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Little Dot Tube Amps: Vacuum Tube Rolling Guide - Page 189

post #2821 of 7553
Quote:
Originally Posted by KR500 View Post
 

I just got mine in the mail , 61...same year. They look nice

well protected in a hard cardboard tube wrapped in bubble wrap

Just have to find some thin copper wire to make a jumper. Just have never saved any bits of wire that fine in my parts bins

 

What i did is  remove strands from the wire to make it smaller

post #2822 of 7553
Quote:
Originally Posted by TrollDragon View Post
 

I'll have to inquire with the guru's over on DIY Audio and see if there is not some economical way to make a little box to go between the LD's pre-amp out's and a power amplifier, either with some blocking caps or a 1:1 transformer that does not cost $100 to implement. 

 

The quest is a foot for a solution!

 

for me i dont even know if the lepai ta2020 is dc coupled or not i dont know which is which

post #2823 of 7553
Quote:
Originally Posted by gibosi View Post
 

A pair of RCA 6HM5/6HA5/EC900 RF triodes arrived today.

 

 

After about 15 hours of burn-in, casually listening every so often, I think I can say that these are pretty good tubes. Unlike the 6AQ6/6AT6/6AV6, these do not have a treble-oriented analytic presentation, but instead, are more similar to pentodes. The highs are definitely there, clean and detailed, and musical. Moreover, the bass on these is quite good. 

 

I do not feel that these are at the same level as the TS 6485 or GE 6AV6. However, after only 15 hours and rather casual listening through old ears, this is more of a hunch than a critical evaluation, and I hope that others with betters ears and gear will check these out.

 

And I have one more pair of 6HM5 coming. A pair of GE 6HM5 "Made in Great Britain". From the pictures provided by the vendor, these are not short and squat like the RCA-Siemens, so likely different construction, and perhaps, a different sound.

post #2824 of 7553

I'm kind of short on cash was wondering if anyone was interested in Valvo E91H. Sylvania 5915 and Tung Sol 6AH6WA, I have one pair of each im trying to sell off, I live in Malaysia so if I could send them all to 1 person that would be great.

post #2825 of 7553
Quote:
Originally Posted by siles1991 View Post
 

im kind of stumped with this is the Lepai TA2020 a DC coupled amplifier I was planning to pre amp out into this amp but I can't tell whether it is or not?

It is most likely a AC coupled T amp and should be safe. There are other failures that can blow out speakers and a internal fault in the amp can still blow speakers. My LD VI+ is a direct coupled tube amp with DC servo control and so is my Schiit Lyr. A failure in the DC servo control could in theory blow out the headphones or speakers. I had a custom tube amp that was AC coupled (caps at the output) that took out a headphone when the tube arc over. DC coupled amps should have protection circuits in them for DC offset that can burn out speakers. There are pros and cons for direct coupled amps for both tube and Solid State. 

post #2826 of 7553

The USAF 6AH6 sound really nice . I'll play them in a bit and post thoughts on them next week .

CAT5E cable worked fine as a jumper . Used the orange and blue cable. Tubes are a bit tighter now

The RCA 6DT6 are being sent back to the dealer , hum city although a tiny bit quieter in EF92 mode .  After 6 different pairs of preamp tubes these are the only faulty ones so far . The others are all completely noise free.

I moved the Little Dot away from all electronic equipment with the RCA's just to make sure. but no change in the noise/hum .

post #2827 of 7553
Quote:
Originally Posted by KR500 View Post

The USAF 6AH6 sound really nice . I'll play them in a bit and post thoughts on them next week .
CAT5E cable worked fine as a jumper . Used the orange and blue cable. Tubes are a bit tighter now
Nice!
It will be 2 weeks till mine arrive. I need a local tube supplier, strike that no I don't. biggrin.gif
post #2828 of 7553
Quote:
Originally Posted by john57 View Post

It is most likely a AC coupled T amp and should be safe. There are other failures that can blow out speakers and a internal fault in the amp can still blow speakers. My LD VI+ is a direct coupled tube amp with DC servo control and so is my Schiit Lyr. A failure in the DC servo control could in theory blow out the headphones or speakers. I had a custom tube amp that was AC coupled (caps at the output) that took out a headphone when the tube arc over. DC coupled amps should have protection circuits in them for DC offset that can burn out speakers. There are pros and cons for direct coupled amps for both tube and Solid State. 
Many a failure can take things out quickly, but since the LD has no caps on the Pre-Amp Outs I still wouldn't take the chance of smoking someones $3K+ amp and speakers with a $300 inexpensive Chi-nee amp, whose manufacturer even states "You no hookup, no hookup" biggrin.gif

The Lepai 2020 is only $25 so I'd worry more about it taking out speakers, but that's another story...

I am still looking for a solution for the bretheren here.
post #2829 of 7553

So I made a little stand to take pictures of tubes with...

 

With the GE5654's

 

Then you plug it in and the Magic Happens! (Click to show)

 

 

 

The light does not shine too well through the 6H30Pi-EH's, so I used both lamps... :)

 

post #2830 of 7553

Hi TrollDragon,

 

Beautiful piece of work, but my tubes glow orange LOL...

 

On a more serious note, there was a post way back of a guy who made a similar piece of wood for tubes, but instead of drilling the holes for the pins he made a circular grove the same size as the pin circumference (actually two sizes, one for 7 pin and one for 9 pin tubes).

 

Then he put in fine sand in the grooves and twirled the tubes around. The picture he posted after this treatment showed sparkling clean pins. From what I have read a mechanical light scraping/cleaning gets you the best electrical metal to metal contact.

post #2831 of 7553
Quote:
Originally Posted by mordy View Post
 

Hi TrollDragon,

 

Beautiful piece of work, but my tubes glow orange LOL...

 

On a more serious note, there was a post way back of a guy who made a similar piece of wood for tubes, but instead of drilling the holes for the pins he made a circular grove the same size as the pin circumference (actually two sizes, one for 7 pin and one for 9 pin tubes).

 

Then he put in fine sand in the grooves and twirled the tubes around. The picture he posted after this treatment showed sparkling clean pins. From what I have read a mechanical light scraping/cleaning gets you the best electrical metal to metal contact.

Thanks mordy!

 

Just had high intensity white LED's in the parts bin... :)

 

That is a great idea for the pin cleaner, I have another piece of hardwood, and the wife has some very fine grit for her rock polishing....

Now to pick up the proper sized hole saws, 3/8" and 15/32" will do 7 and 9 pin respectively.

post #2832 of 7553

Hi TD,

 

Thanks to the search function on this forum I found the original post. You may find this post useful: Post #639 by GermanGuy on this page:

 

 

 

http://www.head-fi.org/t/632518/analog-paper-2-discussion-and-appreciation-thread/630#post_9573905

 

 

Good luck!


Edited by mordy - 9/7/13 at 9:49pm
post #2833 of 7553
Thanks mordy!
I'll check it out for sure.
=====
Update from that info...

Before


After


I used a 3/4" dowel with a 7/16" hole drilled 1/2" deep, filled with 80 Mesh Lapidary Grit.
Stuck the tube pins in and rotated the dowel back and for for 1 minute or so, I know now why GG used the little disk of foam on the bottom of the tube. It kept the sand in his holder which I didn't have that problem of the grit falling out, but the grit will grind down the edge of the glass as well... smily_headphones1.gif
I'll use a thin piece of foam next time I clean pins.

The Product & The Super Duper handmade Tooling.


I have 200 & 600 Grit as well but they are really fine, the 200 is a gritty powder and the 600 is like talcum powder, so I'll probably not use either of those.
I feel the 80 grit did a fine job cleaning the pins for a minute or two of easy turning.
Edited by TrollDragon - 9/8/13 at 11:40am
post #2834 of 7553

Just popped in my Mullard 10M Master series EBC91/6AV6 for the first time today, pretty impressive, lets see how time is to them.

 

They came in fancy foam boxes with gold pins, I also have a set of RCA and Sylvania JAN 6AV6 i'm going to try later this week.

 

I'm curious to how these compare to AFB Pinnacle 6AV6 as well if anyone has compared them.

post #2835 of 7553

Hi mab 1376,

 

Found these inexpensive 6AV6 tubes of Japanese origin. They are NOT identical to the Pinnacle tubes, but have very similar construction including the unusual side getter. Have not tried them, but may be interesting to people who like the 6AV6 tubes.

 

 

http://www.ebay.com/itm/2PCS-NEC-6AV6-Radio-Vacuum-tube-NOS-/151114821587?pt=Vintage_Electronics_R2&hash=item232f252fd3

 

 

Please note that the price is per pair.

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