[Paladin79]

I will extract all the "old" solder that's on there until I see inside of the pin right ? I can see that some pins even on some other tubes have a little hole opening on the tip the pins.
And then apply a new solder ?

You can, yes.

With solder removed, and after soldering. I usually keep the tube parallel with the work surface when doing the soldering. You can slide small diameter solder inside each pin before applying heat, if not capillary action will draw it in anyway but you may have a bit more cleanup. If you were in the US I would offer to fix them for you free as I have with many other folks on here.

Rosin core solder can often work if you do not find liquid rosin flux, since it is not easy to see what is truly happening inside each pin, I do not like to take chances and I do not want to have to do the process over again.

https://www.kester.com/Portals/0/Documents/Knowledge Base/Hand Soldering Short Course.pdf

There is plenty of info out there on soldering, Kester used to do a six week live soldering course, I was fortunate to go through that but then I have taught soldering and electronics.

 

[Deceneu808]

You can, yes.

With solder removed, and after soldering. I usually keep the tube parallel with the work surface when doing the soldering. You can slide small diameter solder inside each pin before applying heat, if not capillary action will draw it in anyway but you may have a bit more cleanup. If you were in the US I would offer to fix them for you free as I have with many other folks on here.

Looks so clean. Thank you for the offering but yeah unfortunately there is a slight 5,155 miles distance in a straight line
I'll need to improvise something to hold the tubes and last but not least I hope my small iron is up to the task of melting whatever is left on the pins.

Are the pins empty on the inside ? Should I also heat the enitre pin and not only the tip ? I'm still trying to figure out the details. How deep does the rabbit hole go inside the pin ?

 

[Paladin79]

Looks so clean. Thank you for the offering but yeah unfortunately there is a slight 5,155 miles distance in a straight line
I'll need to improvise something to hold the tubes and last but not least I hope my small iron is up to the task of melting whatever is left on the pins.

Are the pins empty on the inside ? Should I also heat the enitre pin and not only the tip ? I'm still trying to figure out the details. How deep does the rabbit hole go inside the pin ?

Generally factory solder is often just toward the pin end but I like to extend it further into the pin. If you get solder say 7 mm into the pin you are fine, just try not to angle the tube down so the solder flows all the way through. You can just heat the tip of the pin.

You do a makeshift vise using kitchen tongs.

https://www.amazon.com/dp/B07CSTLCS...&pd_rd_r=bffb05d4-8d2b-46e0-825d-a3ede6e626ea

Just wrap each end with silicone tape or even electrical tape, use a few rubber bands to give enough pressure to keep the jaws shut. Place the handles inside a couple bricks or blocks of wood and use whatever you have to apply pressure, a bungee cord does a great job.

Ok time for me to face the frozen tundra that is my home now but I should be around later.

 

[Deceneu808]

Generally factory solder is often just toward the pin end but I like to extend it further into the pin. If you get solder say 7 mm into the pin you are fine, just try not to angle the tube down so the solder flows all the way through. You can just heat the tip of the pin.

You do a makeshift vise using kitchen tongs.

https://www.amazon.com/dp/B07CSTLCS...&pd_rd_r=bffb05d4-8d2b-46e0-825d-a3ede6e626ea

Just wrap each end with silicone tape or even electrical tape, use a few rubber bands to give enough pressure to keep the jaws shut. Place the handles inside a couple bricks or blocks of wood and use whatever you have to apply pressure, a bungee cord does a great job.

Ok time for me to face the frozen tundra that is my home now but I should be around later.

Thanks for all the explanations. I'll grab all I need and see what I can pull off

 

[tubebuyer2020]

If you were in the US I would offer to fix them for you free as I have with many other folks on here.

A YouTube video demonstrating the process and as many cats as there are available would be great, but if video-blogging is not your thing that also is understandable .

 

[Paladin79]

A YouTube video demonstrating the process and as many cats as there are available would be great, but if video-blogging is not your thing that also is understandable .

I may work on that. Woodstock would require equal time though.

 

[adamus]

Speaking of future designs...



Cool idea! But are those Edcors gapped to take 80-100mA on the primary? Otherwise, would have to cap couple to them anyway, so not sure that would be an improvement, unless you had something else in mind?

This got the gears turning though, could be interesting to load the cathode follower with a low turns ratio output transformer, maybe 2:1 or 4:1 to lower the output impedance further, although they would be large to handle 100mA without saturating, also wouldn't be an OTL anymore I might explore this idea.

they arent gapped for any DC, so you would need to parafeed them. but.... that cap can be small and premium. You would be right to question the gains over the the current caps you have in... but could you impendance match for all headphones. Thats the biggey

 

[L0rdGwyn]

they arent gapped for any DC, so you would need to parafeed them. but.... that cap can be small and premium. You would be right to question the gains over the the current caps you have in... but could you impendance match for all headphones. Thats the biggey

Yes with multiple taps, it could be done, but a tight squeeze...I think I will leave it as is for now, but thank you for the idea. You have inspired me @adamus , I might experiment with OPT that are gapped for >100mA on the primary to load the cathode, something to think about in a future amplifier, likely with a different tube in the cathode follower position. I have seen this with some speaker amplifiers, but obeying Vhk of the cathode follower can become an issue at high voltage swings, not so much a problem for headphone amplifier.

 

[Paladin79]

Straight out of the box with some excellent tubes and headphones I am pretty shocked at the SQ, hum, blooming, volume pot tracking etc. I might keep the blue LED on the front.

Um I do like the shape of the transformer cover. Oh and I have never heard any difference in IEC sockets so that might stay. I tried Focal Utopias, a Tung Sol 6080, and a Tung Sol BGRP trying to be as fair as possible.

 

[bcowen]

Looks so clean. Thank you for the offering but yeah unfortunately there is a slight 5,155 miles distance in a straight line
I'll need to improvise something to hold the tubes and last but not least I hope my small iron is up to the task of melting whatever is left on the pins.

Are the pins empty on the inside ? Should I also heat the enitre pin and not only the tip ? I'm still trying to figure out the details. How deep does the rabbit hole go inside the pin ?

The wire from each element inside the tube comes all the way down to the tip of the pin. When the tube was made, those wires stuck out of the end of the pins a bit, and were then either trimmed flush with the pin's end and soldered, or soldered and then trimmed. So as @Paladin79 noted, you just need to get enough solder in there to be sure the wire is electrically and solidly mated to the pin. You need a soldering iron that is capable of at least 600 degrees at the tip, and preferably higher (like 750 - 800). You can do more damage with too little heat (and having to apply it for too long) than a higher heat that will get things to the right temperature for the solder to melt more quickly. Kind of like a dull knife being more dangerous than a sharp knife (only different).

 

[bcowen]

Straight out of the box with some excellent tubes and headphones I am pretty shocked at the SQ, hum, blooming, volume pot tracking etc. I might keep the blue LED on the front.

Um I do like the shape of the transformer cover. Oh and I have never heard any difference in IEC sockets so that might stay. I tried Focal Utopias, a Tung Sol 6080, and a Tung Sol BGRP trying to be as fair as possible.

Well, the biggest problem is pretty obvious. You have it on a cherry shelf, and we all know that maple sounds better.

 

[Paladin79]

Well, the biggest problem is pretty obvious. You have it on a cherry shelf, and we all know that maple sounds better.

Hmm you could be right, now if you tell me you loved it, out of the box, you might as well send the Incubus back since it is wasted on you.

 

[qingcai]

You can see the yellow/green earth cable sticking out just close to the blue disc capacitors - the yellow/green goes from the mains earth input straight to that point.
And that is the main earth point of this circuit, and everything is earthed to the earth pin on the mains socket.

Yes it is a bit of a mixed mess, but generally works, please note than only two cables goes to the phones socket, both channels are earthed thru the chassis, no separate earth lead.

It is a major engineering mistake to just dump the 50 Hz / 6,9 V heater straight at the left channel earth.
And then tell customers that it is a defective tube that causes the loud left channel hum at zero volume.
But still it is sold in huge numbers, and people accept it anyhow - there is a huge market for this type op OTL headphone amp, and a really silly mistake made by the Chinese engineers, this type of referencing the heaters to ground has been around since the 1950´s.

Just tested my circuit coupled to a Pioneer CD player, thru a Beyer-dynamic DT 990 Pro 250 Ohm phone, and it is dead quiet up to say 3 a clock PM on the volume control.
And the phones are quite loud at 9 a clock AM, and whats more, dead quiet at zero volume, when this thing just buzzed loudly in the left channel before I modded it.

Please, I thought I checked the volume control for any anomalies, but could find none - I read your post, but I could not find any error in the volume control circuit - all connections are there, I think, and everything checks out?

still not see clearly about how virtual zero connected. should be looks like this ?

 

[Paladin79]

Providing more cabinet room can look like this:

Two inch and three inch additions, naturally the bottom plates would be removed and additional ventilation would be provided. I believe @bcowen is looking for the three inch extension in tiger maple with mitered corners and at least one spline per corner. My cabinet will look nothing like this, most likely only the top plate will be visible.

 

[Ripper2860]

I believe @bcowen is looking for the three inch extension in tiger maple with mitered corners and at least one spline per corner.

He is soooooo high maintenance!