[TrollDragon]

Rp is the Dynamic Plate Resistance of the tube.

Here is a good explanation of that value:
http://www.guitarstudio.tv/Splawn/explanation_you_must_read.htm

 

[gibosi]

  Has anyone used 6SN7 with the octal adapters? I think i read somewhere it needs more power than the LD can provide but i'm not sure. Currently i've got a re-issuse Tung SOL 6SL7GT and a NOS Tung Sol 6SU7GTY in the mail to get started rolling octals. Can't wait to get started!

 
Yes, you can use the 6SN7 with an octal adapter. It is pin-compatible with the 6SL7, so plug and play. But it does draw 600ma and this is more than the 500ma that many of us believe the LD can safely provide. So if you want to roll 6SN7, it is strongly recommended that you get an AC to DC adapter and a voltage regulator. 

 

[gibosi]

6SN7 to E80CC and everything in between...
 
Yesterday, I revealed my tricked-out LD1+ (running a MUSES 02) to several local Head-fiers. And I asked them to help me evaluated four tubes:
 
1948 Tung-Sol 6SN7GT with black glass and round plates
1960 Heerlen-made E188CC
1951 Western Electric 392A/2C51
1961 Heerlen-made E80CC
 
Our goal was to determine the tube with the most accurate and correct tonality. We listened through a pair of HD 700 headphones, and for music, we used "Halloween" and "The Stone" from "Before These Crowded Streets" by the Dave Matthews Band. These two tracks seamlessly run together for a run-time of about 12 and 1/2 minutes.
 
As could easily be predicted, the 6SN7GT was judged to be the most colored, and thus ranked No. 3. The E188CC and the 396A/2C51 tied for No. 2. And the E80CC was judged No. 1, based primarily on it's ability to accurately reproduce treble and upper harmonics.
 
In my mind, the Heerlen E80CC is a step up from the Heelen E188CC, and those of you who place a premium on linearity and accuracy, may wish to try this tube. However, they can be a bit expensive (but I got mine for only $29.00, likely because it carries the Zaerix label, and not Amperex). Moreover, you will need an external heater PS as this tube draws 600ma at 6.3 volts or 300ma at 12.6 volts.
 
To my way of thinking, I am very happy to have both the Heerlen E80CC and the Tung-Sol 6SN7. When I wish to listen actively, the Heerlen E80CC is my choice. Its accuracy and clarity is quite amazing. But when I want to chill out, perhaps after a drink or two, the Tung Sol is my choice. The added warmth and coloration, while certainly not accurate, is quite beautiful. And the tube transports me to an enhanced, or should I say "exaggerated", sound stage which feels magical.

 

[mordy]

Hi Gibosi,
 
I believe that you have the Raytheon 6CG7/6FQ7 tube. How does it compare to the tubes you did a shootout on?

 

[mordy]

Hi trolldragon,
 
Thanks for the link about Dynamic Plate Resistance (Rp). I cannot say that that I understand it too well, except that this value seems to be a real world measurement of the tube in action.
What I don't understand is if the Rp value can be taken as a sole indicator of how well the tube sounds, or if this value must be used in the context of other measurements.

 

[kvtaco17]

  Hi Gibosi,
 
I believe that you have the Raytheon 6CG7/6FQ7 tube. How does it compare to the tubes you did a shootout on?

This!

 

[gibosi]

 
I believe that you have the Raytheon 6CG7/6FQ7 tube. How does it compare to the tubes you did a shootout on?

 
It's on my to-do list, along with comparing it to the Raytheon 6SN7GT/VT-231.
 

Spoiler: Raytheon 6SN7GT

 

[mordy]

Hi Mikelap,
 
I believe that I have the same type of National Union tube as you have:

If you look at post #4132 on page 276 you will be able to read my impressions of it. After 100 hours of burn in I wrote that " I have this single 1940-50s  octal National Union 6SL7 which is getting better and better. After about 100 (!) hours of burn in the bass is getting more and more distinct and powerful and the detail, imaging and sound stage all have improved. An absolutely delicious tube!"
 
Right now I am visiting 6/8CG7 land. The 8CG7 Sylvania tube I am listening to now has more powerful bass than the Sylvania 6CG7. What I like about this family of tubes is the beautiful timbre and quickness and wide sound stage.
 
I would really like to hear from AFB how this tube compares to his best 6DJ8 type tubes.....

 

[mordy]

HI G,
 
Your Raytheon tube looks similar to mine.

 


I listened to this tube but unfortunately, I was not impressed. The bass and treble had limited extension, and it just sounded tired. Hope your example is better.

 

[gibosi]

  HI G,
 
Your Raytheon tube looks similar to mine.
 
I listened to this tube but unfortunately, I was not impressed. The bass and treble had limited extension, and it just sounded tired. Hope your example is better.

 
Yours is an earlier version, with T-plates. Mine is a bit later, with flat ribbed plates and two support rods. According to "The Reference 6SN7 Thread", the flat plate version sounds better.... And after reading your comment, I sure hope so.   
 
As my US-made Raytheon 6CG7 also has the same flat ribbed plates, it is reasonable to think that my 6SN7 will sound very similar, but will have to wait and see....

 

[TrollDragon]

Hi trolldragon,

What I don't understand is if the Rp value can be taken as a sole indicator of how well the tube sounds, or if this value must be used in the context of other measurements.

Everything factors into the equation, board component values, output tubes, the whole works... I wouldn't worry too much about all the factors. If your music sounds good to you with a certain tube then that is really all that matters isn't it?

Personally I'd rather listen to my music then concentrate on listening to the gear.

There is only so far you can take these little amps, once you've listened to higher end tube gear with an optimal circuit designs and much better components, a few tubes rolled will not give you the sonic quality of the higher end rigs. It's a lot of fun to check out all the possibilities but at some point the pursuit of the "Perfect Tube" becomes more than the results obtained IMHO.

Take Artsi's DIY octal amps for example, I don't even think he has listened to his Little Dot since he made the jump. He can fine tune all the other components for optimal results as well as adjust the tubes he is using for proper performance.

This is why I don't actively persue the FoTM tube anymore, I don't really need a drawer full of tubes that I will never listen to a month or two later.

This is just my take on the whole thing, YMMV and it's all good for those who want to seek out some great tubes.

Sorry for the rant...

 

[Artsi]

Yes,it is more than 2 weeks when i have listened my little dot for one minute.

Surprisingly i have focused now rolling my 6080 and 6AS7 power tubes. They affect much to sound quality in my diy amp. Much more than with little dot. Of course 6080/6AS7 tubes quality is rather variable and they are not meant for audio originally. And they need serious burn-in for an optimal sound. Now i'm listening raytheon 6080WC's. As new sound is very smooth and enjoyable, but i hope after hours of usage sound get more sharpness.

I still have much to learn with diy tube amps. It is fun to notice how different resistor values and different biasing will affect to sound.

Next i'm planning to do little amp with 4 6N6P's as powertubes and one octal socket for double triode to drive them. Amp should be appropriate to use even with 32ohm headphones,since output impedance should be around 25-30ohm. I have octal to 9pin 6 and 12v adapters, so with this amp i can roll all my single double triodes.

sorry for offtopic

 

[mordy]

Hi TrollDragon,
 
Thanks for your insightful comments. Had to look up what FoTM means (flavor of the mouth). I too, do have boxes of tubes that I will never listen to. However, to me, part of the excitement in tube rolling is to find an obscure and cheap tube that beats the big expensive boys.
 
As has been mentioned by some of the members on this forum, there seems to be a feeling of seeing the tube glow at the end of the tunnel, although different people have different preferences. Personally, I think that the human ear is the most sensitive instrument. What is amazing to me is that people in different parts of the globe and with very diverging tastes in  music can come to a conclusion and agree on which tubes are the best for the Little Dot amps.
 
Some people like the super detailed, analytical tubes, others the warm and musical ones. I think that it is possible to find a tube that is both super detailed and warm, and with excellent bass and treble characteristics. In other words, a tube that has EVERYTHING.
 
Maybe ignorance is bliss, but not having heard the super expensive tube amps, I am perfectly happy with the sound I now get out from my LDIII. Nothing bothers me, and I have been listening to music and Hi Fi for over 55 years.
 
The LD MKIII is hooked up to a 80's Sony 110W amp, and I am using plebeian Polk speakers with a sub. Musical bliss for a very small cost, + the cost of some 400 tubes....LOL

 

[TrollDragon]

Hey mordy!
 
That is excellent then, please do enjoy the fun and your great setup.

 

[i luvmusic 2]

With all of those 8 pins and 9 pins tubes that you guys are using with adapters/converters with separate power supply does it really sound better than most of the 7 pins tubes specially compare to 6HM5 and  6CS6(my favourite)?