Little Dot Tube Amps: Vacuum Tube Rolling Guide
Feb 24, 2014 at 12:59 PM Post #5,131 of 13,434
 
So you like syrup eh? Me - I prefer honey! Preferably with lots of different, subtle flavours..

 
lol.. Well yes, sometimes the RCA is a bit too syrupy for sure, but it does a wonderful job of recreating a sense of being in a live performance space, and on some recordings, it is quite spectacular. However, the 6SN7 that spends the most time in my LD is a 1945 short-bottle Sylvania 6SN7W. It compares very well with my Heerlen-made E80CC, which is the most neutral and linear tube I have, with similar detail, but a stronger and more propulsive bass. So as of this moment, these are my top two tubes.
 
Eventually, I do intend to get to the C3-pentodes. But as they will require a significant reworking of my current configuration, swapping two loctal sockets for one 9-pin, I want to wait until I have finished exploring the ECC40s....
 
Cheers,
 
Feb 24, 2014 at 4:52 PM Post #5,132 of 13,434
Has anyone tried any VT-99 tubes?
 
Feb 24, 2014 at 5:02 PM Post #5,133 of 13,434
  Has anyone tried any VT-99 tubes?

 
I haven't, but they have gotten a fair amount of love over in the 6SN7 Tube Addicts thread. As it is simply a 6F8G, all you need is an octal socket and an adapter like this:
 
http://www.ebay.com/itm/Tube-adaptor-6F8G-to-6SN7-Socket-/400667131972?pt=Vintage_Electronics_R2&hash=item5d499f4044
 
Feb 24, 2014 at 5:37 PM Post #5,134 of 13,434
6F8G are great tubes if you have quiet one, BL63 better again. Re the former Tung Sol are the prefered with round plates but I have found many other good examples out there with and without both round plates and Tung Sol logos.
 
Feb 24, 2014 at 9:43 PM Post #5,135 of 13,434
   
I haven't, but they have gotten a fair amount of love over in the 6SN7 Tube Addicts thread. As it is simply a 6F8G, all you need is an octal socket and an adapter like this:
 
http://www.ebay.com/itm/Tube-adaptor-6F8G-to-6SN7-Socket-/400667131972?pt=Vintage_Electronics_R2&hash=item5d499f4044

 
so its an octal but different pinout? and whats the top cap in the adapter for?
 
Feb 24, 2014 at 10:10 PM Post #5,136 of 13,434
  so its an octal but different pinout? and whats the top cap in the adapter for?

 
Again, I have no experience with this tube, but yes, the pin-out is different and thus, an adapter is needed. The biggest difference is that there is an element, or perhaps one might say, a very fat pin located on top of the tube, which corresponds to grid 1.
 
wa22_6f8g.jpg
 
 
Feb 25, 2014 at 4:27 AM Post #5,138 of 13,434
Hi Artsi,


 


Here is a colorful idea for your next project. All you need is a WWII jerry can:


 


Triode-Festival-1.jpg



 


LOL

 


Usually those jerry cans smell like diesel for a long time. But i have plans to do normal stereo tube amplifier with headphone output. It is little bit different to work with output transformers, but we'll see what is going to happen.
 
Feb 26, 2014 at 11:12 PM Post #5,139 of 13,434
Hi,
 
Little quiet on the forum; we need a little action.
 
Here is a he-man tube, the indomitable 833C: (plz note the size compared to a regular tube)
 
 
 
DSCF1607.jpg

 
PICT0303.jpg

 
This is a broadcast tube that can generate some serious high voltage; 1200-2000V +
 
DSCF1753.jpg

 
 
Here is an application for stereo.
 
PICT0333.jpg

 
However, personally, I think that it is a bigger achievement to get $1000 sound from a $200 amp than to get great sound from an amp costing tens of thousands of $$......
 
Feb 27, 2014 at 12:08 AM Post #5,140 of 13,434
Yes, it has been quiet... So maybe I can stir things up a bit? lol
 
I have been thinking about whether it might be possible to use a rather different double triode, the E90CC, in our LDs. Users of Torpedo headphone amps
 
http://beezar.com/catalog/product_info.php?cPath=42&products_id=153
 
rate the E90CC to be the best tube available for that amp.
 
However, it has a common cathode, and evidently, there is no way to run it as a double triode in our LDs. When I first looked at this tube, and saw only 7 pins, I wondered how? Each triode typically takes 3 pins and then the heaters take 2 more for 8 pins! But in the E90CC, the two cathodes are tied together. So, this leads me to the idea of converting this double triode into a single triode, that is, finish the job by tying the two grids together and the two plates together in the socket.
 
Now.... my knowledge of electronics is just sufficient to get me into trouble... but not out of trouble!  lol...
 
So I will just throw this out and see if folks think this is crazy..
 
From what I have been able to figure out....  The plate resistance of the E90 is 4.5Kohms. So if we tie the two plates together, I guess the combined plate resistance would be 9.0Kohms? However, the ECC40 has a plate resistance of 9.3Kohms, and it works extremely well in my LD. So it would seem to me that the LD just might be able to handle a E90CC converted into a single triode...
 
TrollDragon and others.... what do you think?
 
Feb 27, 2014 at 12:52 AM Post #5,141 of 13,434
Feb 27, 2014 at 1:13 AM Post #5,142 of 13,434
From what I have been able to figure out....  The plate resistance of the E90 is 4.5Kohms. So if we tie the two plates together, I guess the combined plate resistance would be 9.0Kohms? However, the ECC40 has a plate resistance of 9.3Kohms, and it works extremely well in my LD. So it would seem to me that the LD just might be able to handle a E90CC converted into a single triode...  
TrollDragon and others.... what do you think?

Hey gibosi
 
Paralleling plates is like paralleling resistors the resistance will be half not double, so you will end up with an Rp of 2.25K
 
The parafeed amp does parallel the plates and the grids but it is designed to do such.

Sorry I don't know what the LD's minimum Rp value should be and can't say if this tube would be OK or not.
beerchug.gif

 
Feb 27, 2014 at 1:33 AM Post #5,143 of 13,434
I was thinking something along the lines of a 6D10, Compactron with three triodes in it, just ignore the middle triode and make a 12pin to dual 7 pin adapter and the heater is only 0.45A.
http://www.radiomuseum.org/tubes/tube_6d10.html
beerchug.gif

 
 
Feb 27, 2014 at 1:52 AM Post #5,144 of 13,434
  Hey gibosi
 
Paralleling plates is like paralleling resistors the resistance will be half not double, so you will end up with an Rp of 2.25K
 
The parafeed amp does parallel the plates and the grids but it is designed to do such.
 
Sorry I don't know what the LD's minimum Rp value should be and can't say if this tube would be OK or not.
 

 
lol... So I got it backwards!
 
But even so, the 6DJ8 has a plate resistance of about 2.5K, so the E90CC just might be OK...  
 

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