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Little Dot Tube Amps: Vacuum Tube Rolling Guide - Page 412

post #6166 of 7324
Quote:
Originally Posted by TrollDragon View Post


Then there is something not quite correct in either how you wired it or if it is an old pot salvaged from an old radio they had changed the A / B designation quite a few years ago.

The best way to tell if it is a linear pot is to unsolder it completely. Measure both outside lugs, this should give you roughly 10K ohms. Then turn the shaft approximately half way and you should measure 5K ohms between the center and each of the outside lugs. If the measurement is drastically different between the center and each outside lug, you have a logarithmic pot that will not work.

Also check the pinout of the trimpot you removed by looking it up on the net and make sure you have the wires to the big pot in the same configuration. Only if the big pot is confirmed to be linear from the first test.

Hi TD,

      I measured the pot from lug 1 to lug 3 = 9.56K then lug 1 to lug 2=4.11K then lug 2 to lug 3=5.42K.I double checked my connections they look ok pin1 to pin1 pin2 to pin2 pin3 to pin3=by turning the shaft clockwise the reading goes up and if i connect it reverse pin1 to pin3 pin2 to pin2 pin3 to pin1= by turning the shaft counter clockwise the reading goes up.The POTS are brand new from Chinada.THANKS!


Edited by i luvmusic 2 - 5/19/14 at 5:14am
post #6167 of 7324
Well everything sounds correct, don't forget the trimmer pot on the board only goes up a few hundred ohms with each turn of the little screw.

Try turning the big pot very slowly and gradually to see what happens.
post #6168 of 7324

Finally got the Sylvania sub-miniature 7963 installed into a 6SN7 base. I don't know why I thought this was a good idea! It was a PITA! So you might want to consider this a short essay in how NOT to build an adapter for these little tubes. lol :)

 

Since the pins in a 6SN7 base are hollow, I guess I thought it would be easy to simply insert the long sub-miniature leads and solder. But since the 6SN7 pins are recessed about an inch into the bottom of the base, it was very difficult to manipulate the leads in such a tight space. I ended up using some thick bare copper wire salvaged out of an old 12 gauge cable of the kind used to wire American buildings. I cut the wire into 1.75 inch sections and soldered them to the ends of the thin wire leads. Next, I wrapped the exposed leads with white electrical tape and labeled each - H, 1K, 2K, and so forth, and then inserted the thick copper wires directly into the hollow pins. A very snug fit, no solder required.

 

And there you have it: Another ugly masterpiece from yours truly :)

 

 

Listened to Diana Krall - Live in Paris last night. This tube has exceptional transparency, clarity and detail, with a black, black background. Imaging is precise and the stage is wide and deep. Like the Sylvania 6SN7W, vocals are sweet with a touch of warmth, very natural. Highs are extended and airy and the bass is deep, detailed and propulsive. This is right up there with the C3g. Another "endgame" tube to my mind.

post #6169 of 7324
Quote:
Originally Posted by TrollDragon View Post

Well everything sounds correct, don't forget the trimmer pot on the board only goes up a few hundred ohms with each turn of the little screw.

Try turning the big pot very slowly and gradually to see what happens.

Yeah that's what i've been doing turning the shaft very slow one thing i noticed if the input is 12V the pot looks like it's sensitive and if the input is 24V not as sensitive compared to 12V inputs.Again THANK YOU for  your HELP!:beerchug:

post #6170 of 7324

So those miniature tubes are that good i can't wait for mine your adapter looks fine to me whatever works is all good.

post #6171 of 7324

Hi Gibosi,

 

Welcome to sub miniature land! I do not have the C3g tubes  but I was very impressed that you found your Sylvania 7963 comparable to the C3g.

 

Now, I do not have the 7963 either, and it's $20 price and up precludes me from getting it due to my self imposed $8 limit per tube. However, I do have the mighty Raytheon 6832. Instead of using my clumsy set up of two Vectors I realized that I can use the tube mounted in the 9 pin extender on my 6DJ8 breadboard. IMHO it is easier to use it in this way with solderless connections, utilizing insulated 18 gauge solid copper wire as push in pins. Based on our collective experience with jumpers on various tubes I do know that the connections made this way are solid and perhaps superior to soldered connections. Just think of all the tubes that are pushed into tube sockets! Here are pictures:

 

 

I gave up on using the 6832 tubes as power tubes although it was quite possible, but I was lacking the slam in the bass. Now I am running my trusty RCA 6SN7GTB top heater wire tubes as power tubes, and the Raytheon JAN 6832 as driver.

 

The sound is excellent with all the accolades you can heap upon it. I am going to paint the leads with nail polish to insulate them, but one grand daughter gave me a bottle of pearlized nail polish and I am afraid that there is metal in it which would defeat it's purpose. Holding out for a different nail polish from another kid.

 

It would be nice if somebody could compare the 6832 to the 7963. My guess is that they are going to sound similar. If that is true I will easily resist the itch to buy the C3g with all the adapters. (I did see a pair of Lorenz C3g on German Ebay that went for 2.5 Euros + shipping, but I think a lot of German sellers don't ship outside of Europe.)

 

Cheers,

post #6172 of 7324
Quote:
Originally Posted by kvtaco17 View Post
 

 

I shall tempt you no more...

 

 

 

 

 

 

 

...unless shots of tubes in the dark are tempting...

 

Sorry old fruit....already have a gorgeous glow....:

 

 

And not only that, but at the risk of repeating myself, I can say that without doubt these 6AS7Gs are giving me a taste of hi-end at a lo-to-mid-end price. NOTHING could have prepared me for the difference they are making. Now my new adapter is well run-in, along with all the other goodies I have described (many times!) the depth of bass (as blew me away on revisiting Dire Straits' track 'Love over Gold') is now as never before...together with its wonderful detail...sheer bliss!

Can't wait to see what happens when silver wire adapter #2 gets finished, lol!

post #6173 of 7324

Hi guys,

 

So now I have obtained the Mullard 8100 and Voskhod, I was just wondering if upgrading my power tubes from stock to ELECTRO HARMONIX 6H30Pi would have any further improvement?

 

I would really appreciate some subjective and fair comments, as these are costing between 50-60GBP online at the moment.. If they dont make a noticeable difference then I will not rush into buying them.

 

 

Thanks in advance! 

 

ps cant make my mind up whether I should use the Mullards or Voskhods as my default tubes... both are good :x

post #6174 of 7324

Hi guys anyone of you familiar with these brand of 6AS7 made by GTC on the base it mark GTC 6AS7G Made in USA.Thanks!

CREATOR: gd-jpeg v1.0 (using IJG JPEG v62), quality = 90

 

CREATOR: gd-jpeg v1.0 (using IJG JPEG v62), quality = 90


Edited by i luvmusic 2 - 5/20/14 at 3:35pm
post #6175 of 7324
Quote:
Originally Posted by i luvmusic 2 View Post
 

Hi guys anyone of you familiar with these brand of 6AS7 made by GTC on the base it mark GTC 6AS7G Made in USA.Thanks!

 

I have no idea what GTC means.... I suggest you might have a better chance to get an informed answer if you post in the 6AS7G tube rollers thread. And it would very helpful if you posted a picture so people can see this tube.

 

http://www.head-fi.org/t/410326/for-6as7g-tube-rollers-here

post #6176 of 7324
Quote:
Originally Posted by gibosi View Post
 

 

I have no idea what GTC means.... I suggest you might have a better chance to get an informed answer if you post in the 6AS7G tube rollers thread. And it would very helpful if you posted a picture so people can see this tube.

 

http://www.head-fi.org/t/410326/for-6as7g-tube-rollers-here

Thanks G! i did not think about the pictures and the 6AS7 thread.

post #6177 of 7324
Quote:
Originally Posted by philiptw View Post
 

So now I have obtained the Mullard 8100 and Voskhod, I was just wondering if upgrading my power tubes from stock to ELECTRO HARMONIX 6H30Pi would have any further improvement?

 

I would really appreciate some subjective and fair comments, as these are costing between 50-60GBP online at the moment.. If they dont make a noticeable difference then I will not rush into buying them.

 

My amp is a hybrid, so I have no experience with power tubes. However, buried in the last 400 pages are a number of discussions. I suggest you click on the "Search This Thread" at the top (or bottom) of this page and search for "6H30P". Good luck.

post #6178 of 7324

I'm wondering if those tubes are made by RCA.

post #6179 of 7324

I think those are Russian tubes they look exactly like my russian tubes but i could be wrong.

post #6180 of 7324
Quote:
Originally Posted by i luvmusic 2 View Post

I'm wondering if those tubes are made by RCA.
I would hazard a guess those were made for the General Transformer Corp.'s PeeWee 25W transmitter from the 30's.

Sold by Rat Shack.
http://www.radioshackcatalogs.com/html/1939/h037.html
Center of the page.
Edited by TrollDragon - 5/20/14 at 4:08pm
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