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Little Dot Tube Amps: Vacuum Tube Rolling Guide - Page 393

post #5881 of 5890
Quote:
Originally Posted by gibosi View Post
 

 

Actually, it is possible to do this with only one "lot of degradation". :) 

 

7N7 to 6CG7 adapter:

 

http://www.ebay.com/itm/two-Adapters-7N7-plug-adapters-6CG7-ECC88-tubes-amplifier-SUB-/250751485734?pt=Vintage_Electronics_R2&hash=item3a61f40726

 

And for those of you who do not want to mess with loctals, the late 1940's to early 1950's small-bottle chrome-top Sylvania 6SN7GT and GTA sound very similar to the 7N7.

 

Hi again gibosi.

 

Just popped back to correct my previous post - said mordy, not mab - and found your post...certainly much better than two piggy-backed, but $37 each PLUS postage?...OUCH!!...Will stick to my blood, sweat and tears!...

 

Cheers.

post #5882 of 5890
Quote:
Originally Posted by i luvmusic 2 View Post
 

how do you read the date on tubes?

 

For the small-bottle chrome-top Sylvania 6SN7GT and GTA (and other Sylvania tubes):

 

326 = 1953 week 26

 

 

Top etch codes:

 

D= April, 2 = 1952 (And R = Replacement - that is, not OEM issue)

 

 

Edit: Added top etch codes and fixed typos


Edited by gibosi - Today at 7:40 am
post #5883 of 5890
Quote:
Originally Posted by hypnos1 View Post
 

 

Hi again gibosi.

 

Just popped back to correct my previous post - said mordy, not mab - and found your post...certainly much better than two piggy-backed, but $37 each PLUS postage?...OUCH!!...Will stick to my blood, sweat and tears!...

 

Cheers.

 

Actually, $37 for a pair plus $13 for shipping (to the States), so still not cheap. :(

post #5884 of 5890

My tubes marking on the base are AL and on top of tubes F4B and F3B these are Sylvania Chrome top no number markings anywhere on or around  the tubes.So F=June 4=1954  and B=? is these right?


Edited by i luvmusic 2 - Today at 7:52 am
post #5885 of 5890
Quote:
Originally Posted by i luvmusic 2 View Post
 

My tubes marking on the base are AL and on top of tubes F4B and F3B these are Sylvania Chrome top no number markings anywhere on or around  the tubes.

 

F4B = June 1954 and F3B = June 1953

 

Also, you will see these small-bottle chrome-top Sylvania 6SN7GT and GTA with short bases and tall bases, still the same tube, same sound. :)

 

 

post #5886 of 5890

You can make a dapter for 8 pin to 9 pin using a copper fitting(reducer) 1'' to 3/4''. or 3/4'' to 1/2 for 9 pin to 7 pin.

post #5887 of 5890

What about EL34 as power tubes?

post #5888 of 5890
Quote:
Originally Posted by mab1376 View Post

What about EL34 as power tubes?
The EL34 is a pentode, you would need 4 of them strapped as triodes and probably would not work in our LD configuration. biggrin.gif
post #5889 of 5890
Quote:
Originally Posted by gibosi View Post
 

 

Actually, $37 for a pair plus $13 for shipping (to the States), so still not cheap. :(

 

Thanks gibosi...I should look more closely. But yes, not cheap...then again, if you can find the 7N7 for the right price you could be on to a winner!

 

A few more hours on the 7N7/Psvane combo and still WOW...I cannot believe it...veeery interesting!

post #5890 of 5890

Hi hypnos 1,

 

Firstly, I decided to try an all Russian all star lineup and use two 6P23N tubes for power tubes, and one for a driver. This worked quite well, and the bass became firmer and better controlled, without a feeling of hollowness. Nevertheless, real slam and attack in the bass is missing, but all-in-all a nice combination.

 

Then I read your impressions of mixing two different power tubes and getting a synthesis of the best of them both. Sounds interesting; let's try it. So I swapped out one 6P23N for my trusty Hoffman (nee RCA) top heater wire 6SN7.

 

Well, I listen through speakers and not headphones, and unfortunately I did not get any synthesis of the sound, but two distinct halves, right and left. The Hoffman side sounded full bodied and coherent with a fat round bass, and the Russki side sounded thin, akin to the difference in general between the 6N6P-IR tubes compared to the RCA 6SN7 octals when used as power tubes.

 

In conclusion, this did not work for me, but it taught me that power tubes could make such a difference that I could clearly hear the difference, similar to hearing the differences between different sets of driver tubes.

 

Now I am listening to the 6N23P as a driver with the RCA 6SN7 as power tubes. This is quite a good combination - the sound is open and forward with great detail and soundstage, except for a peculiar brightness bump in the upper midrange - we'll see if it gets better by time. The bass is very strong with great impact and slam; the mid bass is outstanding with a propensity to unlock the full bass potential of old 20's 78's (and everything else for that matter).

 

Funny that the other way around (6N23P power and octal driver) it is only OK, but this way with 6N23P as driver and power octals it is quite good.

 

About the upper midrange bump - I have four tubes, so I'll may try another one if it does not go away.

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