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Little Dot Tube Amps: Vacuum Tube Rolling Guide - Page 62

post #916 of 7658

A few pics of the 6AH6 tubes as promised. First, the Raytheon JAN 6AH6WA packed and made in 1973, which I now know is probably later than I should have bought. These are very well built and look great up close.

 

 

And while I am it, here's a bit of a review of these after a day. They are balanced and detailed with a nice deep soundstage and slightly loose and grainy bass that goes pretty low, but are ultimately too veiled and not transparent enough after 10h of burn-in to warrant more listening. They aren't unpleasant and are quite tame in the highs -for those of you that like rolled-off treble- but they just don't make the cut compared to the kind of sound I've been hearing for the last couple of weeks. A B+ grade tube, which is actually pretty good for $3 NIB tubes with mil specs. Btw, for a 450 mA heater current, these really let the amp run pretty cool, a far cry from the EF91. Apparently, the gain of driver tubes (and the relative volume they produce) seem to be more correlated to amplifier heat dissipation than any other tube spec; which makes sense, more voltage going through everything, more loss do to heat.

 

Second, some Sylvania JAN 6AH6WA packed in 1970 and possibly made that year or the year before -getting closer to the 60s which is good for US tubes. These are extremely well built -best of the 3 6AH6 tubes I got- and the inner construction reeks of quality; I noted and you can see on the pic that the grids inside seem to be "gold colored", not necessarily gold but not that basic steel-grey color like on the Raytheons and others. At any rate, these were left to burn-in for the day and this time, first impressions are excellent, I can't imagine this tube getting less than an A grade really; highs are very detailed out of the box and have a really nice flavor to them, more later.

 

 

Third and last, GE JAN 6485 packed and made in 1978. I probably should not have bought those... Made too late in time, basic "6AH6" etched in glass, poor construction -tubes aren't perfectly straight just like cheap late 6AK5- and innards are lackluster -the anode on 6AH6 tubes is two separate pieces like on most recently tested tubes, the Raytheons and Sylvanias have both anode parts made and attached from a single sheet, the GE does not, it's just two anodes linked by a silly copper wire, disappointing, 70s/80s GE = poor quality- and the tubes just don't have that "shine" about them that the best JAN tubes have. Anyway, I'll try them as they're still special quality tubes, but I'm not hoping for much...

 

 

And bonus tubes, just for kicks, some Sylvania JAN 6AG5WA 6186 made and packed in 1967. These actually look great too, making me think I should buy more Sylvanias and less GE. Very nice construction with nice insides, these actually have both 6186 -special quality- and 6AG5WA etched on the glass, so I can't really imagine what I could have picked better in the 6AG5 family really. If these don't sound OK, then I'm done with that tube type anyway...

 

post #917 of 7658

A pair of GE 6485/6AH6s arrived in this mornings' mail.

 

 

I believe these are 1960's vintage, but am not positive. I cannot find anything on the web about this "NV" code. However my GE 8524A/6AU6s had a "NW" code plus the date 67-32, so I am guessing these are 1960's vintage as well....  Also of interest, the cage structure on these is quite different than the Tung Sols I received yesterday. I hope to get to these over the weekend.

 

And I am currently listening to a pair of 6HS6s.

 

 

These are purported to be a souped up 450 mA version of the 6AU6 (9500 gm and 50 mu), but unfortunately, they are rare and expensive. The cheapest price I am seeing on eBay for a pair is in excess of $80.00! Mine are used, as I pulled them out of some old McIntosh equipment. The tubes are dated 1970. As you can see, all the printing has worn off, but the shape of the shield suggests that they might be RCAs. Most unfortunately, one of these tubes has a significant ground hum... :( I am currently cooking them in the LD with the hope that the hum will dissipate. However, as these are not NOS, but used, I have no idea if they might improve. Nonetheless, these sound very good to my amateur ears. If you can find a pair cheap, I believe these are well worth checking out.

post #918 of 7658
Quote:
Originally Posted by gibosi View Post

A pair of GE 6485/6AH6s arrived in this mornings' mail.

 

 

I believe these are 1960's vintage, but am not positive. I cannot find anything on the web about this "NV" code. However my GE 8524A/6AU6s had a "NW" code plus the date 67-32, so I am guessing these are 1960's vintage as well....  Also of interest, the cage structure on these is quite different than the Tung Sols I received yesterday. I hope to get to these over the weekend.

 

And I am currently listening to a pair of 6HS6s.

 

 

These are purported to be a souped up 450 mA version of the 6AU6 (9500 gm and 50 mu), but unfortunately, they are rare and expensive. The cheapest price I am seeing on eBay for a pair is in excess of $80.00! Mine are used, as I pulled them out of some old McIntosh equipment. The tubes are dated 1970. As you can see, all the printing has worn off, but the shape of the shield suggests that they might be RCAs. Most unfortunately, one of these tubes has a significant ground hum... :( I am currently cooking them in the LD with the hope that the hum will dissipate. However, as these are not NOS, but used, I have no idea if they might improve. Nonetheless, these sound very good to my amateur ears. If you can find a pair cheap, I believe these are well worth checking out.


Nice tubes! I'm really curious about how the 6HS6 will sound if they (it) stops humming. One question though, what do the anodes look like on your GE 6485? Do they look like two plates, one on each side, just linked by a copper wire on one side, or linked by two solid metal bands? I think I see a cheap looking wire soldered on one of the anodes on the right tubes just like on mine, but I'm not quite sure...

post #919 of 7658
Quote:
Originally Posted by Audiofanboy View Post

One question though, what do the anodes look like on your GE 6485? Do they look like two plates, one on each side, just linked by a copper wire on one side, or linked by two solid metal bands? I think I see a cheap looking wire soldered on one of the anodes on the right tubes just like on mine, but I'm not quite sure...

 

Yeah, you are right! Just a cheap looking copper wire! So much for the 6485s being "premium" tubes! LOL 

post #920 of 7658
Quote:
Originally Posted by Audiofanboy View Post

Nice tubes! I'm really curious about how the 6HS6 will sound if they (it) stops humming.

 

Unfortunately, even after some 15 hours of cooking, the ground hum is still there... :( Nonetheless, these are very good sounding tubes. As one might expect they sound like the 6AU6. I really cannot hear any difference between these and my 8425As,.. Except for the ground hum!

 

It occurs to me that perhaps if I had some carefully selected tracks chosen to reveal subtle audio differences, perhaps one track for sub bass, one for highs, one for sound stage and imaging, and so forth, this might help me distinguish between tubes that are both very good and very similar.

 

Any suggestions or advice? Anyone? When introducing a new tube, headphones, or other piece of equipment into your system, what routines or methodologies do you use to help you to hear and understand the differences?

post #921 of 7658

 

Finally received today my TESLA 6F32V after a months wait (mother russia is far away)  right off the bat i like them i like the bassy sound and a decent soundstage top end just perfect for me so that probably means cleaner sounding  for younger ears but sounds good .I  i like them more than the 6aj5 and the 6ak5w/6096 right out of the box thats paired with 6h30pi gold pins power tubes

post #922 of 7658
Quote:
Originally Posted by MIKELAP View Post

 

Finally received today my TESLA 6F32V after a months wait (mother russia is far away)  right off the bat i like them i like the bassy sound and a decent soundstage top end just perfect for me so that probably means cleaner sounding  for younger ears but sounds good .I  i like them more than the 6aj5 and the 6ak5w/6096 right out of the box thats paired with 6h30pi gold pins power tubes

 

Glad to hear that they are everything you hoped for, especially given how long you had to wait! I notice that yours look somewhat different than the ones that mojorisin35 and I have. The build quality of yours clearly looks quite a bit better.... I wonder how they compare in sound?

 

 

 

Unfortunately, one of mine is very microphonic to the point that it is not usable. That said, I felt that these sounded very similar to the Russian Voshkods. And given the fact that the Tesla facilities were located in Czechoslovakia, I wonder if there might have been a degree of technology transfer between Tesla and the Russians...

post #923 of 7658
Quote:
Originally Posted by gibosi View Post

 

Glad to hear that they are everything you hoped for, especially given how long you had to wait! I notice that yours look somewhat different than the ones that mojorisin35 and I have. The build quality of yours clearly looks quite a bit better.... I wonder how they compare in sound?

 

 

 

Unfortunately, one of mine is very microphonic to the point that it is not usable. That said, I felt that these sounded very similar to the Russian Voshkods. And given the fact that the Tesla facilities were located in Czechoslovakia, I wonder if there might have been a degree of technology transfer between Tesla and the Russians...

ive been playing them for a couple of hours and the bass kind of mellowed out a bit but they are  cleaner sounding now you talked about the voshkod well its true they sound similar but upper end of the Tesla not harsh yet anyways i dont really like the vohkods that much the highs are a bit harsh if i remember correctly does that make any sense . And i want to add that they look like they where made yesterday dont know when they were made dough.


Edited by MIKELAP - 3/22/13 at 2:35pm
post #924 of 7658

I recently sold my LD MKiii, so I have a few sets of tubes with low hours on them. Sylvania, Voskhod, Tung Sol, and Electro Harmanix power tubes. PM me if you want more details.

post #925 of 7658

Six 6J4Ps (Russian equivalent of the 6AU6/EF94) arrived in today's mail:

 

 

These are rather nice looking tubes, manufactured in in November, 1975. However, all six are pretty noisy so I can't say how they sound. Two of them are burning in at the present time, and I really hope they will quiet down.

post #926 of 7658
Quote:
Originally Posted by MIKELAP View Post

 

Finally received today my TESLA 6F32V after a months wait (mother russia is far away)  right off the bat i like them i like the bassy sound and a decent soundstage top end just perfect for me so that probably means cleaner sounding  for younger ears but sounds good .I  i like them more than the 6aj5 and the 6ak5w/6096 right out of the box thats paired with 6h30pi gold pins power tubes

Well first pair ran for about 8 hours they opened up beautifully  balanced sound burning in 2nd pair of the bat they are  like the other ones at first bassy closed in a bit. tried to find what year they were made in data sheet from tesla says the 60's if you guys have any infos about year of manufacture i would appreciated it. Thanks.

 

 

post #927 of 7658

And these pretty little things came the other day, a pair of Philips MiniWatt 408As:

 

 

However, I believe that the only Little Dot that can use these is the 1+. As I understand, 408As are simply 6AK5s with 20V heaters. Lots of gold and silver in these. And I keep thinking that these just might make some mighty nice earrings, don't you agree? LOL

 

I need to open up the amp to change a set of jumpers before I can check them out, but with all the other interesting tubes I've been getting recently, just haven't gotten around to it yet...


Edited by gibosi - 3/23/13 at 12:16pm
post #928 of 7658
Quote:
Originally Posted by gibosi View Post

Six 6J4Ps (Russian equivalent of the 6AU6/EF94) arrived in today's mail:

 

 

These are rather nice looking tubes, manufactured in in November, 1975. However, all six are pretty noisy so I can't say how they sound. Two of them are burning in at the present time, and I really hope they will quiet down.

 

After 10 hours of burn, these tubes haven't improved. Moreover, considering that all six were noisy to begin with, I have decided that they aren't worth any more of my time, at least for now. And I would suggest that if anyone else is thinking about these tubes, my experience might be instructive. I should note that the vendor clearly states that these tubes are NOS but not tested. That said, I wonder if the standard "tube testers" most vendors use would even detect this noise?

 

Oh, on the chance any of you noticed, these tubes really are taller than the the standard American made 6AU6s. I am disappointed... but all six cost me $10, so it doesn't hurt too bad. LOL. Anyway, I still have a few more interesting tubes on the way, so for now, will now go back to my trusted 8425As and enjoy some good music. :)

 

PS: Has anyone else noticed that if you click on pictures included in quotes, you get a little + and if you then click on that, you get a zoomed in view?

post #929 of 7658

Hi Mikelap,

 

Here is a code chart for Tesla tubes in the Czechoslovakian language.  

From Google translate: 

MARKING DEVICES TESLA - CODE PRODUCTION DATA. TABLE OF DATA FROM 1947 TO THE END OF 1984
Sort by year and month of manufacture ascending page 1
  
code code Month Year Month Year Month Year code code code Month Year Month Year

 

Here is the link to the code chart - hope it helps.

 

http://web.archive.org/web/20070824161210/http://www.radiojournal.cz/tab4.htm

post #930 of 7658
Quote:
Originally Posted by mordy View Post

Hi Mikelap,

 

Here is a code chart for Tesla tubes in the Czechoslovakian language.  

From Google translate: 

MARKING DEVICES TESLA - CODE PRODUCTION DATA. TABLE OF DATA FROM 1947 TO THE END OF 1984
Sort by year and month of manufacture ascending page 1
  
code code Month Year Month Year Month Year code code code Month Year Month Year

 

Here is the link to the code chart - hope it helps.

 

http://web.archive.org/web/20070824161210/http://www.radiojournal.cz/tab4.htm

 

This is great! What a sleuth you are! :)  

 

So it seems my tubes, TG = Oct 1957. And Mikelap's tubes, AN = May 1963. Only 6 years difference, but in that time they radically changed the internal construction.

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