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Little Dot Tube Amps: Vacuum Tube Rolling Guide - Page 251

post #3751 of 8026
Quote:
Originally Posted by mordy View Post
 

Below are pictures of my low cost hillbilly 12A7 adapter.

 

Please: Don't laugh - this is very serious business for me and allows me to stay in the race for the best tube. BTW, as long as I don't touch anything there is no hum (unless I turn up the volume to deafening levels).

 

I'm not sure my setup with wires flying everywhere looks any better! lol :)

 

And I think it is great that you posted your pictures. I suspect that all of us have lots of electrical stuff stashed away, and if we take the time to rummage through it, we can often find bits and pieces that we can re-purpose to new uses. Your pictures might help others to think about how they might be able to cobble something together to explore these double triodes. Cheers!

post #3752 of 8026
Quote:
Originally Posted by mordy View Post
 

Hi Mikelap,

 

I assume that you are referring to the screw holding the socket. The socket itself came with a mounting ring with facilities for two screws to hold the socket in place. If it was designed for this, why do you feel that this setup is a fire hazard?

 

Its not what i ment mordy  what i ment is maybe somebody else in the household taught it was a fire hasard .Thats what my wife would say to me I was  just kidding mordy sorry 

post #3753 of 8026

Hi Gibosi,

 

Thanks for your encouraging words.

post #3754 of 8026

How tough are these tubes, having a close look at mine they seem quite delicate -  images of shards of glass embedded in my fingers filled my head on first closer inspection. One of mine was a bit wonky so I gave it a little push and it moved, have to look at the manual to see how to remove them but quite happy with them as they are at the moment.

post #3755 of 8026
Quote:
Originally Posted by stvn758 View Post
 

How tough are these tubes, having a close look at mine they seem quite delicate -  images of shards of glass embedded in my fingers filled my head on first closer inspection. One of mine was a bit wonky so I gave it a little push and it moved, have to look at the manual to see how to remove them but quite happy with them as they are at the moment.

 

More context please? What tubes are you talking about?

 

But generally speaking, unless you drop them on concrete, tubes are pretty durable. 

post #3756 of 8026
Quote:
Originally Posted by gibosi View Post
 

 

More context please? What tubes are you talking about?

 

But generally speaking, unless you drop them on concrete, tubes are pretty durable.

I have a Little Dot MKIII, the power tubes looked fragile, not much to grab onto with the two front ones either. I assume they don't require much force to come out?


Edited by stvn758 - 10/31/13 at 1:53pm
post #3757 of 8026
Quote:
Originally Posted by stvn758 View Post
 

I have a Little Dot MKIII, the power tubes looked fragile, not much to grab onto with the two front ones either. I assume they don't require much force to come out?

 

You may have heard the term "rolling tubes"? So grab the tube and gently "roll" it so that the top makes a small circle. This will help to loosen it, and then pull it straight up and out. Easy. :)

post #3758 of 8026
Quote:
Originally Posted by gibosi View Post
 

 

You may have heard the term "rolling tubes"? So grab the tube and gently "roll" it so that the top makes a small circle. This will help to loosen it, and then pull it straight up and out. Easy. :)

Thanks.

post #3759 of 8026

Hi,

 

Entered the 6DJ8 world going window shopping. First impression is the enormous selection available with hundreds and hundreds of items for sale.

 

Seems that Amperex is the way to go. Does anybody have any feedback on Japanese manufactured 6DJ8 tubes?

 

I am getting my receiver back soon. Seems that the blow out of the left channel had nothing to do with the Little Dot. It could be that I moved one speaker and a wire came lose and shorted out the amp.

 

Speaking of dual triodes I have four 12A7 variants, all Sylvania with red designations printed on the box flaps which indicates replacement tubes. It is possible that these red marked boxes were not the highest quality production items.

 

Only tried two types so far. One is a 12AX7A that sounds absolutely great. Tried a 12AU7A today but could not stand it - thin and shrill sounding. Go figure?

 

A couple of the soldered wires came off the Vectors. I am exhausted after going to soldering school and wondering what happens to the melted solder that drips down into the adapter..

 

Anyhow, everything works and sounds fine now.

post #3760 of 8026
Quote:
Originally Posted by mordy View Post
 

Speaking of dual triodes I have four 12A7 variants, all Sylvania with red designations printed on the box flaps which indicates replacement tubes. It is possible that these red marked boxes were not the highest quality production items.

 

Only tried two types so far. One is a 12AX7A that sounds absolutely great. Tried a 12AU7A today but could not stand it - thin and shrill sounding. Go figure?

 

With regard to 12AX7, I have followed Joe's advice and ordered a few 5751s. 

 

http://www.audioasylum.com/scripts/d.pl?audio/faq/joes-tubes.html#12AX7-3

 

I was able to pick up a Tung-Sol, GE black plate, and a Sylvania JAN black plate, and hope to get to them eventually. However, I will admit that I will be approaching them with a fair amount of prejudice, as I seriously doubt that they can compete with the 6DJ8s that I have become accustomed to.....

post #3761 of 8026
Quote:
Originally Posted by mordy View Post
 

 

For those that don't know I'd like to issue a safety warning on open connections like this, I am NOT picking on you personally mordy, it is just your setup here is a great example. 

 

On the unmodified Vector extenders there can be upwards of 155 Volts exposed on terminals 5 & 6 and if you have the LD in EF92 mode on terminal 7 as well. (Obviously the same applies to the terminals on the bare B9A socket since that is where the wires terminate.)

 

If you are going to work with this kind of setup then do your work with the power off and don't forget that the capacitors in the LD will take a few minutes to discharge.

There is still dangerous levels with the power switch turned off and the mains cord unplugged if the amp has been on for a few minutes or more.

 

Try it for your self, while listening to some music, shut the amp off and pull the AC cord out if you wish just to see how long it takes for the music to fade out. These are the 250Volt capacitors in the amp discharging that is keeping the music playing and the voltage on the above terminals will still be present. I believe the music stops because the tube cooled with no heater voltage before the capacitors discharged all their reserve.

 

So if you have to touch or adjust anything with the power on then only work with one hand. Keep the other hand behind your back or in your pocket.

 

I you had a hold of the amp chassis and managed to touch terminal 5, 6 or 7 depending on the mode, it would be similar to grabbing the 110V Mains with a wire in each hand.

 

The LD transformer is rated for 100mA on the B+ line and referencing Charles Dalziel's chart, you are past the point where you can voluntarily let go.

 

So seriously take heed of this warning with these open point to point connections. 

I really don't want to see anyone get hurt and If this warning makes just one person who is unaware of the possible dangers take some precautions, then that is good.

post #3762 of 8026

I have some battle going on with two tubes.

700

 

700

Westinghouse 6DJ8 -63 made in USA and RCA 12AZ7A made in usa. Ring getters and RCA with black plates.

These two delivers something like honey to my ears. Real jaw droppers to me. Westinghouse is microphonic, but only if i knock the amp.

 

Comparing these to still very good 6N2P-EV it's easy to find bad things from it. 6N2P bass is boomier and lacks some control. Otherwise sound with these two is more clarity and clear brightness.

 

NUFF SAID.

 

Could be little rare ones, found only 1 of each identical to these from ebay.

http://www.ebay.co.uk/itm/Westinghouse-6DJ8-ECC88-Rohre-Lampe-Valvola-Valvula-/160891339939

http://www.ebay.co.uk/itm/Radio-Tubes-12AZ7A-12AZ7-RCA-Black-Plate-Orange-NOS-/290897243868

 

Btw amperex 6DJ8 -74 Holland with A-getter structure sound only mediocre to good.


Edited by Artsi - 10/31/13 at 11:36pm
post #3763 of 8026

i fell for tube mania and ordered the first Voskhod 6ZH1P-EV i saw on Ebay. Then while completing my mammut task of reading this entire thread i stumbled upon the same valves nearly half the price(they were just named differently i think without the Z and a J). damn how could i have not seen? guess the seller had a nice day as i paid him:)

Oh btw i ordered some

JHY-6AK5

from ebay.They are from 1945.They are also unmatched but same production year and month so i hope nothing goes wrong in my amp. So i was wondering about jumper setting?any help pls?


Edited by superdux - 11/1/13 at 7:36am
post #3764 of 8026
Quote:
Originally Posted by TrollDragon View Post
 

 

For those that don't know I'd like to issue a safety warning on open connections like this, I am NOT picking on you personally mordy, it is just your setup here is a great example. 

 

On the unmodified Vector extenders there can be upwards of 155 Volts exposed on terminals 5 & 6 and if you have the LD in EF92 mode on terminal 7 as well. (Obviously the same applies to the terminals on the bare B9A socket since that is where the wires terminate.)

 

If you are going to work with this kind of setup then do your work with the power off and don't forget that the capacitors in the LD will take a few minutes to discharge.

There is still dangerous levels with the power switch turned off and the mains cord unplugged if the amp has been on for a few minutes or more.

 

Try it for your self, while listening to some music, shut the amp off and pull the AC cord out if you wish just to see how long it takes for the music to fade out. These are the 250Volt capacitors in the amp discharging that is keeping the music playing and the voltage on the above terminals will still be present. I believe the music stops because the tube cooled with no heater voltage before the capacitors discharged all their reserve.

 

So if you have to touch or adjust anything with the power on then only work with one hand. Keep the other hand behind your back or in your pocket.

 

I you had a hold of the amp chassis and managed to touch terminal 5, 6 or 7 depending on the mode, it would be similar to grabbing the 110V Mains with a wire in each hand.

 

The LD transformer is rated for 100mA on the B+ line and referencing Charles Dalziel's chart, you are past the point where you can voluntarily let go.

 

So seriously take heed of this warning with these open point to point connections. 

I really don't want to see anyone get hurt and If this warning makes just one person who is unaware of the possible dangers take some precautions, then that is good.

+1

post #3765 of 8026

I have been burning in a Voskhod 6N23P, 1978, with silver shields, and after about 20 hours I am very impressed, great bass, transparency, 3-D stage and liquidity. This reviewer ranks it among the best of the Voshkods:

 

http://www.head-fi.org/t/549508/schiit-lyr-the-tube-rolling-thread/8595#post_9625620

 

Highly recommended! :)

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