300B driver tube 6SN7 and 6SL7

[joe3rp]

Mga GURUs,

I have a 300B amp with a 6SN7 Sovtek, I have also tried an 6SN7 NOS RCA which I found too dark and syrupy. I prefer the detail of the SOVTEK with enough body to image.

I have read some 300B amps with driver 6SL7, 6SU7 or Mullard ECC35...can this be interchanged with the 6SN7????

Do any of you have spare 6SN7 (a pair) for sale? Tungsol ?

joe3rp

[arnoldc]

i'm not a guru, but these specs say that are not interchangeable without circuit modification.

6SN7
Vh=6.3, Ih=0.6, Cgk=2.6, Cak=0.7, Cga=4.1, Va=250, Vg1=-8, Ia=9, Ra=7,700, Mu=20.02

6SL7
Vh=6.3, Ih=0.3, Cgk=2.15, Cak=0.9, Cga=3.5, Va=250, Vg1=-2, Ia=2.3, Ra=44,000 Mu=70.4

[mozilla]

Here's something worth reading:
=============
Best of 6SN7 and GZ34



Lee HC?s Summary:

It had been several months since the last blind test of vacuum tubes. We were happy to arrange another party of blind test of tubes last Saturday. As Tim mentioned, being privileged as participants, I need to buy the tubes first before I report the event & my preference here. So, I bought the tubes yesterday.

Here is the story. It was a blind test of the rectifier GZ34 & line amp tube 6SN7 for the R&D 2A3-300B integrated SETA.

System:

Proceed CDD - The One AES digital cable - Aragon D2A2 - AS Gen5 - R&D 2A3-300B - AQ Midnight 2 - Klipsch KLF-30. Audition area : 11.5 ft x 20 ft.

Methodology:

6 participants.

Tim was the moderator & changed tubes.

We rated each numbered tube with reference to sonic attributes, treble, midrange, bass & dynamic, resolution, musicality, after audition of the tube. Then, we gave personal ranking of the tubes to Tim to make up the overall rating. Only after completion of the overall rating, we got information of the

tubes.

Candidates listed according to sequence of appearance:

6SN7 type & substitutes

1. CBS 6SN7

2. Sweden made 33S30

3. Osram B65

4. Telefunken 6SN7

5. Mullard ECC32

6. Mullard ECC33
GZ32 type & substitutes

1. Mullard GZ32
2. Mullard GZ34 big black base

3. Mullard GZ34 metal base

4. Mullard GZ34 big brown base

5. Telefunken GZ34 - unfortunately not working.
Difference in preference of tubes were expected as the personal rating is quite different. The preference of first & second choice of the tubes are identical between me & Alan.

So, here is my personal preference of tubes, start from the best:

6SN7 :

1. Sweden made 33S30

2. Osram B65

3. Telefunken B6

4. Mullard ECC32 (default tube)
5. Mullard ECC33

6. CBS 6SN7
The first (Sweden) & second (Osram) are quite close but different in sonic attribute between themselves. To me, they are obviously outstanding among all six.
33S30 rated best in the treble sound more beautiful & musical to me. Musicality, very subjective? right it is! Osram rated best in the midrange, but loss in bass quite significantly. Telefunken have been my favourite brand, best in resolution this time, but unfortunately not the best match with the amp & the speaker this time.

GZ32:

1. Mullard GZ34 metal base

2. Mullard GZ34 big brown base
3. Mullard GZ32

4. Mullard GZ34 big black base

Default Mullard GZ34 small black base is put aside to save time. Again, The first & second are quite close but different in sonic attribute between themselves and are also obviously outstanding among all four. The metal base is best in treble, resolution. The big brown base is best in bass. The mid range & musicality is nearly identical for the two.

At this juncture, I must confess that I'm more biased toward beautiful mid, treble, resolution & musicality. Bass & dynamic are not my major concern from SETA.

Maybe, Tim should be able to give more information on the overall rating to the tubes. Finally, let me express my greatest thank to the contributors of all the tubes for party.

Rgds.

Lee HC



Summary from Tim:

Since Lee HC got his favourite tubes already, now is time for a proper run down.

Another great party last Saturday and many thanks for Lee HC for hosting this again. Although there were only Alan, LeeHC, Chung, Andy Law, and myself, I am convinced that that we have heard some of the best 6SN7 and GZ34 ever made. Edwin also joined us later for the GZ34 match.

Here is the line-up :

6SN7

1. CBS 5692 red base

2. Sweden made 33S30/M2462

3. Osram B65 metal base

4. Telefunken 6SN7

5. Mullard ECC32

6. Mullard ECC33

GZ34

1. Mullard GZ34 (small black base)

2. Mullard GZ32

3. Mullard GZ34 (big black base)

4. Amperex BB GZ34 (metal base)

5. Mullard GZ34 (big brown base)

For the 6SN7 match, the Osram B65 enjoys the highest total score, very closely followed by the 33C30 and TFK 6SN7. I would say they are very likely to be of the same class and way above the CBS red base 5682. The TFK is so rare that most of us do not even know it exists! I don't think it is possible to buy this any where in the world in NOS or even used form. The metal base B65 is well known and quite expensive. Used ones costs around HK$600 and NOS probably double that price. I have actually never seen any NOS metal base B65 before. IMO, this has the best mid-range of all and also most musical to my ears. The 33C30 is probably the best buy as it is only RR grade 6SN7 around that you can still buy from shops!
ECC32 ad ECC33 has clearly different gain and sound too "hifi" in the R&D at the expense of musicality. I believe these 2 tubes should only be used in system that is far too show and flat.

For the GZ34, in a sense, there is no surprise at all. As the performance of each tube map exactly to the price of each. The most expensive metal base GZ34 is the clear winner, followed by the next expensive big brown base, and the big black base. The only interesting thing is that I believe most of us actually prefer the Mullard GZ32 to the most common small base GZ34. I actually quite like the GZ32 myself.

So this is it and I will let all the participants to express their own views.

Tim



Comment from Chung:

My rating is quite different to others.

Since the 1st,2nd and 3rd got 9,10 and 11 mark (less is better), So actually, they are close!

I feel Telefunken the best. It's Resolution is the highest, more musical and better balance. I want buy it!!

The 33S30 is better bass control and more HiFi and clear.

Osram is more high and more musical than 33S30.

ECC32 & ECC33 is quite different tube, since the gain is higher, so difficult to compare!!

Anyway, 33S30 is the best buy tube. Actually, the structure is same as RCA 5692, which we forgot to compare. Their sound should be very close. (Tim ? we did. Their sound is NOT close)

Chung



Alfia?s comment:

I really miss the chance to listen to the well known R&D amp ! I have both the following tubes

and I have been listening to them for the last 4 days just to get some feeling about the 6SN7 match.

ECC32

RCA red 5692

33S30

CBS

B65

Philip JAN

RCA JAN

IMO, I do feel that B65 is very musical and sweet, not as dynamic as the other 2 ECC32 is best in dynamic and detail and sound stage RCA red based 5692 is best in detail and air and image focus
One thing I am not in agreement is the ECC32, it may not be the best, but it is amount the top. I am

no sure which version I own, it has a black base and semi transparent grey glass bottle with D getter.

Again this is only from my system and it may perform differently in another setup.

Alfia



Tim?s reply on ECC32 vs. 6SN7:

Creevy YU wrote in message <740tf5$7h7@hkusud.hku.hk>...

>

>Hi Tim,
>

>You know best with the valve structure, and I would like if you can elaborate

>the structure of each tube as there are many versions among themselves.

>

>My testing which was 3 years ago, show some discrepancy with your group's

>comment. As we have the highest rating on the Mullard ECC32,

>I will agree if the system need such a boost. As a matter of fact, I have tried

> the B65 against the ECC32 on the SAME amp before but pushing the Rogers

>LS5/9. In that match, the ECC32 won hands down. But on the KLF30, the B65

>is clearly a better choice. However, there

>are 6 different types of the ECC32 as far as I can recall with huge variation

>in performance. Would you tell us something below for the ECC32(actually not

>only this but please also the telefunken B6/6sn7,Osram B65, CBS 5692 and the

>Mullard ECC33):

>

>1. Base color,

>2. Getter Shape

>3. Plate Color

>

CBS 5692 red base black plate

M2462 brown base rusty black plate

B65 metal base inverted cup shape getter

TFK 6SN7 fat getter, big black base

Mullard ECC32 black base inverted cup shape getter

Mullard ECC33 black base (cannot remember getter)

Which version do you mean is the best for each type?

Tim



Creevy?s comment:

Our test on 6SN7 is more or less similar but the Mullard ECC32 comes with black base, black plate with a circular spot at the centre of a thin plate getter, whereas the B65 is the earliest prototype with clear glass( the inverted cup getter ECC32 and the smoky glass B65 were rejected after our first

informal audition.) The ECC32 performs slightly better in our test (we used he Cary 300SE with Roger 15ohm 3/5a) than the B65. The remaining test result was more or less the same.

The metal collar GZ34 are excellent. Don't miss the WE 274 next time for a complete rectification tube test.

Creevy

[ambel]

This is only a guess but it seems that the 6SN7>300B amp might
be a 3 stage cascade amp. Using 6SL7 in place of 6SN7 will result
in too much gain that's only one problem. Considering the plate
resistance for 6SN7 is around 7700 ohm vs. 44000 ohm, I max 20 ma
vs. 5 ma. So they are not interchangeable but If you convert the
gain and driver stage to SRPP circuit you can use the 6SL7.

[johnmarc0]

Joey,

You can change then but your bias will go out of whack, try it tubes are robust anyways.

Just make sure you go passive on the line stage, I reckon you will be biased a bit higher in the 12 to 15V range (from the typical 6V) for the 6SL7. Most 6SN7/6SL7 tubes are RC coupled voltage amplifier service they have RL of 50K or more. But if your amp is using direct coupled amps, the cathiode voltage will shoot up on the 300B (a few hundred volts). So just make sure it is not DC coupled 300B amp and you should be okay.

JM