Little Dot Tube Amps: Vacuum Tube Rolling Guide
Sep 24, 2013 at 11:40 AM Post #3,061 of 13,413
  I asked that question over at "I <3 Tube Amps" and got my arse chewed on hard by the pros there... 
Lucky to make it out of there unscathed, but I did manage to get some info from the guru's while running away in sheer terror. 
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Two of them suggested to run both halves of the tube in parallel as opposed to floating or grounded.
 
 
Ponder it over and see what you think...

 
Lol, yeah, the internet can be a dangerous place to hang out (just look at the other threads here!).
 
I'd read that one of the options to use a double triode in a single channel gain stage is to parallel both triodes, but everywhere I looked, I saw that this would probably mean some degree of parts to change or adapt to work well (people suggest two separate grid stoppers for example). Besides, it's not like we need the extra current that would come from double dipping triodes. It's extra gain I'd like!
 
For a 12Ax7 tube, this isn't really a problem, since one side of the tube can be used with the other triode unpowered -unheated. On a ECC88, that's not possible. Apparently, the heated but idle triode would eventually get "cathode poisoning" from such a use over time (years, mind you), meaning that it wouldn't work well the day you decide to use it. Not that it matters, since it's easy to just use another tube altogether when the first triode starts to show signs of fatigue.
 
The real potential problem is just this floating triode... Which really should be grounded. Then again, I haven't seen or heard anything bad in my amp for the last 2 hours, so it is unlikely to be a huge issue. And I know that some -professional- amps use only one half of a double triode (with the other half grounded, obviously).
 
Sep 24, 2013 at 1:41 PM Post #3,062 of 13,413
  Next, with those adapters prepped up, you just have to manhandle the ECC88 tubes to fit in those 5 relevant pins in the 5 consecutive relevant holes (which would probably require you to bend the four left over pins on the tube, unless you have really small adapters). Look at the pics in full size if you want to get a better picture of what I mean.
 
.......
 
Now, I just need to solve the floating triode issue (ground the heated yet unused triode)...

 
Now that we know that the top front right screw on the LD IV is chassis ground, it should be possible, but perhaps a bit ugly, to assemble a wiring harness to connect the unused triode pins to that screw. Or otherwise, it might be just as well to cut off the four pins connected to the unused triode in the same manner as we cut off the pins connected to the unused diodes in the 6AV6.
 
Sep 24, 2013 at 1:56 PM Post #3,063 of 13,413
   
Now that we know that the top front right screw on the LD IV is chassis ground, it should be possible, but perhaps a bit ugly, to assemble a wiring harness to connect the unused triode pins to that screw. Or otherwise, it might be just as well to cut off the four pins connected to the unused triode in the same manner as we cut off the pins connected to the unused diodes in the 6AV6.

 
See, this is where I don't know which option to choose...
 
I guess depending on how well the ECC88 tubes work with a floated triode, I'll gauge whether or not it's worth bothering with an -ultimately ugly- grounding solution or just chopping those pins off neatly and be done with the problem.
 
I do recall reading that regardless of grounding, all the unused pins (triode + shield) should be tied together. It would probably be good to ground them in such a scenario, or at least ground the shield separating the triodes...?
 
Sep 24, 2013 at 2:36 PM Post #3,064 of 13,413
Sep 24, 2013 at 5:56 PM Post #3,068 of 13,413
   
Here's an idea for you:
 

Images of South Parks "humancentipad" episode come to mind... humancentitube... lol
 
Sep 24, 2013 at 7:13 PM Post #3,069 of 13,413
  Guy's I cant reach my jumpers...is tehre another way to put the RCA 6DT6A's into EF95 mode?

When jumpers are on EF92 setting on amp put in adaptor and your EF95 tube in adaptor

 
http://www.ebay.com/itm/300961753333?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649
 
Sep 24, 2013 at 7:14 PM Post #3,070 of 13,413
  Guy's I cant reach my jumpers...is tehre another way to put the RCA 6DT6A's into EF95 mode?

You will have to remove the jumpers to switch it into EF95 mode or cut off pin 7 on the 6DT6A but that would not be a good choice.
 
Find some long tweezers or a pair of hemostat's and pull the jumpers off.
 
Then PM me your mailing address and I'll mail you some long jumpers that are easier to get a hold of.

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Sep 24, 2013 at 7:25 PM Post #3,071 of 13,413
  You will have to remove the jumpers to switch it into EF95 mode or cut off pin 7 on the 6DT6A but that would not be a good choice.
 
Find some long tweezers or a pair of hemostat's and pull the jumpers off.
 
Then PM me your mailing address and I'll mail you some long jumpers that are easier to get a hold of.

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Where do you buy those long jumpers and what would be the size of those 2.54 M M maybe and whats the total lenght about . Thanks
 
Sep 24, 2013 at 9:35 PM Post #3,073 of 13,413
   
Where do you buy those long jumpers and what would be the size of those 2.54 M M maybe and whats the total lenght about . Thanks

They are for 2.5mm pin spacing and the jumper are 13.5mm in length.
 
I've collected a few from computer service over the years, but you could probably get a handful from a mom & pop type computer repair shop near you, they would probably have a bucket full of them lying around.
 
If not then eBay sells them as well.
http://www.ebay.ca/sch/i.html?_from=R40&_sacat=0&_nkw=jumper+cap+handle&_sop=7
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Sep 24, 2013 at 10:29 PM Post #3,074 of 13,413
GE 6DT6A's & CGE 6CS6's are in the house with the 6DT6A's in 1-7 mode for a bit.

 
\And the led lit up version's...


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