires correction.
 
Little Dot I" / II/ III / IV Endgame Tube Table
 
Power Tube   
NameAdapterHeater Current (A) / 6.3 VNotes
5687/7044/7119(E182CC)5687 Powersocket Adapter 0.9easily usable substitutes, sound great
6AS7G/6080Adapter + External Power Supply, see 1 and 2 and 32.5this is probably the icing of the power tube cake
12AU7/12AT7/12AX7/7025/5751/ECC83/6057Powersocket Adapter0.35 
6BL7/6BX7/6BQ7Adapter + External Power Supply, see 1 and 2 and 31.5 
6DJ8not needed0.365 
6GU7/6CG7/6FQ7not needed0.6not compatible with 12AX7 driver tubes
6N23Pnot needed0.31 
6SL7*6SN7 Powersocket Adapter0.3lower gain than 6SN7, not compatible with low impedance cans
6SN7*6SN7 Powersocket Adapter0.6classic high end tube, not compatible with low impedance cans
6N6P-IRnot needed0.9high quality, long lasting version of the 6N6P-I and considered best sounding 6N6P before the very expensive 6N6P-DR
    
Maximum recommended heater current for power tubes is 1.0 A. Tubes exceeding this are highlighted in red.  
    
Driver Tube   
NameAdapterHeater Current (A) / 6.3 VNotes
5687/7044/7119(E182CC)External driver socket ^, external power supply0.96.3 V / 12.6 V **
6350/6463/ECC813External driver socket ^, external power supply0.96.3 V / 12.6 V**
2C51 / 396A / 5670External driver socket ^ + driver socket adapter0.35 
7AU7External driver socket ^0.63. 5 V / 7 V**
12AU7External driver socket ^0.36.3 V / 12.6 V**
12AU7/12AT7/12AX7/7025/5751/ECC83/6057*External driver socket ^0.3One triode can be used besides a non-powered one, 6.3 or 12.6 V**
6BQ7AAdapter0.4 
6DJ8External driver socket ^0.365probably noisiest double triode, both triodes must be powered
6HM5none0.19probably best standard AK5-type option
6N23Pnone0.31 
6SL7*6SL7 driver adapter0.3 
6SN7*External driver socket ^, external power supply0.6 
C3G(S)* ^^C3G AK5 Adapter0.37C3G(S) tubes sound great but they are produced with a fragile glass base. Widen the socket holes before inserting the tube to avoid breaking.
ECC81External driver socket ^0.3 
ECC40External driver socket ^, external power supply0.6 
E80CC/6085External driver socket ^, external power supply0.6 6.3 V / 12.6 V **
    
Maximum recommended heater current for driver tubes is 0.4 A. Tubes exceeding this are highlighted in red.
 
   
*: Requires socket extenders for LD MKIII": For Little Dot I only driver tubes.  
9 Pin power socket extender   
7 Pin driver socket vector extender   
**: Generally, when doubling the voltage, the apparent current is halved.  
^: The external driver socket adaper uses a breadboard and allows the use of a single double triode to drive both channels. 
^^ Hypnos1 (post 5670): How to remove the C3Gs metal shielding, this requires care to not break the fragile tubes.
 
   
Power Tube Requirements (Gibosi post #7937)  
1) Double triode   
2) Separate cathodes (there are some double triodes such as the E90CC where the triodes "share" a cathode. These will not work.) 
3) Heater current 1.0A or less   
4) 6.3 Volts   
    
List of compatible tubes and 6DJ8, 6SL7, 6SN7, 12AX7 wiring instructions  
 
For old school driver tubes operable without adapter, see page 77.
 
Driver Tube 7-Pin Vector Socket Adapter
images

 
Power Tube 9-Pin Socket Adapter
mppIDOWNRlv0CVXOnF2cEgw.jpg

 
Revisions 1 & 2, 24/12/2014: Thanks for the input Gibosi and Mordy, thanks for sending the socket extender pictures Mordy, which are now included. Added a reference to Hypnos1 on how to remove the C3G(S) metal shielding.
Added ECC40 and E80CC/6085 as suggested by Gibosi, thanks.
Merry Christmas.
Revision 3, 09/01/2015: Added links to the implementation of 6AS7G/6080 power tubes, thanks Gibosi for finding the posts and suggesting the implementation and Mordy making it work. Added link to page 77 and 6N6P-IR.
Revision 4, 10/02/2015: Updated power tube links for 6080/6AS7G by Mordy's post 9059 on page 604 (3)
 
Dec 23, 2014 at 6:27 PM Post #8,767 of 12,779

i luvmusic 2

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  Hi, Just for Christmas I have put together a table as a reminder for everyone in the thread  and to help new arrivals. Please treat this as a alpha version of would be the final product but however I hope it provides useful data for everyone interested.
 
Please, let me know if you find anything that requires correction.
 
  Power Tube 
NameAdapterHeater Current (A) / 6.3 VNotes
5687/7044/7119(E182CC)5687 Powersocket Adapter 0.9great and simple 6N6P substitute
6AS7G/6080Adapter + External Power Supply2.5this is probably the icing of the power tube cake
12AU7/12AT7/12AX7/7025/5751/ECC83/6057Powersocket Adapter0.35 
6BL7/6BX7/6BQ7Adapter + External Power Supply1.5 
6DJ8not needed0.365 
6GU7/6CG7/6FQ7not needed0.6not compatible with 12AX7 driver tubes
6N23Pnot needed0.31low output
6SL7*6SN7 Powersocket Adapter0.3lower gain than 6SN7, not compatible with low impedance cans
6SN7*6SN7 Powersocket Adapter0.6classic high end tube, not compatible with low impedance cans
    
  Maximum recommended heater current for power tubes is 1.0 A. Tubes exceeding this are highlighted in red. 
    
  Driver Tube 
NameAdapterHeater Current (A) / 6.3 VNotes
568712AX7 double triode adapter, external power supply0.9 
6350/6463/ECC81312AX7 double triode adapter, external power supply0.96.3 V / 12.6 V
2C51 / 396A / 567012AX7 double triode adapter + driver socket adapter0.35driver socket adapter
7AU712AX7 doule triode adapter0.6 (parallel) 
12AU712AX7 doule triode adapter0.3 (parallel)6.3 V / 12.6 V
12AU7/12AT7/12AX7/7025/5751/ECC83/6057*12AX7 doule triode adapter0.3One triode can be used besides a non-powered one, 6.3 or 12.6 V
6BQ7AAdapter0.4 
6DJ812AX7 double triode adapter 0.365one of the noisiest double triods, both triods must be powered
6HM5none0.19probably best standard AK5-type option
6N23Pnone0.31low output
6SL7*6SL7 driver adapter0.3 
6SN7*12AX7 double triode adapter, external power supply0.6 
C3G(S)*C3G AK5 Adapter0.37 
ECC8112AX7 doule triode adapter0.3 
    
  Maximum recommended heater current for driver tubes is 0.4 A. Tubes exceeding this are highlighted in red. 
* Requires vector socket extender for MKIII   
9 Pin power socket vector extender   
7 Pin driver socket vector extender   
    
Power Tube Requirements (Gibosi post #7937)  
    
1) Double triode   
2) Separate cathodes (there are some double triodes such as the E90CC where the triodes "share" a cathode. These will not work.) 
3) Heater current 1.0A or less   
4) 6.3 Volts   
    
List of compatible tubes and 6DJ8, 6SL7, 6SN7, 12AX7 wiring instructions  

Thank You! for posting these it's very helpful.
beerchug.gif

 
Dec 24, 2014 at 7:50 AM Post #8,769 of 12,779

vic2vic

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  Hi, Just for Christmas I have put together a table as a reminder for everyone in the thread  and to help new arrivals. Please treat this as a beta version of would be the final product but however I hope it provides useful data for everyone interested.
 
Please, let me know if you find anything that requires correction.
 

 
WOW ! Amazing job. Page 585 is now the new "page 77" 
beerchug.gif

I need to change my fixed bookmark. 
cool.gif
 
 
Dec 24, 2014 at 1:30 PM Post #8,773 of 12,779

MIKELAP

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Dec 24, 2014 at 2:25 PM Post #8,774 of 12,779

hypnos1

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  I have finished my newest DIY amp. Sadly no headphone connect (yet?). I bought Russian 6F6S tubes because of this effect.

With 6F6S's around 2x13w triode connected and pentode connected 2x18w. So these small powertubes are giving their max. Of course this amp is designed for KT88's, and with them i get much more power. And here is the amp with 5U4G, 4 6F6's, 2 6SN7 and 12AV7.

I had so many different 12A*7 tubes from little dot times, so decided to use these as driver tube and they tolerate more voltage than 6DJ8. Transformers and choke are from old Hammond organ amplifiers. 4 inputs and again selector switch from old organ, since it was way better quality, than new small plastic knob. 6SN7's are connected as long-tailed-pair phase inverters. There is small switch for triode-pentode change behind powertubes. It seems to be mostly as for experimental and not for real high-end sound with pentode connection.
 
Amp size is 50x37cm and weights 20kg.

 
Artsi....you are a true CRAFTSMAN - one of the highest order. I envy you your skills. Marvellous work!
 

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