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Little Dot Tube Amps: Vacuum Tube Rolling Guide - Page 137

post #2041 of 8786
Quote:
Originally Posted by gibosi View Post

GE = the Philips code for EH90

 

1 = change code. Over time, as Philips implemented various changes and modifications to their tubes, the change code was incremented. I would guess that most of the time, these changes were small and perhaps undetectable to the naked eye.

 

A good example is the Philips E91H/6687 manufactured in Heerlen, Holland, as I am somewhat familiar with four different pairs:

 

3L = E91H

 

Date 1957 = 3L3 (D-getter and pinched glass envelope)

Date 1960 = 3L6 (D-getter and straight glass and ????)

Date 1962 = 3L7 (O-getter and straight glass and ????)

Date 1968 = 3L8 (?????)

 Hi gibosi,

 

Another little detail to confuse  matters even more : my first pair of 'Siemens' EH90s (without 'made in germany' on) had code B6G3, which is 1966, ya? The second (WITH) have B5I4, which is therefore 1965...Now the first have plain GE above, the second GE1 - one would have expected the change code to be the other way round , non? My conspiracy theory moves forward another step!!! (There's probably a very simple explanation...???).

 

Audiofanboy - glad I wasn't having a 'bad ear day' re the bass on these babies...when I returned once again to Cat Stevens's remastered 'Hard headed Woman', it nearly blew my head off!! So yet another added bonus - even if they aren't actually Siemens/Germany made...Will be interested to see what you make of the Blackburns after further burn-in.

 

Cheers!

post #2042 of 8786
Quote:
Originally Posted by hypnos1 View Post

Another little detail to confuse  matters even more : my first pair of 'Siemens' EH90s (without 'made in germany' on) had code B6G3, which is 1966, ya? The second (WITH) have B5I4, which is therefore 1965...Now the first have plain GE above, the second GE1 - one would have expected the change code to be the other way round , non? My conspiracy theory moves forward another step!!! (There's probably a very simple explanation...???).

 

Conspiracy theory? lol... However, I don't have an explanation and all I can do is conjecture that it might simply be a poor etching. On my single Siemens (1959 [B9F] and pair of Valvos [1967 (B7A3)],  I can't even find GE plus a number etched in the glass. If these codes are there, they are just too faint for me to make out....

post #2043 of 8786

I am still luxuriating in triode land, most recently under the spell of the Amperex/BugleBoy EBC91 (or perhaps, I should say RCA 6AV6! lol).

 

This morning, I received a pair of CBS-Hytron 6AV6. Yes, this CBS is the Columbia Broadcasting System. In the early 1950s, CBS acquired Hytron Laboratories as they attempted to push deeper into vacuum tube technology, TV and radio manufacturing, and color broadcasting. However, this venture was short-lived as it appears that CBS-Hytron ceased production in 1961. These tubes are dated 1958.

 

post #2044 of 8786
Quote:
Originally Posted by mordy View Post

Hi All,

 

What follows here is a review of the the mighty Tesla 6H31 heptode tubes (6BE6) from 12/58.....

 

On the EF95 1/7 setting the first impression is detail. Gobs and gobs of detail, micro, macro, looking into the recordings and hearing things you did not know were there before. The detail of the bass and treble is exquisite; it is like you walked into a dark basement and attic and turned on the light - everything is there. The tubes are very revealing, but not ruthlessly revealing to the point that deficiencies in recordings are highlighted. However, the quality of different recordings becomes immediately apparent. The tubes are neutral but analytical with a super detailed presentation - they won't let you alone but force you to listen carefully. They are open, airy, crystal clear, with a wide 3D sound stage. The bass is strong with good timbre and grip on the low frequencies.

 

The only con is a certain coolness in the mid range. The only way I can describe it is when you try to fix a photo on the computer and try to adjust the color and everything suddenly gets a slightly blueish hue. The tonality is not so warm, but perhaps it is equipment dependent.

 

I'm not surprised that you are finding the mid range a bit cool. Grid 3 on the 6BE6 is remote cutoff, that is, it was deliberately and precisely designed to have a nonlinear response. Thus when you strap a linear Grid 1 and a nonlinear Grid 3 together, the resulting combined grid is going to be somewhat nonlinear. And it makes perfect sense that a nonlinear grid is going to affect the sound in some way.

 

When I strapped the Siemens EK90 (6BE6), 1/7, I had a similar experience. The analytical detailed presentation and 3D sound stage were beyond compare, but the mid range was just not right. Eventually, I arrived at the conclusion that for me, unstrapped was best for that particular tube.

 

Interestingly, it seems that this phenomena may not be due entirely to the fact that the 6BE6 Grid 3 is nonlinear. Even strapping the 6BY6, with two linear signal grids 1/7, I notice that the mid range becomes a bit thinner on both the Sylvania 5915 and the Amperex E91H/6687. AFB also noticed and discussed this with regard to his Telefunken/Sylvania 5915. However, at least on the Sylvania 5915, strapped 1/7, in my mind the mid range is still quite acceptable, and the analytical detailed presentation and 3D sound stage more than makes up for a slightly thinner mid range.

 

And now that more people are listening to the 6CS6/EH90, it will be interesting to learn more about how they behave strapped 1/7....

post #2045 of 8786
Ah after reading all your posts I am so curious! I want to tube roll too but sadly the shipping costs from other countries are just way too high. If only my country sold nos tubes...instead only shops which sell brands like EH,JJ,Gold lion. All the expensive ones and none compatible with the little dot. I shall continue to stalk this thread so I can find more tubes to try. Thank you guys for the time you take to try these tubes.
post #2046 of 8786

Post ex-2045 [I see it's disappeared & there's a new one] above is clearly spam & has been duly reported. The French is a random extract from an online contract & the links speak for themselves.

 

Tiresome.


Edited by bruce108 - 7/24/13 at 4:29am
post #2047 of 8786

Hi Gibosi,

 

I feel so much better now that somebody is commenting on my Tesla review that involved many hours of thought, effort and reflection - thanks.

 

Since the differences between different heptodes are so subtle, it is much more difficult to differentiate and describe the characteristics of each tube. The evaluating process is known to lead to heptode overload and heptoditis, usually cured by putting your brain in neutral and taking a break from critical listening.

 

I have used the Teslas another 10 hours. Don't know if my brain or the tubes adjust (or both), but the mid range discoloration seemed to disappear into the background, and I was thoroughly enjoying the tubes so much so that I didn't want to switch to the next project of evaluating the IBM 1680 tubes. As you state: the mid range is still quite acceptable, and the analytical detailed presentation and 3D sound stage more than makes up for a slightly thinner mid range.
 

Now, re the EH90, when I tried my Siemens EH90 unstrapped the Dreaded Hum suddenly appeared in the right channel. It sounded like the low frequency hum of a window air conditioner and was not volume dependent. Once before I had hum in the right channel which went away after I changed the tubes. The Little Dot blog has several entries about R channel hum and a check list how to try to eliminate it. Seems that in some instances the hum comes from a bad cable connection. Don't know yet if the hum was permanent for the NS setting with the Siemens tubes or temporary. Also don't understand why the hum would only affect one channel, and always the R channel. The design of the LD is two completely separate channels, but in many instances only the right channel hums, which leads me to think that there is some kind of synergistic effect.

 

I have a pair of Sylvania 6CS6(EH90) tubes waiting to try but this has to wait until the 1680's have been grilled to perfection....

post #2048 of 8786

 

Speaking of grilling 20 hours later the hungarian russian 6A2P tubes dont sound bad but are not as open and transparent as the SYLVANIA 6AV6 that i am starting to burnin now, the Sylvania sound like a typical 6av6 tube so far. And by the way Audiofanboy dropping by in Montreal tomorrow with little glass goody's i got from him .It's going to be fun meeting him and his dad . Like we say over here. BIENVENUE AU QUEBEC !                                                                                                 


Edited by MIKELAP - 7/23/13 at 9:01am
post #2049 of 8786

Processed By eBay with ImageMagick, R1.1.1.M2b

 

News regarding the socket adaptors reported a while back that sockets didnt work well actually they did but they were built backwards the amp jumpers should of been on the EF92 settting instead of theEF95 settings, noticed this today on the sellers website when i read the bottom of the page  i went aaaaaaaaaaaaaaaaahhh !!!!!! so  UNDER THE AMP EF92 JUMPER SETTINGS when the SOCKETS ARE ON  you can use the EF 95 TUBES  ain't that grand.  EDIT: NOTICE TUBE IS EF92 NOTHING TO HELP CLEAR THINGS UP !


Edited by MIKELAP - 7/23/13 at 12:19pm
post #2050 of 8786
Yup, private NOS tube exchange in Montreal, PQ, tomorrow; you just can't stop globalization lol. We have a French in his late 20s selling American & German olde world tubes to a Canadian twice his age -and all that while on vacation, I'd call that optimizimation!

About strapping heptodes, and especially the newest 6CS6/EH90, I found that my M.B.L.E. Mazda EH90 (which should sound and react very close to Blackburn's) sounded very nice 1-7 srapped actually. I had to quit rolling them since I was leaving the country for a few weeks, but from what I had time to test, the tubes had more gain than unstrapped (moreso than the difference we saw with other heptode types, which makes sense as g3 has a higher gain on this type; I suspect the amp also ran hotter but then again it was 30/90 °C/F...), sounded just a tad more detailed (not a night and day difference like 6BY6 tubes), and the bass was even better (harder hitting) and deeper (sub bass like I've rarely heard on this amp). I haven't reached a conclusion as to what setting I prefer though.
Edited by Audiofanboy - 7/23/13 at 1:21pm
post #2051 of 8786
Quote:
Originally Posted by Audiofanboy View Post

Yup, private NOS tube exchange in Montreal, PQ, tomorrow; you just can't stop globalization lol. We have a French in his late 20s selling American & German olde world tubes to a Canadian twice his age -and all that while on vacation, I'd call that optimizimation!

About strapping heptodes, and especially the newest 6CS6/EH90, I found that my M.B.L.E. Mazda EH90 (which should sound and react very close to Blackburn's) sounded very nice 1-7 srapped actually. I had to quit rolling them since I was leaving the country for a few weeks, but from what I had time to test, the tubes had more gain than unstrapped (moreso than the difference we saw with other heptode types, which makes sense as g3 has a higher gain on this type; I suspect the amp also ran hotter but then again it was 30/90 °C/F...), sounded just a tad more detailed (not a night and day difference like 6BY6 tubes), and the bass was even better (harder hitting) and deeper (sub bass like I've rarely heard on this amp). I haven't reached a conclusion as to what setting I prefer though.

Private you say sounds serious ill bring my body guard (my wife) later .

post #2052 of 8786

http://www.ebay.com.my/itm/Lot-of-2-Vintage-TELEFUNKEN-EH900S-E91H-Audio-Radio-Amp-Vacuum-Tubes-/400405173654?pt=Vintage_Electronics_R2&hash=item5d3a021596&_uhb=1#ht_1630wt_1139

 

Just found this on ebay :D TFK E91H only 8$ for a pair before shipping. According to the codes i'm thinking Heerlen 1969 January 4th Week

post #2053 of 8786
Quote:
Originally Posted by siles1991 View Post

http://www.ebay.com.my/itm/Lot-of-2-Vintage-TELEFUNKEN-EH900S-E91H-Audio-Radio-Amp-Vacuum-Tubes-/400405173654?pt=Vintage_Electronics_R2&hash=item5d3a021596&_uhb=1#ht_1630wt_1139

 

Just found this on ebay :D TFK E91H only 8$ for a pair before shipping. According to the codes i'm thinking Heerlen 1969 January 4th Week

Misread shipping rate saw $42.80 but that was to Malaysia i think is shipping rate decent.


Edited by MIKELAP - 7/23/13 at 6:13pm
post #2054 of 8786
Quote:
Originally Posted by MIKELAP View Post

Misread shipping rate saw $42.80 but that was to Malaysia i think is shipping rate decent.

Even my 5 pcs of 6AH6WA didnt cost me more than 15$...42.80$ for 2 pcs is a bit much...for shipping that is


Edited by siles1991 - 7/23/13 at 7:00pm
post #2055 of 8786
Quote:
Originally Posted by MIKELAP View Post

Misread shipping rate saw $42.80 but that was to Malaysia i think is shipping rate decent.
What the hey....

Shipping to: Worldwide
Excludes: Canada

This seller does not ship to Canada

Now there's a prime DB for ya... biggrin.gif
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