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Little Dot Tube Amps: Vacuum Tube Rolling Guide - Page 283

post #4231 of 10501
Quote:
Originally Posted by gibosi View Post
 

In my opinion the 12AX7 / 5751 tubes, and even the 6SL7s, are not worth your time and money. I believe that the 6DJ8 are unquestionably superior, at least in our LDs, But again, this is only my opinion.... :)

 

Quote:
Originally Posted by Audiofanboy View Post
 

Oh.

 

Well... I guess that just answers a few questions right there lol... Hopefully the 2C51 may be able to hold a candle to the all-mighty 6DJ8 so we can at least have some alternative?

 

Then again, I keep marveling at both how good the 6922 and 7308 are, all in all, and how well they work in my LD... I only have 10 hours on my - one of my two - Philips 1960 E188CC, and I can already tell how these how very very very rugged and nice tubes. Even after 3 hours, the detail in the treble and sense of air (see the comments on the RTC E188CC over on the Lyr thread) were impressive. I haven't had a chance to listen to the tube that critically yet, not with music at least, but after 10-12 hours, I am hearing something I like!

 

Maybe I should explain my thinking...  The Sylvania 5751 TMBP and the Tung-Sol JAN-CTL-6SU7GTY are very good tubes, among the best of their breed. But in my opinion, they are not as good as the 6922/E88CC and 7308/E188CC I have been listening to recently. Given that, on eBay the Sylvania and Tung-Sol have typically been going for around $50. On the other hand, I have paid in the neighborhood of $30 to $50 each for the eight 6922 and 7308 I have. So if one is willing to spend $50, I would absolutely recommend a nice 7308. But if the Sylvania and Tung-Sol can be gotten for $25 to $30 each, then by all means, grab them. Cheers.
post #4232 of 10501
Quote:
Originally Posted by gibosi View Post
 

 

Well color me surprised!  I just won one... and at a pretty good price - $12 plus $5 shipping. In a few days, I hope to be able to see how one of the best of the 2C51 compares to some of the best of the 6DJ8. :) 

 

Nice! Hopefully that'll directly settle whether or not it's worth pursuing that tube type without spending any more cash.

 

As much as those tube rolling adventures have been very pleasant (and still are right now), I do like the feeling that we're "wrapping it up" somewhat, and at least narrowing our range and reorienting our money toward excellent tubes that we know will both sound good and couple well in our LD. It just seems like a so much better investment than before lol...

 

And, yeah, for those who haven't treated themselves to a good 6922/E88CC or 7308/E188CC, I urge you to do so. I mean, any Philips group premium 6DJ8 will take your amp to a different and better world...!

 

Quote:
Originally Posted by TrollDragon View Post

Hey gibosi

Pricklely Peete in this thread has done some major mods to his amp improving the sound totally.

He also suffers from a mains voltage of 127V which brings his filaments up to 6.9 or 7. He solved this issue by putting a 1 ohm 3W resistor in series with the filament which dropped it .5V I think this is something you should look into as well to improve the longevity of your tubes. Running them at 6.2 or 6.1 will definitely make them last longer.

Here is the link, info is about halfway down.
www.head-fi.org/t/439449/little-dot-mk-iii-mods/15#post_5938548

beerchug.gif

 

So, hypothetically, would adding another filament "in series" with the the first one (i.e., a second tube) yield a similar drop in filament voltage, like in the example where a 6SL7 was swapped for a 6SN7 and voltage dropped?

 

If so, I still think that just wastefully using two separate tubes may just better and prettier...

 

Quote:
Originally Posted by gibosi View Post
 

Maybe I should explain my thinking...  The Sylvania 5751 TMBP and the Tung-Sol JAN-CTL-6SU7GTY are very good tubes, among the best of their breed. But in my opinion, they are not as good as the 6922/E88CC and 7308/E188CC I have been listening to recently. Given that, on eBay the Sylvania and Tung-Sol have typically been going for around $50. On the other hand, I have paid in the neighborhood of $30 to $50 each for the eight 6922 and 7308 I have. So if one is willing to spend $50, I would absolutely recommend a nice 7308. But if the Sylvania and Tung-Sol can be gotten for $25 to $30 each, then by all means, grab them. Cheers.

 

I have to agree that for $50 (or even more), all those Amperex or Philips 6922 and 7308 are a steal...To think I used to blow $20 on pairs of pentodes and oddball single triodes (was fun in its own right)...

post #4233 of 10501
Hey AFB

Tube filaments in series would probably not be a good idea in the LD and I would advise not to do so. Heaters do not work like a normal resistor would.

A little reading on series filaments...
www.emissionlabs.com/html/guarantee/HEATER-MODULES/index-heater.htm
beerchug.gif
post #4234 of 10501
Quote:
Originally Posted by TrollDragon View Post

Hey AFB

Tube filaments in series would probably not be a good idea in the LD and I would advise not to do so. Heaters do not work like a normal resistor would.

A little reading on series filaments...
www.emissionlabs.com/html/guarantee/HEATER-MODULES/index-heater.htm
beerchug.gif

 

Sorry if I confused you, I didn't mean actually changing the heater circuitry lol; I got my wording mixed up.

 

My question is just: should we expect a lower heater voltage when using two tubes instead of one (twice the heater current and load on the transformer)?

post #4235 of 10501
Quote:
Originally Posted by Audiofanboy View Post
 

 

Sorry if I confused you, I didn't mean actually changing the heater circuitry lol; I got my wording mixed up.

 

My question is just: should we expect a lower heater voltage when using two tubes instead of one (twice the heater current and load on the transformer)?

 

I wouldn't expect the voltage to drop with two tubes instead of one as the transformer is designed to run two tubes. Whether there is 300mA draw on one socket or a 600mA draw across two sockets, it should be within spec. Now a 600mA draw across one socket I can't say since it is yet to be determined how the windings are configured.

 

I don't have any Vector sockets so I can't measure the voltages, but that would be a good thing for someone with the Vector's to do. Measure the filament voltage of two tubes vs one and post it here. :smile:

post #4236 of 10501
Quote:
Originally Posted by Audiofanboy View Post

 

So, hypothetically, would adding another filament "in series" with the the first one (i.e., a second tube) yield a similar drop in filament voltage, like in the example where a 6SL7 was swapped for a 6SN7 and voltage dropped?

 

If so, I still think that just wastefully using two separate tubes may just better and prettier...

 

In an attempt to test whether running two separate tubes would affect the heater voltage, I made sure their was no tube in the 9-pin socket, and then plugged in two 7-pin tubes, 6HM5, and measured the heater voltage on the Vectors. Both of them read 6.7 volts. Therefore, running two tubes, versus one, makes no difference.

 

If you are thinking about actually rewiring the filament wiring inside the LD, well, that is a whole 'nother story....

post #4237 of 10501

If one has problems with little dot giving too much voltage to filaments, then i suggest you buy something like this.

700

8.4V 0.45A and no worries of over voltage. Just got this in my hands. :L3000:

post #4238 of 10501

Final comments on Tesla E88CC (gold pins & grids) v TFK ECC88.

 

Although it has been mentioned that the 6DJ8 family don't seem to need much burn-in, these Teslas have improved massively over time (in my system at least) - now 50+ hrs.. I never thought they would/could match the Telefunkens, let alone surpass them. The TFKs have slightly more bass slam, but get beaten in the detail/3D soundstage/clarity/overall 'magic' arenas. Revisiting every piece of music I have been using for comparison over the past months does nothing to bring any doubt into the picture - just more joy...oh happy days!

 

Despite fear of repeating myself to nauseating degree, I still believe that soldering the headphone cable direct to the board has proved to be one of the biggest improvements I have managed to achieve - and the cheapest!

post #4239 of 10501

Hi Artsi,

 

How does this tube sound compared to the octals?

post #4240 of 10501
Quote:
Originally Posted by mordy View Post
 

Hi Artsi,

 

How does this tube sound compared to the octals?

Heating time is noticeably longer with 8FQ7. About sound is difficult to say anything bad. After some usage this tube could even be one of my favorites. Local seller of this tube and philips 6922 & 6DJ8 said that GE 8FQ7 does have compressed sound. This was NOS and it really sounded first like it compressed everything to mp3. But even after hour or two of usage it is not sounding mp3 anymore. Sound is very pleasing and i'm going to listen this tube way longer. I haven't heard any bad sounding tubes for a long time. :L3000:

post #4241 of 10501

Running filaments below recommended rating will shorten the life of a tubes faster than overvoltage will from what I read, and 2V is quite the drop.

 

Another thing to remember with these big octals is even though a 6L6 has a running heater current of 900mA hot, it can draw up to 3A on a cold startup. So everytime you power up a tube that is close to maximum heater current, you are actually creating a severe load on the LD transformer for a short period of time...

 

Just something to think about...

:beerchug:

post #4242 of 10501

I have quite a few tube books, manuals etc in PDF format on Dropbox, if you want any of them just PM for the link.

 

The Super Sekret List - Enter if you dare... :D (Click to show)
American Substitutes for Foreign Types.doc
Amperex 1958.pdf
Amperite Ballasts.pdf
ARRL - Amatur Radio Handbok (1941).pdf
Basic Theory of Electron Tubes (Army 1952).pdf
Brimar Tubes 196x (partial).pdf
Burroghs Nixie Tube Catalog B_W.pdf
Federal Telephone and Radio Corporation - Handbook of Tube Operation (82nd Ed. 1944).pdf
Foreign Substitutes for American Types.doc
GE Essential Characteristics.pdf
GE Neon Lamps 1965.pdf
Kenyon Amateur 1937.pdf
Mcarthur - Electronics and Electron Tubes (1936).pdf
Moyer - Radio Recieving and Television Tubes (1936).pdf
Mullard Tubes 196x.pdf
Peters - Theory of Thermonic Vacuum Tube Circuits (1927).pdf
Philips 1943 GVDR.pdf
Philips Part 4 1972.pdf
Preisman - Graphical Constructions for Vacuum Tube Circuits (1943).pdf
Pullen - Conductance Curve Design Manual (1958).pdf
Radiotron Designers Handbook (1941).pdf
Radiotron Designers Handbook (1953).pdf
Raytheon Amateur 1938.pdf
Raytheon Tubes 196x.pdf
RCA 1940 Vacuum Tube Design.pdf
RCA 1962 Electron Tube Design.pdf
RCA Amateu 1934.pdf
RCA Electron Tubes (1935-1941) vol1.pdf
RCA Electron Tubes (1942-1948) vol2.pdf
RCA Industrial and Communications Types 1960.pdf
RCA Interchange 1960.pdf
RCA Phototubes 1941.pdf
RCA R-10 1933.pdf
RCA Radio Designers Handbook 4th Ed 1952.pdf
RCA RC-12 1934.pdf
RCA RC-13 1937.pdf
RCA RC-14 1940.pdf
RCA RC-15 1947.pdf
RCA RC-16 1950.pdf
RCA RC-17 1954.pdf
RCA RC-18 1956.pdf
RCA RC-19 1959.pdf
RCA RC-20 1960.pdf
RCA RC-21 1961.pdf
RCA RC-22 1963.pdf
RCA RC-23 1964.pdf
RCA RC-24 1965.pdf
RCA RC-25 1967.pdf
RCA RC-26 1968.pdf
RCA RC-30 1975.pdf
RCA RefBook 1956.pdf
RCA ST-59 Beam Power Tubes 1938.pdf
RCA TT-3 1938.pdf
RCA TT-4 1956.pdf
Reich - Theory and Applications of Electron Tubes (1944).pdf
Reich Principles of Electron Tubes (1941).pdf
Rider - Inside the Vacuum Tube (1945).pdf
Robin & Lipman 1947 Practical Amplifier Diagrams.pdf
Schure Vacuum Tube Rectifiers (1958).pdf
Secondary_Electron_Emission.pdf
Seely - Electron Tube Circuits (1950).pdf
Spangenberg- Vacuum Tubes (1948).pdf
STC 1947 Standard Valves.pdf
Sylvania 1951.pdf
Sylvania 1959.pdf
Taylor 1939.pdf
taylor tube catalog.pdf
taylor_transmitting 193xtubes.pdf
Telefunken 1930-31.pdf
The Thermonic Vacuum Tube and it's Applications (1920).pdf
Theory of Thermonic Vacuum Tubes (Chaffee 1933).pdf
Tomer 1960 Getting the Most Out of Vacuum Tubes.pdf
Tube Numbering Systems.doc
Vacuum Tube Oscilators (1953).pdf
Western Electric Tubes 1933.pdf
Western Electric Tubes 1956.pdf

:beerchug:

post #4243 of 10501
Quote:
Originally Posted by hypnos1 View Post
 

Final comments on Tesla E88CC (gold pins & grids) v TFK ECC88.

 

Although it has been mentioned that the 6DJ8 family don't seem to need much burn-in, these Teslas have improved massively over time (in my system at least) - now 50+ hrs.. I never thought they would/could match the Telefunkens, let alone surpass them. The TFKs have slightly more bass slam, but get beaten in the detail/3D soundstage/clarity/overall 'magic' arenas. Revisiting every piece of music I have been using for comparison over the past months does nothing to bring any doubt into the picture - just more joy...oh happy days!

 

I have three of these gold pin/grid Tesla E88CC, but I forgot to mark the one that has already been burned in for 20 hours!!  (>_<)  I guess I am going to have to start all over again! lol :)

 

And thank you so much for posting this! My wallet is feeling much better now that I am no longer feeling the urge to get a TFK ECC88!  :) 

post #4244 of 10501

I haven't read this thread for quite some time...could someone point me in the right direction? I'm looking for a suitable replacement for my Sylvania GB-408A tubes that I love, LOve, LOVED in my LD1+. I've pretty much worn them out though, time for new tubes. Actually, I fried my amp as well so time for a new amp too...lol

 

Anyways, looking for something that might be easier to come by that can compare to the Sylvania GB-408A's.

post #4245 of 10501

Would like to measure the voltages using the Vectors. My wall outlet voltage is 122V. Does this mean that the values will be skewed upwards?

 

If I were to measure the voltages of a dual triode octal tube, am I to measure only on one Vector adapter? Which pins to measure on the 12AX7 adapter that I use with an additional adapter for octal tubes?

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