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Little Dot Tube Amps: Vacuum Tube Rolling Guide - Page 320

post #4786 of 10502

Hi tvrguy,

 

Glad to see a Koss Porta-Pro listed next to the Senns. These were recommended by Sam Tellig, and I finally got a pair on sale. Except for a little heavy on the bass I found them very enjoyable.

post #4787 of 10502
Wow that is a vintage II+, I guess it is common for the 4P1S's to arc as they are quite poorly made. Here is a thread on the amp and the 4P1L's

www.head-fi.org/t/265470/little-dot-2-owners-4p1l-tubes
post #4788 of 10502
Quote:
Originally Posted by mordy View Post

Hi tvrguy,

Glad to see a Koss Porta-Pro listed next to the Senns. These were recommended by Sam Tellig, and I finally got a pair on sale. Except for a little heavy on the bass I found them very enjoyable.
Hey mordy

The Porta Pro's are a great little open headphone I just love them. If you want a great portable closed headphone the JVC HA-S500's only from Japan on eBay are quite a step up from the Koss. They are my first goto portable when I don't need the openness of the Koss.

I bought from this seller here:
http://www.ebay.com/itm/141169666280

There is also a 700+ page appreciation thread here on HF. biggrin.gif
Edited by TrollDragon - 1/25/14 at 6:39pm
post #4789 of 10502

Does anybody have those National Union 6SL7 tubes how would they compare to the Tung Sol 6SU7GT and Sylvania 6SL7 VT-229                                                                                                                                                                                                                                                                                                                                      Processed By eBay with ImageMagick, z1.1.0. ||B2

 

                                                                          

Processed By eBay with ImageMagick, z1.1.0. ||B2


Edited by MIKELAP - 1/25/14 at 7:16pm
post #4790 of 10502

Those are some great looking tubes! Unfortunately, the only 6SL7s I have are a Tung Sol 6SU7GTY and a Sylvania 6SL7WGT. However, I do have a NU 6SN7GT. It is very smooth and liquid but rather dark with a very strong bass. I'll be curious to learn what you think of your tubes.

post #4791 of 10502

The coffee is hot, the 6Н23П is all warmed up and the German Maestro's 8.300 D's ready to go...

 

A little Chet queued up in 24/192

Smooth very smooth.

 

Taking a Jazz Appreciation course from the University of Texas at Austin.

Sign up closes today (Sunday) if anyone is interested in it.

:beerchug:

post #4792 of 10502

I have dug out 'Uncle Erics' medium Mu triode tests from the mid 90s as of relevance to the DIY experrimenters here.

 

Top tube was a

 

76 Sylvania 40s, 2nd harmonic at 0.002%, Rp 37k

 

then

 

5687 RCA 50s, 2nd harmonic at 0.005%, Rp 48k

6CG7 / 6FQ7 Sylvania 60s, 2nd harmonic at 0.005%, Rp 25k

9002 Kenrad 40s, 2nd harmonic at 0.005%, Rp 48k

76 RCA 40s, 2nd harmonic at 0.005%, Rp 37k

12SX7 JAN RCA 1955, 2nd harmonic at 0.005%, Rp 37k

12SX7 JAN RCA 1955, 2nd harmonic at 0.005%, Rp 37k (another example but tested identially)

 

than follows 5687WB, 396A/2C51, 6C5G, 76, 6GH8A, 5814 and the first 6SN7GT

 

6SN7GTA Sylvania 1982 and 1978, 2nd harmonic at 0.015%, Rp 48k

 

and then pages more of tested valves but this is where most 6SN7GT start appearing (so quite high up the list)

 

Erics general conclusion were:

 

basically 5687 and 6CG7 are capable of low distortion but need to be selected first.

Old 6SN7GT are very consistent (span being only 0.2%). Current Russian are OK but not as good as NOS.

9002 (and Acorn 955) are good.

Antique triodes like 27, 56, 76 are excellent. [perhaps also 30, 37?]

12AU7 and 5814s are not consistent.

7199 is not standout despite being a hifi tube!

Steer clear of 5963 and 5964 as they were intended a computing switching tubes and not linear operation.

12SX7GT were used in old military radion, if you are offered some don't turn them down. [These are ones that always stood out to me on the list and why I have used them ever since]

396A,, 2C51 are under appreciated in audio circles like 9002 and 7F8 (loctal version of 396A, 2C51).

 

Eric was recommending tubes above 0.025% distortion which covered most 6SN7GTs.


Edited by Nic Rhodes - 1/26/14 at 6:42am
post #4793 of 10502
Quote:
Originally Posted by Nic Rhodes View Post
 

I have dug out 'Uncle Erics' medium Mu triode tests from the mid 90s as of relevance to the DIY experrimenters here.

 

This is very interesting stuff. Thanks for posting!

 

But I wonder... Did Eric test the 6DJ8/6922/7308 tubes?

 

And also... I have been listening to the 6085/E80CC, and think this might be the best dual triode I have ever heard in my LD. Did Eric test this tube?

post #4794 of 10502
Quote:
Originally Posted by gibosi View Post
 

 

This is very interesting stuff. Thanks for posting!

 

But I wonder... Did Eric test the 6DJ8/6922/7308 tubes?

 

And also... I have been listening to the 6085/E80CC, and think this might be the best dual triode I have ever heard in my LD. Did Eric test this tube?


 re 6DJ8/6922/7308 yes he did test in his 'book', also most of this came out in VTV issues also. [I previous offered here to post the VTV 6DJ8/6922/7308 article but no one showed any interest then]. I will check on his stuff for E80CC but from my perspective it is a quality tube. No surprizes on that tube! Not cheap anymore but I did get a pair of Tungsrams for very decent money a month or two ago.

post #4795 of 10502

Hi Nic Rhodes and Gibosi,

 

"6CG7 / 6FQ7 Sylvania 60s, 2nd harmonic at 0.005%, Rp 25k" This tube is #3 on Uncle Eric's list.

 

I am listening to this very tube now, and it is quite good. Would put it on the level of the Japanese Raytheon. In comparison it has more bass presence but the treble is better in the Raytheon. Not as a forward sounding as the Raytheon.

 

 

The left tube is a 60's Sylvania and the right tube is the Sears branded version (appears identical).

 

Now, for somebody electronically challenged like me, can you please explain what difference the harmonic distortion makes, especially very small differences? Also, what is Rp37, Rp48 etc? Are there values you could use to match your equipment?

Can something that does not measure great sound good?

post #4796 of 10502

Do you know if there is an index for VTV? I downloaded issues 1 through 20, but without an index, it is not at all convenient or easy to find anything relative to a particular tube....

post #4797 of 10502

I am afraid it is a trawl through the back issues...nice article on 12SX7GT as a tube dumpster..

post #4798 of 10502

Here is my first 8.4V tube - a Sylvania 8CG7/8FQ7 from February 1952. The other date code is JAM. I have yet to find any post that deciphers the three letter date codes, and I can't figure out any connection between JAM and 652. (At least JAM is better than XYZ which is printed on one of my Sylvania tubes!)

 

In addition, the logo is not the usual Sylvania S or oak leaf, so I have my doubts if it really was made by Sylvania. However, the internal construction looks to be the same as the Sylvania 6CG7/6FQ7 tubes that I have.

 

 

 

If anybody could answer my questions at the end of post 4795 (above) I would appreciate it - thanks.

post #4799 of 10502
Quote:
Originally Posted by mordy View Post
 

In addition, the logo is not the usual Sylvania S or oak leaf, so I have my doubts if it really was made by Sylvania. However, the internal construction looks to be the same as the Sylvania 6CG7/6FQ7 tubes that I have.

 

 

If anybody could answer my questions at the end of post 4795 (above) I would appreciate it - thanks.

 

The internal construction looks identical to my Sylvania 6CG7. Moreover, looking at the plates, it looks nothing like an RCA, Tung-Sol or Raytheon, so I believe it really is a Sylvania.

 

As to your questions....

 

In my uninformed opinion, I am not sure we can hear distortion in the range of 0.005% to 0.015%, but I certainly do not know....

 

I do not know what Rp 37k or Rp 45k means.... perhaps 37k and 45k are frequencies? But what is Rp?

 

And if a tube measures bad and sounds good, it begs a number of questions: What parameters were measured? Can it be demonstrated that these parameters have any relationship to what we hear? If so, perhaps our ears are more sensitive than the test equipment? Anyway, I do not put much stock in measurements. I trust my ears and those of my colleagues. :)

post #4800 of 10502

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!

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